Pharmacodynamics of mivacurium in infants

A computerized infusion system was used to determine mivacuriuminfusion requirements to maintain 95% and 50% neuromuscularblock in 15 infants less than 1 yr of age. Neuromuscular blockwas measured by adductor pollicis EMG and anaesthesia maintainedwith 66% nitrous oxide in oxygen and alfentanil 50–100µg kg^–1 h^–1. Neuromuscular block was producedby repeated bolus doses of mivacurium 0.1 mg kg^–1; subsequentlythe target neuromuscular block was maintained by a closed loopinfusion. Dose potency of mivacurium was similar to that previouslypublished in children with a similar anaesthetic technique.Mean mivacurium requirement for 95% neuromuscular block was820 (SD 300) µg kg^–1 h^–1, which representedan hourly requirement of 6.6 (1.5) individual ED₉₅ doses. Infusionrequirement for 50% neuromuscular block was 320 (150) µgkg^–1 h^–1. These infusion rates were similar to thosein children. No side effects of mivacurium were noticed.     

Neuromuscular effects of atracurium during halothane-nitrous oxide and enflurane-nitrous oxide anesthesia in humans

To compare the effect of halothane and enflurane on an atracurium-induced neuromuscular blockade, the authors studied 40 patients during elective surgery. During 1.25 MAC enflurane-nitrous oxide (n = 20) or halothane-nitrous oxide (n = 20) (MAC value includes contribution from 60% nitrous oxide), the doses depressing twitch tension 50% (ED50S) for atracurium were 70 and 77 micrograms/kg, respectively. The difference was not significant. Time from injection to peak effect did not differ between groups. However, the duration of action of atracurium (expressed as duration 50 or the duration of a 50% blockade) was longer during enflurane-nitrous oxide anesthesia (34.2 min) than during halothane-nitrous oxide anesthesia (25.5 min) (P less than 0.05). The authors conclude that the potency of atracurium does not differ during halothane-nitrous oxide and enflurane-nitrous oxide anesthesia. Combining the results of this study with a previous study (atracurium ED50 = 68 micrograms/kg and 83 micrograms/kg during isoflurane-nitrous oxide and fentanyl-nitrous oxide anesthesia respectively), the potency of atracurium does not differ by more than 20% among the four anesthetic techniques studied. The background anesthetic appears to have less effect on an atracurium-induced neuromuscular blockade than on one produced by other longer-acting nondepolarizing muscle relaxants (e.g., pancuronium and d-tubocurarine).     

Hemodynamic responses during induction of anesthesia with halothane-nitrous oxide in children with or without atropine premedication

Forty three children ranged from 1yr. to 6yr. were randomly assigned to non-atropinized group (n = 20; A(–)) and atropinized group (0.015mg·kg^–1 i.m., n = 23; A(+)). Control hemodynamics were measured under 0.5% halothane and 67% nitrous oxide and 33% oxygen for three minutes, and then halothane was increased to 2.5% and maintained for 15min. In the A(–) group, stroke volume (SV) decreased to 64%, heart rate (HR) increased from 100/min to 111/min, and blood pressure (BP) decreased from 65mmHg to 62mmHg. Skin blood flow (SBF) concomitantly measured by a laser doppler flowmeter decreased to 48% and total peripheral resistance (TPR) increased to 128%. In the A(+) group, HR increased from 117/min to 132/min (P 0.05, vs. A(–) group), BP decreased from 67mmHg to 66mmHg. SV decreased to 71% (P 0.05, vs. A(–) group). Changes in SBF and TPR were 68% and 128% respectively. End-expired halothane concentration in the A(+) group increased slower than in the A(–) group but not significantly. The results indicate increased sympathetic tone would work as a compensating mechanism for decreased SV and CO. Atropine premedication attenuated cardiovascular depression by maintaing HR and possibly by delaying induction speed of anesthesia. In conclusion, halotane-nitrous oxide anesthesia decreased SV without a marked decrease in heart rate and blood pressure in children. This decrease in SV and BP was attenuated by atropine premedication.(Kawana S, Namiki A, Morita Y, et al.: Hemodynamic responses during induction on anesthesia with halothane-nitrous oxide in children with or without atropine premedication. J Anesth 6: 63–68, 1992)     

美维松临床肌松效应和安全性的评价

目的：研究在安氟醚麻醉下，使用美维松的肌松效应和心血管反应并了解其副作用。方法：使用肌松监测仪监测ＴＯＦ（四个成串刺激）变化，观察在全麻下的３０例择期手术病人，使用美维松诱导插管时的最大肌松效应，术中微量泵泵入美维松维持肌松的有效剂量及停药后恢复指数，并了解其对电解质，肝肾功能的影响。结果：静脉注射美维松０．２ｍｇ／ｋｇ（３ＥＤ９５）后，在１１９±４．０秒获得最大阻滞及良好的气管插管条件，以５．８μｇ·ｋｇ－１·ｍｉｎ－１速度输入美维松可维持良好的肌肉阻滞，停药后恢复指数为９．９±４．０分钟，手术前后电解质，肝肾功能无明显变化。结论：美维松适用于诱导插管和短小手术的肌松维持，采用静脉输注也可满足中长手术的肌松需要。     

Comparison of the neuromuscular effects of mivacurium and suxamethonium in infants and children

We compared both the time course of neuromuscular blockade and the cardiovascular side-effects of suxamethonium and mivacurium during halothane and nitrous oxide anaesthesia in infants 2–12 months and children 1–12 years of age. Equipotent doses of mivacurium and suxamethonium were studied; 2.2×ED₉₅ was used in four groups of infants and children, while 3.4×ED₉₅ was used in two groups of children. Onset of neuromuscular block in infants was not significantly faster with suxamethonium than with mivacurium ( P =0.2). In all infants given suxamethonium, intubating conditions were excellent, while, in 6/10 infants given mivacurium, intubating conditions were excellent. Onset of complete neuromuscular block in children was significantly faster with suxamethonium, 0.9 min compared with mivacurium, 1.4 min ( P ×0.05). Increasing the dose of suxamethonium or mivacurium in children to 3.4×ED₉₅ did not change the onset of neuromuscular block. Recovery of neuromuscular transmission to 25% of initial twitch height (T₂₅) in infants and children was significantly faster after suxamethonium than after mivacurium, at 2.5 and 6 min, respectively ( P ×0.05). In children given 3.4×ED₉₅ of suxamethonium or mivacurium, recovery from neuromuscular block was almost identical with the dose of 2.2×ED₉₅, with spontaneous recovery to T₂₅ prolonged by only 0.5 min. No infant or child had hypotension after the mivacurium bolus dose.     

The safety and efficacy of sevoflurane anesthesia in infants and children with congenital heart disease

We tested the hypothesis that sevoflurane is a safer and more effective anesthetic than halothane during the induction and maintenance of anesthesia for infants and children with congenital heart disease undergoing cardiac surgery. With a background of fentanyl (5 microg/kg bolus, then 5 microg. kg(-1). h(-1)), the two inhaled anesthetics were directly compared in a randomized, double-blinded, open-label study involving 180 infants and children. Primary outcome variables included severe hypotension, bradycardia, and oxygen desaturation, defined as a 30% decrease in the resting mean arterial blood pressure or heart rate, or a 20% decrease in the resting arterial oxygen saturation, for at least 30 s. There were no differences in the incidence of these variables; however, patients receiving halothane experienced twice as many episodes of severe hypotension as those who received sevoflurane (P = 0.03). These recurrences of hypotension occurred despite an increased incidence of vasopressor use in the halothane-treated patients than in the sevoflurane-treated patients. Multivariate stepwise logistic regression demonstrated that patients less than 1 yr old were at increased risk for hypotension compared with older children (P = 0.0004), and patients with preoperative cyanosis were at increased risk for developing severe desaturation (P = 0.049). Sevoflurane may have hemodynamic advantages over halothane in infants and children with congenital heart disease. IMPLICATIONS: In infants and children with congenital heart disease, anesthesia with sevoflurane may result in fewer episodes of severe hypotension and less emergent drug use than anesthesia with halothane.     

Pharmacodynamics of vecuronium in infants during intravenous induction of anesthesia with ketamine

The pharmacodynamic effects of vecuronium in children aged 1 to 6 years were investigated after intravenous induction of anaesthesia with ketamine, using an initial dose of vecuronium of 0.08 mg/kg body wt. 0.1 mg/kg body wt. The degree of neuromuscular blockade was determined by measuring the contraction force of the m. adductor pollicis after supramaximal stimulation of the ulnar nerve using an electromechanical device. The results (median, chi min and chi max) were as follows. For the initial dose 0.08 mg/kg body wt., the onset time was 150 s (110-360 s); total blockade: 5 of 9 children, D25 (duration of 25% recovery) 13 min (10-31); RI (recovery index): 8.5 min (6.0-14.5); D90 (duration of 90% recovery): 27 min (20-44). For the initial dose of 0.1 mg/kg body wt., the onset time was 135 s (80-300); total blockade: all children, D25: 19.5 min (12-32.5); RI: 8.75 min (6.5-13.5); D90 35 min (22-45). Only the D25 was significantly shorter using an initial dose of 0.08 mg/kg body wt. For a total blockade, a higher dose of vecuronium is necessary using intravenous induction of anaesthesia compared with previously described inhalation techniques. Even with the high dosage, recovery from neuromuscular blockade is so rapid in this age group that it can be used even for short operations without reversal.     

Pharmacodynamics of high-dose vecuronium in children during balanced anesthesia.

To compare the speed of onset, intubating conditions, duration of action, and recovery from neuromuscular blockade with vecuronium to those with succinylcholine, 40 ASA physical status 1 or 2 children (ages 2-9 yr) were studied during N2O-O2-opioid anesthesia. Each child was randomly assigned to receive a bolus dose of one of the following muscle relaxants: succinylcholine 2.0 mg/kg (n = 10), vecuronium 0.1 mg/kg (n = 10), vecuronium 0.2 mg/kg (n = 10), or vecuronium 0.4 mg/kg (n = 10). The evoked electromyogram of the abductor digiti minimi to train-of-four stimulation was monitored. We found that with succinylcholine, the time to 95% twitch depression (speed of onset, mean +/- SD), 24 +/- 7 s, was significantly less than that with each dose of vecuronium: 0.1 mg/kg, 83 +/- 21 s; 0.2 mg/kg, 58 +/- 17 s; and 0.4 mg/kg, 39 +/- 11 s, respectively (P less than 0.05). The time to laryngoscopy and intubation did not differ significantly between succinylcholine (48 +/- 10 s) and vecuronium 0.4 mg/kg (57 +/- 13 s); however, both were significantly less than than with vecuronium 0.1 and 0.2 mg/kg (P less than 0.005). The intubating conditions were excellent in 100% of patients. The duration of action was least with succinylcholine (5.7 +/- 1.5 min) and increased with increasing doses of vecuronium: 0.1 mg/kg, 23.9 +/- 5.1 min; 0.2 mg/kg, 55.2 +/- 11.6 min; and 0.4 mg/kg, 74.6 +/- 9.9 min, respectively (P less than 0.001). The recovery index was most rapid with succinylcholine (1.6 +/- 0.4 min) and was slowest with vecuronium 0.4 mg/kg (22.6 +/- 2.1 min) (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Nitrous oxide: cardiovascular effects in infants and small children during halothane and isoflurane anesthesia

Two-dimensional and pulsed Doppler echocardiography were used to measure cardiovascular function in 31 unmedicated infants and small children. In 15 patients, the cardiovascular effects of equipotent levels of halothane were compared with and without N2O. In 16 patients, the cardiovascular effects of isoflurane with and without N2O were compared. Prior to anesthesia induction, cardiovascular measurements of heart rate (HR), mean blood pressure (MBP), and two-dimensional and pulsed Doppler echocardiography were recorded. The echocardiographic measurements were used to determine cardiac output (CO), stroke volume (SV), ejection fraction (EF), and left ventricular end-diastolic and end-systolic volume (LVEDV and LVESV). Twenty minutes after mask inhalation induction with halothane or isoflurane with N2O and O2 (3:2 liters/min), cardiovascular measurements were repeated with end-expired halothane or isoflurane maintained at 0.9 MAC. A third set of cardiovascular data was collected 10 minutes after the discontinuation of N2O, with inspired isoflurane or halothane levels in O2 (5 liters/min) increased to maintain 1.5 MAC end-expired levels. Ventilation was controlled throughout the study period and the study was completed before intubation and the start of elective surgery. Heart rate and MBP decreased to similar degrees below awake levels in both patient groups during N2O with halothane or isoflurane. When N2O was discontinued and end-expired levels of halothane or isoflurane increased, MBP remained at levels observed during N2O-O2 with halothane or isoflurane. Heart rate increased during isoflurane in O2. Cardiac output decreased significantly and similarly below awake levels during both halothane of isoflurane with and without N2O.     

Induction and maintenance characteristics of anesthesia with desflurane and nitrous oxide in infants and children.

To determine the induction and maintenance characteristics of desflurane in pediatric patients, the authors anesthetized 206 infants and children aged 1 month to 12 yr with nitrous oxide plus desflurane and/or halothane in oxygen. Patients were assigned to one of four groups: anesthesia was 1) induced and maintained with desflurane after premedication with an oral combination of meperidine, diazepam, and atropine; 2) induced and maintained with desflurane; 3) induced with halothane and maintained with desflurane; or 4) induced and maintained with halothane. An unblinded observer recorded time to loss of consciousness (lid reflex), time to intubation, and clinical characteristics of the induction and maintenance of anesthesia. Moderate-to-severe laryngospasm (49%) and moderate-to-severe coughing (58%) occurred frequently during induction of anesthesia with desflurane; the incidence of these was not altered by premedication. In contrast, laryngospasm and coughing were rare during induction of anesthesia with halothane. In unpremedicated patients, time to loss of lid reflex (mean +/- SD) was similar for desflurane (2.4 +/- 1.2 min) and halothane (2.1 +/- 0.8 min). During induction of anesthesia, before laryngoscopy and intubation, mean arterial pressure less than 80% of baseline was more common with halothane; heart rate and mean arterial pressure greater than 120% of baseline were more common with desflurane. Intraoperatively, heart rate greater than 120% of baseline was more common with desflurane; blood pressures were similar for the two anesthetics. The authors conclude that the high incidence of airway complications during induction of anesthesia with desflurane limits its utility for inhalation induction in pediatric patients. Anesthesia can be safely maintained with desflurane if induced with a different anesthetic.     

Sevoflurane-nitrous oxide or halothane-nitrous oxide for paediatric bronchoscopy and gastroscopy

We have studied 120 infants and children, in three age groups (3-11 months, 1-5 yr and 6-15 yr), to compare anaesthesia with sevoflurane or halothane for bronchoscopy or gastroscopy, or both. Premedication or i.v. anaesthetic agents were not used. Patients were allocated randomly to receive either 7% sevoflurane or 3% halothane in 66% nitrous oxide in oxygen for induction of anaesthesia. The same inspired mixture was continued during bronchoscopy while the concentration of the inhalation agent was reduced by 50% during gastroscopy. Induction times were shorter for infants than for children and shorter for sevoflurane than for halothane. Cardiac arrhythmias were significantly more frequent during halothane than during sevoflurane anaesthesia. Physiological and psychomotor recovery were more rapid after sevoflurane than after halothane. At 24-h follow-up, children who received sevoflurane had significantly less nausea and vomiting. We conclude that sevoflurane was superior to halothane for paediatric bronchoscopy and gastroscopy.      

Pharmacodynamics and intubating conditions of cisatracurium in children during halothane and opioid anesthesia

STUDY OBJECTIVES: To determine the pharmacodynamics and intubating conditions of cisatracurium 0.2 mg/kg in children aged 2 to 12 years. DESIGN: Open-label, randomized study.SETTING: Operating room of a university-affiliated hospital.PATIENTS: 42 ASA physical status I and II patients, 24 to 155 months of age.INTERVENTIONS: Patients were assigned to one of two groups: halothane anesthesia (G1) and opioid anesthesia (G2). Subsequently, each group was divided into two age subgroups: 24-59 months and 60-155 months. All patients were premedicated with midazolam intranasal 0.1 to 0.2 mg/kg. In G1, anesthesia was induced with halothane up to 3% and N(2)O/O(2) (60-70/30-40%). Halothane was reduced to 0.05).CONCLUSIONS: Cisatracurium 0.2 mg/kg offered acceptable intubating conditions at 90 seconds in 98% of pediatric patients, regardless of the anesthesia-based technique. Longer clinical duration in the halothane group in younger children may be due to age-related potentiation or to the small number of patients enrolled in the younger subgroup.