D. Jordan et al., ESMOLOL HYDROCHLORIDE, SODIUM-NITROPRUSSIDE, AND ISOFLURANE DIFFER INTHEIR ABILITY TO ALTER PERIPHERAL SYMPATHETIC RESPONSES, Anesthesia and analgesia, 77(2), 1993, pp. 281-290
To demonstrate that esmolol, sodium nitroprusside, and isoflurane diff
er in their abilities to alter adrenal medullary blood flow and other
peripheral sympathetic responses to hypotension, 16 mongrel dogs anest
hetized with pentobarbital were allocated randomly to one of four test
groups and given two hypotensive stimuli, separated by 1 h, to a mean
arterial blood pressure of 60 mm Hg for 10 min. The first stimulus, i
nduced by blood loss into a pressurized bottle system, constituted the
control for each animal. The second hypotensive stimulus was created
by either repeat blood loss (Group 1), esmolol infusion (Group 2), sod
ium nitroprusside infusion (Group 3), or isoflurane administration (Gr
oup 4). Before and 10 min into hypotension, the variables of abdominal
organ blood flow, adrenal medullary blood flow, arterial norepinephri
ne and epinephrine concentrations were measured. In the control animal
s (Group 1), comparable decreases in abdominal organ blood flow and si
milar increases in adrenal medullary blood flow, norepinephrine, and e
pinephrine were elicited by the first and second hypotensive stimulus.
Esmolol-induced hypotension (Group 2) abolished the increase in adren
al medullary blood flow and attenuated the increase in epinephrine by
65% (P < 0.03). The decrease in abdominal organ blood flow and the inc
rease in norepinephrine were similar to that observed during baseline
hemorrhagic hypotension. In contrast, sodium nitroprusside-induced hyp
otension (Group 3) abolished abdominal organ vasoconstriction whereas
the increases in adrenal medullary blood flow, norepinephrine, and epi
nephrine were comparable to baseline hemorrhagic hypotension. In fact,
abdominal organ blood flow increased 2.5-fold (P < 0.001) during hypo
tension with SNP. Isoflurane 2%, 1.54 minimum alveolar anesthesia conc
entration (Group 4), abolished the increases in adrenal medullary bloo
d flow, norepinephrine, and epinephrine observed during baseline hemor
rhagic hypotension and attenuated the decrease in abdominal organ bloo
d flow by 70% (P < 0.001). These data demonstrate that esmolol, sodium
nitroprusside, and isoflurane differ radically in their ability to al
ter or blunt peripheral sympathetic responses to hypotension, and sugg
est that isoflurane is the drug most effective in blunting multiple re
sponses of the peripheral sympathetic system.