Hypokalemia, High Erythrocyte Na⁺ and Low Erythrocyte NaK-ATPase in Relatives of Patients Dying from Sudden Unexplained Death Syndrome in North-East Thailand and in Survivors from Near-Fatal Attacks

Abstract

The sudden unexplained death syndrome (SUDS) is a sudden death of unknown cause in healthy South-East Asians. In Thailand, it is common in the North-East region. We previously reported high incidences of low erythrocyte sodium and potassium-activated adenosine triphosphatase (NaK-ATPase) activity and of high erythrocyte sodium in North-East Thais and speculated that this metabolic defect might be associated with the high incidence of SUDS in that region. In this communication, we studied plasma sodium and potassium, erythrocyte sodium and potassium, activities of erythrocyte NaK-ATPase, ouabain-insensitive ATPase and total ATPase in healthy Thai blood donors from Central Thailand (group 1), healthy North-East city dwellers (group 2), relatives of SUDS victims (group 3) and survivors from SUDS-like attacks (group 4). Compared with groups 1 and 2, group 3 and 4 subjects had significantly lower plasma potassium (p < 0.0001), higher erythrocyte sodium (p < 0.0001), lower activities of erythrocyte NaK-ATPase (p < 0.0001) and of erythrocyte total ATPase (p < 0.0001). In addition, group 4 subjects had lower plasma potassium, higher erythrocyte sodium and lower activity of total ATPase than those of group 3. The findings suggest that the pathogenesis of SUDS could be related to hypokalemia and a membrane sodium/potassium pump defect.

Differences in serum potassium concentrations between Chinese, Indians and Malays

“…The victims are in apparently good health and usually die at night while sleeping. His group have documented low erythrocyte sodium-potassium ATPase in relatives of patients dying from SUDS and suggested that the pathogenesis of SUDS could be related to hypokalaemia and possibly an acquired membrane sodium-potassium pump defect (12,13). Patients who have been resuscitated were found to have ventricular fibrillation and inducible polymorphic ventricular tachycardia in the electrophysiologic laboratory.…”

Potassium depletion in a healthy north‐eastern Thai population: No association with tubulo‐interstitial injury

“…Based on the previous hypothesis that north‐east Thais might have a lower body potassium store than Thais who lived centrally, 1–3 we studied the tissue potassium contents of the north‐eastern and central Thais who died from a vehicular accident. This gave us an opportunity to compare the potassium content of various tissues from both population groups.…”

“…31 Tosukhowong et al and Tungsanga et al found that north-eastern Thais who had survived from a sudden unexplained death syndrome (SUDS)-like syncopal attack had lower serum potassium, urinary potassium and citrate, higher erythrocyte sodium but lower erythrocyte Na, K-ATPase activity than controls. 2,12 Hypokalaemia is also consistently found in hypokalaemic periodic muscle paralysis, a common problem in north-eastern Thais. 4 In hypokalaemic nephropathy, the renal tubular production of ammonia is increased.…”

“…In north‐east Thais with upper urinary tract stone disease, hypokalaemia and the low urinary excretion of potassium are frequently observed, and they can be corrected by the use of potassium supplementation. In subjects who have survived syncopal attacks similar to fatal attacks of sudden unexplained death syndrome (SUDS), hypokalaemia was observed in 50% of cases 2 . Hypokalemia is a consistent finding in distal renal tubular acidosis (dRTA) and hypokalaemic periodic paralysis 3,4 .…”

“…In subjects who have survived syncopal attacks similar to fatal attacks of sudden unexplained death syndrome (SUDS), hypokalaemia was observed in 50% of cases. 2 Hypokalemia is a consistent finding in distal renal tubular acidosis (dRTA) and hypokalaemic periodic paralysis. 3,4 The data suggests that north-eastern Thais might have pre-existing potassium deficiency.…”