Fight for a Future

ANESTHESIA IN DMD

In the last 20 years many deaths during surgeries of DMD patients have been documented, many of which did not have a DMD diagnosis before surgery. The indications are similar to those observed in malignant hypertermia. The muscle biopsy of DMD patients shows contractures in the halothane-caffeine test(as it occurs in the malignant hipertermia) but many have normal results. Malignant Hypertermia is a heterogeneous entity and DMD is a distinct entity, but in both, the the results of the anesthesia is the same one, rhabdomyolysis.

Rhabdomyolysis is an injury of the skeletal muscles that leads to a potassium, creatine kinase (CK) and myoglobin release in the sanguineous circulation. Beyond being able to promote cardiac arrest from potassium excess, excess of CK and myoglobina can provoke damage to renal function.

Unlike malignant hyperthermia, the patients with DMD with a result of rhabdomyolysis induced by anesthetics do not present hypercapnia (increase of paCO2) or high temperature. The treatment of both these entities results in the same way: administration of dantrolene, which reduces mortality; this drug acts directly in the contractil mechanism of the skeletal muscle cell, blocking the calcium release of the sarcoplasmatic reticulum, reducing muscle tone and the production of heat.

Succinylcholin and assymptomatic children
Succinylcholin is a depolarizing blocking agent (muscle relaxant) and it is associated with cardiac arrest and reactions in malignant hipertermia type- in assymptomatic children, many of which had been later diagnosed as carriers of myopathy and many with DMD. Many works suggest that the drug does not have to be used in children, the recommendation of the FDA from 1992, except in emergency situations where it is used for the orotraqueal intubation.

Succinylcholin can promote rise of the seric potassium levels, without rabdomyolisis, since it can cause arrhythmias and cardiac arrest.

Inalatory Anaesthetics and rhabdomyolysis
Rhabdomyolysis and cardiac arrest with the use of inalatory agents without the succinylcholin use had been described. Although to have much documentation of surgeries with inalatory agents without side effects, its use must be prevented whenever possible. DMD patients can be submitted to the surgeries with the follow cares:

Care before the surgery : as patients with DMD can be carriers of alterations of the pulmonary and cardiac function, and frequently do few physical activities, these alterations may not be recognized. The cardio-pulmonary evaluation must be rigorous, with attention to the history of repetitious infections, secretion retention, inability to cough and other. Specialized examinations frequently are necessary: pulmonary function test, EKG, echocardiogram and others.

Slow emptying of gastric material has been found in DMD carriers and indicates that more fasting is necessary before the surgery. The use of drugs to reduce the gastric acidity and prevention against aspiration of the gastric juice can be necessary.

Patients with alterations of the CNS (Central Nervous System) may not be cooperative.
The anesthetist must be careful of the toracic alterations and contractures that the patient can present tobe prepared with regard to intubation, that can be made difficult, and with regard to positioning of the patient in surgery .

Anesthesics care during the anesthesia : the use of inalatory anaesthetics and succinylcholin as displayed above must be contraindicated.

The use of not-depolarizing blocking agents as vecuronium, antracuronium and mivacurium are probably safe, but they must be used in reduced doses.

Intravenous anaesthetics have not demonstrated problems in patients with DMD, however, as cardiac alterations can be a given in these patients, they can be more sensitive to the effect of cardiac depressors, barbiturates and propofol.

Drugs as the opiates, hypnomidate and midazolam are, also, probably safe.

Care after the surgery : After the anesthesia the care must be increased; with the reduction of the effect of anesthetics, much attention must be given to the respiratory function; many times the patients need ventilation for longer to prevent the hypoventilation (reduction of the respiratory rhythm), difficulties to cough and to prevent the pulmonary aspiration.

Cardiac arrest and “hyperthermia malignant like” can be observed after the surgery.

The rank of the patient in lateral position reduces the pulmonary risk of aspiration.

Regional Anesthesia : regional or local anesthesia has been used without complications in DMD. Complications are rare in these techniques. Intravenous regional anesthesia also can be used.

26/11/03: Blood loss during posterior spinal fusion surgery in patients with neuromuscular disease: is there an increased risk?.

EDLER, ALICE MD, MA (EDUC) ; MURRAY, DAVID J. MD ; FORBES, ROBERT B. MD

Paediatric Anaesthesia. 13(9):818-822, November 2003. Abstract Background: Scoliosis surgery in paediatric patients can carry significant morbidity associated with intraoperative blood loss and the resultant transfusion therapy. Patients with neuromuscular disease may be at an increased risk for this intraoperative blood loss, but it is unclear if this is because of direct vascular pathophysiological changes or the fact that neuromuscular patients typically have more extensive orthopaedic disease and more vertebral segments involved. This study examined the risk of extensive blood loss (>50% of total blood volume) in patients with neuromuscular disease compared with patients who did not have neuromuscular disease when the extent of the surgery (number of segments fused), age and preoperative coagulation profile where taken into consideration.

Methods: Retrospective chart review of 163 paediatric patients was preformed. Patients who carried a diagnosis of preexisting neuromuscular disease were classified as such. Idiopathic, traumatic and iatrogenic scoliosis were classified as nonneuromuscular. Extensive blood loss was defined as >50% of estimated total blood volume. Logistic regression was used to predict the risk of extensive blood loss between the two groups when age, weight, extent of surgery was controlled for and anaesthetic and surgical techniques remained similar.

Results: Patients with neuromuscular disease did not vary significantly in age, weight, or preoperative haematocrit and platelet count from patients without neuromuscular disease. Neuromuscular patients did have significantly more vertebral segments fused. When this difference was controlled for statistically, neuromuscular patients had an almost seven times higher risk (adjusted odds ration 6.9, P < 0.05) of losing >50% of their estimated total blood volume during scoliosis surgery.

Conclusions: Patients with neuromuscular disease can present various anaesthetic challenges during scoliosis surgery, among these is the inherent risk of extensive blood loss. Recognizing this may help anaesthesiologists and surgeons more accurately prepare for and treat intraoperative blood loss during scoliosis surgery in patients with neuromuscular disease.

1) COPING WITH ANESTHESIA
Neuromuscular Disorders Pose Special Risks, But Preparation Minimizes Dangers
http://www.mdausa.org/publications/Quest/q73anesthesia2.html

2) Sevoflurane can induce rhabdomyolysis in Duchenne's muscular dystrophy
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11889791&dopt=Abstract

3) Current Concepts in Malignant Hyperthermia
Journal of Clinical Neuromuscular Disease 2002; 4(2):64-74

Josef Finsterer, MD, PhD

Malignant hyperthermia (MH) is a rare, potentially lethal, clinically and genetically heterogeneous pharmacogenic myopathy, which during or after general anesthesia manifests as MH crisis (MHC) in genetically predisposed, but otherwise mostly normal, individuals (MH susceptibles) in response to anesthetic-triggering agents. MHC can also occur in patients with central core disease. MCH-like crises have been reported in those with Duchenne/Becker muscular dystrophy, myotonic dystrophy, mitochondriopathy, and various other conditions. MH susceptibility is diagnosed if there is an MHC in the individual or family history or by the in vitro caffeine-halothane contracture test. Although screening for mutations in the ryanodine-receptor-1 gene and the dihydropyridine-receptor gene, respectively, could further substantiate the diagnosis, the caffeine-halothane-contracture test still remains the gold standard for diagnosing MH susceptibility. The most well-known triggers of an MHC are depolarizing muscle relaxants and volatile anesthetics. Therapy of an MHC comprises discontinuation of triggering agents, oxygenation, and correction of the acidosis and electrolyte disturbances, treatment of arrhythmias, cooling, and dantrolene. If MH susceptibility is not known preoperatively and an MHC unexpectedly interrupts anesthesia, consultation by a specialist in MH susceptibility after anesthesia is essential to investigate the patient for MH susceptibility or subclinical myopathy, guide laboratory investigations, manage therapy, and counsel the family on further risk. To further reduce morbidity and mortality of those with MHC, anesthesiologists and neurologists should be well educated and should strengthen their clinical vigilance. Research should be intensified and extended with regard to the development of new in vitro tests to further elucidate the heterogeneous genetic background of MH susceptibility.<o:p></o:p>

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