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IMPLICATIONS: This study demonstrated that pretreatment of succinylcholine with rocuronium failed to decrease the incidence or the severity of postoperative myalgia. However, in most patients, pretreatment was associated with muscle weakness before loss of consciousness. Thus, there is no convincing evidence supporting routine pretreatment with succinylcholine.
BACKGROUND: Contracting muscle emits sounds. The purpose of this study was to compare the time course of muscular paralysis at the adductor pollicis muscle (AP) with use of acoustic myography and mechanomyography. METHODS: Thirteen elective surgery patients, American Society of Anesthesiologists physical status I, received rocuronium (0.6 mg/kg intravenously) as a bolus dose during general anesthesia. Force of AP was measured with use of a strain gauge, and sounds were recorded simultaneously with use of a small condenser microphone fixed on the palmar surface of the hand over the AP. Supramaximal stimulation was applied to the ulnar nerve at 0.1 Hz for 45-60 min. In seven patients, the response to train-of-four stimulation was also recorded during recovery. RESULTS: Force and sounds both were equally sensitive in measuring maximum block. The relation between sound and force was curvilinear, with good agreement near 0 and 100% and acoustic response exceeding mechanical response at intermediate levels of block. The acoustic signal had a slower onset and a faster recovery than the force response. The fade response of sound to train-of-four stimulation also recovered faster than that of force. CONCLUSION: Acoustic myography is an alternative method to monitor muscular paralysis that is easy to set up and applicable to most superficial muscles. However, the time course of relaxation at AP using acoustic myography differs from the time course of force relaxation. Therefore, these two methods are not equivalent when applied to AP.
BACKGROUND: Conventional supine emergence in patients undergoing prone lumbar surgery frequently results in tachycardia, hypertension, coughing, and loss of monitoring as the patient is rolled supine. The prone position might facilitate a smoother emergence because the patient is not disturbed. No data describe this technique. METHODS: Fifty patients were anesthetized with fentanyl, nitrous oxide, isoflurane, and rocuronium. By the conclusion of surgery, all patients achieved spontaneous ventilation and full reversal of neuromuscular blockade in the prone position, as the volatile anesthetic level was reduced. Baseline heart rate and mean arterial pressure were recorded. Patients were then randomized at time 0 to the supine (n = 24) or prone (n = 21) position as 100% oxygen was administered. Patients in the supine position were then rolled over, while those in the prone position remained undisturbed. Heart rate, mean arterial pressure, and coughs were recorded until extubation. Tracheas were extubated on eye opening or purposeful behavior. RESULTS: When compared with the supine group, prone patients had significantly less increase in heart rate (P = 0.0003, maximum increase 9.3 vs. 25 beats/min), less increase in mean arterial pressure (P = 0.0063, maximum increase 4.8 vs. 19 mmHg), less coughing (P = 0.0004, 7.0 vs. 23 coughs), and fewer monitor disconnections (P < 0.0001). Time to extubation from time 0 was similar (4.0 vs. 3.7 min, prone vs. supine). No one required airway rescue. There was no significant difference in need for restraint (three prone, four supine). CONCLUSIONS: Prone emergence and extubation is associated with less hemodynamic stimulation, less coughing, and less disruption of monitors, without specifically observed adverse effects, when compared with conventional supine techniques.
BACKGROUND: Residual neuromuscular blockade remains a problem even after short surgical procedures. The train-of-four (TOF) ratio at the adductor pollicis required to avoid residual paralysis is now considered to be at least 0.9. The incidence of residual paralysis using this new threshold is not known, especially after a single intubating dose of intermediate-duration nondepolarizing relaxant. Therefore, the aim of the study was to determine the incidence of residual paralysis in the postanesthesia care unit after a single intubating dose of twice the ED(95) of a nondepolarizing muscle relaxant with an intermediate duration of action. METHODS: Five hundred twenty-six patients were enrolled. They received a single dose of vecuronium, rocuronium, or atracurium to facilitate tracheal intubation and received no more relaxant thereafter. Neuromuscular blockade was not reversed at the end of the procedure. On arrival in the postanesthesia care unit, the TOF ratio was measured at the adductor pollicis, using acceleromyography. Head lift, tongue depressor test, and manual assessment of TOF and DBS fade were also performed. The time delay between the injection of muscle relaxant and quantitative measurement of neuromuscular blockade was calculated from computerized anesthetic records. RESULTS: The TOF ratios less than 0.7 and 0.9 were observed in 16% and 45% of the patients, respectively. Two hundred thirty-nine patients were tested 2 h or more after the administration of the muscle relaxant. Ten percent of these patients had a TOF ratio less than 0.7, and 37% had a TOF ratio less than 0.9. Clinical tests (head lift and tongue depressor) and manual assessment of fade showed a poor sensitivity (11-14%) to detect residual blockade (TOF < 0.9). CONCLUSION: After a single dose of intermediate-duration muscle relaxant and no reversal, residual paralysis is common, even more than 2 h after the administration of muscle relaxant. Quantitative measurement of neuromuscular transmission is the only recommended method to diagnose residual block.
BACKGROUND: Residual paralysis increases the risk of pulmonary complications but is difficult to detect. To test the hypothesis that accelerometry predicts effects of residual paralysis on pulmonary and upper airway function, the authors related tests of pulmonary and pharyngeal function to accelerometry of adductor pollicis muscle in 12 partially paralyzed volunteers. METHODS: Rocuronium (0.01 mg/kg + 2-10 microg x kg-1 x min-1) was administered to maintain train-of-four (TOF) ratios (assessed every 15 s) of approximately 0.5 and 0.8 over a period of more than 5 min. The authors evaluated pharyngeal and facial muscle functions during steady state relaxation and performed spirometric measurements every 5 min until recovery. Upper airway obstruction was defined as a mean ratio of expiratory and inspiratory flow at 50% of vital capacity of greater than 1. The TOF ratio associated with "acceptable" pulmonary recovery (forced vital capacity and forced inspiratory volume in 1 s of > or =90% of baseline) was calculated using a linear regression model. RESULTS: At peak blockade (TOF ratio 0.5 +/- 0.16), forced inspiratory flow was impaired (53 +/- 19%) to a greater degree than forced expiratory flow (75 +/- 20%) with a mean ratio of expiratory and inspiratory flow at 50% of vital capacity of 1.18 +/- 0.6. Upper airway obstruction, observed in 8 of 12 volunteers, paralleled an impaired ability to swallow reported by 10 of 12 volunteers. In contrast, all volunteers except one could sustain a head lift for more than 5 s. The authors calculated that a mean TOF ratio of 0.56 (95% confidence interval, 0.22-0.71) predicts "acceptable" recovery of forced vital capacity, whereas forced inspiratory volume in 1 s was impaired until a TOF ratio of 0.95 (0.82-1.18) was reached. A 100% recovery of TOF ratio predicts an acceptable recovery of forced vital capacity, forced inspiratory volume in 1 s, and mean ratio of expiratory and inspiratory flow at 50% of vital capacity in 93%, 73%, and 88% of measurements (calculated negative predictive values), respectively. CONCLUSION: Impaired inspiratory flow and upper airway obstruction frequently occur during minimal neuromuscular blockade (TOF ratio 0.8), and extubation may put the patient at risk. Although a TOF ratio of unity predicts a high probability of adequate recovery from neuromuscular blockade, respiratory function can still be impaired.
BACKGROUND: The use of nondepolarizing neuromuscular blocking drugs (NDNMBDs) via continuous infusion in the intensive care unit (ICU) is gaining in popularity. Several new NDNMBDs have been developed recently; these drugs vary in their elimination, metabolism, and half-lives. METHODS: A review of the recent English language literature was done, with those articles relevant to the ICU being incorporated into this paper. RESULTS: The six most frequently used NDNMBDs, consisting of atracurium, cisatracurium, doxacurlum, pancuronium, rocuronium, and vecuronium, were reviewed. The neuromuscular junction and impulse transmission, clinical monitoring, clinical pharmacology, the elimination and metabolism, the adverse reactions, and the drug interactions of these NDNMBDs are reviewed. CONCLUSIONS: The use of NDNMBDs is progressively increasing in ICUs. Proper understanding of normal neuromuscular physiology, clinical pharmacology, and drug interactions is essential to optimize patient care and to minimize the risk of adverse reactions.
PURPOSE OF REVIEW: Rapid sequence intubation is the method of choice for intubation of the emergency department patient. The purpose of the present review is to address several controversies pertaining to emergency department rapid sequence intubation of children. RECENT FINDINGS: The topics covered in this review include the determination of the appropriate clinician to perform emergency department intubation, the use of atropine and lidocaine as premedications, the choice of sedative agents depending upon the clinical scenario, and the choice of neuromuscular blockade agent. Concerning these topics: The literature supports that emergency department physicians, with appropriate training, successfully perform intubation in most patients. Limited data exist to determine the appropriate use of atropine and lidocaine for rapid sequence intubation. Etomidate has clearly become a preferred sedative for rapid sequence intubation with a low risk of cardiovascular side effects. Thiopental and propofol may more readily provide adequate sedation as compared with etomidate but both have the potential to reduce blood pressure. Succinylcholine arguably remains the preferred neuromuscular blockade agent for rapid sequence intubation in most children. The side effects of succinylcholine occur in relatively predictable circumstances. Rocuronium is a commonly used nondepolarizing paralytic agent but its prolonged duration of action must be weighed against the risk of side effects associated with succinylcholine. SUMMARY: Though more research is needed, the available data allow for the development of protocols that will result in a rational, scenario-based approach to rapid sequence intubation in children.
BACKGROUND: The purpose of this study was to evaluate the effect of paramedic-administered neuromuscular blocking agents as part of a rapid-sequence intubation (RSI) protocol on successful intubation of severely head-injured patients in a large, urban prehospital system. METHODS: Adult head-injured patients were prospectively enrolled over 1 year using these inclusion criteria: Glasgow Coma Scale (GCS) score of 3 to 8, transport time > 10 minutes, and inability to intubate without RSI. Midazolam and succinylcholine were administered before laryngoscopy; rocuronium was given after tube placement was confirmed using capnometry, syringe aspiration, and pulse oximetry. The Combitube was used as a salvage airway device. All adult trauma victims with a GCS score of 3 to 8 were identified during the first 12 months of the study as the trial cohort and from the preceding 12 months as the control cohort. The trial and control cohorts were compared with regard to demographic data, mechanism of injury, initial vital signs, and GCS scores. The primary outcome measure was intubation success, defined as insertion of either an endotracheal tube or a Combitube, with patients stratified by GCS score. RESULTS: The trial cohort (n = 249) and control cohort (n = 189) were similar with regard to demographic data, mechanism of injury, and initial vital signs and GCS scores. Intubation success rates increased significantly during the trial period for all patients and when stratified into GCS score of 3 and GCS score of 4 to 8. The percentage of patients intubated without neuromuscular blocking agents actually increased during the trial period. Although the number of intubations by helicopter flight crews decreased during the trial, the overall use of aeromedical resources did not change. CONCLUSION: Paramedic-administered neuromuscular blockade as part of an RSI protocol improves intubation success in a large, urban prehospital system.
BACKGROUND: Accelerometry (ACM) of adductor pollicis muscle has been used for monitoring of neuromuscular blockade but its validity compared with the gold standard, mechanomyography (MMG), has been questioned. During neuromuscular blockade we compared these methods and we assessed pulmonary function. METHODS: In awake partially paralyzed volunteers we spirometrically assessed pulmonary function every 5 min until recovery. Rocuronium (0.01 mg kg(-1) + 2-10 microg kg(-1) min(-1)) was administered to maintain train-of-four (TOF)-ratios (assessed every 15 s) of approximately 0.5 and 0.8 over a period of more than 5 min. The TOF-ratio associated with 'acceptable' pulmonary recovery [forced vital capacity (FVC) and forced inspiratory volume in 1 s (FIV1) of > or =90% of baseline] was calculated using a linear regression model. During 5-min periods of repetitive nerve stimulation we compared the squared residuals of the FVC and FIV1 estimates from TOFACM vs. TOFMMG, and compared variance of values derived from ACM and MMG using Wilcoxon's test. RESULTS: Limits of agreement of TOF-ratio derived from ACM and MMG were wide [0.15+/-0.016 (SD)], and variability of TOFACM exceeded that of TOFMMG[variance: 77+/-105 vs. 51+/-55% (P<0.01)]. Calculated TOF(ACM) and TOFMMG ratios of 0.56 (0.22-0.71) [mean (95%CI) and 0.6 (0.28-0.74)], respectively, predict 'acceptable' (90%) recovery of FVC while FIV1 remains impaired until TOF-ratios of 0.91 (0.82-1.07) and 0.95 (0.82-1.18), respectively. In turn, TOFMMG (TOFACM) of unity predicted 'acceptable' recovery of FVC and FIV1 in 94 (93) % and 68 (73) % of measurements, respectively. CONCLUSIONS: Accelerometry predicts effects of relaxation on pulmonary function as valid as the gold standard mechanomyography. We recommend that recovery of TOF ratio to 0.9-1.0 should be used as an indication of sufficient neuromuscular recovery in daily practice.
BACKGROUND: The effect of different opioids on postoperative nausea and vomiting (PONV) has not been conclusively determined yet, thus the aim of this study was to compare the incidence of PONV in propofol-anaesthetized patients receiving either fentanyl or remifentanil as opioid supplement. METHODS: Sixty ASA physical status I and II patients scheduled for plastic surgery gave their written informed consent for this prospective, randomized, double-blind study. Anaesthesia was induced with propofol, rocuronium and fentanyl (n = 30; 2 microg kg(-1)) or remifentanil (n = 30; 1 microg kg(-1)). After tracheal intubation, anaesthesia was maintained with propofol, oxygen in air and an infusion of the opioid studied, which was modified according to clinical criteria. Baseline postoperative analgesia was achieved with intravenous propacetamol + metamizol. Intravenous morphine was given if visual analogic scale (VAS) for pain was > or = 4 (scale 0-10) and metoclopramide was administered if a patient presented > or = 2 PONV episodes (nausea or vomiting) in less than 30 min. Postoperatively (2, 12 and 24 h), we registered VAS, rescue morphine consumption, number of patients with episodes of PONV and number of patients requiring metoclopramide. P < 0.05 was considered significant. RESULTS: There were no significant differences between groups in the demographic parameters, ASA physical status, propofol dose, VAS, and rescue morphine requirements. Fourteen patients in the fentanyl group and four in the remifentanil group presented PONV episodes 2-12 h postoperative hours' interval; (P < 0.05). Ten patients in the fentanyl group and four in the remifentanil group presented vomiting episodes in the same period (P < 0.05); and eight patients in the fentanyl group and one in the remifentanil group required metoclopramide; (P < 0.05). The number of postoperative PONV episodes were low, both in the 0-2-h period (n = 2 vs. n = 1, fentanyl and remifentanil, respectively) and in the 12-24-h period (n = 3 vs. n = 1). CONCLUSION: Propofol + fentanyl anaesthesia resulted in a higher incidence of PONV and requirements of antiemetic drugs in the period between 2 and 12 postoperative hours compared with propofol + remifentanil, in patients undergoing plastic surgery.
Four new nondepolarising muscle relaxants, pipecuronium bromide, doxacurium chloride, mivacurium chloride and Org 9426 (rocuronium) offer alternatives to the established agents atracurium besilate and vecuronium bromide. Pipecuronium and Org 9426 are steroidal compounds, the latter being a monoquaternary agent, whereas doxacurium and mivacurium are bisquaternary benzylisoquinolinium compounds. Pipecuronium and doxacurium have a relatively slow onset and a long duration of action. Pipecuronium produces maximum block in 3 to 6 min when given in a dose of 45 to 80 micrograms/kg, and a duration of clinical relaxation of between 40 and 110 min. Doxacurium is more potent, but is the least rapid and the longest acting relaxant currently available. When administered in doses of 37 to 80 micrograms/kg, it produces maximum block within 3.5 to 10 min, with a duration of clinical relaxation of 77 to 164 min. The advantage of both pipecuronium and doxacurium is their cardiovascular stability. Both agents are primarily eliminated via the kidneys and both have now been licensed for use in the US. Mivacurium is a muscle relaxant with a short duration of action. When administered in doses of 0.1 to 0.25 mg/kg it produces maximum block in 2 to 4 min, but the duration of clinical relaxation is less than 20 min. Higher doses which could induce a faster neuromuscular block are unfortunately associated with some histamine liberation. The drug is metabolised by plasma cholinesterase. Mivacurium has also been licensed for use in the US. Org 9426 is an agent with a rapid onset but an intermediate duration of action. A dose of 0.5 to 0.6 mg/kg induces maximum block in about 1.5 min and has a duration of clinical relaxation of about 30 min. The rapid onset of effect could be useful for early intubation as an alternative to suxamethonium chloride. However, much more clinical experience is needed with this agent, particularly with regard to duration of action of larger doses and occurrence of side effects. The drug is mainly eliminated via the liver.
Rapid sequence induction (RSI) for intubation using neuromuscular blockade (NMB) is the most common method of achieving emergent tracheal intubation.(1) The ideal muscle relaxant for RSI would have four characteristics: a rapid onset to minimize the risk of aspiration and hypoxia, a rapid recovery to facilitate the return of ventilation if intubation proves difficult, minimal hemodynamic effects, and minimal systemic effects.(2) However, the ideal drug has yet to be found or created, so succinylcholine has been widely used for more than 40 years as a muscle relaxant in patients with full stomachs or who require emergent intubation.(3,4) Recently, rocuronium has received consideration as an alternative.(1,4) This article discusses both agents.
Neuromuscular blocking agents are used as adjuvants in day case anaesthesia to facilitate tracheal intubation and/or surgery. Although the majority of day case procedures are performed without the use of neuromuscular blocking agents, there are procedures, such as laparoscopic surgery, microsurgery, open eye surgery, some ear, nose and throat procedures and some paediatric procedures, which may require neuromuscular blockade. The characteristics of an ideal neuromuscular blocking agent for day case surgery are a short onset, a short clinical duration and a short recovery time, with or without reversal. It should also lack histamine release, provide haemodynamic stability, and be competitively priced. This paper reviews the neuromuscular blocking agents currently available and used, such as succinylcholine and mivacurium, low doses of an intermediate-acting neuromuscular block, such as rocuronium and the recently introduced rapacuronium. Their advantages and disadvantages are described and discussed, with special reference to the needs of day case surgery. Rapacuronium offers certain benefits compared with the currently available neuromuscular blocking agents for day care anaesthesia.
BACKGROUND: To evaluate a protocol for rapid sequence intubation (RSI) for pediatric patients in a Level 1 trauma center. MATERIAL/METHODS: Retrospective review of prospectively gathered Continuing Quality Improvement (CQI) data at an inner city Level 1 trauma center with an emergency medicine residency program. Protocols for RSI were established prior to initiating the study. All pediatric intubations at the center from February 1996 to February 2000 were included. Statistical analysis included descriptive statistics for categorical data and Chi-square for comparisons between groups. RESULTS: Over the 4-year study period there were 83 pediatric intubations ranging in age from 18 months to 17 years; mean age 8.6. All had data collected at the time of intubation. There were 20 (24%) females and 62 (76%) males (p<0.001). Reasons for intubation were related to trauma in 71 (86%) and medical reasons in 12 (14%) (p<0.001). Of the trauma intubations 7 (10%) were for gunshot wounds, 39 (55%) were secondary to MVCs, and the remainder (25; 35%) were from assaults, falls, and closed head injuries. The non-trauma intubations were for smoke inhalation, overdose, seizure, HIV related complications, eclampsia, and near drowning. Intubations were successful with one attempt in 65 (78%) cases. No surgical airways were necessary. Rocuronium was used in 4 cases. Protocol deviations did not lead to complications. CONCLUSIONS: This protocol based pediatric rapid sequence intubation method worked well in an EM residency program. More intubations were in males and more were necessary due to trauma in this group.
The electromyographic and hemodynamic profile and side effects of the new nondepolarizing myorelaxants Mivacurium chloride (Mivacron), Cisathracurium besilate (Nimbex), Rocuronium bromide (Esmerone) were studied in 117 adult patients. All the test myorelaxants as bolus or infusion in a dose of 3.ED95 were found to be effective in creating adequate conditions for tracheal intubation and neuromuscular block (NMB) maintenance during operations on the coronary arteries and cardiac vales under extracorporeal circulation. In terms of the onset rate of NMB, Esmerone is the drug of choice for tracheal intubation. Esmerone and Nimbex in a dose of 3.ED95 did not produce a noticeable hemodynamic effect. The former was found to have a slight vagolytic effect. When rapidly injected as bolus, Mivacron caused a significant decrease in blood pressure and heart rate by 10-12%. Based on a comprehensive study, the authors have scientifically substantiated principles in the choice of nondepolarizing myorelaxants in cardiac surgical patients in relation to the baseline hemodynamic values, the stage of an operation, and the duration of artificial pulmonary ventilation.
In a little over 10 years, six new muscle relaxants have been introduced in clinical practice. The first two, intermediate-duration vecuronium and atracurium, were outstanding drugs and clearly an advance over the earlier, longer-acting drugs. With their introduction, the phenomenon of "recurarization" largely disappeared. The next two, long-acting doxacurium and pipecuronium, were relics of an earlier era and have made little clinical impact. Mivacurium created a new class, the short-acting nondepolarizing relaxant, and caused succinylcholine to be reclassified as an ultra-short-acting drug. However, mivacurium has neither the rapid onset nor the ultra-short duration of succinylcholine. Rocuronium is the first nondepolarizing relaxant with an onset approaching that of succinylcholine. It is likely that we will see the introduction of at least two more drugs, Org 9487 and 51W89, by the end of this decade, and the goal of developing a nondepolarizing relaxant that is a complete replacement for succinylcholine may not be too far in the future.
The development of new non-depolarizing neuromuscular blocking drugs starting with the introduction of the intermediate-acting agents atracurium and vecuronium has made it possible to avoid the use of succinylcholine for elective cases. Recently 4 new drugs have become available; the short-acting mivacurium, the intermediate-acting rocuronium and the 2 long-acting drugs doxacurium and pipecuronium. The pharmacokinetic and pharmacodynamic profile of these drugs are reviewed in this paper.
The introduction of each new muscle relaxant has advanced anaesthetic practice by trying to meet some perceived deficiency in the existing therapeutic armamentarium. Anaesthesiologists need agents which are appropriate to the duration of surgery: they prefer agents which are not subject to drug interaction, have no effect on cardiovascular function, which do not depend significantly on renal excretion, which are easy to reverse, and which have a rapid onset of action. In certain circumstances one of these requirements becomes overridingly important. The latest new addition, rocuronium, fills the gap for an agent with rapid onset while lacking the potentially adverse features of suxamethonium, retaining a medium duration of action and meeting the other requirements set out above as well as any existing agent.