Hyperkalemia Flashcards
ECG
What is the clinical definition of hyperkalemia?
Serum potassium levels greater than 5 mEq/L
What increases the risk of hyperkalemia?
Renal:
- Acute or Chronic kidney disease
- decreased effective circulating volume (ECV) causing low distal solute delivery
- decreased aldosterone from RTA type 4 (hyporeninemic-hypoaldosteronism)
- decreased aldosterone from Addisons disease
- decreased aldosterone from ACEi or ARB use
- resistance to aldosterone from K-sparing diuretics
Rhabdomyolysis
Insulin deficiency
Beta-Blockers
Metabolic or respiratory acidosis (swapping K for H on albumin)
Tumor lysis syndrome
A patient receiving chemotherapy can develop hyperkalemia due to …. ?
Tumor lysis syndrome.
A 62-year-old man with recently diagnosed diffuse large B-cell lymphoma is admitted to the hospital for chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab (R-CHOP). Medical history also includes hypertension, type 2 diabetes mellitus, coronary artery disease, and heart failure with reduced ejection fraction. Pretreatment evaluation shows normal renal function, liver function, and uric acid levels. Echocardiography reveals a left ventricular ejection fraction of 45%. Intravenous fluids and allopurinol are administered prior to chemotherapy. After receiving chemotherapy, the patient experiences mild nausea that resolves with antiemetics. The next morning, he reports dyspnea and lightheadedness and becomes unresponsive with a loss of pulse while being evaluated. Electrocardiographic monitoring just prior to cardiac arrest is shown in the exhibit. Which of the following most likely directly contributed to this patient’s cardiac arrest?
This patient with diffuse large B-cell lymphoma likely developed cardiac arrest the day after administration of chemotherapy/immunotherapy medications. These medications lyse tumor cells, thereby releasing intracellular potassium, phosphate, and nucleic acids (metabolized to uric acid) into the circulation. When large amounts of these substances are released at a rate that exceeds their renal elimination, this process is termed tumor lysis syndrome (TLS).
TLS is a complication of chemotherapy/immunotherapy that typically develops in patients who have tumors with high cell burden (eg, widespread bulky lymphadenopathy) or rapid turnover, as well as those who are receiving combination therapy. Early TLS symptoms are nonspecific (eg, nausea, as in this patient) and can mimic symptoms caused by chemotherapy. Severe manifestations of TLS include, Acute kidney injury due to renal precipitation of uric acid and calcium-phosphate crystals, Seizures due to neuronal hyperexcitability caused by hypocalcemia (ie, calcium-phosphate formation), and Cardiac arrhythmias due to hyperkalemia and myocardial calcium-phosphate deposition. This patient’s ECG shows a widened QRS interval (eg, sine wave pattern) consistent with severe hyperkalemia, which is the most likely precipitant of his cardiac arrest (ie, progression to ventricular asystole and loss of pulse). Although pretreatment with intravenous fluids and uric acid level reduction (eg, allopurinol) lowers the risk of developing TLS, it may still occur despite these measures.
What is the progression of T-wave morphology seen in hyperkalemia?
1) Peaked T-waves
2) Loss of P-wave and ST-depression
3) Widened QRS
4) Asystole
What is the potassium level range associated with peaked T waves on an ECG?
5.5–6.5 mmol/L
What ECG changes occur at a potassium level of 5.5–6.5 mmol/L?
Peaked T waves (due to repolarization abnormalities).
What potassium level is associated with progressive atrial paralysis on ECG?
6.5–7.0 mmol/L
What ECG changes occur at potassium levels of 6.5–7.0 mmol/L?
P wave widening and flattening
Progressive atrial paralysis = gradual disappearance of P waves
Increased QRS duration
PR prolongation
eventual disappearance of P waves.
At what potassium level does muscle weakness, conduction abnormalities and bradyarrhythmias appear?
7.0–9.0 mmol/L
What are the key ECG changes associated with potassium levels of 7.0–9.0 mmol/L?
Bradyarrhythmias (sinus bradycardia, AV block, slow junctional/ventricular escape rhythms), conduction blocks, prolonged QRS interval with bizarre QRS morphology.
What potassium level is associated with pre-terminal ECG findings, such as a sine wave appearance?
Greater than 9.0 mmol/L
What ECG findings are seen at potassium levels above 9.0 mmol/L?
Sine wave appearance, asystole, ventricular fibrillation, and PEA with bizarre, wide-complex rhythms.
What is the first step in managing hyperkalemia?
IV Calcium Gluconate
IV Insulin with D5W
What are the second-line medications for hyperkalemia?
Beta-agonist (albuterol)
Sodium Bicarbonate
What must be done to definitively treat hyperkalemia?
Dialysis
- can give diuretics if the renal function is good *
- K-binding resins has been shown to cause GI necrosis *
