BackgroundStudies evaluating nicotine replacement therapy (NRT) to prevent nicotine withdrawal symptoms in ICU patients have yielded conflicting results. We performed a randomised controlled double-blind pilot study to assess the safety and efficacy of NRT in critically ill patients. Mechanically ventilated patients admitted to two medical–surgical intensive care units and smoking more than 10 cigarettes per day before ICU admission were enrolled in this study. Participants were randomised to transdermal NRT (14 or 21 mg per day) or placebo until ICU discharge or day 30. Smoking status was confirmed by the biomarkers serum cotinine and urinary NNAL. The primary endpoint was 30-day mortality. Among secondary endpoints and post hoc endpoints, 90-day mortality, safety, time spent without delirium, sedation and coma, and patient destination at day 30 were addressed.ResultsWe enrolled 47 patients. No differences were found between NRT and control group patients concerning 30-day mortality (9.5 vs. 7.7%, p = 0.84) and 90-day mortality (14.3 vs. 19.2%, p = 0.67). The number of serious adverse events was comparable between groups (NRT: 4, control: 11, p = 0.13). At day 20, average time alive without delirium, sedation and coma was 16.6 days among NRT patients versus 12.6 days among control patients (p = 0.03). At day 30, more NRT group patients were discharged from the ICU or hospital compared with controls (p = 0.03).ConclusionsNRT did not affect mortality or the number of (serious) adverse events compared with placebo. Time alive without delirium, sedation and coma at day 20 in NRT patients was longer than in control patients. An adequately powered randomised controlled trial to further study safety and efficacy of NRT in ICU patients seems feasible and is warranted.Trial registration ClinicalTrials.gov, number NCT01362959, registered 1 June 2011Electronic supplementary materialThe online version of this article (10.1186/s13613-018-0399-1) contains supplementary material, which is available to authorized users.