ICAAC Highlights

Surgical site infections are costly and deadly

Costs may not be reimbursed under managed care

Nosocomial surgical site infections (SSIs) can result in significant unreimbursed hospital expenses and dramatically increase patient mortality, researchers reported recently in San Diego at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

To assess the impact of SSIs, researchers at LDS Hospital at the University of Utah in Salt Lake City used computerized medical records, patient acuity information, and cost data.¹ The most recent data reviewed in the study were from August 1992, but data from as recently as 1997 will be reported in the next phase, says Tze Shien Lo, MD, infectious disease fellow at the hospital who presented the study at ICAAC.

The study compared 191 patients with hospital-acquired SSIs with 1,868 cohort patients without SSIs. The groups were well-matched for age, sex, acuity, and DRGs. Patients with SSIs had a mean length of stay of 14.5 days, while the matched cohort had a mean length of stay of 4.7 days. The mean attributable difference in length of stay between the two groups was 5.3 days.

"The mortality data was 6.8% for the case patients with nosocomial wound infections and for the matched cohort it was 1.1%," Lo says.

The matched cohort patients had a mean total cost of hospitalization of $6,030 vs. $18,621 for the cases. The mean attributable cost difference between the patient groups was $4,935. In addition, the authors noted that in 1992 there were 386 surgical wound infections at the hospital, which would have added an estimated 2,061 extra inpatient days in that year.

"[Under] traditional fee-for-service LDS Hospital could have recovered the cost associated with the extra length of stay by simply charging the patient or insurer," Lo and colleagues reported at ICAAC. "The extra estimated cost of surgical wound infections in 1992 would have been $1.9 million for LDS Hospital. Based on current managed care contracts 75% of this would not be recoverable."

In other ICAAC highlights, Wesley P. Kozinn, MD, FACP, and colleagues at Easton (PA) Hospital reported the presence of pathogenic bacteria on the surfaces of electronic ear-probe thermometers being used in the hospital.²

Like stethoscopes and other medical devices used on one patient after another, tympanic earprobe thermometers may spread infection between hospitalized patients, they surmised, recommending routine disinfection of the devices because they are handled by diverse health care workers and usually are shared between patients.

The tympanic thermometers provide rapid and convenient temperature measurements for hospital patients, who ordinarily require several temperature measurements per day. They represent an advance over electronic rectal probe thermometers that readily become contaminated during use, may cause injuries, and have been proven to contribute to the spread of hospital infections, they reported. Tympanic thermometers use a disposable probe tip cover, which is changed between patients to prevent cross-transmission. However, the thermometer handle may harbor pathogenic microbes, which can inadvertently be transferred to the attendant’s hands and then to patients, Kozinn and colleagues concluded.

The researchers tested tympanic thermometers for the presence of bacteria on surfaces touched by health care workers during use. The device consists of a storage base and hand unit, both of which were cultured. They obtained 44 cultures from 24 thermometers being used on Easton Hospital’s general medical/surgical wards, intensive care units, cardiac surgery service, kidney dialysis center, and cancer care unit.

All 24 thermometers showed growth of Staphy l ococcus epidermis, a common skin bacteria of recognized pathogenic potential, they reported. An average of 280 colonies of these bacteria were recovered from each device, and 40% of strains tested were resistant to a multitude of antibiotics. Two of the most important agents of hospital-acquired infections, Staphylococcus aureus and enterococci, were found on 8% and 12% of thermometers respectively. One S. aureus isolate was antibiotic-resistant, but vancomycin-resistant enterococci were not recovered.

Streptococcal bacteria, which can originate in the respiratory tract, were found on 21% of thermometers, suggesting mouth-to-hand transfer. The authors recommend routine disinfection of tympanic thermometers transferred from one patient to another, but say more research is needed to define optimal disinfection schedules and technique.

In another study presented at the conference, M.J. Struelens, MD, PhD, and colleagues at the Erasme Hospital in Brussels, Belgium, found that a drastic reduction of frequently used broad-spectrum antibiotics in an intensive care unit was associated with a dramatic improvement in antibiotic sensitivity.³

Laboratory monitoring of antibiotic-resistant bacteria in patients admitted to the ICU showed an alarming increase in the frequency of multiple-resistant Enterobacter aerogenes, a common cause of hospital-acquired infections. Over a four-year period from 1993 to 1996, resistance to the commonly used third-generation cephalo spor ins and fluoroquinolones increased threefold and sixfold, respectively. During the same period, hospital physicians’ prescription of those antibiotics increased by 37% and 270%, respectively. An epidemic strain of E. aerogenes originally was introduced into the ICU by admitting an infected patient in 1993, they reported. Epidemiologic investigations showed that the pathogen was spreading between patients despite infection control efforts that included wearing of gloves and gowns, hand washing, and placement of infected patients in private rooms.

Therefore, a decision was made to stop using antibiotics to which the bacteria were resistant, replacing the drugs with a new cephalosporin called cefepime for treatment of infected patients in the ICU. Over the following one-year evaluation period, the consumption of third-generation cephalosporins and fluoroquinolones decreased by 57% and 80%, respectively. During that same period, the frequency of overall resistance to third-generation cephalosporins and fluoroquinolones decreased from 27% to only 11%. Transmission of multidrug-resistant Enterobacter aerogenes strains was reduced by 89%.

"We conclude that this change of antibiotics used in the intensive care department for treatment of infection was helpful, together with infection control measures, [in] protecting our patients against the risk of infection caused by antibiotic-resistant bacteria," Struelens and colleagues concluded at ICAAC.

References

1. Lo TS, Classen DC, Burke JP, et al. Assessing the effect of nosocomial surgical wound infections on the cost of hospitalization by using a hospital information system. Abstract 0-3. Presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). San Diego; Sept. 24-27, 1998.

2. Kozinn WP, Lam M, Schenck N, et al. Bacterial flora of a hospital electronic ear-probe thermometer. Abstract K-135. Presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). San Diego; Sept. 24-27, 1998.

3. Struelens MJ, Byl B, Govaerts D, et al. Modification of antibiotic policy associated with decrease in antibiotic-resistant gram-negative bacilli in an intensive care unit. Abstract K-12. Presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). San Diego; Sept. 24-27, 1998.