Changes in Heart Rate and Rhythm after Intramuscular Succinylcholine with or without Atropine in Anesthetized Children

The effects of intramuscular injections of Succinylcholine with or without atropine on heart rate and rhythm were studied in 50 unpremedicated children 6–18 months of age. All had anesthesia induced with N2O-O2 and halothane 2% by face mask. Sixty seconds later, one of four study drugs or drug combinations was injected into the deltoid muscle of patients in groups 1–4. Following injection, halothane concentration was reduced to 1%, and ventilation was controlled. Patients given atropine only (0.02 mg/kg), succinylcholine only (4 mg/kg), or a combination of both (4 mg/kg Succinylcholine plus 0.02 mg/kg atropine) showed transient increases in heart rate to 106 ± 7.5%, 113 ± 11.8%, and 109 ± 20.1% (mean ± so) of control, followed by a decrease to 78 ± 6.7%, 79 ± 9.4%, and 80 ± 10.5%, respectively, in 2–3 min after injection. Patients given a combination of Succinylcholine (4 mg/kg) plus a higher dose of atropine (0.03 mg/kg) also had a transient increase in heart rate to 107 ± 7.5%, followed by a decrease to 82 ± 11.8% 2 min after injection. However, this group differed from the other three groups in presenting a second, prolonged increase in heart rate to 115 ± 9.0% of preinjection levels. Patients in group 5 (controls) received no injections. Their heart rate decreased to 76 ± 10.78% of preinduction level within 90 sec of induction, and remained unchanged thereafter. We conclude that Succinylcholine (4 mg/kg) can be used intramuscularly with or without atropine (0.02 mg/kg) in lightly anesthetized young children without producing severe bradycardia. If an increase in heart rate is desired, a higher dose of atropine (0.03 mg/kg) is recommended.