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Surgical Infectious Disease. Extra Credit Questions

admin — Tue, 07 Jul 2009 07:37:23 +0000

EXTRA-CREDIT QUESTIONS

25. Should all patients undergoing elective laparotomy receive prophylactic antibiotic coverage?

Show answer
No. Doing so would contribute to driving up the cost of antibiotics and their complication rate and devaluing formerly good drugs by rendering them useless against common flora against which they were once highly potent. Operating room nurses have always classified the kind of operation by its status with respect to microbial exposure: clean, contaminated, or septic. These categories are approximation of the microbial risk exposure, and if additionally are superimposed categories of patient resistance (higher risk associated with aging, obesity or other malnutrition, concomitant drugs, or viral or mycobacterial or neoplastic disease immune compromise), these same strata are called class I, II, and III.

26. Which abscess is the most important one to be drained?

Show answer
It is the last abscess that counts in drainage because the patient’s dramatic response is often only achieved when the last pus is drained. Draining a pelvic abscess, for example, but leaving behind a subphrenic abscess, would not result in the quenching of the inflammatory mediators of the sepsis syndrome.
27. Is postoperative fever the earliest and most frequent sign of an incisional infection? Show answer
Postoperative fevers are much more frequent than are wound infections, and the typical wound infection presents far later. The principal sources of postoperative fever are:

* Wind (atelectasis or pneumonia)
* Water (urinary tract infection)
* Walk (get your patient up and around; thrombophlebitis)
* Wound

28. Should you begin amphotericin at the first isolation of Candida species drawn from any intravenous catheter line?

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No. Again, remember the distinction between colonization and infection, as well as the source from which the specimen is taken. The IV lines through which hyperalimentation solutions are infused make colonization possible. The presence of a fungus such as Candida species is frequent in patients who do not have an invasive fungal infection or a true candidemia. The latter might be distinguished from catheter colonization by a blood culture drawn from another source, such as a venopuncture. If evidence of any invasive fungal infection is also present (e.g., as endoscopic biopsy of inflammatory mucositis), a choice of antifungal therapies is now indicated.
Topical fungal solutions (e.g., mycostatin mouthwashes or lavage) may control the local fungal infection and may sometimes be instituted as prophylaxis in high-risk patients (e.g., patients on antirejection therapy for bone marrow or solid organ transplantation).
Systemic antifungal agents include fluconazole, caspifungin, and amphotericin.

29. Are antibiotic drug combinations always superior to a single antibiotic agent?

Show answer
Monotherapy is superior to combination antibiotic treatment regimens, but this is provable probably only in the highest-risk patients. With the carbapenem class antibiotic agents, a large multicenter clinical trial proved imipenem therapy superior to aminoglycoside and a macrolide antibiotic, with survival demonstrably superior only in the patients with the highest APACHE scores. Ertapenem monotherapy was the equivalent of ceftriaxone and metronidazole in a smaller, more recent trial.
More is not always better, and the R and S on culture reports does not translate directly to the M and M (morbidity and mortality) at the Death and Complications Conference reports. It is not just important that the effective antibiotic regimen kills the bacteria; also important are how this microbicidal effect is carried out and what effect it may have on the patient in quenching or prolonging the systemic inflammatory response.

30. Is antibody treatment of circulating endotoxin a clinically important tool?

Show answer
Not yet. The neutralization of circulating endotoxin might give a theoretic benefit to patients with sepsis, and animal studies looked promising. But antigen/antibody complexes initiate complement cascade and release of activate leukocyte products such as leukotrienes that may further augment the inflammatory process. The complexes are also filtered in the kidney where they may further impair renal function. To date, no clinical therapeutic benefit has been demonstrated for such monoclonal antibody therapy.

31. What is the role of human recombinant activated protein C in patients with sepsis?

Show answer
Of the multiple clinical trials of mediator neutralization or receptor blockade, the evidence to date seems marginally favorable only for a few, and the major response to treatment comes from early and complete control of the focus of sepsis (not the cytokine sequelae).

References
WEB SITES

1. http://www.acssurgery.com/abstracts/acs/acs0102.htm
2. http://www.medscape.com
* Search: preoperative antibiotics

BIBLIOGRAPHY
1. Bartlett JG: Intra-abdominal sepsis. Med Clin North Am 79:599-617, 1995. Medline Similar articles
2. Bernard GR, Vincent JL, Laterre PF, et al: Efficacy and safety of recombinant human activated protein C for severe sepsis. N Engl J Med 344:699, 2001.

3. Bilik R, Burnweit C, Shandling B: Is abdominal cavity culture of any value in appendicitis? Am J Surg 175:267-270, 1998.
4. Christou NV, Turgeon P, Wassef R, et al: Management of intra-abdominal infections. The case for intraoperative cultures and comprehensive broad-spectrum antibiotic coverage. The Canadian Intra-abdominal Infection Study Group. Arch Surg 131:1193-1201, 1996. Medline Similar articles
5. Ciftci AO, Tanyei FC, Buyukpamukcu N, Hicsonmea A: Comparative trial of four antibiotic combinations for perforated appendicitis in children. Eur J Surg 163:591-596, 1997. Medline Similar articles
6. Falagas ME, Barefoot L, Griffith J, et al: Risk factors leading to clinical failure in the treatment of intra-abdominal or skin/soft tissue infections. Eur J Clin Microbiol Infect Dis 15:913-921, 1996. Medline Similar articles
7. Geelhoed GW: Preoperative skin preparation: Evaluation of efficacy, timing, convenience, and cost. Infect Surg 85:648-669, 1985.

Surgical Infectious Disease. Management Of Surgical Infections

admin — Tue, 07 Jul 2009 07:33:12 +0000

MANAGEMENT OF SURGICAL INFECTIONS

21. What is the drug of choice for the treatment of an abscess?

Show answer
A knife. Surgically drain the abscess. Abscesses have no circulation of blood within them to deliver an antibiotic. The antibiotic, even if injected directly into the abscess, would be worthless because the abscess contains a soup of dead microorganisms and white blood cells (WBCs). Even if the organisms were barely alive, they would not be reproducing and incorporating the antibiotic. The drug most likely would not work at all at the pH and pKa conditions of the abscess environment.

If there is an indication for an antibiotic, it would be in the circulation around the compressed inflammatory edge of the abscess and the cellulitis (at the vascularized “peel of the orange”) and uncontaminated tissue planes through which the necessary drainage must be carried out. A focal infection is managed by a local treatment, which is both necessary in all abscesses and sufficient treatment in many. Adjunctive systemic antibiotics are occasionally indicated for protection of the tissues through which drainage is carried out. If it helps to make this fundamental surgical principle clear, here is the rule of thumb for management of abscesses: Where there is pus, let there be steel. Perhaps one of the most gratifying procedures in all of medicine is the drainage of pus with immediate relief of local and systemic symptoms (e.g., a perirectal abscess).

22. Which abscess treatment is the important one in determining the outcome of a patient with intraabdominal sepsis?

Show answer
It is the drainage of the last abscess that counts. There should be little applause for drainage of a pelvic abscess in the patient who retains a subphrenic abscess. The patient responds dramatically when the last pus is drained.
This has been an area of significant advance in managing surgical infections because noninvasive scanning capability has facilitated the finding of multiple pockets of pus. Furthermore, such modalities as the computed tomography (CT) scan not only find but also percutaneously direct the fixing of the last abscess. What might have been an indication for an exploratory return trip to the operating room only a decade before (i.e., a failing patient on appropriate therapy should trigger the first response, “Where’s the pus?”) is now a good indication for a CT scan to find and drain the focal infection.

23. Which is preferred for draining an intraabdominal abscess, a needle or a knife?

Show answer
Which can be done most expeditiously? The patient with intraabdominal sepsis is very ill, and the earliest, safe drainage is the procedure of choice. There may be advantages to the less invasive CT scanning, which can be repeated and has less morbidity if the results are negative. Surgery, on the other hand, can fix associated conditions that may have caused the abscess, such as the devitalized loop of bowel or the leak in the anastomosis that can be exteriorized. Each method is likely to find multiple collections, and each can leave external drains for lavage and continuing drainage. Whether by needle or by knife, the urgency and adequacy of local treatment of focal infection determine which methods takes precedence.

24. What is the role of gallium scintiscanning in early finding of abscesses in the abdomen?

Show answer
There is none. Ordering a gallium scan is a temporizing means of self-deception that some progress is being made in finding out what is wrong with the patient. In fact, it merely postpones decisions about intervention in critical illness for several days, often to a point beyond salvage. Gallium scanning involves bowel prepping, a vigorous WBC response from an active bone marrow, and false-positive test results at the sites of tubes and incisions. It is a time-consuming and unreliable test that is the obverse of the principles of early and definitive management. Do not order a gallium scan to satisfy a consultant that “something is being done for this patient.”

Surgical Infectious Disease. Prophylaxis

admin — Tue, 07 Jul 2009 07:31:13 +0000

PROPHYLAXIS

17. Should systemic antibiotic prophylaxis be used in elective colon resection?

Show answer
Yes, beyond any statistical shadow of a doubt. At least two dozen clinical trials have been carried out using placebo controls against a variety of antibiotics, principally those active against at least the anaerobic-predominant flora, and nearly all have shown a reduction in infectious complications in the antibiotic group. Never again should this point need repeating, and no patient should be placed at risk when systemic antibiotic prophylaxis has been established as the standard of care. No new clinical trials against placebo in this group of patients with known risk can be performed ethically given the confirmed risk reduction.
Other risk groups (e.g., cesarean section after membrane rupture) besides patients undergoing colon resection have been standardized by trials in large patient populations and have shown similar risk reduction. The benefit of prophylaxis has been demonstrated. In other groups of patients that cannot be standardized because of unusual contamination factors or unique factors of host resistance impairment, guidelines for rational prophylaxis should follow similar principles.

18. Are two prophylactic doses better than one in preventing infection? Are three doses better still?

Show answer
Only one dose of prophylactic antibiotic can be proved, beyond statistical or clinical doubt, to be efficacious-the dose in systemic circulation at the time of the inoculum. Whether the dose needs to be repeated one or more times during the 24 hours after the inoculum depends on the blood levels of the drug, which are largely a function of protein binding and clearance rate. We also know for sure that 10 days of the same prophylactic drug that is efficacious if given immediately before the inoculum results in a higher risk of infection than no antibiotic at all.
KEY POINTS: PREOPERATIVE ANTIBIOTIC PROPHYLAXIS

1. Timing of administration is the most important factor.
2. Dose 30 minutes before incision so that antibiotic is circulating before the inoculum.
3. No evidence supports continuation of prophylaxis beyond 24 hours.

19. What factors determine the timing of antibiotic administration under the criteria of prophylaxis?

Show answer
The one immutable principle has been set out above-the most important element in timing of prophylaxis is that the drug be circulating before the inoculum. When should it stop? When the reduction in infection risk is no longer provable and before continued use will defeat the prophylactic purpose (as explained above). To summarize with an arbitrary rule of thumb: there is no justification for prophylactic antibiotic 24 hours after the inoculum of an invasive procedure.

What does this rule imply? Should we not continue prophylaxis for weeks to cover the presence of a prosthetic hip joint? Presumably, the prosthetic hip will be in the patient for many years-but surely you do not argue that the antibiotic should continue on a daily basis as long as the hip is in place! What is “prophylaxed” is not the prosthetic hip but the procedure of implantation. And it is not only implantation that poses a risk to the patient with a prosthesis-so does hemorrhoidectomy done years later, for which prophylaxis is made mandatory by the presence of the hip prosthesis.
The prosthetic or rheumatic heart valve is a risk, but the indication for the use of prophylactic antibiotics is an invasive procedure-a root canal is an example in which an inoculum is unavoidable. Operations are covered by prophylactic antibiotics; the conditions that are risk factors during the operation are not.

20. To be safe, why not administer prophylactic antibiotics to all patients undergoing any kind of operation?

Show answer
Can you give me the indication for a prophylactic antibiotic in a patient undergoing a clean elective surgical procedure that implants no prosthesis, such as hernia repair?
“Sure,” one of my brighter students once responded, “the patient who has a serious impairment in host response, such as acute granulocytic leukemia in blast crisis.”
I responded, “Why on earth are you fixing his hernia? That is a clean error [hopefully not a clean kill] in surgical judgment that has nothing to do with antibiotics at all. A patient with that degree of host impairment does not undergo an elective surgical procedure.”
Rule of thumb: If you can provide the indication for a prophylactic antibiotic to cover a clean elective nonprosthetic operation for a patient, you have provided the contraindication for the operation.

Surgical Infectious Disease. Antibiotics

admin — Tue, 07 Jul 2009 07:24:59 +0000

ANTIBIOTICS

11. Are antibiotics the classic wonder drugs?

Show answer
Only because you wonder if they are going to work, if they are going to cause more harm than good, and if the next generation will be unaffordable or toxic.
Skepticism is healthy with regard to any procedure or agent in heath care but especially with regard to antibiotics, which are embraced almost universally as agents that both prevent and cure infections. The primacy of the host defense in this vital process and the potential interference by the very drugs given credit for infection control are overlooked. We must look critically at the limited role that antibiotics should play in health care and restrain their overuse, which generates even more harm than unnecessary expense.

12. What is meant by generations of antibiotics, as in third-generation cephalosporins?

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The earliest antibiotics were bacteriostatic, largely through interference in protein synthesis, so that they might keep a microorganism from reproducing even if they did not kill it. The difference between infestation (presence of living microbes in the host) and infection (replication and spread of microorganisms in the host) may be useful in understanding how earlier drugs possibly controlled infection but were less capable of eliminating organisms in any brief period of therapy.
Penicillin changed all that. It may be the first antibiotic with a legitimate claim to the title “wonder drug” because it has the microbicidal capability of eradicating sensitive organisms. Penicillin was the first generation of the beta-lactam antibiotics, joined by the congener first-generation cephalosporins (e.g., cefazolin). They shared beta-lactam structure and had good gram-positive coverage with less range in any effect over gram-negative microbes.
The second-generation beta-lactam antibiotics (e.g., cefoxitin) covered new classes of microbes beyond gram-positive aerobes, such as many of the Bacteroides species, but had little effect on gram-negative aerobic microbes. Because the third-generation cephalosporins covered some of the latter microbes, they were touted as single-agent therapy for all principal-risk flora.

As with penicillin, the original wonder drug, the wonderment waned with failures of the new agents because of rapidly induced antimicrobial resistance. The most easily measured and calculated difference in the generations is cost: wholesale values are about $2.00/g for the first generation, $5.00/g for the second, and $30.00/g for the third. Despite this bracket creep in cost, the higher generations lose some of their potency against the original gram-positive organisms for which the first-generation agents were truly wonderful. Therefore, it takes 2 g of moxalactam to be half as good as 1 g of cefazolin for gram-positive coverage. It does not take a pharmacoeconomist to ask, “What have I got in return for this 60-fold surcharge?”

13. What is the role of third-generation cephalosporins in surgical prophylaxis?

Show answer
None (no more wondering here!). If the principal-risk flora are gram-positive, the first generation is better; if the anaerobic risk is sizable, the second generation is better. And either class is cheaper by far and seems to have generated less resistance than the third-generation cephalosporins, which are unconscionably expensive for use in prophylaxis and rarely as effective as other single-agent therapy for established surgical infection. Specific indications, such as pediatric meningitis, hospital-acquired pneumonia, or other specific infections outside the indications of surgical predominance, might use or exclude these agents.

14. How do enzyme inhibitors combined with antibiotics enhance their antimicrobial spectrum?

> Show answer
Microorganisms have defense mechanisms of their own, and the strains that have the capacity to make antibiotic-degrading enzymes achieve an unnatural selection advantage with the widespread use of antibiotics. This is what happened to penicillin: penicillinases emerged. But clever pharmaceutical manufacturers closed that loophole for bacterial ingenuity in degrading penicillin by strategic placement of a methyl group to ruin the survival fitness of penicillinase producers. Methicillin was the result, but the persistence of the microbes means that we now have a plague of methicillin-resistant Staphylococcus aureus (MRSA). Besides, microbes outnumber pharmaceutical manufacturers and have a shorter turnaround time than the approval process of the Food and Drug Administration (FDA). Microbes will always be ahead of us in ingenuity if only because of their numbers.
Newer strategies by the bacteria included the production of beta-lactamases. The response of the pharmaceutical industry was a group of inhibitors of beta-lactamase, such as clavulanic acid or sulbactam. The combination of a beta-lactamase inhibitor with a modified penicillin such as ampicillin should have enhanced activity against bacteria that produce beta-lactamase, provided that they were ampicillin-sensitive in the first place. Higher doses of the original agent for a shorter time may accomplish the same effect, often at lower cost, because the combined drugs were developed much more recently and are under patent protection.

15. What are the most expensive kinds of antibiotic therapy?

Show answer

* Drugs that are given when they are not needed.
* Drugs that are badly needed but do not work.
* Drugs that cause more harm than good because of host toxicity, whatever their antibiotic potential.

16. Can oral antibiotics be given in place of intravenous antibiotics in seriously ill surgical patients?

Show answer
Yes, if only they could take them! These patients almost invariably can take nothing by mouth (NPO), are often unconscious, and are as likely as not to be on a ventilator. In addition, the gut has been put out of commission by nasogastric suction tubes, laparotomy, and ileus, and primary intraabdominal problems often associated with the need for the antibiotics, such as intraabdominal sepsis and pancreatitis. Usually such patients are on complete gut rest and are likely to be on parenteral nutrition as well.

The attempt to use some form of gut-delivered antibiotic is based on the favorable pharmacokinetics and spectrum of quinolones, which can be started intravenously and switched as soon as possible to the oral form when feeding has resumed. Nearly all such patients begin on some form of intravenous (IV) antibiotic program and the start-up of the antibiotic regimen is more important than the form to which patients are tapered before treatment is discontinued.

Surgical Infectious Disease

admin — Tue, 07 Jul 2009 07:22:00 +0000

15 SURGICAL INFECTIOUS DISEASE
Glenn W. Geelhoed M.D., M.P.H., DTMH

1. Have modern antibiotic developments controlled many, if not most, of the problems of surgical infection?

Show answer
No. In seriously ill surgical patients in intensive care unit (ICU) settings, the problems of sepsis have increased and remain among the principal causes of death in ICU patients, especially those with multiple organ failure and impairments of host defense. Antibiotic treatment may change the biographical sketch of the flora associated with patients’ deaths but cannot overcome the multiple causes of failing host resistance to infection that accompany barrier breeches to microbial invasion and the inflammatory and immunologic responses to the “usual suspects.”

2. What kinds of barrier breech allow microbial invasion that may set up surgical infection?

Show answer
The skin and mucosal linings of the body maintain a barrier between the multifloral outside world and the sterile interior milieu of the tissues and organs (even when the outside world is a tube of heavily populated flora through the middle of usually sterile body cavities, such as the gastrointestinal [GI] tract). It is easy to see the barrier breech when a knife penetrates the skin, carrying exterior flora beneath the skin, or when that knife perforates and spills the contaminated contents of the gut into the abdomen. It is less obvious when the breech is caused by a low-flow state or when inadequate nutrition or toxins impair mucosal immunoglobulins, making the “bug-body barrier” permeable. These polymicrobial communities of organisms may begin to invade through the breech in such barriers, particularly if there are further failures in the third line of defense in humoral and cellular resistance.

3. What is the difference between contamination and infection?

Show answer
The presence of microorganisms does not an infection make!
Resident communities of flora on body surfaces do little harm, and gut flora are even beneficial when contained in the gut. It is even possible for bacteria to be transiently present outside their usual commensal residences without constituting an infection in the normally intact host. For example, in vigorously brushing one’s teeth, gram-negative bacteria of various kinds that are resident in the oral cavity are introduced into the bloodstream but probably quickly were eliminated by normal defense mechanisms-unless they met lowered host resistance or seeded a prosthetic heart valve.

4. How can the enormous load of bacteria in the lower GI tract be beneficial?

Show answer
Bugs can be beautiful. These are the same bacteria that have lived with and in humans symbiotically for millennia. They synthesize vitamin K-something we literally cannot do without-or crowd out pathogenic organisms by their overwhelming numbers. They also help to metabolize bile salts and play a role in detoxifying some environmental hazards, similar to septic systems.

5. Whenever intraabdominal bowel spillage is encountered, is it mandatory to culture the fecal contamination and obtain sensitivities of all identified organisms?

Show answer

No. There is a difference between contamination and infection. Therefore, cultures of fecal spillage into the peritoneum will not provide useful information. The contaminant, just because of its change in position with reference to the bowel wall, is not likely to be sterile. When would you like the laboratory to quit? Will you be content to hear a report of Escherichia coli and bacteroides, two of the more than 800 species that even the most compulsive laboratory can hardly be competent to identify, given the exposure to air and time lapse until processing on different media? How will information from a sampling error of mixed, community-acquired contaminants change your therapy? If, for instance, no anaerobes are identified from the fecal specimen, will you be so confident that they are not present as to exclude these species from coverage?
The lesson to be learned is that culture of community-acquired contaminants is expensive, incomplete, and unedifying; the culture of invading microbes in infections, particularly hospital-acquired microbes that persist after treatment, may give critical information and is a more appropriate use of microbiologic resources.

6. What are preps (e.g., bowel preps)?

Show answer
Preps are decontamination procedures, designed to reduce resident flora before an elective invasive procedure. Preps may take the form of a simple process such as an alcohol swab smeared over the skin before a quick prick of the subcutaneous injection or may involve preparation of a larger area of the skin surface for the surgical field of incision (see question 7).
A bowel prep is similarly designed to reduce the resident flora in the gut through (1) mechanical catharsis (i.e., purge); (2) osmotic or volume dilution with large volumes of saline, other electrolyte solutions, or mannitol; or (3) oral administration of nonabsorbed antibiotics. Of these methods, the most important is clearly mechanical catharsis because it purges huge amounts of flora, which may account for up to two thirds the dry weight of colon contents. One of the most cogent reasons for the choice of certain oral antibiotics in bowel preps (see question 9) is their vigorous cathartic action.

7. How is the skin or mucosal cavities of a patient sterilized to prepare a sterile field for operative incision?

Show answer
There is one way, hardly recommended, by which patients can be “sterilized”: similar to instruments and drapes, they can be placed in an autoclave. But short of this absurd example, the skin is never sterile. Decontamination processes are never perfect, particularly in so complex a tissue with crevices and accessory skin structures in which bacteria reside. Resting gloved hands on a “sterile field” does not include the skin or mucosal surfaces.
At best, we simply reduce the flora to the low-level inoculum that can be handled by most intact host defense systems-as in the example of brushing your teeth-but living tissue surfaces are never “sterile.” A method that kills all microbial organisms from such surfaces would also devitalize mammalian cells and render them more susceptible to lower-level microbial inocula.

8. What means can be used to reduce surface resident flora without further injuring the skin or mucosa?

Show answer

* Volume lavage (for mnemonic value only: dilution is the solution to pollution)
* Defatting, which solubilizes the sebaceous oils that may trap flora
* Microbicidal killing with a bacteriostatic agent

To an amazing extent, one cheap, simple fluid that may serve as a diluent, fat solvent, and antimicrobial is alcohol. Alcohol is nearly ideal as prepping solution, with the minor disadvantages that it is dehydrating and minimally flammable. Because it vaporizes and disappears, flora may spread from interstices, outside the field, or even via aerosolized fallout onto the field, thus requiring the addition of extended-duration bacteriostasis to the alcohol prep.
Iodine also kills bacteria but with a greater hazard to sensitive mammalian cells (it oxidizes the cell walls of small plants). A lower initial concentration of iodine and a longer duration of action can be achieved by incorporation of an iodophor, a substance in nearly universal use in preps. The application of moisture- and vapor-permeable “incise drapes” or desiccation-preventing “ring drapes” may further retard repopulation of flora over the prepped (but still not sterile) field.

9. What are “pipe cleaner” antibiotics?

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Pipe cleaners are orally administered antibiotic regimens that reduce the flora in the GI tract, from which they are not well absorbed. They are an almost ideal component of bowel preps because they are potent cathartic agents and accomplish the vast majority of their “pipe cleaning” by mechanical purgative action. The most popular pipe cleaners include a neomycin or erythromycin base.

10. What is selective gut decontamination? How does it work?

Show answer
It does not work. This method used pipe cleaners in patients at high risk for the development of sepsis from multiple organ failure with the theoretic aim of reducing the risk involved in barrier breech of the GI tract and inoculation with gut flora. Good experimental evidence indicated that this method should reduce the high mortality rate in seriously ill patients at high risk of surgical sepsis. After prolonged clinical trials, however, it failed to demonstrate a benefit in patient survival. The likely reason is that whereas the laboratory studies were done in intact animal models with functioning host defense systems, failures of defense beyond the barrier breech may explain why selective gut decontamination failed to benefit seriously ill patients. Furthermore, resident hospital flora repopulated the purged gut over time, but with virulent forms of microbes selected by their resistance to the broad-spectrum antibiotics. The method still has some use in patients undergoing procedures such as high-dose chemotherapy or bone marrow transplantation and in some patients isolated in “life islands” (e.g., patients with immunodeficiency diseases or burns).

Properties In Evaluation Of The Acute Abdomen. Surgical Treatment

admin — Tue, 07 Jul 2009 07:17:51 +0000

SURGICAL TREATMENT

22. If the patient is sick (and not getting better), what should be done?

Show answer
After fluid resuscitation, the patient’s abdomen should be explored. An exploratory laparotomy has been touted as the logical conclusion of a complete physical examination.

23. Is a negative laparotomy harmful?

Show answer
Yes, but patients can uncomfortably survive a negative laparotomy, whereas missed bowel infarction (or appendicitis) can be life-threatening.

24. Name the most challenging problem in all of medicine.

Show answer
An acute abdomen.

References
WEB SITE
http://www.acssurgery.com/abstracts/acs/acs0301.htm
BIBLIOGRAPHY
1. D’Agostino J: Common abdominal emergencies in children. Emerg Med Clin N Am 20:139-153, 2002. Full article
2. Dhillon S, Halligan S, Goh V, et al: The therapeutic impact of abdominal ultrasound in patients with acute abdominal symptoms. Clin Radiol 57:268-271, 2002. Medline Similar articles Full article
3. Gajic O, Urrutia LE, Sewani H, et al: Acute abdomen in the medical intensive care unit. Crit Care Med 30:1187-1190, 2002. Medline Similar articles Full article
4. Rozycki GS, Tremblay L, Feliciano DV, et al: Three hundred consecutive emergent celiotomies in general surgery patients: Influence of advanced diagnostic imaging techniques and procedures on diagnosis. Ann Surg 235:681-689, 2002. Medline Similar articles Full article

Properties In Evaluation Of The Acute Abdomen. Lab Stadies

admin — Tue, 07 Jul 2009 07:11:15 +0000

LABORATORY STUDIES

15. How is a complete blood count helpful?

Show answer
1. Hematocrit. If the hematocrit is high (> 45%), the patient is most likely dry or may have chronic obstructive pulmonary disease. If it is low (< 30%), the patient probably has a more chronic disease (associated with blood loss-always do a rectal and test the stool for blood).
2. White blood cell count.It takes hours for inflammation to release cytokines and elevate the white blood cell count. A normal white blood cell count is entirely consistent with significant abdominal trouble.

16. Is urinalysis necessary?

Show answer
Yes. White blood cells in the urine may redirect attention to the diagnosis of pyelonephritis or cystitis. Hematuria points to renal or ureteral stones. Because an inflamed appendix may lie directly on the right ureter, red and white blood cells may be found in the urine of patients with appendicitis.

17. What is a “three-way of the abdomen”?

Show answer
1. Upright chest radiograph. Look for free air under the diaphragm (perforated viscus) and pneumonia or pneumothorax.
2. Upright abdomen. Look for free air under the diaphragm and air-fluid levels (intestinal obstruction). Remember to look for sigmoid or rectal air (partial obstruction).
3. Supine abdomen. This radiograph tells nothing.

Most ureteral stones can be visualized. Only 10% of gallstones are radiopaque, and appendiceal fecaliths are rarely noted.
Honors: Air in the biliary system indicates a biliary-enteric fistula; this in association with intestinal air-fluid levels makes the diagnosis of gallstone ileus.
KEY POINTS: RADIOGRAPHIC EVALUATION FOR THE ACUTE ADBOMEN

1. May assist in diagnostic evaluation but should not supplant physical exam in evaluaton of an acute abdomen.
2. Three-way of the abdomen: look for free air under the diaphragm, intrathoracic pathology, air-fluid levels, dilated alimentary canal, distal air in rectum.
3. Ultrasound: useful for biliary, ob-gyn, and vascular assessments; may note intraperitoneal or retroperitoneal fluid collections.
4. Computed tomography: increasing use in clinical arena, with excellent visualization of abdominal structures. Drawbacks: cost, radiation exposure.

18. What is a sentinel loop?

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Except in children (who swallow everything, including air), small bowel gas is always pathologic. A single loop of small bowel gas adjacent to an inflamed organ (e.g., the pancreas) may point to the diseased organ.

19. Is ultrasound valuable?

Show answer
Yes, if the working diagnosis is cholecystitis, gallstones, ectopic pregnancy, ovarian cyst, abdominal aortic aneurysm, or intraperitoneal/retroperitoneal fluid.

20. Is abdominal computed tomography (CT) valuable?

Show answer
Yes, if the working diagnosis is an intra-abdominal abscess (sigmoid diverticulitis), pancreatitis, retroperitoneal bleeding (leaking abdominal aortic aneurysm; this patient should have gone straight to the operating room), or intrahepatic or splenic pathology.

21. What is a double-contrast CT scan?

Show answer
The bowel is delineated with barium or Gastrografin. The blood vessels are delineated with an iodinated vascular dye. The CT scan precisely displays the abdominal contents relative to vascular and intestinal landmarks. Contrast CT of pancreatitis is valuable to assess zones of perfusion or necrosis.

Properties In Evaluation Of The Acute Abdomen. Physical Exam

admin — Tue, 07 Jul 2009 07:07:25 +0000

PHYSICAL EXAMINATION

7. Are vital signs important?

Show answer
Yes. They are vital. If heart rate and blood pressure are on the wrong side of 100 (heart rate > 100 beats/min, systolic blood pressure < 100 mmHg), watch out! Tachypnea (respiratory rate >16) reflects either pain or systemic acidosis. Fever may develop late, particularly in the immunosuppressed patient who may be afebrile in the face of florid peritonitis.

8. What is rebound?

Show answer
The peritoneum is well innervated and exquisitely sensitive. It is not necessary to hurt the patient to elicit peritoneal signs. Depress the abdomen gently and release. If the patient winces, the peritoneum is inflamed (rebound tenderness).

9. What is mittelschmerz?

Show answer
Mittelschmerz is pain in the middle of the menstrual cycle. Ovulation frequently is associated with intraperitoneal bleeding. Blood irritates the sensitive peritoneum and hurts.

10. What do bowel sounds mean?

Show answer
If something hurts (e.g., a sprained ankle), the patient tends not to use it. Inflamed bowel is quiet. Bowel contents squeezed through a partial obstruction produce high-pitched tinkles. Bowel sounds are notoriously unreliable, however.

11. Explain the significance of abdominal distention.

Show answer
Distention may derive from either intraenteric or extraenteric gas or fluid (worst of all, blood). Abdominal distention is always significant and bad.

12. Is abdominal palpation important?

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Yes. Remember, the patient is (or should be) the surgeon’s friend. There is no need to cause pain. Palpation guides the surgeon to the anatomic zone of most tenderness (usually the diseased area). It is best to start palpation in an area that does not hurt. Rectal (test stool for blood) and pelvic examinations localize pathology further.

13. What is Kehr’s sign?

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The diaphragm and the back of the left shoulder enjoy parallel innervation. Concurrent left upper quadrant and left shoulder pain indicate diaphragmatic irritation from a ruptured spleen or subdiaphragmatic abscess.

14. What is a psoas sign?

Show answer
Irritation of the retroperitoneal psoas muscle by an inflamed retrocecal appendix causes pain on flexion of the right hip or extension of the thigh.

Properties In Evaluation Of The Acute Abdomen

admin — Tue, 07 Jul 2009 07:04:30 +0000

14 PRIORITIES IN EVALUATION OF THE ACUTE ABDOMEN
Alden H. Harken M.D.

1. What is the surgeon’s responsibility when confronted by a patient with an acute abdomen?

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1. To identify how sick the patient is
2. To determine whether the patient (a) needs to go directly to the operating room, (b) should be admitted for resuscitation or observation, or (c) can be sent safely home

2. Which is the most dangerous course?

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To send the patient home.

3. Is it important to make the diagnosis in the emergency department?

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No. Frequently time spent confirming a diagnosis in the emergency department is lost to inhospital resuscitation or treatment in the operating room. The only patient who needs a relatively firm diagnosis is a patient who is to be sent home.

4. If the essential goal is not to make the diagnosis, what should the surgeon do?

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1. Resuscitate the patient. Most patients do not eat or drink when they are getting sick. Most patients are depleted of at least several liters of fluid. Fluid depletion is worse in patients with diarrhea or vomiting.
2. Start a big IV line.
3. Replace lost electrolytes (see Chapter 7).
4. Insert a Foley catheter.
5. Examine the patient (frequently).

5. Are symptoms and signs uniquely misleading in any groups of patients?

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Yes. Watch out for the following groups:

* The very young, who cannot talk.
* Diabetics, because of visceral neuropathy.
* The very old, in whom, much as in diabetics, abdominal innervation is dulled.
* Patients taking steroids, which depress inflammation and mask everything.
* Patients with immunosuppression (a heart or kidney transplant patient may act cheerful even with dead or gangrenous bowel).

6. Summarize the history needed.

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1. The patient’s age. Neonates present with intussusception; young women present with ectopic pregnancy, pelvic inflammatory disease, and appendicitis; the elderly present with colon cancer, diverticulitis, and appendicitis.
2. Associated problems. Previous hospitalizations, prior abdominal surgery, medications, heart and lung disease? An extensive gynecologic history is valuable; however, it is probably safer to assume that all women between 12 and 40 years old are pregnant.
3. Location of abdominal pain. Right upper quadrant: gallbladder or biliary disease, duodenal ulcer. Right flank: pyelonephritis, hepatitis. Midepigastrium: duodenal or gastric ulcer, pancreatitis, gastritis. Left upper quadrant: ruptured spleen, subdiaphragmatic abscess. Right lower quadrant: appendicitis (see Chapter 37), ectopic pregnancy, incarcerated hernia, rectus hematoma. Left lower quadrant: diverticulitis, incarcerated hernia, rectus hematoma. Note: Cancer, unless it obstructs (colon cancer), and bleeding (diverticulosis) typically do not hurt.
4. Duration of pain. The pain of a perforated duodenal ulcer or perforated sigmoid diverticulum is sudden, whereas the pain of pyelonephritis is gradual and persistent. The pain of intestinal obstruction is intermittent and crampy. Note: Although the surgeon is rotating through a gastrointestinal service, the patient may not know this and may present with urologic, gynecologic, or vascular pathology.

Surgical Wound Infection

admin — Tue, 07 Jul 2009 06:58:10 +0000

13 SURGICAL WOUND INFECTION
Steven L. Peterson D.V.M., M.D.

1. Why should we worry about surgical wound infection?

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Approximately 30 million patients undergo surgery each year in the United States, and 20% of these patients acquire at least one nosocomial infection in the postoperative period. Infections at surgical sites are the third most common form of these infections and complicate 1-12% of all operations. The risk of death is four times higher in patients who develop wound infections, and each infection costs $12,000-30,000 to treat.

Commonly reported rates for specific operations are:

2. What comprises a surgical wound infection?

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Surgical wound infections more appropriately are called surgical site infections (SSIs) and must occur within 30 days of surgery unless a foreign body is left in situ. In the case of implanted foreign material, 1 year must elapse before surgery can be excluded as causative. SSIs are subdivided based on depth of tissue involvement into three clinically relevant categories.

1. Superficial incisional SSIs-involving only the skin and subcutaneous tissue
2. Deep incisional SSIs-involving deep soft tissue layers, such as fascial or muscle layers of the incision
3. Organ space SSIs-involving any anatomic structure opened or manipulated during the operative procedure

3. List the classic signs of superficial incisional, deep incisional, and organ space SSIs.

Show answer
Superficial and deep incisional SSIs:

* Calor (heat)
* Rubor (redness)
* Tumor (swelling)
* Dolor (pain)
* Purulent drainage

Organ space SSIs should be suspected in the presence of systemic signs and symptoms:

* Fever
* Ileus
* Shock

Definitive diagnosis of organ space SSIs may require imaging studies.

4. Why do these infections occur?

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Many factors contribute; however, the fundamental principle is that traumatic and surgical wounds violate the normal protective layer of skin. The importance of an intact integument has been shown experimentally in which it was determined that an inoculum of 8 million bacteria is required for infection of intact skin, 1 million are required for violated skin, and only 100 are required when foreign material is present.

5. Surgery always violates the skin and we often leave foreign material. How can we avoid SSIs?

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Although it is true that the basic act of surgery compromises the patients’ defenses, we can take steps to prevent wound infection. These steps involve the surgeon and the patient.

6. What can the surgeon do to decrease SSIs?

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The first step the surgeon can take is appropriate hand washing. The classic surgical scrub consists of 3 minutes of brushing with povidone-iodine or chlorhexidine gluconate. This protocol has been shown to have a high rate of noncompliance, which may contribute to SSIs. Data indicate improved compliance with comparable SSI rates using a much simpler protocol consisting of a 1-minute hand wash with nonantiseptic soap followed by hand-rubbing with a liquid aqueous alcoholic solution. Whether such simpler scrub protocols also can be applied in the future to the preparation of the patient is unknown.

7. What else can the surgeon do to control SSIs?

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The surgeon may limit the duration of surgery and follow good surgical principles by eliminating dead space, controlling hemorrhage, minimizing placement of foreign material (including excessive suture), and exhibiting gentle tissue handling. The surgeon should ensure that the patient remains warm during the perioperative period. This simple act of warming was shown in two prospective studies to decrease significantly the incidence of SSIs.

8. Can’t the surgeon predict who is going to get infected and just give them lots of antibiotics to stop infection from happening?

Show answer
To a degree SSIs can be anticipated. Factors that have been shown to have some predictive value to the surgeon are the physical status of the patient as classified by the American Society of Anesthesiologists, results of intraoperative cultures, and duration of preoperative hospital stay. Adequacy of regional blood supply also is important, as evidenced by the low infection rate in facial wounds. The classic description of wounds based on degree of gross contamination also may be of value. This scheme places wounds into one of four categories:

1. Clean wounds are atraumatic wounds in which no inflammation is encountered, no breaks in sterile technique occur, and no hollow viscus is entered.
2. Clean-contaminated wounds are identical except that a hollow viscus is entered.
3. Contaminated wounds are caused by trauma from a clean source or by minor spillage of infected materials.
4. Dirty-infected wounds are caused by trauma from a contaminated source or gross spillage of infected material into an incision.

Reported infection rates for each category are 2.1%, 3.3%, 6.4%, and 7.1%. Antibiotics can help but only when used appropriately.

9. How do I use antibiotics correctly to prevent SSIs?

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First by knowing what organism you are targeting, then choosing an appropriate antibiotic and delivering it at the appropriate time via the appropriate route. Because you usually will not have a preoperative culture to guide therapy, you need to base your choice of antibiotic on predicted organisms. Staphylococci are the most common skin organism and the most common etiologic agent in SSIs. Cefazolin, a first-generation cephalosporin, is usually the recommended antibiotic for prophylaxis in clean surgical procedures. In circumstances in which known contamination has occurred, initial antibiotics should be tailored based on the violated organ’s common flora. If the gut was entered, enterobacteriaceae and anaerobes are common; biliary tract and esophageal incisions yield these organisms plus enterococci. The urinary tract or vagina may contain group D streptococci, Pseudomonas, and Proteus spp.

10. If antibiotics are used, how and when should they be administered?

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Maximal benefit is obtained when tissue concentrations are therapeutic at the time of contamination. Efficacy is enhanced when prophylactic antibiotics are administered IV 20-30 minutes before surgical incision; late administration is similar to no administration. Multiple-dose regimens have no proven benefit over single-dose regimens. Indiscriminate antibiotic selection outside recommended hospital protocols may increase the incidence of SSIs. In special circumstances, administration routes other than IV may be indicated.

KEY POINTS: WOUND CLASSIFICATION AND INFECTION RATE (%)

1. Clean: atraumatic, no breaks in sterile technique, no entry into respiratory, alimentary, or genitourinary tract (2.1%)
2. Clean-contaminated: same as above except entry into respiratory, alimentary, or genitourinary tract (3.3%)
3. Contaminated: trauma from a clean source or minor spillage of infected materials (6.4%)
4. Dirty: trauma from a contaminated source or spillage of infected materials (7.1%)

11. Name other routes that you would use for prophylactic antibiotic administration.

Show answer
In patients with nasal carriage of Staphylococcus aureus, intranasal administration of mupirocin ointment may have some efficacy in decreasing nosocomial and surgical site infections. In elective colon surgery, a meta-analysis of published studies indicated that orally administered antibiotics combined with IV antibiotics are superior to IV antibiotics alone in preventing surgical site infections.
12. Does all that pulsatile lavage the surgeon uses in the operating room really do any good? Show answer
Yes. High-pressure pulsatile lavage has been evaluated extensively in soft tissue contamination and shown to be seven times more effective in reducing bacterial load than bulb syringe lavage. The inherent elastic recoil of the soft tissues allows particulate matter to escape between pulses of fluid. The optimal pressure and pulse frequency seems to be 50-70 lb/in.2 and 800 pulses/min. Adding antibiotics to lavage solutions, although commonly practiced, has not been shown definitively to improve outcome.

13. What can the patient do to help decrease SSIs?

Show answer
Stop smoking. Although obesity, poor nutritional status, advanced age, and diabetes are risk factors for SSIs, cigarette smoking is probably the leading preventable patient factor for SSIs just like it is the leading preventable cause of death and disability in the United States. Half of all people who smoke eventually die from a smoking-related illness. Smoking not only kills, but also more than triples that risk of incisional wound breakdown; in one study, smoking increased the incidence of SSIs in clean operative procedures sixfold, from 0.6% to 3.6%. Tobacco use results in decreased blood flow and decreased oxygen delivery to the wound. Toxic tobacco by-products also directly impede all stages of wound healing. Despite this knowledge, surgeons continue to operate electively on smokers, and most smokers continue to smoke up until the day of surgery.

14. When prevention fails, what do you do for SSIs?

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The first line of therapy in SSIs is drainage. This is established by reopening the wound or, in the case of deep space infections, using computed tomography-guided or ultrasound-guided techniques for drain placement or presurgical planning. Antibiotic therapy is used to control associated cellulitis and generalized sepsis.

15. What may happen with untreated superficial or deep incisional SSIs?

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Locally the wound breaks down, and infection dissects through the tissue planes and continues to advance. If the infection progresses rapidly, necrotizing fasciitis may develop. Finally, the strength layers of the wound closure break open (dehisce).
16. Define wound dehiscence. Show answer
The partial or total disruption of any or all layers of the operative wound.

17. Define evisceration.

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Rupture of the abdominal wall and extrusion of the abdominal viscera.

18. What factors predispose to dehiscence?

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Age > 60 years, obesity and increased intra-abdominal pressure, malnutrition, renal or hepatic insufficiency, diabetes mellitus, use of corticosteroids or cytotoxic drugs, and radiation have been implicated in wound dehiscence. Infection also plays an important role; an infective agent is identified in more than half of wounds that undergo dehiscence. Despite these excuses, the most important factor in wound dehiscence is the adequacy of closure. Fascial edges should not be devitalized. Ideally the linea alba sutures should be placed neither too laterally nor too medially. Excessive lateral placement may incorporate the variable blood supply of the rectus abdominis muscle and compromise fascial circulation. Excessive medial placement misses the point of maximal strength at the transition zone between the linea alba and rectus abdominis sheath. In addition, sutures should be tied correctly without excessive tension, and suture material of adequate tensile strength should be chosen.

19. When does wound dehiscence occur?

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It may occur at any time after surgery; however, it is most common between the 5th and 10th postoperative days, when wound strength is at a minimum.

20. What are the signs and symptoms of wound dehiscence?

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Normally a ridge of palpable thickening (healing ridge) extends about 0.5 cm on each side of the incision within 1 week. Absence of this ridge may be a strong predictor of impending wound breakdown. More commonly, leakage of serosanguineous fluid from the wound is the first sign. In some instances, sudden evisceration may be the first indication of abdominal wound dehiscence. The patient also may describe a sensation of tearing or popping associated with coughing or retching.

21. Describe the proper management of wound dehiscence.

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If the dehiscence is not associated with infection, elective reclosure may be the appropriate therapeutic course. If the condition of the patient or wound makes reclosure unacceptable, however, the wound should be allowed to heal by second intention. An unstable scar or incisional hernia may be dealt with at a later, safer time. Dehiscense of a laparotomy wound with evisceration is a surgical emergency with a reported mortality of 10-20%. Initial treatment in this instance consists of appropriate resuscitation while protecting the eviscerated organs with moist towels; the next step is prompt surgical closure. Exposed bowel or omentum should be lavaged thoroughly and returned to the abdomen; the abdominal wall should be closed; and the skin wound should be packed open. Vacuum-assisted wound closure may be valuable in select cases.

References
WEB SITE
http://www.acssurgery.com/abstracts/acs/acs0102.htm
BIBLIOGRAPHY
1. Barie PS: Modern surgical antibiotic prophylaxis and therapy: Less is more. Surg Infect 1:23-29, 2000. Full article
2. Garner GB, Ware DN, Cocanour CS, et al: Vacuum-assisted wound closure provides early fascial reapproximation in trauma patients with open abdomens. Am J Surg 182:630-638, 2001. Medline Full article
3. Kluytmans J, Voss A: Prevention of postsurgical infections: Some like it hot. Curr Opin Infect Dis 15:427-432, 2002. Medline Similar articles
4. Krueger JK, Rohrich RJ: Clearing the smoke: The scientific rationale for tobacco abstention with plastic surgery. Plast Reconstr Surg 108:1063-1073, 2001.
5. Myles PS, Iacono GA, Hunt JO, et al: Risk of respiratory complications and wound infection in patients undergoing ambulatory service. Anethesiology 97:842-847, 2002. Full article
6. Parienti JJ, Thibon P, Heller R, et al: Hand-rubbing with an aqueous alcoholic solution vs traditional sugical hand scrubbing and 30-day surgical site infection rates: A randomized equivalence study. JAMA 288:722-727, 2002. Medline Similar articles Full article
7. Perl TM, Cullen JJ, Wenzel RP, et al: Intranasal mupirocin to prevent postoperative Staphylococcus aureus infections. N Engl J Med 346:1871-1877, 2002. Medline Similar articles Full article
8. Seltzer J, McGraw K, Horsman A, Korniewicz DM: Awareness of surgical site infections for advanced practice nurses. ACCN Clin Iss 13:398-409, 2002. Full article