THE EFFECT OF FRESH GAS-FLOW AND ANESTHETIC TECHNIQUE ON THE ABILITY TO CONTROL ACUTE HEMODYNAMIC-RESPONSES DURING SURGERY

We evaluated the effect of the fresh gas flow (FGF) rate and the anest hetic technique on the ability to control the acute hyperdynamic respo nse to a specific surgical stimulus during surgery in 90 consenting AS A physical status I-III patients undergoing lower abdominal procedures . After the administration of midazolam 2 mg IV, anesthesia was induce d in all patients with propofol 1.5 mg/kg IV and fentanyl 1 mu g/kg IV and was initially maintained with desflurane or isoflurane, 0.7 minim um alveolar anesthetic concentration, at total FGF rates of either 1 o r 3 L/min. In response to the surgical stimulation of skin incision an d retropubic dissection, an increase in mean arterial pressure (MAP) > 20% above the preincision baseline MAP value provoked a stepwise incre ase in the inspired concentration of the volatile anesthetic or the TV administration of a variable-rate infusion of esmolol. At both FGF ra tes, the acute hemodynamic response to surgical stimulation was more e fficiently treated by increasing the inspired concentration of desflur ane than isoflurane. At 1 L/min, the average time to control the incre ase in MAP was significantly shorter with desflurane (17 +/- 12 min) c ompared with isoflurane (29 +/- 16 min), with 60% of the patients in t he isoflurane group requiring rescue therapy. When an esmolol infusion was used to control the increase in MAP, supplementation with fentany l was required in 40% and 53% of patients anesthetized with desflurane and isoflurane, respectively. In conclusion, desflurane provided more rapid and reliable control of acute hemodynamic responses to surgical stimulation than isoflurane or esmolol when the volatile anesthetics were administered at low FGF rates. Implications: At low fresh gas flo w rates (1 L/min), desflurane more successfully and rapidly controlled the acute hemodynamic responses to painful surgical stimuli than isof lurane.