In a postoperative patient with shivering (rigor), should I use active warming or cooling to stop it?

Use Active Warming to Stop Postoperative Shivering

In a postoperative patient with shivering, you should use active warming devices (forced-air warming) to address the underlying hypothermia while simultaneously administering meperidine 25-50 mg IV for immediate shivering suppression. 1, 2

Understanding the Pathophysiology

Postoperative shivering is primarily thermoregulatory—a normal physiological response to core hypothermia that develops during surgery. 1, 3, 4 The key insight is that cooling the patient would be counterproductive and worsen the problem, as you would be fighting against the body's attempt to restore normal temperature. 3, 4

• Core temperature typically drops 0.5-1.5°C within the first 30-60 minutes of anesthesia due to heat redistribution from core to periphery and impaired thermoregulation. 5
• Even on postoperative day 2, patients may experience delayed hypothermia from continued heat redistribution. 1
• Shivering doubles metabolic rate and nearly triples oxygen consumption, creating significant physiological stress. 1, 2

Immediate Management Algorithm

Step 1: Active Warming (Primary Intervention)

• Apply forced-air warming devices immediately—this is the most validated non-pharmacological method and addresses the root cause. 1, 6
• Use warmed intravenous fluids if the patient is receiving fluid resuscitation. 1, 2
• Ensure adequate ambient room temperature. 1
• Important caveat: While active warming improves thermal comfort and reduces oxygen consumption, it does not quickly eliminate shivering on its own—the duration of shivering remains similar with or without warming (approximately 36-37 minutes). 7

Step 2: Pharmacologic Suppression (Concurrent with Warming)

• Administer meperidine 25-50 mg IV—this is the single most effective pharmacologic agent, stopping shivering in nearly 100% of patients within 5 minutes. 1, 2
• Meperidine is approximately 2,800 times more effective at inhibiting shivering than predicted by its analgesic potency alone, uniquely lowering the shivering threshold while directly suppressing the response. 1, 2
• The combination of forced-air warming devices and intravenous meperidine is the most validated treatment method. 6

Step 3: Adjunctive Measures

• Consider acetaminophen as a non-sedating adjunct, though it is insufficient alone for clinically significant shivering. 1, 2
• Magnesium sulfate (2-4 g bolus, then 1 g/h infusion) can be added but should not be used as monotherapy. 1, 2

Rule Out Alternative Causes

Before attributing shivering solely to hypothermia, measure core temperature and assess for:

• Infection: Check for fever ≥38.0°C, examine wound sites, assess respiratory status, and evaluate IV sites for phlebitis. 1
• Inadequate pain control: Pain-related shivering may manifest on postoperative day 2; ensure regular rather than as-needed pain medication administration. 1, 3
• Medication effects: Reduction in sedatives that were suppressing shivering response can unmask the problem. 1

Critical Pitfalls to Avoid

• Do not cool the patient—this worsens the underlying problem and increases metabolic stress. 3, 4
• Do not rely on warming alone without pharmacologic intervention—while warming addresses the cause, it does not rapidly eliminate shivering and the patient continues to experience metabolic stress during the 30+ minute shivering duration. 7
• Do not use acetaminophen or magnesium as monotherapy—these are adjuncts only and insufficient for clinically significant shivering. 1, 2
• Do not assume shivering is benign—it indicates failed thermoregulation and carries metabolic consequences including increased risk of myocardial ischemia, surgical site infection, and coagulopathy. 5, 4

Special Populations

• Patients with sickle cell disease require particular attention, as shivering can precipitate sickling crisis—aggressive warming and early pharmacologic suppression are essential. 1
• Patients who received neuraxial anesthesia may experience delayed shivering on day 2 as the sympathetic block wears off. 1

Refractory Cases

If shivering persists despite warming and meperidine:

• Add continuous opioid infusion (fentanyl or hydromorphone) with short-acting sedative (dexmedetomidine or propofol) titrated to minimum effective dose. 2
• Last resort: Neuromuscular blockade with cisatracurium is the most effective abortive measure for refractory shivering when all other approaches fail. 1, 2