Focal cerebral ischemia during anesthesia with etomidate, isoflurane, or thiopental: a comparison of the extent of cerebral injury

The Neuroprotective Effect of Thiopental on the Postoperative Neurological Complications in Patients Undergoing Surgical Clipping of Unruptured Intracranial Aneurysm: A Retrospective Analysis

Although thiopental improved neurological outcomes in several animal studies, there are still insufficient clinical data examining the efficacy of thiopental for patients undergoing surgical clipping of unruptured intracranial aneurysm (UIA). This study validated the effect of thiopental and investigated risk factors associated with postoperative neurological complications in patients undergoing surgical clipping of UIA. In total, 491 patients who underwent aneurysm clipping were included in this retrospective cohort study. Data regarding demographics, aneurysm characteristics, and use of thiopental were collected from electronic medical records. Propensity score matching and logistic regression analysis were used. After propensity score matching, the thiopental group showed a lower incidence of the postoperative neurological complications than non-thiopental group (5.5% vs. 17.1%, p = 0.001). In multivariate analysis, thiopental reduced the risk of postoperative neurological complications (odds ratio (OR) 0.26, 95% confidence interval (CI) 0.13 to 0.51, p < 0.001) while aneurysm size ≥ 10 mm (OR 4.48, 95% CI 1.69 to 11.87, p = 0.003), and hyperlipidemia (OR 2.24, 95% CI 1.16 to 4.32, p = 0.02) increased the risk of postoperative neurological complications. This study showed that thiopental was associated with the lower risk of neurological complications after clipping of UIA.

Sedation for Rapid Sequence Induction and Intubation of Neurologically Injured Patients

There are subtle physiologic and pharmacologic principles that should be understood for patients with neurologic injuries. These principles are especially true for managing patients with traumatic brain injuries. Prevention of hypotension and hypoxemia are major goals in the management of these patients. This article discusses the physiology, pitfalls, and pharmacology necessary to skillfully care for this subset of patients with trauma. The principles endorsed in this article are applicable both for patients with traumatic brain injury and those with spinal cord injuries.

Anesthesia in Experimental Stroke Research

Anesthetics have enabled major advances in development of experimental models of human stroke. Yet, their profound pharmacologic effects on neural function can confound the interpretation of experimental stroke research. Anesthetics have species-, drug-, and dose-specific effects on cerebral blood flow and metabolism, neurovascular coupling, autoregulation, ischemic depolarizations, excitotoxicity, inflammation, neural networks, and numerous molecular pathways relevant for stroke outcome. Both preconditioning and postconditioning properties have been described. Anesthetics also modulate systemic arterial blood pressure, lung ventilation, and thermoregulation, all of which may interact with the ischemic insult as well as the therapeutic interventions. These confounds present a dilemma. Here, we provide an overview of the anesthetic mechanisms of action and molecular and physiologic effects on factors relevant to stroke outcomes that can guide the choice and optimization of the anesthetic regimen in experimental stroke.

Neuroprotective effects of propofol, thiopental, etomidate, and midazolam in fetal rat brain in ischemia-reperfusion model

PURPOSE

The aim of this study was to investigate the neuroprotective effects of propofol, thiopental, etomidate, and midazolam as anesthetic drugs in fetal rat brain in the ischemia-reperfusion (IR) model.

METHODS

Pregnant rats of day 19 were randomly allocated into eight groups. Fetal brain ischemia was induced by clamping the utero-ovarian artery bilaterally for 30 min and reperfusion was achieved by removing the clamps for 60 min. In the control group, fetal rat brains were obtained immediately after laparotomy. In the sham group, fetal rat brains were obtained 90 min after laparotomy. In the IR group, IR procedure was performed. No treatment was given in the IR group. One milliliter intralipid solution, 40 mg/kg propofol, 3 mg/kg thiopental, 0.1 mg/kg etomidate, and 3 mg/kg midazolam was administered intraperitoneally in the vehicle group, propofol group, thiopental group, etomidate group, and midazolam group, respectively, 20 min before IR procedure. At the end of the reperfusion period, the whole brains of the fetal rats were removed for evaluation of thiobarbituric acid reactive substances and for examination by electron microscopy.

RESULTS

According to lipid peroxidation data, all the anesthetic drugs provide neuroprotection; however, ultrastructural findings and mitochondrial scoring confirms that only propofol and midazolam provides a strong neuroprotective effect.

CONCLUSIONS

Propofol and midazolam may be used to protect fetal brain in case of acute fetal distress and hypoxic injury as a first choice anesthetic drug in cesarean delivery.

Isoflurane induces endothelial apoptosis of the post-hypoxic blood-brain barrier in a transdifferentiated human umbilical vein endothelial cell model

Isoflurane is a popular volatile anesthetic agent used in humans as well as in experimental animal research. In previous animal studies of the blood-brain barrier (BBB), observations towards an increased permeability after exposure to isoflurane are reported. In this study we investigated the effect of a 2-hour isoflurane exposure on apoptosis of the cerebral endothelium following 24 hours of hypoxia in an in vitro BBB model using astrocyte-conditioned human umbilical vein endothelial cells (AC-HUVECs). Apoptosis of AC-HUVECs was investigated using light microscopy of the native culture for morphological changes, Western blot (WB) analysis of Bax and Bcl-2, and a TUNEL assay. Treatment of AC-HUVECs with isoflurane resulted in severe cellular morphological changes and a significant dose-dependent increase in DNA fragmentation, which was observed during the TUNEL assay analysis. WB analysis confirmed increases in pro-apoptotic Bax levels at 4 hours and 24 hours and decreases in anti-apoptotic Bcl-2 in a dose-dependent manner compared with the control group. These negative effects of isoflurane on the BBB after a hypoxic challenge need to be taken into account not only in experimental stroke research, but possibly also in clinical practice.

Comparative Study of Brain Protection Effect between Thiopental and Etomidate Using Bispectral Index during Temporary Arterial Occlusion

OBJECTIVE

This study was conducted to compare the effect of etomidate with that of thiopental on brain protection during temporary vessel occlusion, which was measured by burst suppression rate (BSR) with the Bispectral Index (BIS) monitor.

METHODS

Temporary parent artery occlusion was performed in forty one patients during cerebral aneurysm surgery. They were randomly assigned to one of two groups. General anesthesia was induced and maintained with 1.5-2.5 vol% sevoflurane and 50% N(2)O. The pharmacological burst suppression (BS) was induced by a bolus injection of thiopental (5 mg/kg, group T) or etomidate (0.3 mg/kg, group E) according to randomization prior to surgery. After administration of drugs, the hemodynamic variables, the onset time of BS, the numerical values of BIS and BSR were recorded at every minutes.

RESULTS

There were no significant differences of the demographics, the BIS numbers and the hemodynamic variables prior to injection of drugs. The durations of burst suppression in group E (11.1±6.8 min) were not statistically different from that of group T (11.1±5.6 min) and nearly same pattern of burst suppression were shown in both groups. More phenylephrine was required to maintain normal blood pressure in the group T.

CONCLUSION

Thiopental and etomidate have same duration and a similar magnitude of burst suppression with conventional doses during temporary arterial occlusion. These findings suggest that additional administration of either drug is needed to ensure the BS when the temporary occlusion time exceed more than 11 minutes. Etomidate can be a safer substitute for thiopental in aneurysm surgery.

Brain tissue oxygenation during dexmedetomidine administration in surgical patients with neurovascular injuries

Investigations in dogs have shown substantial dexmedetomidine (Dex)-induced reductions in cerebral blood flow (CBF) unaccompanied by reductions in cerebral metabolic rate (CMR). If this effect were to occur in humans in areas of injured brain in which CBF is already low, oxygen delivery might be critically impaired. The institutional use of brain PO2 monitoring during neurovascular surgery and the use of Dex as a component of the anesthetic allowed insight into this issue. Data from 5 neurovascular surgery patients, 2 for excision of arteriovenous malformations (AVMs), and 3 for intracranial aneurysm clipping were reviewed retrospectively. All had acute, lesion-related neurologic deficits. During general anesthesia with sufentanil and sevoflurane, with or without N2O, a parenchymal brain tissue PO2 (PbrO2) electrode was placed directly in the territory at risk from the pending neurosurgical intervention. After a stable PbrO2 value was achieved, Dex was administered by bolus (1 μg/kg over 10 min) and infusion (0.5 to 0.7 μg/kg/min). Mean arterial pressure (MAP), heart rate (HR), and PbrO2 were observed continuously for at least 25 minutes. Baseline PbrO2 values were relatively low (≤16 mm Hg) in 4 of the 5 patients, a pattern consistent with antecedent neurologic insult. In the 15 minutes after initiation of Dex administration, the pattern was one of a modest increase in Pbr02 (maximum 11.1%; P=0.0147) occurring roughly in parallel with a modest increase in MAP [maximum 3.5 mm Hg (4.5%); P=0.041]. HR did not change. Clinically significant reduction of PbrO2 did not occur before neurosurgical interventions. These observations provide no support for a direct cerebral vasoconstrictive effect of Dex in humans that is independent of any vasoconstriction that may occur as a consequence of Dex-induced reduction in CMR. At a minimum, any such effect was insufficient to have an adverse effect on oxygen delivery to brain parenchyma.

Sedation and analgesia in children with developmental disabilities and neurologic disorders

Sedation and analgesia performed by the pediatrician and pediatric subspecialists are becoming increasingly common for diagnostic and therapeutic purposes in children with developmental disabilities and neurologic disorders (autism, epilepsy, stroke, obstructive hydrocephalus, traumatic brain injury, intracranial hemorrhage, and hypoxic-ischemic encephalopathy). The overall objectives of this paper are (1) to provide an overview on recent studies that highlight the increased risk for respiratory complications following sedation and analgesia in children with developmental disabilities and neurologic disorders, (2) to provide a better understanding of sedatives and analgesic medications which are commonly used in children with developmental disabilities and neurologic disorders on the central nervous system.

Temperature management in studies of barbiturate protection from focal cerebral ischemia: systematic review and speculative synthesis

Our goal was to test the hypothesis that-given the barbiturates' novel ability to reduce brain temperature-the high prevalence of reports describing cerebral protection by barbiturates in animal models are, in part, the result of inadvertent cerebral hypothermia. We reviewed all published reports evaluating barbiturate protection in animal models of focal cerebral ischemia where functional or anatomic endpoints were assessed. Presence or absence of protection, and additionally the year of publication, were tabulated. Temperature monitoring was categorized as: (a) not monitored, (b) inadequately monitored (ie, temperature monitored, but not at appropriate sites or times), or (c) adequately monitored (brain or cranial temperature monitored at appropriate times, with or without core temperature). Twenty eight references published between 1974 and 2008 described 57 separate protocols. Cerebral protection by barbiturates was reported in 35 of 57 (61%) protocols. Temperature was not monitored in 10 protocols (18%), inadequately monitored in 32 (56%), and adequately monitored in 15 (26%). Although the majority (32 of 57; 56%) of the protocols were published before December 1987, none of these properly monitored temperature. In the protocols published in 1988 or later, 15 of 25 (60%) had proper temperature monitoring and 9 of the 15 (60%) reported protection by the barbiturates. Very few (ie, 15 of 57; 26%) protocols were capable of distinguishing between direct cerebral protection by the barbiturates and an artifactual, hypothermia-related, effect. However, among those protocols having proper temperature monitoring, there remained considerable evidence of barbiturate protection.

EFFECTS OF ISOFLURANE ON GLUTAMATE AND TAURINE RELEASES, BRAIN SWELLING AND INJURY DURING TRANSIENT ISCHEMIA AND REPERFUSION

The volatile anesthetic agent isoflurane was thought to provide neuroprotection against ischemic damage; however, this effect remains controversial. Using the middle cerebral artery occlusion model and intracerebral microdialysis, the authors monitored the variations of glutamate and taurine concentrations in the extra-cellular space in male rats anesthetized with pentobarbital or isoflurane. Brain injury and edema were evaluated 24 h after ischemia. Isoflurane prevented the ischemia-induced efflux of glutamate and reduced the release of taurine. No difference in the size of the brain lesions was observed with both anesthetics, and isoflurane induced the formation of a bigger brain edema and reduced taurine release. These results suggest that inhibiting glutamate release during ischemia may not be sufficient to improve brain outcome after transient ischemia.

Impact of anesthetic agents on cerebrovascular physiology in children

The role of the pediatric neuroanesthetist is to provide comprehensive care to children with neurologic pathologies. The cerebral physiology is influenced by the developmental stage of the child. The understanding of the effects of anesthetic agents on the physiology of cerebral vasculature in the pediatric population has significantly increased in the past decade allowing a more rationale decision making in anesthesia management. Although no single anesthetic technique can be recommended, sound knowledge of the principles of cerebral physiology and anesthetic neuropharmacology will facilitate the care of pediatric neurosurgical patients.

RODENT STROKE MODEL GUIDELINES FOR PRECLINICAL STROKE TRIALS (1ST EDITION)

Translational stroke research is a challenging task that needs long term team work of the stroke research community. Highly reproducible stroke models with excellent outcome consistence are essential for obtaining useful data from preclinical stroke trials as well as for improving inter-lab comparability. However, our review of literature shows that the infarct variation coefficient of commonly performed stroke models ranges from 5% to 200%. An overall improvement of the commonly used stroke models will further improve the quality for experimental stroke research as well as inter-lab comparability. Many factors play a significant role in causing outcome variation; however, they have not yet been adequately addressed in the Stroke Therapy Academic Industry Roundtable (STAIR) recommendations and the Good Laboratory Practice (GLP). These critical factors include selection of anesthetics, maintenance of animal physiological environment, stroke outcome observation, and model specific factors that affect success rate and variation. The authors have reviewed these major factors that have been reported to influence stroke model outcome, herewith, provide the first edition of stroke model guidelines so to initiate active discussion on this topic. We hope to reach a general agreement among stroke researchers in the near future with its successive updated versions.

Thiopental protects human T lymphocytes from apoptosis in vitro via the expression of heat shock protein 70

Barbiturates, which are used for the treatment of intracranial hypertension after severe head injury, have been associated with anti-inflammatory side effects. Although all barbiturates inhibit T-cell function, only thiobarbiturates markedly reduce the activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Various pharmacologic inhibitors of the NF-kappaB pathway are concomitant nonthermal inducers of the heat shock response (HSR), a cellular defense system that is associated with protection of cells and organs. We hypothesize that thiopental mediates cytoprotection by inducing the HSR. Human CD3(+) T lymphocytes were incubated with thiopental, pentobarbital, etomidate, ketamine, midazolam, or propofol. Human Jurkat T cells were transfected with small interfering RNA (siRNA) targeting heat 70-kDa shock protein (hsp 70) before thiopental incubation. Apoptosis was induced by staurosporine. DNA binding activity of HSF-1 was analyzed by electrophoretic mobility shift assay; mRNA expression of hsp27, -32, -70, and -90 was analyzed by Northern blot, and protein expression of hsp70 was analyzed by Western blot and flow cytometry after fluorescein isothiocyanate (FITC)-hsp70-antibody staining. Apoptosis was assessed by flow cytometry after annexin V-FITC or annexin V-phycoerythrin staining. Activity of caspase-3 was measured by fluorogenic caspase activity assay. Thiopental induced hsp27, -70, and -90 but not hsp32 mRNA expression as well as hsp70 protein expression. Thiopental dose-dependently activated the DNA binding activity of HSF-1, whereas other substances investigated had no effect. In addition, pretreatment with thiopental significantly attenuated staurosporine-induced apoptosis and caspase-like activity. Transfection with hsp70-siRNA before thiopental treatment reduced this attenuation. Thiopental specifically and differentially induces a heat shock response, and it mediates cytoprotection via the expression of hsp70 in human T lymphocytes.

Etomidate revisited

The major advantage of etomidate is its lack of cardiovascular side effects. In addition, etomidate is supposed to be neuroprotective. The side effects of etomidate include adrenal suppression and myocloni. A review of the recent literature on etomidate, its clinical use, its side effects and its mechanism of action was performed. Among others, major recent advances include a new drug preparation devoid of propylene glycol and its side effects, a new pretreatment technique that may reduce the incidence of myocloni, and the identification of its site of action in the central nervous system.

Inhalational anesthetics as neuroprotectants or chemical preconditioning agents in ischemic brain

This review will focus on inhalational anesthetic neuroprotection during cerebral ischemia and inhalational anesthetic preconditioning before ischemic brain injury. The limitations and challenges of past and current research in this area will be addressed before reviewing experimental and clinical studies evaluating the effects of inhalational anesthetics before and during cerebral ischemia. Mechanisms underlying volatile anesthetic neuroprotection and preconditioning will also be examined. Lastly, future directions for inhalational anesthetics and ischemic brain injury will be briefly discussed.

Neuroanesthesiology review--2006

In this article, we will provide a review of the 2006 literature of interest to those readers who provide perioperative care to patients with neurologic disease. This evaluation of the literature is not intended to be comprehensive, nor were systematic criteria used to include or exclude articles. Instead, the authors attempted to highlight those articles of greatest clinical relevance or those that provided unique insights into the physiology, pharmacology, and pathomechanisms of neurologic function for practicing clinicians and clinician-investigators. This article focuses on intracranial hemorrhage, anesthetic considerations in neurosurgical patients, cerebral hemodynamics, electrophysiologic monitoring, neuroprotection, and traumatic brain injury.

Anesthetic-mediated protection/preconditioning during cerebral ischemia

Cerebral ischemia is a multi-faceted neurodegenerative pathology that causes cellular injury to neurons within the central nervous system. In light of the underlying mechanisms being elucidated, clinical trials to find possible neuroprotectants to date have failed, thus highlighting the need for new putative targets to offer protection. Recent evidence has clearly shown that anesthetics can confer significant protection and or induce a preconditioning effect against cerebral ischemia-induced injury. This review will focus on the putative protection/preconditioning that is afforded by anesthetics, their possible interaction with GABA(A) and glutamate receptors and two-pore potassium channels. In addition, the interaction with inflammatory, apoptotic and underlying molecular (particularly immediately early genes and inducible nitric oxide synthase etc) pathways, the activation of K(ATP) channels and the ability to provide lasting protection will also be addressed.

The Dose-Dependent Effects of Isoflurane on Outcome from Severe Forebrain Ischemia in the Rat

Isoflurane improves outcome against cerebral ischemia in the rat. However, the optimal neuroprotective concentration has not been defined. We examined the effects of different isoflurane concentrations on outcome from severe forebrain ischemia in the rat. Fasted rats were subjected to 0.5, 1.0, 1.5, 2.0, or 2.5 minimum alveolar concentration (MAC) isoflurane during 10 min bilateral carotid occlusion plus systemic hypotension. Each isoflurane concentration was administered only before ischemia. Arterial blood pressure was not pharmacologically manipulated. After ischemia, the anesthetic regimen was changed to fentanyl/nitrous oxide and maintained for 2 h. Pericranial temperature was maintained normothermic during the experiment. Neuromotor score, % dead hippocampal CA1 neurons, and cortical injury were measured 5 days postischemia. Preischemic arterial blood pressure decreased as MAC was increased. Animals administered >1.0 MAC frequently exhibited postischemic seizures resulting in increased mortality. There was no difference among MAC conditions for % dead CA1 neurons (93 approximately 95%). In the cortex, neuronal necrosis was less severe with 0.5 MAC and 1.0 MAC isoflurane relative to >1.0 MAC values. The neuromotor score in the 1.0 MAC isoflurane group was superior to the 2.5 MAC group. Dose-dependent effects of preischemic administration of isoflurane on histologic and behavioral outcome after severe forebrain ischemia were observed. Isoflurane MAC values <1.5 provided superior overall outcome relative to larger isoflurane concentrations.

Effects of intravenous anesthetics on the activity of glutamate transporter EAAT3 expressed in Xenopus oocytes: Evidence for protein kinase C involvement

We investigated the effects of the intravenous anesthetics, thiopental, etomidate and ketamine, on the activity of one type of glutamate transporters, EAAT3 (excitatory amino acid transporter type 3). Rat EAAT3 was expressed in Xenopus oocytes by injection of its mRNA. Using two-electrode voltage clamp, membrane currents were recorded after the application of L-glutamate (30 microM) in the presence or absence of various concentrations of the anesthetics. Thiopental (0.3-30 microM) and ketamine (3-1000 microM) did not affect EAAT3 activity. Etomidate decreased EAAT3 activity in a concentration-dependent manner (0.10-10 microM). Etomidate at 1 microM significantly decreased the Vmax, but not the Km of EAAT3 for glutamate. Chelerythrine, a protein kinase C (PKC) inhibitor, significantly decreased EAAT3 activity, however, there were no statistical differences among the chelerythrine, etomidate or chelerythrine plus etomidate groups. Likewise, the combination of staurosporine, another PKC inhibitor, and etomidate did not decrease the responses further compared with staurosporine or etomidate alone. Phorbol-12-myrisate-13-acetate, a PKC activator, abolished etomidate-induced decrease in EAAT3 activity. Since our results showed that thiopental and ketamine did not affect EAAT3 activity significantly, EAAT3 may not be a target for their anesthetic effects. Our results also suggest that etomidate, possibly via PKC, decreased EAAT3 activity at clinically relevant concentrations.

New cerebral protection strategies

PURPOSE OF REVIEW

This article presents an overview of the most recent and important strategies to reduce secondary brain damage.

RECENT FINDING

There is currently no magic bullet available to protect the brain after neuronal injury. This is related to the complex pathophysiology of cerebral ischemia, which makes it unlikely that a single pharmacological intervention results in sustained neuroprotection. Analyses of clinical studies reveal that acute physiologic derangements (e.g. fever, hypertension and hypotension, hypoxemia, hypercapnia, hyperglycemia) are the most important predictors of unfavorable outcome after brain injury and have to be treated. The effectiveness of anesthetic agents to extend the ischemic tolerance of neurons has been demonstrated in experimental settings, but such benefits have not been demonstrated in humans. The effectiveness of osmodiuretics to decrease elevated intracranial pressure, a factor with relevance to outcome, has been demonstrated. Infusion of magnesium in patients with subarachnoidal hemorrhage can reduce the occurrence of delayed ischemia caused by cerebrovascular spasm. The prophylactic administration of glucocorticoids should be avoided. While the positive effects of chronic administration of statins to reduce the incidence of stroke has been demonstrated in several clinical studies, the protective effect of acute administration of statins after a cerebral insult has do be defined.

SUMMARY

Control of physiological variables, avoidance of hyperthermia, intensive control of plasma glucose concentrations, use of anesthetic agents and osmodiuretics to control intracranial hypertension and the possible prophylactic administration of magnesium in patients at risk of vasospasm and of statins in patients with cerebrovascular risk factors are currently the most important strategies to reduce neuronal injury.

Pre- or Postinsult Administration of Lidocaine or Thiopental Attenuates Cell Death in Rat Hippocampal Slice Cultures Caused by Oxygen-Glucose Deprivation

Lidocaine and thiopental improve recovery when administrated during hypoxia and ischemia; however, the effect of pre- or postinsult treatment alone is unknown. We applied either lidocaine or thiopental to hippocampal slice cultures from 20-day-old rats either before or after 10 min of oxygen-glucose deprivation (OGD). Propidium iodide (PI) fluorescence was used as an indicator of neuronal death for 7 days after OGD. OGD-induced neuronal death, in both the Cornus Ammonis 1 (CA1) and the dentate gyrus regions, peaked the first day after ischemia. Preinsult administration of either lidocaine (10, 100 microM) or thiopental (250, 600 microM) significantly reduced the damage measured on the first and second days after OGD; these drugs also significantly decreased the summed daily post-OGD PI fluorescence in both regions. Postinsult administration of lidocaine (10, 100 microM) or thiopental (250, 600 microM) significantly decreased the PI fluorescence on the first day after OGD; postinsult administration of these drugs also attenuated the summed daily post-OGD PI. These data indicate that the administration of lidocaine or thiopental either before or directly after OGD reduced neuronal damage in this in vitro model of cerebral ischemia. Postischemic administration is frequently the first opportunity for treatment.

IMPLICATIONS

Lidocaine or thiopental applied either 10 min before or 10 min directly after oxygen-glucose deprivation reduced neuronal cell death in rat hippocampal slice cultures. Postinsult administration is often the first opportunity for treatment after stroke; lidocaine and thiopental reduced damage caused by oxygen-glucose deprivation, an in vitro model of stroke.

The Role of Nitric Oxide Synthase Inhibition in the Adverse Effects of Etomidate in the Setting of Focal Cerebral Ischemia in Rats

We evaluated the effect of N(G)-nitro-L-arginine-methyl-ester (l-NAME, a nitric oxide synthase [NOS] inhibitor) and L-arginine (nitric oxide substrate) on cerebral mitochondrial dysfunction (hereafter referred to as "injury") after temporary middle cerebral artery occlusion (MCAo) during halothane or etomidate anesthesia in spontaneously hypertensive rats. Sixty minutes before MCAo, rats were randomized to 1 of 5 regimens (n = 8 per group): h/control, 1.2 minimum alveolar anesthetic concentration of halothane; h/L-NAME, 1.2 minimum alveolar anesthetic concentration of halothane and L-NAME (30 mg/kg); etomidate, an electroencephalographic (EEG) burst suppression dose of etomidate; e/L-NAME, an EEG burst suppression dose of etomidate and L-NAME (30 mg/kg); or e/L-NAME/arg, an EEG burst suppression dose of etomidate, L-NAME (30 mg/kg), and L-arginine (bolus of 300 mg/kg with an infusion at 35 mg x kg(-1) x min(-1)). After 180 min of MCAo and 120 min of reperfusion, volume of injury was determined using 2,3,5-triphenytetrazolium stain. Injury volume (mm(3), mean +/- sd) was larger in the etomidate group (153 +/- 17) than the halothane anesthetized h/control group (93 +/- 16) (P < 0.05) but did not differ between the e/L-NAME (162 +/- 17) and h/L-NAME groups (155 +/- 26). Injury volume in the e/L-NAME/arg group (88 +/- 15) was not different from the h/control group (93 +/- 16) and was less than that in either the etomidate or the e/L-NAME groups (P < 0.05). The data reproduce our previous observation that, relative to a halothane-anesthetized control state, etomidate has an adverse effect on ischemic injury in the setting of temporary focal cerebral ischemia. Prior inhibition of NOS with L-NAME resulted in no difference in the volume of injury between groups receiving etomidate or halothane (162 +/- 17 versus 155 +/- 26). Administration of a large dose of L-arginine prevented the adverse effect of etomidate. The data were obtained after only 2 h of reperfusion and therefore cannot be construed as representative of final neurologic outcome. They nonetheless suggest that etomidate produces an adverse effect on mitochondrial function early in the course of focal cerebral ischemia, in part, by inhibition of NOS.

Desflurane affords greater protection than halothane against focal cerebral ischaemia in the rat

BACKGROUND

We studied the potential neuroprotective effects of halothane and desflurane, compared with the awake state, on infarct size following 2 h of intraluminal middle cerebral artery occlusion (MCAo) and 22 h of reperfusion.

METHODS

Male Sprague-Dawley rats were anaesthetized with desflurane or halothane, intubated, and mechanically ventilated. Mean arterial pressure (MAP), blood gases, and pH were controlled. Body temperature was maintained at 37.5-38 degrees C. Animals were assigned to one of four groups according to the anaesthetic type (halothane or desflurane) and the duration of anaesthesia: "short-duration", during the preparation only; "long-duration", during both preparation and ischaemia. Twenty-four hours after MCAo, infarcts were visualized by staining with 2,3,5-triphenyltetrazolium chloride. Two additional groups of rats were subjected to the same protocol as that of long-duration halothane and long-duration desflurane with additional pericranial temperature measurements made.

RESULTS

Physiological parameters were comparable between the groups but MAP was higher (P<0.0001) in the short-duration groups. In the short-duration groups, cerebral infarct volumes were not significantly different between anaesthetics (short-duration halothane: 288 (61) mm(3), mean (SD); short-duration desflurane: 269 (71) mm(3), P>0.56). Compared with the awake state (short-duration groups), halothane and desflurane significantly reduced infarct volumes (long-duration halothane: 199 (54) mm(3), P<0.0047 vs short-duration halothane; long-duration desflurane: 121 (55) mm(3), P<0.0001 vs short-duration desflurane). The mean infarct volume in the long-duration desflurane group was significantly lower than that in the long-duration halothane group (P<0.0053). Pericranial temperatures were similar in the desflurane and halothane long-duration groups (P>0.17).

CONCLUSIONS

In rats, desflurane-induced neuroprotection against focal cerebral ischaemia was greater than that conferred by halothane.

Release of neuron-specific enolase and S100 after implantation of cardioverters/defibrillators

OBJECTIVE

Repeated induction of ventricular fibrillation with ensuing alterations in electroencephalogram and jugular venous oxygen saturation is common practice during insertion of transvenous implantable cardioverters/defibrillators. We investigated whether these functional changes are also associated with cerebral injury.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

We studied 45 patients undergoing implantable cardioverter/defibrillator insertion. Eleven patients with cardiac pacemaker implantation, which was performed in the same manner yet without the necessity to induce ventricular fibrillation, served as controls.

MEASUREMENTS AND MAIN RESULTS

Serum neuron-specific enolase and S100 were determined before, immediately postoperatively, and 2 hrs postoperatively. In a randomly composed subgroup, neuron-specific enolase was also determined 6 and 24 hrs after surgery. Implantable cardioverter/defibrillator patients only showed an increase of both markers postoperatively. Median neuron-specific enolase values climbed from a preoperative 9.9 to 12.3 and 14.4 microg/L at 2 and 24 hrs after surgery, respectively. This increase was associated with the number of shocks and the cumulative time in circulatory arrest. The highest median S100 level (0.075 microg/L) was reached 2 hrs after the procedure. Neuron-specific enolase and S100 were extremely elevated (13.7 and 0.970 microg/L, respectively) in one patient after an extended episode of ventricular fibrillation. Plasma hemoglobin levels were in the normal range in implantable cardioverter/defibrillator patients throughout the observation period.

CONCLUSIONS

Apparently, even brief successive periods of global cerebral ischemia cause neuronal damage without obvious severe neurologic deficits. However, they may be related to subtle postoperative neurologic or cognitive dysfunctions that a number of implantable cardioverter/defibrillator patients exhibit after implantation.

Acute intraoperative cerebral oedema: are current therapies evidence based?

Acute intraoperative ischaemic cerebral oedema following torrential haemorrhage from the left intracranial internal carotid artery occurred during resection of a recurrent middle cranial fossa meningioma. A series of immediate anaesthetic interventions was effective in reducing brain oedema, allowed for surgical haemostasis, and resulted in no permanent sequelae to patient outcome. A review of the literature indicates that direct evidence for the efficacy of extremely early interventions as described in this case report is lacking and must be extrapolated from other brain injury models.

Anesthetic technique influences brain temperature, independently of core temperature, during craniotomy in cats

Because anesthetic technique has the potential to dramatically affect cerebral blood flow and metabolism (two determinants of brain thermoregulation), we tested the hypothesis that, after craniotomy, anesthetic technique would influence brain temperature independent of core temperature. Twenty-one cats (2.7 +/- 0.4 kg; mean +/- SD) undergoing a uniform right parasagittal craniotomy received 1) halothane 1.5% end-expired and normocapnia (HN), 2) halothane 1.5% and hypocapnia (HH), or 3) large-dose pentobarbital and normocapnia (PN) (n = 7 per group). Heating devices initially maintained core and right subdural normothermia (38.0 degrees C). Thereafter, cranial heating was discontinued. Brain-to-core temperature gradients during the 3 h study were greatest in the right subdural area, averaging -2.5 degrees C +/- 0.9 degrees C in HN, -2.5 degrees C +/- 0.8 degrees C in HH, and -4.1 degrees C +/- 1.1 degrees C in PN. Gradients within the unexposed left subdural area and in the right cortex 0.5 and 1.0 cm below the brain surface were -0.8 degrees C +/- 0.5 degrees C to -1.1 degrees C +/- 0.6 degrees C for both HN and HH but were twice this amount in PN (-1.9 degrees C +/- 0.5 degrees C to -2.1 degrees C +/- 0.7 degrees C) (P < 0.05 for PN versus HN and HH). Deep barbiturate anesthesia can reduce brain temperature independently of core temperature, presumably by reducing the metabolic rate and associated brain heat production. The magnitude is sufficient to augment any direct cerebroprotective properties of the barbiturates.

IMPLICATIONS

Deep barbiturate anesthesia reduced brain temperature independently of body temperature in cats and significantly more than the reduction seen with halothane anesthesia. The magnitude of temperature reduction was sufficient to account for cerebral protection by barbiturates independently of any other properties of the drug.

Sevoflurane improves electrophysiological recovery of rat hippocampal slice CA1 pyramidal neurons after hypoxia

Sevoflurane is a volatile anesthetic agent that reduces cerebral metabolism and thereby may reduce neuronal damage during energy deprivation. We have examined the effect of sevoflurane on hypoxic neuronal damage in rat hippocampal slices. Slices were subjected to 0%, 2%, or 4% sevoflurane 10 minutes before, during, and 10 minutes after hypoxia. The Schaffer collateral pathway was stimulated every 10 seconds and the evoked population spike recorded in the CA1 pyramidal cell region throughout the experiment. During hypoxia, the postsynaptic evoked response was blocked. The time until the blockade of this response in the 0% sevoflurane group was 158 seconds. Sevoflurane (4%) significantly delayed the loss of the evoked response during hypoxia (242 seconds). The percent recovery of the postsynaptic population spike was calculated by dividing the size of the response 120 minutes after hypoxia by its prehypoxic, presevoflurane amplitude. There was no recovery of the population spike in the 0% sevoflurane group 120 minutes after the end of 5 minutes of hypoxia (6 +/- 6%); there was significantly better recovery after 5 minutes of hypoxia in the sevoflurane (4%) treated group (40 +/- 9%). A lower concentration of sevoflurane (2%) delayed the loss of evoked response during hypoxia (191 seconds), but it did not significantly affect recovery of the population spike after hypoxia (7 +/- 7%). Hypoxia irreversibly damages electrophysiologic activity. A high, but clinically usable, concentration of sevoflurane increases the time during hypoxia until the postsynaptic evoked response is blocked and improves recovery of this response after 5 minutes of hypoxia.

Cerebral protection with thiopentone during combined carotid endarterectomy and clipping of intracranial aneurysm

We report a case of carotid endarterectomy and clipping of an ipsilateral internal carotid artery aneurysm in a patient with complete contralateral carotid stenosis. The patient developed an ischaemic electroencephalographic (EEG) tracing on temporary carotid clamping and bypass shunt was contraindicated. We used thiopentone titrated to EEG burst suppression for pharmacological cerebral protection during the subsequent prolonged carotid clamp necessary for carotid endarterectomy. We review the use of thiopentone for this purpose, in particular the evidence for efficacy, mechanism of action and optimal dosage and timing of administration.

Thiopentone and methohexital, but not pentobarbitone, reduce early focal cerebral ischemic injury in rats

PURPOSE

Although barbiturates are considered to be cerebral protectants, little is known regarding the relative efficacy of different barbiturates to reduce ischemic brain injury. In a model of middle cerebral artery occlusion (MCAo), we compared the relative effects of 1.0 and 0.4 burst-suppression doses of thiopentone, methohexital, and pentobarbitone on cerebral infarct.

METHODS

During isoflurane anesthesia, MCAo was achieved via a temporal craniotomy. Thirty minutes before MCAo the rats were randomized to receive one of the following which was maintained throughout the study. Halothane (n=20)-1.2 MAC halothane, thiopentone (n=20), methohexital (n=20), or pentobarbitone (n=20). The first ten animals in each barbiturate group received the respective barbiturate in a dose sufficient to maintain burst-suppression of the electroencephalogram (3-5 bursts x min(-1)). The subsequent ten animals in each barbiturate group received 40% of the burst-suppression dose. After 180 min of MCAo and 120 min of reperfusion, cerebral injury was assessed.

RESULTS

For the burst-suppression animals, injury volume (mm3, mean +/- SD) was less in the thiopentone group (88 +/- 14) than the halothane (133 +/- 17), methohexital (126 +/- 19), or pentobarbitone (130 +/- 17) groups (P <0.05). For 0.4 burst-suppression animals, injury volume was less for the methohexital group (70 +/- 22) than the halothane (124 +/- 24), thiopentone (118 +/- 15), or pentobarbitone (121 +/- 20) groups (P <0.05).

CONCLUSIONS

These data are inconsistent with the longstanding assumption that electrophysiologically comparable doses of the various classes of barbiturates have equivalent protective efficacy. They in turn suggest that mechanisms other than, or at least in addition to, metabolic suppression may contribute to the protective effect of barbiturates.

Anaesthetic considerations for patients undergoing hypothermic cardiopulmonary bypass for complex neurovascular lesions: case presentation and review

The anaesthetic management of a 38-year-old woman having excision of a meningioma involving the superior sagittal sinus is described. The procedure was performed using low flow moderate hypothermic cardiopulmonary bypass with central cannulation. Relevant literature is reviewed.

Monitoring in neuroanaesthesia: update of clinical usefulness

The aim of specific monitoring in neuroanaesthesia is to detect, as quickly as possible, intraoperative ischaemic insults so that the brain and the spinal cord may be protected from harmful and frequently inevitable events due to the type of surgery, patient positioning, haemodynamic changes or any intercurrent event. New monitors are being introduced into the operating theatre, but only a few are considered to be an absolute standard of care in neurosurgery, e.g. facial nerve monitoring for surgery of acoustic neuromas and recording of evoked potentials during repair of scoliosis. In the past decade, new monitoring devices have moved from the experimental stage to the operating theatre and although most are still in a phase of technological development and/or definition of their field of applicability they are being used as guides for clinical practice in those instances where cerebral well-being might be impaired. The metabolic consequences of hyperventilation, pharmacological electroencephalogram burst suppression, hypothermia, etc. can now be assessed in the operating theatre. Non-invasive monitoring is being rapidly integrated into our daily work because of its lack of secondary effects. Nevertheless, each new development is regarded as an addition rather than as a substitute for existing equipment. The perfect combination of monitors to provide essential information during an individual surgical procedure to influence a better patient outcome, is still uncertain and needs extensive clinical research.

Avaliação da isquemia cerebral pela respiração mitocondrial: modelo experimental

A isquemia cerebral acontece em várias doenças. Um dos fatores críticos para a recuperação de um paciente é a duração do processo isquêmico. A atividade cerebral depende do suprimento de energia, isto sugere que o estudo da função mitocondrial pode ser utilizado para a avaliação do dano neuronal. O objetivo deste trabalho foi o de estudar a respiração mitocondrial pela oclusão da artéria cerebral média esquerda pela técnica do fio intraluminal. Ratos da raça Wistar foram subdivididos em 4 grupos: controle e 15, 30 e 60 minutos de oclusão. Os resultados mostraram que não há diferença estatisticamente significativa entre o grupo de 15 minutos e o grupo controle. O grupo de 30 minutos teve diminuição do estado III da respiração mitocondrial comparado com o grupo controle. O grupo de 60 minutos teve diminuição dos estados III e IV comparados com o grupo controle. A respiração mitocondrial permitiu uma avaliação efetiva e precoce do processo isquêmico focal no cérebro do rato.

No additional neuroprotection provided by barbiturate-induced burst suppression under mild hypothermic conditions in rats subjected to reversible focal ischemia

OBJECT

Mild-to-moderate hypothermia is increasingly used for neuroprotection in humans. However, it is unknown whether administration of barbiturate medications in burst-suppressive doses-the gold standard of neuroprotection during neurovascular procedures-provides an additional protective effect under hypothermic conditions. The authors conducted the present study to answer this question.

METHODS

Thirty-two Sprague-Dawley rats were subjected to 90 minutes of middle cerebral artery occlusion and randomly assigned to one of four treatment groups: 1) normothermic controls; 2) methohexital treatment (burst suppression); 3) induction of mild hypothermia (33 degrees C); and 4) induction of mild hypothermia plus methohexital treatment (burst suppression). Local cerebral blood flow was continuously monitored using bilateral laser Doppler flowmetry and electroencephalography. Functional deficits were quantified and recorded during daily neurological examinations. Infarct volumes were assessed histologically after 7 days. Methohexital treatment, mild hypothermia, and mild hypothermia plus methohexital treatment reduced infarct volumes by 32%, 71%, and 66%, respectively, compared with normothermic controls. Furthermore, mild hypothermia therapy provided the best functional outcome, which was not improved by additional barbiturate therapy.

CONCLUSIONS

The results of this study indicate that barbiturate-induced burst suppression is not required to achieve maximum neuroprotection under mild hypothermic conditions. The magnitude of protection afforded by barbiturates alone appears to be modest compared with that provided by mild hypothermia.

Pentobarbital inhibits apoptosis in neuronal cells

OBJECTIVE

Previous reports have demonstrated that barbiturates have a protective effect against cerebral ischemia, although the mechanisms are incompletely understood. Recently, it has been suggested that apoptosis is involved in ischemic neuronal death. This study examined the effect of pentobarbital on neuronal apoptosis.

DESIGN

Randomized, controlled, prospective study.

SETTING

University research laboratory.

SUBJECTS

PC12 cells derived from rat pheochromocytoma as a model of neuronal tissue.

INTERVENTIONS

Apoptosis was induced by depriving serum from the cell culture medium. Effect of pentobarbital (0.5, 5, 50 microg/mL) was evaluated.

MEASUREMENTS AND MAIN RESULTS

First, electrophoresis of DNA and fluorescence microscopic examination were performed to ascertain whether apoptosis was really induced after serum deprivation in our cells. Second, the effect of pentobarbital on cytotoxicity (evaluated by a leakage assay of lactic dehydrogenase) was evaluated. Third, the percentage of apoptotic cells was calculated by measuring cellular DNA content with flow cytometry. Calculation of the percentage of apoptotic cells was based on cumulative frequency curves of the appropriate DNA histograms. DNA electrophoresis exhibited a typical ladder pattern from the first day after the induction of apoptosis. The cells with chromatin condensation and/or fragmentation increased day by day after depriving serum in fluorescence microscopic examination. Four days after the induction of apoptosis, cytotoxicity without pentobarbital was 53.9 +/- 24.3% (mean +/- SD). Pentobarbital significantly inhibited cell death in a dose-dependent fashion. The percentage of apoptotic cells without pentobarbital was 94.9 +/- 6.3% 4 days after the induction of apoptosis. The treatment with 50 microg/mL pentobarbital significantly decreased the percentage of apoptotic cells to 61.8 +/- 21.3%.

CONCLUSIONS

Our data indicate that pentobarbital inhibits apoptosis induced by serum deprivation in PC12 cells.

Reproducibility of cerebral cortical infarction in the wistar rat after middle cerebral artery occlusion

Although middle cerebral artery (MCA) occlusion in the rat is often used to study focal cerebral ischemia, the model of ischemia affects the size and reproducibility of infarction. The purpose of this experiment was to methodically examine different preparations to determine the optimum focal cerebral ischemia model to produce a reproducible severe ischemic injury. Eighty-two Wistar rats underwent either 1 hour, 3 hour, or permanent MCA occlusion combined with no, unilateral, or bilateral common carotid artery artery (CCA) occlusion. Three days after ischemia, the animals were prepared for tetrazolium chloride assessment of infarction size. One-hour MCA occlusion produced a coefficient of variation (CV) of 200% with an infarction volume of 20.3+/-10.5 mm(3). Adding unilateral or bilateral CCA occlusion resulted in a CV of 134% and 101%, respectively. Three-hour MCA occlusion combined with bilateral CCA occlusion decreased the CV to 58% with a cortical infarction volume of 82.6+/-12.1 mm(3), P<05, compared with 1-hour MCA occlusion with or without CCA occlusion. Permanent MCA occlusion combined with 3 hours of bilateral CCA occlusion resulted in a CV of 47% with a cortical infarction volume of 89.6+/-16.0 mm(3). These results indicate that 3-hour MCA occlusion combined with bilateral CCA occlusion provide consistently a large infarction volume after temporary focal cerebral ischemia.

Thiopental attenuates hypoxic changes of electrophysiology, biochemistry, and morphology in rat hippocampal slice CA1 pyramidal cells

BACKGROUND AND PURPOSE

Thiopental has been shown to protect against cerebral ischemic damage; however, it has undesirable side effects. We have examined how thiopental alters histological, physiological, and biochemical changes during and after hypoxia. These experiments should enable the discovery of agents that share some of the beneficial effects of thiopental.

METHODS

We made intracellular recordings and measured ATP, sodium, potassium, and calcium concentrations from CA1 pyramidal cells in rat hippocampal slices subjected to 10 minutes of hypoxia with and without 600 micromol/L thiopental.

RESULTS

Thiopental delayed the time until complete depolarization (21+/-3 versus 11+/-2 minutes for treated versus untreated slices, respectively) and attenuated the level of depolarization at 10 minutes of hypoxia (-33+/-6 versus -12+/-5 mV). There was improved recovery of the resting potential after 10 minutes of hypoxia in slices treated with thiopental (89% versus 31% recovery). Thiopental attenuated the changes in sodium (140% versus 193% of prehypoxic concentration), potassium (62% versus 46%), and calcium (111% versus 197%) during 10 minutes of hypoxia. There was only a small effect on ATP (18% versus 8%). The percentage of cells showing clear histological damage was decreased by thiopental (45% versus 71%), and thiopental improved protein synthesis after hypoxia (75% versus 20%).

CONCLUSIONS

Thiopental attenuates neuronal depolarization, an increase in cellular sodium and calcium concentrations, and a decrease in cellular potassium and ATP concentrations during hypoxia. These effects may explain the reduced histological, protein synthetic, and electrophysiological damage to CA1 pyramidal cells after hypoxia with thiopental.

Thiopental and desflurane treatment for brain protection

OBJECTIVE

Thiopental produces cerebral metabolic depression and cerebral vasoconstriction. However, the effect of thiopental on brain tissue oxygen pressure (PO2), carbon dioxide pressure, and pH is not known. In a prospective study, we measured brain tissue gases and pH during thiopental or desflurane treatment that was administered for brain protection during brain artery occlusion.

METHODS

After institutional review board approval, 20 patients undergoing craniotomies for cerebrovascular surgery were tested; 10 were randomized to receive thiopental and 10 to receive desflurane. After each craniotomy, a Neurotrend probe (Diametrics Medical, Minneapolis, MN) was inserted to measure tissue PO2, carbon dioxide pressure, and pH in a tissue region at risk to develop ischemia during temporary brain artery occlusion. Thiopental or desflurane was administered to produce burst suppression of electroencephalography, and then temporary artery occlusion was performed during aneurysm or extracerebral-to-intracerebral bypass surgery.

RESULTS

Thiopental produced no change in tissue gases or pH, but temporary artery clipping in thiopental-treated patients decreased PO2 30% (P < 0.05). Desflurane increased PO2 70% (P < 0.05), and tissue oxygenation remained elevated during temporary artery occlusion. Tissue pH did not decrease in either group during temporary brain artery occlusion.

CONCLUSION

Thiopental has a metabolically neutral effect on brain tissue gases and pH, even though it is known to decrease cerebral oxygen consumption. The metabolic depressant and vasodilator effects of desflurane enhance tissue oxygenation and attenuate tissue PO2 reductions produced by artery occlusion. Both thiopental and desflurane inhibit ischemic lactic acidosis and decreases in pH.