Hemodynamic stability in an optimized propofol-remifentanil based anesthesia for ophthalmic surgery

Abstract

Background and Goal of the Study: A deep level of anesthesia is often required in ophthalmic surgery to obtain optimal surgical conditions, which may induce significant cardiovascular impairment and compromise tissue oxygenation. We investigated the hemodynamic stability and tissue oxygenation in a balanced general anesthesia with remifentanil, low-dose propofol, norepinephrine and goal-directed fluid administration in patients undergoing ophthalmic surgery. Material and Methods: 40 consecutive patients were included after informed consent was obtained. Anesthesia was induced with 1-3 mg kg-1 propofol, 1 µg kg-1 remifentanil, 0.1 mg kg-1 cisatracurium and an additional bolus of norepinephrine 10 µg, if required. Anesthesia was maintained with 4 mg kg-1 min-1 propofol, 0.25 µg kg-1 min-1 remifentanil and 0.05 µg kg-1 min-1 norepinephrine if required and further titrated to a MAP above 80% of baseline. Propofol or remifentanil infusion was increased upon the discretion of the anesthetist and targeted to a BIS value between 40 - 60. Voluven® 500ml was administered if the plethysmographic wave variation was > 10%. Tissue oxygen saturation (StO2) was measured by near-infrared spectroscopy using the Inspectra device (Model 650, Hutchinson Technology, USA) at the left thenar eminescence. Hemodynamics (cardiac index (CI), mean arterial pressure (MAP) and heart rate (HR)) were measured non-invasively (Nexfin, BMEye, Amsterdam). Results and Discussion: Mean (SD) StO2 increased from 83 (6) % before induction to 86 (4) % 20 minutes after induction of anesthesia (p< 0.05) and remained stable throughout the procedure. Cardiac index dropped from 3.0 (0.7) to 2.1 (0.4) L min-1 after 20 minutes (p< 0.05). Furthermore MAP decreased from 109 (16) to 83 (14) mm Hg and HR from 73 (12) to 54 (8) bpm (both p< 0.05). 14/40 patients received a 500 ml Voluven bolus. The median (range) norepinephrine administration rate was 0.05 (0.0 - 0.10) µg kg-1 min-1. The overall median (IQR) BIS value from induction of anesthesia to the end of the procedure was stable in all patients and was 44 (40 - 51), while 3/40 patients required additional propofol or remifentanil. Conclusion: This balanced protocol based on remifentanil, low-dose propofol, norepinephrine and goal-directed fluid therapy preserves StO2 while other hemodynamic variables are within a clinically acceptable range, suggesting this protocol to be feasible for use in anesthesia for ophthalmic surgery.