Atrial fibrillation with rapid ventricular response is common in critical illness. It is often a sign of physiologic stress rather than an isolated rhythm problem.
The atria become irritable in sepsis, hypoxemia, pulmonary embolism, hemorrhage, alcohol withdrawal, postoperative stress, electrolyte abnormalities, catecholamine exposure, and volume overload. The ventricular rate may worsen hemodynamics by reducing diastolic filling time and increasing myocardial oxygen demand. But rate control alone may not fix the patient.
The first question is stability. If atrial fibrillation is causing hypotension, ischemia, pulmonary edema, or shock, synchronized cardioversion may be needed. If the patient is not crashing, evaluate the trigger.