A comparative study between a calcium channel blocker (Nicardipine) and a combined alpha-beta-blocker (Labetalol) for the control of emergence hypertension during craniotomy for tumor surgery.

We compared the efficacy of the combination of enalaprilat/labetalol with that of enalaprilat/nicardipine to prevent emergence postcraniotomy hypertension. A prospective, randomized open labeled clinical trial was designed to compare the incidence of breakthrough hypertension (systolic blood pressure [SBP] > 140 mm Hg) and adverse effects (hypotension, tachycardia, and bradycardia) between the two drug combinations. Secondarily, the effects of the drugs on SBP, mean blood pressure, and diastolic blood pressure were evaluated over the course of the study. Forty-two patients received enalaprilat 1.25 mg IV at dural closure followed by either multidose nicardipine 2 mg IV or labetalol 5 mg IV to maintain the SBP below 140 mm Hg. SBP was similarly controlled in both groups. There was a marginally smaller incidence of failures and adverse effects with labetalol. Blood pressure profiles were similar for both groups.

Propofol versus midazolam for monitored sedation: a comparison of intraoperative and recovery parameters.

STUDY OBJECTIVE: To compare intraoperative and recovery parameters in patients who received either propofol infusion (PI), propofol bolus (PB), or midazolam bolus (MZ) for sedation. DESIGN: Randomized clinical study. SETTING: Medical/surgical patients in a specialized hospital. PATIENTS: Ninety patients, aged 18 to 85 years, scheduled for central venous access for chemotherapy and/or total parenteral nutrition. INTERVENTIONS: In 30 patients, sedation was induced with MZ 0.02 mg/kg intravenously (i.v.), repeated every 2 to 3 minutes to achieve a sedation level of 3 (eyes closed, responds to verbal stimulus) (SL3). Maintenance was with MZ 0.005 mg/kg i.v. repeated as necessary to maintain SL3. In both propofol groups (30 patients each), induction of sedation was with a bolus of propofol 0.75 to 1.0 mg/kg i.v. Maintenance in the PB group was with propofol 0.25 mg/kg IV, repeated as necessary to maintain SL3. Maintenance in the PI group was with propofol 2 to 4 mg/kg/hr or 33 to 66 micrograms/kg/min to maintain SL3. MEASUREMENTS AND MAIN RESULTS: Blood pressure, heart rate, respiratory rate, oxygen saturation, and sedation level were monitored each minute for 5 minutes and then at 5-minute intervals during the procedure. A right atrial blood sample was taken for pH and partial pressure of carbon dioxide at maximum sedation. Adequate sedation was achieved in all three groups. The time to reach SL3 was significantly shorter in the PB group than in the PI and MZ groups (p < 0.05 and p < 0.01, respectively). Cardiovascular and respiratory parameters were remarkably stable. Immediate recovery, as judged by spontaneous eye opening, response to commands, and ability to state date of birth, was significantly shorter in both the PB and PI groups than in the MZ group (p < 0.0001). Intermediate recovery, as measured by sedation score at recovery entry, Aldrete score, and time to standing, was slower in the MZ group (p < 0.05 for the MZ group vs. the PB and PI groups for sedation score and Aldrete score; p < 0.05 for the MZ group vs. the PI group in time to standing). Psychomotor recovery, judged by digit symbol substitution tests, was significantly faster in the PB and PI groups (p < 0.05 vs. the MZ group). Amnesia, measured by picture recall, was significantly greater in the MZ group than in the PI and PB groups (p < 0.05). Mood changes were measured on a visual analog scale. All groups showed improvement. Nausea, headache, dizziness, blurred vision, appetite, tension, pain, depression, drowsiness, and ability to concentrate were evaluated in the preoperative and postoperative periods. The frequency did not differ significantly between groups due to confounding factors such as postoperative chemotherapy and premedicant drugs. CONCLUSION: The PI, PB, and MZ groups all gave excellent sedation for patients undergoing surgical procedures with local anesthesia. Amnesia was greatest with midazolam, and recovery was more rapid with propofol.

Anesthesia for diagnostic and therapeutic procedures in pediatric outpatients.

Appropriate sedation of pediatric oncology patients during painful diagnostic and therapeutic procedures is a recognized problem. At the Memorial Sloan-Kettering Cancer Center the pediatric oncologists and anesthesiologists have developed a cooperative program that has provided safe and effective sedation of outpatients. The experience with 100 consecutive outpatients is reported. Patients ranged from 3 months to 17 years of age. Procedures included lumbar puncture and/or intrathecal chemotherapy, multiple bone marrow aspirations, bone marrow biopsies, and removal of indwelling central vein catheters. Monitoring of patients during the procedures as well as various pharmacologic techniques to provide adequate working conditions are described.

Inhibition by enflurane and methoxyflurane of postdrive hyperpolarization in canine Purkinje fibers.

When a pacemaker cell is driven with a train of stimuli at a rate faster than its own, the termination of the drive is followed by a transient hyperpolarization, due to the activity of an electrogenic Na+-K+ pump. In this study, the effect of the halogenated ethers, enflurane and methoxyflurane, on postdrive hyperpolarization (PDH) was determined in cardiac Purkinje fibers. The fibers were removed from freshly excised canine hearts and superfused with a Tyrode's solution (containing 2.7 or 3.5 mM K+). The preparation was paced at 0.2 Hz before and after drives, and at 2 Hz during drives. Under control conditions, drives of 2 min produced a PDH of 5.5 +/- 0.2 mV. Enflurane (1.5-5%) significantly reduced the PDH. At 4 to 5%, enflurane reduced the PDH to a mean value of 42% of the control. Methoxyflurane was more potent than enflurane in affecting the PDH. At 0.5 to 0.75%, methoxyflurane reduced the PDH to 5% of the control. At higher (1-1.5%) concentrations of methoxyflurane, the PDH was converted to a depolarization, which varied between 0.5 and 8.0 mV. The PDH was restored to control levels within 10 to 20 min after washout of either anesthetic agent. Methoxyflurane (0.5 or 1%) enhanced the automaticity of spontaneously firing cells (2.35 mM K+ Tyrode's solution used). This positive chronotropic action coincided with a depolarization of 2 to 8 mV. Enflurane, at concentrations of 3 to 5%, gave similar results. On the action potential, methoxyflurane, at 1%, reduced the amplitude and duration (measured at 50% repolarization) of the plateau, and also the maximal upstroke velocity (+Vmax) of the rising phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Enflurane depression of myocardial slow action potentials.

Effects of enflurane on myocardial electrophysiologic and contractile properties were examined by simultaneous measurement of action potentials (APs) and contractions in guinea-pig papillary muscle. Enflurane was administered in 1 to 6% concentrations in 5% CO2-95% O2 bubbled through the standard Tyrode's perfusing solution. After studying normal APs, slow APs were induced with 5 to 30 x 10(-8) M isoproterenol and/or 1 to 2 mM theophylline in partially depolarized muscles (typically -40 mV in 26 mM K+ media). AP characteristics and contractions measured during each enflurane application were analyzed. The maximum rate of rise (+Vmax) and amplitude of the normal AP was not depressed, although duration decreased in greater than or equal to 3% enflurane. In contrast, slow AP + Vmax declined significantly (P less than .05) to 90, 80 and 74% of control in enflurane concentrations of 2, 3 and 4%, respectively. Decrease in slow AP duration was significant only in 5 to 6% enflurane. In 1% enflurane, contractions declined to steady-state levels of 75 (fast AP) and 79% (slow AP) of control and fell to 20 (fast AP) and 35% (slow AP) in 4% enflurane. Enflurane concentrations of 2% and greater inhibit slow (Na+-Ca++) channels which mediate slow APs. This effect may be in part responsible for the negative inotropic effect of enflurane.

Sympathetic nervous system tonicity and post-coronary artery bypass hypertension.

To elucidate the pathogenesis of hypertension following coronary bypass surgery, blood pressure and plasma catecholamine concentration were measured in 28 patients with coronary artery disease who were undergoing myocardial revascularization procedures. Measurements were obtained on arrival in the operating room and 1 and 4 h after surgery. One hour after surgery, plasma norepinephrine (NE) increased significantly by 495 +/- 108 pg/ml (P less than 0.001) in the coronary artery disease group which developed hypertension, but the increase was not significant in the coronary artery patients who remained normotensive after surgery. However, 4 h after surgery, plasma NE increased significantly and to the same extent in both coronary artery disease groups, regardless of the change in blood pressure. Plasma epinephrine (E) also increased significantly 1 and 4 h after surgery in both groups. The observed change in plasma catecholamine concentration is direct evidence that the stress of surgery is a potent adrenergic stimulus, but the hemodynamic significance of the plasma catecholamine change remains unclear.

Anaesthetic management of phaeochromocytoma.

The incidence, mortality, physiology, clinical findings and diagnosis of phaeochromocytoma are reviewed. Treatment, after adequate medical stabilization, must be surgical because of the high incidence of malignancy. Alpha-adrenergic receptor blockade and beta-adrenergic receptor blockade in the preoperative period was discussed. Anaesthetic management of patients with phaeochromocytoma requires close monitoring. Virtually all inhalational anaesthetic agents have been used in cases of phaeochromocytoma. Recent reports have favored enflurane. The merits of neuroleptanaesthesia and the various muscle relaxants are also discussed. Most authors favour lidocaine over propranolol for management of dysrhythmias during operation. Phentolamine or sodium nitroprusside are used for hypertension during operation. Hypotension is treated by fluid replacement with nor-epinephrine if a vasopressor becomes necessary. Close monitoring is necessary in the postoperative period. Adequate urinary output is of more importance than actual blood pressure levels.