Malignant hyperthermia and myotonic disorders

Malignant hyperthermia: a case report with a literature review

Malignant hyperthermia is an extremely rare, potentially lethal disorder that occurs in susceptible patients who are exposed to triggering agents such as volatile anesthetic gases or depolarizing muscle relaxants. The clinical manifestations of malignant hyperthermia include hypermetabolism, hyperthermia, hypercapnia, and sustained skeletal muscle rigidity, which result in cardiac arrest, brain damage, and death. It is associated with a high morbidity and mortality rate if not recognized immediately and treated appropriately. We report a case of suspected malignant hyperthermia in a young male patient undergoing axillary osmidrosis surgery.

A case report of malignant hyperthermia in a patient with myotonic dystrophy type I: A CARE-compliant article

RATIONALE

Several hereditary myopathies that can predispose to malignant hyperthermia (MH) are reported. However, the risk of MH in myotonic dystrophy type I (DM1) has been suggested equal to general population, although the evidence is limited to only a few case reports.

PATIENT CONCERNS

We encountered a rare case of MH during anesthesia induction with sevoflurane in a male adolescent with previously undiagnosed DM1.

DIAGNOSES

After the event, genetic testing revealed the presence of a previously unknown heterozygous missense mutation in ryanodine receptor 1 (RYR1) associated with MH (c.6898T > C; p.ser2300Pro). Concomitantly, the patient was diagnosed with DM1 with abnormal cytosine-thymine-guanine triplet expansion in the DMPK gene.

INTERVENTIONS

Dantrolene was administered to treat the hypermetabolic manifestations in 20 minutes after the identification of MH.

OUTCOMES

The patient was successfully treated and discharged without any complications. Laboratory abnormalities were recovered to baseline at postoperative 4 days.

LESSONS

The authors suggest that possible MH susceptibility in DM1 patients may be refocused. Genetic testing can be a screening tool for MH susceptibility in these population, prior to receiving general anesthesia.

Relevance of pathogenicity prediction tools in human RYR1 variants of unknown significance

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle metabolism characterized by generalized muscle rigidity, increased body temperature, rhabdomyolysis, hyperkalemia and severe metabolic acidosis. The underlying mechanism of MH involves excessive Ca²⁺ release from myotubes via the ryanodine receptor type 1 (RYR1) and the voltage-dependent L-type calcium channel (CACNA1S). As more than 300 variants of unknown significance have been detected to date, we examined whether freely available pathogenicity prediction tools are able to detect relevant MH causing variants. In this diagnostic accuracy study, blood samples from 235 individuals with a history of a clinical malignant hyperthermia or their close relatives were genetically screened for RYR1 variants of all 106 RYR1 exons and additionally for known variants of CACNA1S. In vitro contracture tests were conducted on muscle biopsies obtained from all individuals, independently of whether a pathogenic variant, a variant of unknown significance or no variant was detected. Comparisons were made to three established bioinformatic pathogenicity detection tools to identify the clinical impact of the variants of unknown significance. All detected genetic variants were tested for pathogenicity by three in silico approaches and compared to the in vitro contracture test. Sensitivity and specificity of exon screening of all individuals listed in our MH database was analyzed. Exon screening identified 97 (41%) of the 235 individuals as carriers of pathogenic variants. Variants of unknown significance were detected in 21 individuals. Variants of unknown significance were subdivided into 19 malignant-hyperthermia-susceptible individuals and 2 non-malignant-hyperthermia-susceptible individuals. All pathogenic variants as well as the malignant-hyperthermia-suspectible variants were correctly identified by the bioinformatic prediction tools. Sensitivity of in silico approaches ranged between 0.71 and 0.98 (Polyphen 0.94 [CI 95% 0.75; 0.99]; Sift 0.98 [CI 95% 0.81; 0.99]; MutationTaster 0.92 [CI 95% 0.75; 0.99]). Specificity differed depending on the used tool (Polphen 0.98 [CI 95% 0.32; 0.99]; Sift 0.98 [CI 95% 0.32; 0.99]; MutationTaster 0.00 [CI 95% 0.00; 0.60]). All pathogenic variants and variants of unknown significance were scored as probably damaging in individuals, demonstrating a high sensitivity. Specificity was very low in one of the three tested programs. However, due to potential genotype–phenotype discordance, bioinformatic prediction tools are currently of limited value in diagnosing pathogenicity of MH-susceptible variants.

Hypermetabolism in B-lymphocytes from malignant hyperthermia susceptible individuals

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle metabolism which is characterized by generalized muscle rigidity, increased body temperature, rhabdomyolysis, and severe metabolic acidosis. The underlying mechanism of MH involves excessive Ca(2+) release in myotubes via the ryanodine receptor type 1 (RyR1). As RyR1 is also expressed in B-lymphocytes, this study investigated whether cellular metabolism of native B-lymphocytes was also altered in MH susceptible (MHS) individuals. A potent activator of RyR1, 4-chloro-m-cresol (4-CmC) was used to challenge native B-lymphocytes in a real-time, metabolic assay based on a pH-sensitive silicon biosensor chip. At the cellular level, a dose-dependent, phasic acidification occurred with 4-CmC. The acidification rate, an indicator of metabolic activation, was significantly higher in B-lymphocytes from MHS patients and required 3 to 5 fold lower concentrations of 4-CmC to evoke similar acidification rates to MHN. Native B-lymphocytes from MHS individuals are more sensitive to 4-CmC than those from MHN, reflecting a greater Ca(2+) turnover. The acidification response, however, was less pronounced than in muscle cells, presumably reflecting the lower expression of RyR1 in B-lymphocytes.

Neurologic disease with pregnancy and considerations for the obstetric anesthesiologist

Women with neurologic conditions present a challenge during pregnancy and in the peripartum period. Given the low prevalence of these diseases during pregnancy, most management decisions are guided by retrospective reviews and case reports. This article reviews current literature for some of the more common or complex neurologic conditions affecting pregnancy with special consideration for anesthetic management. In particular, epilepsy; multiple sclerosis; primary intracranial hypertension; secondary intracranial hypertension-Arnold-Chiari malformations and intracranial neoplasms; spinal cord injury; neuromuscular junction disorders-myasthenia gravis; and hereditary neuromuscular disorders-myotonic dystrophy and spinal muscular atrophy will be discussed. By increasing understanding of anesthetic issues for parturients with neurologic disease, providers may more effectively anticipate anesthetic considerations, thereby optimizing care plans.

In vitro muscle contracture investigations on the malignant hyperthermia like episodes in myotonia congenita

BACKGROUND

A common form of congenital myotonia, myotonia congenita (MC), is caused by mutations in the skeletal muscle Cl(-) channel gene type 1 (CLCN1). Due to the reduced Cl(-) conductance of the mutated channels, the patients may develop generalized muscle rigidity and hypermetabolism during general anaesthesia. The clinical symptoms resemble malignant hyperthermia (MH), which may lead to mistreatment of the patient.

METHODS

Muscle specimens of ADR mice (an animal model of MC) as well as of human individuals were used and exposed to potent ryanodine receptor type 1 (RyR1) activators and increasing K(+) concentration. Muscle force was monitored by a standardized diagnostic method for MH, the so-called in vitro contracture test.

RESULTS

Neither muscle of ADR mice nor MC muscle (murine and human myotonic muscle) showed pathological contractures after exposure to the potent RyR1 agonists caffeine and halothane. Increasing concentrations of K(+) had a dose-dependent preventive effect on myotonic stiffness.

CONCLUSION

We conclude that the adverse anaesthetic MH-like episodes observed in MC patients do not primarily originate from an altered Ca(2+) release in skeletal muscle. In MC muscle, this hypermetabolism is facilitated by a (pharmacologically induced) sustained depolarization due to an instable membrane potential. The in vitro results suggest that these patients benefit from tight K(+) monitoring because of the membrane potential stabilizing effect of K(+) .

Neuromuscular disease and anesthesia

Patients with neuromuscular disease pose many anesthetic challenges and are at greater risk for perioperative complications, including respiratory or cardiovascular dysfunction and pulmonary aspiration. Therefore, these patients require special precautions, including interdisciplinary communication between primary care physicians, neurologists, physiatrists, surgeons, and anesthesiologists. Preoperative evaluation and optimization of comorbid conditions is critical. These patients may have adverse response to neuromuscular blocking drugs and the reversal drugs (e.g., neostigmine). They should be used with caution and titrated based on objective neuromuscular monitoring. Drugs that potentiate neuromuscular blocking drugs should also be avoided or their doses limited if possible. The risk of malignant hyperthermia in certain neuromuscular diseases mandates avoidance of triggering agents such as succinylcholine and inhaled anesthetics. Patients with neuromuscular disease may also be sensitive to sedative-hypnotics and opioids, which should be used judiciously. Finally, the postoperative period requires close monitoring due to increased risk of postoperative cardiorespiratory dysfunction.

Myotonia congenita with strabismus in a large family with a mutation in the SCN4A gene

BACKGROUND/AIMS

To determine the genetic basis of myotonia congenita (MC) and strabismus in a large Caucasian family.

METHODS

Seven patients making up four generations of a family with MC and strabismus were recruited. All patients had at least one standard ophthalmic examination, including best-corrected visual acuity, refraction, and ocular motility measurements. CLCN1 and SCN4A genes were sequenced and analysed for mutations.

RESULTS

Five out of the seven family members were diagnosed with MC by clinical history and electromyography. Ophthalmic history and exam revealed eyelid myotonia and strabismus. All patients with MC were diagnosed with strabismus between the ages of 3 and 6 and required surgical restoration of ocular alignment. Sequencing results revealed a c. 1333G>A; p. Val445Met mutation in the SCN4A gene.

CONCLUSION

There are few reports describing eyelid myotonia and strabismus in patients diagnosed with MC. We found significant ocular involvement in a family with a mutation in SCN4A. Future studies may confirm that MC with significant ocular involvement can be used to direct genetic analysis.

Spinal blocks

Every anesthetist should have the expertise to perform lumbar puncture that is the prerequisite to induce spinal anesthesia. Spinal anesthesia is easy and effective technique: small amount of local anesthetic injected in the lumbar cerebrospinal fluid provides highly effective anesthesia, analgesia, and sympathetic and motor block in the lower part of the body. The main limitation of spinal anesthesia is a variable and relatively short duration of the block with a single-injection of local anesthetic. With appropriate use of adjuvant or combining spinal anesthesia with epidural anesthesia, the analgesic action can be controlled in case of early recovery of initial block or in patients with prolonged procedures. Contraindications are rare. Bleeding disorders and any major dysfunction in coagulation system are rare in children, but spinal anesthesia should not be used in children with local infection or increased intracranial pressure. Children with spinal anesthesia may develop the same adverse effects as has been reported in adults, but in contrast to adults, cardiovascular deterioration is uncommon in children even with high blocks. Most children having surgery with spinal anesthesia need sedation, and in these cases, close monitoring of sufficient respiratory function and protective airway reflexes is necessary. Postdural puncture headache and transient neurological symptoms have been reported also in pediatric patients, and thus, guardians should be provided instructions for follow-up and contact information if symptoms appear or persist after discharge. Epidural blood patch is effective treatment for prolonged, severe headache, and nonopioid analgesic is often sufficient for transient neurological symptoms.

Neuroleptic malignant syndrome: mechanisms, interactions, and causality

This review focuses on new data from recent publications concerning how compounding interactions between different thermoregulatory pathways influence the development of hyperthermia and/or neuroleptic malignant syndrome (NMS), and the fundamental issue of the presumed causal role of antipsychotic drugs. The formal criteria for substantiating cause-effect relationships in medical science, established by Hill, are applied to NMS and, for comparison, also to malignant hyperthermia and serotonin toxicity. The risk of morbidities related to hyperthermia is reviewed from human and experimental data: temperatures in excess of 39.5°C cause physiological and cellular dysfunction and high mortality. The most temperature-sensitive elements of neural cells are mitochondrial and plasma membranes, in which irreversible changes occur around 40°C. Temperatures of up to 39°C are "normal" in mammals, so, the term hyperthermia should be reserved for temperatures of 39.5°C or greater. The implicitly accepted presumption that NMS is a hypermetabolic and hyperthermic syndrome is questionable and does not explain the extensive morbidity in the majority of cases, where the temperature is less than 39°C. The thermoregulatory effects of dopamine and acetylcholine are outlined, especially because they are probably the main pathways by which neuroleptic drugs might affect thermoregulation. It is notable that even potent antagonism of these mechanisms rarely causes temperature elevation and that multiple mechanisms, including the acute phase response, stress-induced hyperthermia, drugs effects, etc., involving compounding interactions, are required to precipitate hyperthermia. The application of the Hill criteria clearly supports causality for drugs inducing both MH and ST but do not support causality for NMS.

The risk of malignant hyperthermia in children undergoing muscle biopsy for suspected neuromuscular disorder

BACKGROUND

It is assumed that those children with known or suspected neuromuscular disorders (NMD) are at increased risk for malignant hyperthermia (MH). Despite the lack of conclusive data, most of these children are managed with a nontriggering anesthetic. This study examined the risk of MH in children exposed to a triggering anesthetic while undergoing muscle biopsy for suspected NMD.

METHODS

Between 1992 and 2005, the medical records of 351 children under 21 years of age were identified as having undergone muscle biopsy for suspected NMD. Of these, only 274 received a volatile anesthetic agent or succinylcholine and were included for study. Records were examined for evidence of MH or rhabdomyolysis.

RESULTS

No patient exhibited signs or symptoms suggestive of MH. One patient was found, by muscle biopsy, to have evidence of rhabdomyolysis prior to exposure to a volatile anesthetic. Of 274 patients, only three received succinylcholine. None developed MH or rhabdomyolysis. The estimated risk of a patient with suspected NMD developing MH as a result of exposure to volatile anesthetic agents during muscle biopsy is 1.09% or less.

CONCLUSION

The estimated risk of MH or rhabdomyolysis is 1.09% or less in a diverse population of children with suspected NMD.

A case report of malignant hyperthermia in a dental clinic operating room

A healthy 5-year-old boy presented for arch bar placement under general anesthesia in an operating room in a dental school. The patient had previously undergone general anesthesia without complication, and no family history of anesthetic problems were reported. Halothane mask induction, intravenous catheter placement, and nasal intubation proceeded uneventfully without the aid of a muscle relaxant. Halfway through the procedure, signs and symptoms of malignant hyperthermia, including muscle rigidity, hypercarbia, tachypnea, and tachycardia were noted. Immediate treatment, including discontinuation of the triggering agent, dantrolene administration, and cooling measures were applied, and once stable, the child was transferred to Columbus Children's Hospital for further management. The patient experienced no postoperative complications. Further discussion regarding the pathophysiology and management of malignant hyperthermia is provided.

Scoliosis in Steinert syndrome: a case report

BACKGROUND CONTEXT

Steinert syndrome is described as an autosomal dominant condition characterized by progressive muscular wasting, myotonia, musculoskeletal manifestations and rare spinal defects. Little is reported about spinal deformity associated with this syndrome.

PURPOSE

We present a patient with Steinert syndrome complicated by scoliosis. In the literature on muscular dystrophy, other than Duchenne, little mention is given to the problem of scoliosis in general and its treatment in particular.

STUDY DESIGN

A case report of a patient with Steinert syndrome associated with thoracic scoliosis and hypokyphosis is presented.

METHODS

A 17-year-old boy presented with King type II right thoracic scoliosis (T5-T11, Cobb angle of 40 degrees) and hypokyphosis--10 degrees. He was treated with posterior stabilization and instrumentation at level T3-L2 with a postoperative correction of the scoliotic curve to 20 degrees. Histopathologic examination of the muscles confirmed the diagnosis of Steinert myotonic dystrophy.

RESULTS

At 30-month follow-up, the patient was clinically pain free and well balanced. Plain radiographs showed solid spine fusion with no loss of deformity correction.

CONCLUSIONS

Scoliosis in Steinert syndrome shares the characteristic of an arthrogrypotic neuromuscular curve and demands the extensive soft tissue release for optimal surgical correction. Intraoperative observations included profound tissue bleeding, abnormally tough soft tissues and a difficult recovery from anaesthesia.

Atypical Neuroleptic Malignant Syndrome Presenting as Fever of Unknown Origin in the Elderly

A 79-year-old nursing home resident who was taking olanzapine presented to multiple hospitals with fevers of unknown origin. After an extensive workup to rule out infection, the patient was diagnosed as having neuroleptic malignant syndrome (NMS). This patient's presentation was atypical because of the lack of rigidity or tremor at the time of admission. This case highlights the importance of including NMS in the differential diagnosis of fever of unknown origin in medical patients. A review of the medical literature is taken, focusing on diagnoses, prevalence, predisposing factors, pathophysiology, and current treatment approaches for NMS.

Management of drug-induced hyperthermia

PURPOSE OF REVIEW

To review the current literature describing drug-induced hyperthermia and its treatment. Specifically, five syndromes will be discussed: malignant hyperthermia, neuroleptic malignant syndrome, anticholinergic poisoning, sympathomimetic poisoning, and serotonin syndrome.

RECENT FINDINGS

The most recent findings in the literature are the recognition of previously undescribed drugs or drug combinations that have lead to hyperthermia. Recent literature also attests to the potential morbidity and mortality of drug-induced hyperthermia.

SUMMARY

Although the recognition of causative agents is increasing, the treatment of drug-induced hyperthermia remains unchanged and continues to be primarily supportive.

Pyloromyotomy in a patient with paramyotonia congenita

A 2-mo-old infant with paramyotonia congenita was scheduled for pyloromyotomy and repair of inguinal hernia. Diagnosis of paramyotonia congenita was done with positive family history, myotonia at eyelids, provocation by cold, and electromyogram analysis. Anesthesia was induced via face mask with sevoflurane at 4 minimum alveolar anesthetic concentration in oxygen. Tracheal intubation was attempted without a neuromuscular relaxant. Anesthesia was maintained with sevoflurane at 0.5 minimum alveolar anesthetic concentration in oxygen and remifentanil infusion at a rate of 0.2 micro g. kg(-1). min(-1). After discontinuation of sevoflurane and remifentanil, the patient was awake and had full recovery of muscle activity.

IMPLICATIONS

The literature concerning general anesthesia in paramyotonic patients is limited. We report a case of paramyotonia congenita in a 2-mo-old male infant undergoing surgery for pyloric stenosis and inguinal hernia after an uneventful anesthesia.