Abstract

Shivering is a frequently encountered perioperative complication in patients undergoing spinal anesthesia. Numerous different pharmacological agents have been employed to mitigate this issue. This scoping review aims to evaluate the efficacy of ketamine in mitigating the incidence of shivering. This review process utilized PubMed, JAMA, and Cochrane as primary databases. Searches were performed using combinations of key terms: “Ketamine,” “Shivering,” “Spinal Anesthesia,” and “Hypothermia.” Reviews of reference lists for additional pertinent data were performed. When ketamine was compared against a saline control, three out of five studies found ketamine to be more effective (p < 0.05, p < 0.001, p < 0.001) in the prevention of shivering. When compared with tramadol, two studies found ketamine to be more effective (p < 0.001, p < 0.001), one found no difference (p = 0.261), and one found tramadol to be more effective (p < 0.001). Two studies found dexmedetomidine more effective (p < 0.022, p < 0.027) than ketamine and tramadol. When comparing ketamine, ondansetron, and meperidine, all three were effective (p < 0.001) versus saline, with no significant difference between the three. Meperidine demonstrated more efficacy (p < 0.05) in reducing the intensity of shivering than ketamine. Ketamine’s effects on hemodynamics were shown to be equivocal or more favorable across several studies. While there is mixed evidence on whether it is better than other treatments, ketamine may have advantages from a hemodynamic standpoint. Dosages of 0.2-0.5 mg/kg with or without a subsequent infusion of 0.1 mg/kg per hour may aid in the prevention of perioperative shivering. Overall, ketamine is a safe and effective drug for the prevention of perioperative shivering. However, other drugs may be equally or more effective; therefore, patient population, hemodynamic status, patient preferences, and provider familiarity with different agents should be considered.

Introduction & Background

Shivering is an involuntary somatic muscle response typically triggered by prolonged exposure to cold environments or fever to raise body temperature by generating heat through repetitive contraction of skeletal muscles. Shivering is primarily controlled by the median preoptic nucleus (MnPO) in the anterior thalamus of the brain which contains the central efferent pathways for cold-defensive and febrile shivering. Some common causes of shivering include movement disorders, excitement, fear, stress, tremors, low blood sugar, anxiety, fever, cold exposure, postanesthetic shivering, and shivering with spinal anesthesia.

Patients frequently experience shivering following surgery with general or spinal anesthesia. This shivering may be due to a natural thermoregulatory response to central hypothermia or as a result of the release of cytokines throughout the surgical process [1]. This is unpleasant for the patient and occurs following surgery in 30-65% of patients who have received general anesthetics [1].

The exact mechanism underlying post-spinal anesthesia shivering is not fully understood but may involve thermoregulatory responses to hypothermia, affecting neurons in specific brain regions. Shivering with spinal anesthesia is an involuntary, oscillatory muscular activity that significantly increases metabolic heat production by up to 600% and increases oxygen consumption up to 400% [2]. This may lead to arterial hypoxia and is associated with an increased risk to patients with myocardial infarction [1]. These sequelae of shivering may prolong post-operative recovery time and contribute to poor patient outcomes.

A variety of medications have been studied to prevent or treat post-anesthesia shivering; recent studies indicate ketamine shows promise in controlling shivering. Ketamine is a competitive N-methyl-D-aspartate (NMDA) receptor antagonist and is involved in the regulation of heat. As a NMDA agonist, it increases the rate of neuronal discharge in the anterior hypothalamic preoptic region modulating serotonergic and noradrenergic neurons in the locus coeruleus [3]. The mechanism of action by which ketamine controls shivering has yet to be determined, but it is believed that it regulates shivering by producing non-vibration-induced heat, acting on the hypothalamus and beta-adrenergic effects.

As there is not yet a determined most effective agent this scoping review of current literature was conducted to determine the benefits of ketamine in the prevention of perioperative spinal anesthetic shivering. Hemodynamic effects of ketamine and other anesthetic agents were examined as a secondary objective.