Alexander T. Marr

Rocuronium Onset of Action: A Comparison with Atracurium and Vecuronium

The onset, maximal neuromuscular block, and duration of rocuronium were compared with atracurium and vecuronium during enflurane anesthesia. Sixty patients received rocuronium (80,100,120, or 160 μg/kg). Enflurane enhanced a rocuronium neuromuscular block in a dose-related manner; the ED50 was 104 ± 11 and 83 ± 7 μg/kg (SEM) during 1% and 2% enflurane anesthesia, respectively. Patients receiving atracurium (0.12 mg/kg) or vecuronium (0.02 mg/kg) were studied during 1 % enflurane anesthesia until seven in each group qualified by achieving a maximal block between 85% and 97%. These patients were matched with each other and with patients who had received rocuronium. Seven groups of three patients (rocuronium, vecuronium, and atracurium) were obtained. The average difference in maximal block was less than 2% between matched patients. The ratio of dose used to achieve a similar final block suggests potency ratios of 1,8.5, and 1.2 for rocuronium, vecuronium, and atracurium. Rocuroniums onset time (time from drug administration to 50%, 75%, and 90% of final block) was significantly faster than either of the other two muscle relaxants (P < 0.01). Time to 90% of final block was 1.35 min for rocuronium, 3.06 min for atracurium, and 3.71 min for vecuronium. Using these equipotent doses, atracurium also had a shorter time to develop neuromuscular block than vecuronium (P < 0.05). For these three intermediate duration neuromuscular blockers, speed of onset was inversely related to their potency, confirming a relationship that had been demonstrated for the long-acting drugs pancuronium, d-tubocurarine, and gallamine.

Preoxygenation in the morbidly obese: a comparison of two techniques

Morbid obesity by increasing acidity and volume of gastric contents, as well as by increasing and intragastric pressure (l), increases the risk of pulmonary aspiration of gastric contents during general anesthesia. Rapid sequence induction of anesthesia with cricoid pressure can prevent this complication. Gold et al. (2) have shown that four vital capacity breaths of 100% 0, within 30 seconds elevates PaO, in non-obese patients as effectively as 5 min of tidal breathing of 100% 0,. Morbidly obese patients with altered lung volumes and diminished compliance, may respond differently to preoxygenation (3). We therefore compared two methods of preoxygenation in morbidly obese patients undergoing rapid sequence induction and intubation.

Sevoflurane versus halothane for general anesthesia in pediatric patients: A comparative study of vital signs, induction, and emergence

STUDY OBJECTIVE To compare vital signs and the speed of induction and emergence with sevoflurane versus halothane in pediatric patients. DESIGN Prospective, randomized, open study. SETTING Thomas Jefferson University Hospital. PATIENTS 40 unpremedicated ASA Physical Status I and II children age 9 months to 16 years undergoing elective inpatient otorhinolaryngologic or orthopedic surgery. INTERVENTIONS Standardized induction of anesthesia with sevoflurane (start: 1%, maximum: 7%) or halothane (start: 0.5%, maximum: 5%) in nitrous oxide/oxygen (N2O/O2). Intubation following vecuronium and 4 minutes of controlled ventilation with 2 minimum alveolar concentration (MAC) drug in O2; 1.5 MAC drug in N2O/O2 delivered for 20 minutes; then 0.75 MAC until the end of surgery. Fentanyl 1 mcg/kg was administered 15 minutes before the anticipated end of surgery, at which time anesthetics were stopped and mechanical ventilation continued until eye opening (emergence). MEASUREMENTS AND MAIN RESULTS Blood pressure, heart rate (HR), oxygen saturation, end-tidal gas concentrations, and temperature were recorded. Induction and emergence times were measured to the nearest second. Induction (loss of eyelash reflex) was faster with sevoflurane (97 +/- 31 sec) than halothane (120 +/- 36 sec; p < 0.05), despite a lower inspired sevoflurane MAC. Emergence was faster with sevoflurane (9.9 +/- 2.9 min vs. 12.5 +/- 4.7 min; p < 0.05), despite a higher MAC multiple of end-tidal sevoflurane concentration at the end of surgery. Following intubation, HR (compared with the preinduction value in the operating room) was significantly higher in the halothane group (136.8% +/- 16.3% vs. 115.0% +/- 25.6%), as was mean arterial pressure (113.2% +/- 25.5% vs. 87.8% +/- 22.6%). This finding corresponded with a higher MAC multiple of end-tidal concentration in the sevoflurane group than in the halothane group. CONCLUSIONS Induction of and emergence from anesthesia was faster with sevoflurane than halothane. Airway complications were low in both groups. Vital signs were more stable with sevoflurane during induction through intubation, and were comparable during maintenance. Sevoflurane is an excellent drug for inhalational induction in pediatric patients.

Comparison of atracurium and d-tubocurarine for prevention of succinylcholine myalgia

We compared the incidence of postoperative myalgia (POM) and fasciculations when atracurium (ATR) or d-tubocurarine (DTC) was given prior to succinylcholine (SDC) for tracheal intubation in 44 ASA class I or II outpatient females undergoing laparoscopy. The subjects were assigned to one of three groups: group 1 received 0.025 mg/kg ATR; group 2 received 0.05 mg/kg DTC; and group 3 received saline (NS), all in a double-blind manner. Thiopental was administered 1 min and 45 sec after pretreatment in doses adequate to allow control of ventilation. Three minutes after pretreatment, SDC 1.5 mg/kg was given, and fasciculations were recorded on a scale of 0-3. All patients were questioned 1 and 3 days postoperatively about POM, using a scale of 0-3. Fasciculations occurred in 79% of patients given saline, in 46% of those receiving ATR, and in 12% of those given DTC. Eighty-five percent of ATR patients were free of POM on postoperative day 1. The corresponding figures for DTC and NS were 59% and 43%, respectively. Only the difference between ATR and NS achieved statistical significance. On the third postoperative day, POM was rare and there were no significant differences among the groups. We conclude that DTC is a better defasciculant than ATR. DTC was, however, not significantly better than NS in the prevention of POM. The findings suggest that ATR may be the drug choice for the prevention of POM.

Priming with atracurium

Priming with atracurium was evaluated by dividing 39 patients into 2 groups. All received 0.2 mg IV glycopyrrolate and fentanyl, 50 μg IV. Group 1 received saline, group 2 received 0.06 mg/kg atracurium and a stop watch was started. After 3.5 min the patients were asked to lift their heads and maximum negative inspiratory pressure (MIP) was measured. Anesthesia then commenced with thiorpental and a twitch monitor was applied to the ulnar nerve. At 5 min group 1 received 0.36 mg/kg atracurium and group 2 was given 0.30 mg/kg atracurium. At 6.5 min intubation was accomplished in all but one patient in group 1 and all but one in group 2. Mean T4/T1 ratios at 90 sec were 0.73 in group 1 and 0.51 in group 2. This difference was statistically significant (P < 0.001). Bucking on the endotracheal tube occurred in 72% of patients in group 1 and 62% of those in group 2 (not significant). Intubating conditions were “excellent” in 56% of those in group 1 and 75% in group 2 (not significant). “Good” conditions were seen in 33% of group 1 and 15% of group 2 patients (not significant). “Fair” conditions were noted in 6% of patients in group 1 and 5% of group 2 patients (not significant). The time to maximum twitch depression was 11.3 min and 11.5 min in groups 1 and 2 respectively (not significant). All patients in group 1 could sustain head lift whereas four patients in group 2 could not (not significant). A decrease in MIP was noted in 38% of patients in group 2, but MIP was not decreased in those in group 1. This difference was statistically significant (P < 0.005). We conclude that priming with atracurium, although providing a small improvement in T4/T1 ratio at intubation, does not significantly improve intubating conditions. It is complex, time consuming, is not well tolerated, and may put patients at risk for aspiration.

Intravenous labetalol for the treatment of hypertension after carotid endarterectomy

Hypertension after carotid endarterectomy has a variable incidence ranging up to 56%. Blood pressure (BP) control is essential due to possible increased risk of morbidity from neurologic deficits or cardiovascular complications. This study evaluated intravenous labetalol for control of hypertension after carotid endarterectomy. Sixty ASA II-IV patients were studied; 20 developed BP high enough for treatment with labetalol. The anesthetic technique was standardized. Labetalol was administered at the conclusion of surgery as a 20-mg bolus over two minutes followed by 40 mg every 10 minutes until the desired BP was achieved (BP less than or equal to 10% above average preoperative BP or less than 150 mmHg, systolic) or 300 mg had been given. The mean total dose of labetalol was 42.0 +/- 33.0 mg (mean +/- SD) and mean time to reach the desired BP was 16.2 +/- 21.4 minutes. Systolic, diastolic, mean arterial pressure and heart rate significantly decreased after labetalol treatment and remained so for the remainder of the 180-minute study period. There was no hypotension, bradycardia, evidence of myocardial ischemia or central nervous system dysfunction present with labetalol treatment. Blood samples were obtained for determination of plasma renin activity, epinephrine, and norepinephrine in 10 patients who developed hypertension and received labetalol, and 10 patients who did not develop hypertension. In the patients developing hypertension, there was a significant elevation in epinephrine just before treatment, that decreased by 30 minutes after treatment. Norepinephrine levels became significantly elevated five minutes after labetalol treatment in the group with hypertension and remained elevated for 120 minutes. Concomitantly, there was a significantly lower plasma renin activity seen in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of labetalol and nitroprusside for inducing hypotension during major surgery.

The hemodynamic and intrapulmonary shunt effects of intravenous labetalol and nitroprusside were compared during induced hypotension for major spinal surgery. A randomized, double-blind protocol was used in which 20 patients, ASA physical status I or II, received either nitroprusside infusion (n = 10) or labetalol bolus injections of 10 mg every 10 min (n = 10) until mean arterial blood pressure was reduced to 55--60 mm Hg. Pulmonary artery pressures were measured and mixed venous samples obtained via a pulmonary artery catheter. Nitroprusside increased heart rate significantly more than labetalol during the period of hypotension. When compared with prehypotension baseline values, nitroprusside increased heart rate significantly with a concomitant significant decrease in systemic vascular resistance. Cardiac output increased significantly 60 min after hypotension was achieved in patients treated with nitroprusside. Systemic vascular resistance decreased significantly below baseline levels in patients treated with labetalol but without changes in cardiac output, heart rate, or mean pulmonary artery pressure. There was a 122% increase in intrapulmonary shunt with nitroprusside administration, compared with an 11% increase with labetalol. Labetalol was effective for inducing hypotension and was not associated with an increase in heart rate, intrapulmonary shunt, or cardiac output as seen with nitroprusside.

Intubating Conditions after Pipecuronium Bromide: The Influence of Dose and Time

STUDY OBJECTIVE To determine the intubating conditions following the administration of pipecuronium bromide in doses of two (0.07 mg/kg) or three (0.1 mg/kg) times ED95 (average dose that gives 95% block of the first twitch). DESIGN To compare intubating conditions at 11/2 and 21/2 minutes in 41 patients receiving balanced anesthesia. SETTING Surgical patients at Thomas Jefferson University Hospital. PATIENTS Forty-one patients undergoing surgical procedure who received general anesthesia. INTERVENTIONS After obtaining a stable baseline of train-of-four (TOF), 41 patients randomly received either 0.07 mg/kg or 0.1 mg/kg of pipecuronium as a single intravenous (IV) bolus dose, and the trachea was intubated either at 11/2 or 21/2 minutes. MEASUREMENTS AND MAIN RESULTS Intubating conditions at 21/2 minutes appeared significantly better than those at 11/2 minutes, regardless of the pipecuronium dose. The mean time for T1 (first twitch of TOF) to reach 50% and 90% suppression was 1.36 +/- 0.51 minutes and 2.29 +/- 0.8 minutes, respectively, for the 0.07 mg/kg dose and 1.07 +/- 0.27 minutes and 1.72 +/- 0.45 minutes, respectively, for the 0.1 mg/kg dose. This did not make a significant difference in intubating conditions at either time. The time to 25% recovery of T1 was 68.2 +/- 22 minutes for the 0.07 mg/kg dose and 121.5 +/- 49 minutes for the 0.1 mg/kg dose. In patients who had spontaneous recovery of T1 to between 10% and 25% of control, administration of neostigmine or edrophonium resulted in identical recovery in 10 minutes. However, in patients with less than 10% spontaneous recovery of T1, neostigmine appeared to be superior to edrophonium. CONCLUSION Pipecuronium has a relatively rapid onset. The trachea could be intubated successfully in 11/2 minutes with a dose of either 0.07 mg/kg or 0.1 mg/kg. If the clinical situation requires perfect relaxation with no movement or bucking, we recommend waiting at least 21/2 minutes.