Administration Of Isoflurane Research Articles

Cardiorespiratory effects of isoflurane in Asiatic black bears (Ursus thibetanus) anesthetized with intramuscular medetomidine and zolazepam/tiletamine.

The objective of this study was to determine the dose-dependent effects of isoflurane on various cardiovascular parameters and the stable range of isoflurane concentrations in Asiatic black bears (Ursus thibetanus). Seven Asiatic black bears were intramuscularly injected with medetomidine, zolazepam and tiletamine (MZT) to induce anesthesia, and anesthesia was maintained by administering isoflurane in 100% oxygen (4 l/min) without mechanical ventilation. Several cardiovascular parameters were measured at five end-tidal isoflurane concentrations (0.5, 1.0, 1.5, 2.0, and 2.5%). Blood was collected from the femoral artery before administration of isoflurane and after each administration for immediate blood gas analysis. Isoflurane produced dose-dependent increases in heart rate, respiratory rate, minute volume, end-tidal carbon dioxide (CO2) partial pressure and the partial pressure of arterial CO2, and dose-dependent decreases in non-invasive blood pressure and tidal volume. Rectal temperature, oxygenation and acid-base balance were unaffected by isoflurane. All parameters in this study were in a clinically acceptable range at all times. The data show that the combination of MZT and isoflurane is suitable for general anesthesia in Asiatic black bears with spontaneous breathing during prolonged procedures. End-tidal isoflurane concentrations of 0.5 to 2.5% can be used in Asiatic black bears without adverse side effects.

Comparative immunohistochemical assessment of the effect of repetitive anesthesia with isoflurane and sevoflurane on rat liver

Inhalation anesthetics are used in human, as well as veterinary medical practice. In the present study we investigated the effect of isoflurane and sevoflurane on rat hepatocytes. A total of 40 Wistar female rats were used in this study. Animals were divided in groups of 5 rats. Groups IM, SM served as control groups. Groups I1, I2, I3 were used to study isoflurane and S1, S2, S3 for sevoflurane study. They were anesthetized 3 times, for 2h long, at 2 days interval with a concentration of: 1.5% isoflurane (I1, I2, I3) and 2% sevoflurane (S1, S2, S3). The oxygen supply throughout the anesthesia was 1LO2/min. Groups IM, IS, I1, S1 were sacrificed immediately after the last anesthesia. Groups I2, S2 were sacrificed 6h after the last anesthesia, and groups I3, S3, 24h post-anesthesia. Liver samples were harvested to highlight caspase-3 in apoptotic hepatocytes. Following isoflurane administration, there were less than 1% cells in apoptosis highlighted in rat livers from groups IM, I1 and I2. At 24h post-anesthesia (group I3), a small number of apoptotic hepatocytes was highlighted (around 3.23% cells in apoptosis), with a strictly periacinar disposition, randomly distributed in a small number of hepatic lobules. After sevoflurane administration, less than 1% apoptotic hepatocytes were identified at all control moments throughout the study. The results suggest that the anesthetics do not present a considerable hepatotoxicity. The comparative assessment of the two anesthetics shows that sevoflurane is superior to isoflurane.

Isoflurane-induced inactivation of CREB through histone deacetylase 4 is responsible for cognitive impairment in developing brain

Anesthetics including isoflurane are known to induce neuronal dysfunction in the developing brain, however, the underlying mechanism is mostly unknown. The transcriptional activation of CREB (cyclic AMP response element binding protein) and the alterations in acetylation of histones modulated by several histone deacetylases such as HDAC4 (histone deacetylase 4) are known to contribute to synaptic plasticity in the brain. Here we have shown that administration of isoflurane (1.4%) for 2h leads to transcriptional inactivation of CREB which results in loss of dendritic outgrowth and decreased expression level of proteins essential for memory and cognitive functions, such as BDNF, and c-fos in the developing brain of mice at postnatal day 7 (PND7). To elucidate the molecular mechanism, we found that exposure to isoflurane leads to an increase in nuclear translocation of HDAC4, which interacts with CREB in the nucleus. This event, in turn, results in a decrease in interaction between an acetyltransferase, CBP, and CREB that ultimately leads to transcriptional inactivation of CREB. As a result, the expression level of BDNF, and c-fos were significantly down-regulated after administration of isoflurane in PND7 brain. Depletion of HDAC4 in PND7 brain rescues the transcriptional activation of CREB along with augmentation in the level of the expression level of BDNF and c-fos. Moreover, administration of lentiviral particles of HDAC4 RNAi in primary neurons rescues neurite outgrowth following isoflurane treatment. Taken together, our study suggests that HDAC4-induced transcriptional inactivation of CREB is responsible for isoflurane-induced cognitive dysfunction in the brain.

Euthanasia using gaseous agents in laboratory rodents.

Several questions have been raised in recent years about the euthanasia of laboratory rodents. Euthanasia using inhaled agents is considered to be a suitable aesthetic method for use with a large number of animals simultaneously. Nevertheless, its aversive potential has been criticized in terms of animal welfare. The data available regarding the use of carbon dioxide (CO2), inhaled anaesthetics (such as isoflurane, sevoflurane, halothane and enflurane), as well as carbon monoxide and inert gases are discussed throughout this review. Euthanasia of fetuses and neonates is also addressed. A table listing currently available information to ease access to data regarding euthanasia techniques using gaseous agents in laboratory rodents was compiled. Regarding better animal welfare, there is currently insufficient evidence to advocate banning or replacing CO2 in the euthanasia of rodents; however, there are hints that alternative gases are more humane. The exposure to a volatile anaesthetic gas before loss of consciousness has been proposed by some scientific studies to minimize distress; however, the impact of such a measure is not clear. Areas of inconsistency within the euthanasia literature have been highlighted recently and stem from insufficient knowledge, especially regarding the advantages of the administration of isoflurane or sevoflurane over CO2, or other methods, before loss of consciousness. Alternative methods to minimize distress may include the development of techniques aimed at inducing death in the home cage of animals. Scientific outcomes have to be considered before choosing the most suitable euthanasia method to obtain the best results and accomplish the 3Rs (replacement, reduction and refinement).

Relevance of using bispectral index monitoring to stabilize hemodynamic parameters in patients undergoing cardiac surgery under cardiopulmonary bypass by better titration of anaesthetic agents

Background:The aim of our study is to find the relevance of using a bispectral index (BIS) monitor, a neurophysiological monitoring device, in patients undergoing cardiopulmonary bypass and measure their hemodynamic stability due to better titration of anaesthetic drugs.Methods: After approval of the ethical committee and informed consents, forty patients were included in this study, age ranging between 45 and 60 years, of both sexes, scheduled for elective coronary bypass surgery or valve replacement done with cardiopulmonary bypass (CPB) were selected. This was a prospective, randomized, controlled study in which the subjects were randomly allocated into 2 groups of 20 each as per random number chart. They were (I) BIS monitor group (group A) where A the administration of propofol and isoflurane were controlled to achieve the target range of 40-60 BIS value and (II) BIS blinded to anaesthesiologist group (group B), where the BIS values were blinded to the anesthesiologist and the administration of propofol and isoflurane were left to the anesthesiologist's discretion.Results:Patient in group A had stable hemodynamic in that the incidence of fluctuation of blood pressure were only 15% while it was 80% in group B. Similarly the fluctuations in heart rate were 10% in group A and 75% in group B.Conclusions:By using Bispectral index monitor we can maintain a better hemodynamic stability in patients during cardiac surgery under cardiopulmonary bypass. This finding was in agreement to similar studies conducted by various researchers.

Evaluation of isoflurane anesthesia after xylazine/ketamineadministration in dromedary camels

The objective of this study was to evaluate isoflurane after premedication with xylazine and induction with ketamine in camels. Six healthy adult female dromedary camels were premedicated with xylazine (0.2 mg/kg, IV). Twenty minutes later, anesthesia was induced with ketamine (2 mg/kg, IV) and was maintained with isoflurane in 100% oxygen. Onset and duration of anesthesia were recorded. Rectal temperature, respiratory rate, heart rate, oxygen hemoglobin saturation, and blood pressure were measured before and 20 min after xylazine administration and every 10 min thereafter until recovery. Lead II electrocardiogram was used to monitor camels for the presence of arrhythmias. Venous and arterial blood samples were taken for hematological examination and blood gases and pH, respectively. The results are thought to be the first detailed evaluation of isoflurane anesthesia in dromedary camels. Significant decrease in heart rate after xylazine/ketamine administration and significant decreases in rectal temperature and arterial blood pressure were recorded in camels during isoflurane administration. However, percentage of oxygen hemoglobin saturation significantly increased with significant changes in complete blood count and minor changes in arterial pH, PCO 2 , and PO 2 during the study. The quality of anesthesia and recovery was good to excellent. In conclusion, isoflurane resulted in smooth recovery without complications and can be considered a good inhalation anesthetic for camels.

Effects of isoflurane and ethanol administration on c-Fos immunoreactivity in mice

Noninvasive functional imaging holds great promise for the future of translational research, due to the ability to directly compare between preclinical and clinical models of psychiatric disorders. Despite this potential, concerns have been raised regarding the necessity to anesthetize rodent and monkey subjects during these procedures, because anesthetics may alter neuronal activity. For example, in studies on drugs of abuse and alcohol, it is not clear to what extent anesthesia can interfere with drug-induced neural activity. Therefore, the current study investigated whole-brain c-Fos activation following isoflurane anesthesia as well as ethanol-induced activation of c-Fos in anesthetized mice. In the first experiment, we examined effects of one or three sessions of gaseous isoflurane on c-Fos activation across the brain in male C57BL/6J mice. Isoflurane administration led to c-Fos activation in several areas, including the piriform cortex and lateral septum. Lower or similar levels of activation in these areas were detected after three sessions of isoflurane, suggesting that multiple exposures may eliminate some of the enhanced neuronal activation caused by acute isoflurane. In the second experiment, we investigated the ability of ethanol injection (1.5 or 2.5g/kgi.p.) to induce c-Fos activation under anesthesia. Following three sessions of isoflurane, 1.5g/kg of ethanol induced c-Fos in the central nucleus of amygdala and the centrally-projecting Edinger–Westphal nucleus (EWcp). This induction was lower after 2.5g/kg of ethanol. These results demonstrate that ethanol-induced neural activation can be detected in the presence of isoflurane anesthesia. They also suggest, that while habituation to isoflurane helps reduce neuronal activation, interaction between effects of anesthesia and alcohol can occur. Studies using fMRI imaging could benefit from using habituated animals and dose–response analyses.

Comparative immunohistochemical assessment of the effect of repetitive anesthesia with isoflurane and sevoflurane on rat liver

Background and objectivesInhalation anesthetics are used in human, as well as veterinary medical practice. In the present study we investigated the effect of isoflurane and sevoflurane on rat hepatocytes. MethodsA total of 40 Wistar female rats were used in this study. Animals were divided in groups of 5 rats. Groups IM, SM served as control groups. Groups I1, I2, I3 were used to study isoflurane and S1, S2, S3 for sevoflurane study. They were anesthetized 3 times, for 2h long, at 2 days interval with a concentration of: 1.5% isoflurane (I1, I2, I3) and 2% sevoflurane (S1, S2, S3). The oxygen supply throughout the anesthesia was 1LO2/min. Groups IM, IS, I1, S1 were sacrificed immediately after the last anesthesia. Groups I2, S2 were sacrificed 6h after the last anesthesia, and groups I3, S3, 24h post-anesthesia. Liver samples were harvested to highlight caspase-3 in apoptotic hepatocytes. ResultsFollowing isoflurane administration, there were less than 1% cells in apoptosis highlighted in rat livers from groups IM, I1 and I2. At 24h post-anesthesia (group I3), a small number of apoptotic hepatocytes was highlighted (around 3.23% cells in apoptosis), with a strictly periacinar disposition, randomly distributed in a small number of hepatic lobules. After sevoflurane administration, less than 1% apoptotic hepatocytes were identified at all control moments throughout the study. ConclusionsThe results suggest that the anesthetics do not present a considerable hepatotoxicity. The comparative assessment of the two anesthetics shows that sevoflurane is superior to isoflurane.

Preischemic Administration of Sevoflurane Does not Exert Dose-dependent Effects on the Outcome of Severe Forebrain Ischemia in Rats.

We previously showed that preischemic administration of high-dose isoflurane worsened the outcome from severe forebrain ischemia in rats. Conversely, high doses of sevoflurane have been reported to improve the outcome from forebrain ischemia when the insult is moderate. To clarify the dose-dependent effects of sevoflurane on severe forebrain ischemia, we performed an outcome study using an identical protocol to that in our previous study with isoflurane. Fasting male Sprague-Dawley rats underwent surgical preparation for forebrain ischemia under halothane anesthesia. Anesthesia was changed to fentanyl/nitrous oxide to eliminate the halothane, after which 30 minutes of 0.5, 1.0, 1.5, 2.0, or 2.5 minimum alveolar concentration sevoflurane was administered. Ten minutes of ischemia was induced by bilateral carotid occlusion plus systemic hypotension, in which cessation of electroencephalographic activity was confirmed. Sevoflurane was discontinued and anesthesia continued with fentanyl/nitrous oxide for an additional 100 minutes. Outcome evaluation at 5 days postischemia included seizure incidence, mortality rate, neuromotor score, and histologic injuries to the cerebral cortex and hippocampal CA1 and CA3. Different doses of sevoflurane did not statistically affect seizure incidence (10.0% to 18.2%), mortality rate (20.0% to 46.7%), cortical damage (mild to moderate degree), or hippocampal CA1 damage (93.7% to 96.7% neuronal necrosis) or CA3 damage (36.3% to 41.7%). Dose-dependent effects of sevoflurane were not observed for any of the outcome variables assessed in this rat model of severe forebrain ischemia.

In vivo assessment of arterial stiffness in the isoflurane anesthetized spontaneously hypertensive rat.

BackgroundRodent models are increasingly used to study the development and progression of arterial stiffness. Both the non-invasive Doppler derived Pulse Wave Velocity (PWV) and the invasively determined arterial elastance index (EaI) have been used to assess arterial stiffness in rats and mice, but the need for anesthetic agents to make these in vivo estimates may limit their utility. Thus, we sought to determine: 1) if known differences in arterial stiffness in spontaneously hypertensive rats (SHR) are detectable by PWV and EaI measurements when made under isoflurane anesthesia, and 2) if these two uniquely acquired assessments of arterial elasticity correlate.MethodsWe obtained PWV and EaI measurements in isoflurane anesthetized young and old SHRs, which are known to have significant differences in arterial stiffness. Doppler pulse waves were recorded from carotid and iliac arteries and the distance (D) between probe applantation sites was recorded. Simultaneously, an EKG was obtained, and the time intervals between the R-wave of the EKG to the foot of the Doppler waveforms were measured and averaged over three cardiac cycles. Pulse-transit time (T) of the carotid to iliac artery was determined, and PWV was calculated as Distance (D)/Time (T), where D = the distance from the carotid to the iliac notch and T = (R to iliac foot) - (R to carotid foot). EaI was subsequently determined from pressure volumes loops obtained via left ventricle catheterization.ResultsPWV and EaI were found to be significantly faster in the older rats (13.2 ± 2.0 vs. 8.0 ± 0.8 m/sec, p < 0.001; 120 ± 20 vs. 97 ± 16 mmHg/μl/g, p <0.05). Bland-Altman analyses of intra- and inter-observer measures demonstrate a statistically significant relationship between readings (p < 0.0001). PWV and EaI measurements were found to be significantly and positively correlated with a correlation coefficient of 0.53 (p < 0.05).ConclusionOur study suggests that isoflurane administration does not limit Doppler PWV or EaI measures in their ability to provide accurate, in vivo assessments of relative arterial stiffness in isoflurane anesthetised SHR rats. Furthermore, PWV data obtained in these rats correlate well with invasively determined EaI.

Isoflurane Protects Against Injury Caused by Deprivation of Oxygen and Glucose in Microglia Through Regulation of the Toll-Like Receptor 4 Pathway

Oxygen and glucose deprivation (OGD) are the most important factors related to tissue damage resulting from stroke. Microglial cells have been found to be very vulnerable to ischemia and OGD. It has been reported that isoflurane exposure can protect the mammalian brain from insults such as ischemic stroke; however, the effects of isoflurane on OGD-induced injury in microglia are as yet unknown. In this study, we investigated the effects of isoflurane on OGD-induced injury in microglia. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) revealed that OGD did indeed induce cell death in microglia. However, isoflurane preconditioning attenuated OGD-induced cell death. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay demonstrated that isoflurane treatment alleviated OGD-induced apoptosis. Toll-like receptor 4 (TLR4) plays a considerable role in the induction of innate immune and inflammatory responses. Our results indicate that isoflurane preconditioning inhibits the upregulation of TLR4 as well as the activation of its downstream molecules, such as c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-κB), in BV-2 microglia exposed to OGD. Importantly, we also found that isoflurane pretreatment significantly reduces the production of proinflammatory factors such as tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), IL-β, and nitric oxide (NO). The results indicate that TLR4 and its downstream NF-κB-dependent signaling pathway contribute to the neuroprotection of microglia exposed to OGD/reoxygenation by administration of isoflurane.

Geranylgeranylacetone and volatile anesthetic-induced cardiac protection synergism is dependent on caveolae and caveolin-3

Pharmacological preconditioning, including that with geranylgeranylacetone (GGA) and volatile anesthetics, has been shown to confer cardiac protection from ischemia/reperfusion injury although the mechanisms for this protection are poorly understood. Caveolins, integral membrane proteins that act as scaffolding proteins in caveolar membranes, localize molecules involved in cardiac protection. We have tested the hypothesis that caveolin-3 (Cav-3), the predominant isoform in cardiac myocytes, is essential for the synergistic effect observed between GGA and volatile anesthetics. Mice were randomly assigned to receive GGA, isoflurane [0.5 and 1.0 minimum alveolar concentration (MAC)], or GGA + isoflurane (0.5 MAC). An in vivo mouse model of ischemia/reperfusion injury was tested in wild-type and Cav-3 knockout mice, and the infarct size was determined. Biochemical assays were also performed in excised hearts. Geranylgeranylacetone and therapeutic isoflurane (1.0 MAC) independently reduced infarct size (31.6 ± 6.1 and 28.0 ± 5.0% of the area at risk, respectively; n = 10) as compared to the controls (45.8 ± 9.4%; n = 10). The combination GGA + sub-therapeutic isoflurane (0.5 MAC) further decreased the infarct size to 19.3 ± 5.1% (n = 10). Preconditioning [GGA, isoflurane (1.0 MAC), and GGA + isoflurane] increased the amount of Cav-3 protein in the discontinuous sucrose-gradient buoyant fractions. Additionally, cardiac protection was not observed in Cav-3 knockout mice following the administration of GGA, isoflurane, and GGA + isoflurane. Combined administration of GGA + isoflurane had a synergistic effect, enhancing the protection against myocardial infarction to a greater extent than either drug alone. This beneficial effect is mediated by Cav-3 expression.

Preconditioning renoprotective effect of isoflurane in a rat model of virtual renal transplant

BackgroundThe development of warm–cold ischemia–reperfusion (IR) injury of the kidney grafts is inevitable during renal transplantation. However, there is currently no definite renoprotective strategy available in the protection of the graft tissue. In the present study, we compared the renal protection of preconditioning isoflurane with N-acetylcysteine (NAC) in a novel rat model of warm–cold renal IR injury. Materials and methodsAdult Sprague–Dawley rats were randomly assigned to receive inhaled isoflurane (1.5% for 2 h), NAC (1 g/kg, intra-arterial injection) or placebo before the induction of brief warm ischemia (10 min) followed by cold ischemia (45 min) periods. Plasma levels of creatinine and tissue inflammatory reaction in the kidney were analyzed 72 h after reperfusion. ResultsElevated plasma level of creatinine and urea indicated the development of acute renal injury secondary to IR injury. The creatinine levels were reduced in animals pretreated with inhaled isoflurane and NAC, and the level was more significantly decreased in the isoflurane-treated group. Preconditioning with volatile isoflurane also significantly suppressed the tissue myeloperoxidase activity and expression of the inducible nitric oxide synthase. Immunostaining confirmed that myeloperoxidase expression was most significantly attenuated in the glomerulus and peritubular capillaries of rats pre-exposed to isoflurane. ConclusionsWe present the first study demonstrating that the administration of volatile isoflurane before induction of experimental warm–cold renal IR injury provides preconditioning renoprotective effect, which is superior to the treatment with NAC. The beneficial renoprotective effect of isoflurane is most likely mediated by attenuation of proinflammatory reaction in the injured kidney.

Isoflurane prevents learning deficiencies caused by brief hypoxia and hypotension in adult Sprague Dawley rats

Context: Hypotension causes histologic changes in the hippocampal CA1 area, while behavior remains unchanged. We believe that an even stronger insult may also cause behavioral changes.Objective: We used a rat hemorrhagic shock model plus temporary hypoxia to assess functional outcome at different time points post-injury. Our hypothesis is that the damage can be attenuated by the use of isoflurane.Materials and methods: Rats were subjected to brief hypotension. Animals were evaluated at different time points after receiving hypoxia and hypotension, with and without isoflurane treatment.Results: The administration of isoflurane after the insult protected the animals from memory alterations. No histopatologic changes were found in any of the groups.Discussion and conclusions: This observation suggests that in this model of hypotension plus hypoxia there is mild cerebral damage that is reflected by memory changes. Exposure to isoflurane after the insult can prevent the onset of memory deficits.

Dexmedetomidine decreases requirement of thiopentone sodium and pentazocine followed with improved recovery in patients undergoing laparoscopic cholecystectomy.

Background:Pain relief remains the most fundamental and consequential aspect of surgery for patients throughout perioperative period. Dexmedetomidine has created an interest in α2-adrenoceptor agonists in the management of pain and hence the aim of this study was to evaluate the effectiveness of the drug in hilly population of North India.Materials and Methods:Patients, irrespective of gender, were randomly allocated to two groups, control and test, each having 30 patients. Test group received an infusion of dexmedetomidine at a rate of 0.5 μg/kg/h 30 min before induction and 0.6 μg/kg/h after inducing anesthesia. Control patients received a volume-matched infusion of normal saline as placebo. Approximately 2 min before induction, analgesia was provided in the form of pentazocine, 0.5 mg/kg in control and 0.3 mg/kg in the test group. Induction was performed by 2 mg/kg thiopentone sodium supplemented with intravenous boluses of 25 mg thiopentone sodium every 15 s until loss of eyelid reflex (determined every 15 s). Induction dose of thiopentone sodium and total pentazocine dose were recorded. Recovery was assessed on the clinical recovery score (CRS) scale.Results:Infusion of dexmedetomidine decreased the induction dose of thiopentone approximately by 33% and of pentazocine dose by approximately 39% in patients undergoing laparoscopic cholecystectomy. Moreover, incidence of pain was also decreased significantly. Improved CRS from 4.33 to 6.87 was noticed immediately post-operatively in dexmedetomidine group of patients.Conclusion:Infusion of dexmedetomidine during the laparoscopic cholecystectomy decreases the requirement of thiopentone sodium and pentazocine and leads to early recovery of patients.

Comparison of anesthesia with fully reversible dexmedetomidine-butorphanol-midazolam versus ketamine-midazolam in captive Asian small-clawed otters (Aonyx cinereus)

To evaluate the efficacy and safety of a combination of dexmedetomidine, butorphanol, and midazolam administered IM for anesthesia in captive Asian small-clawed otters (Aonyx cinereus) and to compare this combination with a combination of ketamine and midazolam. Prospective crossover study. 10 captive Asian small-clawed otters. A combination of either dexmedetomidine (0.03 mg/kg [0.014 mg/lb]), butorphanol (0.2 mg/kg [0.091 mg/lb]), and midazolam (0.15 mg/kg [0.068 mg/lb]) or ketamine (10.1 mg/kg [4.59 mg/lb]) and midazolam (0.3 mg/kg [0.14 mg/lb]) was administered IM to otters for immobilization to allow scheduled wellness examinations. Otters were intubated and administered 100% oxygen during the examination. Anesthesia was supplemented with isoflurane in oxygen if necessary. Routine medical procedures, including blood collection, radiography, echocardiography, dental scaling, vaccinations, and contraception administration, were performed as indicated during the immobilization. Physiologic, clinicopathologic, and anesthetic variables were recorded and compared. Otters given dexmedetomidine-butorphanol-midazolam were administered atipamezole (0.2 mg/kg [0.091 mg/lb]), naltrexone (0.6 mg/kg [0.27 mg/lb]), and flumazenil (0.05 mg/kg [0.023 mg/lb]) IM at the completion of the examination. The need for and duration of isoflurane administration were greater for ketamine-midazolam anesthesia, compared with dexmedetomidine-butorphanol-midazolam anesthesia. Recoveries were shorter and subjectively smoother with dexmedetomidine-butorphanol-midazolam. Heart rates were significantly higher during ketamine-midazolam anesthesia. Regardless of protocol, all otters developed hypothermia and hypercapnia during anesthesia. Both protocols were safe and effective for this species, but the reversible nature of dexmedetomidine-butorphanol-midazolam resulted in more rapid recoveries than did ketamine-midazolam. Otters anesthetized with ketamine-midazolam may require additional anesthetic medications for routine examinations, and assisted ventilation and thermal support may be of benefit with either protocol.

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Introduction: Isoflurane is conventionally used for general anesthesia, but also has a well-documented off-label use as a bronchodilator for the treatment of severe, refractory status asthmaticus. Several cases have been described in the medical literature in which patients receiving prolonged isoflurane therapy for asthma have experienced untoward neurologic side effects. To our knowledge, there are no documented cases of bilateral fixed and dilated pupils secondary to isoflurane therapy in critically-ill children. We report this condition in two asthmatic patients who received isoflurane. Case One: An 8 year-old male with past history of asthma was admitted to the pediatric intensive care unit in respiratory distress secondary to status asthmaticus. The exacerbation was refractory to supplemental oxygen, continuous albuterol, intravenous (IV) steroids, subcutaneous epinephrine, magnesium sulfate and terbutaline infusion. He ultimately required intubation and mechanical ventilation. Isoflurane (1.8% exhaled concentration) was initiated via an anesthesia ventilator. Approximately 12 hours after initiation of isoflurane, the patient was found to have bilateral dilated (5-6 mm) and non-reactive pupils. A non-contrast head CT revealed no acute intracranial pathology. Case Two: A 7 year-old male with past history of asthma presented in severe respiratory distress with hypoxemia. His initial treatment included subcutaneous epinephrine, nebulized albuterol, IV steroids and terbutaline infusion. He eventually required intubation, and was emergently placed on isoflurane (1.8% exhaled concentration) via an anesthesia ventilator. The patient was noted to have bilateral dilated (7-8 mm) and non-reactive pupils within 2 hours of isoflurane initiation. As in case one, a non-contrast head CT revealed no acute intracranial pathology. Discussion: In both cases, the children developed pupillary changes (fixed and dilated pupils) during the initial hours of isoflurane therapy, which resolved within 24 hours of isoflurane discontinuation. The extent to which isoflurane contributed to these findings is unclear. While it is difficult to implicate a single causative agent underlying the pupillary changes observed in both cases, it is likely that isoflurane was a contributing factor. Further investigation is needed to determine the effects of isoflurane administration on pupillary activity.

The ability of bispectral index to detect intra‐operative wakefulness during isoflurane/air anaesthesia, compared with the isolated forearm technique

Clinical signs are unreliable for guiding anaesthetic administration and it is suggested that using the bispectral index can improve anaesthetic delivery. In the current study, isoflurane administration was guided to a bispectral index range of 55-60. Intra-operative responsiveness, as assessed by the isolated forearm technique, was compared with whether the bispectral index predicted/identified a patient's appropriate hand movements in response to commands. Thirty-four women underwent major gynaecological surgery with isoflurane/air and atracurium. Eleven women responded on 32 occasions with appropriate hand movements to commands given during surgery, of which the bispectral index detected 17 (sensitivity 53%). The bispectral index suggested consciousness 660 times in the absence of any movement responses (specificity 69%). The positive predictive value of the bispectral index was 3%. The median (IQR [range]) bispectral index value associated with an intra-operative response was significantly lower than that associated with eye opening after surgery: 60 (50-68 [36-83]) vs 77 (75-84 [59-90]), respectively (p = 2.25 × 10(-8)). Conversely, end-tidal isoflurane concentration was significantly higher at intra-operative response than at eye opening: 0.3 (0.3-0.4 [0.2-0.9]) vs 0.2 (0.1-0.2 [0.1-0.3]), respectively (p = 7.36 × 10(-8)). For patients who responded more than once during surgery, the bispectral index value associated with a response was not constant. No patient had recall for surgery or the taped commands, and only one could remember dreaming (a good dream). Titrating isoflurane to target a bispectral index range of 55-60 may result in an unacceptable number of patients who are conscious during surgery (albeit without recall).

Isoflurane post-conditioning protects primary cultures of cortical neurons against oxygen and glucose deprivation injury via upregulation of Slit2/Robo1

Different mechanisms have been suggested to contribute to isoflurane-mediated neuroprotection. Previous studies have suggested that the protein Slit can abrogate neuronal death in mixed neuronal–glial cultures exposed to oxygen–glucose deprivation (OGD) and reperfusion (OGD/R). We hypothesized that isoflurane increases the expression of Slit and its receptor Robo when cortical neurons are exposed to OGD/R. To test this hypothesis, we exposed primary cortical neurons to OGD for 90min and reperfusion for 24h and investigated how isoflurane post-conditioning affected cell survival and expression of Slit2 and receptors Robo1 and Robo4. Cell survival increased after administration of isoflurane, as assessed by the lactate dehydrogenase assay, trypan blue analysis, and propidium iodide staining. Western blot analysis showed that cleaved caspase-3 was increased after OGD/R(P<0.01) but reduced by isoflurane post-conditioning. Real-time PCR and Western blot analysis showed that the expression levels of Slit2 and Robo1, but not Robo4, were increased after OGD/R (P<0.5) and increased even further by isoflurane post-conditioning (P<0.01). Our results suggest that isoflurane post-conditioning markedly attenuates apoptosis and necrosis of cortical neurons exposed to OGD/R possibly in part via elevation of Slit2 and Robo1 expression. These findings provide a novel explanation for the pleiotropic effects of isoflurane that could benefit the central nervous system.

Observations on the Effects of Inhaled Isoflurane in Long-term Sedation of Critically Ill Children Using a Modified AnaConDa©-System

Long-term intravenous sedation may present problems due to dependence and side effects. Medical records of children who were administered isoflurane were reviewed. 15 patients (9 boys, 6 girls) with a mean age of 11.8 month (+2.4) were analysed.Analgesia and sedation was given in mean 9.7+1.1 days before commencing inhalation using a modified application device (AnaConDa©). Administration was given over a period of 7.2+1.4 days. Depth of sedation was monitored by using Comfort- and Hartwig-scores. Observations included continuous monitoring of heart-rate, pulse oxymetry, blood pressure and cerebral tissue oxygenation.Within 4 h post administration of isoflurane a satisfactory increase in the depth of sedation was seen and kept till extubation. 6/15 patients received tracheostomies during the observation period. None of the patients observed suffered life-critical events of the modified application of isoflurane proceeded without complications. Ketamine and clonidine infusion rates were significantly reduced (p<0.005) as well as the use and overall infusion rate of midazolam, γ-hydroxy butyrate, fentanyl and morphine (p<0.05).Isoflurane inhalation may provide an additional option for long-term sedation in a specific group of critically ill infants but neurodegenerative toxic effects will have to be taken into account when using volatile anesthetics at any time during infancy.