Cardiovascular effects of 6% hetastarch and lactated Ringer's solution during spinal anesthesia

Background and Objectives. The purpose of this prospective, randomized, dou ble-blinded study was to compare the hemodynamic effects of 6% hetastarch w ith lactated Ringer's solution and to determine the main reasons for hemody namic impairment following spinal anesthesia in elderly patients undergoing emergent hip surgery. Methods. After receiving institutional approval and informed consent, we enrolled 24 ASA physical status III patients for this study. Hemodynamics were recorded with pulmonary artery and arterial cathet ers and an electrocardiogram. Following fluid administration with either 50 0 mL. 6% hetastarch (group H) or 1500 mL lactated Ringer's solution (group R), spinal anesthesia was administered with 3.0 mi, 0.5% bupivacaine (isoba ric). Hemodynamic measurements were recorded prior to fluid administration, before spinal anesthesia, and 10, 20, and 30 minutes following spinal anes thesia and reported as relative changes relating to baseline. Results. Alth ough the hemodynamic measurements after spinal anesthesia remained stable i n group 11 throughout the observation period, blood pressure, central venou s pressure, pulmonary artery (PA) wedge pressure and systemic vascular resi stance deceased significantly in group R (blood pressure: -7 +/- 10 vs -14 +/- 8% 30 minutes after spinal anesthesia, P < .05 to group R; central veno us pressure: 51 +/- 106 vs -26 +/- 27% 10 minutes, 63 +/- 89 vs -36 +/- 30% 20 minutes and 73 +/- 112 vs -33 +/- 29% 30 minutes after spinal anesthesi a, P < .01 to group R; PA wedge pressure: 40 +/- 37 vs -5 +/- 40% 10 minute s, 40 +/- 35 vs -23 +/- 32% 20 minutes and 38 +/- 36 vs -23 +/- 32% 30 minu tes after spinal anesthesia, P < .01 to group R; systemic vascular resistan ce: -10 +/- 16 vs -18 +/- 7% 20 minutes and -10 +/- 15 vs -19 +/- 12% 30 mi nutes after spinal anesthesia, P < .05 to group R). Conclusions. Six percen t hetastarch minimizes the hemodynamic responses during spinal anesthesia i n elderly patients undergoing emergent hip surgery. In this study populatio n, spinal anesthesia-induced hemodynamic impairment is caused by decreases in cardiac filling pressures and systemic vascular resistance.