Inhibition of succinylcholine-induced increased intragastric pressure by nondepolarizing muscle relaxants and lidocaine

Cricoid Pressure Controversies

Since cricoid pressure was introduced into clinical practice, controversial issues have arisen, including necessity, effectiveness in preventing aspiration, quantifying the cricoid force, and its reliability in certain clinical entities and in the presence of gastric tubes. Cricoid pressure–associated complications have also been alleged, such as airway obstruction leading to interference with manual ventilation, laryngeal visualization, tracheal intubation, placement of supraglottic devices, and relaxation of the lower esophageal sphincter. This review synthesizes available information to identify, address, and attempt to resolve the controversies related to cricoid pressure. The effective use of cricoid pressure requires that the applied force is sufficient to occlude the esophageal entrance while avoiding airway-related complications. Most of these complications are caused by excessive or inadequate force or by misapplication of cricoid pressure. Because a simple-to-use and reliable cricoid pressure device is not commercially available, regular training of personnel, using technology-enhanced cricoid pressure simulation, is required. The current status of cricoid pressure and objectives for future cricoid pressure–related research are also discussed.

A randomized trial to identify optimal precurarizing dose of rocuronium to avoid precurarization-induced neuromuscular block

PURPOSE

The aim of this study was to examine the safe precurarizing dose of rocuronium required to avoid neuromuscular block after precurarization.

METHODS

Twenty-four female patients were randomly allocated into two groups of 12 patients each. General anesthesia was induced and maintained with remifentanil and propofol, and a laryngeal mask was inserted without the aid of a neuromuscular blocking agent. Patients were randomized to receive either 0.03 or 0.06 mg/kg rocuronium as a precurarizing dose. Neuromuscular block was monitored using acceleromyographic train-of-four (TOF) of the adductor pollicis muscle. Three minutes after the precurarization, all patients received suxamethonium 1.5 mg/kg and were graded on severity of fasciculations.

RESULTS

The average TOF ratio was kept above 0.9 even 3 min after precurarization with 0.03 mg/kg rocuronium. In contrast, in patients who received 0.06 mg/kg rocuronium, the ratios significantly decreased to 0.72 (0.14) [mean (SD), P < 0.004] and 0.68 (0.18) (P < 0.006) 2 min and 3 min after the precurarization, respectively. No visible muscle movement was observed following suxamethonium injection, except that one patient who received 0.03 mg/kg rocuronium showed very fine muscle movements of the fingertips.

CONCLUSION

Rocuronium at 0.06 mg/kg is an overdose for precurarization. The results of the present study demonstrate that a safe and effective precurarizing dose of rocuronium is 0.03 mg/kg.

Remifentanil attenuates muscle fasciculations by succinylcholine

PURPOSE

The present visual and electromyographic study was designed to evaluate muscle fasciculations caused by succinylcholine in adults pretreated with either remifentanil 1.5 microg/kg or saline.

MATERIALS AND METHODS

The effect of remifentanil on succinylcholine-induced muscle fasciculations was studied using a double-blind method in 40 adults. After i.v. pretreatment with either remifentanil 1.5 microg/kg (remifentanil group, n = 20) or an equivalent volume of i.v. saline (saline group, n = 20), patients were anaesthetized with a 2.0 mg/kg of i.v. propofol followed by i.v. succinylcholine 1.0 mg/kg. Intensity and duration of muscle fasciculation following i.v. succinylcholine administration were recorded. Electromyography (EMG) was used to quantify the extent of muscle fasciculation following i.v. succinylcholine injection. Myalgia was evaluated 24 hours after induction time. Serum potassium levels were measured five minutes after i.v. succinylcholine administration and creatine kinase (CK) levels 24 hours after induction time.

RESULTS

Compared to saline treated controls, remifentanil decreased the intensity of muscle fasciculations caused by i.v. succinylcholine [fasciculation severity scores (grade 0 to 3) were 2/1/12/5 and 3/13/4/0 (patients numbers) in the saline group and the remifentanil group, respectively, p < 0.001]. The mean (SD) maximum amplitude of muscle action potential (MAP) by EMG was smaller in the remifentanil group [283.0 (74.4) microV] than in the saline group [1480.4 (161.3) microV] (p = 0.003). Postoperative serum CK levels were lower in the remifentanil group (p < 0.001). Postoperative myalgia was not different between the two groups.

CONCLUSION

Remifentanil 1.5 microg/kg attenuated intensity of muscle fasciculations by succinylcholine.

Muskelrelaxanzien in Deutschland 2005

Aim of this study was to evaluate application customs of muscles relaxants in hospitals compared to their use in private practice. Of the 3,260 questionnaires sent-out, 66.9% could be analyzed. Of these 54% were from anesthetists in private practice, 41% from heads of hospital anesthesia departments and 5% from heads of level one hospital anesthesia departments. The first difference between private practices and hospitals was the number of available muscle relaxants: 87% of private practices use 1-3 relaxants, whereas 79% of hospitals use 3-5. Another apparent difference was the relationship between general anesthesia and the number of intubations: 60% of private practices have over 80% of general anesthesia cases, but only 50% of these patients are intubated. On the contrary, two thirds of the hospitals have 50-80% general anesthesia cases and 60-70% of patients are intubated. The main wish for an ideal muscle relaxant was independent of private practice or hospital, short onset time, followed by fast recovery. In accordance 74% of anesthetists in hospitals and 72% of anesthetists in private practice voiced the wish for a non-depolarizing succinylcholine substitute. The results of this nationwide survey suggest that time pressure in combination with an increased specialization of anesthetists in private practice are the main factors for availability and use of muscle relaxants in routine anesthesia.

Succinylcholine: adverse effects and alternatives in emergency medicine

Succinylcholine has long been the favored neuromuscular blocking agent for emergent airway management because of its rapid onset, dependable effect, and short duration. However, it has a plethora of undesirable side effects, ranging from the inconsequential to the catastrophic. When patients requiring tracheal intubation present with potential contraindications to succinylcholine use, the emergency physician will need to substitute a rapid-onset nondepolarizing neuromuscular blocking agent, such as rocuronium or mivacurium. An understanding of the pharmacology of these agents is essential.

[Rapid sequence anesthetic induction via prehospital tracheal intubation]

The choice of sedation for emergency intubation remains controversial. This lack of consensus has led to various sedation protocols used in French prehospital care setting. A review of data from the literature suggests that the association etomidate-suxamethonium is probable the best choice for rapid sequence intubations in the prehospital setting. Its benefits include protection against myocardial and cerebral ischaemia, decreased risk of pulmonary aspiration, and a stable haemodynamic profile. Randomized studies are needed to substantiate the advantages of the association etomidate-suxamethonium for rapid sequences intubation in the prehospital setting.

Neuromuscular relaxation and reversal: an update

Neuromuscular relaxants are commonly used in the provision of general anesthesia for the majority of surgical procedures. After a brief overview of the physiology of the neuromuscular junction, pharmacology of both depolarizing and nondepolarizing muscle relaxants will be discussed. Attention will be given to side effects and factors that influence neuromuscular blockade including reversal agents. This article will provide the PACU nurse with the knowledge necessary to provide safe and effective nursing care.

Rapid sequence intubation in adults with elevated intracranial pressure: a survey of emergency medicine residency programs

A questionnaire entitled "Survey of Protocols for Rapid Sequence Intubation in Previously Healthy Adults with Elevated Intracranial Pressure" was distributed to the program directors of all 100 emergency medicine residency programs listed in the Directory of Graduate Medical Education Programs in February 1995. The medical literature on rapid sequence intubation in patients with suspected intracranial pressure elevations was reviewed. The findings of the review were compared with the survey responses. Sixty-seven program directors responded to the survey. Sixty-five programs performed rapid sequence intubation in their institution. Five programs performed 0 to 10 procedures annually. Six performed 10 to 30 annually, 19 performed 30 to 50, 17 performed 50 to 100, and 18 performed more than 100. Succinylcholine and vecuronium were the most frequently used neuromuscular blockers. Midazolam and thiopental were the most frequently used sedative induction agents. Most programs use a defasciculating agent prior to succinylcholine administration. The majority of programs do not use a priming agent before the use of a nondepolarizing neuromuscular blocking agent. Intravenous lidocaine was routinely administered prior to neuromuscular blockade. Fentanyl was the most frequently used other pretreatment medication. Rapid sequence intubation is used to facilitate definitive, emergent airway management in patients with suspected intracranial pressure elevations in almost all of the emergency medicine residency programs that responded to the survey. Most of these programs follow the guidelines recommended in the medical literature. The majority of these guidelines, however, are based on statistical data performed in the laboratory or nonemergency environments. Further clinical studies in an emergency medicine environment must be performed to determine the optimal drug regimen for rapid sequence intubation in patients with elevated intracranial pressure.

Efficacy and safety of divided dose administration of mivacurium for a 90-second tracheal intubation

STUDY OBJECTIVE

To compare the safety and effectiveness of 0.25 mg divided doses of mivacurium chloride to succinylcholine for a 90-second tracheal intubation.

DESIGN

Randomized, double-blind, multicenter study in two groups.

SETTING

Operating rooms at four university medical centers.

PATIENTS

200 healthy ASA status I and II adult patients scheduled for elective surgery with general anesthesia and endotracheal intubation.

INTERVENTIONS

Patients were premedicated with 1 to 2 mg midazolam and 2 micrograms/kg fentanyl. Anesthesia was induced with 2 mg/kg propofol. Group A received 0.25 mg/kg mivacurium given as a divided dose (0.15 mg/kg followed in 30 seconds with 0.1 mg/kg). Group B (control) received 1.5 mg/kg succinylcholine (SCh) preceded two minutes earlier by 50 micrograms/kg d-tubocurarine (dtc).

MEASUREMENTS AND MAIN RESULTS

Tracheal intubation grading, train-of-four response of the adductor pollicis, heart rate (HR), and mean arterial blood pressure (MAP) were measured and evaluated. Chi-square analysis was performed for comparison between Group A and Group B with respect to the frequency distribution of intubation using the scores excellent, good, and poor and not possible (combined). Group B had a significantly higher excellent score of intubation than Group A, 84% versus 56% (p < 0.0001). No significant difference was found between the two groups when the scores excellent and good were combined (Fisher's Exact test, p = 0.28). The changes in MAP and HR were similar for the two groups.

CONCLUSIONS

When Sch is not desirable, mivacurium 0.25 mg/kg given as a divided dose provides good to excellent intubation conditions 90 seconds after the initial dose without significant changes in MAP or HR. It can be an appropriate alternative for short surgical procedures. It must be emphasized that this conclusion does not apply to rapid-sequence induction-intubation.

Can pulmonary aspiration of gastric contents be prevented by balloon occlusion of the cardia? A study with a new nasogastric tube

Rapid-sequence induction of anesthesia and the application of cricoid pressure are the two most common maneuvers performed when patients requiring general anesthesia are at risk of pulmonary aspiration. However, these procedures are quite elaborate and entail risks and dangers in themselves. A new disposable nasogastric balloon tube was developed to prevent the reflux of gastric contents by blocking the cardia with a balloon. The effectiveness of this tube was investigated in animals and healthy volunteers. In addition, we describe the initial experience with the tube during ventilation via a mask in patients with an increased risk of aspiration. Twelve pigs with a blocked cardia did not show any gastroesophageal reflux under six different procedures to provoke vomiting and regurgitation (gastric fluid filling with different volumes, head-down positioning, drug-induced vomiting, external gastric compression before and after surgical ligation of the pyloric orifice), whereas 37 of 48 provocation maneuvers led to a reflux in eight additional pigs with an unblocked cardia. In 26 test subjects with a blocked cardia, reflux of gastric contents was not observed when vomiting was provoked. After elimination of the cardia blockade, a reflux could be triggered in 24 of the 26 subjects. Among 42 patients in danger of aspiration, anesthesia could be induced without any problems using a nasogastric balloon tube with ventilation via a mask. The present experimental findings in animals and test subjects show that the nasogastric balloon tube can prevent gastroesophageal reflux under provocation of vomiting and regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adverse effects of depolarising neuromuscular blocking agents. Incidence, prevention and management

Muscle relaxants block neuromuscular transmission, acting at nicotinic acetylcholine receptors of the neuromuscular junction. Suxamethonium (succinylcholine) is a depolarising agent, whereas all other relaxants in clinical use are nondepolarising. The desired neuromuscular block results from the structural similarity of muscle relaxants to acetylcholine, enabling the interaction with receptors at the neuromuscular junction. Adverse effects of suxamethonium are generally related to its agonist mode of action. Autonomic cardiovascular effects may result. Other adverse effects include anaphylactic or anaphylactoid reactions, and histamine release. Various disease states may present specific considerations in the use of muscle relaxants. Although many complications of muscle relaxants (such as prolonged block or resistance) are easily treated, others may require immediate intervention and vigorous therapy. Careful selection of appropriate relaxants for particular patients will usually prevent the occurrence of complications.

Waiting time after non-depolarizing relaxants alter muscle fasciculation response to succinylcholine

The purpose of the study was to determine the effect of nondepolarizing muscle relaxants and waiting time on muscle fasciculations after succinylcholine in anaesthetized patients. Adult men and women, 60-80 kg, received pretreatment doses of atracurium 5 mg (n = 160), pancuronium 1 mg (n = 123), d-tubocurarine 3 mg (n = 97), or vecuronium 1 mg (n = 62). Waiting times between pretreatment and succinylcholine, 100 mg, ranged between 0.6 and 5 min. Data points (presence or absence of fasciculations and waiting time) were entered for each patient. Waiting time response curves were obtained between the logit transformation of the probability of no fasciculations and the log waiting time for each drug. Statistical differences between wait time response curves were determined by non-overlapping of the associated 95% confidence intervals. The frequency of muscle fasciculations was reduced with increased waiting time for all nondepolarizers tested. Following wait times of three, four and five minutes, the probability of not fasciculating was greatest with d-tubocurarine (90, 97 and 99%, respectively) and atracurium (89, 93 and 96%). Corresponding values for pancuronium were 70, 82 and 88% and for vecuronium were 74, 82 and 86%. Waiting times to prevent fasciculations in 80% and 90% of patients were shorter with d-tubocurarine (2.46 and 3.02 min, respectively) or atracurium (2.16 and 3.24 min) than pancuronium (3.77 and 5.35 min) or vecuronium (3.73 and 6.36 min).(ABSTRACT TRUNCATED AT 250 WORDS)

[Intra-abdominal pressure]

The abdominal pressure is a hydrostatic one, which can be measured in the bladder, the rectum and the stomach. In physiologic conditions, the abdominal pressure is variable, with peaks as high as 100 to 200 mmHg at the time of defecation, cough. The increase in abdominal pressure elicited by abdominal distension or compression acts directly on the abdominal compartment, indirectly on the thoracic compartment, and modifies the circulation and the ventilation. Venous return is decreased as the inferior vena cava is compressed. The systemic resistances are also increased as the abdominal vessels are compressed. Therefore the circulation is mainly distributed to the superior part of the body. Although the cardiac output is decreased, the usual haemodynamic parameters remain in the normal range: arterial pressure is increased, heart rate is unchanged, central venous pressure is increased, cardiac failure is unusual. The abdominal distension is also responsible for a restrictive respiratory syndrome, mainly due to the ascension of the diaphragm. The compression of the abdominal content explains renal effects and the decreased diuresis. A sustained increase in abdominal pressure occurs in several clinical conditions. During coelioscopy, abdominal pressure is a under control and the cardiovascular effects are minor. Insufflation with CO2 carries the risk of hypercapnia, gas embolism and pneumothorax. During abdominal tamponade, anuria is directly related to the level of pressures. At an abdominal pressure over 25 mmHg, anuria is common and decompression becomes essential. The G suit increases arterial pressure either by elevating vascular resistances or increasing blood content in the upper part of the body. Therefore cardiac tolerance can be decreased especially in cardiac patients. The adverse effects of abdominal pressure can also be observed in case of peritoneal dialysis and ascites. The risk of regurgitation associated with an increased abdominal pressure must also be kept in mind. The abdominal pressure plays an important role in anaesthesia as well as in surgery. Therefore its measurement, which is easy, should become a routine.

Alfentanil inhibits muscle fasciculations caused by suxamethonium in children and in young adults

The effect of alfentanil on suxamethonium-induced muscle fasciculations was studied in a double-blind study in 34 children (mean age 6.8 years) and in 30 adults (mean age 20 years). After pretreatment with either alfentanil 50 micrograms kg-1 or saline, each patient was anaesthetized with a sleep dose of thiopental followed by suxamethonium 1.5 mg kg-1 for endotracheal intubation. Compared to the control groups, alfentanil significantly decreased the intensity of visible muscle fasciculations caused by suxamethonium. In children, the duration of muscle fasciculations was shorter in the alfentanil than in the control group. In adults, the intensity rather than the duration of fasciculations was attenuated by alfentanil. The inhibition of fasciculations caused by alfentanil was also demonstrated in children in the surface electromyogram recorded on the biceps. There was no circulatory response to endotracheal intubation in the groups pretreated with alfentanil.

Rapid-sequence intubation of head trauma patients: prevention of fasciculations with pancuronium versus minidose succinylcholine

INTRODUCTION

Fasciculations during rapid-sequence intubation may lead to increased intracranial pressure and emesis with aspiration. Standard rapid-sequence intubation requires a nondepolarizing blocking agent before succinylcholine administration.

HYPOTHESIS

Prevention of fasciculations during rapid-sequence intubation of head trauma patients can be accomplished as safely and effectively with minidose succinylcholine as with a defasciculating dose of pancuronium.

DESIGN

A prospective, randomized, double-blind study.

SETTING

An inner-city county trauma center with 70,000 patient visits per year.

PARTICIPANTS

Sequential adult head trauma patients requiring rapid-sequence intubation who had no contraindications to succinylcholine or pancuronium.

INTERVENTIONS

Each head trauma patient requiring rapid-sequence intubation who met the inclusion criteria received standard rapid-sequence intubation maneuvers and lidocaine (1 mg/kg) IV. Patients were randomized to receive either minidose succinylcholine (0.1 mg/kg) or pancuronium (0.03 mg/kg) IV one minute prior to the full paralytic dose of succinylcholine (1.5 mg/kg) IV. Fasciculations were recorded using a graded visual scale.

RESULTS

Of 46 patients, eight of 19 (42%) in the pancuronium group and six of 27 (22%) in the succinylcholine group experienced fasciculations. No statistically significant difference in fasciculations was detected between the two groups using chi 2 analysis. Complete relaxation of the cords was present in all but two patients, one in each group. No patient in either group experienced emesis or significant dysrhythmias.

CONCLUSION

Pretreatment with minidose succinylcholine causes no greater incidence of fasciculations than pancuronium in rapid-sequence intubation of head trauma patients in an ED setting. Thus succinylcholine may be used as the sole paralytic agent in rapid-sequence intubation of head trauma patients.

Attenuation of suxamethonium myalgias. Effect of midazolam and vecuronium

We studied the incidence of fasciculations and postoperative myalgias in 100 female outpatients who had laparoscopy under thiopentone, N2O, isoflurane anaesthesia. Four groups of 20 patients each were pretreated with saline (group 1), tubocurarine 0.05 mg/kg (group 2), vecuronium 0.006 mg/kg (group 3), or midazolam 0.025 mg/kg (group 4), followed by suxamethonium 1.5 mg/kg. Group 5 received only vecuronium 0.1 mg/kg as relaxant (no suxamethonium). Fasciculations were graded, and postoperative myalgias rated on the first and third postoperative days. In groups 1-5 the incidence of fasciculations was 95, 15, 25, 95 and 0%; the incidence of myalgias on the first day after operation was 70, 45, 65, 75 and 60%, and on the third day after operation 20, 5, 20, 20, and 5%, respectively. We conclude that pretreatment with vecuronium, but not midazolam, decreases the incidence of fasciculations after suxamethonium (p less than 0.05) and that in this patient population, postoperative myalgias appear to be unrelated to the use of suxamethonium.

Gastroesophageal reflux during anesthetic induction with thiopental and succinylcholine

The effects of patient physiology and the prior administration of a nondepolarizing muscle relaxant on the frequency of gastroesophageal reflux during induction with thiopental sodium and succinylcholine were investigated. Forty patients underwent anesthetic induction during continuous esophageal pH monitoring. Twenty patients had preoperative symptoms of gastroesophageal reflux, and 20 asymptomatic patients served as controls. Half the patients in each group received a small dose of nondepolarizing muscle relaxant prior to induction. Five patients (25%) with gastroesophageal reflux and none of the control patients showed significant decreases in esophageal pH during induction. Two of these patients received prior administration of a nondepolarizing drug. In all five patients, reflux occurred during laryngoscopy and intubation, suggesting the possibility that succinylcholine did not play a role in the generation of reflux. Preoperative gastroesophageal reflux symptomatology is associated with an increased frequency of reflux during induction, and the vulnerable period seems to occur after the achievement of neuromuscular blockade during laryngoscopy. Preinduction administration of a non-depolarizing muscle relaxant prior to succinylcholine use had no demonstrable effect on the frequency of reflux during induction, although the numbers studied were too small to be conclusive.

Adverse reactions and interactions of the neuromuscular blocking drugs

The adverse reactions seen following administration of neuromuscular blocking agents are mainly cardiovascular. Due to the lack of specificity for the nicotinic receptor at the neuromuscular junction, these agents may interact with receptors in autonomic ganglia and muscarinic receptors in the heart. Furthermore, muscle relaxants may have histamine-releasing properties. The cardiovascular effects vary with potency and specificity of the drug, depending mainly on the chemical structure. Pancuronium, fazadinium and especially gallamonium block cardiac muscarinic receptors, and tachycardia may be seen. Atracurium, metocurine and in particular d-tubocurarine have histamine-releasing properties and may cause flushing, hypotension and tachycardia. Vecuronium has no effect on the cardiovascular system. The effect of succinylcholine on heart rate differs between children, where bradycardia is seen, and adults in whom tachycardia may follow. However, bradycardia may occur in adults following a single dose. Succinylcholine increases plasma potassium, especially in patients with nerve damage, and arrhythmias may be observed. The neuromuscular adverse effects of succinylcholine, such as fasciculations and increased gastric and intraocular pressure, may be prevented by precurarisation. Many drugs interact with neuromuscular blocking agents and there is often a potentiation of the neuromuscular effect. This is of clinical importance in the case of antibiotics, inhalational anaesthetics, lithium and cyclosporin. Difficulty in reversing the block may occur with calcium channel blockers and polymyxin. However, some drugs, such as phenytoin, carbamazepine and lithium, may cause resistance to neuromuscular blocking agents. Furthermore, clinically important interactions exist between individual neuromuscular blocking drugs. Precurarisation with a non-depolarising drug prolongs the onset of succinylcholine, and conversely a prolonged effect of non-depolarising drugs is seen following succinylcholine. The effect of succinylcholine is markedly prolonged if the drug is administered during recovery from pancuronium blockade or following neostigmine for reversal. Succinylcholine is hydrolysed by plasma cholinesterase, and drugs which decrease the activity of this enzyme may produce a prolonged block, i.e. contraceptive pills, cyclophosphamide, echothiopate and organophosphate.

Myalgia in outpatient surgery: comparison of atracurium and succinylcholine

We studied 60 outpatients randomly divided into two groups. Anesthesia was induced with fentanyl 1.5 micrograms.kg-1 plus thiopentone 5-7 mg.kg-1. Patients in Group I were intubated with the aid of succinylcholine 1.5 mg.kg-1 after pre-treatment with d-tubocurarine 0.05 mg.kg-1. Group II received atracurium 350 micrograms.kg-1 three minutes after a priming dose of 50 micrograms.kg-1. Anesthesia was maintained with isoflurane 1-2 per cent in a mixture of nitrous oxide 60 per cent and oxygen 40 per cent. No supplemental doses of fentanyl or atracurium were given. Intubation conditions were satisfactory for all patients in both groups. There was no significant difference in intubation score between the two groups. The incidence of myalgia was 76 per cent in the succinylcholine group compared to 23 per cent in the atracurium group (p less than 0.005). Fifty per cent of the patients in the succinylcholine group had myalgia necessitating bed rest or analgesics compared to 23 per cent in the atracurium group (p less than 0.05). We conclude that atracurium is a suitable neuromuscular relaxant for outpatient surgery and that myalgia is a major morbidity factor in this population that can be reduced by the use of atracurium instead of succinylcholine.

Optimal time interval between pretreatment with alcuronium and suxamethonium during anaesthetic induction

Alcuronium 0.03 mg/kg was studied in a double-blind randomized fashion as a pretreatment before suxamethonium using different time intervals between the administration of the drugs in 78 patients (ASA I-II) undergoing otolaryngological surgery. Alcuronium was given 1, 2 or 3 min before suxamethonium 1.5 mg/kg. The control group received saline as a pretreatment and suxamethonium 1 mg/kg. Anaesthesia was induced with thiopental 5.5 mg/kg over 60 s. Muscle fasciculations, intubating conditions, cardiovascular responses to endotracheal intubation and duration of neuromuscular block were assessed. Muscle fasciculations were statistically and similarly inhibited (P less than 0.01) at all time intervals between alcuronium and suxamethonium. Intubating conditions were worse (P less than 0.05) in the 3-min group than in the other groups. Cardiovascular responses to endotracheal intubation were similar in all groups. The neuromuscular block after suxamethonium was significantly shorter (P less than 0.05) in the 2- and 3-min groups than in the other groups. In conclusion, from the clinical point of view the 1-min time interval between alcuronium and suxamethonium is optimal since muscle fasciculations are inhibited and intubating conditions are satisfactory.

Cardiovascular effects of nondepolarizing relaxants employed for pretreatment prior to succinylcholine

A pregnant woman with severe pre-eclampsia experienced a hypertensive crisis following a pretreatment dose (20 mg) of gallamine. That episode initiated a study to determine the cardiovascular effects of non-depolarizing muscle relaxants in 58 nonobese, ASA physical status I and II adults. Subjects were assigned randomly to one of five treatment groups as follows: gallamine (0.29 mg X kg-1), d-tubocurarine (0.04 mg X kg-1), metocurine (0.014 mg X kg-1), pancuronium (0.007 mg X kg-1), or normal saline (control). Baseline measurements of systolic, diastolic, mean arterial pressure, heart rate (HR) and rate pressure product (calculated RPP) were recorded at one-minute intervals while electrocardiogram, lead II, was recorded continuously. Statistically significant increases occurred in HR at minutes 2, 3 and 4; RPP at minutes 3 and 4; and per cent change in HR at minutes 2, 3 and 4 following gallamine pretreatment. The rise in RPP was predominantly due to the elevation in HR. These results suggest that even modest doses of gallamine should be avoided in clinical situations where lability of cardiovascular dynamics can be anticipated.

[Prevention of hyperkalemia and muscular fasciculations induced by suxamethonium]

Suxamethonium has not yet been replaced to ease endotracheal intubation despite its many undesirable side effects. Hyperkalemia and muscle pain are two such side effects; they are not reliably prevented by giving, before suxamethonium, a small dose of a non depolarizing muscle relaxant, although it does decrease muscle fasciculations. The purpose of this study was to compare with a control group three different pretreatments of these undesirable effects of suxamethonium: 1) hyperventilation, 2) calcium chloride which are accepted means of lowering the serum potassium, and 3) magnesium sulfate which has been reported in a non-controlled study to decrease muscle fasciculations. The study was performed in 40 patients (10 per group) in whom changes of plasma potassium and calcium levels were determined and muscle fasciculations measured by an objective method. Serum electrolyte variations and the quantity and duration of muscle fasciculations were similar in all groups. None of the pretreatments administered had any adverse effect on the neuromuscular block induced by suxamethonium.

Five non-depolarizing muscle relaxants in precurarization

Five different non-depolarizing muscle relaxants and a control solution of saline were studied as precurarization agents. Two hundred and twenty-two surgical patients (ASA I-II) were allocated in a double-blind fashion to one of the following groups: d-tubocurarine 0.05 mg/kg, alcuronium 0.03 mg/kg, pancuronium 0.01 mg/kg, gallamine 0.25 mg/kg, ORG NC-45 (vecuronium) 0.01 mg/kg and saline solution 0.005 ml/kg. Pretreatment was performed 4 min before administering a 1.5 mg/kg bolus of succinylcholine (SCh). Fasciculations, intubation conditions, duration of neuromuscular blockade after SCh, serum potassium changes and postoperative myalgias (in 60 patients) were recorded. All the drugs studied prevented fasciculations significantly (P less than 0.05) more than in the control group. d-Tubocurarine and alcuronium were superior to the others in this respect. Intubation conditions were best in the control and pancuronium groups, but there was no significant difference between the pancuronium and d-tubocurarine or between the d-tubocurarine and alcuronium groups. Pancuronium pretreatment prolonged the SCh block significantly, whereas other agents shortened the duration of the SCh block. The antagonism of the SCh block apparently also affected intubation conditions, although intubation remained satisfactory. A statistically significant rise in serum potassium level was measured only in the control and pancuronium groups. In the control and pancuronium groups, four patients out of 10 had postoperative myalgias, whereas in the other groups only one or none out of 10 had them (0/10 vs. 4/10; 0.10 greater than P greater than 0.05). In conclusion, d-tubocurarine and alcuronium seem to have advantages over pancuronium, ORG NC-45 and gallamine for precurarization.

Mixed neuromuscular block: the effect of precurarization

The effects of precurarisation, with small doses of pancuronium, curare or gallamine, on the neuromuscular blockade following suxamethonium, 1 mg/kg, were studied using train-of-four stimulation. The duration of the block was reduced by pretreatment with d-tubocurarine and gallamine but increased with pancuronium. The degree of competitive neuromuscular blockade, both after administration of the precurarising dose and at full recovery from suxamethonium was mild and was insufficient to be a cause of postoperative muscle weakness.

The influence of thiopentone and alfathesin on succinylcholine-induced fasciculations and myalgias

Thiopentone doses corresponding to 5.238 mg x kg-1, that is 2UD95 (UD95:unconsciousness dose 95) inhibit the intensity of succinylcholine-induced fasciculations compared with UD95. Alfathesin doses corresponding to 0.570 mg x kg-1, also 2UD95 (calculated as alphaxalone at a concentration of 9 mg/ml in alfathesin), do not have any greater effect on the degree of fasciculations compared to UD95. Furthermore, neither induction agent influences the incidence, distribution and duration of succinylcholine-induced myalgias. The inhibition of the degree of fasciculations caused by thiopentone is believed to be a consequence of a postsynaptic depressant effect of thiopentone at the neuromuscular junction. The evaluation of the degree of succinylcholine-induced fasciculations must take into consideration the dose of thiopentone administered at induction of anaesthesia.

Repeated doses of suxamethonium

Repeated sub-apnoeic doses of suxamethonium produce increased neuromuscular block in a hand muscle, measured by integrated electromyogram. The response to the initial dose varies widely between patients. More than 50% of patients showed evidence of non-depolarising block after one dose of suxamethonium. There was a variation between the response of the hand muscle and respiratory muscles.

The effect of lidocaine on succinylcholine-induced rise in intraocular pressure

The effect of lidocaine on the increase of intraocular pressure induced by succinylcholine was studied in patients 6 to 85 years of age. Three groups of patients were studied. One group of eight patients received lidocaine 1 mg.kg-1 before succinylcholine and a control group of ten patients did not have lidocaine. Anaesthesia was induced with thiopentone 5 mg.kg-1 and maintained with nitrous oxide 50 per cent with oxygen and halothane 1.0-1.5 per cent. The tracheae of all patients were intubated. Lidocaine in doses of 1.0 to 2.0 mg.kg-1 did not prevent transient rise in intraocular pressure following administration of succinylcholine and tracheal intubation.

Pharmacology and use of muscle relaxants in infants and children

Succinylcholine is a short-acting depolarizing neuromuscular blocker used to facilitate intubation; pancuronium is a longer-acting, nondepolarizing agent commonly employed to control ventilation in pediatric patients. The neuromuscular block produced by both drugs may be modified by patient age, acid-base and electrolyte status, body temperature, and drugs such as aminoglycoside antibiotics; adjustment in dose or in technique of administration may be required. Cardiovascular side-effects, primarily arrhythmias, are occasionally associated with the use of either agent. In contrast to that of succinylcholine, the paralysis from pancuronium is pharmacologically reversible with the combination of atropine and neostigmine.

Relation of precurarization to suxamethonium to provide ease of intubation and to prevent post-suxamethonium muscle pains

Tubocurarine 0.05 and 0.07 mg.kg-1, gallamine 0.1 and 0.2 mg.kg-1 and pancuronium 0.01 and 0.02 mg.kg-1 given three minutes before suxamethonium 1.0, 1.5 and 2 mg.kg-1 in groups of 10 patients each (total 210 patients) to compare ease of tracheal intubation and incidence of post-suxamethonium muscle pain. These were compared with a control group of suxamethonium 1.0, 1.5 and 2 mg.kg-1 given alone after thiopentone 5 mg.kg-1. On analysis, tubocurarine 0.07 mg.kg-1 and suxamethonium 2 mg.kg-1 was the ideal combination with the best intubation conditions and the lowest incidence of post-suxamethonium muscle pains. The second best combination was gallamine 0.2 mg.kg-1 and suxamethonium 2 mg.kg-1. Pancuronium 0.01 mg.kg-1 and 0.02 mg.kg-1 in combination with suxamethonium 2 mg.kg-1 were satisfactory, although less efficient than the combination with either tubocurarine or gallamine.

Dantrolene and suxamethonium. The effect of pre-operative dantrolene on the action of suxamethonium

A single oral dose of dantrolene (100--150 mg) given at least 2 hr pre-operatively has been found to reduce significantly the strength of muscular fasciculations, the hyperkalaemia and the incidence of muscle pains following suxamethonium (from 56 to 4%) in a series of forty-eight patients compared with controls. The biceps EMG of the fasciculations was unchanged by dantrolene; the incidence of troublesome side effects was low (9%) and there did not appear to be any alteration in the duration of action of suxamethonium.

Some aspects of ocular function after precurarization

Small doses of nondepolarizing relaxants are often recommended as prior medication to suxamethonium in order to avoid or attenuate the side effects elicited by the latter drug. After D-tubocurarine (0.05 mg/kg b.w. and 0.075 mg/kg b.w.) in unmedicated volunteers, a dose-dependent recession of the monocular near point of accomodation was recorded. This recession, which parallelled the decrease in grip strength, was 4 cm and 9 cm, respectively. The same doses evoked an exophoria of 14 and 17 prism diopters, respectively. Intraocular pressure was significantly lowered by D-tubocurarine 0.05 mg/kg b.w., from 2.01 kPa (15.1 mmHg) to 1.64 kPa (12.3 mmHg), and by pancuronium 0.015 mg/kg b.w. from 1.90 kPa (14.3 mmHg) to 1.44 kPa (10.8 mmHg). The decreases lasted for 7 min. Gallamine 0.3 mg/kg b.w. also decreased intraocular pressure, but to a lesser degree, and with statistical significance only during the fourth minute after administration. Relaxation of extraocular muscles may change the slightly ovoid shape of the eyeball into a more spherical one, thereby inducing a fall in intraocular pressure and a recession of the near point of accommodation.

Anaesthesia for electroconvulsive therapy

The results of a prospective study of 3,500 Anaesthetics for electroconvulsive therapy is presented. Minimal differences were observed between thiopentone and methohexitone. Propanidid and Diazepam were found to be unsuitable induction agents. Other findings included minimal serum potassium elevation and a low incidence of post treatment muscle pains. The place of the single-handed operator and the place of unmodified electroconvulsive therapy is questioned as being unacceptable practice.

Intubating conditions with AH 8165 and suxamethoniun

Intubating conditions after AH 8165, 1times25 mg/kg, have been compared with those after suxamethonium 1 mg/kg in 240 patients. Patients were matched for physical fitness and intubating conditions were studied in different groups at 30, 45, 60 and 75 seconds after the relaxant. At all times suxamethonium produced a higher incidence of good relaxation of the vocal cords and the incidence of excellent overall intubating conditions was significantly higher with suxamethonium. It proved impossible to intubate eleven patients with AH 8165 at the chosen time but all patients receiving suxamethonium could be intubated.