Frequency and yield of postoperative fever evaluation.

OBJECTIVE: In women undergoing major gynecologic surgery, we wish to determine the frequency and yield of blood culture, urine culture, and chest X-ray evaluation of postoperative fever. METHODS: A retrospective review of 537 consecutive patients undergoing major gynecologic surgery was performed. In patients who developed postoperative fever, it was determined whether blood culture, urine culture, and/or chest X-ray were performed, and, if so, the frequency of positive results was evaluated. RESULTS: Two hundred eleven patients (39%) developed postoperative fever. Blood cultures were obtained in 77 of 211 (37%) febrile patients, urine cultures in 106 of 211 (50%) febrile patients, and chest X-ray in 54 of 211 (26%) febrile patients. Zero of 77 blood cultures were positive, 11 of 106 (10%) urine cultures were positive, and 5 of 54 (9%) chest X-rays were positive. Logistic regression revealed that late onset fever predicted for positive urine cultures and early onset fever and advanced age predicted for pneumonia. Eighty percent of patients with pneumonia were symptomatic. In 92% of patients with postoperative fever, no infections or pathologic process were diagnosed. CONCLUSION: Although postoperative fever is frequently evaluated by blood culture, urine culture, and chest X-ray, evaluation rarely yields positive results.

chest X-ray in 54 of 211 (26%) febrile patients. Zero of 77 blood cultures were positive, 11 of 106 (10%) urine cultures were positive, and 5 of 54 (9%) chest X-rays were positive. Logistic regression revealed that late onset fever predicted for positive urine cultures and early onset fever and advanced age predicted for pneumonia. Eighty percent of patients with pneumonia were symptomatic. In 92% of patients with postoperative fever, no infections or pathologic process were diagnosed.
Conclusion: Although postoperative fever is frequently evaluated by blood culture, urine culture, and chest X-ray, evaluation rarely yields positive results. Infect. Dis. Obstet. Gynecol. 6:252-255, 1998. (C) 1999 Wiley-Liss, Inc. KEY WORDS postoperative fever; urine culture; blood culture; chest X-ray gynecologic surgery, with rates of febrile morbidity reported as 32-52%. [1][2][3][4] Most studies contain less than 100 patients, z-4 These studies routinely state that urine culture, blood culture, and chest X-ray are obtained to evaluate postoperative fever. [1][2][3][4] However, evaluation of postoperative fever by blood culture, urine culture, and chest X-ray is based on anecdotal evidence and not on scientific analysis. Basic science research has shown that postoperative release of cytokines is a major cause of postoperative fever, s Routine use of preoperative prophylactic antibiotics has significantly decreased the incidence of operative site infection following major gynecologic surgeries. 1,6 To our knowledge, there are no large studies that have analyzed the yield of postoperative fever evaluation after major gynecologic surgery. Because of lack of scientific analysis, basic science evaluation of cytokines, use of prophylactic antibiotics, and increased pressure for cost control, we POSTOPERATIVE FEVER EVALUATION FANNING ET AL. wish to determine the frequency of postoperative fever evaluation and determine the yield of blood culture, urine culture, and chest X-ray evaluation of postoperative fever.

SUBJECTS AND METHODS
We conducted a retrospective analysis of all major gynecologic surgeries performed from January 1995 through January 1996. Major gynecologic surgical procedures included abdominal hysterectomy, vaginal hysterectomy, laparotomy, operative laparoscopy, hysterectomy with lymphadenectomy, ovarian cytoreduction, radical hysterectomy, and vulvectomy. No patients were excluded. Data collected included: fever, age, weight, smoking history, associated medical diseases, type of surgical procedure, blood loss, transfusions, operative time, length of bladder catheterization, length of hospitalization, and use of preoperative prophylactic antibiotics. We defined postoperative fever as any temperature ->38C excluding the day of surgery. Although the conventional definition of febrile morbidity is two temperatures ->38C taken six hours apart excluding the day of surgery, we chose to evaluate any temperature ->38C excluding the day of surgery because we were interested in the frequency and yield of any fever evaluation. It is our belief that some gynecologic residents and gynecologists evaluate fevers without waiting six hours for a second temperature evaluation. However, for completeness, we also evaluated febrile morbidity. In patients who developed postoperative fever, it was determined whether urine culture, blood culture, and/or chest X-ray were performed, and the results of these evaluations were examined. Because this was a retrospective study evaluating patients treated by a large number of clinical and full-time faculty members, no criteria existed for fever evaluation. This study was approved under expedient review by the Institutional Review Board.
Statistics were analyzed using the SPSS for Windows. Logistic regression analysis was used to determine if any preoperative or operative variables would significantly identify positive urine culture, blood culture, or chest X-ray.

RESULTS
Hospital records of 537 consecutive patients who underwent major gynecological procedures were   patients were symptomatic, with shortness of breath and/or chest pain. Of the 11 patients with urinary tract infections, the median length of postoperative fever was two days (range: 1-7 days). Only two of 11 patients were symptomatic. Two patients with negative blood culture, urine culture, and chest X-ray had significant pathology causing postoperative fever. One patient with daily spiking temperatures developed clinical features of lower extremity deep venous thrombosis, which was confirmed by Doppler. Another patient with daily spiking temperatures and significant malaise had a pelvic mass detected on physical exam, which was confirmed by computed tomography to be a pelvic abscess. Of the 211 patients with postoperative fever, only 8% were diagnosed with an infectious or pathologic process (11 urinary tract infections, five pneumonias, one pelvic abscess, one deep venous thrombosis). Logistic regression for predicting positive urine culture or pneumonia based on surgical characteristics (Table 1) and patient characteristics ( Table 2) was performed. The only characteristic that helped predict a positive urine culture was the day of temperature elevation (P .04). The later the temperature occurred, the more likely a urine culture would be positive. The chance of a chest X-ray being positive was also influenced by the day of temperature elevation (P .05). The earlier a temperature occurred postoperatively, the more likely the diagnosis of pneumonia. Also, the older the patient, the more likely a chest X-ray would be positive (P .03).
At our hospital, the charge for 77 blood cultures was $9,394; for 106 urine cultures, $7,950; and for 54 chest X-rays, $8,154. In this study, the charge for postoperative fever evaluation for one year was $25,498.

DISCUSSION
In our retrospective review, the incidence of postoperative fever after major gynecological surgery was 39%, and the incidence of febrile morbidity was 37%, which is consistent with other publications. [1][2][3][4] Thirty-seven percent of febrile patients had blood cultures obtained with no positive resuits. Fifty percent of febrile patients had urine cultures obtained with only 10% yielding positive results. Chest X-rays were obtained in 26% of febrile patients, with pneumonia documented in only 9%. Patients with postoperative pneumonia had early onset fever of a median length of three days and were usually symptomatic. Patients with postoperative urinary tract infection had late onset fevers of a median length of two days and were rarely symptomatic. Although not evaluated, because 92% of patients with postoperative fever had no infectious or pathologic process diagnosed, we must assume that the majority of postoperative fevers were secondary to noninfectious processes, such as cytokine release, atelectasis, hematoma reabsorption, etc.
We searched Medline from 1966 to 1998 for postoperative fever, postoperative blood cultures, postoperative urine cultures, and postoperative chest X-ray. A total of 1,407 articles were reviewed.
Although there were multiple studies evaluating postoperative fever following gynecologic surgery, 1-4 we identified only one additional study evaluating postoperative fever evaluation following gynecologic surgery. Swisher et al. 7  In conclusion, although we present the largest study analyzing postoperative fever evaluation following major gynecologic procedures, no definite conclusions can be made, because this study was retrospective. However, because of increasing cost restraints and the findings of no positive blood cultures and few positive urine cultures or chest Xrays, we cannot recommend routine evaluations of postoperative temperatures by urine culture, blood culture, and/or chest X-ray. It is our opinion that postoperative fever evaluation should be based on symptoms and physical examination. In symptomatic, older patients with persistent early postoperative temperature elevations, chest X-ray e.valuation seems appropriate. In patients with persistent late postoperative temperature elevations, urine cultures may be appropriate. We are presently performing a prospective trial of postoperative fever evaluation based on the above recommendations.