Choice of the muscle relaxant for rapid-sequence induction:

Factors that affect the onset of action of non-depolarizing neuromuscular blocking agents

Neuromuscular blockade plays an important role in the safe management of patient airways, surgical field improvement, and respiratory care. Rapid-sequence induction of anesthesia is indispensable to emergency surgery and obstetric anesthesia, and its purpose is to obtain a stable airway, adequate depth of anesthesia, and appropriate respiration within a short period of time without causing irritation or damage to the patient. There has been a continued search for new neuromuscular blocking drugs (NMBDs) with a rapid onset of action. Factors that affect the onset time include the potency of the NMBDs, the rate of NMBDs reaching the effect site, the onset time by dose control, metabolism and elimination of NMBDs, buffered diffusion to the effect site, nicotinic acetylcholine receptor subunit affinity, drugs that affect acetylcholine (ACh) production and release at the neuromuscular junction, drugs that inhibit plasma cholinesterase, presynaptic receptors responsible for ACh release at the neuromuscular junction, anesthetics or drugs that affect muscle contractility, site and methods for monitoring neuromuscular function, individual variability, and coexisting disease. NMBDs with rapid onset without major adverse events are expected in the next few years, and the development of lower potency NMBDs will continue. Anesthesiologists should be aware of the use of NMBDs in the management of anesthesia. The choice of NMBD and determination of the appropriate dosage to modulate neuromuscular blockade characteristics such as onset time and duration of neuromuscular blockade should be considered along with factors that affect the effects of the NMBDs. In this review, we discuss the factors that affect the onset time of NMBDs.

Risk over time and risk factors of intraoperative respiratory events: a historical cohort study of 14,153 children

Background

The variation in the rate of intraoperative respiratory events (IRE) over time under anesthesia and the influence of anesthesia-related factors have not yet been described. The objectives of this study were to describe the risk over time and the risk factors for IRE in children at a tertiary care hospital in southern Thailand.

Methods

The surveillance anesthetic database and chart review of IRE of 14,153 children who received surgery at Songklanagarind Hospital during January 2005 to December 2011 were used to obtain demographic, surgical and anesthesia-related data. Incidence density of IRE per person-time was determined by a Poisson modelling. Risk of IRE over time was displayed using Kaplan Meier survival and Nelson-Aalen curves. Multivariate Cox regression was employed to identify independent predictors for IRE. Adjusted hazard ratios (HR) and their 95% confidence intervals (CI) were obtained from the final Cox model.

Results

Overall, IRE occurred in 315 out of 14,153 children. The number (%) of desaturation, wheezing or bronchospasm, laryngospasm, reintubation and upper airway obstruction were 235 (54%), 101 (23%), 75 (17%), 21 (5%) and 4 (1%) out of 315 IRE, respectively. The incidence density per 100,000 person-minutes of IRE at the induction period (61.3) was higher than that in the maintenance (13.7) and emergence periods (16.5) (p < 0.001). The risk of desaturation, wheezing and laryngospasm was highest during the first 15, 20 and 30 minutes of anesthesia, respectively. After adjusting for age, history of respiratory disease and American Society of Anesthesiologist (ASA) classification, anesthesia-related risk factors for laryngospasm were assisted ventilation via facemask (HR: 18.1, 95% CI: 6.4-51.4) or laryngeal mask airway (HR: 12.5, 95% CI: 4.6-33.9) compared to controlled ventilation via endotracheal tube (p < 0.001), and desflurane (HR: 11.0, 95% CI: 5.1-23.9) compared to sevoflurane anesthesia (p < 0.001).

Conclusions

IRE risk was highest in the induction and early maintenance period. Assisted ventilation via facemask or LMA and desflurane anesthesia were anesthesia-related risk factors for laryngospasm. Therefore, anesthesiologists should pay more attention during the induction and early maintenance period especially when certain airway devices incorporated with assisted ventilation or desflurane are used.

Effects of 2 mg.kg⁻¹ of intravenous lidocaine on the latency of two different doses of rocuronium and on the hemodynamic response to orotracheal intubation

BACKGROUND AND OBJECTIVES

Lidocaine potentiates the effects of neuromuscular blockers and attenuates the hemodynamic response to orotracheal intubation. The objective of the present study was to test the effects of lidocaine on the latency of two different doses of rocuronium and on the hemodynamic response to intubation.

METHODS

Eighty patients were distributed in 4 groups: Groups 1 and 2 received 0.6 mg.kg(-1) of rocuronium; patients in Group 2 also received 2 mg.kg(-1) of lidocaine before intubation. Patients in Groups 3 and 4 received 1.2 mg.kg(-1) of rocuronium; patients in Group 4 received additional 2 mg.kg(-1) of lidocaine. The latency of the neuromuscular blockade was measured by acceleromyography. Hemodynamic evaluation was performed at baseline, immediately before, and 1 minute after orotracheal intubation (OI).

RESULTS

Statistically significant differences were not observed between the latency from 0.6 mg.kg(-1) and 1.2 mg.kg(-1) of rocuronium in patients who received lidocaine before induction and those who did not. The latency in patients who received 0.6 mg.kg(-1) of rocuronium with lidocaine was statistically similar to that of those who received 1.2 mg.kg(-1) rocuronium independently of whether lidocaine was administered or not. Patients who did not receive lidocaine before induction showed the same increases in systolic, diastolic, and mean arterial pressure and heart rate after OI, which was not observed in those patients who received lidocaine.

CONCLUSIONS

Intravenous lidocaine before anesthetic induction was capable of attenuating the hemodynamic response associated to OI maneuvers, but it did not reduce the latency of the neuromuscular blockade produced by two different doses of rocuronium.

Is 0.6 mg/kg of succinylcholine adequate for tracheal intubation in Korean?

BACKGROUND

The usual dose of succinylcholine for tracheal intubation is 1.0 mg/kg. If the patient is not ventilated by face mask after administration of the succinylcholine (1.0 mg/kg), the patient may experience significant hemoglobin desaturation. The purpose of the present study was to evaluate an appropriate dose of succinylcholine for tracheal intubation in Korean.

METHODS

Sixty patients scheduled for elective surgery were randomly divided into three groups; group I (succinylcholine 0.3 mg/kg, n = 20), group II (succinylcholine 0.6 mg/kg, n = 20), group III (succinylcholine 1.0 mg/kg, n = 20). All patients were not premedicated. After loss of consciousness, the patients received succinylcholine 0.3, 0.6, 1.0 mg/kg, respectively. The contraction responses of the adductor pollices muscle were monitored by using TOF. Tracheal intubation was accomplished as the height of T1 was inhibited maximally. Then, intubation scores were recorded. The recovery times from neuromuscular blockade in groups II and III were also measured.

RESULTS

The acceptable conditions for tracheal intubation were 30%, 100%, and 100%, respectively in groups I, II, and III. The onset time was 80.4 +/- 15.5 sec, 69.6 +/- 13.1 sec, and 56.1 +/- 9.3 sec, respectively. The recovery time (T1 = 90%) was 446.0 +/- 86.2 sec, 694.0 +/- 84.7 sec, respectively in groups II and III. The onset time was the fastest in group III. But the recovery time in group III was slower than in group II.

CONCLUSIONS

We concluded that 0.6 mg/kg of succinylcholine is an appropriate dose for tracheal intubation in Korean except for rapid sequence intubation.

Rapid sequence induction: a survey of practices in three French prehospital mobile emergency units

OBJECTIVES

This prospective study was conducted in three mobile emergency and intensive care units.

METHODS

The patients were over 15 years of age and were not in cardiac arrest. The study was to compare practices in the three units with the guidelines drawn up by the Commission of Experts so as to define the main parameters for quality assurance. All of the patients involved were considered to have full stomachs and required rapid sequence induction.

RESULTS

This procedure comply the guidelines only in 45% of cases; in the other cases succinylcholine should have been administered (mobile emergency and intensive care unit A) and the Sellick manoeuvre should have been used (mobile emergency and intensive care unit A and B). Notwithstanding, these two centres treated more traumatized patients than mobile emergency and intensive care unit C, and use of the Sellick manoeuvre in such circumstances is questionable.

CONCLUSIONS

More training and greater diffusion of the protocols are required, especially with regard to doctors who intervene intermittently.

The Rapid Sequence Induction Revisited: Obesity and Sleep Apnea Syndrome

Pulmonary aspiration is a cause of anesthesia-related morbidity and mortality, with little change in incidence over the past 20 years. Rapid sequence induction is a common procedure in obese patients, who appear to be more at risk for both pulmonary gastric aspiration and difficult airways, and is required in obese and sleep apnea syndrome patients with symptomatic gastroesophageal reflux or other predisposing conditions. In the elective obese or sleep apnea patient with no other risk factors for pulmonary aspiration, the risks and benefits of rapid sequence induction and cricoid pressure should be weighed. If rapid sequence induction is required, succinylcholine remains the neuromuscular blocking agent of choice, if there are no contraindications.

A priming technique accelerates onset of neuromuscular blockade at the laryngeal adductor muscles

PURPOSE

Priming is a known technique to accelerate onset of neuromuscular blockade (NMB). Its effect on NMB of the larynx has not been studied yet.

METHODS

We compared a priming technique with a bolus application of rocuronium on the onset of NMB at the laryngeal adductor and the adductor pollicis muscles (AP). In 30 female patients, after induction of anesthesia a tube with a surface electrode was placed into the trachea prior to the administration of any neuromuscular blocking agent to monitor electromyography (EMG) of the laryngeal adductor muscles. Neuromuscular monitoring consisted of EMG of the laryngeal adductor muscles and the left AP. Patients were randomized into two groups. After transcutaneous stimulation of the recurrent laryngeal nerve and ulnar nerve, a bolus of rocuronium 0.6 mg x kg(-1) (Bolus group) or a priming dose of rocuronium 0.06 mg x kg(-1) followed by rocuronium 0.54 mg x kg(-1) three minutes later (Priming group) were injected. Lag time, onset 90%, onset time and peak effect of NMB were recorded and compared; a P < 0.05 was considered significant.

RESULTS

The onset 90% and onset time measured at the laryngeal adductor muscles (onset: 44.7 +/- 7.4 vs 74.0 +/- 23.8 sec) and at the AP (onset: 105.4 +/- 29.9 vs 139.2 +/- 51.5 sec) were significantly shorter in the Priming group than in the Bolus group. Within groups, the onset times were significantly shorter at the laryngeal muscles in comparison to AP.

CONCLUSION

Our results indicate that a priming technique with rocuronium significantly accelerates the onset of NMB at the laryngeal adductor muscles. Our results further support the use of rocuronium as an alternative to succinylcholine for rapid sequence induction.

The effect of cisatracurium and rocuronium on cisatracurium precurarization and the priming principle

STUDY OBJECTIVE

To demonstrate the effect of administering a precurarizing dose of cisatracurium or rocuronium on the speed of onset of cisatracurium, and to review the possible mechanisms and value of the priming principle.

DESIGN

Double-blind, randomized, controlled trial.

SETTING

Inpatient anesthesia in a university teaching hospital.

PATIENTS

90 ASA physical status I and II patients undergoing elective surgery requiring endotracheal intubation.

INTERVENTIONS

Three groups of 30 patients each were investigated. Following induction of anesthesia with fentanyl and propofol, Group 1 received cisatracurium 0.015 mg.k(-1), Group 2 received rocuronium 0.09 mg. kg(-1), and Group 3 (control) received normal saline. Six minutes after priming, Groups 1 and 2 received cisatracurium 0.135 mg. kg(-1) whereas Group 3 received cisatracurium 0.15 mg. kg(-1).

MEASUREMENTS AND MAIN RESULTS

In each group, first twitch height and the train-of-four ratios were recorded every 10 seconds after the initial priming dose. Intubation was attempted after the first twitch height became less than 15% of baseline. The decrease in the train-of-four ratios at 6 minutes was 0.97 for cisatracurium and 0.85 for rocuronium. The onset of muscle relaxation was significantly faster after priming with cisatracurium and rocuronium (71.7 +/- 21.3 and 65 +/- 19.8 sec, respectively) compared with control (148.7 +/- 43.1 sec). Females receiving both muscle relaxants had a faster onset of paralysis than did males (65.9 +/- 20.6 vs. 79.2 +/- 20.6 and 55 +/- 14.5 vs. 71.7 +/- 20.4 sec). Intubation conditions were either excellent or satisfactory in all patients.

CONCLUSIONS

Six minutes after precurarization, there is no significant difference between rocuronium and cisatracurium when used as priming drugs. An even faster onset time with both drugs was demonstrated in females. The use of priming doses of 25% to 30% of ED(95) may cause symptomatic muscle weakness. The mechanisms of the priming principle are discussed.