Dexamethasone and Diphenhydramine for Postoperative Shivering
Dexamethasone is effective for preventing postoperative shivering, but diphenhydramine (Avil) has no established role in shivering management and should not be used for this indication. 1, 2
Evidence for Dexamethasone
Dexamethasone significantly reduces postoperative shivering with a relative risk of 0.39 (95% CI: 0.23-0.63), meaning it prevents shivering in approximately 60% of cases where it would otherwise occur. 3
Mechanism and Efficacy
- Dexamethasone works by decreasing the gradient between core and skin temperature and modifying the inflammatory response that contributes to postoperative shivering 4
- In cardiac surgery patients, dexamethasone decreased shivering incidence from 33.0% to 13.1% (P = 0.001), independent of temperature and cardiopulmonary bypass duration 4
- One randomized trial found dexamethasone superior to meperidine (pethidine) for preventing postoperative shivering, with only 10% shivering incidence versus 47.5% in placebo group 5
Dosing Recommendations
- The effective dose for shivering prevention is 0.1 mg/kg IV administered 15 minutes before anesthesia 6
- For cardiac surgery, 0.6 mg/kg has been used successfully 4
- The FDA label indicates general dosing ranges from 0.5 to 9 mg daily depending on indication, though shivering prevention is not a labeled indication 7
Additional Benefits
- Dexamethasone provides antiemetic effects, reducing postoperative nausea (RR: 0.54) and vomiting (RR: 0.37) 3
- It prolongs postoperative analgesia by approximately 270 minutes following spinal anesthesia 6
- The drug significantly decreases fatigue and improves quality of recovery 8
Evidence Against Diphenhydramine (Avil)
Diphenhydramine has no established efficacy for treating or preventing shivering and is not mentioned in any shivering management guidelines. 1, 2
- The only available evidence shows diphenhydramine combined with metoclopramide reduces postoperative nausea and vomiting when added to patient-controlled analgesia, but this study made no mention of shivering effects 9
- The FDA label for diphenhydramine (Avil) provides only contraindication information and does not list shivering as an indication 10
Recommended Shivering Management Algorithm
First-Line Approach
- Administer dexamethasone 0.1 mg/kg IV prophylactically before anesthesia for shivering prevention 3, 6
- Initiate surface counterwarming immediately, particularly warming extremities 1, 2
If Shivering Occurs Despite Prophylaxis
- Meperidine 12.5-50 mg IV is the single most effective treatment, 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 1
Alternative Agents (if meperidine unavailable)
- Magnesium sulfate 2-4 g bolus, then 1 g/h infusion as adjunct 1, 2
- Moderate-dose continuous opioid infusion (fentanyl or hydromorphone) plus short-acting sedative (dexmedetomidine or propofol) 1
Critical Pitfalls to Avoid
- Do not use diphenhydramine for shivering management—there is no evidence supporting this practice 1, 2, 10
- Do not rely on acetaminophen or magnesium alone for clinically significant shivering, as these are insufficient as monotherapy 1
- Remember that shivering doubles metabolic rate and nearly triples oxygen consumption, creating significant energy supply-demand mismatch 2
- If shivering occurs with fever, consider sepsis and obtain blood cultures if temperature ≥38.0°C 1