What are the causes of shivering in patients?

Causes of Shivering in Patients

Shivering in patients is primarily caused by hypothermia, infection, pain, medication effects, and neurological responses to temperature regulation, with hypothermia being the most common trigger through activation of the preoptic region of the hypothalamus when core temperatures fall below 35.5-36°C. 1, 2

Physiological Causes

• Thermoregulatory Response to Hypothermia: Shivering is triggered when core temperatures fall below a set threshold (usually 35.5–36°C), activating the preoptic region of the hypothalamus 1
• Metabolic Response: Shivering is an involuntary oscillatory activity of skeletal muscles that facilitates thermoregulation, but at the cost of higher metabolic expenditures 1
• Increased Oxygen Demand: Shivering can double the metabolic rate in patients with high muscle mass and nearly triple oxygen consumption 1
• Redistribution of Heat: Delayed hypothermia due to redistribution of heat from the core to the periphery can cause shivering even after the immediate perioperative period 2

Pathological Causes

• Infection: A spike in temperature with associated shivering is often an early sign of infection, particularly respiratory and wound infections 1, 2
• Sepsis: Shivering with temperature ≥38.0°C may indicate developing sepsis requiring prompt evaluation 2
• Pain: Inadequate pain control can manifest as shivering, particularly in postoperative patients 2, 3
• Acute Opioid Withdrawal: Especially with the use of short-acting narcotics, withdrawal can trigger shivering 3

Situational/Iatrogenic Causes

• Post-Cardiac Arrest: Shivering is common during targeted temperature management (TTM), particularly during the induction phase 1
• Postoperative Setting: Common after surgery due to exposure to cool operating rooms, administration of unwarmed fluids, and anesthetic agents 3, 4
• Post-Anesthesia: Both general and spinal anesthesia can cause shivering due to thermoregulatory disruption 5, 6
• Medication Reduction: Decreasing sedative medications that were previously suppressing shivering response 2
• Medication Side Effects: Certain medications can affect thermoregulatory control 2

Risk Factors for Shivering

• Age: Younger patients are at higher risk for postoperative shivering 7
• Type of Surgery: Endoprosthetic surgery carries higher risk 7
• Core Hypothermia: Lower core temperature significantly increases shivering risk 7
• Lower Skin Temperature: Even with normal core temperature, lower skin temperature predicts shivering 4
• Hemodynamic Instability: Patients requiring vasodilators like nitroprusside may be more prone to shivering 4
• Inadequate Intraoperative Warming: Failure to maintain normothermia during surgery 2
• Prolonged Surgical Exposure: Extended surgical time increases risk 2

Neurological Factors

• Brain Injury Severity: The degree of shivering can be influenced by the severity of brain injury, with potentially less shivering in more severe brain injury 1
• Altered Hypothalamic Function: Following hypoxic-ischemic injury, the temperature threshold for shivering can be lower 1
• Sickle Cell Disease: Patients with sickle cell disease are particularly vulnerable as shivering can lead to sickling crisis 1, 2

Metabolic Consequences

• Bioenergetic Failure: Shivering-induced elevated metabolic expenditure can trigger bioenergetic failure with demand cerebral ischemia 1
• Energy Mismatch: Significant mismatch in energy supply and demand to the brain can occur during shivering 1
• Lactic Acidosis: Increased muscle activity during shivering can induce lactic acidosis 3
• Catecholamine Release: Shivering triggers release of catecholamines, potentially worsening hemodynamic instability 3

Understanding these diverse causes of shivering is essential for proper diagnosis and management, especially in critically ill patients where shivering can significantly impact outcomes by increasing metabolic demand when the body is least equipped to handle it 1.