Objective: To study changes in kalemia caused by succinylcholine administration to patients in critical care, and the possible association of succinylcholine with clinical and analytical data, severity-of-disease classification, duration of stay in the intensive care unit (ICU) and immobility.
Patients and methods: Twenty-three patients admitted to the ICU, none of whom suffered burns, polytrauma or neuromuscular disease, and who had received 1.5 mg/kg succinylcholine on 28 occasions, usually to facilitate tracheal intubation. Kalemia was analyzed before neuromuscular relaxation and 5 and 30 min afterwards. Electrocardiographic II and V5 derivations and invasive arterial pressure were monitored in all patients. The increase in kalemia at 5 min correlated with age, sex, weight, APACHE II score, days in ICU, current and accumulated immobility, and analytical parameters such as glycemia, creatinine, GOT, bilirubinemia, pH and creatine kinase. The kalemia of these patients was compared with that of 15 patients in acceptable general state who had undergone scheduled surgery.
Results: Kalemia increased significantly from a mean baseline level of 4.2 (0.9) mEq/l to 5.5 (1.4) at 5 min and 4.6 (0.9) at 30 min in ICU patients. In the non ICU patients there were no statistically significant changes. Kalemia at 5 min was correlated with baseline (r = 0.84; p < 0.0001), days in the ICU (r = 0.39; p < 0.05) and weight (r = 0.46; p < 0.05). The mean increase in kalemia at 5 min was 0.5 mEq/l in patients who stayed less than 10 days, 1.8 mEq/l in those whose stay was from 10 to 30 days and 1.4 mEq/l in patients who stayed longer than 30 days. The percent increase in kalemia correlated directly (r = 0.7; p < 0.001) with days in the ICU and with accumulated immobility in patients whose ICU stay was less than 30 days. For ICU stays longer than 30 days the correlation was negative (r = -0.98; p = 0.03). Electrocardiographic changes were recorded in 2 patients with brief sinus bradycardia having no hemodynamic repercussions.
Conclusions: The use of succinylcholine in critically ill patients causes a brief but significant increase in kalemia, with slight and rare electrocardiographic changes. The effect varies according to the length of time spent in the ICU and the degree of immobility, with maximum increases seen when the ICU stay is between 10 and 30 days. Patient immobility may play an important pathophysiological role. The indications for use of succinylcholine in critically ill patients should be very strict, particularly during the period of greatest sensitivity.