Hypokalemic familial periodic paralysis

Diverse phenotype of hypokalaemic periodic paralysis within a family

Hypokalaemic periodic paralysis typically presents with intermittent mild-to-moderate weakness lasting hours to days. We report a case with an uncommon phenotype of late-onset myopathy without episodic paralytic attacks. Initial work-up including muscle biopsy was inconclusive. A subsequent review of the right deltoid biopsy, long exercise testing and repeated family history was helpful, followed by appropriate genetic testing. We identified a heterozygous pathogenic mutation in calcium ion channel (CACNA1S:c.1583G>A p.Arg528His) causing hypokalaemic periodic paralysis. Myopathy can present without episodic paralysis and the frequency of paralytic episodes does not correlate well with the development and progression of a fixed myopathy. Our report also highlights the intrafamilial phenotypic variation of hypokalaemic periodic paralysis secondary to a CACNA1S gene mutation.

Pathophysiologic and anesthetic considerations for patients with myotonia congenita or periodic paralyses

Myotonia congenita and periodic paralyses are hereditary skeletal muscle channelopathies. In these disorders, various channel defects in the sarcolemma lead to a severely disturbed membrane excitability of the affected skeletal muscles. The clinical picture can range from severe myotonic reactions (e.g., masseter spasm, opisthotonus) to attacks of weakness and paralysis. Provided here is a short overview of the pathomechanisms behind such wide-ranging phenotypic presentations in these patients, followed by recommendations concerning the management of anesthesia in such populations.

Hypokalemic periodic paralysis

Hypokalemic periodic paralysis is a rare genetic disorder characterized by recurrent attacks of skeletal muscle weakness with associated hypokalemia which is precipitated by stress, cold, carbohydrate load, infection, glucose infusion, hypothermia, metabolic alkalosis, anesthesia, and steroids. We encountered one such incidence of prolonged recovery after general anesthesia, which on further evaluation revealed a case of hypokalemic paralysis. The key to successful management of such a patient was vigilant pre-operative evaluation, perioperative monitoring, and aggressive treatment of hypokalemia when it occurs.

Severe prognosis in a large family with hypokalemic periodic paralysis

Hypokalemic periodic paralysis (HypoPP) is a channel disorder caused primarily by mutations in the human skeletal muscle alpha1 subunit (CACNA1S) of the dihydropyridine-sensitive calcium channel. Molecular, clinical, and biochemical studies were aimed at establishing genotype/phenotype correlations in a large Italian family affected by a severe form of HypoPP. Whereas patients with HypoPP usually show a normal life span, in this family three male patients died young, one of them from anesthetic complications resembling malignant hyperthermia. Our patients carried the c1583G>A genetic lesion (R528H), which has been associated with a mild phenotype and with incomplete penetrance in women. Surprisingly, the R528H amino acid substitution in the family presented here correlated with an unfavorable prognosis in both male and female patients. We conclude that genetic characterization is an important requirement to alert physicians about the management of similar patients, especially when anesthesia is considered.

Total intravenous anaesthesia in a patient with familial hypokalaemic periodic paralysis

A 35-year-old woman with known familial hypokalaemic periodic paralysis received general anaesthesia for reduction of bilateral breast hyperplasia. Uncomplicated general anaesthesia was performed using a propofol target-controlled infusion, remifentanil infusion and bolus doses of mivacurium with neuromuscular function monitoring. Plasma potassium concentrations were controlled intermittently in the peri-operative period and supplemented to achieve normokalaemia. Despite continuous substitution, an episode of low plasma potassium concentration occurred during the recovery period; this was without any clinical signs of muscle paralysis or respiratory distress.

Familial hypokalemic periodic paralysis and Wolff-Parkinson-White syndrome in pregnancy

PURPOSE

To describe the anesthetic and obstetrical management of a pregnant patient with co-existing Familial Hypokalemic Periodic Paralysis (FHPP) and Wolff-Parkinson-White syndrome (WPW).

CLINICAL FEATURES

A 29 yr-old primigravida with FHPP and WPW presented to the antenatal clinic at 18 wk gestation, for consideration of her anesthetic and obstetrical management during labour and delivery. A plan was constructed to avoid the known precipitating factors of FHPP including carbohydrate loading, cold, mental stress and exercise, which could lead to acute attacks of weakness. She presented for induction of labour at 41 wk and three days. An epidural catheter was sited early in labour. The second stage was limited to less than one hour. She had a rotational forceps delivery for which the epidural was extended to provide anesthesia. A healthy male baby was delivered. The patient made an uncomplicated recovery and was discharged home on the second postnatal day. The peripartum potassium was kept within the normal range with intravenous as well as oral potassium supplementation. No arrhythmias were reported.

CONCLUSION

Assessment of the patient at an early stage in her pregnancy allowed for a multidisciplinary approach to this patient and her medical problems. A plan was made to avoid known precipitating factors during labour, delivery and the postnatal period well in advance of her date of confinement, leading to a successful outcome for mother and child.

Anaesthetic management of a patient with familial normokalaemic periodic paralysis

PURPOSE

We describe the anaesthetic management of a patient with the autosomal dominant inherited disease, normokalaemic periodic paralysis. The disease results in intermittent bouts of limb and respiratory muscular weakness in association with hypothermia, stress, prolonged fasting or exercise. Unlike hypokalaemic and hyperkalaemic periodic paralysis, the more common variants of the disease, normokalaemic periodic paralysis is not accompanied by alterations in the plasma potassium concentration.

CLINICAL FEATURES

A five-year-old boy presented for emergency scrotal exploration. He had a family history of periodic paralysis and had experienced previous episodes of weakness, two of which had required hospitalization for respiratory distress. On admission there was no evidence of weakness and serum potassium concentration was 4.2 mMol.L-1. A spinal anaesthetic was performed and the procedure was uncomplicated by muscle paralysis above the level of the spinal block.

CONCLUSION

Avoidance of known precipitating factors and judicious use of neuromuscular blocking drugs has been advocated in patients with this disorder presenting for surgery. In appropriate circumstances, spinal anaesthesia represents a useful option in patients with normokalaemic periodic paralysis.

Hypokalaemic episodic polymyopathy in cats fed a vegetarian diet

A previously undocumented hypokalaemic condition with a cyclical nature, comprising acute bouts of polymyopathy followed by spontaneous recoveries, is described in the cat. Cats being fed a high protein vegetarian diet developed recurrent episodes of polymyopathy, characterised by ventroflexion of the head and neck, stiff forelimb gait, lateral head-resting and generalised muscle weakness. Plasma potassium concentrations (mean +/- standard deviation) were reduced from 3.28 +/- 0.33 mmol/l at the beginning of the experiment to 2.45 +/- 0.24 mmol/l during bouts of myopathy. This hypokalaemia was associated with increased creatine kinase activities indicative of muscle damage, and decreased urinary potassium concentrations, and was caused by insufficient dietary potassium. Cats that received the same diet supplemented with potassium did not develop hypokalaemic polymyopathy. Spontaneous recoveries of affected cats were not associated consistently with increases in plasma potassium concentrations. Plasma taurine concentrations decreased and glutamic acid increased markedly in all cats fed the experimental diet. There was no evidence of thiamin deficiency associated with the high glutamic acid intake. Veterinarians should be aware that hypokalaemic cats, and in particular those on potassium-deficient diets, may show cyclical disease with episodes of polymyopathy recurring after periods of spontaneous clinical recovery. This condition in cats may be a useful animal model for familial hypokalaemic periodic paralysis in humans.

Atracurium use in a patient with familial periodic paralysis

We describe a patient with the hypokalemic type of familial periodic paralysis (FPP) who received atracurium for muscle relaxation as required for diagnostic laparoscopy. Electrocardiographic (EKG) T-wave changes suggestive of hypokalemia were not supported by blood determinations. Arterial blood measurements of potassium (K+), pH, and arterial carbon dioxide tension (PaCO2) and the patient's esophageal temperature were maintained within normal limits. The degree of muscle relaxation was closely monitored by a peripheral nerve stimulator and train-of-four (TOF) measurement of muscle twitch height. At the conclusion of the surgical procedure, no reversal to the muscle relaxant was needed or given. The patient regained preoperative muscle strength, and her postoperative course was uneventful.

Hypokalemic periodic paralysis

Generalized motor weakness is a common complaint in the emergency department and has a wide differential diagnosis that includes both organic and infectious etiologies. We report the case of a previously healthy young man with symptoms of muscular paralysis and associated hypokalemia. The clinical presentation of hypokalemic periodic paralysis, its differential diagnosis, and pertinent physical findings are discussed.

Familial "hashitoxic' periodic paralysis

Four members of a Chinese family who had thyrotoxicosis and periodic paralysis are described. Two of these patients had "hashitoxicosis' (Graves' disease and Hashimoto's thyroiditis) as evidenced by the presence of thyroid antibodies in addition to elevated thyroxine (T4) levels. The other two patients were not available for testing. The association of the familial occurrence of "hashitoxicosis' and periodic paralysis does not appear to have been reported previously.