Properties of fibres, endplates and acetylcholine receptors in the diaphragm, masseter, laryngeal, abdominal and limb muscles in the goat

Effect of Diabetes Mellitus Type 2 on Voice: A Systematic Review and Meta-Analysis

INTRODUCTION

Diabetes mellitus type 2 is a growing health concern that affects several systems in the body, among which is the phonatory apparatus. Voice may be affected in view of the high prevalence of myopathy and neuropathy in diseased subjects. The authors aimed to answer the following question: does type 2 diabetes have an effect on voice?

METHODS

The systematic review included search terms such as "speech, voice, larynx, glucose, diabetes, and hyperglycemia." The search strategy yielded 221 articles, only five of which satisfied the inclusion criteria. Articles were considered for inclusion using the PRISMA method. Analysis included 321 patients with type 2 diabetes mellitus and 171 controls. All studies included were case-control studies except for one study which was an observational cohort. Six parameters were chosen as endpoints for the systematic review and meta-analysis: the presence/absence of voice complaints, fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, and maximum phonation time.

RESULTS

There was no significant difference in the prevalence of voice complaints (i.e., hoarseness) between diabetic patients and control groups. There was also no significant difference in any of the acoustic and aerodynamic measures between patients with type 2 diabetes and controls. These findings can be ascribed to the high resilience of the laryngeal muscles to the adverse effect of systemic diseases.

CONCLUSION

There is no consensus in the literature that the prevalence of voice symptoms in diabetic patients is significantly higher than that reported in healthy subjects.

Effect of Vitamin D Deficiency on Voice: A Review of the Literature

OBJECTIVE

The purpose of this study is to review the current literature on the effect of hypovitaminosis D on voice.

STUDY DESIGN

Narrative review.

METHODS

The literature search from electronic databases included PubMed/MEDLINE, EMBASE, SCOPUS, and Google Scholar. Search terms included voice, voice quality, voice disorders, larynx, laryngology, acoustic analysis, vitamin D, calcitriol, cholecalciferol, vitamin D deficiency, and vitamin D insufficiency. All studies on patients with vitamin D deficiency, which included subjective and objective voice assessments, were reviewed.

RESULTS

A total of 39 studies were retrieved. Only four studies met the above-mentioned inclusion criteria and hence were included in this review. The total number of subjects analyzed was 466. The subjective voice outcome measures used were the Voice Handicap Index-10 (VHI-10), self-reported phonatory symptoms, and the GRBAS scale. Objective voice outcome measures included fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, maximum phonation time, and dysphonia severity index.

CONCLUSION

Vitamin D deficiency has no significant effect on laryngeal muscles. There was no statistically significant difference in VHI-10 score, self-reported dysphonia, perceptual voice evaluation scores, or any of the acoustic measures between those with or without vitamin D deficiency.

Comparison of onset of neuromuscular blockade with electromyographic and acceleromyographic monitoring: a prospective clinical trial

BACKGROUND

Reliable devices that quantitatively monitor the level of neuromuscular blockade after neuromuscular blocking agents' administration are crucial. Electromyography and acceleromyography are two monitoring modalities commonly used in clinical practice. The primary outcome of this study is to compare the onset of neuromuscular blockade, defined as a Train-Of-Four Count (TOFC) equal to 0, as measured by an electromyography-based device (TetraGraph) and an acceleromyography-based device (TOFscan). The secondary outcome was to compare intubating conditions when one of these two devices reached a TOFC equal to 0.

METHODS

One hundred adult patients scheduled for elective surgery requiring neuromuscular blockade were enrolled. Prior to induction of anesthesia, TetraGraph electrodes were placed over the forearm of patients' dominant/non-dominant hand based on randomization and TOFscan electrodes placed on the contralateral forearm. Intraoperative neuromuscular blocking agent dose was standardized to 0.5 mg.kg-1 of rocuronium. After baseline values were obtained, objective measurements were recorded every 20 seconds and intubation was performed using video laryngoscopy once either device displayed a TOFC = 0. The anesthesia provider was then surveyed about intubating conditions.

RESULTS

Baseline TetraGraph train-of-four ratios were higher than those obtained with TOFscan (Median: 1.02 [0.88, 1.20] vs. 1.00 [0.64, 1.01], respectively, p < 0.001). The time to reach a TOFC = 0 was significantly longer when measured with TetraGraph compared to TOFscan (Median: 160 [40, 900] vs. 120 [60, 300] seconds, respectively, p < 0.001). There was no significant difference in intubating conditions when either device was used to determine the timing of endotracheal intubation.

CONCLUSIONS

The onset of neuromuscular blockade was longer when measured with TetraGraph than TOFscan, and a train-of-four count of zero in either device was a useful indicator for adequate intubating conditions.

CLINICAL TRIAL NUMBER AND REGISTRY

URL NCT05120999, https://clinicaltrials.gov/ct2/show/NCT05120999.

Nicotinic acetylcholine receptor subunit expression in the gastrocnemius and in the orbicularis oris before and after facial nerve injury in rats

Objectives: To observe the expression of nicotinic acetylcholine receptor (AChR) subunits in normal orbicularis oris and gastrocnemius muscles and to explore the relationships between the expression of AChR subunits and the severity of facial nerve injury. Methods: Gene and protein expression of AChR subunits in the orbicularis oris and gastrocnemius muscles of male Sprague-Dawley rats was measured by reverse transcription polymerase chain reaction and western blotting, respectively, 1-90 days after graded facial nerve injury. Results: Expression of ε-AChR in the normal orbicularis oris was significantly higher than that in the gastrocnemius, whereas no γ subunit expression was observed. Expression of α, β, δ, ε, and γ subunits was upregulated in the orbicularis oris and was positively correlated with the degree of facial nerve injury. Discussion: We demonstrated the higher expression of the AChR subunits in the orbicularis oris, compared to gastrocnemius muscles. The differences in expression of these subunits between muscles innervated by the facial nerve and somatic nerves and the correlation of AChR subunit expression with the degree of facial nerve injury yield insights into the sensitivity to muscle relaxants during intraoperative facial nerve monitoring.

Sexual Dimorphism in Laryngeal Volumetric Measurements Using Magnetic Resonance Imaging

The objective of this study is to investigate the dimensional and volumetric measurements in the thyroarytenoid (TA) muscle in men and women using magnetic resonance imaging (MRI). The hypothesis is that there is a gender-related difference in these measurements. A retrospective chart review of 76 patients who underwent MRI of the neck at the American University of Beirut Medical Center was conducted. The dimension and volume of the right and left TA muscle were measured on axial and coronal planes short tau inversion recovery images. Male and female groups were compared with respect to demographic data and MRI findings using parametric and nonparametric tests. The mean length of the thyro-arytenoid muscle in males was larger than that in females on the right (males 2.44 [0.29] cm vs females 1.70 [0.22] cm) and on the left (males 2.50 [0.28] cm vs females 1.72 [0.24] cm) reaching statistical significance (P < .001). The mean width of the thyro-arytenoid muscle in males was larger than that in females on the right (males 0.68 [0.13] cm vs females 0.59 [0.11] cm) and on the left (males 0.68 [0.12] cm vs females 0.57 [0.12] cm) reaching statistical significance (P < .001). The mean height of the thyro-arytenoid muscle in males was larger than that in females on the right (males 1.05 [0.21] cm vs females 0.95 [0.12] cm) and on the left (males 1.05 [0.21] cm vs females 0.95 [0.12] cm) reaching statistical significance (P < .01 on the right and P < .05 on the left). The volume of the thyroarytenoid muscle in males was larger than that in females on the right (males 0.86 [0.25] mL vs females 0.48 [0.15] mL) and on the left (males 0.89 [0.27] mL vs females 0.48 [0.17] mL) reaching statistical significance (P < .001). The results of this investigation clearly indicate a significant difference in these measurements between men and women.

Effect of Vitamin D Deficiency on Voice

PURPOSE

The purpose of this article was to investigate the relationship between low level of vitamin D, phonatory symptoms, and acoustic findings.

METHOD

A total of 38 subjects presenting to the endocrinology clinic were enrolled in 2 groups: 19 with vitamin D deficiency who were not on treatment, and 19 with normal vitamin D level who were on treatment. Demographic data included age, gender, and history of smoking. All patients were asked about the presence or absence of dysphonia, degree of phonatory effort, and vocal fatigue. Acoustic analysis and perceptual evaluation using the grade, roughness, breathiness, asthenia, and strain scale were performed on all subjects.

RESULTS

The mean age of the total group was 47.29 ± 13.52 years. The difference in the mean and frequency of phonatory effort, vocal fatigue, and dysphonia, and in the mean of the acoustic variables, perceptual parameters, and the score of the Voice Handicap Index-10 was not statistically significant between patients with low vitamin D levels compared with controls.

CONCLUSION

The results of this study revealed no significant difference in the prevalence of phonatory symptoms in patients with vitamin D deficiency compared with patients with no vitamin D deficiency. A larger study is needed to substantiate the difference in the prevalence of phonatory systems between the 2 groups.

Differences in pharmacodynamic responses to rocuronium in normal or injured orbicularis oris are associated with expression of acetylcholine receptor subunits

Previous research has indicated that differences in sensitivities to muscle relaxants exist between facial nerve- and somatic nerve-innervated muscles. Here, we report that the 50% inhibitory concentration (IC50) values for rocuronium were significantly larger in the normal orbicularis oris than those in the gastrocnemius. Increased IC50 values and reduced twitch tension were observed after facial nerve injury. The normal orbicularis oris had a smaller muscle fiber cross-sectional area (CSA) and a larger ratio of endplate surface area (ESA) to muscle fiber CSA (ESA/CSA), but no difference was found in the density of nicotinic acetylcholine receptor (nAChR) subunits on endplates between normal orbicularis oris and gastrocnemius. Expression of the nAChR α1, β1, δ, ε, and γ subunits increased significantly on the postsynaptic membranes of endplates and extra-junctional muscle membranes after facial nerve injury. Our results suggest that facial nerve-innervated muscle was less sensitive than somatic nerve-innervated muscle, and the mechanisms underlying this result may be related to muscle fiber CSA and the ESA/CSA ratio, but not to the density of nAChR subunits on endplates. Facial nerve injury caused the resistance to neuromuscular blockers and reduced twitch tension, which was related to qualitative, quantitative, and locational changes in nAChR subunits.

Effect of vitamin D deficiency on the laryngo-pharyngeal tract

OBJECTIVE

To investigate the effect of vitamin D deficiency on the laryngopharyngeal tract.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary care center.

SUBJECTS AND METHODS

A total of 38 human subjects were prospectively recruited, equally divided into two groups. The Vitamin D deficiency group defined as 25-OH<25ng/dl and the control subjects with normal vitamin D level defined as 25-OH>25ng/dl. The presence and severity of vocal tract symptoms was assessed using the Vocal Tract Discomfort score.

RESULTS

There was no significant difference in vocal tract discomfort score for frequency and severity between patients with Vitamin D deficiency and patients with no vitamin D deficiency (p value 0.272). However there was a significant difference in the mean frequency of burning, aching, soreness and lump sensation (p value<0.05) in patients with vitamin D deficiency compared to those with no vitamin D deficiency. There was also a significant difference in the means of vocal tract severity symptoms, namely for burning and aching between patients with vitamin D deficiency compared to patients with no vitamin D deficiency (p value<0.05).

CONCLUSION

Subjects with vitamin D deficiency do not have a higher vocal tract discomfort score than subjects with no vitamin D deficiency. However the frequency and severity of certain vocal tract discomfort symptoms was higher and can be based hypothetically on the similarity in structure between the laryngopharyngeal complex and the musculoskeletal system.

Influence of oilseed supplement ranging in n-6/n-3 ratio on fatty acid composition and Δ5-, Δ6-desaturase protein expression in steer muscles

This study investigated effects of roasted or extruded oilseed supplementation ranging in n-6/n-3 ratios from 0.3 to 5.0 on the fatty acid composition and expression of delta-5 desaturase (Δ5d) and Δ6-desaturase (Δ6d) protein in commercial steer cheek (m. masseter) and diaphragm (pars costalis diaphragmatis) muscles. In general, the n-6/n-3 ratio of the diet had a subsequent effect on the muscle n-6/n-3 ratio (P < 0.05), with muscle 18:2n-6 and 18:3n-3 content relating to proportion of dietary soya bean and linseed (P < 0.01). Compared with canola, pure linseed and soya bean diets reduced 14:1c-9 and 16:1c-9 (P < 0.05) but increased 18:1t-11 and c-9,t-11 conjugated linoleic acid (CLA) content (P < 0.01). Oilseed processing had a minor influence but extruded oilseeds increase 18:1t-11 and c-9,t-11 CLA compared with roasted (P < 0.05). Polar lipid 18:3n-3 and n-3 long-chain polyunsaturated fatty acid (LC, ⩾20 carbons PUFA) derivative content increased in relation to dietary linseed supplementation in the diaphragm (P < 0.01), whereas only 18:3n-3 was increased in the cheek (P < 0.01). Protein expression did not differ between diets; however, in each muscle the Δ5d protein expression had a stronger association with the desaturase products rather than the precursors. The relationship between Δ5d protein expression and the muscle LC n-6/n-3 ratio was negative in both muscles (P < 0.05). The relationship between Δ6d protein expression and the LC n-6/n-3 ratio was positive in the cheek (P < 0.001) and negative in the diaphragm (P < 0.05). In conclusion, diet n-6/n-3 ratio affected muscle 18:2n-6 and 18:3n-3 deposition, whereas the Δ5d and Δ6d protein expression had some influence on the polar lipid LC-PUFA profile. Results reaffirm that processed oilseeds can be used to increase the proportion of fatty acids potentially beneficial for human health, by influencing the formation of LC-PUFA and reducing the n-6/n-3 ratio.

Differences in sensitivity to rocuronium among orbicularis oris muscles innervated by normal or damaged facial nerves and gastrocnemius muscle innervated by somatic nerve in rats: combined morphological and functional analyses

OBJECTIVES/HYPOTHESIS

To evaluate mechanisms of discrepant responses to the nondepolarizing muscle relaxant rocuronium among normal and injured facial nerve-innervated orbicularis oris and tibial nerve-innervated gastrocnemius, and to provide information for the proper use of muscle relaxants to balance evoked electromyography (EEMG) monitoring and immobility in general anesthesia.

STUDY DESIGN

Randomized controlled study.

METHODS

Right-sided facial nerve injury was induced by crush axotomy in 18 Sprague-Dawley rats. At different rocuronium concentrations, muscular tension amplitude (MTA) was determined in vitro for normal and injured facial nerve-innervated orbicularis oris and gastrocnemius; the number of unsaturated acetylcholine receptors (AChRs) at end plates was determined by (125) I-α-bungarotoxin staining followed with gamma spectroscopy. The morphological composition of muscle fibers was determined by histological examination.

RESULTS

Following rocuronium incubation, the percentage of MTA inhibition (MTAI%) of gastrocnemius was significantly higher than the corresponding values of orbicularis oris (P < .05), and the degree of saturation of AChR in gastrocnemius was significantly greater than that in orbicularis oris (P < .05). The baseline MTA and AChR density of injured-side orbicularis oris was significantly smaller than those of the normal side, whereas no significant difference was found regarding MTAI% and the degree of AChR saturation between the normal and injured side.

CONCLUSIONS

The affinity of AChR at end plates and different number of AChR per unit fiber cross-sectional area may be the mechanisms for differential sensitivities to neuromuscular blockers between facial nerve-innervated muscles and somatic nerve-innervated muscles. The lower EEMG responses in the impaired facial nerve-innervated muscles may result from the lower AChR density at end plates compared with the normal facial nerve-innervated muscles.

Influence of stimulus frequency on blockade induced by pancuronium and rocuronium: study on rats phrenic nerve-diaphragm preparation

PURPOSE: To evaluate the influence of two stimulation frequencies on the installation of neuromuscular blockade produced by pancuronium and rocuronium on the rat diaphragm. METHODS: Diaphragms were submitted to an indirect frequency stimulation of 0.1 and 1Hz (Groups I and II, respectively). Subgroups were formed (n=5) according to the neuromuscular blocker employed (pancuronium-2µg/ml and rocuronium-4µg/ml). The twitch height depression was evaluated at 5, 15 and 30 minutes after adding the neuromuscular blocker. RESULTS: The decrease in twitch height was greater (p<0.01) with a frequency of 1Hz at all time periods studied both in preparations that are blocked with pancuronium and in those that are blocked with rocuronium. CONCLUSION: The frequency of stimulation interferes significantly with the installation of neuromuscular blockade produced by pancuronium and rocuronium, since the reduction in amplitude of the rat diaphragm response was greater for 1Hz frequencies, at all periods studied.

Onset properties of mivacurium measured by mechanomyography depend on the twitch height of the adductor pollicis muscle

INTRODUCTION

The influence of the twitch height of the adductor pollicis muscle during baseline measurements on the pharmacodynamic parameters of mivacurium was prospectively evaluated.

PATIENTS AND METHODS

Fifty adult patients were anaesthetized with propofol and alfentanil. Neuromuscular function was monitored mechanomyographically by measuring the force of the adductor pollicis muscle following stimulation of the ulnar nerve. Following a stabilization period of 20 min, the individual twitch height of the adductor pollicis muscle was determined before a single bolus of mivacurium (75 microg kg-1) was administered. Patients were divided into two groups. The data of patients whose thumb adduction force was below the median value of all patients were the 'low force' group (9.1 +/- 1.4 N) and the data of all other patients were the 'high force' group (13.7 +/- 1.8 N).

RESULTS

In the 'high force' group, maximum neuromuscular blockade of mivacurium was deeper (0.97 +/- 0.05 vs. 0.93 +/- 0.06; P < 0.05) and onset faster (2.9 +/- 1.1 min vs. 4.0 +/- 1.2 min; P < 0.05). Neuromuscular recovery did not differ between the groups.

CONCLUSION

The different onset speeds reflect either different sensitivity to neuromuscular blocking agents with respect to patients' muscle power or a problem of the mechanomyographic measuring technique.

Effects of SZ1677, a new non-depolarizing steroidal neuromuscular blocking drug, and rocuronium on two laryngeal muscles and the anterior tibial muscle in guinea pigs

BACKGROUND

SZ1677 is a new neuromuscular blocking drug structurally related to rocuronium. We compared the effect of an ED(90) of SZ1677 (25 microg/kg) with that of rocuronium (100 microg/kg) in guinea pig laryngeal and peripheral muscles.

METHODS

Electromyography was used to quantify neuromuscular blockade at the posterior cricoarytenoid muscle, the thyroarytenoid muscle and the anterior tibial muscle after SZ1677 (n = 10) and rocuronium (n = 9).

RESULTS

Maximum neuromuscular blockade was similar after SZ1677 and rocuronium (83 +/- 11% vs. 89 +/- 11%; thyroarytenoid muscle: 91 +/- 8% vs. 97 +/- 3%; anterior tibial muscle: 91 +/- 15% vs. 96 +/- 3%, respectively). Onset time of neuromuscular blockade at the laryngeal muscles was similar for the two neuromuscular blocking drugs; it was shorter at the thyroarytenoid muscle (67 +/- 32 s vs. 42 +/- 40 s) than at the posterior cricoarytenoid muscle (101 +/- 26 s vs. 102 +/- 108 s). Onset time at the anterior tibial muscle was longer after SZ1677 (114 +/- 34 s) than after rocuronium (68 +/- 46 s); P < 0.05. Neuromuscular recovery was faster after SZ1677 (interval 25%-75%: posterior cricoarytenoid muscle: 222 +/- 66 s; thyroarytenoid muscle: 192 +/- 92 s; tibial muscle 149 +/- 55 s) than after rocuronium (450 +/- 148 and 464 +/- 183 s, 292 +/- 86 s, respectively); P < 0.05.

CONCLUSIONS

In guinea pigs, SZ1677 offers a rapid onset of neuromuscular blockade at a laryngeal adductor muscle with a shorter duration than rocuronium. Regardless of the drug used, the course of neuromuscular blockade differs not only between peripheral muscles and the larynx but also between antagonistic laryngeal muscles. The differences seem to be species specific.

Comparative evolution of muscular dystrophy in diaphragm, gastrocnemius and masseter muscles from old male mdx mice

X chromosome-linked muscular dystrophic mdx mouse lacks the sarcolemmal protein dystrophin and represents a genetic homologue of human Duchenne muscular dystrophy (DMD). The present study analysed some aspects of pathological processes such as fibrosis, frequency of centralized nuclei, presence of degenerative or regenerative fibres, expression of utrophin and associated protein complexes, and myosin heavy chain isoforms in three muscles [diaphragm (DIA), gastrocnemius (GTC) and masseter (MAS)] from old male mdx mice. All parameters investigated comparatively in these pathological muscles provided evidence that the MAS mdx muscle presents a slight deterioration pattern in comparison to that of DIA and GTC muscles. Utrophin and associated proteins are present in many cell clusters with continuous membrane labelling in MAS muscle. Respective proportions of myosin heavy chain isoforms, measured by electrophoresis/densitometry, showed only slight change in GTC muscle, significant evolution in DIA muscle but drastic isoform conversions in MAS muscle. These results highlighted the difference in deterioration susceptibility of various muscles to muscular dystrophy. The reason why this occurs in MAS muscles is still obscure and discussed in terms of the comparative developmental origins of these muscles.

Limb myosin heavy chain isoproteins and muscle fiber types in the adult goat (Capra hircus)

The primary focus of this study was the accurate classification of limb skeletal muscle fiber types in adult goats (Capra hircus) according to the myosin heavy chain (MHC) isoform they express. Combined methodologies of gel electrophoresis, immunoblotting, immunohistochemistry, myofibrillar ATPase (mATPase), and quantitative metabolic enzyme histochemistry of M. semitendinosus samples were developed. Three MHCs were identified and tentatively designated as types I, IIA, and IIX. Five fiber types were defined immunohistochemically according to their MHC content: I, I+IIA, IIA, IIAX, and IIX. The hybrid fast-twitch fibers (IIAX) totaled 21% of the fiber population analyzed. The three major pure fibers (I, IIA, and IIX) could be objectively separated upon the basis of their mATPase activities after acid and alkaline preincubations. The prominent number of hybrid fibers, however, could not be delineated with these mATPase methods. Metabolic and size properties of muscle fibers varied according to their MHC content, but overlapped the full range of muscle fiber phenotypes. These integrated data demonstrate that type II skeletal muscle fibers of small ruminants have been misclassified in previous studies. The immunohistochemical approach developed in the present study offers new prospects for muscle fiber typing in caprine experimental studies and meat production technologies.

[Sensitivity to atracurium in the lateral abdominal muscles]

OBJECTIVE

To study the effect of atracurium on the electromyographic activity of the lateral abdominal muscles and adductor pollicis in anaesthetized subjects.

STUDY DESIGN

Prospective, comparative, open study.

PATIENTS AND METHODS

Sixteen patients, ASA physical status 1 or 2, undergoing elective orthopaedic surgery under general anaesthesia were studied. Anaesthesia was induced with propofol/fentanyl and orotracheal intubation performed after glottic local anaesthesia without using muscle relaxant. Anaesthesia was maintained with isoflurane/nitrous oxide/oxygen and fentanyl reinjections. Supramaximal percutaneous stimulations in a simple twitch mode (0.1 Hz) were applied at the 9th-10th intercostal nerve on the posterior axillary line and at the ulnar nerve at the wrist. The electromyographic responses were registered using skin surface electrodes, placed on the D9-D10 dermatome in regard of the lateral abdominal muscles and of the thenar muscles. After a single bolus dose of atracurium 0.5 mg.kg-1, the following parameters were studied: the maximum effect (Emax), the time for obtaining Emax (Delay) and the recovery time of 5, 10, 25, 50, 75 and 100% of the control neuromuscular response (T5, T10, T25, T50, T75, T100).

RESULTS

The dose of 0.5 mg.kg-1 of atracurium induced 100% block in both lateral abdominal muscles and adductor pollicis. Lateral abdominal muscles blockade had faster onset (136 +/- 4 s versus 205 +/- 29 s) and shorter recovery, T5, T10, T25, T50, T75 and T100 were significantly (p < 0.05) shorter than at the adductor pollicis.

CONCLUSION

Lateral abdominal muscles blockade have faster onset and recovery than adductor pollicis.

Common peroneal nerve stimulation for neuromuscular monitoring: evaluation in awake volunteers and anesthetized patients

The study was conducted in two parts. First, evoked responses to common peroneal nerve stimulation at four electrode positions were tested in 25 awake volunteers. The initial threshold stimulus current (ITS) (minimal current producing dorsiflexion or eversion of the ankle joint and great toe) and the supramaximal stimulus current (SMS) (the point at which further increases in current did not produce increases in twitch tension) were defined. SMS was not reliably achieved using electrodes at each side of the fibular head. However, an exploratory electrode accurately located the nerve and enabled SMS in all volunteers (SMS/ITS = 3.4). Second, 16 anesthetized, paralyzed patients were studied. The common peroneal and ulnar nerves were stimulated simultaneously. Evoked tension was recorded at the adductor pollicis using a force transducer and at the great toe by a blinded observer. Reversal was given when the train-of-four count at the great toe reached four. Onset times were longer, and median posttetanic counts were greater, at the great toe compared with the adductor pollicis. Time from reversal to train-of-four ratio = 0.7 at the adductor pollicis was 207+/-160 s. We conclude that neuromuscular monitoring at the common peroneal nerve was not equivalent to monitoring at the ulnar nerve.

IMPLICATIONS

Accurate neuromuscular monitoring is important for patient safety. We studied the accuracy of monitoring at the common peroneal nerve in volunteers and patients. An exploratory electrode accurately located the common peroneal nerve. Monitoring at the common peroneal nerve was not equivalent to monitoring at the ulnar nerve in patients.

Duration of succinylcholine and vecuronium blockade but not potency correlates with the ratio of endplate size to fibre size in seven muscles in the goat

PURPOSE

Muscles differ in their response to neuromuscular relaxants. This study investigated whether (1) the relative responses of muscles is inverted between succinylcholine (SUX) and vecuronium (VEC), and (2) differences in dose-response or duration of action are related to the morphology of fibres, endplates and acetylcholine receptors (AChR) in muscles.

METHODS

In goats during thiopentone anaesthesia, the evoked EMG response to indirect train-of-four stimulation was monitored and the cumulative dose-response curves and duration of action of SUX and VEC in the diaphragm, cricoary-tenoideus dorsalis, thyroarytenoideus, transversus abdominis, rectus abdominis, soleus and gastrocnemius muscles were determined and related to their fibre composition, fibre size, endplate size, endplate to fibre size ratio, AChR number or AChR density by regression analysis.

RESULTS

There were no differences in the ED50S of SUX [range, 119 +/- 11 (SE) to 159 +/- 20 micrograms.kg-1] or VEC [range, 2.8 +/- 0.2 to 3.7 +/- 0.8 microgram.kg-1] among muscles. With either drug, duration to 25% or 50% T1 recovery was shortest at the laryngedl muscles and longest at abdominal muscles (P = 0.0001), and correlated directly with fibre size (r > or = 0.40; P < 0.004) and inversely with the endplate to fibre size ratio (r > or = 0.40; P < 0.008).

CONCLUSION

The results show that (1) the relative responses of muscles do not differ between depolarizing and non-depolarizing relaxants; (2) the duration of blockade is shorter in muscles composed of small fibres with large endplates relative to fibre size; and (3) there is no relation between fibre type composition and sensitivity to muscle relaxants.