1. Introduction
hypotension, shivering, Shivering, hypothermia
HEAT, LACTIC ACIDOSIS
Shivering is described as an involuntary, repetitive activity of skeletal muscles. It is activated when behavioral compensation and maximal vasoconstriction are insufficient to maintain core temperature.It is important for anesthesiologists to recognize and treat perioperative shivering and to prevent it, if possible, as shivering can have deleterious effects on anesthetized patients. Shivering can increase intraocular and intracranial pressure, oxygen consumption by 300% to 400%, carbon dioxide production, catecholamine release, metabolic heat production by up to 600%, metabolic rate by up to 400%, and lactic acidosis.Perioperative hypothermia is defined as a core temperature of <33 to 35 °C, whereas the shivering threshold in non-anesthetized patients is 35.5 °C. Central neuraxial anesthesia impairs both central and peripheral thermoregulation as it increases the inter-threshold range by increasing the sweating threshold and decreasing the vasoconstriction threshold and shivering threshold (triggering core temperature) by approximately 0.5 to 0.6℃.Phenylephrine is an alpha-1 adrenergic receptor agonist with minimal to no beta-adrenergic activity. Therefore, it is mainly used intraoperatively to treat hypotension.