Effect of dexmedetomidine on the release of [3H]-noradrenaline from rat kidney cortex slices: characterization of alpha2-adrenoceptor.

The presynaptic modulation of [3H]-noradrenaline (NA) release from rat kidney cortex slices, a method used for the first time, was investigated. Rat kidney cortex slices were loaded with [3H]-NA and the release of radioactivity at rest and in response to field stimulation was determined. The alpha(2)-adrenoceptor agonist, dexmedetomidine inhibited the stimulation-evoked release of NA from kidney slices in a concentration-dependent manner, whereas alpha(2)-adrenoceptor antagonist CH-38083 (7,8-methyenedioxy-14-alpha-hydroxyalloberbane HCl), an alpha(2)-adrenoceptor antagonists, enhanced it. When dexmedetomidine and BRL-44408, a selective alpha(2A) antagonist, were added together, the effect of dexmedetomidine was significantly antagonized. In contrast, ARC-239 (2-(2,4-(o-piperazine-1-yl)-ethyl-4,4-dimethyl-1,3-(2H, 4H)disoguinolinedione chloride), a selective alpha(2B)-antagonist, had no effect on the release and failed to prevent the effect of dexmedetomidine. Prazosin, an alpha(1)- and alpha(2B/C)-adrenoceptor antagonist enhanced the release evoked by field stimulation. It is therefore suggested that there is a negative feedback modulation of NA release at the sympathetic innervation of kidney cortex, and dexmedetomidine, a clinically used anesthetic adjunct inhibits the release via activation of alpha(2C)-adrenoceptors.

[Anesthetic management of cesarean section for a patient with idiopathic thrombocytopenic purpura].

A 39-year-old parturient with idiopathic thrombocytopenic purpura (ITP) was scheduled for cesarean section at 37 weeks gestation. ITP, diagnosed during the first pregnancy, recurred during the second pregnancy, and she was treated with high dose gamma-globulin and platelets transfusion to increase her platelets count over 5.0 x 10(4) x microliter-1 before cesarean section. During the operation under general anesthesia with propofol and pentazocin, atonic hemorrhage occurred gradually with increasing blood loss after the parturition. Since administration of oxytocin, ergometrine maleate, and prostaglandin E1 could not improve the uterine contraction, the hysterectomy was performed to control massive bleeding (finally 8200 g). Packed red cells (22 units) and platelets (40 units) were transfused and fresh frozen plasma (28 units) was infused during anesthesia. Management of ITP during pregnancy is important to prevent hemorrhagic complications because of a narrow safety margin of parturient and fetus.

[The effect of sevoflurane and enflurane on renal sympathetic nerve activity in sinoaortic denerved rabbits].

We assessed the effects of sevoflurane and enflurane, i.e. halogenated volatile anesthetics, on blood pressure, heart rate, and renal sympathetic nerve activity (RSNA) in rabbits. To eliminate the influence of baroreceptor reflex, bilateral carotid sinus nerve branches and vagus nerves were resected before the measurements. Sevoflurane and enflurane [0.5-1.15 MAC (minimum alveolar anesthetic concentration)] did not significantly change heart rate, but decreased mean blood pressure in a concentration-dependent manner. On the other hand, while sevoflurane did not significantly attenuate RSNA, enflurane decreased it in a concentration-dependent manner. There was a significant difference between sevoflurane and enflurane in their effects on RSNA. These results suggest that a decrease in blood pressure caused by sevoflurane is related to factors other than sympathetic nerve activity, and that hypotension caused by enflurane is related more closely to attenuated activity of sympathetic nerve, at least, in comparison with sevoflurane.

[The effect of sevoflurane and isoflurane on striatal dopamine of awake freely moving rats observed in an in vivo microdialysis study].

We investigated the effect of sevoflurane and isoflurane on the level of interstitial dopamine of in vivo awake, free moving rats brain striatum using microdialysis techniques. Rats were implanted with a microdialysis probe to the right striatum of the brain and administered with 1.2 MAC of each volatile anesthetics for 1 hour, and dialysates from the probe were determined every 20 minutes. Both anesthetics reduced the amount of dopamine derived from dialysate, and increased the efflux of dopamine with pretreatment of nomifensine 10mg. kg-1 i.p. The change of metabolites of dopamine during anesthesia was increased. No significant difference was found between sevoflurane and isoflurane. We hypothesized that these anesthetics might have special actions on interactions between metabolism and re-uptake of dopamine in rats striatum during anesthesia.

Minimum alveolar concentration of sevoflurane that blocks the adrenergic response to surgical incision in women: MACBAR.

We have investigated the cardiovascular and plasma noradrenaline response to surgical incision under sevoflurane anaesthesia and determined the end-tidal concentration of sevoflurane that blocks the adrenergic response or responses to surgical incision (MACBAR) and changes in mean arterial pressure (MAP) in response to surgical incision (MACBCR) in 50% of women. We randomly assigned 64 female patients, aged 20-49 years, to eight groups according to end-tidal sevoflurane concentration: 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0% and 8.5%. All patients received only sevoflurane anaesthesia. An increase of 10% or more from prestress (incision) values of MAP or plasma noradrenaline concentration was considered a positive response. The probability of no response to stress was analysed using logistic regression to obtain the probability of no response vs. end-tidal sevoflurane concentration and the best-fit curve from the maximum likelihood estimators of the model parametes. MACBAR (mean +/- SE) was 8.0 +/- 0.2%, MACBCR was 7.9 +/- 0.2%. However, such high doses of sevoflurane cannot be used clinically because of their high toxicity. It may be preferable to combine sevoflurane with other anaesthetics to reduce haemodynamic responses to strong stimulation.

Minimum alveolar concentration of sevoflurane for tracheal extubation in children.

BACKGROUND: One advantage of tracheal extubation during deep anaesthesia is that respiratory complications are reduced. Sevoflurane is a suitable anaesthetic agent for children. This study was conducted to determine the minimum alveolar concentration of sevoflurane required to prevent cough or movement during and after tracheal extubation (MACextubation). METHODS: We studied 30 nonpremedicated children, aged 2-10 yr, undergoing plastic surgery. They were allocated randomly to five groups (end-tidal sevoflurane concentrations: 2.0, 2.5, 3.0, 3.5, 4.0%). After surgery, 60% nitrous oxide was discontinued and the target concentration of sevoflurane was maintained for at least 10 min in 100% oxygen, then the trachea was extubated to determine MACextubation. Logistic regression was used to estimate MACextubation of sevoflurane. RESULTS: MACextubation was 2.3 (0.2; standard error)% (95% confidence limits: 1.2% and 2.7%). CONCLUSIONS: Tracheal extubation in 50% of anaesthetized children age 2-10 yr may be accomplished without coughing or moving at 2.3% end-tidal concentration of sevoflurane.

[Rhabdomyolysis induced by succinylcholine chloride and sevoflurane in an elderly man].

An 81-year-old man was scheduled for cervical lymph node biopsy. His laboratory data were within normal ranges. After induction of anesthesia with thiopental 175 mg and succinylcholine chloride (SCC) 40 mg, moderate masseter spasm was observed. Anesthesia was maintained with nitrous oxide, oxygen and sevoflurane. After the operation he had severe muscle pain and CK was elevated up to 81,400IU.l-1. The body temperature was not elevated above 37.2 degrees C during and after the operation. The skinned fiber examination, performed one month later, showed his calcium-induced-calcium-release (CICR) to be within normal ranges. We diagnosed him as rhabdomyolysis induced by coadministration of SCC and sevoflurane, especially SCC. We concluded that even in an elderly man, SCC should be administered cautiously.

Hypopituitarism associated with Cogan's syndrome; high-dose glucocorticoid therapy reverses pituitary swelling.

A 70-year-old woman with Cogan's syndrome first presented with central diabetes insipidus and then developed secondary hypothyroidism. Magnetic resonance imaging revealed a diffuse pituitary swelling without evidence of tumor. High-dose glucocorticoid therapy administered to treat Cogan's syndrome was very effective in suppressing the inflammatory process, and resulted in the reversal of the pituitary swelling and partial recovery of thyroid stimulating hormone secretion. This is the first case of hypopituitarism associated with Cogan's syndrome, a form of autoimmune vasculitis. The glucocorticoid-responsive pituitary lesion is best explained by autoimmune hypophysitis which shows pituitary swelling and is known to often associate with other autoimmune phenomena.