Chapter 20. Prevention of Surgical Site Infections

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Chapter 20. Prevention of Surgical Site Infections

Andrew D. Auerbach, M.D., M.P.H.
University of California, San Francisco School of Medicine

Subchapter 20.1. Prophylactic Antibiotics

Background

Surgical site infections (SSI) include superficial incisional infections, infections of the deep incision space and organ space infections.^1,2 A large body of evidence supports the premise that SSIs can be prevented through administration of appropriate prophylactic antibiotics. Two national organizations, the federal Centers for Disease Control and Prevention (CDC) and the American Society for Health System Pharmacists (ASHP), have recently synthesized this vast literature to produce comprehensive guidelines regarding the administration of prophylactic antibiotics across a broad range of procedures.^3,4 Because of the breadth of this literature, we limited the focus of this review of strategies to prevent SSIs to adult surgery and procedures that typically occur in the operating room (as opposed to procedures such as endoscopy, interventional cardiology, or radiology procedures).

Practice Description

Antimicrobial prophylaxis refers to a brief course of an antimicrobial agent administered just before an operation begins in order to reduce intraoperative microbial contamination to a level that will not overwhelm host defenses and result in infection.⁴ To maximize the benefits of antimicrobial prophylactic, the agent used should be safe, inexpensive, and bactericidal with an in vitro spectrum that covers the most probable contaminants for the operation.⁴ Administration, usually by intravenous infusion, should be timed so that a bactericidal concentration is present in serum and tissues by the time the skin is incised.⁵ This practice is now standard of care and recommended by professional societies.⁶ Therapeutic levels in serum and tissues should be maintained until, at most, a few hours after the incision is closed in the operating room.⁴

Prevalence and Severity of the Target Safety Problem

Surgical site infections are a common complication of care, occurring in 2-5% of patients after clean extra-abdominal surgeries (e.g., thoracic and orthopedic surgery) and in up to 20% of patients undergoing intra-abdominal procedures.^7-12 Studies following patients into the post-discharge period have reported even higher rates of postoperative infection.^13-16 These complications increase morbidity for patients and consume substantial additional resources.^17-21

Opportunities for Impact

Approximately 80-90% of surgical patients receive some kind of antibiotic prophylaxis, though recent studies have shown that choice of regimen, timing of administration or duration of prophylaxis is inappropriate in approximately 25-50% of cases.^22-27

Study Designs and Outcomes

As previously noted, the literature on prophylactic antibiotics is extensive. Therefore, the review was limited to evidence from Level 1A study designs. We identified 9 relevant studies examining the use of prophylactic antibiotics to prevent surgical site infections: 7 meta-analyses and 2 systematic reviews.^28-36 (Tables 20.1.1 and 20.1.2) These reviews were of high quality and limited their source material to randomized controlled trials. Although additional randomized trials have been published since these reviews were performed, updating the results of each review was beyond the scope of this project. All studies examined measured rates of site infection directly (Level 1), using previously published definitions to allow comparability. In addition, the rates of sepsis, length of stay, and physiologic measures were reported. One meta-analysis ³¹ and one systematic review ³³ combined rates of several relevant infectious outcomes.

Evidence for Effectiveness of the Practice

All studies showed a marked reduction in the odds or relative risk of SSI when antibiotic prophylaxis was employed. None of the meta-analyses reviewed explicitly examined the timing of prophylaxis, although many studies pooled data from investigations of antibiotic regimens administered in the immediate preoperative period, (i.e., within minutes to an hour of initial incision). Two meta-analyses in our review^29,31 suggested a trend towards lower rates of infection with use of broader-spectrum antibiotic prophylaxis, such as third generation cephalosporins. When compared with single dose prophylaxis, multiple dose prophylaxis generally did not result in significant additional benefit.^29,30,35 In fact, Tanos et al found the odds of SSI were significantly less with single dose prophylaxis.³¹ Gillespie et al reported a greater relative risk of infection with single dose prophylaxis with a short-acting antibiotic when compared with multiple dose prophylaxis.³⁶ However, the risk of infection with single dose prophylaxis using long-acting antibiotics did not differ significantly from that seen with multiple-dose regimens.

Potential for Harm

None of the meta-analyses analyzed reported rates of adverse events (such as allergic reactions or nosocomial infections) associated with antibiotic prophylaxis of any type or duration. Both of the systematic reviews^33,36 noted a trend towards more frequent adverse events with the use of antibiotic prophylaxis. Authors of both systematic reviews observed that these events were reported rarely and that variation in the definition of "adverse events" across studies made pooling results difficult.

Infection with Clostridium difficile affects a large number of hospitalized patients and has significant clinical and economic implications. As many as 16% of C. difficile colitis cases in surgical patients can be attributed to prophylaxis alone,³⁷ with higher risk for this complication among patients receiving broad-spectrum antibiotics or prolonged courses of therapy. Shortening the duration of antibiotic administration may reduce potential risks of prophylaxis (see Chapter 14). Emergence of other types of resistant pathogens is an additional theoretical concern of inappropriate antibiotic prophylaxis; our literature search found no data describing effect of antibiotic prophylaxis on population-level incidence of these pathogens.

Costs and Implementation

A number of studies have evaluated strategies for improving compliance with recommended practices for perioperative antibiotic prophylaxis. These include chart audit with feedback,³⁸ computerized decision support,^{23, 39-42} dissemination of guidelines,⁴³ total quality management (TQM) and continuous quality improvement (CQI) techniques,^44-47 provider education programs,^48,49 and comprehensive efforts by an infection control team.⁵⁰ Another promising and easily implemented method is to delegate the administration of prophylactic antibiotics to the anesthesia team or the holding room nursing staff.^{22, 25, 48}

Costs for systems to increase appropriate use of antibiotics will likely be offset by savings due to prevented infections. However formal analyses of the cost-effectiveness of specific programs to improve prophylaxis have not been reported.

Comment

For many surgical procedures there is clear evidence supporting the use of antibiotic prophylaxis, administered in a timely manner, to prevent surgical site infections. The reviews suggest that broader spectrum antibiotics may be superior to limited-spectrum antibiotics for intra-abdominal or gynecologic surgeries. In addition, single-dose antibiotic prophylaxis appears to be at least as effective as multiple-dose regimens for a broad range of surgical procedures and may pose less risk to patients in terms of adverse events (e.g., C. difficile colitis) and less risk to the population in terms of microbial resistance.

Future research will continue to address what prophylactic regimens are most effective for various surgical procedures. Investigation should also focus on methods to improve compliance. The optimal strategies for implementation will likely vary from institution to institution.

Table 20.1.1. Meta-analyses examining antibiotic prophylaxis*

Study	Trials Included	Surgical Procedures, Antibiotics	Results: Odds Ratio or Relative Risk of Infection (95% CI)
Kreter, 1992³⁵	28	Cardiothoracic surgery; cephalosporins	Cefazolin vs. placebo: OR 0.2 (0.10-0.48) Cefazolin vs. cefuroxime or cefamandole: OR 1.6 (1.03-2.45) Single dose vs. multiple dose regimen: no significant difference
McDonald, 1998³⁰	28	Multiple types of surgery; multiple antibiotics	Single dose vs. multiple dose antibiotics (all studies): OR 1.06 (0.89-1.25) Duration of multiple dose regimen <24 hours: OR 1.02 (0.79-1.32) Duration of multiple dose regimen >24 hours: OR 1.08 (0.86-1.36)
Meijer, 1990²⁹	42	Biliary surgery; cephalosporins	Antibiotic vs. placebo: OR 0.30 (0.23-0.38) Cephalosporin I vs. cephalosporin II or III: OR 1.18 (0.69-2)^a Single dose vs. multiple dose regimen: OR 0.80 (0.4-1.6)
Mittendorf, 1993²⁸	25	Abdominal hysterectomy; multiple antibiotics	Antibiotic vs. placebo (all studies): OR 0.35 (0.27-0.5); p<0.00001^b Cefazolin vs. placebo: OR 0.32 (0.18-0.6); p=0.0002^b Metronidazole vs. placebo: OR 0.24 (0.08-0.8); p=0.015 ^b
Sharma, 2000³⁴	6	Percutaneous gastrostomy; multiple antibiotics	Antibiotic vs. placebo (all studies): RR 0.73, NNT 5.7 Single dose regimens: RR 0.78, NNT 6.1
Tanos, 1994³¹	17	Abdominal hysterectomy; cephalosporins	Antibiotic vs. placebo (all studies): OR 0.35 (0.3-0.4) Cephalosporin I vs. placebo: OR 0.4 (0.3-0.5) Cephalosporin II vs. placebo: OR 0.37 (0.2-0.8) Cephalosporin III vs. placebo: OR 0.26 (0.1-0.5) Single dose vs. multiple dose regimen: OR 0.37 (0.3-0.5)
Wilson, 1992⁵¹	21	Multiple types of surgery; multiple antibiotics	Amoxicillin-clavulanic acid vs. other antibiotics (all studies): OR 0.84 (0.68-1.04) Trend favoring amoxicillin-clavulanic acid for biliary and gynecologic surgery.

* CI indicates confidence interval; NNT, number needed to treat; OR, odds ratio, and RR, relative risk.

^a Roman numerals I, II, III indicate generation of cephalosporin antibiotics.

^b P values were reported in article; OR were approximated based on figures.

Table 20.1.2. Systematic reviews of antibiotic prophylaxis*

Study

Trials Included

Surgical Procedures; Antibiotics

Results: Relative Risk of Infection (95% CI)

Gillespie, 2000³⁶

Long bone fractures; multiple antibiotics

Single dose antibiotic vs. placebo

Deep wound infection: RR 0.40 (0.24-0.67)
Superficial wound infection: RR 0.69 (0.50-0.95)
Urinary tract infection: RR 0.63 (0.53-0.76)
Pneumonia: RR 0.46 (0.33-0.65)

Multiple dose antibiotic vs. placebo:

Deep wound infection: RR 0.36 (0.21-0.65)
Superficial wound infection: RR 0.48 (0.28-0.81)
Urinary tract infection: RR 0.66 (0.4-1.0)
Pneumonia: RR 0.81 (0.41-1.63)
Adverse events: RR 1.83 (0.96-3.50)

Single dose short-acting antibiotic vs. multiple doses same agent up to 24 hours after surgery

Deep wound infection: RR 7.98 (1.01-62.0)
Superficial wound infection: RR 4.82 (1.08-21.6)
Urinary tract infection: RR 1.81 (1.01-3.23)

Single dose long-acting antibiotic vs. any multiple dose regimen lasting more than 24 hours

Deep wound infection: RR 1.10 (0.22-5.34)
Superficial wound infection: RR 0.57 (0.17-1.93)

Multiple doses administered over 24 hours or less vs. longer therapy

Deep wound infection: RR 1.1 (0.22-5.34)
Superficial wound infection: RR 0.57 (0.17-1.93)

Oral vs. parenteral prophylaxis

Insufficient data (single underpowered study)

Smaill, 2000³³

Cesarean section; multiple antibiotics

Impact of antibiotic prophylaxis on...

-Combined outcomes of fever, wound infection, sepsis and endometritis:

Elective Cesarean section: RR 0.25 (0.11-0.55)
Emergent Cesarean section: RR 0.39 (0.33-0.46)
Unspecified/nonelective: RR 0.37 (0.32-0.42)
All Cesarean section: RR 0.37 (0.33-0.42)

-Maternal side effects: RR 1.96 (0.86-4.49)

-Length of stay: 0.34 fewer days in hospital (0.17-0.52)

* CI indicates confidence interval; RR, relative risk.

References

1. Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for the Prevention of Surgical Site Infection. Hospital Infection Program, Centers for Disease Control and Prevention. Available at: http://www.cdc.gov/ncidod/hip/. Accessed April 29, 2001.

2. Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol 1999;20:250-278.

3. ASHP Therapeutic Guidelines on Antimicrobial Prophylaxis in Surgery. American Society of Health-System Pharmacists. Am J Health Syst Pharm 1999;56:1839-1888.

4. Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for Prevention of Surgical Site Infection, 1999. Centers for Disease Control and Prevention (CDC) Hospital Infection Control Practices Advisory Committee. Am J Infect Control 1999;27:97-132.

5. Classen DC, Evans RS, Pestotnik SL, Horn SD, Menlove RL, Burke JP. The timing of prophylactic administration of antibiotics and the risk of surgical-wound infection. N Engl J Med 1992;326:281-286.

6. Dellinger EP, Gross PA, Barrett TL, et al. Quality standard for antimicrobial prophylaxis in surgical procedures. The Infectious Diseases Society of America. Infect Control Hosp Epidemiol 1994;15:182-188.

7. Delgado-Rodriguez M, Sillero-Arenas M, Medina-Cuadros M, Martinez-Gallego G. Nosocomial infections in surgical patients: comparison of two measures of intrinsic patient risk. Infect Control Hosp Epidemiol 1997;18:19-23.

8. Horan TC, Culver DH, Gaynes RP, Jarvis WR, Edwards JR, Reid CR. Nosocomial infections in surgical patients in the United States, January 1986-June 1992. National Nosocomial Infections Surveillance (NNIS) System. Infect Control Hosp Epidemiol 1993;14:73-80.

9. Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG. CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol 1992;13:606-608.

10. Horan TC, Emori TG. Definitions of key terms used in the NNIS System. Am J Infect Control 1997;25:112-116.

11. Wallace WC, Cinat M, Gornick WB, Lekawa ME, Wilson SE. Nosocomial infections in the surgical intensive care unit: a difference between trauma and surgical patients. Am Surg 1999;65:987-990.

12. Scheel O, Stormark M. National prevalence survey on hospital infections in Norway. J Hosp Infect 1999;41:331-335.

13. Sands K, Vineyard G, Platt R. Surgical site infections occurring after hospital discharge. J Infect Dis 1996;173:963-970.

14. Waddell TK, Rotstein OD. Antimicrobial prophylaxis in surgery. Committee on Antimicrobial Agents, Canadian Infectious Disease Society. CMAJ 1994;151:925-931.

15. Medina-Cuadros M, Sillero-Arenas M, Martinez-Gallego G, Delgado-Rodriguez M. Surgical wound infections diagnosed after discharge from hospital: epidemiologic differences with in-hospital infections. Am J Infect Control 1996;24:421-428.

16. Lynch W, Davey PG, Malek M, Byrne DJ, Napier A. Cost-effectiveness analysis of the use of chlorhexidine detergent in preoperative whole-body disinfection in wound infection prophylaxis. J Hosp Infect 1992;21:179-191.

17. Vegas AA, Jodra VM, Garcia ML. Nosocomial infection in surgery wards: a controlled study of increased duration of hospital stays and direct cost of hospitalization. Eur J Epidemiol 1993;9:504-510.

18. Kirkland KB, Briggs JP, Trivette SL, Wilkinson WE, Sexton DJ. The impact of surgical-site infections in the 1990s: attributable mortality, excess length of hospitalization, and extra costs. Infect Control Hosp Epidemiol 1999;20:725-730.

19. Collins TC, Daley J, Henderson WH, Khuri SF. Risk factors for prolonged length of stay after major elective surgery. Ann Surg 1999;230:251-259.

20. Asensio A, Torres J. Quantifying excess length of postoperative stay attributable to infections: a comparison of methods. J Clin Epidemiol 1999;52:1249-1256.

21. Wong ES. The price of a surgical-site infection: more than just excess length of stay. Infect Control Hosp Epidemiol 1999;20:722-724.

22. Silver A, Eichorn A, Kral J, et al. Timeliness and use of antibiotic prophylaxis in selected inpatient surgical procedures. The Antibiotic Prophylaxis Study Group. Am J Surg 1996;171:548-552.

23. Larsen RA, Evans RS, Burke JP, Pestotnik SL, Gardner RM, Classen DC. Improved perioperative antibiotic use and reduced surgical wound infections through use of computer decision analysis. Infect Control Hosp Epidemiol 1989;10:316-320.

24. Finkelstein R, Reinhertz G, Embom A. Surveillance of the use of antibiotic prophylaxis in surgery. Isr J Med Sci 1996;32:1093-1097.

25. Matuschka PR, Cheadle WG, Burke JD, Garrison RN. A new standard of care: administration of preoperative antibiotics in the operating room. Am Surg 1997;63:500-503.

26. Gorecki P, Schein M, Rucinski JC, Wise L. Antibiotic administration in patients undergoing common surgical procedures in a community teaching hospital: the chaos continues. World J Surg 1999;23:429-432.

27. Zoutman D, Chau L, Watterson J, Mackenzie T, Djurfeldt M. A Canadian survey of prophylactic antibiotic use among hip-fracture patients. Infect Control Hosp Epidemiol 1999;20:752-755.

28. Mittendorf R, Aronson MP, Berry RE, et al. Avoiding serious infections associated with abdominal hysterectomy: a meta-analysis of antibiotic prophylaxis. Am J Obstet Gynecol 1993;169:1119-1124.

29. Meijer WS, Schmitz PI, Jeekel J. Meta-analysis of randomized, controlled clinical trials of antibiotic prophylaxis in biliary tract surgery. Br J Surg 1990;77:283-290.

30. McDonald M, Grabsch E, Marshall C, Forbes A. Single- versus multiple-dose antimicrobial prophylaxis for major surgery: a systematic review. Aust N Z J Surg 1998;68:388-396.

31. Tanos V, Rojansky N. Prophylactic antibiotics in abdominal hysterectomy. J Am Coll Surg 1994;179:593-600.

32. Song F, Glenny AM. Antimicrobial prophylaxis in colorectal surgery: a systematic review of randomized controlled trials. Br J Surg 1998;85:1232-1241. Published erratum appears in Br J Surg 1999;1286:1280.

33. Smaill F, Hofmeyr GJ. Antibiotic prophylaxis for cesarean section. In: The Cochrane Library, Issue 2, 2000. Oxford: Update Software.

34. Sharma VK, Howden CW. Meta-analysis of randomized, controlled trials of antibiotic prophylaxis before percutaneous endoscopic gastrostomy. Am J Gastroenterol 2000;95:3133-3136.

35. Kreter B, Woods M. Antibiotic prophylaxis for cardiothoracic operations. Meta-analysis of thirty years of clinical trials. J Thorac Cardiovasc Surg 1992;104:590-599.

36. Gillespie WJ, Walenkamp G. Antibiotic prophylaxis for surgery for proximal femoral and other closed long bone fractures. In: The Cochrane Library, Issue 2, 2000. Oxford: Update Software; 2000.

37. Crabtree TD, Pelletier SJ, Gleason TG, Pruett TL, Sawyer RG. Clinical characteristics and antibiotic utilization in surgical patients with Clostridium difficile-associated diarrhea. Am Surg 1999;65:507-511.

38. Zhanel GG, Gin AS, Przybylo A, Louie TJ, Otten NH. Effect of interventions on prescribing of antimicrobials for prophylaxis in obstetric and gynecologic surgery. Am J Hosp Pharm 1989;46:2493-2496.

39. Pestotnik SL, Evans RS, Burke JP, Gardner RM, Classen DC. Therapeutic antibiotic monitoring: surveillance using a computerized expert system. Am J Med 1990;88:43-48.

40. Pestotnik SL, Classen DC, Evans RS, Burke JP. Implementing antibiotic practice guidelines through computer-assisted decision support: clinical and financial outcomes. Ann Intern Med 1996;124:884-890.

41. Evans RS, Pestotnik SL, Classen DC, et al. A computer-assisted management program for antibiotics and other antiinfective agents. N Engl J Med 1998;338:232-238.

42. Evans RS, Pestotnik SL, Burke JP, Gardner RM, Larsen RA, Classen DC. Reducing the duration of prophylactic antibiotic use through computer monitoring of surgical patients. DICP 1990;24:351-354.

43. Dobrzanski S, Lawley DI, McDermott I, Selby M, Ausobsky JR. The impact of guidelines on peri-operative antibiotic administration. J Clin Pharm Ther 1991;16:19-24.

44. Koska MT. Using CQI methods to lower postsurgical wound infection rate. Hospitals 1992;66:62,64.

45. Kroll DA, Brummitt CF, Berry BB. A users group approach to quality improvement across an integrated healthcare delivery system. J Healthc Qual 2000;22:39-43.

46. Welch L, Teague AC, Knight BA, Kenney A, Hernandez JE. A quality management approach to optimizing delivery and administration of preoperative antibiotics. Clin Perform Qual Health Care 1998;6:168-171.

47. Woster PS, Ryan ML, Ginsberg-Evans L, Olson J. Use of total quality management techniques to improve compliance with a medication use indicator. Top Hosp Pharm Manage 1995;14:68-77.

48. Gyssens IC, Knape JT, Van Hal G, ver der Meer JW. The anaesthetist as determinant factor of quality of surgical antimicrobial prophylaxis. A survey in a university hospital. Pharm World Sci 1997;19:89-92.

49. Everitt DE, Soumerai SB, Avorn J, Klapholz H, Wessels M. Changing surgical antimicrobial prophylaxis practices through education targeted at senior department leaders. Infect Control Hosp Epidemiol 1990;11:578-583.

50. McConkey SJ, L'Ecuyer PB, Murphy DM, Leet TL, Sundt TM, Fraser VJ. Results of a comprehensive infection control program for reducing surgical-site infections in coronary artery bypass surgery. Infect Control Hosp Epidemiol 1999;20:533-538.

51. Wilson AP, Shrimpton S, Jaderberg M. A meta-analysis of the use of amoxycillin-clavulanic acid in surgical prophylaxis. J Hosp Infect 1992;22:9-21.

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Subchapter 20.2. Perioperative Normothermia

Background

The body temperature of patients may fall by 1 to 1.5° C during the first hour of general anesthesia.¹ Regional anesthesia also typically causes core hypothermia.² Intraoperative hypothermia impairs immune function (especially oxidative killing by neutrophils) and results in dermal vasoconstriction and reduced blood flow to surgical sites, which further increases the risk of surgical site infection by lowering tissue oxygen tension.³ Hypothermia also results in reduced platelet function, shivering associated with patient discomfort and activation of the sympathetic nervous system, and adverse cardiac events.²

Practice Description

Normal core temperature can be maintained during surgery through use of active measures including warmed intravenous fluids and inspired gases, as well as forced air warming. The latter involves an air blanket placed over the patient that circulates air warmed to 40° C. Water blankets may also be used, but are not as effective in maintaining body temperature.⁴ Patient temperature is monitored using conventional thermometer probes, with active measures adjusted to maintain core temperature near 36.5° C. Any method or combination of methods that maintains the target core temperature appears to have the same effect.²

Prevalence and Severity of the Target Safety Problem

See Subchapter 20.1.

Opportunities for impact

Attention to patient temperature is standard of care in intraoperative anesthesia management. However, there are no data on the extent to which active warming measures are currently used perioperatively.

Study Designs and Outcomes

We identified one randomized controlled trial³ and one retrospective cohort study⁶ evaluating the effect of active warming interventions on the rate of wound infection (Level 1 outcome). (Table 20.2.1). Wound infection was either defined as "suppuration requiring removal of sutures"³ or as in previously published definitions.⁷

Evidence for Effectiveness of the Practice

Kurz et al performed a randomized controlled trial of active warming in the intraoperative care of patients undergoing elective colectomy. All patients received aggressive perioperative hydration and intravenous opioids for pain relief, in an effort to maximize wound perfusion. Patients in the normothermia arm experienced a 68% reduction in the rate of wound infection, lower wound infection scores (as defined by the elements of the acronym ASEPSIS: Additional treatment, Serous discharge, Erythema, Purulent exudate, Separation of deep tissues, Isolation of bacteria, and duration of inpatient Stay), and shorter length of hospitalization.³ While the relatively high infection rate (19% of control group in this university-based population with a substantial degree of underlying disease) and suboptimal antibiotic prophylaxis (antibiotics continued for about 4 days postoperatively; see Subchapter 20.1) do not invalidate the study results, they do limit their generalizability.

In a retrospective cohort study based on chart reviews of 150 patients undergoing elective colectomy, Barone et al noted no independent association between intraoperative hypothermia (defined as temperature less than <34.3ºC) and the incidence of wound infections, or the length of stay. Explanation for differences in the findings of the two studies may relate to confounding due to the retrospective design of the study by Barone, or in differences in defining wound infections by the authors (suppuration requiring removal of sutures).⁸

Other potential benefits of maintaining perioperative normothermia have been reported in randomized controlled trials. Frank et al found the risk of morbid cardiac events (combined outcome of angina, myocardial ischemia or infarction, and ventricular arrhythmia) was significantly decreased among patients in the normothermia group (1% intervention vs. 6% control, p=0.02).⁹ Maintaining normothermia has also been associated with decreased blood loss and transfusion requirements among patients undergoing elective colectomy³ and hip arthroplasty.^10,11 Postoperative shivering, thermal discomfort, time to extubation, and duration of post-anesthesia recovery are all significantly reduced.^2,12

Potential for Harm

None of these studies reported an adverse effect directly related to these practices. Sigg et al observed a higher rate of wound bacterial colonization with the reuse of forced air coverlets.¹³

Costs and Implementation

Equipment for monitoring temperature is readily available in operating rooms. Kruz et al estimated the direct cost of fluid and forced air warming at $30 per case.⁹ Studies have not formally assessed all relevant costs, including additional physician time required. It is likely that added costs are largely offset by savings due to reduced surgical site infections and associated decreases in length of stay.

Comment

Given the evidence of effectiveness, the low potential for harm, and the simplicity of the intervention (including the ready availability of the equipment), maintenance of perioperative normothermia seems a promising practice to improve patient safety. The methodologically stronger of the 2 studies reviewed showed clear benefits. However, some of its benefits may not be generalizable to patient populations undergoing other procedures. For example, intraoperative hypothermia may have little impact on wound infections in patients undergoing cesarean section.¹⁴ Thus, additional study of the practice is needed in other settings. Furthermore, for some procedures hypothermia is likely to protect patients. Core temperature is often intentionally reduced to protect the myocardium and central nervous system during certain cardiac and neurosurgical procedures.^2,12,15 In such cases the potential benefits of normothermia may not outweigh the associated risks.

Table 20.2.1. Summary of studies reporting effectiveness of perioperative normothermia*

Study

Study Population; Intervention

Study Design, Outcomes

Results

Kurz, 1996³

200 patients (104 normothermia, 96 hypothermia) undergoing, elective colectomy in multicenter study; warmed gases, fluids and forced arm during operation vs. usual care

Level 1,
Level 1

Wound infection rate: 6% vs. 19% (p=0.009)

ASEPSIS score: 7 vs. 13 (p=0.002)

Days to sutures out: 9.9 vs. 10.9 (p=0.002)

Taking nutrition orally: 5.6 vs. 6.5 days (p=0.006)

Length of stay: 12 vs. 15 days (p=0.001)

Barone, 1999⁶

150 patients (101 normothermia, 49 hypothermia) undergoing elective colectomy at a single community hospital; no formal intervention (retrospective chart review, warming devices were used in 90% of patients)

Level 3,
Level 1

Wound infection rate: 12% in both groups

Multivariate models: no significant association between hypothermia and wound infection or length of stay

* ASEPSIS indicates Additional treatment, Serous discharge, Erythema, Purulent exudate, Separation of deep tissues, Isolation of bacteria, and duration of inpatient Stay.⁷

References

1. Matsukawa T, Sessler DI, Sessler AM, et al. Heat flow and distribution during induction of general anesthesia. Anesthesiology 1995;82:662-673.

2. Sessler DI. Mild perioperative hypothermia. N Engl J Med 1997;336:1730-1737.

3. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. N Engl J Med 1996;334:1209-1215.

4. Kurz A, Kurz M, Poeschl G, Faryniak B, Redl G, Hackl W. Forced-air warming maintains intraoperative normothermia better than circulating-water mattresses. Anesth Analg 1993;77:89-95.

5. American Society of Anesthesiologists. Standards of the American Society of Anesthesiologists. Available at: http://www.asahq.org/Standards/02.html. Accessed June 6, 2001.

6. Barone JE, Tucker JB, Cecere J, et al. Hypothermia does not result in more complications after colon surgery. Am Surg 1999;65:356-359.

7. Wilson AP, Treasure T, Sturridge MF, Gruneberg RN. A scoring method (ASEPSIS) for postoperative wound infections for use in clinical trials of antibiotic prophylaxis. Lancet 1986;1:311-313.

8. Sessler DI, Kurz A, Lenhardt R. Re: Hypothermia reduces resistance to surgical wound infections. Am Surg 1999;65:1193-1196.

9. Frank SM, Fleisher LA, Breslow MJ, et al. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial. JAMA 1997;277:1127-1134.

10. Schmied H, Kurz A, Sessler DI, Kozek S, Reiter A. Mild hypothermia increases blood loss and transfusion requirements during total hip arthroplasty. Lancet 1996;347:289-292.

11. Winkler M, Akca O, Birkenberg B, et al. Aggressive warming reduces blood loss during hip arthroplasty. Anesth Analg 2000;91:978-984.

12. Leslie K, Sessler DI. The implications of hypothermia for early tracheal extubation following cardiac surgery. J Cardiothorac Vasc Anesth 1998;12:30-34; discussion 41-34.

13. Sigg DC, Houlton AJ, Iaizzo PA. The potential for increased risk of infection due to the reuse of convective air-warming/cooling coverlets. Acta Anaesthesiol Scand 1999;43:173-176.

14. Munn MB, Rouse DJ, Owen J. Intraoperative hypothermia and post-cesarean wound infection. Obstet Gynecol 1998;91:582-584.

15. Winfree CH, Baker KZ, Connollly ES. Perioperative normothermia and surgical-wound infection. N Engl J Med 1996;335:749.

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