Enhanced cerebral blood flow autoregulation in the newborn piglet by d-tubocurarine and pancuronium but not by vecuronium

Abstract

Neuromuscular blockers may affect cerebral blood flow (CBF) regulation in the newborn. We studied the effects of d-tubocurarine (0.1 mg·kg-1, n = 8), pancuronium (0.1 and 0.4 mg·kg-1, n = 6 and 7), and vecuronium (0.1 and 0.4 mg·kg-1, n = 6 and 7) on CBF measured over the same range of mean systemic blood pressure ([BP] 15-122 mmHg) in each group of newborn pigs; controls received normal saline (n = 7). The levels of BP during hypotension and hypertension were scaled at intervals of 5 ± 1.6 mmHg and adjusted by inflating balloon-tipped catheters placed in the aorta. After saline, the low dose of pancuronium (0.1 mg·kg-1), and the two doses of vecuronium, CBF was constant over the BP range of 50-90 mmHg (r = -0.07-0.35, P > 0.20) but varied directly with BP beyond this range (τ = 0.38 - 0.60, P < 0.05). In contrast, in pigs treated with d-tubocurarine and high-dose pancuronium, CBF remained constant from 35 to 122 mmHg of BP (r = 0.14 - 0.37, P > 0.10) and changed minimally (4-12%) with BP > 105 mmHg compared to the other groups (41-59%, P < 0.01). When BP was reduced below 30 mmHg, CBF also decreased less (20-38%) in animals treated with d-tubocurarine and high dose-pancuronium than after the other treatments (58-67%, P < 0.05). CBF autoregulation was also determined in pigs treated with the ganglion blocker, hexamethonium (1 mg·kg-1, n = 6); the relation between CBF and BP in these animals was almost identical to that observed with d-tubocurarine and high-dose pancuronium. Hexamethonium, d-tubocurarine, and high-dose pancuronium but not the other treatments attenuated the baroreceptor-mediated BP response to common carotid artery occlusion. In summary, neuromuscular blocking agents with ganglion blocking activity (d-tubocurarine and high-dose pancuronium) as well as the specific ganglion blocker hexamethonium enhanced CBF autoregulation, but agents more selective for the neuromuscular junction (vecuronium and low-dose pancuronium) did not alter CBF autoregulation of the newborn pig.