A COMPARISON OF DESFLURANE AND ISOFLURANE IN PROLONGED SURGERY

Study Objective: To compare desflurane with isoflurane in several anes thetic situations. Design: Intubating conditions, hemodynamic response to intubation, maintenance hemodynamics, and speed of recovery from d esflurane and isoflurane anesthesia were evaluated. In addition, inter action with a muscle relaxant at low and high concentrations of the an esthetics were compared. Setting: Thomas Jefferson University Hospital . Patients: Thirty-two patients who received general anesthesia for le ngthy, mostly orthopedic procedures. Interventions: Immediately after induction with thiopental sodium, desflurane or isoflurane in nitrous oxide-oxygen was administered via face mask. Anesthesia was deepened u ntil end-tidal concentration reached 1.7 minimum alveolar concentratio n (MAC). The trachea was intubated without the aid of a muscle relaxan t. Heart rate (HR) and blood pressure (BP) were recorded before and at 1, 2, 4, 5, and 10 minutes after intubation. Noninvasive cardiac outp ut (CO) and systemic vascular resistance (SVR) were determined while t he patient was awake, immediately before intubation, and at 5 and 10 m inutes after intubation. Following intubation, the concentration of de sflurane or isoflurane was lowered until the end-tidal concentration r eached 0.65 MAC (low-MAC group), 1.25 MAC (high-MAC group), or 0 MAC ( control group). Pancuronium bromide in 0.005 mg/kg doses was administe red incrementally until T1 (first twitch of train-of-four) was depress ed more than 90%. ED50 and ED95 for pancuronium with balanced anesthes ia and for desflurane or isoflurane in low and high MACs, as well as s peed of recovery, were determined. The time to responsiveness and awak ening also was determined. Measurements and Main Results: There was no significant difference between desflurane and isoflurane in intubatin g conditions or in BP or HR response to tracheal intubation. Both anes thetics increased HR significantly during induction. BP rose with desf lurane at the preintubation point; other points showed no difference. A hyperdynamic response of increased HR and BP above 20% of baseline v alues was seen more frequently with desflurane (n = 7) than with isofl urane (n = 1). CO was elevated at all times after induction for low an d high concentrations of both drugs, while SVR decreased over the same time with no significant difference between drugs. ED50 and ED95 for pancuronium were similar under desflurane and isoflurane at both low a nd high MAC, but they were significantly lower than under balanced ane sthesia. Awakening times were similar for desflurane and isoflurane. C onclusions: Desflurane is similar to isoflurane in providing anesthesi a for intubation and maintenance. Desflurane tends to increase HR and occasionally causes a hyperdynamic response during rapid deepening of anesthesia. It is very similar to isoflurane in its interaction with p ancuronium.