Is tramadol appropriate for managing rigors (shivering) in a patient with fever or postoperative shivering?

Tramadol for Rigors

Tramadol is NOT the preferred agent for treating rigors—meperidine (25-50 mg IV) is the drug of choice, stopping shivering in nearly 100% of patients within 5 minutes and is approximately 2,800 times more effective at inhibiting shivering than predicted by its analgesic potency alone. 1, 2

Why Meperidine is Superior to Tramadol

Meperidine uniquely lowers the shivering threshold and directly suppresses shivering through mechanisms beyond its analgesic properties, making it the most effective single pharmacologic agent endorsed by the American Society of Anesthesiologists for treating established shivering. 1, 2

• The ASA explicitly states that meperidine is more effective than other opioid agonists or agonist-antagonists for the reduction of shivering during emergence and recovery. 1
• Meperidine achieves a number-needed-to-treat (NNT) of 1.3 at 5 minutes and 1.5 at 10 minutes, meaning fewer than two patients need treatment for one to benefit. 2
• When combined with buspirone (30 mg), meperidine can reduce the shivering threshold to as low as 33°C for patients requiring aggressive temperature management. 1, 2

Tramadol's Limited Role

While tramadol has been studied for postoperative shivering prevention and treatment, it is significantly less effective than meperidine and carries a higher risk of adverse effects:

• Tramadol (0.5 mg/kg IV) is associated with a high rate of nausea/vomiting (~60%) compared to alternatives like low-dose ketamine. 2
• Low-dose ketamine (0.25 mg/kg IV) reduces shivering incidence and severity more effectively than tramadol (adjusted odds ratio ≈ 0.43) with markedly lower nausea/vomiting. 2
• Although tramadol 1 mg/kg may be more effective than pethidine 0.5 mg/kg in some studies, this comparison used a suboptimal pethidine dose—the standard effective dose is 25-50 mg (approximately 0.35-0.7 mg/kg for a 70 kg patient). 3

Critical Safety Concern: Serotonin Syndrome Risk

Tramadol carries a significant risk of serotonin syndrome when combined with other serotonergic agents, which is particularly relevant in the perioperative setting:

• Tramadol inhibits serotonin reuptake and can precipitate serotonin syndrome when combined with meperidine or other serotonergic medications. 4, 5
• Case reports document serotonin syndrome resulting from tramadol-meperidine interactions in the post-anesthesia care unit, presenting with altered mental status, respiratory distress, fever, and hemodynamic instability. 4
• The increased use of serotonergic antidepressants in surgical patients represents an underrecognized potential for dangerous multidrug interactions. 4

Recommended Treatment Algorithm for Rigors

First-Line Non-Pharmacologic Measures

• Initiate active forced-air warming immediately to normalize core temperature, as hypothermia is the most common cause of shivering. 1, 2, 6
• Ensure adequate ambient room temperature and use warmed intravenous fluids. 2, 6

First-Line Pharmacologic Treatment

• Administer meperidine 25-50 mg IV as the drug of choice for established shivering. 1, 2
• Expect cessation of shivering within 5 minutes in nearly 100% of patients. 1, 2

Alternative Options (when meperidine is contraindicated or unavailable)

• Clonidine 150 µg IV (NNT = 1.3 at 5 minutes, but may cause hypotension). 2
• Low-dose ketamine 0.25 mg/kg IV (more effective than tramadol with lower nausea/vomiting rates). 2
• Doxapram 100 mg IV (NNT = 1.7 at 5 minutes). 2
• Consider tramadol 0.5-1 mg/kg IV only as a last resort when other agents are unavailable, recognizing its inferior efficacy and higher adverse effect profile. 2, 7, 8

Adjunctive Measures

• Acetaminophen and magnesium sulfate (2-4 g bolus, then 1 g/h) are safe adjuncts but insufficient as monotherapy for clinically significant shivering. 1, 2, 6

Refractory Shivering

• Neuromuscular blockade with cisatracurium (0.1-0.2 mg/kg bolus, then 0.5-10 µg/kg/min infusion) is the most effective abortive measure when pharmacologic approaches fail. 1, 2, 6
• Ensure adequate depth of sedation before administering neuromuscular blockers. 2

Common Pitfalls to Avoid

• Do not use tramadol as first-line therapy when meperidine or other more effective alternatives are available. 1, 2
• Do not combine tramadol with meperidine or other serotonergic agents due to serotonin syndrome risk. 4
• Do not rely on acetaminophen or magnesium alone for clinically significant shivering—these are adjuncts only. 1, 6
• Exercise caution with meperidine in patients at risk for seizures, particularly when combined with buspirone or in those not continuously monitored, as it lowers the seizure threshold. 1, 2