STUDIES OF THE EPIDEMIOLOGY OF STAPHYLOCOCCAL INFECTION. VI. INFECTIONS IN THE SURGICAL PATIENT

Wound complications

This article discusses postoperative wound complications in detail, including host factors that predispose the patient to nonhealing, technical factors in surgery that can reduce the likelihood of infection and dehiscence, and recommendations for postoperative management that can prevent wound healing problems. This discussion includes the treatment of wound complications, ranging from local wound care to various wound coverage options.

Hyperglycemia as a predictor for mortality in veterans with pneumonia

The elderly may have multiple problems including diabetes mellitus and pneumonia. This study was undertaken to evaluate the effect of hyperglycemia on the length of stay (LOS) and mortality of elderly veterans admitted for pneumonia. Forty-seven and forty-eight patients over the age of 60 admitted for the diagnosis of pneumonia at the Lexington, Kentucky and Iron Mountain, Michigan VAMC's respectively were evaluated. The mean age at Lexington was 72 and at Iron Mountain was 73.9. At Lexington the mean LOS was 39.5 days with a standard deviation of 9.2 for those with hyperglycemia (n = 18) and 16.5 days with a standard deviation of 2.5 for those without hyperglycemia (n = 29). At Iron Mountain the mean LOS was 21.5 days with a standard deviation of 3.3 for those with hyperglycemia (n = 10) and 13.6 days with a standard deviation of 1.2 for those without (n = 38). These differences were significant at p less than .01 using the 2-sample independent t-test. At Iron Mountain 5 of 38 (13%) of the patients with normoglycemia died during the hospital stay compared to 3 of 10 (30%) those with hyperglycemia. For Lexington the figures were 4 of 29 (13%) and 6 of 18 (33%) respectively. These differences were significant at p less than .05. Age did not have any significant effect on either mortality or length of stay. Hyperglycemia appears to be a significant predictor of a longer hospital course and increased mortality in elderly veterans hospitalized for pneumonia.

Empirical and mathematical models on the relationship between patient age and nosocomial infection

This paper proposes two models, one a purely empirical one and the other a mathematical one, which depict the relationship between patient age and nosocomial infection rate. The empirical model is based on the two age-specific phenomena, the acquisition of resistance to infection with age mainly in the early years of life and the deterioration of existing resistance mechanisms with ageing predominantly in the later years of life. The net effect of these two factors is shown to approximate into a quadratic relationship between age and nosocomial infection rate, like the type demonstrated in earlier experimental studies. The second mathematical model is derived from studies on cancer research and here the relationship between age and nosocomial infection rate for patients in the age group 30-70 years is represented by a log linear model. The model was tested against experimental data derived from large surveys on nosocomial infection and the resulting correlation coefficient was 0.98. The model was an extremely good fit when tested against postoperative wound infection rates as well as nasal carriage rate of antibiotic resistant Staph. aureus. Furthermore, when patients in the survey were subdivided into groups of male patients and female patients and into two groups based on the type of operative wound, the model was still found to be a very good fit to the experimental data. This confirmed the validity of the model even in the presence of other patient-related parameters. Finally, the model was tested against the results of a totally different experimental study conducted elsewhere and the resulting correlation coefficient was 0.999, which confirmed the validity of the model in a universal context.

Diabetes and abdominal surgery: the mutual risks

The patient with diabetes represents to the surgeon a particular challenge in the management of acute abdominal problems. In addition to their ongoing and potential metabolic problems, diabetics have specific difficulty in their ability to handle infections and heal wounds. The present report reviews the general principles in the peri-operative management of diabetics and discusses the implications in the diabetic of several specific clinical problems. In view of the known accelerated atherosclerosis associated with diabetes, the risks of anesthesia and surgery must be assessed in the context of the coronary, cerebral, visceral, and peripheral vascular status. Infections in diabetics (potential or established) must be treated aggressively and promptly. Acidosis in the diabetic with abdominal pain must be considered both a metabolic problem and a possible secondary manifestation of an intra-abdominal process. In view of these challenges, the need for careful, anticipatory management of the diabetic patient facing major abdominal surgery is clear.

Nosocomial infections in U.S. hospitals, 1975-1976: estimated frequency by selected characteristics of patients

To obtain estimates of the frequency of nosocomial infections nationwide, those occurring at the four major sites--urinary tract, surgical wound, lower respiratory tract and bloodstream--were diagnosed in a stratified random sample of 169,526 adult, general medical and surgical patients selected from 338 hospitals representative of the "mainstream" of U.S. hospitals. We estimate that in the mid-1970s one or more infections developed in 5.23 percent (+/- 0.16) of the patients and that 6.62 (+/- 0.24) infections occurred among every 100 admissions. Risks were significantly related to age, sex, service, duration of total and of preoperative hospitalization, presence of previous nosocomial or community-acquired infection, types of underlying illnesses and operations, duration of surgery, and treatment with urinary catheters, continuous ventilatory support or immunosuppressive medications. Seventy-one percent of the nosocomial infections occurred in the 42 percent of patients undergoing surgery and 56 percent in the 38 percent financed by Medicare, Medicaid or other public health care plans.

A bacteriological study of the immediate environment of a surgical wound

In an attempt to assess the importance of different aspects of the immediate wound environment during an operation, detailed bacteriological data were obtained in the operating theatre from 1000 patients operated upon in two different theatres.

Nasal and skin carriage of Staphylococcus pyogenes were found to be associated with a small number of autogenous infections, but no significant increase in the staphylococcal wound infection incidence could be shown in these groups. Skin carriage of other pathogens seemed to be of no importance with the disinfection methods used in the present study.

Settle-plate studies showed no apparent difference in the bacteriological hazard of the two operating theatre environments, neither appearing to constitute any real danger. Samples at the end of operation confirmed the importance of endogenous contamination with intestinal organisms during potentially dirty operations. Apart from the few autogenous infections, there was little evidence of staphylococcal wound sepsis arising as a result of contamination in the operating theatre. Hands and masks of members of the operating team could not be demonstrated as sources of contamination during operation.

There was no apparent difference in the bacteriological findings as they related to the different operating theatre environments.

Importance of the carrier state as a source of Staphylococcus aureus in wound sepsis

The relationship of pre-operative nasal and skin carriage of Staphylococcus aureus to wound colonization and sepsis was studied in 269 patients. Thirty-seven per cent of 96 carriers developed wound colonization as compared to 16 % among non-carriers (a statistically significant difference). The wound sepsis rates were 17 % and 9 % respectively. The combination of nasal and skin carriage was an important factor, since the sepsis rate among skin carriers (most of whom were nasal carriers as well) was 22%. Among carriers, the homologous strain was recovered from the majority of wound colonizations and from all instances of wound sepsis. A carrier strain also was recovered from 52% of the wounds colonized and from 50% of septic wounds in the entire study group. Profuse nasal carriage resulted in a significantly greater number of septic wounds (31%) than sparse carriage (9%). Wound cultures before closure, and skin from the initial incision site only once yielded a patient's carrier strain or a strain of Staph. aureus that was later recovered from the wound. The results indicate that measures designed to control the carrier state or to isolate the wound from the external environment should reduce wound sepsis by approximately one half.

Excellent technical aid was furnished by Eleanor Ford, R. N., Edith E. Silverman, Adrienne Marus, M. S., and Patricia Welch.