What are the causes of shivering in admitted patients?

Causes of Shivering in Admitted Patients

Shivering in admitted patients is most commonly caused by hypothermia, infection, pain, medication effects, or as a physiological response during targeted temperature management, with each cause requiring specific identification and management. 1

Physiological Causes

• Thermoregulatory response to hypothermia is the most common cause, triggered when core temperatures fall below a threshold (usually 35.5–36°C), activating the preoptic region of the hypothalamus 1
• Shivering is an involuntary oscillatory activity of skeletal muscles that can double the metabolic rate in patients with high muscle mass and nearly triple oxygen consumption 1
• This increased metabolic expenditure can create a significant mismatch in energy supply and demand to the brain, potentially leading to bioenergetic failure 1

Pathological Causes

• Infection is a major cause of shivering in admitted patients, particularly:
  • Respiratory infections 1, 2
  • Wound infections 1, 2
  • Early sepsis (often accompanied by temperature ≥38.0°C) 1
• Pain, especially inadequately controlled postoperative pain, can manifest as shivering 2
• Neurological factors affecting shivering include:
  • Severity of brain injury (potentially less shivering in more severe brain injury) 1
  • Altered hypothalamic function following hypoxic-ischemic injury 1

Iatrogenic/Situational Causes

• Post-cardiac arrest patients undergoing targeted temperature management (TTM) commonly experience shivering, particularly during the induction phase 1
• Medication-related causes include:
  • Reduction in sedative medications that were previously suppressing shivering response 1, 2
  • Medication interactions affecting thermoregulatory control 2
  • Acute opioid withdrawal, especially with short-acting narcotics 3
• Perioperative factors:
  • Inadequate intraoperative warming 1, 2
  • Prolonged surgical exposure 1, 2
  • Redistribution of heat from core to periphery (can occur even on day 2 post-surgery) 2

Risk Factors for Shivering

• Young age is the most important risk factor for postoperative shivering 4
• Endoprosthetic surgery 4
• Core hypothermia 4
• Decreased body surface area 5
• Male gender 5
• Patients with sickle cell disease are particularly vulnerable, as shivering can lead to sickling crisis 1

Clinical Implications

• Shivering increases oxygen consumption and the risk of hypoxemia 3
• It can induce lactic acidosis and catecholamine release 3
• In post-cardiac arrest patients, shivering can mitigate the potential benefits of temperature control if left unchecked 6
• Shivering is one of the leading causes of discomfort for postsurgical patients 3
• In patients with brain injury, shivering-induced elevated metabolic expenditure can trigger bioenergetic failure with demand cerebral ischemia 1

Evaluation Approach

• Measuring core temperature is essential to differentiate between hypothermic and normothermic shivering 2
• Assessment for signs of infection should include:
  • Checking wound sites and respiratory status 2
  • Evaluating intravenous cannula sites for phlebitis 2
  • Checking for symptoms of sepsis if temperature ≥38.0°C 2
• Monitor vital signs, as mean arterial blood pressure is significantly higher in hypothermic patients, and heart rate is significantly higher in shivering patients 7

Common Pitfalls and Caveats

• Shivering is not always thermoregulatory, even though it's traditionally attributed to hypothermia 7
• Shivering can occur even in normothermic patients during the perioperative period 3
• The etiology of shivering is still insufficiently understood, making treatment sometimes empirical 3
• Severe complications of shivering are rare but can occur due to increased oxygen consumption 8
• Patients with neuraxial anesthesia may experience delayed shivering as the block wears off 2