BACKGROUND Loop diuretics, when given as intermittent bolus injections in acutely decompensated heart failure, may cause fluctuations in intravascular volume, increased toxicity and development of tolerance. Continuous infusion has been proposed to avoid these complications and result in greater diuresis, hopefully leading to faster symptom resolution, decrease in morbidity and possibly, mortality. OBJECTIVES To compare the effects and adverse effects of continuous intravenous infusion of loop diuretics with those of bolus intravenous administration among patients with congestive heart failure Class III-IV. SEARCH STRATEGY We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2003), MEDLINE (1966 to 2003), EMBASE (1980 to 2003) and the HERDIN database. We also contacted pharmaceutical companies. SELECTION CRITERIA Randomized controlled trials comparing the efficacy of continuous intravenous infusion versus bolus intravenous administration of loop diuretics in congestive heart failure were included DATA COLLECTION AND ANALYSIS Two reviewers independently assessed study eligibility, methodological quality and did data extraction. Included studies were assessed for validity. Authors were contacted when feasible. Adverse effects information was collected from the trials. MAIN RESULTS Eight trials involving 254 patients were included. In seven studies which reported on urine output, the output (as measured in cc/24 hours) was noted to be greater in patients given continuous infusion with a weighted mean difference (WMD) of 271 cc/24 hour (95%CI 93.1 to 449; p<0.01). Electrolyte disturbances (hypokalemia, hypomagnesemia) were not significantly different in the two treatment groups with a relative risk (RR) of 1.47 (95%CI 0.52 to 4.15; p=0.5). Less adverse effects (tinnitus and hearing loss) were noted when continuous infusion was given, RR 0.06 (95%CI 0.01 to 0.44; p=0.005). Based on a single study, the duration of hospital stay was significantly shortened by 3.1days with continuous infusion WMD -3.1 (95%CI -4.06 to -2.20; p<0.0001) while cardiac mortality was not significantly different in the two treatment groups, RR 0.47 (95% CI 0.33 to 0.69; p<0.0001). Based on two studies, all cause mortality was not significantly different in the two treatment groups, RR 0.52 (95%CI 0.38 to 0.71; p<0.0001). REVIEWER'S CONCLUSIONS Currently available data are insufficient to confidently assess the merits of the two methods of giving intravenous diuretics. Based on small and relatively heterogenous studies, this review showed greater diuresis and a better safety profile when loop diuretics were given as continuous infusion. The existing data still does not allow definitive recommendations for clinical practice and larger studies should be done to more adequately settle this issue.