Potentiation of Mivacurium Blockade by Low Dose of Pancuronium: A Pharmacokinetic Study

Background: Mivacurium is potentiated by pancuronium to a much greater extent than other relaxants. In a previous investigation we suggested that this potentiation could be due to the ability of pancuronium to inhibit plasma cholinesterase activity, but we did not measure plasma concentrations of mivacurium. In the current study we performed a pharmacokinetic analysis by measuring the plasma concentration of mivacurium when preceded by administration of a low dose of pancuronium.

Methods: After induction of general anesthesia with propofol and fentanyl and orotracheal intubation, 10 patients (pancuronium-mivacurium group) received 15 [mu]g/kg pancuronium followed 3 min later by 0.1 mg/kg mivacurium, whereas 10 other patients (mivacurium group) received saline followed by 0.13 mg/kg mivacurium 3 min later. Plasma cholinesterase activity was measured before and 3 and 30 min after pancuronium dosing in the pancuronium-mivacurium group and was measured before and after administration of saline in the mivacurium group. Arterial plasma concentrations of mivacurium and its metabolites were measured at 0.5, 1, 1.5, 2, 4, 10, 20, and 30 min after injection. Neuromuscular blockade was assessed by mechanomyography.

Results: Plasma cholinesterase activity decreased by 26% in the pancuronium-mivacurium group 3 min after injection of pancuronium (P < 0.01) and returned to baseline values 30 min later; however, no significant variation was observed in the mivacurium group. The clearances of the two most active isomers (Cis-Trans and Trans-Trans) were lower in the pancuronium-mivacurium group (17.6 +/- 5.1, 14.7 +/- 5.3 ml [middle dot] min-1[middle dot] kg-1, respectively) than in the mivacurium group (32.4 +/- 20.2, 24.8 +/- 13.5 ml [middle dot] min-1[middle dot] kg-1;P < 0.05).     

Overestimation of Bispectral Index in Sedated Intensive Care Unit Patients Revealed by Administration of Muscle Relaxant

Background: Electromyographic activity has previously been reported to elevate the Bispectral Index (BIS) in patients not receiving neuromuscular blockade while under sedation in the intensive care unit. This study aimed to investigate the magnitude of the decrease of BIS following administration of muscle relaxant in sedated intensive care unit patients.

Methods: The authors prospectively investigated 45 patients who were continuously sedated with midazolam and sufentanil to achieve a Sedation-Agitation Scale value equal to 1 and who required administration of muscle relaxant. BIS (BIS(R) version 2.10), electromyography, and acceleromyography at the adductor pollicis muscle were recorded simultaneously before and after neuromuscular blockade. Sixteen of these 45 patients were also studied simultaneously with the new BIS(R) XP.

Results: After administration of a muscle relaxant, BIS (67 +/- 19 vs. 43 +/- 10, P < 0.001) and electromyographic activity (37 +/- 9 vs. 27 +/- 3 dB, P < 0.001) significantly decreased. Multiple regression analysis showed that the decrease of BIS following administration of myorelaxant was significantly correlated to BIS and electromyographic baseline values. Using standard BIS range guidelines, the number of patients under light or deep sedation versus general anesthesia or deep hypnotic state was markedly overestimated before administration of myorelaxant (53 vs. 2%, P < 0.001).     

The Problem of the Aging Surgeon: When Surgeon Age Becomes a Surgical Risk Factor

The question of when a surgeon should retire has been the subject of debate for decades. Both anecdotal evidence and objective testing of surgeons suggest age causes deterioration in physical and cognitive performance. Medical education, residency and fellowship training, and technology evolve at a rapid pace, and the older a surgeon is, the more likely it is he or she is remote from his or her initial education in his or her specialty. Research also shows surgeons are reluctant to plan for retirement. Although there is no federally mandated retirement age for surgeons in the United States, surgeons must realize their skills will decline, a properly planned retirement can be satisfying, and the retired surgeon has much to offer the medical and teaching community. The author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.     

Residual Paralysis in the PACU after a Single Intubating Dose of Nondepolarizing Muscle Relaxant with an Intermediate Duration of Action

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 ED95 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).     

Enhancement of Renal Function by a Long-acting Somatostatin Analogue in Patients with Decompensated Cirrhosis

The effect of the long-acting somatostatin analogue SMS 201–995on renal function was investigated in nine cirrhotic patientswith ascites, low urine output, low serum sodium, and normalserum creatinine. SMS 201–995, infused at 40 µg/hfor 2 h, produced a significant increase in urine volume, asignificant decrease in urine osmolality, and a significantincrease in creatinine clearance. These changes, although lesspronounced, persisted 24 h after the infusion of the analogue.No significant changes in free water clearance, urinary sodiumexcretion or serum sodium were noted. The effects of SMS 201–995might be attributed to an improvement of renal haemodynamicsthrough inhibition of vasoconstrictor systems acting in cirrhosis.It is concluded that SMS 201–995 may have a role in thetreatment of the renal abnormalities complicating liver disease.     

Response to Mivacurium in a Patient Compound Heterozygous for a Novel and a Known Silent Mutation in the Butyrylcholinesterase Gene: Genotyping by Sequencing

Background: Patients who are homozygous for the atypical mutation, compound heterozygous for atypical and silent mutations, or homozygous for silent mutations (SS) respond to mivacurium with extensively prolonged neuromuscular block. Although important, exact phenotyping of these patients is difficult. This article presents the pharmacodynamics and pharmacokinetics of a normal dose of mivacurium in a patient with phenotype SS, including a pedigree analysis and delineation of the molecular genetic method used to identify the genotype.

Methods: The neuromuscular block following administration of mivacurium, at a dose of 0.14 mg/kg, was monitored in a 30-yr-old healthy man with use of a mechanosensor and mechanomyography, and times to different levels of recovery were measured. Venous samples for determination of the mivacurium isomers were collected during the interval 134-494 min after administration of mivacurium, and the terminal half-lives were calculated. Butyrylcholinesterase activity, phenotype, and genotype were determined for both the patient and the family. Complete nucleotide sequencing was used to identify the genotype.

Results: A train-of-four ratio of 0.75 was reached 469 min after the injection of mivacurium. The terminal elimination half-lives of the mivacurium isomers, cis-trans and trans-trans, were 90 min. Complete nucleotide sequencing revealed two point mutations, the known silent variant S7 and a previously undescribed mutation of amino acid residue 170 introducing a stop codon.     

Muscle activity during a dash shown by 18F-fluorodeoxyglucose positron emission tomography

Background ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been used to examine muscle activity during running. The dash is a basic activity in various kinds of sports but differs from running in terms of intensity and severity. The purpose of this study was to evaluate muscle activity during running at full speed using FDG PET. Methods Six healthy men were investigated during a dash for 10 min after intravenous injection of FDG (37 MBq). Another six healthy men were studied as controls. PET images were obtained 45 min after the FDG injection. Regions of interest were drawn on the anterior and posterior thighs and the anterior and posterior legs. The standardized uptake value (SUV) was calculated to examine the FDG uptake of muscle tissue per unit volume according to an equation. Results In the control group, the mean SUVs of the anterior thigh, posterior thigh, anterior leg, and posterior leg were 0.49 ± 0.04, 0.44 ± 0.02, 0.46 ± 0.05, and 0.44 ± 0.07, respectively. In the dash group, the mean SUVs of the anterior thigh, posterior thigh, anterior leg, and posterior leg were 0.74 ± 0.20, 0.79 ± 0.08, 0.61 ± 0.07, and 0.60 ± 0.08, respectively. FDG accumulation of every one of the four compartments in the dash group was significantly higher than that in the control. FDG accumulation of the posterior thigh was significantly higher than that of the anterior and the posterior leg in the dash group (P < 0.02). Conclusion Based on the results of our investigation, posterior thigh muscles were especially active during a dash.     

Evidence of Reduced Muscle Trauma Through a Minimally Invasive Anterolateral Approach by Means of MRI

Background  

Minimally invasive techniques in THA are intended to minimize periarticular muscle trauma. The lateral approach has a risk of partial gluteal insufficiency, while the anterolateral approach carries the risk of damaging the tensor fasciae latae through intermuscular nerve and compression injury.     

靶肌肉注射睫状神经营养因子促周围神经再生的功能评价

目的 评价靶肌肉注射睫状神经营养因子(Ciliary Neumtrophic Factor，CNTE)对受损周围神经功能恢复的影响。方法 用硅胶管桥接80支大鼠左侧6mm长坐骨神经缺损，随机分为2组。分别行CNTF、生理盐水(NS)靶肌肉注射。术后行坐骨神经功能指数(SFI)测定、电生理检测、轴突图像分析及霍乱毒素-辣根过氧化物酶(CB-HRP)逆行追踪。结果 CNTE组SFI恢复率、各项电生理及轴突图像分析指标、CB-HRP标记的脊髓前角运动细胞数明显优于NS组。结论 靶肌肉注射CNTF可明显促进周围神经再生，提高神经功能恢复。     

Cross-Facial Nerve Graft: A Report of Chronically Paralyzed Facial Muscle Neurotization by a Nerve Graft

A 21-year-old housewife with long-standing hemifacial paralysis on the left side decided to undergo the classic two-stage cross-facial nerve graft with muscle transfer. The first stage of the operation was performed successfully with the use of a sural nerve graft. After the appearance of Tinel’s sign 8 months later, gain of function in the muscles of the paralyzed side was observed and negated the need for the second-stage muscle transfer.     

Biceps Femoris Muscle is Activated by Performing Nordic Hamstring Exercise at a Shallow Knee Flexion Angle

The semitendinosus (ST) muscle is primarily used during Nordic hamstring exercise (NHE), which is often prescribed for preventing hamstring injury, though the biceps femoris long head (BFlh) muscle that is more susceptible to injuries. Thus, this study aimed to identify the modulation of BFlh muscle activity with different knee flexion angles during NHE using an inclined platform. Fourteen male athletes performed NHE and maintained their position at maximum inclination (NH). Subjects also performed isometric NHE using a platform inclined to 50° (ICL) and 40° (ICH), and the knee flexion angle was controlled to 50° and 30°. The electromyography (EMG) activity of the BFlh, ST, semimembranosus, gluteus maximus, elector spinae, and rectus abdominus muscles was determined during each exercise. The EMG of the ST was higher than that of the BFlh during NHE and the highest of all muscles in all exercises (p < 0.05). Moreover, the activity of the BFlh tended to be higher than that of the ST for ICH than for ICL, regardless of the knee joint angle. The activity of the BFlh becomes equivalent to that of the ST during NHE at a knee flexion angle of less than 50°. These results indicate that performing NHE at a shallow knee flexion angle will enhance the activity of the BFlh muscle.Key points

• Performing Nordic Hamstring exercise at a shallow knee flexion angle will enhance the biceps femoris muscle rather than the semitendinosus muscle
• There is no significant inter-load difference in the EMG activity of hamstring muscles across different inclination platform angles when the knee joint angle is the same
• Using an incline platform enables athletes with an insufficient strength of hamstring muscles to perform Nordic Hamstring exercises at a shallow knee angle.

Key words: Electromyography, physical conditioning, preventive medicine, muscle strain injury     

Muscle mass index in haemodialysis patients: a comparison of indices obtained by routine clinical examinations.

BACKGROUND: Measurement of muscle mass is useful for evaluating protein nutritional status. Various methods for estimating muscle mass in haemodialysis patients have recently been developed. METHODS: The validity of the estimate of creatinine production calculated with the creatinine kinetic model (CKM) was examined in 46 haemodialysis patients by comparing it with the actual creatinine production, this being determined from the sum of creatinine appearing in the dialysate and the estimated metabolic degradation. The correlation of various other muscle mass indices with creatinine production was also investigated in these patients. RESULTS: The estimate of creatinine production using CKM was significantly correlated with creatinine production calculated from the spent dialysate plus an estimate for the extra-renal creatinine degradation (r=0.90, P<0.001). A Bland-Altman analysis revealed that the mean prediction error for the estimate of creatinine production by CKM was +0.10 g/day and the limits of agreement were +0.34 to -0.14 g/day. The cross-sectional area of the thigh muscle measured by computed tomography (CT) was also significantly correlated with creatinine production (r=-0.86, P<0.01). In contrast, the correlations of 3-methylhistidine production measured in the spent dialysate, the mid-upper arm muscle circumference and the skeletal muscle mass estimated by an anthropometric prediction model with creatinine production were lower (r<0.82). CONCLUSION: Creatinine production calculated using CKM and CT measurement of thigh muscle area are valid methods for estimating muscle mass during routine clinical examinations of haemodialysis patients.