Ketamine contraindications

Barbiturates may precipitate episodes of acute intermittent porphyria (AIP) and their use is contraindicated in patients who are predisposed to this condition. Some animal models indicate that ketamine, etomidate, and the benzodiazepines may be porphyrinogenic and propofol is considered to be the intravenous anaesthetic of choice in AlP-prone patients. 

Ketamine has been traditionally contraindicated in patients with increased ICP or reduced cerebral compliance because it increases CMR02, CBF and ICP. These deleterious effects can be antagonised by the concomitant administration of propofol, or thiopentone, and benzodiazepines. Furthermore, ketamine is an antagonist at the NMDA receptor. Nevertheless, ketamine can adversely affect neurological outcome in the presence of brain ischaemia. 

If a (3-adrenoceptor antagonist is administered prior to sufficient ol-radrenoceptor blockade, a hypertensive episode may be precipitated with cardiac failure and pulmonary oedema. Most intravenous anaesthetic agents have been used safely, but ketamine is contraindicated. Sodium nitroprusside can be used to achieve arteriolar dilation. Esmolol, a pi-selective antagonist with very short duration of action, is administered intravenously to prevent cardiac arrhythmias intra-operatively. After tumour removal, volume administration should be aggressive to maintain haemodynamic stability, and a noradrenaline infusion may be required. 

Use in pregnancy. Ketamine is contraindicated in pregnancy before term, since it has oxytocic activity. It is also contraindicated in patients with eclampsia or pre-eclampsia. It may be used for assisted vaginal delivery by an experienced anaesthetist. Ketamine is better suited for use during caesarean section it causes less fetal and neonatal depression than other anaesthetics. 

Unlike other parenteral anesthetics, ketamine increases cerebral blood flow and ICP with minimal alteration of cerebral metabolism. These effects can be attenuated by concurrent administration of thiopental and/or benzodiazepines along with hyperventilation. However, given that other anesthetics actually reduce ICP and cerebral metabohsm, ketamine is relatively contraindicated for patients with increased ICP or those at risk for cerebral ischemia. The effects of ketamine on seizure activity are mixed. Emergence dehrium characterized by hallucinations is a frequent comphcation of ketamine that can result in serious patient dissatisfaction and can complicate postoperative management. Delirium is most frequent in the first hour after emergence and appear to occur less frequently in children benzodiazepines reduce the incidence of emergence delirium. 

IV. Rapid distribution, short duration (15 min). T oral secretions, nightmares, hallucinations (schizophrenia is a contraindication). Consider ketamine when elevated heart rate is desired and in asthmatics. 

The only absolute contraindication is use in patients who have a hypersensitivity or allergy to ketamine products. 

Ketamine and morphine are contraindicated in strychnine-intoxicated anfrnab. 

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