Management of Shivering During Active Cooling
Use a multimodal stepwise approach starting with non-pharmacologic measures (surface counterwarming) plus acetaminophen and magnesium, then escalate through analgesics and sedatives, reserving neuromuscular blockade as the most effective but final option when other measures fail. 1
Stepwise Approach to Shivering Management
First-Line: Non-Pharmacologic + Adjuncts
- Surface counterwarming (warming extremities, especially ears, palms, soles) reduces shivering threshold by ~4°C per 4°C increase in mean skin temperature 1
- Acetaminophen: Standard dosing as antipyretic adjunct 1
- Magnesium sulfate: 2-4 g bolus, then 1 g/h infusion (keep levels <4 mg/dL) 1
- Caveat: These adjuncts alone are typically insufficient for clinically significant shivering but have excellent safety profiles 1
Second-Line: Intensify Sedation/Analgesia
- Analgesic-first approach: Fentanyl bolus + continuous infusion (moderate dose) 1
- Add sedative: Propofol or dexmedetomidine infusion if inadequate with analgesic alone 1
- Meperidine: Most effective opioid for shivering (lowers threshold AND suppresses shivering) 1
Third-Line: Neuromuscular Blockade (NMB)
NMB is the most effective abortive measure for shivering 1 and should be used when:
- Less aggressive measures fail to control shivering
- Rapid temperature induction is needed
- Patient has hemodynamic instability limiting sedative tolerance 1
NMB Agent Selection:
| Agent | Bolus | Infusion | Key Points |
|---|---|---|---|
| Cisatracurium (preferred) | 0.1-0.2 mg/kg | 0.5-10 μg/kg/min | Non-enzymatic degradation; safe in renal/hepatic impairment [1] |
| Rocuronium | 0.6-1 mg/kg | 3-12 μg/kg/min | Longer-acting; risk of tachyphylaxis; decreased clearance in hypothermia [1] |
| Vecuronium | 0.1 mg/kg | 0.8-2 μg/kg/min | Avoid in renal impairment [1] |
NMB Dosing Strategy:
- Induction phase: Use 1-2 boluses of longer-acting agent to rapidly achieve target temperature 1
- Maintenance phase: Continuous infusion only if other measures fail 1
- Titrate to minimum dose that suppresses shivering and maintains goal temperature (NOT train-of-four 1-2 as in typical ICU practice) 1
- Monitor for seizures with EEG during NMB as clinical manifestations are masked 1
Phase-Specific Considerations
Induction Phase (0-2 hours)
- Deep sedation required 1
- Shivering is most problematic during this phase 1
- NMB often needed to achieve rapid cooling 1
Maintenance Phase
- Moderate sedation 1
- Lower sedative doses may be needed than during induction, especially at 33°C target 1
- Continue titrating to minimum dose that prevents shivering 1
Rewarming Phase
- Reduce to light sedation 1
- Avoid NMB to allow neurological assessment 1
- Wean analgesics/sedatives to lowest tolerated dose 1
Critical Hemodynamic Considerations
In patients with cardiogenic shock (common post-cardiac arrest):
- Minimize sedative doses as propofol and dexmedetomidine worsen hemodynamic compromise 1
- Ketamine may be reasonable but can suppress myocardial contractility when catecholamine reserves depleted 1
- Lower threshold to initiate NMB rather than escalating sedatives 1
Common Pitfalls
Infection masquerading as shivering: Shivering and hyperthermia may indicate infection post-cardiac arrest; consider empiric antibiotics 1
Drug accumulation: Sedatives accumulate during hypothermia due to reduced metabolism/clearance, causing delayed awakening 1
- Delay neuroprognostication ≥72 hours after rewarming AND sedation discontinuation 1
Tachyphylaxis with NMB: All NMB agents can develop tolerance requiring dose escalation 1
Seizure masking: NMB prevents clinical seizure detection; continuous EEG monitoring essential 1
Evidence Quality Note
The 2023 European Heart Journal guidelines 1 represent the most comprehensive and recent expert consensus on this topic. Implementation studies 2, 3 demonstrate that stepwise protocols reduce shivering incidence (57% to 39%, p=0.03) and neuromuscular blocker use (19% to 6%, p=0.02) while improving survival to discharge (35% to 55%, p=0.02) 3.