Comparative effects of lidocaine, esmolol, and nitroglycerin in modifying the hemodynamic response to laryngoscopy and intubation.

STUDY OBJECTIVE: To compare the safety and efficacy of lidocaine, esmolol, and nitroglycerin in modifying the hemodynamic response to laryngoscopy and intubation. DESIGN: Randomized, placebo-controlled, double-blind study. SETTING: University-affiliated VA medical center. PATIENTS: 40 ASA physical status I and II patients undergoing electric surgery with general endotracheal anesthesia. INTERVENTIONS: Anesthesia was induced with thiopental sodium 5 mg/kg, and intubation was facilitated with vecuronium 0.15 mg/kg. Isoflurane (0.5% to 1%) and 50% nitrous oxide in oxygen were used for maintenance of anesthesia. In addition, patients received one of the following four study drugs intravenously (i.v.) prior to laryngoscopy: Group 1 (control) = saline 5 ml; Group 2 = lidocaine 1.5 mg/kg; Group 3 = esmolol 1.4 mg/kg; Group 4 = nitroglycerin 2 micrograms/kg. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure (MAP) and heart rate (HR) were recorded every minute for 20 minutes following induction of anesthesia. Following laryngoscopy and intubation, MAP increased significantly in all four treatment groups (control 49% +/- 19%, lidocaine 55% +/- 26%, esmolol 25% +/- 11%, nitroglycerin 45% +/- 21%) compared with preinduction baseline values. In the esmolol-pretreated patients, the increase in HR was significantly lower (20% +/- 3%) compared with the nitroglycerin (37% +/- 8%), lidocaine (52% +/- 8%), and control (29% +/- 4%) groups. CONCLUSIONS: Lidocaine 1.5 mg/kg i.v. and nitroglycerin 2 micrograms/kg i.v. were ineffective in controlling the acute hemodynamic response following laryngoscopy and intubation. Esmolol 1.4 mg/kg i.v. was significantly more effective than either lidocaine or nitroglycerin in controlling the HR response to laryngoscopy and intubation (p < 0.05). Esmolol also was significantly more effective than lidocaine in minimizing the increase in MAP (25% vs. 55%).

Effect of oral clonidine and intrathecal fentanyl on tetracaine spinal block.

We studied the effect of oral clonidine and intrathecal (IT) fentanyl on the onset and duration of a hyperbaric tetracaine-induced spinal block. Forty adult males undergoing elective surgery were studied according to a randomized, double-blind, placebo-controlled protocol involving four treatment regimens: Group I, placebo per os (PO) + tetracaine 12 mg IT; Group II, placebo PO+tetracaine 12 mg IT+fentanyl 10 micrograms IT; Group III, clonidine 200 micrograms PO+tetracaine 12 mg IT; Group IV, clonidine 200 micrograms PO+tetracaine 12 mg IT+fentanyl 10 micrograms IT. Onset time to highest sensory level was 8.5 +/- 3.1, 8.2 +/- 2.3, 6.1 +/- 1.6, and 6.8 +/- 1.4 min in Groups I, II, III, and IV, respectively. The time required for sensory regression to the L1 dermatome level was 153 +/- 34, 151 +/- 51, 183 +/- 63, and 209 +/- 39 min in Groups I, II, III, and IV, respectively. Similarly, the duration of Grade III motor block was 132 +/- 37, 140 +/- 55, 160 +/- 51, and 189 +/- 52 min in Groups I, II, III, and IV, respectively. IT fentanyl 10 micrograms did not change the onset or duration of tetracaine-induced spinal block. Furthermore, there was no significant interaction between clonidine and fentanyl in Group IV. Episodes of bradycardia and hypotension were more frequent in the clonidine-treated patients (40%-50% vs 10%). We conclude that oral clonidine (200 micrograms) shortened the onset time of tetracaine's sensory block and prolonged the duration of sensory and motor block. However, clonidine premedication increased the risk of hypotension and bradycardia.

Anesthetic considerations for electroconvulsive therapy.

Electrically induced seizures have been used widely to treat psychiatric disease since their introduction in 1938. Seizure activity is the therapeutic aspect of this form of treatment, but it is accompanied by untoward physiologic consequences. Cardiovascular responses consist of generalized autonomic nervous system stimulation with initial parasympathetic outflow, followed immediately by a sympathetic response. In certain patients the sequence described may result in an initial bradycardia or even asystole, followed by tachycardia, dysrhythmia, and hypertension. The cerebrovascular system responds with a marked increase in cerebral blood flow in response to increased cerebral oxygen consumption, and dramatic elevation of intracranial pressure. General anesthesia for electroconvulsive therapy (ECT) must be administered only in locations equipped for support of the unconscious patient and treatment of complications. Intravenous access is mandatory in all patients, as is monitoring of blood pressure, and ECG, as well as pulse oximetry. Appropriate oxygen supplementation and ventilatory support are essential as they are during any procedure necessitating general anesthesia. Methohexital, 0.75 to 1.0 mg/kg intravenously, is the most frequently used agent for induction of anesthesia for ECT; muscle relaxation usually is accomplished with succinylcholine, 0.5 to 1.0 mg/kg. In patients at risk for ill effects from the tachycardia and hypertension that may accompany sympathetic nervous system response to ECT, nitroglycerin, propranolol, hydralazine, or other sympatholytic agents should be used to attenuate the potentially harmful sequelae of ECT. The efficacy of ECT requires a knowledge of anesthetic precepts, an understanding of the interaction between anesthetic drugs and seizure activity, and an awareness of the physiologic effects of ECT as well as the treatment of those effects.

One-lung anesthesia--a comparison of pulmonary gas exchange during anesthesia with ketamine or enflurane.

Twenty-four men undergoing elective pulmonary resection with a period of one-lung ventilation were studied to compare the effects of ketamine-O2 and enflurane-O2 anesthesia on arterial oxygen tension (PaO2) and intrapulmonary shunting (Qs/Qt). No statistically significant differences were demonstrated between ketamine and enflurane in mean peak Qs/Qt, 43% and 42%, respectively, or minimum PaO2 values, 169 torr and 127 torr, respectively. Stroke volume index, left ventricular stroke work index, and cardiac index were, however, significantly greater with ketamine. No emergence hallucinations were observed in either group. These findings suggest that ketamine affords no advantage over enflurane anesthesia in terms of Qs/Qt, and arterial oxygen desaturation during endobronchial anesthesia.