Post-Operative Shivering Causes and Management

Common Causes of Postoperative Shivering

• Hypothermia is the most common cause of postoperative shivering, which can persist beyond the immediate recovery period, according to the American Society of Anesthesiologists 1, 2
• Patients may experience delayed hypothermia due to redistribution of heat from the core to the periphery even on day 2, as reported in Anaesthesia 2
• Inadequate thermal management during the perioperative period can lead to persistent temperature dysregulation, as stated by the American Society of Anesthesiologists 1
• Inadequate pain control on day 2 may manifest as shivering, according to the American Society of Anesthesiologists 3
• Early infection can present with temperature spikes and associated shivering, as noted in Anaesthesia 2
• Respiratory and wound infections are common causes of shivering on day 2, as reported in Anaesthesia 2
• A spike in temperature with shivering may be an early sign of infection requiring prompt evaluation, according to Anaesthesia 2
• Reduction in sedative medications that were suppressing shivering response can contribute to postoperative shivering, as stated by the European Heart Journal 4
• Medication interactions affecting thermoregulatory control can also contribute to shivering, as reported by Circulation 5

Risk Factors for Postoperative Shivering

• Inadequate intraoperative warming is a risk factor for postoperative shivering, according to the American Society of Anesthesiologists 1
• Prolonged surgical exposure is also a risk factor, as noted in Anaesthesia 2

Evaluation of Postoperative Shivering on Day 2

• Measuring core temperature is essential to differentiate between hypothermic and normothermic shivering, as recommended by the American Society of Anesthesiologists 1
• Assessing for signs of infection, such as checking wound sites and respiratory status, is crucial, according to Anaesthesia 2
• Evaluating intravenous cannula sites for phlebitis is also important, as reported in Anaesthesia 2
• Checking for symptoms of sepsis if temperature ≥ 38.0°C is necessary, as stated by Anaesthesia 2

Management Approach

• Implementing active warming with forced-air warming devices is recommended for hypothermia-related shivering, according to the American Society of Anesthesiologists 1
• Ensuring normothermia is maintained through appropriate ambient temperature is crucial, as noted in Anaesthesia 2
• Using warmed intravenous fluids if needed is also recommended, as reported in Anaesthesia 2
• Considering NSAIDs for pain-related shivering, if not contraindicated, is an option, according to Anaesthesia 6
• Ensuring regular rather than as-needed pain medication administration is important, as stated by Anaesthesia 7
• Obtaining blood cultures if fever is present is necessary for infection-related shivering, according to Anaesthesia 2
• Initiating appropriate antibiotics if infection is suspected is crucial, as reported in Anaesthesia 2
• Providing supportive care, including hydration and oxygenation, is essential, as stated by Anaesthesia 2
• Meperidine (25-50mg) is the most effective medication for treating established shivering, according to the American Society of Anesthesiologists 1, 3

Prevention Strategies for High-Risk Patients

• Maintaining perioperative normothermia through active warming is recommended, according to the American Society of Anesthesiologists 1
• Adequate hydration throughout the perioperative period is crucial, as noted in Anaesthesia 2
• Monitoring for early signs of infection and treating promptly is essential, as reported in Anaesthesia 2

Special Considerations

• Patients with sickle cell disease require particular attention to prevent shivering, as it can lead to sickling crisis, according to Anaesthesia 2
• Patients who have undergone neuraxial anesthesia may experience delayed shivering on day 2 as the block wears off, as reported in Anaesthesia 7

Pharmacologic Management of Shivering

Introduction to Meperidine

• Meperidine is the most effective single pharmacologic agent for treating established shivering, with doses of 25-50 mg IV stopping shivering in nearly 100% of patients within 5 minutes, according to the European Society of Cardiology 8

Mechanism and Efficacy

• Among all opioid analgesics, meperidine uniquely both lowers the shivering threshold and directly suppresses shivering through mechanisms beyond its analgesic properties, making it approximately 2,800 times more effective at inhibiting shivering than would be predicted by its analgesic potency alone 8

Combination Therapy

• When combined with high-dose buspirone (30 mg), meperidine can reduce the shivering threshold to as low as 33°C, providing synergistic benefit for patients requiring aggressive temperature management, as recommended by the European Society of Cardiology 8, 9

Safety Considerations

• Exercise caution with meperidine in patients at risk for seizures, particularly when used in combination with buspirone or in those not continuously monitored, due to the lowered seizure threshold 8, 9
• All opioids and sedatives blunt shivering at the inherent expense of sedation and potential hemodynamic effects, according to the American Heart Association 8

Adjunctive Measures

• Magnesium sulfate and acetaminophen are safe adjuncts with favorable side effect profiles, but when used alone are typically insufficient to suppress clinically significant shivering, and should be considered as part of a multimodal approach rather than monotherapy, as suggested by the European Society of Cardiology 8

Refractory Shivering Management

• Neuromuscular blockade (NMB) is the most effective abortive measure for refractory shivering when pharmacologic approaches fail, particularly appropriate when active temperature management is expected to be transient, such as in post-cardiac arrest care, according to the American Heart Association 8, 9

Pharmacologic Management of Post‑Spinal Shivering

First‑Line Non‑Pharmacologic Measures

• Active forced‑air warming should be started immediately to normalize core temperature and improve patient comfort, addressing hypothermia as the most common trigger for shivering. 10

First‑Line Pharmacologic Treatment

• Meperidine 25–50 mg IV is the drug of choice, achieving cessation of shivering in nearly 100 % of patients within 5 minutes. 10
• The American Society of Anesthesiologists (ASA) endorses meperidine as more effective than other opioid agonists or agonist‑antagonists for treating post‑spinal shivering. 10
• Efficacy metrics: number‑needed‑to‑treat (NNT) = 1.3 at 5 minutes and 1.5 at 10 minutes, indicating that fewer than two patients need treatment for one to benefit compared with placebo. 10

Alternative Pharmacologic Options (when meperidine is unavailable or contraindicated)

• Clonidine 150 µg IV – NNT = 1.3 at 5 minutes; effective but may cause hypotension. 10
• Doxapram 100 mg IV – NNT = 1.7 at 5 minutes. 10
• Ketanserin 10 mg IV – NNT = 2.3 at 5 minutes. 10
• Low‑dose ketamine 0.25 mg/kg IV – reduces incidence and severity of shivering (adjusted odds ratio ≈ 0.43) and results in markedly lower nausea/vomiting compared with tramadol. 10
• Tramadol 0.5 mg/kg IV – less effective than ketamine and associated with a high rate of nausea/vomiting (~60 %). 10

Management of Refractory Shivering

• Neuromuscular blockade is the most effective abortive intervention for shivering unresponsive to pharmacologic measures. 11
• Cisatracurium (0.1–0.2 mg/kg bolus, then 0.5–10 µg/kg/min infusion) is preferred because it undergoes non‑enzymatic degradation and is safe in renal/hepatic impairment. 11
• Indication: reserve for refractory cases where shivering threatens safety (e.g., increased intracranial pressure in neurologic patients or metabolic crisis in high‑risk cardiac patients). 11
• Safety precaution: ensure an adequate depth of sedation before administering neuromuscular blockers. 11

Prevention Strategies (supporting the primary treatment)

• Maintain peri‑operative normothermia through active forced‑air warming and warmed intravenous fluids. 10

Management of Peri‑operative Rigors

Preferred Pharmacologic Agent

• Meperidine 25–50 mg IV is the drug of choice for established shivering, achieving cessation in nearly 100 % of patients within 5 minutes. [12][13]
• The American Society of Anesthesiologists endorses meperidine as the most effective single pharmacologic agent for treating established shivering, citing its superiority over other opioid agonists and agonist‑antagonists. 12

Mechanism of Action & Enhanced Efficacy

• Meperidine uniquely lowers the shivering threshold and directly suppresses shivering through mechanisms beyond its analgesic properties, making it the most effective agent for this indication. [12][13]
• When combined with buspirone (30 mg), meperidine can reduce the shivering threshold to approximately 33 °C in patients requiring aggressive temperature management. 13

Dosing and Expected Outcomes

• Recommended dose: 25–50 mg IV (or weight‑based equivalent) administered for active shivering. Expected rapid effect: shivering stops in ≤5 minutes in almost all patients. [12][13]

Non‑pharmacologic First‑line Measures

• Initiate active forced‑air warming immediately to normalize core temperature, as hypothermia is the most common trigger for shivering. 12

Adjunctive Therapies (Supportive, Not Stand‑alone)

• Acetaminophen combined with magnesium sulfate (2–4 g bolus, then 1 g/h infusion) is safe but insufficient as monotherapy for clinically significant shivering; they should be used only as adjuncts. 13

Rescue Strategy for Refractory Shivering

• Neuromuscular blockade with cisatracurium (0.1–0.2 mg/kg IV bolus, then 0.5–10 µg/kg/min infusion) is the most effective abortive measure when pharmacologic approaches fail, provided adequate sedation is ensured. 13

Safety Considerations & Contraindications

• Meperidine lowers the seizure threshold; caution is advised in patients at risk for seizures, especially when combined with buspirone or when continuous monitoring is unavailable. 13
• Tramadol should not be used as first‑line therapy for shivering when meperidine or other more effective agents are available. 12
• Acetaminophen or magnesium alone should not be relied upon for clinically significant shivering; they are adjuncts only. 13