Administration Of Neuromuscular Blocking Drugs Research Articles

Comparative performance of stimpod electromyography with mechanomyography for quantitative neuromuscular blockade monitoring.

The purpose of this study was to compare the Stimpod electromyograph neuromuscular blockade monitor to mechanomyography, which is widely considered to be the reference standard. The Stimpod electromyograph was used with its designated electrode array on the same hand as the mechanomyograph. Pairs of train-of-four measurements were recorded every 0.5-2min. When the train-of-four count was zero on the electromyograph monitor, pairs of post tetanic count measurements were recorded every 2.5min, instead of train-of-four measurements. Measurements were recorded from immediately after induction of anesthesia until just before emergence. Stimulation current was set to 60 mA with a duration of 200 microsec. The mechanomyography recording system recorded each twitch waveform for analysis. High resolution electromyograph waveforms were also recorded using a datalogger accessory provided by the manufacturer, facilitating inspection of individual waveforms. The administration of neuromuscular blocking drugs was left up to the discretion of the anesthesia care team. Twenty-three patients contributed 1,088 data pairs suitable for analysis. Bland-Altman analysis of 415 pairs of train-of-four ratios showed a bias of 0.028 and limits of agreement of -0.18 and 0.24. Two hundred seventy-three train-of-four count data pairs were compared by Cohen's quadratically weighted kappa which was calculated to be 0.44, indicating moderate agreement. Three hundred thirty-eight post tetanic count data pairs were compared by Cohen's quadradically weighted kappa which was calculated to be 0.80, indicating substantial agreement. The electromyograph produced results that were comparable to the mechanomyograph.

Facemask ventilation and vocal cord angle following neuromuscular blockade: a prospective observational study.

Numerous studies support the idea that neuromuscular blockade facilitates facemask ventilation after induction of anaesthesia. Although improved airway patency or pulmonary compliance and a resolution of laryngospasm have been suggested as possible causes, the exact mechanism remains unclear. We aimed to assess whether neuromuscular blockade improves facemask ventilation and to clarify whether this phenomenon is associated with the vocal cord angle. This prospective observational study included patients aged between 20 and 65 years scheduled for elective surgery under general anaesthesia. After induction of anaesthesia, patients' lungs were ventilated with pressure-controlled ventilation using a facemask. During facemask ventilation, a flexible bronchoscope was inserted through a self-sealing diaphragm at the elbow connector attached to the facemask and breathing circuit and positioned to allow a continuous view of the vocal cords. The mean tidal volume and vocal cord angle were measured before and after administration of neuromuscular blocking drugs. Of 108 patients, 100 completed the study. Mean (SD) tidal volume ((11.0 (3.9) ml.kg-1 vs. 13.6 (2.6) ml.kg-1 ; p < 0.001) and mean (SD) vocal cord angle (17° (10°) vs. 26° (5°); p < 0.001) increased significantly after neuromuscular blockade. The proportional increase in mean tidal volume after neuromuscular blockade was positively correlated with vocal cord angle (Spearman's ρ = 0.803; p < 0.001). In conclusion, neuromuscular blockade facilitated facemask ventilation, and the improvement was correlated with further opening of the vocal cords.

Erroneous neuraxial administration of neuromuscular blocking drugs: Clinical and human factors analysis.

Drug errors during neuraxial anaesthesia or analgesia are not well known. To review the clinical consequences associated with incorrect administration of neuromuscular blocking drugs (NMBDs) during spinal or epidural anaesthesia, and to investigate human factors and strategies available to help prevent such errors. A review of reports of neuraxial administration of NMBDs in humans. Published reports of errors involving NMBDs. We searched the period between 1965 and 2019. Error reports in any language. Nonneuraxial drug errors were excluded. We identified 20 reports involving seven different NMBDs inadvertently administered via the epidural or intrathecal routes. All patients developed systemic neuromuscular junction blockade. Fourteen errors occurred while patients were awake. The onset of action was delayed following epidural rocuronium and suxamethonium. The duration of action was prolonged following epidural administration of vecuronium, pancuronium, cisatracrium and suxamethonium. Five patients required emergency airway interventions. Intrethecal gallamine caused convulsions and muscle spasms migrating up the body. Syringe swap was the primary cause for the majority of errors and perceptual errors were the most common. Implementation of recommendations could have prevented the errors. Following the epidural injection of NMBDs the effects are delayed and prolonged. There was no serious morbidity reported following neuraxial administration of the NMBDs used in current practice. Perceptual errors resulting in incorrect syringe choice were the commonest cause. Four measures can be introduced to reduce such errors.

Comparison of Face Mask Ventilation before and after the Administration of Neuromuscular Blocking Drugs: A Prospective Study

Comparison of Face Mask Ventilation before and after the Administration of Neuromuscular Blocking Drugs: A Prospective Study

Intensive care unit-related generalized neuromuscular weakness due to critical illness polyneuropathy/myopathy in critically ill patients.

Thirty to fifty percent of critically ill patients admitted to the intensive care unit suffer from generalized neuromuscular weakness due to critical illness polyneuropathy, critical illness myopathy, or a combination of them, thus prolonging mechanical ventilation and their intensive care unit stay. A distinction between these syndromes and other neuromuscular abnormalities beginning either before or after ICU admission is necessary. These intensive care unit-related diseases are associated with both elevated mortality rates and increased morbidity rates. Generally, over 50 % of patients will completely recover. Most of them recover after 4-12 weeks, but some patients have been reported to keep on suffering from muscle weakness for at least 4 months. Prevention has a key role in the management of critical illness neuromuscular disorders, as no specific therapy has been suggested. Either prevention or aggressive treatment of sepsis can prevent critical illness polyneuropathy and critical illness myopathy. The dose and duration of the administration of neuromuscular blocking drugs should be limited, and their concurrent administration with corticosteroids should be avoided. Intensive insulin therapy has also been proven to reduce their incidence. Finally, early mobilization via active exercise or electrical muscle stimulation plays a significant role in their prevention.

Evaluation of changes in tidal volume during mask ventilation following administration of neuromuscular blocking drugs.

The practice of checking the ability to mask ventilate before administering neuromuscular blocking drugs remains controversial. We prospectively evaluated the changes in the expired tidal volume during pressure-controlled ventilation (two-handed mask ventilation technique) as a surrogate marker to assess the ease of mask ventilation following administration of rocuronium. After informed consent, 125 patients were anaesthetised using a standard induction technique consisting of fentanyl, propofol and rocuronium, with anaesthesia then maintained with isoflurane in oxygen. The mean (SD) expired tidal volume before administration of rocuronium increased by 61 (13) ml at 2 min following onset of neuromuscular block (p < 0.001). This supports the concept that neuromuscular blockade induced by rocuronium facilitates mask ventilation.

Assessing the Utility of the Utility Function

Over the last 40 years, anesthesiologists have incorporated a series of new pharmacologic concepts that give us a better understanding of how drugs behave when administered by intravenous bolus or infusion. Each of these concepts initially seemed arcane and theoretical, but most are now accepted as a fundamental part of anesthesia practice. For example, the rapid administration of neuromuscular blocking drugs produces effects that aren’t well-described by their plasma concentrations (after all, they don’t work in plasma). This discrepancy lead to the development of “pharmacokinetic-pharmacodynamic (PK-PD) modeling” and the concept of a hypothetical “biophase” or “effect compartment”.1,2 More than fifty years ago, clinicians noted that the recovery from opioid infusions had a poor correlation with the elimination half- life.3. This eventually lead to the development of the “context-sensitive half-time,” which describes the minutes required for a 50% decrement in plasma drug concentration after stopping infusions of varying durations.4–6 Traditional pharmacokinetics focused predominantly on drug elimination, but an understanding of anesthetic onset required models that described drug disposition from the moment of injection.7 Thus, the concept of recirculatory pharmacokinetic models, or “front-end kinetics” was introduced to anesthesiology.8 Subsequent to their introduction, these new concepts were validated through extensive additional investigation.

Sugammadex to rescue a ‘can't ventilate’ scenario in an anticipated difficult intubation: is it the answer?

Sugammadex to rescue a ‘can't ventilate’ scenario in an anticipated difficult intubation: is it the answer?

Reversal with Sugammadex in the Absence of Monitoring Did Not Preclude Residual Neuromuscular Block

In Japan, routine clinical care does not normally involve the use of a monitoring device to guide the administration of neuromuscular blocking drugs or their antagonists. Although most previous reports demonstrate that sugammadex offers more rapid and reliable antagonism from rocuronium-induced neuromuscular blockade, this advantage has not been confirmed in clinical settings when no neuromuscular monitoring is used. In this multicenter observational study, we sought to determine whether sugammadex reduces the incidence of postoperative residual weakness compared with neostigmine when the administration of rocuronium and its antagonists is not guided by neuromuscular monitoring. This study was conducted in two 5-month periods that preceded and followed the introduction of sugammadex into clinical practice in Japan. Five university-affiliated teaching hospitals participated in this study. Neostigmine was used to antagonize rocuronium-induced neuromuscular blockade in the first phase, and sugammadex was used in the second phase. The timing and doses of rocuronium, neostigmine, and sugammadex were determined by the attending anesthesiologists without the use of neuromuscular function monitoring devices. To ascertain the incidence of postoperative residual neuromuscular weakness, the train-of-four ratio (TOFR) was determined acceleromyographically after tracheal extubation. Since our practice also does not usually involve calibration and normalization of accelerographic responses, both TOFR <0.9 and TOFR <1.0 were used as the criteria for defining postoperative residual weakness. In the first phase, 109 patients received neostigmine (average dose 33 µg/kg) and 23 patients were considered (by clinical criteria) to have adequate recovery and did not receive neostigmine (spontaneous recovery group). In the second phase, 117 patients received sugammadex (average dose 2.7 mg/kg) for antagonism of rocuronium-induced blockade. The incidence (95% confidence interval) of TOFR <0.9 under spontaneous recovery, after neostigmine, and after sugammadex, was 13.0% (2.8%-33.6%), 23.9% (16.2%-33.0%), and 4.3% (1.7%-9.4%), respectively. The incidence (95% confidence interval) of TOFR <1.0 in these groups was 69.6% (47.1%-86.6%), 67.0% (57.3%-75.7%), and 46.2% (36.9%-55.6%), respectively. The use of sevoflurane in the neostigmine group and the short interval between the administration of the last doses of rocuronium and sugammadex were associated with a higher incidence of postoperative residual weakness. This study demonstrated that the risk of TOFR <0.9 after tracheal extubation after sugammadex remains as high as 9.4% in a clinical setting in which neuromuscular monitoring (objective or subjective) was not used. Our finding underscores the importance of neuromuscular monitoring even when sugammadex is used for antagonism of rocuronium-induced neuromuscular block.

Intraoperative Neuromuscular Monitoring Site and Residual Paralysis

Thilen, Stephan R.; Hansen, Bradley E.; Ramaiah, Ramesh; Kent, Christopher D.; Treggiari, Miriam M.; Bhananker, Sanjay M. Author Information

The incidence of intra-operative awareness in the UK: under the rate or under the radar?

The incidence of intra-operative awareness in the UK: under the rate or under the radar?

Intraoperative Neuromuscular Monitoring Site and Residual Paralysis

Residual paralysis is common after general anesthesia involving administration of neuromuscular blocking drugs (NMBDs). Management of NMBDs and reversal is frequently guided by train-of-four (TOF) monitoring. We hypothesized that monitoring of eye muscles is associated with more frequent residual paralysis than monitoring at the adductor pollicis. This prospective cohort study enrolled 180 patients scheduled for elective surgery with anticipated use of NMBDs. Collected variables included monitoring site, age, gender, weight, body mass index, American Society of Anesthesiologists physical status class, type and duration of surgery, type of NMBDs, last and total dose administered, TOF count at time of reversal, dose of neostigmine, and time interval between last dose of NMBDs to quantitative measurement. Upon postanesthesia care unit admission, we measured TOF ratios by acceleromyography at the adductor pollicis. Residual paralysis was defined as a TOF ratio less than 90%. Multivariable logistic regression was used to account for unbalances between the two groups and to adjust for covariates. 150 patients received NMBDs and were included in the analysis. Patients with intraoperative TOF monitoring of eye muscles had significantly greater incidence of residual paralysis than patients monitored at the adductor pollicis (P < 0.01). Residual paralysis was observed in 51/99 (52%) and 11/51 (22%) of patients, respectively. The crude odds ratio was 3.9 (95% CI: 1.8-8.4), and the adjusted odds ratio was 5.5 (95% CI: 2.1-14.5). Patients having qualitative TOF monitoring of eye muscles had a greater than 5-fold higher risk of postoperative residual paralysis than those monitored at the adductor pollicis.

Muscle wasting in animal models of severe illness

Muscle wasting is a serious complication of various clinical conditions that significantly worsens the prognosis of the illnesses. Clinically relevant models of muscle wasting are essential for understanding its pathogenesis and for selective preclinical testing of potential therapeutic agents. The data presented here indicate that muscle wasting has been well characterized in rat models of sepsis (endotoxaemia, and caecal ligation and puncture), in rat models of chronic renal failure (partial nephrectomy), in animal models of intensive care unit patients (corticosteroid treatment combined with peripheral denervation or with administration of neuromuscular blocking drugs) and in murine and rat models of cancer (tumour cell transplantation). There is a need to explore genetically engineered mouse models of cancer. The degree of protein degradation in skeletal muscle is not well characterized in animal models of liver cirrhosis, chronic heart failure and chronic obstructive pulmonary disease. The major difficulties with all models are standardization and high variation in disease progression and a lack of reflection of clinical reality in some of the models. The translation of the information obtained by using these models to clinical practice may be problematic.

Desaturation following rapid sequence induction using succinylcholine vs. rocuronium in overweight patients

Rapid sequence induction may be associated with hypoxemia. The purpose of this study was to investigate the possible difference in desaturation during rapid sequence induction in overweight patients using either succinylcholine or rocuronium. Sixty patients with a body mass index (BMI) between 25 and 30 kg/m², American Society of Anesthesiologists class I or II, undergoing general anesthesia were randomly divided into a succinylcholine group and a rocuronium group. After a 3-min preoxygenation, patients received rapid sequence induction of general anesthesia with midazolum-fentanyl-propofol and succinylcholine (1.5 mg/kg) or rocuronium (0.9 mg/kg). Ventilation was not initiated until oxygen saturation declined to 92%. We measured the times when oxygen saturation reached 98%, 96%, 94% and 92%. Safe Apnea Time was defined as the time from administration of neuromuscular blocking drugs to oxygen saturation fell to 92%. The recovery period was defined as the time from initiation of ventilation until oxygen saturation was 97%. Arterial blood gases were taken at baseline, after preoxygenation and at 92% oxygen saturation. The mean Safe Apnea Time (95% CI) was 283 (257-309) s in succinylcholine vs. 329 (303-356) s in rocuronium (P=0.01). The mean recovery period (95% CI) was 43 (39-48) s in succinylcholine vs. 36 (33-38) s in rocuronium (P=0.002). Blood gas analysis showed no difference between the two groups. Succinylcholine was associated with a significantly more rapid desaturation and longer recovery of oxygen saturation than rocuronium during rapid sequence induction in overweight patients.

Train of Four Responses in Paretic Limbs

Quadriplegic patients pose difficulty for neuromuscular monitoring owing to nonavailability of accessible normal muscle. It is known that train of four responses (T4/T1 ratio) was exaggerated in paretic limbs. However, no studies have quantified the exaggeration at different degrees of block. This study was undertaken to quantify the exaggeration of train of four responses in paretic limbs with increasing levels of block after the administration of neuromuscular blocking drugs. Nine patients with normal motor power (group N) and 9 patients with paraplegia (group P) were studied. The mean difference in T4/T1 ratio (95% CI) between upper limb and lower limbs in normal group at T4/T1 81-90, T4/T1 71-80, T4/T1 51-70, T4/T1 31-50, and T4/T1 0-30 were 8.9 (0.8 to 16.9), 11.6 (3.8 to 19.5), 5.1 (-8.6 to 18.8), 7.6 (-6.8 to 21.9), and 3.8 (-0.9 to 8.5) and in paraplegic group, 14.5 (7.6 to 21.5), 25.1 (13.9 to 36.4), 35.6 (27.5 to 43.7), 29.1 (15.4 to 42.7), and 60 (39.4 to 80.7), respectively. There was a statistically significant difference in the train of four responses between normal and paretic limbs at all levels of block except at T4/T1 81-90. There was a significant positive correlation between difference in the T4/T1 ratio between the upper and lower limbs and intensity of block in the paraplegic group but no correlation in the normal group. The observation that T4/T1 ratio enhancement in denervated limbs is dependent on depth of neuromuscular block may have future implications for monitoring and reversal of neuromuscular block in this patient population.

Muscle relaxation does not influence venous oxygen saturation during cardiopulmonary bypass

Study Objective To examine whether the omission of neuromuscular blocking drugs during cardiopulmonary bypass (CPB) is associated with increased anesthetic requirements, higher frequency of intraoperative movements, and lower venous oxygen saturation (SvO 2). Design Prospective, randomized study. Setting Large community hospital. Patients 30 ASA physical status III and IV patients scheduled for cardiac surgery. Interventions Patients were randomized to one of two groups: group 1 (n = 15) received a 3× ED 95 bolus dose of cisatracurium at induction and thereafter no more neuromuscular blocking drug; group 2 (n = 15) received a continuous infusion of cisatracurium during the entire procedure. Interventions Both groups received a standardized anesthetic with bispectral index–guided propofol target-controlled infusion and a remifentanil infusion steered by hemodynamic changes. Venous oxygen saturation was continuously determined during CPB. Measurements and Main Results Propofol consumption was 5.4 ± 1.7 and 4.4 ± 1.0 mg/(kg/h) in groups 1 and 2, respectively ( P = 0.07). Remifentanil consumption was 0.15 ± 0.05 and 0.17 ± 0.05 μg/(kg/min) in groups 1 and 2, respectively ( P = 0.19). In groups 1 and 2, no patient recalled any intraoperative phenomena; none moved or had diaphragmatic contractions. During CPB, SvO 2 was 81.3 ± 3.2% (76%-85%) in group 1 and 80.6 ± 3.1% (73%-85%) in group 2 ( P = 0.53). Conclusions Omitting the continuous administration of neuromuscular blocking drugs during CPB did not increase anesthetic requirements. No intraoperative movements occurred, nor was there decreased SvO 2.

Neuromuscular Blockade Monitoring Complicated by the Unknown Preoperative Cosmetic Use of Botulinum Toxin

The ever-increasing popularity of facial botulinum treatment underscores the importance of obtaining a complete and accurate history before administration of paralytic agents. We report a case of a man undergoing laparoscopy during general anesthesia with an unknown history of facial botulinum injections, and the inability to accurately assess level of paralysis using facial nerve stimulation.A 72-yr-old, 60-kg man with a preoperative diagnosis of small bowel obstruction was scheduled to undergo an exploratory laparoscopy. The patient’s medical history was significant for diverticulitis, which was treated with colon resection; hypertension; and coronary artery disease, which was treated with angioplasty 15 previously. There was no other systemic disease present. On physical examination, there were no abnormalities. After rapid sequence induction with 150 mg propofol and 100 mg succinylcholine, anesthesia was maintained using isoflurane and then desflurane. The patient received a total of 8 mg vecuronium during the remainder of the case for muscle relaxation. The surgeons performed lysis of adhesions, and the operation lasted approximately 2 h. Upon closing the abdominal fascia, the surgeon stated that the patient’s muscles were not relaxed, making closure difficult. Sixty minutes had elapsed since the last dose of vecuronium (2 mg) was administered. Using a peripheral nerve stimulator, train-of-four (TOF) was assessed at the orbicularis oculi muscles bilaterally, and no twitches were noted. The nerve stimulator leads were then placed over the ulnar nerve to assess recovery of the adductor pollicis muscle, and there was indeed recovery of TOF, with a ratio greater than 0.7. The patient was given a small dose of vecuronium, and only one twitch was subsequently observed. After the surgery was completed, there were three TOF visible twitches from the adductor pollicis muscle, and the paralysis was reversed with 5 mg neostigmine and 1 mg glycopyrrolate. The patient emerged from anesthesia smoothly and was extubated in the operating room. It was realized that the patient had appeared younger than his stated age, and it was then considered that the patient may have had cosmetic treatment, which would have affected the musculature of his face and possibly reduced the response to TOF stimulation. On postoperative questioning, the patient indeed confirmed a history of botulinum toxin injections to the upper facial muscles, 4 weeks before this surgery.In our case, the depth and recovery of neuromuscular blockade was assessed using TOF stimulation with a peripheral nerve stimulator. The patient’s use of botulinum toxin around the orbicularis oculi muscles interfered with accurate assessment of muscle paralysis. Normally, the orbicularis oculi muscle has a shorter latency and faster recovery to TOF ratio of 0.80, compared with the adductor pollicis muscle.1However, botulinum toxin had denervated the patient’s facial muscle fibers, and no twitches could be elicited from stimulation of the orbicularis oculi muscles. This was demonstrated by the simultaneous presence of four visible twitches at the adductor pollicis site after TOF stimulation. This case demonstrates that botulinum toxin injections may interfere with the monitoring of neuromuscular blockade. It may indicate a higher degree of neuromuscular block than is actually present. Botulinum toxin may lead to a significant flaccid paralysis for months after injection. The exponential growth in the use of botulinum toxin for cosmesis should prompt the anesthesiologist to inquire about the use of botulinum toxin in patients who appear significantly younger than their actual age. Possible courses of action would be to obtain a baseline TOF before administration of neuromuscular blocking drugs, and to check an alternate site if a deeper-than-expected block is observed.*The Mount Sinai Medical Center, New York, New York. steve.neustein@msnyuhealth.org

Does the Timing of Tracheal Intubation Based on Neuromuscular Monitoring Decrease Laryngeal Injury? A Randomized, Prospective, Controlled Trial

Vocal cord injuries (VCI) and postoperative hoarseness (PH) are common complications after general anesthesia. Poor muscle relaxation at the moment of tracheal intubation may result in VCI. There is a large interindividual variation in neuromuscular depression after administration of neuromuscular blocking drugs. Therefore, the optimal individual timing of tracheal intubation based on neuromuscular monitoring (monitoring) may decrease VCI. In this prospective trial, 60 patients were randomized into 2 groups: Monitoring group: tracheal intubation at maximum block based on monitoring after atracurium 0.5 mg/kg and 2-min group: tracheal intubation 2 min after injection of atracurium 0.5 mg/kg. Intubating conditions were evaluated with the Copenhagen score. VCI were examined by stroboscopy before and 24 and 72 h after surgery. PH was assessed at 24, 48, and 72 h after surgery by a standardized interview. Excellent intubating conditions were significantly increased in the monitoring group compared with the 2-min group: 8 versus 2 patients, respectively (P = 0.036). The incidence of PH between the study groups was comparable: 7 (monitoring) versus 8 patients (2-min) (P = 0.860). Similar findings were observed for VCI: 9 versus 5 patients; respectively (P = 0.268); type of VCI: thickening of the vocal cords: 8 (monitoring) versus 5 (2-min) patients (P = 0.423), hematomas: 2 patients in each group (not significant). The present study demonstrated that neuromuscular monitoring improved endotracheal intubating conditions. However, tracheal intubation at maximum intensity of neuromuscular block was not associated with a decrease in vocal cord injuries.

Neuromuscular blocking agents: New insights and old controversies

T HE LAST ISSUE of Seminars in Anesthes ia totally devoted to muscle relaxants (vol 14, no 1) appeared in March of 1995. It may be argued that the 7 years that have passed since that publication have been relatively uneventful ones for clinicians with a special interest in neuromuscular blocking drugs. Cisatracurium (released in 1995) was a welcome addition to our armamentarium but not a radical advance from drugs already available. Rapacuronium, the only other blocker introduced since 1995, was withdrawn from the market in March 2001. Nevertheless, the last 7 years have seen several changes in our thinking about the clinical administration of neuromuscular blocking drugs. In the paragraphs that follow, I will focus on new information, continuing controversies, and changing standards of care that have emerged as we enter a new millennium.

An alternate method for estimating the dose-response relationships of neuromuscular blocking drugs.

Slopes of the dose-response relationships for all available neuromuscular blocking drugs appear to be essentially parallel and to approximate a log-dose/logit value of 4.75. We tested the possibility of estimating both 50% effective dose (ED(50)) and 95% effective dose (ED(95)) values from a single dose-response data point when that slope is postulated. We compared the ED(50) and ED(95) values of rocuronium and succinylcholine calculated by using traditional log-dose/logit regression analysis with the same values obtained by averaging individual estimates of potency as determined by using the Hill equation. After the induction of anesthesia (propofol/alfentanil), tracheal intubation was accomplished without the administration of neuromuscular blocking drugs. Anesthesia was maintained with nitrous oxide and propofol. The evoked electromyographic response to 0.10-Hz single stimuli was continuously recorded. After baseline stabilization, a single IV bolus of succinylcholine (0.08-0.26 mg/kg, n = 50) or rocuronium (0. 13-0.30 mg/kg, n = 40) was administered and the peak effect noted. By using log-dose/logit regression analysis, we calculated ED(50) and ED(95) values for rocuronium of 0.17 and 0.33 mg/kg and 0.14 and 0.27 mg/kg for succinylcholine. When potency was calculated from the Hill equation, the resultant ED(50) and ED(95) values did not differ by more than +/-4% from those obtained by using regression analysis. Averaging of single-dose estimates of neuromuscular potency provides a useful adjunct and reasonable alternative to conventional regression analysis.