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Hypercapnia Impairs Vasoreactivity to Changes in Blood Pressure and Intraocular Pressure in Rat Retina. Optom Vis Sci 2020; 96:470-476. [PMID: 31274734 DOI: 10.1097/opx.0000000000001400] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
SIGNIFICANCE The balance between oxygen and carbon dioxide sets the resting tone (or diameter) of retinal blood vessels. Eyes that are hypercapnic use up their "vasodilatory reserve" and therefore fail to respond adequately to changes in intraocular or blood pressure. PURPOSE Retinal vessels are regulated by both myogenic and metabolic mechanisms. We considered whether alteration of metabolic status would modify the vascular response to ocular perfusion pressure (OPP) lowering in rat retina. METHODS In pentobarbital anesthetized adult Brown-Norway rats, normocapnia or hypercapnia was achieved by artificially ventilating animals with air or 5% carbon dioxide in ~30% oxygen, respectively. Ocular perfusion pressure was gradually reduced to ~20 mmHg by either lowering blood pressure (slowly drawing blood from a femoral artery/vein) or manometrically increasing intraocular pressure under normocapnic or hypercapnic conditions. In all four groups (n = 7 eyes for each), a confocal scanning laser ophthalmoscope was used to acquire image sequences centered on the optic nerve throughout pressure modification. The diameter of arterioles and venules at various OPP levels was measured and expressed as percentage relative to their own baseline. The response of arterioles and venules to OPP lowering was compared between normocapnic and hypercapnic groups. RESULTS Average arterial carbon dioxide partial pressures were 36.9 ± 2.6 mmHg in normocapnic and 64.1 ± 5.9 mmHg in hypercapnic (P < .001) animals. In the normocapnic groups, blood pressure lowering and intraocular pressure elevation resulted in significant vasodilation of both arterioles and venules (P < .0001). In the hypercapnic groups, OPP lowering-induced vasodilation was significantly attenuated compared with the corresponding normocapnic groups (P < .0001 for both, two-way analysis of variance). CONCLUSION Hypercapnia significantly modified myogenic vascular autoregulation in response to OPP reduction.
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Turhan T, Aydın Ö, Ersahin Y. Neuroendoscopic surgery in empty ventricular system under continuous gas infusion experimental study of pressure changes and complications. Childs Nerv Syst 2012; 28:73-7. [PMID: 21935594 DOI: 10.1007/s00381-011-1586-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 09/07/2011] [Indexed: 11/30/2022]
Abstract
INTRODUCTION The most important limitations to endoscopic procedures in the ventricular system of the brain are due to the constraint of working inside a fluid. The evacuation of cerebrospinal fluid (CSF) from the ventricles is performed often in microsurgical interventions using a surgical microscope. This study aimed at studying the evacuation of CSF during neuroendoscopic surgery in animals while infusing gas to avoid ventricular collapse. MATERIALS AND METHODS Hydrocephalus was provoked in five adult New Zealand rabbits by intracisternal injection of kaolin. Endoscopic intervention was performed later; fluid was given as a continuous infusion at constant speed into the CSF for 3 min. In the next stage, CSF was evacuated from the ventricles, which were infused with gas at a stable rate for the same amount of time. The intracranial pressure (ICP) of the rabbits was recorded during both operations. The animals were sacrificed and the brain subjected to pathology examination at the end of the experiment. RESULTS Mean ICP value in the rabbit ventricle was 19.1 while working in CSF and 17.6 when working in air. The difference by a paired test was statistically significant for each individual rabbit except one. The ICP measurement, however, was never lower than the ambient pressure, even while working in continuous gas infusion. No epidural or subdural hematomas were found at autopsy. CONCLUSIONS Endoscopic surgery is feasible in a ventricular system that has been insufflated with gas after CSF has been evacuated. During the experiment, however, steadily diminishing ICP values were measured. As a result, new devices, such as small-flow insufflators able to perform sensitive pressure adjustments are needed.
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Affiliation(s)
- Tuncer Turhan
- Department of Neurosurgery, Ege University, Izmir, Turkey.
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Yamamoto Y, Kawaguchi M, Kurita N, Kakimoto M, Inoue S, Furuya H. Effects of xenon on ischemic spinal cord injury in rabbits: a comparison with propofol. Acta Anaesthesiol Scand 2010; 54:337-42. [PMID: 19735493 DOI: 10.1111/j.1399-6576.2009.02111.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Xenon has been shown to reduce cellular injury after cerebral ischemia. However, the neuroprotective effects of xenon on ischemic spinal cord are unknown. The authors compared the effects of xenon and propofol on spinal cord injury following spinal cord ischemia in rabbits. METHODS Thirty-two male New Zealand white rabbits were randomly assigned to one of three groups. In the xenon and propofol group, 70% of xenon and 0.8 mg/kg/min of propofol were administered 30 min before an aortic occlusion and maintained until the end of the procedure. The aortic occlusion was performed for 15 min. In the sham group, the aorta was not occluded. After an assessment of the hind limb motor function using the Tarlov score (0=paraplegia, 4=normal) at 48 h after reperfusion, gray and white matter injuries were evaluated based on the number of normal neurons in the anterior spinal cord and the percentage areas of vacuolation in the white matter, respectively. RESULTS In the xenon and propofol groups, the Tarlov score and the number of normal neurons were significantly lower than those in the sham group, whereas the percentage areas of vacuolation were similar among the three groups. There were no significant differences in Tarlov scores and the number of normal neurons between the xenon and the propofol groups. CONCLUSION The results indicated that 70% of xenon has no additional neuroprotective effects on ischemic spinal cord injury in rabbits compared with propofol.
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Affiliation(s)
- Y Yamamoto
- Department of Anesthesiology, Nara Medical University, Nara 634-8522, Japan
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Neuronal preconditioning by inhalational anesthetics: evidence for the role of plasmalemmal adenosine triphosphate-sensitive potassium channels. Anesthesiology 2009; 110:986-95. [PMID: 19352153 DOI: 10.1097/aln.0b013e31819dadc7] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND Ischemic preconditioning is an important intrinsic mechanism for neuroprotection. Preconditioning can also be achieved by exposure of neurons to K+ channel-opening drugs that act on adenosine triphosphate-sensitive K+ (K(ATP)) channels. However, these agents do not readily cross the blood-brain barrier. Inhalational anesthetics which easily partition into brain have been shown to precondition various tissues. Here, the authors explore the neuronal preconditioning effect of modern inhalational anesthetics and investigate their effects on K(ATP) channels. METHODS Neuronal-glial cocultures were exposed to inhalational anesthetics in a preconditioning paradigm, followed by oxygen-glucose deprivation. Increased cell survival due to preconditioning was quantified with the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction test. Recombinant plasmalemmal K(ATP) channels of the main neuronal type (Kir6.2/SUR1) were expressed in HEK293 cells, and the effects of anesthetics were evaluated in whole cell patch clamp recordings. RESULTS Both sevoflurane and the noble gas xenon preconditioned neurons at clinically used concentrations. The effect of sevoflurane was independent of K(ATP) channel activation, whereas the effect of xenon required the opening of plasmalemmal K(ATP) channels. Recombinant K(ATP) channels were activated by xenon but inhibited by halogenated volatiles. Modulation of mitochondrial K-ATP channels did not affect the activity of K(ATP) channels, thus ruling out an indirect effect of volatiles via mitochondrial channels. CONCLUSIONS The preconditioning properties of halogenated volatiles cannot be explained by their effect on K(ATP) channels, whereas xenon preconditioning clearly involves the activation of these channels. Therefore, xenon might mimic the intrinsic mechanism of ischemic preconditioning most closely. This, together with its good safety profile, might suggest xenon as a viable neuroprotective agent in the clinical setting.
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Rex S, Meyer P, Baumert JH, Rossaint R, Fries M, Büll U, Schaefer W. Positron emission tomography study of regional cerebral blood flow and flow–metabolism coupling during general anaesthesia with xenon in humans † †Declaration of Interest. The Department of Anaesthesiology has received funding from Messer-Griesheim GmbH, Business Unit Messer Medical, Krefeld, Germany. Br J Anaesth 2008; 100:667-75. [DOI: 10.1093/bja/aen036] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Yamamoto Y, Kawaguchi M, Kakimoto M, Inoue S, Furuya H. The Effects of Dexmedetomidine on Myogenic Motor Evoked Potentials in Rabbits. Anesth Analg 2007; 104:1488-92, table of contents. [PMID: 17513647 DOI: 10.1213/01.ane.0000261518.62873.91] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Dexmedetomidine is used in the perioperative management of patients, including as an intraoperative adjuvant. The effects of dexmedetomidine on myogenic motor evoked potentials (MEPs) remain undetermined. We conducted the present study to investigate the effects of dexmedetomidine on myogenic MEPs in rabbits. METHODS New Zealand white rabbits were used for the studies. First, to determine appropriate doses of dexmedetomidine as an adjunct for anesthesia in rabbits, the level of anesthesia was evaluated by testing the palpebral and limb withdrawal reflexes, and the reactions to ear pinching and tail clamp at 5, 25, 50, 100 microg/kg/h. Second, in 10 rabbits under ketamine and fentanyl anesthesia, myogenic MEPs in response to single pulse and a train-of-five pulses were recorded from the soleus muscle before, during, and after the administration of dexmedetomidine at 5, 25, and 50 microg/kg/h. RESULTS At 50 microg/kg/h of dexmedetomidine, palpebral reflex, limb reflex, and reaction to ear pinching were inhibited in >50% of animals, but the reaction to tail clamp was not reduced. Dexmedetomidine suppressed myogenic MEPs in a dose-dependent manner, but when multipulses were used for stimulation, myogenic MEPs could be recorded in all animals at 50 microg/kg/h. CONCLUSIONS As long as multipulse is used for stimulation, the recording of myogenic MEPs is feasible in rabbits under ketamine and fentanyl anesthesia during the administration of dexmedetomidine at doses that are an adjunct to anesthesia.
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Affiliation(s)
- Yuri Yamamoto
- Department of Anesthesiology, Nara Medical University, Kashihara, Nara, Japan
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Yamamoto Y, Kawaguchi M, Kakimoto M, Takahashi M, Inoue S, Goto T, Furuya H. The Effects of Xenon on Myogenic Motor Evoked Potentials in Rabbits: A Comparison with Propofol and Isoflurane. Anesth Analg 2006; 102:1715-21. [PMID: 16717315 DOI: 10.1213/01.ane.0000208992.83093.5c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We compared the effects of xenon on myogenic motor evoked potentials (MEPs) with those of propofol and isoflurane in rabbits under ketamine/fentanyl anesthesia. Thirty animals were randomly allocated to one of 3 groups (n = 10 in each group). In the propofol group, propofol was administered at a rate of 0.4 mg x kg(-1) x min(-1) (small) and 0.8 mg x kg(-1) x min(-1) (large). In the isoflurane group, isoflurane was administered at 0.8% (small) and 1.6% (large). In the xenon group, xenon was administered at 35% (small) and 70% (large). Myogenic MEPs in response to stimulation with single pulse and a train of 5 pulses were recorded from the soleus muscle before, during (at small and large doses), and after the administration of each anesthetic. With single-pulse stimulation, MEPs were recorded in 90% and 50% of animals at small and large doses of xenon, respectively, and MEP amplitudes in the xenon and isoflurane groups were significantly lower compared with those in the propofol group. With train pulse stimulation, MEPs were recorded in 100% and 90% of animals at small and large doses of xenon, respectively, and a reduction in MEP amplitudes by xenon was more prominent than by propofol but less than isoflurane at large doses. These results suggest that MEP recording may be feasible under xenon anesthesia if multipulse stimulation is used, although xenon has suppressive effects on myogenic MEPs.
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Affiliation(s)
- Yuri Yamamoto
- Department of Anesthesiology, Nara Medical University, Nara, Japan
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Abstract
Of all the inert gases, only xenon has considerable anaesthetic properties under normobaric conditions. Its very low blood/gas partition coefficient makes induction of and emergence from anaesthesia more rapid compared with other inhalational anaesthetics. In experimental and clinical studies the safety and efficiency of xenon as an anaesthetic has been demonstrated. Xenon causes several physiological changes, which mediate protection of the brain or myocardium. The use of xenon might therefore be beneficial in certain clinical situations, as in patients at high risk for neurological or cardiac damage.
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Affiliation(s)
- Benedikt Preckel
- Department of Anaesthesiology, Dusseldorf University Hospital, P.O. Box 10 10 07, D-40001 Düsseldorf, Germany.
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Abstract
PURPOSE OF REVIEW Xenon anaesthesia has recently been evaluated in large-scale clinical trials that have demonstrated xenon's safe and effective clinical profile. Despite the relatively high cost of xenon anaesthesia, xenon has clear clinical advantages over other current anaesthetics. RECENT FINDINGS Xenon possesses distinct neuroprotective and cardioprotective properties in addition to a favourable pharmacokinetic profile and analgesic effects. In addition, xenon exerts preconditioning effects in the heart and may offer postoperative, as well as intraoperative, cardio and neuroprotection. SUMMARY Further clinical trials are required to evaluate the role that xenon can play in the perioperative period.
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Affiliation(s)
- Robert D Sanders
- Department of Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College, London, UK
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Schmidt M, Marx T, Armbruster S, Reinelt H, Schirmer U. Effect of Xenon on elevated intracranial pressure as compared with nitrous oxide and total intravenous anesthesia in pigs. Acta Anaesthesiol Scand 2005; 49:494-501. [PMID: 15777297 DOI: 10.1111/j.1399-6576.2005.00609.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Xenon in low concentrations has been investigated in neuroradiology to measure cerebral blood flow (CBF). Several reports have suggested that inhalation of Xenon might increase intracranial pressure (ICP) by increasing the cerebral blood flow and blood volume, raising concerns about using Xenon as an anesthetic in higher concentrations for head-injured patients. A porcine study is presented in which the effects of inhaled 75% Xenon on elevated ICP, cerebral perfusion pressure and the efficacy of hyperventilation for ICP treatment were compared with nitrous oxide anesthesia and total intravenous anesthesia (TIVA). METHODS Twenty-one pentobarbital-anesthetized pigs (age: 12-16 weeks) were randomly assigned to three groups to receive either 4 h of Xenon-oxygen ventilation, nitrous oxide-oxygen ventilation or air-oxygen (75%/25%) ventilation, respectively. After instrumentation for parenchymal ICP measurement and ICP manipulation, an epidurally placed 6-F balloon catheter was inflated until a target ICP of 20 mmHg was achieved. After 4 h of anesthesia hyper- and hypoventilation maneuvers were performed and consecutive ICP and CBF changes were investigated. RESULTS Intracranial pressure and CBF increased significantly in the nitrous oxide group as compared with the controls. There was no increase of ICP or CBF in the Xenon or control group. Intracranial pressure changed in all three groups corresponding to hyper- and hypoventilation. CONCLUSIONS During Xenon anesthesia, elevated ICP is not increased further and is partially reversible by hyperventilation. Our study suggests that inhalation of 75% Xenon seems not to be contraindicated in patients with elevated ICP.
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Affiliation(s)
- M Schmidt
- Department Cardiac Anesthesia, University of Ulm, Ulm, Germany.
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Abstract
The 'noble' gases have been known to have anaesthetic properties for 50 years yet only recently has their application become a clinical reality. In this review we describe the preclinical and clinical studies that have led to a resurgence of interest in the use of the element xenon as an anaesthetic. Furthermore, we highlight specific areas where xenon demonstrates advantages over other anaesthetics, including safety, beneficial pharmacokinetics, cardiovascular stability, analgesia and neuroprotection.
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Affiliation(s)
- Robert D Sanders
- Department of Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College London, UK
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Affiliation(s)
- R D Sanders
- Department of Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College London, UK
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