Hemodynamic response to low-dose epinephrine infusion during hypotensive epidural anesthesia for total hip replacement.

The hemodynamic response to reduction in blood pressure after epidural anesthesia in elderly patients is poorly defined. Therefore, hemodynamic measurements using radial artery and thermodilution pulmonary artery catheters were performed in 85 patients undergoing total hip replacement in whom blood pressure was allowed to decrease in order to minimize blood loss. Measurements were made in the lateral position prior to and after induction of epidural anesthesia to T4 or above when mean arterial pressure (MAP) had fallen to 50-55 mmHg. Four non-randomized groups of patients were identified: those requiring zero, less than 1 microgram/minute, 1-2 micrograms/minute or 2-5 micrograms/minute, respectively, of intravenous epinephrine to maintain MAP at 50-55 mmHg. In patients receiving no epinephrine, MAP, heart rate (HR), stroke volume (SV), cardiac index (CI), pulmonary artery diastolic pressure (PAD), left ventricular stroke work index (LVSWI) and systemic vascular resistance (SVR) fell significantly from baseline. Low-dose epinephrine infusions modified this response by increasing SV and CI and reducing SVR, but had little consistent effect on PAD, HR and LVSWI. Increases in SV and CI were significantly related to the dose of epinephrine administered. Low-dose intravenous epinephrine infusions preserve cardiac output during hypotensive epidural anesthesia in elderly patients.