A Protocol for Empiric Treatment of ICU Patients with Pulmonary Infiltrates Reduces Antibiotic Use
October 1, 2000 4 minutes read
A Protocol for Empiric Treatment of ICU Patients with Pulmonary Infiltrates Reduces Antibiotic Use
abstract & commentary
Synopsis: This randomized trial provides strong evidence for a rational approach to the use of antibiotics in critical care patients with pulmonary infiltrates that is associated with improved outcomes while reducing antimicrobial use.
Source: Singh N, et al. Short-course empiric antibiotic therapy for patients with pulmonary infiltrates in the intensive care unit. A proposed solution for indiscriminate antibiotic prescription. Am J Respir Crit Care Med 2000;162:505-511.
An accurate diagnosis of the cause of pulmonary infiltrates is often difficult in the intensive care unit (ICU) patient. Many patients who do not have pneumonia are treated with antibiotics because of diagnostic uncertainty and clinician anxiety. Singh and colleagues performed a randomized trial comparing a protocol for empiric antibiotic use with usual care in ICU patients with new pulmonary infiltrates. They sought to determine if a brief (3 day) period of administration of a defined empiric protocol would lead to a decrease in antibiotic use without compromising outcome.
Patients with new onset pulmonary infiltrates were evaluated using the clinical pulmonary infection score (CPIS). The CPIS uses six readily accessible clinical variables to determine the likelihood that a patient has pneumonia;1 these include temperature, leukocyte count, sputum purulence, oxygenation, radiographic findings, and culture. Patients with a CPIS more than 6 were considered likely to have pneumonia, and were excluded from the study. Patients with a CPIS less than 6 were considered less likely to have pneumonia, and randomized. Those in the experimental group received ciprofloxacin 400 mg IV every 8 hours; control patients received usual care from the ICU staff. Patients were re-evaluated in three days. For patients in the protocol group, if the CPIS remained less than 6 and no additional foci of infection were apparent, antibiotics were stopped. If the CPIS was more than 6, antibiotic therapy was continued, subject to modification based on culture results. In both groups, sputum cultures were obtained after therapy. Primary end points were mortality, length of ICU stay, acquisition of resistant organisms, and cost of antimicrobial therapy.
Thirty-nine patients were randomized to the ciprofloxacin group, and 42 to the control group. Mortality, extrapulmonary infections, and the proportion of patients developing a CPIS more than 6 (implying pneumonia) at three days were not significantly different between the groups. Twenty-one percent of the ciprofloxacin group had a CPIS more than 6 at three days, compared with 23% of controls. Antibiotics were continued for more than three days in 28% of the protocol patients compared with 97% of controls (P = 0.0001). Antibiotic therapy was discontinued at three days in all 25 protocol patients with CPIS less than 6 and no evidence of extrapulmonary infection. In contrast, 24 of 25 such patients in the control group continued to receive antibiotics. Antibiotic costs, duration of ICU stay, and recovery of antibiotic resistant organisms from sputum were all significantly lower in protocol patients than in controls.
Comment by Robert Muder, MD
All infectious disease consultants have been in the frustrating position of trying to convince attending physicians that an ICU patient has a low likelihood of pneumonia, and that antimicrobial therapy should be withheld or discontinued. The response is, all too often, completely disregarded or the argument is made that one can’t be absolutely sure infection is not present, and, thus, treatment should continue. The result is overuse of antibiotics on a major scale with its attendant costs, adverse effects, and contribution to the selection of resistant organisms.
The study by Singh et al attempts to inject some rationality into clinical practice by dividing patients into low and high probability of pneumonia based on a straight-forward clinical grading system. Those patients with a lower likelihood of infection are given a defined course of empiric ciprofloxacin and re-evaluated at three days. If the evidence in favor of pneumonia is not there, or it is argued that since one cannot be 100% certain of the absence of infection, then empiric therapy is stopped. It is notable that this had no adverse effect on outcome. In fact, some important measures of outcome such as length of ICU stay, cost, and acquisition of resistant bacteria were significantly better in the protocol group than in the control group.
A key factor in the success of the protocol was that it allowed use of empiric antibiotics after identification of the infiltrate. This may have had some therapeutic benefit in treating a pneumonia early in its evolution. However, it is quite likely that many of these patients did not have pneumonia in the first place. The major benefit of the brief course of ciprofloxacin might well have been to provide enough reassurance to clinicians to prevent the unnecessary administration of additional agents. Thus, the study does not, and was not designed to, answer the question of which ICU patient does or does not have pneumonia. Instead, it successfully identifies patients at low risk in whom antibiotics can safely be discontinued after three days, with substantial clinical and economic benefit.
Reference
1. Pugin JR, et al. Diagnosis of ventilator-associated pneumonia by bacterologic analysis of bronchoscopic and non-bronchoscopic "blind" brocheoalvelar lavage fluid. Am Rev Respir Dis 1991;143:1121-1129.
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