Janet M.J. Hammond

Double-blind study of selective decontamination of the digestive tract in intensive care

Selective decontamination of the digestive tract (SDD), by means of non-absorbable antibiotics, to prevent infection in intensive-care units (ICUs) remains controversial; there is evidence that the regimen reduces the incidence of secondary infection, but no convincing reduction in morbidity or mortality has been shown and the costs and effect on microbial resistance patterns need further study. In a double-blind, placebo-controlled trial, we have tried to find out whether SDD should be used routinely in all ICU patients at high risk of secondary infection. All patients admitted to the ICU who were thought likely to stay in the unit for at least 5 days and to need intubation for longer than 48 h were enrolled and randomly allocated to groups receiving placebo or SDD (amphotericin, colistin, and tobramycin applied to the oropharynx and enterally); all patients received intravenous cefotaxime for 72 h. Of 322 patients randomised, 83 were withdrawn (80 ICU stay or duration of intubation too short, 3 protocol violations). 239 medical, trauma, and surgical patients completed the trial period (114 SDD, 125 placebo). There were no differences between SDD and placebo groups in incidence of infection (30 [26%] vs 43 [34%] patients; p = 0.22), duration of ICU stay (mean 16.2 [14.3] vs 16.8 [12.3] days), hospital stay (29.9 [SD 25.0] vs 31.9 [22.2] days), or mortality (21 [18%] vs 21 [17%]). SDD substantially increased the costs of intensive care. Mechanisms other than bacterial colonisation of the gut may bring about substantial numbers of secondary infections in ICUs. Routine use of SDD in multidisciplinary ICUs cannot be recommended.

Long-term effects of selective decontamination on antimicrobial resistance

OBJECTIVE To determine whether selective decontamination of the digestive tract exerts any long-term effects on antimicrobial resistance patterns. DESIGN A surveillance and interventional study comparing the antimicrobial sensitivity patterns of clinically important bacterial isolates the year before a 2-yr, double-blind, randomized, controlled study of selective decontamination of the digestive tract, and for the year thereafter when no use of the regimen was made. SETTING A ten-bed respiratory intensive care unit (ICU) in a 1,200-bed teaching hospital. PATIENTS All 1,528 patients admitted to the ICU over the 4-yr study period were included. There were 406 patients admitted in the year before the study of decontamination of the digestive tract (65% medical, 23% surgical, and 12% trauma), of whom 76% required mechanical ventilation. There were 719 patients admitted during the 2-yr study of selective decontamination (55% medical, 28% surgical, and 17% trauma), of whom 79.6% required mechanical ventilation. There were 403 patients admitted in the subsequent year (61% medical, 25% surgical, and 14% trauma), of whom 76.9% required mechanical ventilation. INTERVENTIONS We performed daily clinical monitoring to detect nosocomial infection, with microbiological investigation when clinically indicated, as well as twice-weekly routine microbiological surveillance sampling. Antimicrobial susceptibility testing using standard laboratory methods was also performed. Selective decontamination of the digestive tract included parenteral cefotaxime and oral and enteral polymyxin E, amphotericin B, and tobramycin. MEASUREMENTS AND MAIN RESULTS The occurrence rate of nosocomial infection was 20.6%, 16.6%, and 25.3%, respectively, in the three study periods. In the year after selective decontamination, there was an increase in the occurrence rate of infection (p = .005), with an-associated increase in infections caused by the Enterobacteriaceae, while a reduction in the level of resistance to the third-generation cephalosporins were found (p = .07). There was a progressive increase in the occurrence rate of infections caused by Acinetobacter species (p = .05). Only 11 infections over the 4 yrs were caused by Enterococcus species. Staphylococcal infections were uncommon (5.7% of admissions), and the level of methicillin resistance did not change. No increase in aminoglycoside resistance occurred. CONCLUSION No long-term effects on antimicrobial resistance or the spectrum of nosocomial pathogens could be attributed to the use of selective decontamination of the digestive tract over a 2-yr period in a respiratory ICU admitting all categories of patients.

Selective decontamination of the digestive tract in multiple trauma patients--is there a role? Results of a prospective, double-blind, randomized trial.

Objective: To evaluate the efficacy of the technique of selective decontamination of the digestive tract in preventing the development of secondary infection and its influence on morbidity and mortality rates in multiple trauma patients with chest injuries requiring intermittent positive‐pressure ventilation. Design: Prospective, double‐blind, randomized study. Setting: A multidisciplinary respiratory intensive care unit (ICU) in a 1,500‐bed teaching hospital. Patients: Seventy‐two patients (mean Injury Severity Score of 29.5) who were intubated for >48 hrs and remained in the ICU for >5 days. Interventions: Patients were randomized on admission to receive selective decontamination therapy or placebo. All patients received intravenous cefotaxime for 72 hrs and the treatment group received oral and enteral selective decontamination with amphotericin B, polymyxin E, and tobramycin (n = 39), while the placebo group received a placebo containing oral paste and enteral solution (n = 33). Measurements: Secondary infection was determined clinically and microbiologically and surveillance cultures were monitored for gastrointestinal colonization. Results: The patient groups were fully comparable for age, severity of illness, and compromising factors. There was no difference in the number of patients infected (11 treatment group vs. 11 placebo), infections (17 vs. 16) and deaths (5 vs. 3); the duration of ICU (15.5 vs. 14.2 days) and hospital stays (26.3 vs. 25.5) were also similar. Microbiological surveillance cultures confirmed effective elimination of aerobic Gram‐negative bacilli, and infections in the treatment group were largely due to Staphylococcus aureus and Staphylococcus epidermidis. Conclusion: We have been unable to show any benefit from the use of selective decontamination of the digestive tract in the prevention of secondary infections in multiple trauma patients. (Crit Care Med 1994; 22:33‐39)

Influence of amikacin as the primary aminoglycoside on bacterial isolates in the intensive care unit

Amikacin was introduced as the primary aminoglycoside in our hospital to prevent the further development of multiply resistant Gram-negative organisms. This study compares clinical and microbiological data before and after institution of this policy to evaluate the influence on clinical outcome in patients as well as changing resistance patterns in the respiratory ICU. Patient populations were similar in terms of severity of illness (Acute Physiology and Chronic Health Evaluation II scores), age, ventilation, invasive procedures, and the incidence of various diseases. We found that the rate of amikacin resistance increased from 8.5% to 39.6% with an increase in resistance to tobramycin (19.3% to 33.3%) and netilmicin (23.9% to 47.9%) over the same period despite minimal usage of these drugs. The clinical outcome was similar in the periods contrasted. Our findings suggest that restricting aminoglycosides to amikacin only resulted in increasing Gram-negative resistance although there was no significant effect on patient outcome.

Intensive care management of community-acquired Klebsiella pneumoniae

The clinical features of 18 patients with Klebsiella pneumoniae requiring intensive care unit (ICU) management are presented. All patients required ventilatory support; 17 were given constant positive pressure ventilation and 10 required greater than 10 cm positive end expiratory pressure. The clinical picture was characteristic: pre-existing medical disease, clinical features of severe pneumonia and copious purulent bronchial secretions, Gram--ve organisms on Grams stain and lobar consolidation on the chest radiograph were common. Septicaemic shock, confusion and uncompensated metabolic acidosis were the presenting clinical features predicting a poor outcome. Antimicrobial chemotherapy, that combined an aminoglycoside and a third generation cephalosporin to ensure adequate early antibiotic serum levels, may help to improve the prognosis.

Selective decontamination of the digestive tract

When the intestinal flora is susceptible, selective decontamination of the digestive tract (SDD) reduces colonization of the alimentary tract by aerobic Gram-negative bacilli, and ventilator-associated pneumonia is seen in units with a high rate of nosocomial infection. Although mortality is generally unaltered in studies of SDD, a number of deaths can be directly attributed to ventilator-associated pneumonia; no study has yet had sufficient power to demonstrate a reduction in mortality. Reasons for failure of SDD include infections by organisms that are acquired directly into the trachea thus bypassing the digestive tract, and failure to prevent colonization of the alimentary tract by resistant micro-organisms. As with any excessive antibiotic usage, prolonged use of SDD is likely to have an impact on the microbial ecology of an intensive care unit, thus making microbiological surveillance essential. The role of SDD at present remains controversial, but may be helpful in intensive care units where there is a high incidence of secondary infection.