Hospitalized lithium overdose cases reported to the California Poison Control System

Abstract

Background: Lithium overdose primarily results in neurologic toxicity; however, cardiac effects have also been reported. Our aim was to describe a large cohort of hospitalized lithium overdose patients. Specifically we were interested in reported cardiac complications, frequency of hemodialysis (HD), and mortality.

Methods: This is a retrospective, observational case series of admitted isolated lithium exposure cases reported to the California Poison Control System (CPCS) from 2003 through 2007. Reported lithium exposure cases were identified by a search of our CPCS database. Only those cases resulting in hospital admission were included in this study. Cases with concomitant toxic exposures were excluded. Primary outcome variables were reported cardiac complications (defined as bradycardia with a heart rate < or =50 bpm, atrioventricular (AV) block, ventricular tachycardia, and ventricular fibrillation), administration of cardiovascular intervention (resuscitation, vasopressor medications, or cardiac pacing), and death.

Results: In the 5-year-study period 629 lithium cases were reported to the CPCS and 502 hospitalized cases were included in this study. There were 44 [8.8%; 95% confidence intervals (CI) 6.3, 11.2] cases of acute lithium exposure, 124 (24.7%; 95% CI 20.9, 28.5) cases of acute on chronic (AC) overdose, and 282 (56.2%; 95% CI 51.8, 60.5) cases of chronic overdose. Sixty-nine patients received hemodialysis. This includes 6 (13.6%) acute, 12 (9.7%) AC, and 45 (16.0%) chronic cases. There were four deaths (0.8%, 95% CI 0.2, 1.6). Cardiac complications were reported in 29 cases (5.7%, 95% CI 3.7, 7.7%) with 18 of these cases (18/29; 62%) being isolated bradycardias (without hypotension). Only seven patients with reported cardiac complication (7/29; 24.1%; 95% CI = 8.6, 39.7) required cardiovascular intervention and all of these were cases of chronic lithium toxicity. Two bradycardic arrests occurred in chronic lithium exposure cases, including one who died.

Conclusion: In this cohort of hospitalized lithium exposure patients, death was rare. Reported cardiac complications were unusual with instances requiring cardiovascular intervention occurring only in cases of chronic lithium overdose. The majority of lithium toxicity cases were managed without HD.