Ketamine in ambulatory anesthesia: dose-dependent effects on breathing and cortical function

Ketamine was introduced into medical practice in 1965 and is widely utilized to provide sedation and analgesia. Low-dose ketamine can be used in ambulatory surgery following an assessment of risks and benefits.

Ketamine is an N-methyl-D-aspartate receptor antagonist that decreases the firing rate of fast-spiking gamma-aminobutyric acidergic interneurons, leading to a disinhibition of pyramidal neurons and enhanced cortical and respiratory arousal. The consequences are an activation of the sympathetic nerve system and an increased drive to upper airway dilator and respiratory pump muscles. In parallel, low-dose ketamine has effects on cortical function which can be beneficial: delirium and posttraumatic stress disorder prevention through relief of pain and discomfort, and mood stabilization. However, higher doses increase airway secretions, predispose to laryngospasm, and desaturation. When given to anxious patients without concomitant use of benzodiazepines, ketamine increases the risk of frightening and delusional memories.

Low dose of intravenous ketamine (<0.5 mg/kg) expresses excellent analgesia, improves breathing and circulation, and stabilizes mood, which can help prevent postoperative delirium. Ketamine carries the risk of frightening and delusional memories, when given to anxious patients in the absence of concomitant premedications (eg, midazolam 0.03 mg/kg). Higher doses of ketamine increase the risk of respiratory complications.