Adverse effects of increased succinylcholine dose following d-tubocurarine pretreatment.

Changes in serum potassium (K+) and serum creatine phosphokinase (CPK), incidence of heart rate slowing, junctional rhythm, and postoperative myalgia were determined in patients receiving intravenously (I.V.) either 1 mg./kg. of succinylcholine (SCh) or 0.04 mg./kg. of d-tubocurarine (dTc) as pretreatment, followed 3 minutes later by 2 mg./kg. of SCh. The incidence of heart rate slowing (15 percent less than the control heart rate), junctional rhythm, and postoperative myalgia was less in pretreated patients. Serum CPK and serum K+ elevations were similar with or without pretreatment. Increasing SCh dosage with pretreatment apparently did not accentuate adverse effects, and in some instances was associated with fewer such effects, than after lower-dose SCh injections without pretreatment.