Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content ++ KEY FEATURES ++ ESSENTIALS OF DIAGNOSIS ++ Cardiac arrhythmias or dysfunction with any of the following: – Hyponatremia – Hypokalemia – Hyperkalemia – Hypocalcemia – Hypophosphatemia – Hypomagnesemia ++ GENERAL CONSIDERATIONS ++ Hyponatremia is common in advanced heart failure; diuretics may play a role Hypokalemia is also common with use of diuretics and increases the risk of ventricular arrhythmia – Extreme hypokalemia may lead to cardiac arrest Hyperkalemia can cause asystole Hypocalcemia prolongs QT interval and facilitates ventricular arrhythmias Hypocalcemia and hypophosphatemia, when prolonged, may cause cardiomyopathy Hypomagnesemia may cause: – Refractory hypokalemia and hypocalcemia – Ventricular arrhythmias ++ CLINICAL PRESENTATION ++ SYMPTOMS AND SIGNS ++ Syncope Heart failure symptoms Palpitation Weakness Seizures ++ PHYSICAL EXAM FINDINGS ++ Hypotension Signs of heart failure Edema Tetany with hypocalcemia Proximal muscle weakness with hypokalemia ++ DIFFERENTIAL DIAGNOSIS ++ Hypokalemia and hypomagnesemia may be caused by diuretics or gastrointestinal losses Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and spironolactone may cause hyperkalemia ++ DIAGNOSTIC EVALUATION ++ LABORATORY TESTS ++ Serum electrolytes, calcium, magnesium, phosphorus ++ ELECTROCARDIOGRAPHY ++ Nonspecific ST-T–wave changes are common Hypokalemia causes prominent U waves Hyperkalemia causes absent P waves, peaked T waves, and eventually widened QRS, culminating in a sine-wave ventricular tachycardia or asystole QTc may be prolonged in hypokalemia, hypocalcemia, or hypomagnesemia QTc shortened by hypercalcemia A prolonged QTc facilitates polymorphic ventricular tachycardia ++ IMAGING STUDIES ++ Electrocardiography: may show generalized left ventricular hypokinesis with low ejection fraction ++ TREATMENT ++ CARDIOLOGY REFERRAL ++ Significant cardiac arrhythmias Heart failure Cardiac arrest ++ HOSPITALIZATION CRITERIA ++ Significant arrhythmias Heart failure Cardiac arrest Syncope Seizures ++ MEDICATIONS ++ Identify and treat the underlying cause For hypokalemia and hypomagnesemia, provide IV or oral replacement Severe hyperkalemia is a cardiac emergency – IV calcium chloride or gluconate for cardioprotection – IV insulin/glucose and/or bicarbonate to shift the potassium into the cell – Diuretic to lower body potassium subacutely – Renal dialysis if necessary IV calcium for acute correction of low calcium and to correct hypomagnesemia High calcium: – Can be lowered by ambulation and fluids in mild cases – Can be lowered by bisphosphonates in more severe elevations Hyponatremia is treated with fluid restriction and correction of the circulatory problem In severe cases tolvaptan can be given and, rarely, hypertonic saline ++ MONITORING ++ Close monitoring of metabolic abnormalities during treatment ++ DIET AND ACTIVITY ++ In general, dietary restriction or liberalization is useful, depending on the abnormality, except liberalizing sodium if hyponatremia is due to heart failure ++ ONGOING MANAGEMENT +... GET ACCESS TO THIS RESOURCE Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth Get Free Access Through Your Institution Contact your institution's library to ask if they subscribe to McGraw-Hill Medical Products. What is MyAccess? Create a FREE MyAccess profile to: Use this site remotely Bookmark your favorite content Track your self-assessment progress and more! GET ACCESS TO THIS RESOURCE Subscription Options Pay Per View Timed Access to all of AccessCardiology 24 Hour $34.95 (USD) Buy Now 48 Hour $54.95 (USD) Buy Now Best Value AccessCardiology Full Site: One-Year Individual Subscription $595 USD Buy Now View All Subscription Options