Droperidol lowers the shivering threshold in rabbits.

PURPOSE: Perioperative shivering is common and can occur as a result of hypothermia or changes in the threshold of thermoregulation. Droperidol usage for anesthesia is currently limited to its sedative and antiemetic effects. We investigated the effects of high and low doses of droperidol on the shivering threshold in rabbits. METHODS: Forty-two male Japanese white rabbits were anesthetized with isoflurane and randomly assigned to the control, high-dose, or low-dose group. Rabbits in the high-dose group received a 5 mg/kg droperidol bolus followed by continuous infusion at 5 mg/kg/h, those in the low-dose group received a 0.5 mg/kg droperidol bolus, and those in the control group received the same volume of saline as the high-dose group. Body temperature was reduced at a rate of 2-3 °C/h, and the shivering threshold was defined as the subject's core temperature (°C) at the onset of shivering. RESULTS: The shivering thresholds in the control, high-dose, and low-dose groups were 38.1 °C ± 1.1 °C, 36.7 °C ± 1.2 °C, and 36.9 °C ± 1.0 °C, respectively. The shivering thresholds were significantly lower in the high-dose and low-dose groups than in the control group (P < 0.01). The thresholds were comparable between the high-dose and low-dose groups. CONCLUSIONS: Droperidol in high and low doses effectively reduced the shivering threshold in rabbits. Droperidol has been used in low doses as an antiemetic. Low doses of droperidol can reduce the incidence of shivering perioperatively and during the induction of therapeutic hypothermia.

Severe hypoglycemia reduces the shivering threshold in rabbits.

BACKGROUND: We previously reported that each 100 mg dL- 1 reduction in blood glucose over the range from ≈90 to > 300 mg dL- 1 decreases the shivering threshold (triggering core temperature) in rabbits by 1 °C. However, the effects of lower blood glucose concentrations has yet to be evaluated. We thus evaluated the relationship between the shivering threshold and blood glucose concentration over the mild-to-severe hypoglycemic range. METHODS: Thirty-nine rabbits were lightly anaesthetized with isoflurane and randomly assigned to one of the three groups: 1) severe hypoglycemia, insulin and dextrose infusions titrated to achieve blood glucose concentration at 45-75 mg dL- 1; 2) mild hypoglycemia, insulin and dextrose infusions titrated to achieve blood glucose concentration at 75-100 mg dL- 1; and 3) saline infusion. Cooling by colonic perfusion of water at 10 °C was continued until shivering occurred or esophageal core temperatures reached to 34 °C. RESULTS: The shivering threshold in the severe hypoglycemic rabbits was 35.7 ± 1.1 °C (mean ± SD); the thresholds in the mild hypoglycemic rabbits was 37.0 ± 0.7 °C; and the threshold in the control rabbits was 37.9 ± 1.0 °C. The shivering threshold increased linearly with blood glucose concentration: shivering threshold (°C) = 0.032 ∙ [blood glucose concentration (mg dL- 1)] + 34.1, R2 = 0.45. The shivering threshold thus decreased by approximately 1 °C for each 31 mg dL- 1 decrease in blood glucose concentration. CONCLUSIONS: There was a linear relationship between blood glucose and the shivering threshold over the range from severe hypoglycemia to normoglycemia. Blood glucose perturbations in the hypoglycemic range reduced the shivering threshold about three times as much as previously reported for the hyperglycemic range.

The Effects of Blood Glucose Concentration on the Shivering Threshold in Rabbits.

BACKGROUND: Hyperglycemia is common in critically ill and surgical patients, as are core temperature disturbances. The effect of hyperglycemia on thermoregulatory defenses remains unknown. We determined the effect of blood glucose concentration on the shivering threshold in rabbits. METHODS: Twenty-seven rabbits lightly anesthetized with isoflurane were randomly assigned to infusions of (1) saline, (2) insulin titrated to produce blood glucose concentrations 60 to 100 mg/dL, or (3) 50% dextrose titrated to produce blood glucose concentrations 200 to 300 mg/dL. Core temperature was reduced at a rate of 2 to 3°C/h by perfusing water at 10°C through a plastic tube positioned in the colon. Cooling continued until shivering was observed by an investigator blinded to treatment or until esophageal (core) temperature reached 34°C. Core temperatures at the onset of shivering defined the threshold. All analyses were conducted using SAS version 9.3 (SAS Institute Inc., Cary, NC). RESULTS: Rabbits given saline shivered at 37.2 ± 0.5°C (mean ± SD). Rabbits given insulin shivered at 36.3 ± 1.1°C. Rabbits given dextrose shivered at 38.0 ± 0.6°C. The shivering threshold increased as a function of blood glucose concentration: shivering threshold (°C) = 0.009 [blood glucose concentration (mg/dL)] + 35.6, r = 0.53. The shivering threshold thus increased approximately 1°C for each 100 mg/dL increase in blood glucose concentration. CONCLUSIONS: Hyperglycemia increases the threshold for shivering, whereas hypoglycemia lowers the threshold on rabbits.

Supermassive black hole feeding and feedback observed on subparsec scales.

Active galaxies contain a supermassive black hole at their center that grows by accreting matter from the surrounding galaxy. The accretion process in about the central 10 parsecs has not been directly resolved in previous observations because of the small apparent angular sizes involved. We observed the active nucleus of the Circinus Galaxy using submillimeter interferometry. A dense inflow of molecular gas was evident on subparsec scales. We calculated that less than 3% of this inflow is accreted by the black hole, with the rest being ejected by multiphase outflows, providing feedback to the host galaxy. Our observations also reveal a dense gas disk surrounding the inflow that is gravitationally unstable, which drives the accretion into about the central 1 parsec.

Novel ultrashort-acting benzodiazepine remimazolam lowers shivering threshold in rabbits.

Shivering after surgery or during therapeutic hypothermia can lead to serious complications, such as myocardial infarction and respiratory failure. Although several anesthetics and opioids are shown to have anti-shivering effects, their sedative and respiratory side effects dampen the usefulness of these drugs for the prevention of shivering. In the present study, we explored the potential of a novel ultrashort-acting benzodiazepine, remimazolam, in the prevention of shivering using a rabbit model of hypothermia. Adult male Japanese white rabbits were anesthetized with isoflurane. The rabbits received saline (control), remimazolam (either 0.1 or 1 mg/kg/h), or remimazolam + flumazenil, a selective γ-aminobutyric acid (GABA) type A receptor antagonist (n = 6 each). Thirty minutes after discontinuation of the drugs, cooling was initiated by perfusing 10°C water via a plastic tube positioned in the colon until the animal shivered. Core body temperature and hemodynamic and physiological parameters were recorded. Remimazolam at 1 mg/kg/h significantly lowered the core temperature change during shivering (-2.50 ± 0.20°C vs. control: -1.00 ± 0.12°C, p = 0.0009). The effect of 1 mg/kg/h remimazolam on the core temperature change was abolished by flumazenil administration (-0.94 ± 0.16°C vs. control: -1.00 ± 0.12°C, p = 0.996). Most of the hemodynamic and physiological parameters did not differ significantly among groups during cooling. Remimazolam at a clinically relevant dose successfully suppressed shivering in rabbits via the GABA pathway even after its anesthetic effects likely disappeared. Remimazolam may have the potential to prevent shivering in patients undergoing surgery or therapeutic hypothermia.

Amiodarone Provides Long-Lasting Local Anesthesia and Analgesia in Open-State Mouse Nociceptors.

Local anesthetics with long-lasting effects and selectivity for nociceptors have been sought over the past decades. In this study, we investigated whether amiodarone, a multiple channel blocker, provides long-lasting local anesthesia and whether adding a TRPV1 channel activator selectively prolongs sensory anesthetic effects without prolonging motor blockade. Additionally, we examined whether amiodarone provides long-lasting analgesic effects against inflammatory pain without TRPV1 channel activator co-administration. In the sciatic nerve block model, 32 adult C57BL/6J mice received either bupivacaine, amiodarone with or without capsaicin (a TRPV1 agonist), or vehicle via peri-sciatic nerve injection. Sensory and motor blockade were assessed either by pinprick and toe spread tests, respectively. In another set of 16 mice, inflammatory pain was induced in the hind paw by zymosan injection, followed by administration of either amiodarone or vehicle. Mechanical and thermal sensitivity and paw thickness were assessed using the von Frey and Hargreaves tests, respectively. The possible cardiovascular and neurological side effects of local amiodarone injection were assessed in another set of 12 mice. In the sciatic nerve block model, amiodarone produced robust anesthesia, and the co-administration of TRPV1 agonist capsaicin prolonged the duration of sensory blockade, but not that of motor blockade [complete sensory block duration: 195.0 ± 9.8 min vs. 28.8 ± 1.3 min, F (2, 21) = 317.6, p < 0.01, complete motor block duration: 27.5 ± 1.6 min vs. 21.3 ± 2.3 min, F (2, 22) = 11.1, p = 0.0695]. In the zymosan-induced inflammatory pain model, low-dose amiodarone was effective in reversing the mechanical and thermal hypersensitivity not requiring capsaicin co-administration [50% withdrawal threshold at 8 h (g): 0.85 ± 0.09 vs. 0.25 ± 0.08, p < 0.01, withdrawal latency at 4 h (s) 8.5 ± 0.5 vs. 5.7 ± 1.4, p < 0.05]. Low-dose amiodarone did not affect zymosan-induced paw inflammation. Local amiodarone did not cause cardiovascular or central nervous system side effects. Amiodarone may have the potential to be a long-acting and nociceptor-selective local anesthetic and analgesic method acting over open-state large-pore channels.

The usefulness of an earphone-type infrared tympanic thermometer during cardiac surgery with cardiopulmonary bypass: clinical report.

We evaluated the usefulness of a novel earphone-type infrared tympanic thermometer (IRT) during cardiac surgery with cardiopulmonary bypass. Tympanic membrane temperature (T(Tym)) was monitored using the IRT inserted into the right ear canal of 12 adult patients (ASA III) who had been scheduled for elective cardiac surgery with cardiopulmonary bypass under general anesthesia. Rectum (T(Rec)) and nasopharyngeal temperatures (T(Naso)) were also monitored, and all temperatures were recorded at 5-min intervals during cardiopulmonary bypass. Operating room temperature was kept at 20°-27°C; a conductive warming/cooling system was used to control the patient's body temperature. Of 265 measurements obtained, body temperature range was 31.6°-37.6°C. No complications were related to site of insertion of the monitoring probe. Significant correlations were seen between T(Tym) and T(Naso) (r = 0.971, P < 0.001), and T(Tym) and T(Rec) (r = 0.759, P < 0.001). A Bland-Altman plot showed that average temperature of T (Tym) was 0.06°C above T(Naso) (±0.66°C, 2 SD) and 0.12°C below T(Rec) (±1.78°C, 2 SD). We conclude that an earphone-type IRT is noninvasive and hygienic and could continuously evaluate selective cerebral temperature during cardiopulmonary bypass in adults.

Delayed-Onset Bilateral Vocal Cord Paralysis After Abdominal Surgery: A Case Report.

A 62-year-old male patient suddenly developed severe dyspnea due to bilateral vocal cord paralysis (VCP) 4 days after an abdominal surgery. Emergent tracheostomy effectively improved the patient's respiratory status. The present case report emphasizes that bilateral VCP could occur even several days after an abdominal surgery in patients with multiple risk factors, such as hypertension, diabetes mellitus, an older age, male sex, and an upper abdominal surgery. Even if the patient does not present with hoarseness, bilateral VCP should not be ruled out, because a slight phonetic change can be the only symptom of early-stage bilateral VCP.

Characterization of the supermirror hard-x-ray telescope for the InFOCmuS balloon experiment.

A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20-40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for muCrab Sensitivity balloon experiment.