Laboratory investigations may be helpful in establishing diagnosis and directing management of shock.

• Complete blood count

• In acute blood loss, hemoglobin and hematocrit levels may remain normal until volume repletion.
• Leukocytosis with or without a left shift of neutrophils suggests sepsis.
• Thrombocytopenia with alterations in coagulation panel indicates disseminated intravascular coagulation (DIC), which may be a complication of sepsis.

• Electrolytes

• Decreased bicarbonate levels may be the primary deficit in metabolic acidosis or the compensatory change in respiratory alkalosis.
• Hyperkalemia due to transcellular shift is commonly associated with metabolic acidosis.

• Coagulation panel (PT, PTT, INR, etc.)

• Abnormalities in coagulation panel may be caused by disseminated intravascular coagulation (DIC), over-anticoagulation, or hepatic failure.

• Cardiac markers

• Check troponin and CK-MB levels when suspecting myocardial infarction.
• Elevation in cardiac markers may be associated with both cardiac and extracardiac etiologies.

• Liver function

• Increased levels of conjugated bilirubin, alkaline phosphatase, and hepatic aminotransferases are typically seen in ischemic hepatitis (“shock liver”) due to cardiogenic shock.

• Renal function

• Prerenal azotemia and/or acute tubular necrosis may be associated with conditions of hypovolemia or reduced cardiac output.
• Oliguria (urine output <0.5 mL/kg/h) is usually evident.

• Lactate

• Hyperlactatemia generally reflects the development of anaerobic metabolism in hypoperfused tissue and/or imparied hepatic clearance.
• Lactate level could decrease within hours with effective therapy.^[1]

• Arterial blood gas

• Lactic acidosis may be an indicator of tissue hypoperfusion typically seen in septic shock.
• Combined acid-base disorders are fequently encountered in different stages of shock.
• Severe acidosis could blunt the effectiveness of vasopressors and potentiate the development of arrhythmias.

• Cultures

• Samples of blood, urine, and/or sputum should be sent for culture before administering antibiotics if sepsis is concerned.

• Nasogastric aspirate

• A negative nasogastric aspirate does not rule out upper gastrointestinal bleeding.

• Pregnancy test

• A pregnancy test should be performed on hypotensive women of childbearing age presenting with lower abdominal pain.