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Spinal anaesthesia induced shivering with management

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"spinal anaesthesia" AND "shivering" AND "management"

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"shivering" AND "neuraxial" AND "meperidine OR dexmedetomidine"

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PMID: 39608094

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Spinal Anaesthesia-Induced Shivering

Definition and Incidence

Shivering is one of the most common complications of spinal (neuraxial) anaesthesia, with an incidence of approximately 40-55% of patients. In the obstetric population undergoing caesarean section it affects up to 52% of patients, making it a major management concern.

Pathophysiology

1. Thermoregulatory Physiology

In the unanesthetized patient, the hypothalamus maintains core temperature within a very narrow "interthreshold range" - sweating and vasodilation at the warm end, vasoconstriction and shivering at the cold end. A drop of even a fraction of a degree below the lower threshold triggers vasoconstriction and shivering.
  • Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 2295

2. How Spinal Anaesthesia Disrupts This

Spinal and epidural anaesthetics produce thermoregulatory disruption through two key mechanisms:
a) Heat redistribution (Phase 1 - the major cause) Neuraxial blockade causes vasodilation in the blocked dermatomes, redistributing heat from warm central compartments (abdomen, thorax) to cooler peripheral tissues (arms, legs). This causes a steep 1-2°C drop in core temperature within the first hour. This is the single most important cause of hypothermia and shivering under neuraxial anaesthesia.
b) Impaired afferent thermal signalling The blocked dermatomes send false (abnormally cool) afferent signals to the hypothalamus. The hypothalamus "perceives" that the body's lower half is cold even when core temperature is acceptable, triggering a shivering response that cannot be resolved by the blocked peripheral vasoconstriction. This leads to paradoxical shivering without true systemic hypothermia in many patients.
c) Lowering of the shivering threshold Both spinal and epidural anaesthetics decrease the threshold temperature at which vasoconstriction and shivering are triggered, and decrease sympathetic tone, blunting the normal vasoconstrictive defense against cold.
  • Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 2294-2295
  • Miller's Anesthesia, 10e, p. 2734

Why Shivering is Harmful

Intense shivering is not merely uncomfortable - it carries serious physiological consequences:
EffectClinical Significance
O2 consumption increases up to 5-foldMay cause hypoxaemia
CO2 production rises sharplyRespiratory burden
Cardiac output rises sharplyPoorly tolerated in cardiac patients
Myocardial ischemia risk increasedSignificant in CAD patients
Metabolic acidosisResolves once shivering stops
Rarely: hyperthermia (38-39°C)Can be paradoxical finding
Wound dehiscence / increased painPractical surgical concern
  • Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 2295-2296
  • Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 2435

Management

Management is divided into non-pharmacological (preventive) and pharmacological (preventive and therapeutic) strategies.

A. Non-Pharmacological (Prevention First-Line)

  1. Pre-warming - Warming the patient for 30 minutes before anaesthesia with convective forced-air warming blankets significantly reduces the Phase 1 redistribution temperature drop by reducing the central-peripheral gradient. This is the most effective preventive strategy.
  2. Intraoperative forced-air warming blankets - Applied intraoperatively to reduce Phase 2 heat loss.
  3. Warmed intravenous fluids - Room-temperature large-volume IV fluids are a significant contributor to hypothermia; warming them prevents this.
  4. Warm-water blankets - Supplementary warming.
  5. Heated humidification of inspired gases - Particularly relevant when supplemental O2 is delivered.
  6. Increase ambient OR temperature - Cold operating room is a major contributor.
  7. Avoid excessive surgical wound exposure - Limit the exposed wound area and duration.
  • Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 2295-2296

B. Pharmacological Management

1. Meperidine (Pethidine) - Traditional Gold Standard

  • Dose: 12.5-25 mg IV (small dose is often sufficient)
  • Mechanism: Meperidine has a unique antishivering effect among opioids - it disproportionately reduces the shivering threshold compared with other opioids. This is NOT mediated by the κ-opioid receptor (nalbuphine, a κ-agonist, lacks this effect). Current evidence suggests meperidine's antishivering action is mediated by agonist activity at the α2B-adrenoceptor.
  • Highly effective; long been considered the standard drug for treating established shivering.
  • Miller's Anesthesia, 10e, p. 2734

2. Dexmedetomidine - Currently Best Evidence

  • Dose: Small IV dose (typically 0.5 mcg/kg or lower)
  • Mechanism: α2-adrenoceptor agonism, central sympatholysis, thermoregulatory modulation
  • A 2025 Bayesian network meta-analysis of 20 RCTs (n=1983 patients undergoing caesarean section under neuraxial anaesthesia) found dexmedetomidine to be the top-ranked drug across ALL outcomes: shivering control (OR 38.1 vs placebo), fastest time to shivering control, lowest recurrence, and least maternal nausea. Evidence quality was moderate for dexmedetomidine.
  • Ferrea et al., J Clin Anesth 2025 [PMID: 39608094]

3. Tramadol

  • Dose: 0.5 mg/kg IV (35-220 mg range studied)
  • Mechanism: Weak opioid agonism + serotonin/noradrenaline reuptake inhibition
  • Suppressed shivering after epidural anaesthesia as effectively as meperidine 0.5 mg/kg in parturients
  • Ranked 2nd overall (OR 33.6 vs placebo) in the 2025 network meta-analysis. Evidence quality: low.
  • Miller's Anesthesia, 10e, p. 2734 | [PMID: 39608094]

4. Nalbuphine

  • Dose: Small IV dose
  • Mechanism: κ-opioid receptor agonism (though the precise antishivering mechanism differs from meperidine)
  • Ranked 3rd in the 2025 meta-analysis (OR 26.2 vs placebo). Evidence quality: moderate.
  • [PMID: 39608094]

5. Ondansetron

  • Dose: 4-8 mg IV
  • Mechanism: 5-HT3 receptor antagonism - interferes with serotonergic thermoregulatory pathways
  • Less effective than the opioid-based drugs (OR 6.6 vs placebo) but useful when opioids are undesirable (e.g., severe respiratory impairment)
  • [PMID: 39608094]

6. Clonidine

  • Dose: Small IV dose
  • Mechanism: Central α2 agonism, similar to dexmedetomidine but less potent
  • Lowest ranking in the meta-analysis among active agents (OR 3.2; CI crossed 1 - uncertain benefit). Evidence quality: low.
  • [PMID: 39608094]

7. Ketamine

  • Dose: 0.5 mg/kg at induction, followed by 0.3 mg/kg/h infusion
  • Specifically shown to prevent remifentanil-induced postanesthetic shivering, likely by blocking NMDA receptor-mediated acute opioid tolerance.
  • Miller's Anesthesia, 10e, p. 2734

8. Muscle Relaxant (last resort for intubated patients)

  • For intubated, mechanically ventilated, and sedated patients only, a small dose of neuromuscular blocking agent sufficient to stop the shivering may be used pending normothermia.
  • Morgan & Mikhail's Clinical Anesthesiology, 7e, p. 2435

Ranked Summary - Drug Efficacy (2025 Network Meta-Analysis, PMID 39608094)

RankDrugOR vs PlaceboEvidence Quality
1Dexmedetomidine38.1 (14.2-111.5)Moderate
2Tramadol33.6 (15.1-81.8)Low
3Nalbuphine26.2 (10.8-80.2)Moderate
4Meperidine20.9 (6.2-73.1)Low
5Ondansetron6.6 (2.2-23.2)Low
6Clonidine3.2 (0.6-14.9)Low (uncertain)

Differential Diagnosis - Exclude Other Causes

Before attributing shivering purely to hypothermia from spinal anaesthesia, the following must be excluded:
  • Bacteremia / Sepsis - rigors can mimic shivering
  • Drug allergy / anaphylaxis
  • Blood transfusion reaction
  • Malignant hyperthermia (rare; triggered by volatile agents / succinylcholine)

Practical Approach Summary

  1. Prevent first: Pre-warm the patient, use warmed IV fluids, forced-air warming blanket intraoperatively
  2. Monitor core temperature throughout the procedure
  3. Treat established shivering:
    • First choice (if no contraindication): meperidine 12.5-25 mg IV (rapidly effective, well-established)
    • Emerging preferred option based on current evidence: dexmedetomidine (best overall profile including less nausea)
    • Alternative: tramadol 0.5 mg/kg IV
  4. Active rewarming with forced-air warming device remains the definitive treatment of hypothermia itself
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