Negative Synacthen test during etomidate infusion

Therapeutic Strategies for the Treatment of Severe Cushing's Syndrome

Severe Cushing's syndrome presents an acute emergency and is defined by massively elevated random serum cortisol [more than 36 μg/dL (1000 nmol/L)] at any time or a 24-h urinary free cortisol more than fourfold the upper limit of normal and/or severe hypokalaemia (<3.0 mmol/L), along with the recent onset of one or more of the following: sepsis, opportunistic infection, intractable hypokalaemia, uncontrolled hypertension, heart failure, gastrointestinal haemorrhage, glucocorticoid-induced acute psychosis, progressive debilitating myopathy, thromboembolism or uncontrolled hyperglycaemia and ketocacidosis. Treatment focuses on the management of the severe metabolic disturbances followed by rapid resolution of the hypercortisolaemia, and subsequent confirmation of the cause. Emergency lowering of the elevated serum cortisol is most rapidly achieved with oral metyrapone and/or ketoconazole; if parenteral therapy is required then intravenous etomidate is rapidly effective in almost all cases, but all measures require careful supervision. The optimal order and combination of drugs to treat severe hypercortisolaemia-mostly in the context of ectopic ACTH-secreting syndrome, adrenocortical carcinoma or an ACTH-secreting pituitary adenoma (mainly macroadenomas)-is not yet established. Combination therapy may be useful not only to rapidly control cortisol excess but also to lower individual drug dosages and consequently the possibility of adverse effects. If medical treatments fail, bilateral adrenalectomy should be performed in the shortest possible time span to prevent the debilitating complications of uncontrolled hypercortisolaemia.

Current strategies for the treatment of severe Cushing's syndrome

Severe Cushing's syndrome may present an acute emergency in patients diagnosed with Cushing's syndrome with recent onset of at least one of the following: sepsis, opportunistic infection; intractable hypokalaemia, uncontrolled hypertension; heart failure; gastrointestinal hemorrhage; acute psychosis; progressive debilitating myopathy; thromboembolism; uncontrolled hyperglycemia and ketoacidosis. The biochemical definition includes serum cortisol ≥41μg/dl (1100 nmol/l) and/or severe hypokalemia (<3.0 mmol/l) or urine free cortisol fivefold the upper limit of normal. Treatment focuses on the management of severe metabolic disturbances followed by rapid resolution of the hypercortisolemia and subsequent confirmation of the cause. We emphasize the control of the hypokalemia, hypertension, diabetes and any psychotic state, anti-coagulation, monitoring and vigorous therapy of opportunistic infections. The ideal first-line therapies include metyrapone and ketoconazole, followed by parenteral etomidate; if all else fails life-saving bilateral adrenalectomy should be considered.

Etomidate--a review of robust evidence for its use in various clinical scenarios

Etomidate is an intravenous hypnotic with a favourable clinical profile in haemodynamic high-risk scenarios. Currently, there is an active debate about the clinical significance of the drug's side effects and its overall risk-benefit ratio. Etomidate-induced transient adrenocortical suppression is well documented and has been associated with increased mortality in sepsis. In surgical patients at risk of hypotensive complications, however, a review of current literature provides no robust evidence to contraindicate a single-bolus etomidate induction. Large randomised controlled trials as well as additional observational data are required to compare safety of etomidate and its alternatives.

Efficient short-term control of hypercortisolaemia by low-dose etomidate in severe paediatric Cushing's disease

BACKGROUND

Paediatric Cushing's disease (CD) is rare, but is associated with considerable morbidity and requires effective treatment. Control of hypercortisolaemia is recommended prior to definitive therapy by transsphenoidal pituitary surgery with selective adenomectomy. We describe a 6.2-year-old male with severe hypercortisolaemia and life-threatening complications of Cushing's disease. Control of cortisol with metyrapone and ketoconazole was ineffective, and due to his deteriorating condition, the decision was taken to proceed to bilateral adrenalectomy.

METHODS

Low-dose IV infusion of etomidate, with dose titration according to serum cortisol levels, was administered.

RESULTS

Etomidate infusion (3.0 mg/h i.v.) decreased serum cortisol from 1,250 to 250 nmol/l within 24 h. Combined etomidate and hydrocortisone therapy was maintained to provide stable serum cortisol levels within the desired range for 12 days prior to successful bilateral adrenalectomy.

CONCLUSION

In our experience, etomidate was effective and safe for short-term control of severe hypercortisolaemia in a severely ill child.

Should we use etomidate as an induction agent for endotracheal intubation in patients with septic shock?: a critical appraisal

Etomidate is commonly used for the facilitation of endotracheal intubation. While etomidate possesses multiple qualities that are beneficial in hemodynamically unstable patients who require a sedative or amnestic, its potential to negatively impact corticosteroid production is well-documented. Given the frequency of relative adrenal insufficiency observed in the critically ill and the increasing use of corticosteroids in patients with septic shock, an appraisal of the status of etomidate as an induction agent in patients with evolving or established septic shock is indicated. A review of the relevant literature suggests that its use in this setting may be harmful. It is proposed that, pending the performance of a randomized, controlled clinical trial, considerable caution should accompany its administration in patients with evolving or established septic shock. The potential role for concomitant empiric steroid replacement and the comparability of alternative induction regimens are also discussed.

Adrenocortical suppression and other endocrine effects of etomidate

(+/-) Etomidate is a short-acting general anaesthetic given by the intravenous route. It has strong adrenal suppression capability initially shown in the rat and then observed in man. At present, the drug seems the most effective adrenocortical inhibitor on a molar basis in vitro. 11 beta-hydroxylase is the most sensitive target enzyme; 16 alpha-, 17 alpha-hydroxylase and cholesterol side-chain cleavage are inhibited by higher concentrations. (+) Etomidate was more active than the (+/-) and far more than the (-) stereoisomer. Etomidate blood concentrations greatly exceed those needed to block adrenal steroidogenesis both when used inappropriately by infusion for long-term sedation (such previously unrecognized drug-induced adrenal suppression has often proved fatal in severely-injured patients) and also when given in very low doses as an induction anaesthetic. Reactive ACTH increase is currently observed. Etomidate, in vivo, does not appear to affect testicular steroidogenesis although it shares an imidazole moiety with fungicide phenylimidazoles endowed with such an action. However, testosterone production may be reduced by high concentrations in vitro. Other gonadal hormones seem unchanged. Both basal and stress-induced blood prolactin levels are lowered by etomidate in the rat but probably not in man arguably through interference at brain level where the GABA-benzodiazepine receptor complex could be directly involved. Hence, endocrine and neuroendocrine interferences are unique non-anaesthetic effects of etomidate.

In vitro effect of etomidate and thiopental on granulocyte migration

An increased mortality has been reported during long-term etomidate infusion. Inhibition of adrenal corticosteroid synthesis has been incriminated - but other factors related to host defence cannot be excluded. Using an under-agarose assay, we investigated the effect of etomidate on in vitro granulocyte migration. Unlike thiopental (50 micrograms/ml), etomidate (4-32 micrograms/ml) did not affect either spontaneous or directed migration. Impaired granulocyte migration is an unlikely cause of morbidity during long-term etomidate infusion.

Etomidate infusion and adrenocortical function. A study in elective surgery

The adrenocortical response to a short tetracosactrin (Synacthen) test was studied in 11 patients receiving either etomidate infusion or thiopentone infusion used to maintain anaesthesia for abdominal hysterectomy. Pethidine was used as the narcotic component. The results showed that etomidate infusion (median 28.5 ug/kg/min) completely blocked the adrenocortical response to corticotropin stimulation for at least 24 h after surgery. No suppression was found in patients receiving thiopentone infusion. It is concluded that etomidate cannot be recommended for routine induction and maintenance of anaesthesia.

CBF and CMRO2 during continuous etomidate infusion supplemented with N2O and fentanyl in patients with supratentorial cerebral tumour. A dose-response study

In 14 patients with supratentorial cerebral tumours with midline shift below 10 mm, CBF and CMRO2 were measured (Kety & Schmidt) during craniotomy. The anaesthesia was continuous etomidate infusion supplemented with nitrous oxide and fentanyl. The patients were divided into two groups. In Group 1 etomidate infusion of 30 micrograms kg-1 min-1 was used throughout the anaesthesia, and CBF and CMRO2 were measured twice. In this group CMRO2 (means +/- s.d.) averaged 2.31 +/- 0.43 ml O2 100 g-1 min-1 70 min after induction and 2.21 +/- 0.38 ml O2 100 g-1 min-1 130 min after induction. In Group 2 the etomidate infusion was increased from 30 to 60 micrograms kg-1 min-1 after the first study and a significant fall in CMRO2 from 2.52 +/- 0.56 to 1.76 +/- 0.40 ml O2 100 g-1 min-1 was found. Simultaneously, a significant fall in CBF was observed. The CO2 reactivity was preserved during anaesthesia.

Effects of etomidate on cortisol biosynthesis in isolated guinea-pig adrenal cells: comparison with metyrapone

The effects of the iv hypnotic etomidate on cortisol biosynthesis have been investigated in short term incubations of dispersed guinea-pig adrenal cells and were compared with those produced by metyrapone. Fifty percent inhibition of cortisol output was obtained at a final medium concentration of 3.5 10(-8) M (basal), 2.8 10(-8) M (ACTH-stimulated) for etomidate and of 5.10(-7) M (stimulated) for metyrapone. In the presence of etomidate, 11-deoxycortisol at 5.10(-8) M reached a peak value of 244 +/- 11% of control (mean +/- SE, n = 7). 17 alpha-Hydroxyprogesterone and progesterone were not significantly affected up to 10(-7) M, but at higher concentrations, all three precursors fell under their control values. Metyrapone induced a progressive rise of 11-deoxycortisol, from 10(-7) M upwards, to a maximum level at 10(-5) M (210 +/- 15% of control, mean +/- SE, n = 5). 17-Hydroxyprogesterone and progesterone concentrations were not significantly modified by metyrapone. The less active hypnotic L-enantiomer of etomidate had almost no inhibitory effect on cortisol production. The results obtained so far suggest that etomidate is a potent inhibitor of the mitochondrial cytochrome P-450 enzymes of the adrenal cortex, mainly the 11 beta-hydroxylase. At higher dose the cholesterol side-chain cleavage enzyme system seemed also to be affected.

Effects of etomidate on steroid biosynthesis in subcellular fractions of bovine adrenals

The imidazole derivative, etomidate, inhibits the 11 beta-hydroxylase in cell-free systems and mitochondria isolated from bovine adrenal cortex. Fifty per cent inhibition is achieved at 3.10(-7) M. The less active hypnotic L-enantiomer is also a less potent inhibitor of the 11-hydroxylation. At a 2 times higher concentration, etomidate affects the cholesterol side chain cleavage. The inhibition of both steroidogenic enzyme systems may be due to binding of the unhindered nitrogen of the imidazole ring of etomidate to the heme iron atom of the adrenal cortex mitochondrial cytochrome P-450 species.

Etomidate: a selective adrenocortical 11 beta-hydroxylase inhibitor

To investigate the adrenocortical suppression caused by the anesthetic etomidate, plasma levels of progesterone (P), 17-hydroxyprogesterone (17-OHP), 11-deoxycorticosterone (DOC), corticosterone (B), aldosterone (Aldo), 11-deoxycortisol (S), cortisol (F), and cortisone (E) were measured simultaneously before and after a short-term ACTH stimulation test in a 6.5-year-old boy whose convulsions could be kept under control only with constant etomidate infusions. During etomidate therapy, plasma levels of DOC and S were extremely elevated, the progestins P and 17-OHP were slightly elevated, whereas B and Aldo were in the lower normal range, and F and E were markedly decreased. A short-term ACTH stimulation test during etomidate infusion gave a blunted response of B, Aldo, F and E, whereas the level of DOC remained high and S even further increased. P and 17-OHP showed a positive response to ACTH. The ratios of B/DOC and F/S, which reflect adrenocortical 11 beta-hydroxylase activity, were extremely decreased during etomidate and did not change after ACTH stimulation. In contrast, the ratios of DOC/P and S/17-OHP, which reflect 21-hydroxylase activity, were elevated and remained elevated after ACTH stimulation. After discontinuation of etomidate therapy, all the baseline steroid levels were somewhat elevated, but responded normally to ACTH. These results demonstrate that etomidate causes a specific and reversible blockade of the 11 beta-hydroxylation of adrenal steroid synthesis.

The inhibition by etomidate of the 11 beta-hydroxylation of cortisol

The effect of a sleep-dose of etomidate on the plasma concentrations of cortisol, 11-deoxycortisol and 17 alpha OH-progesterone was investigated in eight patients; two other patients received thiopentone. Blood samples were collected at 0, 15 and 30 min after etomidate or thiopentone when an injection of tetracosactrin was given and a final sample was collected at 60 min. The plasma cortisol response to tetracosactrin was depressed below normal in patients given etomidate, and the 11-deoxycortisol response was very high, ranging from 36.4 to 184.7 nmol/l. The two patients that received thiopentone had a normal response to all steroids. The identity of the plasma 11-deoxycortisol in two patients was confirmed by high-performance liquid chromatographic separation and quantification by both spectrophotometric and radioimmunoassay measurements. These results suggest that a single dose of etomidate inhibits 11 beta-hydroxylation of cortisol.