Ketamine is a broadly used anaesthetic for analgosedation. Accumulating clinical evidence shows that ketamine causes pulmonary edema with unknown mechanisms. We measured the effects of ketamine on alveolar fluid clearance in human lung lobes ex vivo. Our results showed that intratracheal instillation of ketamine markedly decreased the reabsorption of 5% bovine serum albumin instillate. In the presence of amiloride (a specific ENaC blocker), fluid resolution was not further decreased, suggesting that ketamine could decrease amiloride-sensitive fraction of AFC associated with ENaC. Moreover, we measured the regulation of amiloride-sensitive currents by ketamine in A549 cells using whole-cell patch clamp mode. Our results suggested that ketamine decreased amiloride-sensitive Na+ currents (ENaC activity) in a dose-dependent fashion. These data demonstrate that reduction in lung ENaC activity and lung fluid clearance following administration of ketamine may be the crucial step of the pathogenesis of resultant pulmonary edema.

A 58-year-old male was scheduled to undergo radical gastrectomy for cancer under general anesthesia. The patient developed agitation and irregular breathing after receiving a single dose of atropine (0.5 mg) to treat bradycardia immediately prior to induction of anesthesia. Within 5 min after the atropine injection, the patient became unresponsive with facial flushing and diaphoresis. When a drop in oxygen saturation was observed, a laryngeal mask airway was inserted after administering a small bolus dose of propofol (80 mg) and the patient was ventilated with 100% oxygen. Physostigmine was not administered because of the relatively low dose of atropine and the fact that his symptoms were not totally consistent with central anticholinergic syndrome (CAS). The differential diagnosis at the time also included an acute cardiovascular event and an idiosyncratic reaction to atropine. The patient fully recovered within 80 min from this highly unusual reaction to a single 0.5 mg IV dose of atropine.