Up-and-down regulation of skeletal muscle acetylcholine receptors. Effects on neuromuscular blockers

Effect of sugammadex on postoperative complications in patients with severe burn who underwent surgery: a retrospective study

This retrospective study investigated the association of sugammadex with postoperative pulmonary complication risk between 2013 and 2021 in patients with severe burn of five hospitals. Postoperative pulmonary complications included atelectasis, pulmonary edema, pulmonary effusion, pneumothorax, pneumonia, pulmonary thromboembolism, respiratory failure and acute respiratory distress. To identify whether sugammadex reduced the risk of postoperative pulmonary complication in patients with severe burn who underwent surgery, Kaplan-Meier curve were used to check the difference of incidence according to surgical cases and time-varying Cox hazard regression were used to calculate the hazard ratio. The study included 1213 patients with severe burn who underwent 2259 surgeries. Postoperative pulmonary complications were occurred in 313 (25.8%) patients. Among 2259 surgeries, sugammadex was used in 649 (28.7%) surgeries. Cumulative postoperative pulmonary complication were 268 (16.6%) cases in surgeries without sugammadex, and 45 (6.9%) cases in surgeries with sugammadex, respectively (P < 0.005). The postoperative pulmonary complications risk was reduced significantly in patients who use sugammadex than those who did not use sugammadex. (Adjusted hazard ratio, 0.61; 95% confidence interval, 0.42-0.89; P = 0.011). In conclusion, sugammadex reduced risk of postoperative pulmonary complications compared with nonuse of sugammadex in patients with severe burn who underwent surgery.

Anaesthetic management of people with multiple sclerosis

There is a lack of published guidelines on the management of patients with multiple sclerosis (MS) undergoing procedures that require anaesthesia and respective advice is largely based on retrospective studies or case reports. The aim of this paper is to provide recommendations for anaesthetists and neurologists for the management of patients with MS requiring anaesthesia. This review covers issues related to the anaesthetic management of patients with MS, with a focus on preoperative assessment, choice of anaesthetic techniques and agents, side-effects of drugs used during anaesthesia and their potential impact on the disease evolution, drug interactions that may occur, and the need to use monitoring devices. A systematic PubMed research was performed to retrieve relevant articles.

Calcineurin-Dependent Homeostatic Response of C. elegans Muscle Cells upon Prolonged Activation of Acetylcholine Receptors

Pharmacological adaptation is a common phenomenon observed during prolonged drug exposure and often leads to drug resistance. Understanding the cellular events involved in adaptation could provide new strategies to circumvent this resistance issue. We used the nematode Caenorhabditis elegans to analyze the adaptation to levamisole, an ionotropic acetylcholine receptor agonist, used for decades to treat nematode parasitic infections. Genetic screens in C. elegans identified "adapting mutants" that initially paralyze upon exposure to levamisole as the wild type (WT), but recover locomotion after a few hours whereas WT remain paralyzed. Here, we show that levamisole induces a sustained increase in cytosolic calcium concentration in the muscle cells of adapting mutants, lasting several hours and preceding a decrease in levamisole-sensitive acetylcholine receptors (L-AChR) at the muscle plasma membrane. This decrease correlated with a drop in calcium concentration, a relaxation of the animal's body and a resumption of locomotion. The decrease in calcium and L-AChR content depends on calcineurin activation in muscle cells. We also showed that levamisole adaptation triggers homeostatic mechanisms in muscle cells including mitochondria remodeling, lysosomal tubulation and an increase in autophagic activity. Levamisole adaptation thus provides a new experimental paradigm for studying how cells cope with calcium stress.

Perioperative Management of Lewis-Sumner Syndrome

Lewis-Sumner syndrome (LSS) is a rare immune-mediated neuromuscular disorder. It shares some clinical and pathological features with chronic inflammatory demyelinating polyneuropathy (CIDP). We report on the anaesthetic management of a patient with LSS. There are several concerns when anaesthetizing patients with demyelinating neuropathies, the main ones being the post-operative worsening of symptoms and respiratory depression related to muscle relaxants. In our experience, the rocuronium effect was prolonged and an even lower dosage (0.4 mg/kg) was sufficient for intubation and maintenance. Sugammadex allowed total reversion of neuromuscular block and no respiratory complications occurred. In conclusion, the combination of lower dose rocuronium and sugammadex was safely used in a patient with LSS.

Molecular mechanisms of muscular and non-muscular actions of neuromuscular blocking agents in critical illness: a narrative review

Despite frequent use of neuromuscular blocking agents in critical illness, changes in neuromuscular transmission with critical illness are not well appreciated. Recent studies have provided greater insights into the molecular mechanisms for beneficial muscular effects and non-muscular anti-inflammatory properties of neuromuscular blocking agents. This narrative review summarises the normal structure and function of the neuromuscular junction and its transformation to a 'denervation-like' state in critical illness, the underlying cause of aberrant neuromuscular blocking agent pharmacology. We also address the important favourable and adverse consequences and molecular bases for these consequences during neuromuscular blocking agent use in critical illness. This review, therefore, provides an enhanced understanding of clinical therapeutic effects and novel pathways for the salutary and aberrant effects of neuromuscular blocking agents when used during acquired pathologic states of critical illness.

Morphological and biochemical changes of lymphatic vessels in the soleus muscle of mice after hindlimb unloading

INTRODUCTION/AIMS

Lymphatic vessels are responsible for the removal of metabolic waste from body tissues. They also play a crucial role in skeletal muscle functioning thorough their high-energy metabolism. In this study we investigated whether disuse muscle atrophy induced by hindlimb unloading is associated with an alteration in the number of lymphatic vessels and differential expression of lymphangiogenic factors in the soleus muscle.

METHODS

Male C57BL/6 mice were subjected to tail suspension (TS) for 2 or 4 weeks to induce soleus muscle atrophy. After TS, lymphatic and blood capillaries in the soleus muscle were visualized and counted by double staining with LYVE-1 and CD31. The protein and mRNA levels of vascular endothelial growth factor (VEGF)-C, VEGF-D, and vascular endothelial growth factor receptor-3 were measured by Western blotting and real-time reverse transcript polymerase chain reaction, respectively.

RESULTS

TS for 2 weeks resulted in a significant decrease in the number of blood capillaries compared with controls. However, there was no significant change in the number of lymphatic capillaries. By contrast, TS for 4 weeks resulted in a significant decrease in the number of lymphatic and blood capillaries. We observed a significant decrease in the mRNA levels of VEGF-C and VEGF-D in mice subjected to TS for 4 weeks.

DISCUSSION

The decrease of intramuscular lymphatic vessels may a crucial role in the process of muscle atrophy.

First genome-wide association study on rocuronium dose requirements shows association with SLCO1A2

Background

Rocuronium, a common neuromuscular blocking agent, is mainly excreted unchanged in urine (10–25%) and bile (>70%). Age, sex, liver blood flow, smoking, medical conditions, and ethnic background can affect its pharmacological actions. However, reasons for the wide variation in rocuronium requirements are mostly unknown. We hypothesised that pharmacogenetic factors might explain part of the variation.

Methods

One thousand women undergoing surgery for breast cancer were studied. Anaesthesia was maintained with propofol (50–100 μg kg⁻¹ min⁻¹) and remifentanil (0.05–0.25 μg kg⁻¹ min⁻¹). Neuromuscular block was maintained with rocuronium to keep the train-of-four ratio at 0–10%. DNA was extracted from peripheral blood and genotyped with a next-generation genotyping array. The genome-wide association study (GWAS) was conducted using an additive linear regression model with PLINK software. The FINEMAP tool and data from the Genotype-Tissue Expression project v8 were utilised to study the locus further.

Results

The final patient population comprised 918 individuals. Of the clinical variables tested, age, BMI, ASA physical status, and total dose of propofol correlated significantly (all P<0.001) with the rocuronium dose in a linear regression model. The GWAS highlighted one genome-wide significant locus in chromosome 12. The single-nucleotide polymorphisms (SNPs) with the most significant evidence of association were located in or near SLCO1A2. The two top SNPs, rs7967354 (P=5.3e⁻¹¹) and rs11045995 (P=1.4e⁻¹⁰), and the clinical variables accounted for 41% of the variability in rocuronium dosage.

Conclusions

Genetic variation in the gene SLCO1A2, encoding OATP1A2, an uptake transporter, accounted for 4% of the variability in rocuronium consumption. The underlying mechanism remains unknown.

Suxamethonium-Induced Hyperkalemia: A Short Review of Causes and Recommendations for Clinical Applications

After the introduction of suxamethonium in 1953, cases of cardiac arrest during induction of anesthesia were recorded. In the following years, hyperkalemia was identified as the cause, and the connection to acetylcholine receptor modulation as the underlying molecular mechanism was made. Activation of the acetylcholine receptor with suxamethonium, acetylcholine, or choline causes an efflux of potassium to the extracellular space. However, certain pathological conditions cause acetylcholine receptor proliferation and the emergence of immature receptors capable of a larger potassium efflux to the bloodstream. These pathologic conditions include upper and lower neuron injuries, major burns, trauma, immobility, muscle tumors, muscular dystrophy, and prolonged critical illness. The latter is more important and relevant than ever due to the increasing number of COVID-19 patients requiring prolonged respiratory support and consequent immobilization. Suxamethonium can be used safely in the vast majority of patients. Still, reports of lethal hyperkalemic responses to suxamethonium continue to emerge. This review serves as a reminder of the pathophysiology behind extensive potassium release. Proficiency in the use of suxamethonium includes identification of patients at risk, and selection of an alternative neuromuscular blocking agent is imperative.

The Pediatric Burn: Current Trends and Future Directions

Management of the pediatric burn patient presents a variety of clinical challenges for the pediatric anesthesiologist. Despite the high incidence of burn injuries, standard management strategies are far from universal. The complex physiologic changes presented by burn injuries present airway management and resuscitation challenges and mandate careful consideration of adequate nutritional support. Long hospital stays with frequent operations and dressing changes necessitate creative approaches to anxiolysis and pain control. Underutilized modalities warranting further research include regional anesthesia and nonpharmacologic approaches, such as virtual reality. Further research and collaboration between burn centers are needed to standardize care for this population.

Effects of neuromuscular presynaptic muscarinic M1 receptor blockade on rocuronium-induced neuromuscular blockade in immobilized tibialis anterior muscles

This in vivo study tested the hypothesis that the modulation of acetylcholine (ACh) release by the M₁ muscarinic receptor (mAChR) in the neuromuscular junction of disused muscles may affect the tensions of the muscles during the neuromuscular monitoring of a rocuronium‐induced neuromuscular block and compared the results with those obtained from normal muscles. A total of 20 C57BL/6 (wild‐type) and 10 α7 knock out (α7KO) mice were used in this experiment. As a pre‐experimental procedure, knee and ankle joints of right hind limbs were fixed by needle pinning at the 90° flexed position. After 2 weeks, the main experiment was performed. Both tendons of the tibialis anterior (TA) muscles were obtained, and the muscle tensions were recorded while the dose‐responses of rocuronium were measured three times in the same mouse by the serial administration of pirenzepine (0, 0.001 and 0.01 μg/g). Weight losses were observed after 2 weeks of immobilization in both groups, and a decrease in the mass of TA muscles at the immobilized side was observed compared to those of the contralateral nonimmobilized side. Tension depression of the TA muscles at immobilized side of the α7KO group was faster than those of the wild‐type group, but these differences decreased after the administration of pirenzepine. The tension depressions were similar regardless of the pirenzepine doses at the same side in the group. Tension depression may become more rapid in the α7 AChR‐expressed disused muscles by the decreased release of ACh release upon neuronal firing by the blockade of facilitatory M₁mAChR

Infusion dose requirement of rocuronium in patients on phenytoin therapy - A prospective comparative study

Background and Aims:

Patients with intracranial tumour are usually on anticonvulsants. Patients on phenytoin therapy demonstrate rapid metabolism of nondepolarising muscle relaxants secondary to enzyme induction. Infusion dose requirement of rocuronium in such patients has been sparingly studied. We studied the continuous infusion dose requirement of rocuronium bromide in patients on phenytoin therapy and its correlation with serum levels of phenytoin.

Methods:

Seventy-five patients scheduled for supratentorial tumour surgery were included in the study. Patients not on phenytoin were taken as control. The primary outcome variable studied was the infusion dose requirement of rocuronium in patients on phenytoin. Based on pre-operative serum phenytoin levels, study group patients were divided into two groups: sub-therapeutic level group (phenytoin level <10 μg/mL) and therapeutic level group (phenytoin level >10 μg/mL). Following anaesthesia induction, rocuronium bromide 0.6 mg/kg was administered to achieve tracheal intubation. Rocuronium infusion was titrated to maintain zero response on the train-of-four response.

Results:

Demographic data were comparable. Patients receiving phenytoin required higher infusion dose compared to the control group (0.429 ± 0.2 mg/kg/h vs. 0.265 ± 0.15 mg/kg/h, P < 0.001). The serum phenytoin level had no correlation to infusion dose requirement of rocuronium (0.429 ± 0.205 mg/kg/h vs. 0.429 ± 0.265 mg/kg/h (P = 0.815). The recovery was faster in the phenytoin group compared to the control group. Haowever, it was not clinically significant.

Conclusion:

The infusion dose requirement of rocuronium bromide in patients on phenytoin is higher and the serum levels of phenytoin does not influence the dose required.

Factors that affect the onset of action of non-depolarizing neuromuscular blocking agents

Neuromuscular blockade plays an important role in the safe management of patient airways, surgical field improvement, and respiratory care. Rapid-sequence induction of anesthesia is indispensable to emergency surgery and obstetric anesthesia, and its purpose is to obtain a stable airway, adequate depth of anesthesia, and appropriate respiration within a short period of time without causing irritation or damage to the patient. There has been a continued search for new neuromuscular blocking drugs (NMBDs) with a rapid onset of action. Factors that affect the onset time include the potency of the NMBDs, the rate of NMBDs reaching the effect site, the onset time by dose control, metabolism and elimination of NMBDs, buffered diffusion to the effect site, nicotinic acetylcholine receptor subunit affinity, drugs that affect acetylcholine (ACh) production and release at the neuromuscular junction, drugs that inhibit plasma cholinesterase, presynaptic receptors responsible for ACh release at the neuromuscular junction, anesthetics or drugs that affect muscle contractility, site and methods for monitoring neuromuscular function, individual variability, and coexisting disease. NMBDs with rapid onset without major adverse events are expected in the next few years, and the development of lower potency NMBDs will continue. Anesthesiologists should be aware of the use of NMBDs in the management of anesthesia. The choice of NMBD and determination of the appropriate dosage to modulate neuromuscular blockade characteristics such as onset time and duration of neuromuscular blockade should be considered along with factors that affect the effects of the NMBDs. In this review, we discuss the factors that affect the onset time of NMBDs.

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.

Neuromuscular Recovery Is Prolonged After Immobilization or Superimposition of Inflammation With Immobilization Compared to Inflammation Alone: Data From a Preclinical Model

OBJECTIVES

Recovery from ICU-acquired muscle weakness extends beyond hospital stay. We hypothesized that immobilization, more than inflammation, plays a prominent role in the delayed recovery from critical illness.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Animal laboratory, university hospital.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Animals were divided to have one hind limb immobilized (n = 129) or sham-immobilized (n = 129) on day -12. After surgery, rats were further assigned to two subgroups. To induce inflammation, rats received three IV injections of Corynebacterium parvum on days -12, -8, and -4. Controls received saline at the respective time-points. At day 0, the limbs were remobilized and recovery from inflammation and/or immobilization was followed for 36 days.

MEASUREMENTS AND MAIN RESULTS

At day 0 and after 4, 12, or 36 days of recovery, maximum tetanic tension and tetanic fade (functional parameters = primary outcome variables) as well as nicotinic acetylcholine receptor expression, muscle mass, and histologic changes (structural parameters = secondary outcome variables) were measured. Impaired maximum tetanic tension, decreased tibialis muscle mass, and fiber diameter due to inflammation alone recovered by day 4. Tetanic fade was not affected by inflammation. Immobilization-induced loss of tibialis muscle mass, decreased fiber diameter, and tetanic fade did not return to normal until day 36, while maximum tetanic tension had recovered at that time. In the presence of inflammation and immobilization, the decrease in tibialis muscle mass, fiber diameter, and maximum tetanic tension, as well as decreased tetanic fade persisted until day 36. Up-regulation of nicotinic acetylcholine receptors normalized before day 4 following inflammation, but persisted until day 4 following immobilization.

CONCLUSIONS

In our model, muscle function and structure recovered from inflammation within 4-12 days. Immobilization-induced neuromuscular changes, however, persisted even at day 36, especially if inflammation was concomitant.

Decreased Spontaneous Electrical Activity and Acetylcholine at Myofascial Trigger Spots after Dry Needling Treatment: A Pilot Study

OBJECTIVE

The aims of this study are to investigate the changes in spontaneous electrical activities (SEAs) and in acetylcholine (ACh), acetylcholine receptor (AChR), and acetylcholine esterase (AChE) levels after dry needling at myofascial trigger spots in model rats.

MATERIALS AND METHODS

Forty-eight male Sprague-Dawley rats were divided into four groups. Thirty-six rats were assigned to three model groups, which underwent MTrSs modeling intervention. Twelve rats were assigned to the blank control (BC) group. After model construction, the 36 model rats were randomly subdivided into three groups according to treatment: MTrSs model control (MC) and two dry needling groups. One dry needling group received puncturing at MTrSs (DN-M), whereas the other underwent puncturing at non-MTrSs (DN-nM). Dry needling treatment will last for two weeks, once a week. SEAs and ACh, AChR, and AChE levels were measured after one-week rest of dry needling treatment.

RESULTS

The amplitudes and frequencies of endplate noise (EPN) and endplate spike (EPS) significantly decreased after dry needling treatment in the DN-M group. Moreover, ACh and AChR levels significantly decreased, whereas AChE significantly increased after dry needling treatment in the DN-M group.

CONCLUSION

Dry needling at the exact MTrSs is more effective than dry needling at non-MTrSs.

Role of Anesthesiologist in the Management of a Child with Cerebral Palsy

Cerebral palsy (CP) refers to a spectrum of nonprogressive neurological disorders with disturbances in posture and movement, resulting from perinatal intrauterine insult to developing infant brain. Many conditions associated with CP require surgery. Such cases pose important gastrointestinal, respiratory, and other perioperative considerations. Anesthetic management in these cases is delicate. Intraoperative complications including hypovolemia, hypothermia, muscle spasms, seizures, and delayed recovery might complicate the anesthetic management. A thorough preanesthetic evaluation allows for a better intra- and post-operative care. Postoperative analgesia is important, particularly in orthopedic surgeries one for pain relief. This review highlights the clinical manifestations in CP and anesthetic considerations in such child presenting for various surgeries.

Neuromuscular Blockade in the 21st Century Management of the Critically Ill Patient

Neuromuscular blockings agents (NMBAs) have a controversial role in the ventilatory and medical management of critical illness. The clinical concern surrounding NMBA-induced complications stems from evidence presented in the 2002 clinical practice guidelines, but new evidence from subsequent randomized trials and studies provides a more optimistic outlook about the application of NMBAs in the ICU. Furthermore, changes in the delivery of critical care, such as protocolized care pathways, minimizing or interrupting sedation, increased monitoring techniques, and overall improvements in reducing immobility, have created a modern, 21st century ICU environment whereby NMBAs may be administered safely. In this article we start with a review of the mechanism of action, side effects, and pharmacology of commonly used NMBAs. We then address the rationale for NMBA use for an expanding number of indications (endotracheal intubation, acute respiratory distress syndrome, status asthmaticus, increased intracranial and intra-abdominal pressure, and therapeutic hypothermia after cardiac arrest), with an emphasis on NMBA use in facilitating lung-protective ventilation for respiratory failure. We end with an appraisal over the importance of monitoring depth of paralysis and the concerns of complications, such as prolonged skeletal muscle weakness. In the context of adequate sedation and analgesia, monitored NMBA use (continuous or bolus administration) can be considered for the small number of clinical indications in critically ill patients for which evidence currently exists.

Effects of skeletal muscle denervation on the potency of succinylcholine

The aim of the present study was to investigate the time‑dependent effects of denervation on the sensitivity of skeletal muscles to the relaxant succinylcholine (SuCh) and to assess the possible association of the de novo expression of γ‑acetylcholine receptor (AChR). Innervated as well as denervated mouse muscle cells and human embryonic kidney (HEK293) cells expressing γ‑AChR and ε‑AChR were used in the present study. The effects of SuCh on the current of nicotinic (n)AChRs were examined using a whole‑cell patch clamp technique. Compared with innervated skeletal muscle cells, the SuCh concentration producing 50% of the maximal response (EC50) were decreased by 20, 56, 73, 66, 60 and 62% (P<0.05), and current responses induced by 30 µM SuCh were increased by 1.9‑, 4.6‑, 9.4‑, 7.1‑, 5.2‑ and 5.1‑fold (P<0.05) at days 1, 4, 7, 14, 21 and 28 after denervation, respectively. However, SuCh was equipotent regarding γ‑AChR and ε‑AChR (P>0.05). These results indicated that short‑term denervation led to a change in the sensitivity of muscle cells to SuCh, which, however, was unlikely to be associated with the de novo expression of γ‑AChR.

Complete resistance after maximal dose of rocuronium

Rocuronium is a non-depolarizing neuromuscular blocking agent (NDNMBA), employed in the clinic as an adjunct to general anesthesia to facilitate tracheal intubation rapid sequence, and to provide skeletal muscle relaxation during surgery. Many cases of resistance to neuromuscular blocking agents (NMBAs) have been anecdotally reported. There are specific pathologic states, such as upper motor neuron lesions, severe thermal injuries, liver disease, renal failure, disuse atrophy, all of which show an increased resistance to the effects of nondepolarizing muscle relaxants. Also concurrent drug therapy can alter the efficacy of NMBAs such as some classes of antibiotics, furosemide, β receptor agonists, phosphodiesterase inhibitors, calcium antagonists, respiratory stimulants but also ketamine, propofol and barbiturates at high concentrations. In this scenario we describe an unusual case of 20-years-old man who showed a complete resistance to rocuronium maybe due to a glucocorticoids concomitant therapy.

Effects of single-shot and steady-state propofol anaesthesia on rocuronium dose-response relationship: a randomised trial

BACKGROUND

Similar to volatile anaesthetics, propofol may influence neuromuscular transmission. We hypothesised that the administration of propofol influenced the potency of rocuronium depending on the duration of the administration.

METHODS

After consent, patients scheduled for elective surgery randomly received rocuronium either after induction of anaesthesia with propofol (2 min of propofol, n = 36) or after 30 min of propofol infusion (30 min of propofol, n = 36). Remifentanil was given in both groups. Neuromuscular monitoring was performed by calibrated electromyography. The dose-response relationship of rocuronium was determined with a single-bolus technique (0.07, 0.1, 0.15, 0.2, 0.3 and 0.45 mg/kg rocuronium). The primary endpoints were the ED50 and ED95 of rocuronium after 2 and 30 min propofol. Data are presented as means with (95% confidence interval). The trial is registered with the Eudra-CT: 2009-012815-16.

RESULTS

A total of 72 patients were included. Time to maximal neuromuscular blockade was significantly shorter in patients after 30 min of propofol [3.3 min (2.9-3.7)] compared with patients anaesthetised with 2 min of propofol [4.6 min (4.0-5.2)]. After 30 min of propofol, the slope of the dose-response curve was significantly steeper (30 min of propofol: 4.34 [3.62-5.05]; 2 min of propofol: [3.34 (2.72-3.96)], resulting in lower ED95 values of rocuronium (30 min of propofol: 0.287 mg/kg [0.221-0.368]; 2 min of propofol [0.391 mg/kg (0.296-0.520)]. The ED50 were not different between groups.

CONCLUSION

The potency of rocuronium was significantly enhanced after propofol infusion for 30 min. Estimates of potency those are usually determined during steady-state anaesthesia might underestimate rocuronium requirements for endotracheal intubation at the time of induction.

The Sick and the Weak: Neuropathies/Myopathies in the Critically Ill

Critical illness polyneuropathies (CIP) and myopathies (CIM) are common complications of critical illness. Several weakness syndromes are summarized under the term intensive care unit-acquired weakness (ICUAW). We propose a classification of different ICUAW forms (CIM, CIP, sepsis-induced, steroid-denervation myopathy) and pathophysiological mechanisms from clinical and animal model data. Triggers include sepsis, mechanical ventilation, muscle unloading, steroid treatment, or denervation. Some ICUAW forms require stringent diagnostic features; CIM is marked by membrane hypoexcitability, severe atrophy, preferential myosin loss, ultrastructural alterations, and inadequate autophagy activation while myopathies in pure sepsis do not reproduce marked myosin loss. Reduced membrane excitability results from depolarization and ion channel dysfunction. Mitochondrial dysfunction contributes to energy-dependent processes. Ubiquitin proteasome and calpain activation trigger muscle proteolysis and atrophy while protein synthesis is impaired. Myosin loss is more pronounced than actin loss in CIM. Protein quality control is altered by inadequate autophagy. Ca(2+) dysregulation is present through altered Ca(2+) homeostasis. We highlight clinical hallmarks, trigger factors, and potential mechanisms from human studies and animal models that allow separation of risk factors that may trigger distinct mechanisms contributing to weakness. During critical illness, altered inflammatory (cytokines) and metabolic pathways deteriorate muscle function. ICUAW prevention/treatment is limited, e.g., tight glycemic control, delaying nutrition, and early mobilization. Future challenges include identification of primary/secondary events during the time course of critical illness, the interplay between membrane excitability, bioenergetic failure and differential proteolysis, and finding new therapeutic targets by help of tailored animal models.

NRIP is a novel Z-disc protein to activate calmodulin signaling for skeletal muscle contraction and regeneration

Nuclear receptor interaction protein (NRIP, also known as DCAF6 and IQWD1) is a calcium-dependent calmodulin binding protein (Ca2+/CaM). In this study, we found that NRIP is a novel Z-disc protein in skeletal muscle. NRIP knockout mice (NRIP KO) were generated and found to have reduced muscle strength, susceptibility to fatigue and impaired adaptive exercise performance. The mechanisms of NRIP-regulated muscle contraction depend on NRIP being downstream of calcium signaling, where it stimulates phosphorylation of both calcineurin-nuclear factor of activated T-cells, cytoplasmic 1 (CaN-NFATc1) and calmodulin-dependent protein kinase II (CaMKII) through interaction with CaM, resulting in the induction of slow myosin gene expression and mitochondrial activity, and balancing of Ca2+ homeostasis of the internally stored Ca2+ of the sarcoplasmic reticulum. Moreover, NRIP KO mice have delayed regenerative capacity. The amount of NRIP can be enhanced after muscle injury and is responsible for muscle regeneration, coupled with the increased expression of myogenin, desmin and embryonic myosin heavy chain for myogenesis, as well as myotube formation. In conclusion, NRIP is a novel Z-disc protein important for skeletal muscle strength and regenerative capacity.

The use of sugammadex in a patient with Kennedy's disease under general anesthesia

Kennedy's disease (KD), also known as spinal and bulbar muscular atrophy, is a rare, X-linked recessive, neurodegenerative disorder of the lower motor neurons characterized by progressive bulbar and appendicle muscular atrophy. Here we report a case of a 62-year-old male patient with KD, weighing 70 kg and 173 cm tall, was scheduled for frontal sinusectomy due to sinusitis. General anesthesia was induced through propofol 80 mg, remifentanil 0.25 μg/kg/min and 40 mg rocuronium. We were successfully able to use a sugammadex on a patient suffering from KD in order to reverse rocuronium-induced neuromuscular blockade.

Statins and succinylcholine interaction: A cause of concern for serious muscular damage in anesthesiology practice!

Statins are being extensively used in cardiac patient throughout the globe. Succinylcholine has been the mainstay of profound relaxation during induction and intubation of anesthesia for almost six decades now. The interactive properties of these drugs have been of major concern during routine anesthesiology practice in the last few years. However, no major research trial, prospective studies or meta-analysis are available, which can truly allay the fears of possible potential negative synergistic interactions between these two commonly used drugs. Whatever the evidence is available is hardly enough to support a positive outcome and the results have been drawn from observations of only few small studies. As a result, a continuous need among anesthesiologist fraternity is felt to arrive at a suitable inference, which can predict definite consequences of this synergistic interaction. The present article reviews some of the important observations of few handful studies which were carried out to observe any potential adverse interactions between succinylcholine and statins.

Major surgical procedures in children with cerebral palsy

There are 3 surgical procedures that patients with cerebral palsy (CP) undergo that may be considered major procedures: femoral osteotomies combined with pelvic osteotomies, spine fusion, and intrathecal baclofen pump implant for the treatment of spasticity. Many complications are known to occur at a higher rate in this population, and some may be avoided with prior awareness of the preoperative pathophysiology of the patient with CP.

Immobilization with atrophy induces de novo expression of neuronal nicotinic α7 acetylcholine receptors in muscle contributing to neurotransmission

BACKGROUND

Mature acetylcholine receptor (AChR) isoform normally mediates muscle contraction. The hypothesis that α7AChRs up-regulate during immobilization and contribute to neurotransmission was tested pharmacologically using specific blockers to mature (waglerin-1), immature (αA-OIVA), and α7AChRs (methyllycaconitine), and nonspecific muscle AChR antagonist, α-bungarotoxin.

METHODS

Mice were immobilized; contralateral limbs were controls. Fourteen days later, anesthetized mice were mechanically ventilated. Nerve-stimulated tibialis muscle contractions on both sides were recorded, and blockers enumerated above sequentially administered via jugular vein. Data are mean ± standard error.

RESULTS

Immobilization (N = 7) induced tibialis muscle atrophy (40.6 ± 2.8 vs. 52.1 ± 2.0 mg; P < 0.01) and decrease of twitch tension (34.8 ± 1.1 vs. 42.9 ± 1.5 g; P < 0.01). Waglerin-1 (0.3 ± 0.05 μg/g) significantly (P = 0.001; N = 9) depressed twitch tension on contralateral (≥97%) versus immobilized side (approximately 45%). Additional waglerin-1 (total dose 1.06 ± 0.12 μg/g or approximately 15.0 × ED50 in normals) could not depress twitch of 80% or greater on immobilized side. Immature AChR blocker, αA-OIVA (17.0 ± 0.25 μg/g) did not change tension bilaterally. Administration of α-bungarotoxin (N = 4) or methyllycaconitine (N = 3) caused 96% or greater suppression of the remaining twitch tension on immobilized side. Methyllycaconitine, administered first (N = 3), caused equipotent inhibition by waglerin-1 on both sides. Protein expression of α7AChRs was significantly (N = 3; P < 0.01) increased on the immobilized side.

CONCLUSIONS

Ineffectiveness of waglerin-1 suggests that the twitch tension during immobilization is maintained by receptors other than mature AChRs. Because αA-OIVA caused no neuromuscular changes, it can be concluded that immature AChRs contribute minimally to neurotransmission. During immobilization approximately 20% of twitch tension is maintained by up-regulation of α-bungarotoxin- and methyllycaconitine-sensitive α7AChRs.

Pharmacodynamics of cisatracurium in the intensive care unit: an observational study

Background

Data from previous studies indicate that optimal conditions for intubation are met 120 seconds after administration of 0.15 mg.kg^-1 cisatracurium (ED95 × 3) following the induction of anesthesia. The aim of this study was to compare the doses required for complete paralysis after induction of anesthesia in ICU patients with the dose used in patients undergoing elective surgery.

Methods

Seventeen ICU patients undergoing percutaneous tracheostomy and 17 patients undergoing an elective surgical procedure under muscle relaxation were included. In both groups, an initial intravenous bolus of cisatracurium besylate was given at a dose of 0.15 mg.kg^-1 followed by repeated boluses of 0.03 mg.kg^-1 every four minutes. The objective was to obtain no response to the train-of-four (TOF). The contractile response of the corrugator supercilii muscle was monitored every minute by observing the TOF in response to a peripheral nerve stimulator with a constant current set to 60 mA.

Results

After the initial dose of cisatracurium, none of ICU patients (0/17) versus 15/17 of the elective surgery patients were completely paralyzed (P < 0.0001). There was a delay in the onset of neuromuscular blockade among the ICU patients. The cumulative doses of cisatracurium were significantly higher in the ICU group with 38 ± 14 mg (that is, 10 ± 4.7 ED95) versus 11 ± 2 mg (that is, 3 ± 0.3 ED95) in the elective surgery group (P < 0.0001).

Conclusion

The dosing of cisatracrurium for ICU patients, which is based on the dose recommended for elective anesthesia, is unsuitable because the onset is too slow. This phenomenon is probably caused by changes in the pharmacodynamics and pharmacokinetics. These data suggest that neuromuscular monitoring should be used in the ICU.

Collaborative approach in the development of high-performance brain-computer interfaces for a neuroprosthetic arm: translation from animal models to human control

Our research group recently demonstrated that a person with tetraplegia could use a brain-computer interface (BCI) to control a sophisticated anthropomorphic robotic arm with skill and speed approaching that of an able-bodied person. This multiyear study exemplifies important principles in translating research from foundational theory and animal experiments into a clinical study. We present a roadmap that may serve as an example for other areas of clinical device research as well as an update on study results. Prior to conducting a multiyear clinical trial, years of animal research preceded BCI testing in an epilepsy monitoring unit, and then in a short-term (28 days) clinical investigation. Scientists and engineers developed the necessary robotic and surgical hardware, software environment, data analysis techniques, and training paradigms. Coordination among researchers, funding institutes, and regulatory bodies ensured that the study would provide valuable scientific information in a safe environment for the study participant. Finally, clinicians from neurosurgery, anesthesiology, physiatry, psychology, and occupational therapy all worked in a multidisciplinary team along with the other researchers to conduct a multiyear BCI clinical study. This teamwork and coordination can be used as a model for others attempting to translate basic science into real-world clinical situations.

Pharmacodynamic changes with vecuronium in sepsis are associated with expression of α7- and γ-nicotinic acetylcholine receptor in an experimental rat model of neuromyopathy

BACKGROUND

Resistance to non-depolarizing neuromuscular blocking agents induced by sepsis is associated with the qualitative change in the nicotinic acetylcholine receptor (nAChR). This study aims to investigate the effects of sepsis on the neuromuscular block properties of vecuronium in relation to the expression of fetal and neuronal α7 type nAChR.

METHODS

Male Sprague-Dawley rats were randomly divided into sham and sepsis groups. Sepsis was induced by caecal ligation and puncture (CLP). The rats were injected i.v. with ulinastatin or normal saline on Day 10. Neuromuscular block properties of vecuronium were evaluated and neuromuscular function was assessed by electromyography on Days 1, 3, 7, and 14 after CLP. Expression of fetal and neuronal type α7-nAChR on the tibialis anterior muscle was assessed using immunohistochemistry and western blot. The mRNA encoding for γ- and α7 subunits was evaluated by real-time polymerase chain reaction.

RESULTS

The half maximal inhibitory response of vecuronium in the sepsis group significantly increased, peaked on Day 7, and then declined on Day 14 (P<0.05). The neuromuscular function decreased with increasing postoperation time in the sepsis group (P<0.05). Sepsis significantly increased the expression of γ- and α7-nAchR along with expression of γ- and α7 subunits mRNA, peaked on Day 7, and declined on Day 14 (P<0.05). Ulinastatin suppressed the expression of receptor protein and mRNA encoding for γ- and α7 subunits (P<0.05).

CONCLUSIONS

Pharmacodynamic changes with vecuronium seem to be associated with the expression of γ- and α7-nAChR in the skeletal muscle. Ulinastatin can improve this effect by inhibiting the expression of these receptors.

Neuromuscular effects of sevoflurane in patients with myasthenia gravis

The current study evaluated the neuromuscular responses following administration of sevoflurane in 14 patients with myasthenia gravis (MG) (I-IIb in Osserman's classification) scheduled for thymectomy and in 11 control patients (ASA I-II) who underwent elective surgery. The electromyographic (EMG) response of the abductor digiti minimi was measured following train-of-four (TOF) stimulation of the ulnar nerve every 20 s. After induction of anesthesia with a combination of 3-4 mg·kg(-1) thiopental and 1-2 μg·kg(-1) fentanyl with 66% N2O and oxygen, an inspired concentration of 4% sevoflurane was administered via a face mask for 7 min. Anesthesia was maintained during surgery with 66% N2O in oxygen and with 1 minimum alveolar concentration (MAC) of end-tidal concentration of sevoflurane. The T1 (the amplitude of the first response) values decreased more profoundly in the MG patients than in the control patients at the end of surgery (P<0.05). Following administration of 4% sevoflurane for 7 min, the TOFR (the ratio of the fourth TOF to the first response) values revealed depressions greater than 10% of preinhalation values in 11 of 14 MG patients with a marked individual variation. This attenuated response was followed by a further depression of the TOFR values with increasing time of 1 MAC sevoflurane anesthesia. On the other hand, no notable changes were observed in patients with normal neuromuscular functions. The most significant factor that correlated with the depression of the TOFR values induced by 1 MAC sevoflurane was the anti-AchR antibody titers (P=0.029). Our results indicate that MG patients have an increased neuromuscular sensitivity to sevoflurane.

Trauma in the elderly: considerations for anesthetic management

The volume of geriatric trauma patients is expected to increase significantly in coming years. Recognition of severe injuries may be delayed because they are less likely to mount classic symptoms of hemodynamic instability. Head injuries of any severity may place geriatric patients at increased risk of mortality, but there are currently no geriatric-specific treatment recommendations that differ from usual adult guidelines. Our understanding of best practices in geriatric trauma and anesthesia care continues to expand, as it does in all other areas of medicine.

The pharmacokinetics and pharmacodynamics of cisatracurium in critically ill patients with severe sepsis

AIM

To characterize the pharmacokinetics (PK) and pharmacodynamics (PD) of cisatracurium in critically ill patients with severe sepsis.

METHODS

Blood samples were collected before and over 8 h after a single bolus dose of cisatracurium 0.1 mg kg(-1) . Neuromuscular block was assessed by accelerometric peripheral nerve stimulation (TOF Watch). Plasma concentration and neuromuscular block data were fitted using population analysis.

RESULTS

Steady-state volume of distribution was determined to be 111 ± 71 ml kg(-1) and plasma clearance was 5.2 ± 1.8 ml min(-1) kg(-1) in these patients with greater inter-patient variability compared with other populations. The time to maximum block (8.3 ± 2.9 min) and delay time of transferring from central to effect compartment (17.2 min) was much longer, while the maximum block (95.0 ± 6.3%) was less compared with those in other patient populations. The effect compartment concentration resulting in 50% of maximum effect (128 ± 58 ng ml(-1)) was larger than previously described.

CONCLUSIONS

This study suggests that standard dosing of cisatracurium in patients with severe sepsis results in a slower patient response with a reduced effect. Use of a larger dose may overcome this reduced delayed response.

The limits of succinylcholine for critically ill patients

BACKGROUND

Urgent tracheal intubations are common in intensive care units (ICU), and succinylcholine is one of the first-line neuromuscular blocking drugs used in these situations. Critically ill patients could be at high risk of hyperkalemia after receiving succinylcholine because one or more etiologic factors of nicotinic receptor upregulation can be present, but there are few data on its real risk. Our objectives in this study were to determine the factors associated with arterial potassium increase (ΔK) and to assess the occurrence of acute hyperkalemia ≥6.5 mmol/L after succinylcholine injection for intubation in the ICU.

METHODS

In a prospective, observational study, all critically ill patients intubated with succinylcholine in an ICU were screened. Only intubations with arterial blood gases and potassium measurements before and after (K(after)) a succinylcholine injection were studied.

RESULTS

During 18 months, 131 critically ill patients were intubated after receiving succinylcholine with arterial potassium before and after intubation (K(after)) for a total of 153 intubations. After multivariate analysis, the only factor associated with ΔK was the length of ICU stay before intubation (ρ = 0.561, P < 0.001). The factors associated with K(after) ≥6.5 mmol/L (n = 11) were the length of ICU stay (P < 0.001) and the presence of acute cerebral pathology (P = 0.047). The threshold of 16 days was found highly predictive of acute hyperkalemia ≥6.5 with 37% (95% confidence interval: 19%-58%) of K(after) ≥6.5 after the 16th day compared with only 1% (95% confidence interval: 0%-4%) of K(after) ≥6.5 when succinylcholine was injected during the first 16 days.

CONCLUSIONS

This study shows that the risk of ΔK after succinylcholine injection is strongly associated with the length of ICU stay. The risk of acute hyperkalemia ≥6.5 mmol/L is highly significant after 16 days.

Succinylcholine-induced hyperkalemia in a patient with multiple sclerosis

BACKGROUND

Succinylcholine administration is associated with hyperkalemia in patients with a variety of medical conditions, including many neuromuscular disorders. Nonetheless, there is a paucity of literature describing hyperkalemia after the administration of succinylcholine to patients with multiple sclerosis.

CASE REPORT

This case report describes a 38-year-old woman with multiple sclerosis who developed life-threatening hyperkalemia after the administration of succinylcholine during rapid sequence intubation.

CONCLUSION

This case highlights the potential for iatrogenic hyperkalemia after succinylcholine in patients with neurologic diseases, including multiple sclerosis.