What is the recommended management of postoperative shivering in a cardiac patient undergoing non‑cardiac surgery?

Management of Postoperative Shivering in Cardiac Patients Undergoing Non-Cardiac Surgery

Prevent shivering by maintaining normothermia intraoperatively, and if shivering occurs postoperatively, treat it immediately with meperidine (25-50 mg IV) or tramadol (1-2 mg/kg IV) combined with active rewarming, as shivering increases myocardial oxygen demand and can precipitate cardiac injury through oxygen supply-demand mismatch in cardiac patients. 1

Why Shivering is Dangerous in Cardiac Patients

Shivering poses specific cardiac risks that demand aggressive management:

• Hypothermia-induced shivering leads to perioperative cardiac injury due to an imbalance of oxygen supply and demand 1
• Shivering increases sympathetic nervous system activity, making hypothermia proarrhythmogenic 1
• Oxygen consumption increases proportionally to the solicited muscle mass, creating metabolic stress 2
• In cardiac surgery patients, shivering causes mixed venous oxygen saturation (SvO2) to decrease from 74±6% to 57±12%, representing dangerous oxygen depletion 3
• Shivering increases catecholamine release and can induce lactic acidosis 4

Prevention Strategy (First-Line Approach)

Active warming to maintain normothermia is the primary prevention method:

• Maintain core body temperature ≥36°C throughout the perioperative period 1
• A prospective study of 8,841 orthopedic surgery patients showed body temperature ≥36°C was associated with significantly lower risks for cardiac or cerebral events 1
• Use forced-air warming devices intraoperatively and postoperatively 4, 2
• Maintenance of normothermia is reasonable to reduce perioperative cardiac events 1

Treatment Algorithm When Shivering Occurs

Immediate Pharmacological Intervention

First-line medications (choose one):

• Meperidine 25-50 mg IV - Most validated treatment when combined with forced-air warming 4, 3

  • In cardiac surgery patients, meperidine successfully returned SvO2 to baseline and stopped shivering within 10 minutes 3
  • Effective at reducing the shivering threshold temperature 2

• Tramadol 1-2 mg/kg IV - Highly effective alternative 5

  • Tramadol 2 mg/kg showed best efficacy at 1 and 5 minutes post-treatment 5
  • Tramadol 1 mg/kg remained effective at 10 minutes 5
  • Acts by reducing shivering threshold temperature 2

Second-Line Options

If first-line agents fail or are contraindicated:

• Nefopam 10 mg IV - Showed consistent efficacy across all time points (1,5, and 10 minutes) 5
• Clonidine 75-150 µg IV - Effective with statistical significance, particularly at 5 minutes 5
• Doxapram 2 mg/kg IV - Effective at 1 minute, though evidence is limited 5

Non-Pharmacological Adjuncts

Always combine with active rewarming:

• Postoperative skin surface rewarming rapidly achieves threshold shivering temperature 2
• Forced-air warming devices improve patient comfort and raise skin temperature 2
• However, active rewarming alone is less efficient than pharmacological interventions 2

Addressing Underlying Causes

Treat contributing factors simultaneously:

• Pain control - Postoperative pain causes non-thermoregulatory shivering even in normothermic patients 6, 2
• Opioid withdrawal - Acute withdrawal from short-acting narcotics can trigger shivering 4
• Cytokine release - Surgical trauma releases cytokines that cause thermoregulatory-related shivering 6

Monitoring Requirements

For cardiac patients experiencing shivering:

• Monitor mixed venous oxygen saturation (SvO2) if pulmonary artery catheter is in place 3
• Assess for signs of myocardial ischemia (chest pain, ECG changes, hemodynamic instability) 1
• Continuous ECG monitoring for arrhythmias 1
• Monitor core temperature continuously 1

Critical Pitfalls to Avoid

Common errors that worsen outcomes:

• Delaying treatment while waiting for shivering to resolve spontaneously - this allows progressive oxygen debt to develop 3
• Using inadequate doses of pharmacological agents - underdosing prolongs oxygen consumption 3, 5
• Relying solely on passive warming without pharmacological intervention in cardiac patients 2
• Failing to address pain as a contributing factor to non-thermoregulatory shivering 6, 2
• Not recognizing that shivering can occur even in normothermic patients (>35.5°C) 1

Special Considerations for High-Risk Cardiac Patients

Patients requiring heightened vigilance:

• Those with recent myocardial infarction or unstable coronary syndromes 1
• Patients with decompensated heart failure or reduced ejection fraction 1
• Those with significant arrhythmias or conduction abnormalities 1
• Patients with severe valvular disease 1

In these populations, even brief episodes of shivering can precipitate major adverse cardiac events (MACE) through increased myocardial oxygen demand 1.