A patient with a history of alcoholism and liver cirrhosis presents to the ED with diffuse abdominal pain, rigidity, and rebound tenderness. Labs show elevated WBC count and a lactate of 4 mmol/L. The patient has hypotension and tachycardia despite fluid resuscitation. Which immediate intervention is MOST appropriate for this patient?
Administer intramuscular analgesics for pain relief.
Perform an immediate diagnostic paracentesis.
Start the patient on oral lactulose for hepatic encephalopathy.
Initiate broad-spectrum intravenous antibiotics.