Anesthesiology
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Comparative Study
Effect of an intubating dose of succinylcholine and atracurium on the diaphragm and the adductor pollicis muscle in humans.
This study compares the neuromuscular blocking effect of succinylcholine (0.8 mg . kg-1) and atracurium (0.6 mg.kg-1) on the diaphragm (D) and the adductor pollicis (AP) in 20 patients anesthetized with nitrous oxide, oxygen, and fentanyl. The diaphragm was monitored by measuring transdiaphragmatic pressure following bilateral phrenic nerve stimulation. After succinylcholine, the time from injection of succinylcholine to maximum depression of the single twitch response (onset time) was of 50 +/- 11 s (+/- SD) for D compared to 80 +/- 24 s for AP (P less than 0.001). ⋯ The T25 was achieved after 38 +/- 7 min for D compared to 63 +/- 13 min for AP (P less than 0.001). The TH of D returned to T100 after 60 +/- 12 min compared to 87 +/- 17 min for AP (P less than 0.01). The train-of-four ratio returned to 1 after 64 +/- 15 min for D compared to 99 +/- 21 min for AP (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Studies in fetal lambs suggested that the minimum alveolar concentration (MAC) in preterm neonates may be less than that in full-term neonates and older infants. To determine the MAC of isoflurane in preterm neonates, 20 patients less than 32 weeks gestation at birth and 16 patients 32-37 weeks gestation at birth, all less than 1 month post-natal age, were studied. Following tracheal intubation, the neonates were anesthetized with a predetermined end-tidal concentration of isoflurane in oxygen and air. ⋯ MAC (mean +/- SD) of isoflurane in preterm neonates less than 32 weeks gestation was 1.28 +/- 0.17%, and MAC in neonates 32-37 weeks gestation was 1.41 +/- 0.18% (P less than 0.05). Although heart rate did not decrease significantly in either group during the study, systolic arterial pressure decreased between 20 and 30% below awake values both before and after skin incision in both age groups (P less than 0.01). We conclude that the MAC of isoflurane in preterm neonates less than 32 weeks gestation is significantly less than that in preterm neonates 32-37 weeks gestation, and that systolic arterial pressure decreases to a similar extent at approximately 1 MAC isoflurane in both age groups.