Cardiac Glycoside Plant Poisoning Workup

The workup may include the following tests and studies:

• Pulse oximetry - To monitor oxygen saturation and heart rate

• Electrocardiogram (ECG) and continuous cardiac monitoring

• Fingerstick glucose determination - To assess for hypoglycemia as a possible cause of altered mental status

• Complete blood count (CBC) - To determine whether anemia is a cause or potential complicating factor of dysrhythmia or hypotension

• Electrolyte levels

• Blood urea nitrogen (BUN) and creatinine

• Cardiac glycoside level

• Chest radiography - May be indicated for patients with severely toxic reactions or patients with pulmonary findings on physical examination

• Pregnancy test - Consider for women with intentional ingestions or suicidal ideation

Depending on the patient’s presentation, other tests to consider may include the following:

• Cardiac enzymes

• Thyroid function tests (TFTs)

• Arterial blood gases (ABGs)

• Urine drug screens

• Acetaminophen (APAP) level

• Salicylate (ASA) level

• Ethanol (ETOH) level

The ECG is performed to assess the cardiac rhythm and look for signs of ischemia or infarction. Nonspecific ST segment and T wave abnormalities, consistent with "dig effect," (eg, ST "scooping" or "strain"-like pattern) may be noted. This does not signify toxicity; merely the presence of cardiac glycoside. Peaked T waves may occur in hyperkalemia.

Renal function tests are performed because renal impairment negatively impairs elimination of glycosides and may exacerbate hyperkalemia. In addition, renal insufficiency is associated with elevated endogenous digoxinlike immunoreactive factors that can give false-positive digoxin assay results.

Hyperkalemia is a primary manifestation of acute cardiac glycoside toxicity and an early predictor of need for antidotal therapy. Hypokalemia exacerbates cardiac glycoside toxicity, and it is more typical in chronic toxicity. It is usually secondary to the use of loop diuretics, poor dietary intake, diarrhea, and administration of potassium-binding resins.

Hypercalcemia and hypomagnesemia exacerbate cardiac glycoside toxicity. Magnesium and ionized calcium levels may be helpful, but serum magnesium levels do not reflect total body load of magnesium.

Some plant glycosides cross-react with commonly used digoxin radioimmunoassays (RIAs) and digoxin fluorescence polarization immunoassays. Detectable levels of cardiac glycosides have been associated with ingestion of foxglove and oleander; however, levels do not correlate with severity of illness. A negative digoxin RIA does not rule out a plant glycoside exposure.

The following medical conditions are associated with elevated endogenous digoxinlike immunoreactive factors that can give false-positive digoxin assay results:

• Renal insufficiency

• Pregnancy

• Liver disease

• Subarachnoid hemorrhage

• Heart failure

• Type 1 diabetes mellitus

• Stress

• Hypothermia