Screening of certain anaesthetic agents for their ability to elicit acute porphyric phases in susceptible patients

A review of etomidate for rapid sequence intubation in the emergency department

Currently, there is no one drug that is the agent of choice for induction in rapid sequence intubation in the emergency department (ED). All agents currently used as induction agents in the ED offer distinct advantages for various clinical conditions, but each has a significant side effect profile and specific contraindications that limit its use in many common clinical settings. A review of the data available from the anesthesia literature suggests that etomidate possesses many properties that may make it the agent of choice for rapid sequence intubations in the ED. These advantages include excellent pharmacodynamics, protection from myocardial and cerebral ischemia, minimal histamine release, and a hemodynamic profile that is uniquely stable. Disadvantages include a lack of blunting of sympathetic response to intubation, a high incidence of myoclonus, prominent nausea and vomiting, potential activation of seizures in patients with epileptogenic foci, and impaired glucocorticoid response to stress. Further studies are needed to evaluate the advantages and disadvantages of the use of etomidate for rapid sequence intubation in the ED.

Elevated porphyrins following propofol anaesthesia in acute intermittent porphyria

A patient with acute intermittent porphyria was anaesthetised with propofol for a minor orthopaedic procedure. Postoperative urinary porphyrins were markedly raised compared to pre-operative values, although the patient remained clinically well. Caution should continue to be exercised when propofol is used in patients with acute porphyrias.

Acute intermittent porphyria and caesarean delivery

A 29-yr-old patient was diagnosed with acute intermittent porphyria (AIP) during pregnancy. She had a Caesarean section under lidocaine/fentanyl epidural blockade. Because of inadequate analgesia, general anaesthesia was induced with propofol. Postoperatively urinary porphobilinogen excretion (625 mumol.day-1) exceeded the upper limit of normal but no symptoms of porphyria developed. In anecdotal clinical reports and in a previously described rat model of porphyria, propofol was found to be safe. This is the first reported use of propofol in a pregnant porphyric patient. Anaesthetic drug safety in porphyria is reviewed and the choice of induction agent discussed. Data on which to base these decisions is limited but we conclude that propofol may be suitable for use in patients with porphyria.

[Anesthesia and hepatic porphyria]

Three of the acute hepatic porphyrias, acute intermittent porphyria, variegata porphyria and hereditary coproporphyria, are characterized by an idiosyncratic reaction to many common drugs; the resulting excessive excretion of porphyrin precursors is responsible for episodes of acute neurological dysfunction. This review aimed to focus the attention of the anaesthesiologist on the porphyrinogenic properties of all the drugs used in anaesthesia and intensive care. An outline of the chemistry of porphyrins and the enzymatic pathways were recalled, so as to place the acute porphyrias in their proper perspective. There follows a reminder of the clinical aspect of acute porphyric crises. The part played by drugs is then assessed from clinical and laboratory data concerning their porphyrinogenicity. Those drugs for which there is conflicting evidence regarding their safe use in porphyric patients are discussed: propofol, ketamine, benzodiazepines, etomidate, local anaesthetics. Recommendations supported by clinical and experimental data are given, especially the results obtained with the chick embryo liver model. Treatment of the acute crisis is provided, with particular emphasis on the use of haematin. The anaesthetic management of hepatic porphyric patients is described. Those drugs which are well-known porphyrinogenic compounds in the chick embryo liver must be excluded from use for anaesthesia in the porphyric patients, even if they have been observed to be innocuous in rare cases of asymptomatic patients. Finally, recommendations for anaesthesia in symptomatic cutanea porphyria are given.

Is propofol a safe agent in porphyria?

A case is presented of the use of a propofol infusion for anaesthesia in a patient with known variegate porphyria. Urinary screening for porphyrins demonstrated a marked increase after this anaesthetic, but there were no clinical symptoms.

Induction of anaesthesia with ketamine during an acute crisis of hereditary coproporphyria

An appendectomy operation was undertaken in a 29-year-old patient with signs of an acute crisis of hereditary coproporphyria. Anaesthetic induction with ketamine 75 mg IV was uneventful. The safety of ketamine in patients with coproporphyria is discussed.