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Hypokalemic Arrest
Eric Lavonas, MD, FACEP
Carolinas Medical Center
Charlotte, NC
Patient presents with…
H/O schizophrenia Acute-on-chronic overdose 100 pills of a single medication Time of ingestion: ~45 min PTA No symptoms
Vital Signs
P 70 R 16 BP 120/80 T 36.1C
0102030405060708090
100
Per
cen
t o
f P
atie
nts
8 10 12 14 16 18 20 22 24
Resipratory Rate
Vital Signs at Triage
Now the Fun Begins
Sudden cardiac arrest Wide complex tachydysrhythmia No pulse Unknown if Torsades de Pointes
Rapid defibrillation & intubation P 60 BP 70/50
Pre-Arrest Post-Arrest
200 msec 240 msec
Laboratory Abnormalities
Profound hypokalemia Mild metabolic acidosis
Respiratory alkalosis from vent Other minor abnormalities
Creatinine 1.2 mg/dl Glucose 178 mg/dl
Post-Arrest Therapy
Dopamine Poor response
Norepinephrine BP improved
4 gm MgSO4
Potassium, potassium, potassium 300 ml (154 mEq) hypertonic NaCl
Effect of Hypertonic Saline
After
Before
200
80
QT Prolongation
QT = .640s; QTc = .500
QT.440; QTc.469
Before
After
Inpatient Course
Potassium still low Aggressive replacement over 11 hours
Weaned off pressors Did well
Key Elements
Wide QRS Prolonged QTc Relative bradycardia Hypokalemia
Key Elements
Wide QRS Prolonged QTc Relative bradycardia Hypokalemia
Anti-Dysrhythmics
Class I: Block Na entry Ia: Block Na in and K out Ib: Block Na in Ic: Block Na in, Ca in, and K out
Class II: β receptor antagonists Class III: Block K out Class IV: L-type Ca channel antagonists
Vaughn-Williams EM and Singh BN, Cardiovasc Res 6:109 (1972)
Na in K out
Ca in, K out
Na channel blockade
Sodium Channel States
Resting (Closed) Open Inactivated (Closed)
Refractory
Sodium Channel States
Frequency-Dependent Block
Weirich J, Antoni H, J Cardiovasc Pharmacol 15:998-1009 (1990)
Class Ia: τrecovery 1-10 sec
Class Ib: τrecovery < 1 sec
Class Ic: τrecovery > 10 sec
Key Elements
Wide QRS Prolonged QTc Relative bradycardia Hypokalemia
QT Prolongation
QT = .640s; QTc = .500
Na in K out
Ca in, K out
K efflux blockade
Key Elements
Wide QRS Prolonged QTc Relative bradycardia Hypokalemia
Relative Bradycardia
β-receptor antagonists Calcium channel antagonists Digitalis and related glycosides Central α-2 agonists Cholinesterase inhibitors Mitochondrial toxins (e.g. CN) Sedative-hypnotics End-stages of cocaine, TCA’s, etc.
Key Elements
Wide QRS Prolonged QTc Relative bradycardia Hypokalemia
Hypokalemia
Increased urinary losses Most diuretics Renal toxins (toluene, aminoglycosides) Licorice
Extra-renal losses (diarrhea) Exchange with another cation
Sodium polystyrene sulfate (Kayexalate™) Sodium penicillins
Hypokalemia
Intracellular sequestration Enhanced entry
Catecholamines Insulin/glucose Barium salts Thyrotoxicosis
Hypokalemia
Intracellular sequestration Blocked release from IK channels
“Pure”: Dofetilide, Ibutilide
Hypokalemia
Intracellular sequestration Blocked release from IK channels
“Pure”: Dofetilide, Ibutilide “Less selective”: Disopyramide, flecainide,
procainamide, quinidine
Hypokalemia
Intracellular sequestration Blocked release from IK channels
“Pure”: Dofetilide, Ibutilide “Less selective”: Disopyramide, flecainide,
procainamide, quinidine
Hypokalemia
Intracellular sequestration Blocked release from IK channels
“Pure”: Dofetilide, Ibutilide “Less selective”: Disopyramide, flecainide,
procainamide, quinidine Amiodarone, bretylium,
propafenone, sotalol
Key Elements
Wide QRS Prolonged QTc Relative bradycardia Hypokalemia
The Sicilian Gambit
Task Force of the Working Group on Arrhythmias of the European Society of Cardiology. The Sicilian gambit. A new approach to the classification of antiarrhythmic drugs based on their actions on arrhythmogenic mechanisms. Circulation 1991;84:1831-51.
Hints & Clues
Pill form Medication
Prescription? Herbal? Available in bottle of 100
Cardiac arrest precedes AMS Recovery in 26 hours
Closing in…
QuinineQuinidineDisopyramideChloroquineAntipsychoticsAmiodaroneProcainamideSotalol
Closing in…
QuinineQuinidineDisopyramideChloroquineAntipsychoticsAmiodaroneProcainamideSotalol
GI EffectsTachycardiaTachycardia
Tachycardia, sedationOnset delayedOnset delayedNo Na Ch block; no hypoK
Chloroquine
Na channel blockade Present at low heart rate
K efflux blockade QT prolongation Profound hypokalemia
Relative bradycardia Hypotension
Drug Information
Chloroquine
Trade Name Aralen™
Common Use Malaria
Dose 500 mg PO Q week
Half-life Days-weeks
Patient presents with…
H/O schizophrenia Acute-on-chronic overdose 100 pills of a single medication Time of ingestion: ~45 min PTA No symptoms
Drug Information
Chloroquine Hydroxychloroquine
Trade name Aralen™ Plaquenil™
Common use Malaria Autoimmune disease
Dose 500 mg POQ week
200 mg PO1-2 daily-BID
Half life Days-weeks 15-31 hours
Hydroxychloroquine Overdose
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