Background and Objectives Although numerous reports of the use of spinal anesthesia have appeared in recent literature, little information is available on the duration of anesthesia provided by standard doses of the commonly used drugs: lidocaine with epinephrine, tetracaine, or tetracaine with epinephrine. The authors evaluated the duration of spinal anesthesia using standard doses of local anesthetics and an objective endpoint of motor recovery in infants less than 1 year of age.

Methods After reviewing historic literature to select doses, the duration of hyperbaric spinal anesthesia in 100 infants from 1-month to 12-months of age undergoing surgery below the diaphragm was evaluated. Spinal anesthesia was induced, cutaneous level of anesthesia determined by the infant’s response to tetanic stimulation with a peripheral nerve stimulator, and time from injection to flexion of hip in response to stimulus was recorded.

Results Lidocaine 3 mg/kg with epinephrine lasted 56 ± 2.5 minutes, while tetracaine 0.4 mg/kg lasted 86 ± 4 minutes and tetracaine 0.4 mg/kg with epinephrine lasted 128 ± 3 minutes.

Conclusions The three subarachnoid techniques produced varying levels of duration of motor block. The authors recommend lidocaine 3 mg/kg with epinephrine for very brief procedures, tetracaine 0.4 mg/kg for procedures with a potential duration of 1 hour or less, and tetracaine 0.4 mg/kg with epinephrine for procedures estimated to last 90 minutes in infants less than 1 year of age.