Keita Suekane

Effect of Sevoflurane on Hypoxic Pulmonary Vasoconstriction in the Perfused Rabbit Lung

BackgroundIn vitro studies have shown that isoflurane, enflurane, and halothane Inhibit the hypoxic pulmonary vasoconstriction (HPV) with essentially the same potency. The aim of this study is to compare the effects of Sevoflurane and Isoflurane on HPV in constant-flow perfused rabbit lungs. MethodsConstant-flow perfused lungs from Japanese white rabbits were tested. The lungs were divided into three groups: isoflurane alone (n = 6), Sevoflurane alone (n = 6), and sevoflurane with ibuprofen pretreatment (n = 6). Baseline HPV responses were measured as the pulmonary arterial pressure Increased after changing inspired oxygen concentration from 95% for 15 min to 3% (with 5% CO2) for 5 min without anesthetic administration. Next, three different concentrations of anesthetics were added to the inspired gas for 15 min in random order. The HPV response in the presence of anesthetic was expressed as a percentage of the pressor response in the absence of anesthetics, and dose-response relationships were calculated using the nonlinear least-squares method. ResultsIsoflurane and Sevoflurane both depressed the HPV response in a dose-related manner. The half-inhibition values (ED50) of HPV with isoflurane and Sevoflurane were 0.85 ± 0.22 MAC and 1.00 ± 0.12 MAC (mean ± SD), respectively, and were not statistically different. Ibuprofen pretreatment did not alter ED50 and slope of dose-response curve, although the absolute value of pressor response in the sevoflurane group with ibuprofen pretreatment was greater than that in the sevoflurane alone group at every concentration of sevoflurane. ConclusionsSevoflurane inhibits the HPV response in a dose-related manner, and its potency is similar to that of isoflurane in vitro. Cyclooxygenase products do not mediate the inhibition of HPV by sevoflurane.

Suppressant effects of midazolam on responses of spinal dorsal horn neurones in rabbits.

Recordings of noxious intra-arterial bradykinin (BK)-induced chemonociceptive and spontaneous activity from 30 single spinal lamina V neurones of the dorsal horns in non-anaesthetized and decerebrated rabbits, were performed with tungsten microelectrodes. Intravenous injection of midazolam (0.2 mg/kg; 7 neurones) depressed BK-induced neural discharges by 55.0 +/- 6.2% (P less than 0.05) and 57.9 +/- 8.4% (P less than 0.05) 5 and 25 min after administration, respectively. Treatment with flumazenil (0.2 mg/kg, i.v.; 7 neurones), administered 20 min after midazolam, completely reversed the inhibition by midazolam of the BK-induced spinal lamina V neural responses and spontaneous neuronal activity. In contrast, a large dose of naloxone (1.0 mg/kg, i.v.; 6 neurones), administered 20 min after midazolam, failed to alter the midazolam-induced depressant effects on the nociceptive responses, at the spinal dorsal horn. Treatments with flumazenil (5 neurones) and naloxone (5 neurones) did not influence either the spontaneous or the BK-induced neuronal discharges, recorded in spinal lamina V cells. Midazolam depressed the nociceptive responses probably through its agonistic activity on the binding to the GABA-benzodiazepine-barbiturate system in the spinal dorsal horn.

Naloxone and flumazenil fail to antagonize the isoflurane-induced suppression of dorsal horn neurons in cats.

Effects of naloxone and flumazenil on isoflurane activities were examined on dorsal horn neurons in cats. Isoflurane suppressed bradykinin-induced nociceptive responses in transected feline spinal cords. The bradykinin-induced neuronal firing rates were significantly suppressed by 60.0%, 35.3% and 32.2% at 10, 20 and 30 min after isoflurane administration, respectively. The 32.2% suppression on bradykinin-induced neuronal responses at 30 min after isoflurane administration was not reversed 5 min after administration of naloxone (36.4% suppression). The suppressive effects of isoflurane were not reversed by naloxone (0.2 mg·kg−1, i.v. Similarly, the benzodiazepine antagonist, flumazenil (0.2 mg·kg−1 i.v., did not affect the suppressive effects of isoflurane. Failure of naloxone and flumazenil to reverse the suppressive effects of isoflurane suggests that isoflurane interacts with neither opioid nor benzodiazepine receptors in producing its suppressive action on nociceptive responses in dorsal horn neurons of the feline spinal cord.

The Influence of Volatile Anesthetics on Portwine Stain

To examine the relationship between volatile inhalation anesthetics and the fading of portwine stain (PWS), the study retrospectively investigated the incidence of termination of pulsed dye laser treatment vis-à-vis PWS fade during use of a general inhalation anesthetic in 107 infants and children with facial PWS. The fading of PWS is disadvantageous to the pulsed dye laser treatment. All patients received pulsed dye laser treatment under general anesthesia using one of four kinds of volatile inhalation anesthetics (halothane, enflurane, isoflurane, and sevoflurane). Two hours before the induction of anesthesia, all patients were rectally irrigated. Treatment was discontinued in none of the 44 patients in the halothane group or the 7 patients in the enflurane group; in one of the 29 in the isoflurane group; and in 10 of the 27 patients in the sevoflurane group. The sevoflurane group showed a significantly (P < 0.01) higher incidence of PWS fading. Thus, when using a volatile inhalation anesthetic in combination with pulsed dye laser treatment for PWS, caution should be exercised if sevoflurane is selected, as PWS fading is harmful to the pulsed dye laser.

Suppressive action of enflurane on dorsal horn neurons in rabbits

The neurophysiologic mechanism of the suppressive action of enflurane on spinal nociceptive transmission was examined in rabbits with intact and with transected spinal cords. Enflurane suppressed nociceptive responses in both intact and transected spinal cord groups. The suppressive effects of enflurane were significantly greater in the intact group than in the transected group. The suppressive effects of enflurane were not reversed by the addition of 0.2 mg·kg−1 of naloxone. These results suggest that enflurane suppresses nociceptive responses by activating descending inhibitory systems and directly suppressing activity at the spinal level. This suppressive action of enflurane does not interact with the opioid receptor.

The effects of composition of subarachnoid gas space and anesthetic gas mixture on cerebrospinal fluid pressure changes during cisternography for transsphenoidal craniectomy

The effects of gas composition in the subarachnoid space (injection of air or N2O) and in an anesthetic gas mixture (inhalation with or without N2O) on cerebrospinal fluid pressure were studied in 22 patients with pneumocisternography for transsphenoidal craniectomy. N2O (66%) anesthesia for 10 min increased cerebrospinal fluid pressure by up to 150% in 7 patients who were intrathecally injected with air. Withdrawal of N20 from the anesthetic gas mixture for sixty minutes reduced cerebrospinal fluid pressure to the initial pressure. A second N2O administration to the anesthetic gas mixture did not elevate cerebrospinal fluid pressure by as much as the first N20 administration. In 7 patients receiving subarachnoid air injection, replacing 66% N2O with 66% nitrogen prevented the change in cerebrospinal fluid pressure throughout the operation. In 8 patients N20 anesthesia and N20 intrathecal injection failed to eliminate the rise in cerebrospinal fluid pressure in 8 patients. Withdrawal of N20 from the anesthetic gas mixture for 60 min is recommended to prevent an extreme increase in cerebrospinal fluid pressure during pneumocisternography.

Effect of preanesthetic famotidine on gastric volume and pH.

The effect of preanesthetic 20 mg of famotidine on gastric fluid volume and pH were studied in patients scheduled for elective surgery. One hundred and twenty-eight patients were divided into four groups-control, intravenous, intramuscular and oral with 32 patients in each group. Patients in placebo group received no famotidine and served as control. Patients in the intravenous and intramuscular groups were administered famotidine one hour before surgery. Patients in the oral group were administered famotidine the night before and on the morning of surgery. Gasric volume in the control group was 19.1±10.8 ml; in the intravenous group, 7.4±6.4 ml; in the intramuscular group, 7.3±6.9 ml: and in the oral group, 7.1±6.9 ml. Gastric pH was 3.4±2.3, 6.8±1.1, 6.9±1.6, and 6.7±1.2 in groups one through four, respectively. When compared to the control group, famotidine significantly decreased gastric. volume and increased gastric pH. There were no statistical differences among the different modes of administration. No adverse effects were observed in this study. It is concluded that preanesthetic management of 20 mg of famotidine reduced the risk of acid aspiration pneumonitis.

Bilateral pneumothorax, subcutaneous emphysema and pneumomediastinum under anesthesia

•There are many reports on complication of tracheal intubation, but the development of acute respiratory distress associated with subcutaneous emphysema, pneumomediastinum and bilateral pneumothorax is a rare complication during general anesthesia. It has also been reported that tracheal perforation may be predisposed to such complication1-5. This is a report of an unexpected and dramatic experience we had of a case under anesthesia.