How should post‑spinal shivering be managed?

Management of Post-Spinal Shivering

Meperidine 25-50 mg IV is the single most effective treatment for post-spinal shivering, stopping shivering in nearly 100% of patients within 5 minutes. 1, 2, 3

Immediate Assessment

When shivering occurs after spinal anesthesia, rapidly assess:

• Core temperature measurement to differentiate hypothermic from normothermic shivering 2
• Fever ≥38.0°C warrants blood cultures and consideration of early infection (respiratory, wound, or IV site phlebitis) 2, 4
• Pain assessment, as inadequate analgesia can manifest as shivering 2
• Timing of onset, as delayed shivering (day 2 postoperatively) suggests infection, pain, or redistribution hypothermia 2

Treatment Algorithm

First-Line: Non-Pharmacologic Warming

Initiate active warming immediately with forced-air warming devices, which normalize patient temperature and improve comfort. 1, 2 This addresses the most common cause—hypothermia from perioperative heat loss. 2, 5

• Warm extremities specifically (surface counterwarming) to reduce shivering threshold by approximately 4°C per degree of mean skin temperature increase 6
• Administer warmed IV fluids if resuscitation is ongoing 6, 2
• Ensure adequate ambient room temperature 6

Second-Line: Meperidine (Drug of Choice)

If shivering persists despite warming, administer meperidine 25-50 mg IV. 1, 2, 3

• Mechanism: 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 shivering through non-analgesic mechanisms. 6, 2
• Efficacy: Number-needed-to-treat (NNT) is 1.3 at 5 minutes and 1.5 at 10 minutes—meaning fewer than two patients need treatment for one to stop shivering who would have continued with placebo. 3
• Onset: Shivering cessation occurs within 5 minutes in nearly 100% of patients. 6, 2, 3
• ASA endorsement: The American Society of Anesthesiologists explicitly states meperidine is more effective than other opioid agonists or agonist-antagonists for treating shivering. 1

Alternative Pharmacologic Options

If meperidine is unavailable or contraindicated:

• Clonidine 150 mcg IV: NNT 1.3 at 5 minutes, highly effective but may cause hypotension 3
• Doxapram 100 mg IV: NNT 1.7 at 5 minutes 3
• Ketanserin 10 mg IV: NNT 2.3 at 5 minutes 3
• Low-dose ketamine 0.25 mg/kg IV: Reduces incidence and severity of post-spinal shivering (AOR 0.427), with significantly lower nausea/vomiting compared to tramadol 7, 8
• Tramadol 0.5 mg/kg IV: Less effective than ketamine and associated with 60.9% incidence of nausea/vomiting versus 3.1% with ketamine 7

Adjunctive Agents (Insufficient as Monotherapy)

Do not rely on these alone for clinically significant shivering—they are adjuncts only: 6, 2

• Magnesium sulfate 2-4 g bolus, then 1 g/h infusion (maintain serum <4 mg/dL) 6
• Acetaminophen: Non-sedating but typically insufficient alone 6
• NSAIDs: Consider for pain-related shivering if not contraindicated 2

Refractory Shivering: Neuromuscular Blockade

For shivering unresponsive to pharmacologic measures, neuromuscular blockade is the most effective abortive intervention. 6, 2

• Cisatracurium 0.1-0.2 mg/kg bolus, then 0.5-10 mcg/kg/min infusion (preferred due to non-enzymatic degradation, safe in renal/hepatic impairment) 6
• Indication: Reserve for refractory cases, particularly when shivering threatens patient safety (e.g., increased ICP in neurologic patients, metabolic crisis in high-risk cardiac patients) 1, 6
• Caution: Ensure adequate sedation depth before administering neuromuscular blockers 1

Prevention Strategies

For high-risk patients (prolonged surgery, inadequate intraoperative warming, elderly, cardiopulmonary disease):

• Prewarming for 15 minutes before spinal anesthesia with forced-air devices, blankets, or warmed gowns 8
• Prophylactic low-dose ketamine 0.25 mg/kg IV before spinal anesthesia reduces incidence from 43.8% to 28.7% 7, 8
• Maintain perioperative normothermia through active warming and warmed IV fluids 1, 2
• Intrathecal meperidine 0.2 mg/kg added to spinal anesthetic reduces shivering incidence from 56.7% to 16.7%, though nausea may occur 9

Critical Pitfalls to Avoid

• Do not use acetaminophen or magnesium as monotherapy for established shivering—they are adjuncts only and will fail for clinically significant shivering 6, 2
• Do not overlook infection as a cause, especially if fever ≥38.0°C or delayed onset (day 2 postoperatively)—obtain cultures and consider empiric antibiotics 2, 4
• Avoid propofol or dexmedetomidine as first-line agents in hemodynamically unstable patients due to hypotension risk; use meperidine or have lower threshold for neuromuscular blockade 6
• Exercise caution with meperidine in seizure-prone patients, particularly when combined with buspirone or in unmonitored settings 2
• Do not ignore pain as a cause—ensure adequate analgesia with scheduled (not PRN) dosing 2

Special Populations

• Sickle cell disease patients: Shivering prevention is critical as it can precipitate sickling crisis—aggressive warming and prophylactic pharmacologic measures are essential 2, 4
• Cardiac patients: Shivering doubles metabolic rate and nearly triples oxygen consumption, creating dangerous supply-demand mismatch—treat aggressively to prevent myocardial ischemia 6, 4, 5
• Traumatic brain injury patients: Shivering increases ICP and cerebral metabolic stress—ensure adequate sedation before neuromuscular blockade if ICP is labile 1