Year : 2012 | Volume
: 15 | Issue : 4 | Page : 302--304
Management of a patient with hyperkalemic periodic paralysis requiring coronary artery bypass grafts
Sanjay Orathi Patangi, Mathew Garner, Hazel Powell
Department of Cardiothoracic Anaesthesia and Intensive Care, Freeman Hospital, Newcastle Upon Tyne, United Kingdom
Sanjay Orathi Patangi
Department of Cardiothoracic Anaesthesia and Intensive Care, Freeman Hospital, Newcastle Upon Tyne NE7 7DN
Hyperkalemic periodic paralysis (HPP) is an autosomal-dominant inherited muscle disease characterized by episodes of flaccid weakness and intermittent myotonia. There are no previous reports in the literature about anesthesia for cardiac surgery with cardiopulmonary bypass in this disorder. We describe perioperative anesthetic management for on-pump coronary artery bypass grafting in a 75-year-old man with a history of hyperkalemic periodic paralysis. This case report outlines our management strategy and the issues encountered during the perioperative period.
|How to cite this article:|
Patangi SO, Garner M, Powell H. Management of a patient with hyperkalemic periodic paralysis requiring coronary artery bypass grafts.Ann Card Anaesth 2012;15:302-304
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Patangi SO, Garner M, Powell H. Management of a patient with hyperkalemic periodic paralysis requiring coronary artery bypass grafts. Ann Card Anaesth [serial online] 2012 [cited 2022 May 21 ];15:302-304
Available from: https://www.annals.in/text.asp?2012/15/4/302/101867
There are two principal types of familial periodic paralysis, hyperkalemic periodic paralysis (HPP) and hypokalemic periodic paralysis. They are both autosomal-dominant inherited muscle diseases. The hyperkalemic form (HPP) is characterized by episodes of flaccid weakness and intermittent myotonia. The HPP is caused by mutation of the skeletal muscle sodium channel gene SCN4A on chromosome 17q23. Twenty different mutation points have been identified, and these single amino acid changes cause alterations in the parts of the sodium channel that control inactivation, leading to spontaneous depolarisation and subsequent myotonia. , There is no evidence of an association between HPP and malignant hyperpyrexia.  Myotonia may be precipitated by prolonged fasting  and hypothermia,  and paralysis has been described postoperatively following anesthesia. There have been no reported problems with the use of neuromuscular blockade in HPP, , although these may precipitate paralysis in the hypokalemic variant.  There are reports of cardiac anesthesia in patients with hypokalemic periodic paralysis  in the literature, but we could find no reports of anesthesia for cardiac surgery in patients with HPP.
We present our experience of managing a 75-year-old man with a long-standing history of angina and HPP who required coronary artery bypass grafting (CABG). Coronary angiography showed significant disease of the left main stem, left anterior descending and circumflex arteries. The myocardial perfusion scan demonstrated a reversible antero-apical perfusion defect and trans-thoracic echocardiography revealed an ejection fraction of 44%. Significant past medical history included hypertension and hyperlipidemia. The HPP had been diagnosed when the patient was in his 30s. He was prescribed bendrofluazide at that time but stopped taking it after a few years. He had previously been aware of episodes of weakness affecting his lower limbs, particularly when he was given potassium supplementation while serving in the armed forces. The patient's preoperative medication included aspirin, perindopril, diltiazem and isosorbide mononitrate. A 5% dextrose infusion was commenced on the eve of surgery and bendrofluazide in a dose of 5 mg was recommenced. Temazepam premedication was given 90 min before transfer to the operating room (OR).
The OR was warmed to 24 o C before the patient arrived. In the anesthetic room, peripheral venous and radial arterial cannulae were inserted under local anesthesia and the intravenous infusion was changed to dextrose saline. Flucloxacillin was administered as per our antibiotic protocol. General anesthesia was induced with midazolam, etomidate and fentanyl, and maintained with isoflurane and further incremental doses of fentanyl to a total of 1 mg. Atracurium bolus followed by its infusion was used for neuromuscular blockade. Following induction of anesthesia and endotracheal intubation, a nasopharyngeal temperature probe was inserted and central venous catheter was placed in the right internal jugular vein. Before commencement of surgery, a forced air heating blanket was placed over the abdomen and arms to help maintain patient temperature. Cardiac surgery proceeded in a routine fashion with sternotomy and harvesting of the left internal mammary artery and long saphenous vein for use as conduits. A further sterile forced air heating blanket was placed over the lower limbs following vein harvest to help maintain the body temperature following cardiopulmonary bypass (CPB). Heparin (3 mg/kg) was administered prior to commencement of CPB. The CPB circuit was primed with 1400 mL 5% albumin solution and 5000 IU heparin. While on CPB, the patient's temperature was maintained at 36 o C and his mean arterial pressure was maintained at greater than 60 mmHg. Our aim was to keep a serum potassium level of 4-4.5 mmolL -1 to minimize the risk of postoperative arrhythmia, although we were aware that this might trigger the periodic paralysis. The CPB circuit incorporated an oxygenator with in-line arterial blood gas, electrolyte, hematocrit and venous saturation monitoring. The in-line monitoring was invaluable in monitoring the potassium level during the case. No cardioplegia administration circuit was required as a cross-clamp fibrillation technique was used.
On initiation of CPB, the serum potassium level unexpectedly rose to 6.9 mmolL -1 necessitating insulin and glucose administration. Although we initially planned to monitor blood glucose levels every 20 min, this was increased to checks every 10 min to maintain an optimum blood glucose level. Fifty percent dextrose supplementation was needed on two occasions during CPB to maintain an adequate blood glucose level. One dose of potassium supplementation (20 meq) was required during the bypass period to maintain our target level of 4-4.5 mmolL -1 . Acid-base levels remained normal throughout. No further heparin was required during CPB. The total CPB time was 89 min and total cross-clamp time was 47 min, incorporating three periods of 19, 15 and 13 min. Protamine was used to reverse the action of heparin after termination of CPB. Following completion of surgery, the atracurium infusion was discontinued. Propofol and morphine infusions were commenced and the patient was transferred to the intensive care unit for standard postoperative monitoring and ventilatory support. After 2 h, the sedation was stopped and he was extubated uneventfully.
Approximately 14 h following completion of surgery and 12 h post extubation, the patient complained of weakness in his arms and legs. His serum potassium was 3.8 mmolL -1 and he was normothermic. On examination, there was reduced grip strength and inability to move his limbs against gravity, but no respiratory compromise. This resolved spontaneously after 1 h. There was no obvious explanation for this clinical finding. Until this point, the patient had been receiving potassium supplementation (40 meq/L) in his maintenance fluid (dextrose saline 1 mL/kg/h). Although the added potassium was removed, the serum potassium continued to rise and peaked at 5.2 mmolL -1 150 min after the beginning of the episode of limb weakness. The patient's symptoms had resolved by this time; therefore, the elevated serum potassium result was not treated, and it then gradually fell without intervention. There were no such further episodes of weakness during the patient's hospital stay. He was discharged from intensive care to the surgical ward on the first postoperative day, and subsequently discharged home 6 days after the procedure.
Familial periodic paralyses, hyperkalemic and hypokalemic, are a rare group of inherited autosomal-dominant muscle disorders caused by mutations in genes that regulate sodium and calcium channels. Often beginning in infancy or early childhood, attacks of hyperkalemic paralysis are characterized by sudden elevation of potassium blood concentration that are precipitated by exercise, hypothermia and fasting. Between attacks, the affected muscles function normally. As there are no published guidelines for the anesthetic management of such cases undergoing cardiac surgery, we propose a few guidelines that could enable successful management of these cases. Avoidance of a prolonged fasting period preoperatively and hydration with 5% dextrose (2 mL/kg) to cover fasting requirements should be considered. Perioperative use of potent diuretics could precipitate unwanted hypokalaemia in this group of patients and should therefore be used with caution. Emergency drugs that should be readily accessible include calcium chloride, dextrose 50% and actrapid insulin. Avoidance of drugs that cause hyperkalemia is prudent. In cases of difficult airway, use of rocuronium or awake fiberoptic intubation should be considered. Neuromuscular junction monitoring could be considered in these cases, but is mandatory when dealing with the hypokalemic variant. Close monitoring of the patient's acid-base balance, potassium levels and multi-lead ECG should be maintained peri- and postoperatively. An in-line electrolyte and blood gas monitoring system during bypass is recommended. Maintenance of normothermia by optimizing ambient room temperature, warming of intravenous fluids and use of warming blankets are important. If blood transfusion is required, fresh whole blood is recommended. Muscle tone monitoring should be performed postoperatively to look for any significant weakness.
To summarize, this case report describes the molecular and genetic basis of HPP and our approach and guidelines for anesthetising a patient with this condition requiring CABG using CPB.
The authors would like to thank Mr. Leslie Hamilton, Consultant Cardiac Surgeon, for allowing to report this case and acknowledge the help of Mr. Jason Robson who was the perfusionist involved in the management of this case.
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