Systemic lithium reabsorption from lithium-chloride-coated heat and moisture exchangers

Abstract

Objective: To evaluate possible reabsorption and systemic effects of lithium released by lithium-chloride-coated heat and moisture exchangers (HMEs) during prolonged mechanical ventilation. Design: Prospective study, including all patients mechanically ventilated for 5-30 days. Setting: A 7 bed general-traumatological ICU in a University Hospital. Patients: 27 consecutive ICU patients, admitted following trauma, neurosurgery and respiratory insufficiency, mechanically ventilated for at least 5 days, with a lithium coated hygroscopic HME in the circuit. Measurements and results: Serum lithium levels were measured daily, with a standard laboratory spectrophotometric method, from admission to discharge from the ICU, and showed a reabsorption of lithium in all the patients; in the adults, levels were 5 to 15 times lower than therapeutic range, while in a child therapeutic and even toxic levels were reached. Conclusions: LiCl coat enhances HMEs' performance greatly, but reabsorption and systemic action must be considered. In adults, serum lithium levels were lower than the therapeutic range, but lithium is effective at low concentrations and it has a narrow therapeutic range; moreover, toxicity can be observed within this range too. In children, the risk of toxicity is much greater. When lithium coated HMEs are used, the risk/benefit ratio between good performance and systemic reabsorption must be evaluated carefully. © 1995 Springer-Verlag.