Prevention of spinal anaesthesia-induced hypotension in the elderly: i.m. methoxamine or combined hetastarch and crystalloid |
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Authors: | Buggy D J; Power C K; Meeke R; O'Callaghan S; Moran C; O'Brien G T |
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Institution: | Department of Anaesthesia, Cork University Hospital, Wilton, Cork City, Ireland |
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Abstract: | We have compared two methods of reducing hypotension during spinal
anaesthesia in elderly patients, 6% hetastarch and crystalloid or
methoxamine 10 mg i.m., in terms of haemodynamic stability and requirements
for additional vasopressors. Sixty-two patients (aged 60- 97 yr) undergoing
surgical fixation of fractured neck of femur were allocated randomly to
receive 6% hetastarch (Hespan) 500 ml followed by Hartmann's solution 500
ml (group HS, n = 32) or a bolus injection of methoxamine 10 mg i.m. (group
MX, n = 30), 10 min before induction of spinal anaesthesia with 0.5%
hyperbaric bupivacaine 2.25-3.0 ml. Arterial pressure was measured
non-invasively by an oscillotonometer at 2-min intervals from 0 to 40 min
and at 5-min intervals thereafter. Methoxamine 2 mg i.v. was given if
systolic arterial pressure (SAP) decreased to < 100 mm Hg. Hypotension
was defined as a 25% decrease from baseline SAP or mean arterial pressure
(MAP). Patient data, sensory level and blood loss were similar in the two
groups. SAP and MAP increased initially from baseline until induction of
spinal anaesthesia and then decreased for 30 min in both groups, but
remained higher in group MX (P < 0.05). Heart rate (HR) decreased from
baseline in group MX (P < 0.05) and was less than in group HS at all
times from 2 to 60 min (P < 0.01). The incidence of SAP hypotension (47%
vs 75%; P = 0.03, odds ratio (OR) = 3.43) and MAP hypotension (47% vs 67%;
P = 0.09, OR = 2.51) was less in group MX than in group HS. Requirements
for rescue methoxamine i.v. (27% vs 53%, P = 0.04, OR = 3.11) was less in
group MX than in group HS but the dose of rescue methoxamine given (mean
6.3 (95% confidence intervals 3.0-9.6) vs 8.9 (5.6-12.2) mg) and time to
onset of hypotension (20.7 (14.5-26.7) vs 17.3 (11.4-23.1) min) were
similar in groups MX and HS, respectively. We conclude that methoxamine 10
mg i.m., given 10 min before induction of spinal anaesthesia in
normovolaemic elderly patients, reduced subsequent SAP and MAP hypotension,
HR and requirements for rescue vasopressor therapy compared with a
combination of 6% hetastarch 500 ml and crystalloid 500 ml. The previously
reported benefit of such volume administration may not extend to the
elderly.
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