Neuromuscular disorders: relevance to anaesthesia and intensive care

Neuromuscular diseases are relatively rare but it is important for both anaesthetists and intensivists to have a working knowledge of the common diseases, as they may complicate general anaesthesia and result in neurogenic respiratory failure. The most common neurological condition seen in the intensive care unit is that of critical illness neuropathy; this subject is covered elsewhere in the journal. The diseases most commonly encountered in general anaesthetic practice include motor neurone disease, Guillain-Barré syndrome, botulism, myasthenia gravis and the muscular dystrophies.     

Neuromuscular disorders: relevance to anaesthesia and intensive care

Neuromuscular diseases are relatively rare, but it is important for both anaesthetists and intensivists to have a working knowledge of the common diseases as they may complicate general anaesthesia and result in neurogenic respiratory failure. The most common neurological condition seen in the intensive care unit is that of critical illness neuropathy; this subject is covered elsewhere in the journal. The diseases most commonly encountered in general anaesthetic practice include motor neurone disease, Guillain-Barré syndrome, botulism, myasthenia gravis and the muscular dystrophies.     

Blood loss during posterior spinal fusion surgery in patients with neuromuscular disease: is there an increased risk?

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.     

Pompe''s disease and anaesthesia

A case report of a child with Pompe's disease (glycogen storage disease Cori type II), who underwent two general anaesthetics, is presented. The progressive infiltration of heart and skeletal muscle with glycogen results in a severe form of cardiomyopathy and respiratory muscle weakness. Consequently, there are significant problems in the anaesthetic management of these patients. Although there are theoretical attractions for some anaesthetic drugs, the key factors in a successful outcome are attention to anaesthetic technique and close monitoring.     

Perioperative management of patients with musculoskeletal disease and for the burns patient

Musculoskeletal disease may present as isolated joint disease, a severe multisystem disorder or a neuromuscular disorder affecting the musculoskeletal system. Thorough preoperative assessment is essential to plan the surgical management of this group of patients. Assessment of the severity of cardiorespiratory disease may be difficult with severely limited mobility. The airway and neck may be involved so early anaesthetic opinion is essential. Drug therapy may need to be modified or stopped perioperatively. Intraoperative positioning and thermoregulation can be difficult to achieve and postoperative analgesia needs to be carefully planned to avoid respiratory depression in this vulnerable group.     

Hereditary haemorrhagic telangiectasia in pregnancy: regional and general anaesthesia

Hereditary haemorrhagic telangiectasia, also known as Osler–Weber–Rendu disease, is a rare autosomal dominant multisystem disorder, characterised by mucocutaneous telangiectases and arteriovenous malformations affecting any organ. The physiological changes in pregnancy pose significant obstetric and anaesthetic challenges for women affected by the disease. The optimal timing and mode of delivery requires careful consideration; and the benefits and risks of both regional and general anaesthetic techniques must be carefully considered, depending on the organs affected. This case report describes the successful management of a patient with this disease and severe pulmonary involvement, who received both regional and general anaesthesia as a result of a complication in the initial anaesthetic plan. The report demonstrates the benefits of a multidisciplinary approach to a complex case, achieved through providing care in a tertiary centre with appropriate expertise and resources.     

Caesarean section in a patient with haemoglobin SC disease and a phaeochromocytoma

The anaesthetic management of a patient with haemoglobin SC disease for lower segment Caesarean section and excision of a phaeochromocytoma is described. The patient was given a general anaesthetic for the surgical procedure after exchange transfusion had achieved an haemoglobin A concentration of greater than 50%. A live infant was delivered and a suprarenal phaeochromocytoma was excised during a 6.5 hour procedure. The patient's postoperative recovery was uneventful.     

The use of remifentanil in general anaesthesia for Caesarean section in a patient with mitral valve disease

We report the use of remifentanil as part of a general anaesthetic technique for a patient with mixed mitral valve disease, asthma and pre-eclampsia presenting for an emergency Caesarean section. The use of remifentanil was associated with stable haemodynamic variables during general anaesthesia. No clinically significant respiratory depression was noted in the neonate.     

Perioperative management of patients with musculoskeletal disease and for the burns patient

Musculoskeletal disease may present as isolated joint disease, a severe multisystem disorder or a neuromuscular disorder affecting the musculoskeletal system. Thorough preoperative assessment is essential to plan the surgical management of this group of patients. Assessment of the severity of cardiorespiratory disease may be difficult with severely limited mobility. The airway and neck may be involved so early anaesthetic opinion is essential. Drug therapy may need to be modified or stopped perioperatively. Intraoperative positioning and thermoregulation can be difficult to achieve and postoperative analgesia needs to be carefully planned to avoid respiratory depression in a vulnerable group.Patients with burns may present in the emergency department for urgent assessment or for early surgery to excise the burn and graft the defect. There may be an inhalational injury which if severe will require urgent treatment often with intubation and ICU care. A major burn is also a multisystem disorder and again there are challenges with airway management positioning and thermoregulation. These patients present for repeated surgeries and can suffer extreme emotional and psychological strain as a result of the burn insult.     

Anaesthetic considerations for patients with a pre‐existing neurological deficit: are neuraxial techniques safe?

Pre-existing neurological and muscular disease may be a specific concern for anaesthetists as they need to consider the effect of anaesthesia upon the disease, vice versa, and the interaction of anaesthesia with the medication taken by the patient. Despite a lack of controlled studies, many anaesthetists, being afraid of a claim, will prefer general rather than regional anaesthesia in these patients. Nevertheless regional anaesthesia certainly merits its place because it offers undeniable advantages. A good pre-operative examination is very important while patients should also be informed about peri-operative implications of anaesthesia, surgery and stress. Paraesthesias, epinephrine and high concentrations of local anaesthetics should be avoided in the majority of the diseases. Some diseases may benefit from epidural anaesthesia while for others a spinal technique may be the technique of preference. Special attention should be paid to patients with spinal stenosis despite recent reassuring reports with respect to safety of regional anaesthetic techniques. Anaesthetists should not automatically take all responsibility in case of progressive or new deficit after the procedure.     

Train of four fade in a child with stiff baby syndrome

A case is described of a child with stiff baby syndrome who underwent open reduction and femoral shortening of congenital dislocated hip under general anaesthesia. Neuromuscular function was measured electromyographically and demonstrated a great degree of train of four fade (57%) after sevoflurane inhalational induction of anaesthesia. The response to suxamethonium (2 mg x kg(-1)) was normal. The neuromuscular response to volatile anaesthetic agents and suxamethonium may be abnormal in these children with stiff baby syndrome and intraoperative neuromuscular monitoring is recommended.     

Response to single twitch or single burst stimulation of the ulnar nerve as predictive guide for intubating conditions

Disappearance of response to single twitch stimulation (STS) or train-of-four stimulation (TOF) of the ulnar nerve is insufficient as predictive guide for intubating conditions during onset of non-depolarizing neuromuscular block. Double burst stimulation (DBS) appears to be a more reliable indicator of the optimal time for intubation. In the present study, the disappearance of tactile detectable response to 0.1 Hz single twitch stimulation (STS) of the ulnar nerve was compared with disappearance of response to 0.1 Hz single burst stimulation (three stimuli at 50 Hz=SBS) as predictor for optimal intubating conditions during onset of block induced by 0.08 mg . kg^-1 of vecuronium in 100 patients under light general anaesthesia where thiopentone was used as the sole anaesthetic. Intubation was performed immediately after disappearance of the twitch response. Likewise 0.05 Hz STS and 0.05 Hz SBS stimulation were compared under identical circumstances in another 100 patients. Intubating conditions were unacceptable in 10%, 14%, 8% and 10% of the patients in the 0.1 Hz STS, 0.1 Hz SBS, 0.05 Hz STS and 0.05 Hz SBS groups, respectively. There were no significant differences between the groups. In conclusion, neither absence of response to STS stimulation nor absence of response to SBS stimulation of the ulnar nerve at either 0.1 Hz or 0.05 Hz frequency does guarantee acceptable intubating conditions during onset of neuromuscular block induced by vecuronium 0.08 mg . kg^-1 when thiopentone is used as the sole anaesthetic.     

Recovery from neuromuscular blockade. A comparison between old and young patients

Thirteen young and thirteen elderly patients undergoing elective surgery were given an anaesthetic using tubocurarine as the sole muscle relaxant. Following reversal with neostigmine, the time taken to recover from neuromuscular blockade was measured. No significant difference was found between the two groups of patients.     

Alzheimer's disease and anaesthesia: implications for the central cholinergic system

Alzheimer's disease (AD) is associated with a loss of cholinergicneurons resulting in profound memory disturbances and irreversibleimpairment of cognitive function. The central cholinergic systemis involved in the action of general anaesthetic agents. Anaestheticmodulation of cholinergic transmission has profound effectson brain function via a cascade of synaptic and postsynapticevents by binding both nicotinic and muscarinic receptors. Duringgeneral anaesthesia, decrease in acetylcholine release and depressionof cholinergic transmission facilitates the desirable effectsof general anaesthetics, such as loss of consciousness, pain,voluntary movements and memory. From this point of view, patientswith AD, characterized by a compromised neuronal transmission,represent particular cases in which the choice of anaesthesiadrugs may have a negative effect on the postoperative outcome.A future challenge may be the identification of brain targetsof general anaesthetics which do not expose patients to postoperativecognitive dysfunction, nor interfere with prognosis of braindegenerative disease.     

The onset of ablation of the evoked adductor pollicis muscle twitch in children: a clinical perspective

The time to loss of the adductor pollicis muscle response to ulnar nerve stimulation at 1 Hz (twitch) after succinylcholine, 1.5 mg.kg-1 intravenously (IV), or vecuronium, 0.1 mg.kg-1 (IV), administration was assessed visually in 134 children, age 2-13 yr, during clinically determined, deep halothane, enflurane and isoflurane anaesthesia. The overall time to twitch ablation and duration of succinylcholine's action is in agreement with published times obtained under controlled experimental conditions; the onset time following vecuronium is comparable to those observed during a similar anaesthetic background measured under controlled experimental conditions. Twitch ablation after succinylcholine was achieved in half the time needed following vecuronium regardless of anaesthetic agent. Succinylcholine's and vecuronium's onset time as well as succinylcholine's duration is adequately assessed by the outlined, simple clinical means. The choice of inhalation agent does not affect the time to visible twitch ablation in a clinically relevant manner; nor does it make an appreciable difference, in clinical terms, in succinylcholine's duration of action.     

Anaesthetic management of parturients with hereditary haemorrhagic telangiectasia for caesarean section

Hereditary haemorrhagic telangiectasia, also known as Osler-Weber-Rendu disease, is a vascular disorder characterized by multiple mucocutaneous and visceral arteriovenous malformations. There is little in the literature about the anaesthetic management of parturients with this condition. We report the anaesthetic management for caesarean section of two such parturients. One patient, with significant pulmonary involvement, received neuraxial anaesthesia for caesarean delivery. The second patient had general anaesthesia because investigations could not rule out neurological involvement. We review and discuss the anaesthetic considerations for obstetric patients with hereditary haemorrhagic telangiectasia.     

Anaesthesia and endovascular surgery

Anaesthetic requirements for endovascular surgery for aortic, carotid and peripheral vascular disease are reviewed. Peculiarities of the surgery which may impinge on anaesthetic management are discussed together with the pre-operative assessment issues of particular relevance to patients with generalized vascular disease. The detailed anaesthetic management for carotid and aortic endovascular repair is addressed. The lowered peri-operative stress and general morbidity levels which occur with endovascular surgery allow sicker patients with greater risk factors to present for this type of surgery, thus increasing the challenges facing anaesthetists.     

Obstetric anaesthesia in dystrophia myotonica

Two patients with dystrophia myotonica presented for urgent Caesarean section. Their per- and postoperative courses illustrate the anaesthetic problems posed by this disease. Respiratory difficulties are compounded by pregnancy and there is increased susceptibility to uterine haemorrhage. Choice of anaesthetic agent is discussed. Both had general anaesthetics; muscle relaxation was achieved with vecuronium.     

The obstetrical anaesthesia assessment clinic: a review of six years experience

We reviewed the out-patient consultation notes of 136 pregnant women seen at the Ottawa Civic Hospital from 1985 to 1991 to evaluate the efficiacy of an Obstetric Anaesthesia Assessment Clinic (OAC). In addition, their anaesthetic records from labour and delivery were reviewed. For each patient the reason for referral was recorded according to the involved organ system. The anaesthetic management at delivery was compared with the proposed anaesthetic plan by the OAC consultant (obstetric anaesthetist). The majority of women 84 (62%) had complaints related to the musculo-skeletal system. In addition, 18 patients were referred because of previous anaesthetic problems, ten with a history of cardiac disease, and eight with neurological disease. Lumbar epidural analgesia (LEA) was a safe and effective choice for parturients with low back pain, history of lumbar fractures or single level discectomies without lumbar fusion. Parturients with posterior instrumentation experienced an increased incidence of inadequate pain relief from LEA. Individualized anaesthetic management plans were executed for parturients with spina bifida occulta, neurological, cardiac, and haematological disease as well as for women with a history of adverse drug reactions and previous problems with regional or general anaesthesia. It is concluded that the OAC has provided a valuable service to obstetricians and anaesthetists for the anaesthetic management of pregnant women with co-existing disease. The OAC gave an opportunity for patient education regarding anaesthetic options for labour and delivery. The attending anaesthetist was provided with a risk assessment and anaesthetic management plan which was adhered to with only two exceptions. Finally, the obstetrician was given consistent dvice regarding anaesthesia management that may affect obstetrical decisions.     

Duration of action of an equipotent dose of vecuronium in infants and in children

During general anaesthesia without any volatile anaesthetic agents, ten infants and ten children received incremental doses of vecuronium to achieve a 95% neuromuscular block. Thereafter, the thenar electromyographic response was allowed to recover spontaneously. Total dose of vecuronium to establish a 95.0 ± 0.5% (mean ± SEM) neuromuscular block was 66% greater for children than for infants (73 ± 4 vs. 44 ± 4 μg·kg^?1, P < 0.0001). However, recovery index and time to complete recovery of the neuromuscular function were 88 and 89% longer, respectively, in infants than in children (P < 0.0001). These results of the effect of an equipotent dose of vecuronium in infants and in children confirm that vecuronium is a long acting neuromuscular blocking agent in infants.