PREVENTION OF SPINAL ANESTHESIA-INDUCED HYPOTENSION IN THE ELDERLY - IM METHOXAMINE OR COMBINED HETASTARCH AND CRYSTALLOID

We have compared two methods of reducing hypotension during spinal ana esthesia in elderly patients, 6% hetastarch and crystalloid or methoxa mine 10 mg i.m., in terms of haemodynamic stability and requirements f or additional vasopressors. Sixty-two patients (aged 60-97 yr) undergo ing surgical fixation of fractured neck of femur were allocated random ly to receive 6% hetastarch (Hespan) 500 ml followed by Hartmann's sol ution 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 anaesth esia with 0.5% hyperbaric bupivacaine 2.25-3.0 ml. Arterial pressure w as measured noninvasively by an oscillotonometer at 2-min intervals fr om 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 mea n arterial pressure (MAP). Patient data, sensory level and blood loss were similar in the two groups. SAP and MAP increased initially from b aseline until induction of spinal anaesthesia and then decreased for 3 0 min in both groups, but remained higher in group MX (P < 0.05). Hear t rate (HR) decreased from baseline in group MX (P < 0.05) and was les s than in group HS at all times from 2 to 60 min (P < 0.01). The incid ence 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 gro up 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 interv als 3.0-9.6) vs 8.9 (5.6-12.2) mg) and time to onset of hypotension (2 0.7 (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 m in before induction of spinal anaesthesia in normovolaemic elderly pat ients, reduced subsequent SAP and MAP hypotension, HR and requirements for rescue vasopressor therapy compared with a combination of 6% heta starch 500 mi and crystalloid 500 ml. The previously reported benefit of such volume administration may not extend to the elderly.