General anaesthetics General anaesthetics are volatile agents intended to produce loss of consciousness and can cause additive CNS depressant effects with drugs having this effect (e.g. opioid analgesics or antiemetics administered postoperatively). Patients undergoing day-case surgery should be warned about this effect (and should be warned to avoid alcohol for at least 24 hours). General anaesthetics have negative inotropic and/or vasodilating properties that may lead to hypotension, likely to be exacerbated by the co-administration of other drugs with hypotensive effects. They are also likely to increase risk of arrhythmias (due to inherent Q-T prolongation effects and sensitization of the myocardium to circulating catecholamines).