Changes in plasma potassium and neuromuscular blockade following suxamethonium in patients pre-treated with terbutaline.

Plasma potassium, heart rate, systolic and diastolic blood pressure were measured in adult surgical patients pre-treated with either terbutaline 1.25 mg (n = 10) or normal saline (n = 10) prior to and during general anaesthesia which included suxamethonium 1 mg kg-1. Neuromuscular blockade was then measured using a train-of-four technique. Plasma potassium was significantly lower before and during general anaesthesia in those patients who had received terbutaline but the rise following suxamethonium (measured at 1, 3, 5, 7, 10, 12, 15, 30 and 180 min after suxamethonium) was similar in both groups. Heart rate increased significantly in the treatment group both over time and compared to the control group. Onset time to maximum neuromuscular blockade and duration of blockade was shorter in the terbutaline-treated group.