Ketamine is a NMDA antagonist in the CNS. By inhibiting NMDA receptors in inhibitiory neurons in the brain, it causes increased CNS activity and sympathomimetic effects. As a result, there is not only an anaesthetic effect, but also activation of the CNS unlike other anaesthetics. This is beneficial in surgical settings because it maintains blood pressure, airway reflexes, bronchioles remain dilated and airways patent. Making this a particularly useful drug in shock and surgery patients because of blood pressure maintained with ketamine use, unlike typical anaesthetics which cause decreased BP and respiratory suppression.