From the Guidelines
Early ECG changes in non-bilious vomiting due to gastric outlet obstruction primarily reflect electrolyte disturbances, especially hypokalemia and metabolic alkalosis, which can lead to flattened or inverted T waves, the appearance of U waves, ST segment depression, and prolonged QT intervals, as seen in patients with severe hypokalemia (potassium <3.0 mEq/L) 1. The severity of ECG changes correlates with the degree of electrolyte imbalance. Additional ECG findings may include:
- Sinus bradycardia or tachycardia depending on the patient's volume status and autonomic response. These changes are reversible with correction of the underlying electrolyte abnormalities, which requires addressing the gastric outlet obstruction and restoring normal fluid and electrolyte balance through IV rehydration with potassium supplementation (typically KCl 10-20 mEq/L in IV fluids, with rates determined by severity of depletion) 1. Continuous cardiac monitoring is recommended in patients with significant ECG changes until electrolyte abnormalities are corrected. Given the options provided, the most accurate answer is A) depressed ST segment, as this is one of the common ECG changes associated with hypokalemia and metabolic alkalosis in the context of gastric outlet obstruction 1.
From the Research
Early ECG Changes in Gastric Outlet Obstruction
The early ECG changes in a case of non-bilious vomiting due to gastric outlet obstruction can be related to the metabolic and electrolyte disturbances that occur as a result of the obstruction.
- Hypokalemia is a common finding in patients with gastric outlet obstruction due to persistent vomiting, which leads to potassium loss 2, 3.
- Hypokalemia can cause various ECG changes, including:
- Depressed ST segment
- Flattened or inverted T waves
- Presence of U waves
- However, the most specific ECG change associated with hypokalemia is the presence of U waves, but among the given options, the closest related change would be a depressed ST segment or T wave abnormalities.
Relevant ECG Changes
Given the options provided:
- A) Depressed ST segment: This can be seen in hypokalemia, which is a common electrolyte disturbance in gastric outlet obstruction.
- B) Elevated T wave: This is not typically associated with the early stages of hypokalemia or gastric outlet obstruction.
- C) P wave prominent: This is not directly related to the common electrolyte imbalances seen in gastric outlet obstruction.
- D) T wave sagging: While T wave changes can occur, "sagging" is not a standard description used in the context of hypokalemia or gastric outlet obstruction.
Based on the information provided and the typical ECG changes associated with hypokalemia, the most appropriate answer related to early ECG changes in gastric outlet obstruction would be related to hypokalemia's effects on the ECG, such as a depressed ST segment 3.