Cranioplasty with autologous cryopreserved bone after decompressive craniectomy: complications and risk factors for developing surgical site infection.

BACKGROUND: Renewed interest has developed in decompressive craniectomy, and improved survival is shown when this treatment is used after malignant middle cerebral artery infarction. The aim of this study was to investigate the frequency and possible risk factors for developing surgical site infection (SSI) after delayed cranioplasty using autologous, cryopreserved bone. METHODS: This retrospective study included 74 consecutive patients treated with decompressive craniectomy during the time period May 1998 to October 2010 for various non-traumatic conditions causing increased intracranial pressure due to brain swelling. Complications were registered and patient data was analyzed in a search for predictive factors. RESULTS: Fifty out of the 74 patients (67.6 %) survived and underwent delayed cranioplasty. Of these, 47 were eligible for analysis. Six patients (12.8 %) developed SSI following the replacement of autologous cryopreserved bone, whereas bone resorption occurred in two patients (4.3 %). No factors predicted a statistically significant rate of SSI, however, prolonged procedural time and cardiovascular comorbidity tended to increase the risk of SSI. CONCLUSIONS: SSI and bone flap resorption are the most frequent complications associated with the reimplantation of autologous cryopreserved bone after decompressive craniectomy. Prolonged procedural time and cardiovascular comorbidity tend to increase the risk of SSI.

Isoflurane-induced depolarization of neural mitochondria increases with age.

BACKGROUND AND OBJECTIVES: The mitochondrial membrane potential (DeltaPsi(m)) drives the three fundamental functions of mitochondria, namely adenosine triphosphate (ATP) generation, Ca(2+) uptake/storage, and generation/detoxification of ROS. Isoflurane depolarizes neural mitochondria. The sensitivity for general anesthetics increases with age, but the mechanism for this age-related sensitivity is still unknown. We compared the effect of isoflurane on [Ca(2+)](i) and DeltaPsi(m) in isolated pre-synaptic terminals (synaptosomes) from neonatal, adolescent, and adult rats and the influence of interventions in the respiratory chain was assessed. METHODS: Synaptosomes were loaded with the fluorescent probes fura-2 ([Ca(2+)](i)) and JC-1 (DeltaPsi(m)) and exposed to isoflurane 1 and 2 minimum alveolar concentration (MAC). The effect on the electron transport chain was investigated by blocking complexes I and V. RESULTS: In neonatal rats isoflurane had no significant effect on DeltaPsi(m). In adolescent and adult synaptosomes, however, isoflurane 1 and 2 MAC decreased DeltaPsi(m). Isoflurane 2 MAC increased [Ca(2+)](i) in neonatal and adolescent rats, but not in adult synaptosomes. In Ca(2+)-depleted medium, isoflurane still decreased DeltaPsi(m), while [Ca(2+)](i) remained unaltered. By blocking complex V of the respiratory chain, the isoflurane-induced mitochondrial depolarization was enhanced in all age groups. Blocking complex I depolarized the mitochondria to the same extent as isoflurane 2 MAC, but without any additive effect. CONCLUSIONS: The depolarizing effect of isoflurane on neural mitochondria is more pronounced in the adolescent and adult than in neonatal synaptosomes. The increased mitochondrial sensitivity with age seems to be related to the reversed function of the ATP synthase of the electron transport chain.

Sevoflurane and propofol depolarize mitochondria in rat and human cerebrocortical synaptosomes by different mechanisms.

BACKGROUND AND OBJECTIVES: The mitochondrial membrane potential drives the main functions of the mitochondria. Sevoflurane depolarizes neural mitochondria. There is still, however, limited information concerning the effect of anaesthetics on neural mitochondria in humans. The effect of sevoflurane and propofol on the intracellular Ca(2+) concentration [Ca(2+)](i) and the mitochondrial membrane potential (DeltaPsi(m)) was therefore compared in rat and human synaptosomes, and the changes were related to interventions in the electron transport chain. METHODS: Synaptosomes from rat and human cerebral cortex were loaded with the fluorescent probes fura-2 ([Ca(2+)](i)) and JC-1 (DeltaPsi(m)) before exposure to sevoflurane 1 and 2 minimum alveolar concentration (MAC), and propofol 30 and 100 microM. The effect on the electron transport chain was investigated by blocking complex V. RESULTS: Sevoflurane and propofol decreased DeltaPsi(m) in rat synaptosomes in a dose-dependent manner, and to the same extent by equipotent doses. Inhibition of complex V enhanced the depolarizing effect of sevoflurane 2 MAC, but not of propofol 100 microM. Neither sevoflurane nor propofol affected [Ca(2+)](i) significantly. Sevoflurane and propofol decreased DeltaPsi(m) in human synaptosomes to the same extent as in the rat experiments. CONCLUSIONS: Sevoflurane and propofol at equipotent doses depolarize the mitochondria in rat and human nerve terminals to the same extent. The depolarizing effect of propofol on Psi(m) was more rapid in onset than that of sevoflurane. Whereas sevoflurane inhibits the respiratory chain sufficiently to cause ATP synthase reversal, the depolarizing effect of propofol seems to be related to inhibition of the respiratory chain from complex I to V.

Survival, prognostic factors, and therapeutic efficacy in low-grade glioma: a retrospective study in 379 patients.

PURPOSE: We report survival, prognostic factors, and treatment efficacy in low-grade glioma. PATIENTS AND METHODS: A total of 379 patients with histologic intracranial low-grade glioma received post-operative radiotherapy (n = 361) and intraarterial carmustine (BCNU) chemotherapy (n = 153). Overall survival and prognostic factors were evaluated with the SPSS statistical program (SPSS Inc, Chicago, IL). RESULTS: Median survival (all patients) was 100 months (95% confidence interval [CI], B7 to 113); in age group 0 to 19 years (n = 41), 226 months; in age group 20 to 49 years (n = 263), 106 months; in age group 50 to 59 years (n = 49), 76 months; and for older patients (n = 26), 39 months. Projected survival at 10 and 15 years was 42% and 29%, respectively. Patient age, World Health Organization (WHO) performance status, tumor computed tomography (CT) contrast enhancement, mental changes, or initial corticosteroid dependency were significant independent prognostic factors (p < .05), while histologic subgroup, focal deficits, presence of seizures, prediagnostic symptom duration, tumor category, and tumor stage were not. Patients aged 20 to 49 years with no independent negative prognostic factors (n = 132) had a median survival time of 139 months versus 41 months in patients with two or more factors (n = 33). Patients who presented with symptoms of expansion (n = 97) survived longer when resected (P < .03); otherwise no survival benefit was associated with initial tumor resection compared with biopsy. Intraarterial chemotherapy and radiation doses more than 55 Gy were not associated with prolonged survival. Among 66 reoperated patients, 45% progressed to high-grade histology within 25 months. CONCLUSION: Prognosis in low-grade glioma following postoperative radiotherapy seems largely determined by the inherent biology of the glioma and patient age at diagnosis.

Redistribution of glutamate and glutamine in slices of human neocortex exposed to combined hypoxia and glucose deprivation in vitro.

This study was undertaken to elucidate the roles of neurons and glial cells in the handling of glutamate and glutamine, a glutamate precursor, during cerebral ischemia. Slices (400-600 microns) from human neocortex obtained during surgery for epilepsy or brain tumors were incubated in artificial cerebrospinal fluid and subjected to 30 min of combined hypoxia and glucose deprivation (an in vitro model of brain ischemia). These slices, and control slices that had not been subjected to "ischemic" conditions, were then fixed and embedded. Ultrathin sections were processed according to a postembedding immunocytochemical method with polyclonal antibodies raised against glutamate or glutamine, followed by colloidal gold-labeled secondary antibodies. The gold particle densities over various tissue profiles were calculated from electron micrographs using a specially designed computer program. Combined hypoxia and glucose deprivation caused a reduced glutamate immunolabeling in neuronal somata, while that of glial processes increased. Following 1 h of recovery, the glutamate labeling of neuronal somata declined further to very low values, compared to control slices. The glutamate labeling of glial cells returned to normal levels following recovery. In axon terminals, no consistent change in the level of glutamate immunolabeling was observed. Immunolabeling of glutamine was low in both nerve terminals and neuronal somata in normal slices and was reduced to nondetectable levels in nerve terminals upon hypoxia and glucose deprivation. This treatment was also associated with a reduced glutamine immunolabeling in glial cells. Reversed glutamate uptake due to perturbations of the transmembrane ion concentrations and membrane potential probably contributes to the loss of neuronal glutamate under "ischemic" conditions. The increased glutamate labeling of glial cells under the same conditions can best be explained by assuming that glial cells resist a reversal of glutamate uptake, and that their ability to convert glutamate into glutamine is compromised due to the energy failure. The persistence of a nerve terminal pool of glutamate is compatible with recent biochemical data indicating that the exocytotic glutamate release is contingent on an adequate energy supply and therefore impeded during ischemia.

Temperature sensitivity of thin unmyelinated fibers in rat hippocampal cortex.

The effect of changes in temperature on the activity of thin intracortical unmyelinated fibers was investigated in rat hippocampal slices. The amplitude of the presynaptic volley was increased by 40% when the temperature was raised from 23 degrees C to 30 degrees C, whereas the area of the presynaptic volley was reduced. Increasing the temperature above 30 degrees C was without further effect on the amplitude. The conduction velocity was 0.3 m.s-1 at 35 degrees C and 0.1 m.s-1 at 12 degrees C. The Q10 of velocity (25 degrees C-35 degrees C) was 1.6.

Mechanisms concerned in the direct effect of isoflurane on rat hippocampal and human neocortical neurons.

The effect of isoflurane on postsynaptic neurons was studied by intracellular recordings from rat hippocampus and human neocortex in vitro. Isoflurane caused a hyperpolarization of the cell membrane. The hyperpolarization was reversed (although incompletely in some neurons) by increasing the membrane potential. The reversal potential was -80 +/- 12 mV (mean +/- S.D.) or 12 +/- 6 mV negative to the resting membrane potential. Potassium channel blockers reduced the isoflurane-induced hyperpolarization, while chloride loading was without effect. The transient depolarization preceding the hyperpolarization in some of the neurons was not reversed by hyperpolarization. The action potential was prolonged by 19 +/- 3% due to a slower rate of rise. The rise time was almost doubled. Firing threshold was increased by 4 +/- 3 mV (relative to the reference electrode). Subthreshold inward rectification was reduced or abolished. Some cells showed subthreshold outward rectification during isoflurane administration. These results suggest that isoflurane depressed neuronal excitability by (1) hyperpolarizing the cell membrane, at least partly by an increase in potassium conductance, (2) slowing the rate of rise of the action potential, presumably due to interference with the fast sodium channel, (3) decreasing subthreshold inward rectification and (4) increasing firing threshold.

Measured increase in intracellular Ca(2+) during stimulated release of endogenous glutamate from human cerebrocortical synaptosomes.

Presynaptic terminals (synaptosomes) prepared from guinea pig and rat cerebral cortex release endogenous glutamate in a Ca(2+)-dependent manner in response to membrane depolarisation. In the present study, synaptosomes were prepared from human cerebral cortex removed in association with temporal lobe resections in epileptic patients. The cytosolic free Ca(2+) concentration increased from 474+/-66 before to 649+/-89 nM after 2 min depolarisation. The basal level of free cytosolic Ca(2+) is higher and the increase in response to depolarisation is more pronounced in human synaptosomes than observed in animal experiments. The Ca(2+)-dependent glutamate release, estimated as the difference between total - and the Ca(2+)-independent glutamate release, increased from 0 to 5.4+/-1.9 nmol/mg protein. The released amount of glutamate is larger than reported in animal models. These results demonstrate that membrane depolarisation of synaptosomes from human brain evokes a rapid rise in cytosolic free Ca(2+) and a more prolonged rise in synaptic, Ca(2+)-dependent glutamate release.

An experimental study of the effect of isoflurane on epileptiform bursts.

The effect of isoflurane on penicillin- and picrotoxin-induced epileptiform activity was tested using hippocampal slice preparations. Isoflurane reduced both the frequency of spontaneous epileptiform bursts and the number of population spikes within each burst in a dose-dependent manner. The last population spikes in the burst were most sensitive to the anesthetic, whereas the first 4-6 spikes were quite resistant and persisted until spontaneous activity was abolished at 3% isoflurane. Isoflurane increased the stimulus current required to evoke epileptiform bursts and shifted the relationship between stimulus current and population spike amplitude to the right. At 3% isoflurane, a dose that usually causes iso-electric EEG and abolishes all spontaneous epileptiform activity, responses could still be evoked, and then invariably had an epileptiform pattern. The maximum response was reduced compared to control and 1.5% isoflurane. With isoflurane there was a reduced tendency for activity to be transmitted from one region within the hippocampus to the other. This effect was also dose-dependent. However, transmitted activity always retained a typical epileptiform character, although the number of population spikes within a train to some extent decreased with increasing concentrations of isoflurane.

Chloride influx during cerebral energy deprivation.

The purpose of the present study was to investigate the possible role of chloride influx and GABA release during cerebral energy deprivation (ED). The functional activity measured by evoked activity (population spike) in hippocampal slices was recorded during nine minutes of ED and 60 minutes recovery. Treatment groups were exposed to ED following administration of the GABAA antagonist penicillin G (pc G) or substitution of extracellular chloride. The release of glutamate and GABA was measured by HPLC. The efflux of 36Cl from preloaded slices was measured during ED with and without blocking the GABAA receptor. The population spike disappeared during ED, and there was a marked release of GABA and glutamate. During recovery the population spike recovered partially. Both application of pc G and substitution of extracellular chloride during ED improved population spike recovery. Uptake of radiolabeled chloride was significantly reduced by pc G. Glutamate release, but not GABA, was significantly reduced by chloride substitution. These results indicate a possible role of chloride mediated injury during ED, and suggest that chloride entry may partly occur through ligand-operated channels. Furthermore there may be an early chloride dependent release of glutamate during cerebral ischemia, whereas later release seems to be chloride independent.

Changes in amino acid release and membrane potential during cerebral hypoxia and glucose deprivation.

Excessive release of glutamate is believed to play a major role in the susceptibility of neurons to ischaemia. Whether the glutamate release is the primary event or occurs in response to electrophysiologic alterations has not been clarified. In the present study, the amino acid release was therefore correlated to changes in electrophysiological parameters and energy status during conditions of low oxygen tension and varying glucose concentrations in rat hippocampal slices. Plain hypoxia failed to produce glutamate release. All neurons underwent, however, a slow depolarization causing most of the neurons to lose their membrane potential within 10 minutes. By restoring the membrane potential to resting level by current injection, the neurons could still be activated synaptically and respond to transmitter application. Following reoxygenation most of the cells regained their resting membrane potential, but showed reduced excitability. When the slices were exposed to hypoxia combined with glucose deprivation (simulated ischaemia), there was a pronounced increase in the glutamate release. This glutamate release was always preceded by a fast anoxic depolarization. Whereas hypoxia reduced the ATP content only to approximately 50%, ATP was depleted in slices exposed to simulated ischaemia. The results demonstrate that although the neurons lose their membrane potential completely during hypoxia, there is no glutamate release. A fast anoxic depolarization provoked by simulated ischaemia, however, is always followed by glutamate release, probably due to a more severe ATP depletion.

Changes in inhibitory synaptic transmission induced by isoflurane studied in rat hippocampal slices.

The effect of isoflurane on inhibitory postsynaptic potentials (IPSPs) was studied in rat hippocampal slices by intracellular recordings from pyramidal neurons (n = 34). The amplitude of the IPSP was transiently increased and subsequently reduced in a dose-dependent manner. The duration of the IPSP was increased. The reduction in the IPSP persisted after correction was made for the anesthetic-induced hyperpolarization. The reversal potential for the IPSP was slightly displaced in the depolarizing direction. The depolarizing gamma-aminobutyric acid (GABA) response was unaltered, while the hyperpolarizing GABA response was reduced, suggesting a postsynaptic action. The reduction in the IPSP produced by isoflurane is at least partly due to an altered reversal potential for the IPSP (EIPSP).

The effect of isoflurane on brain amino acid release and tissue content induced by energy deprivation.

This article describes the effect of isoflurane on amino acid release and tissue content induced by energy deprivation in slices of rat hippocampus. Energy deprivation (95% N2 / 5% CO2 and glucose free medium) (ED) induced an increase in the release of all amino acids measured, with the exception of glutamine. The tissue content of all amino acids except gamma-aminobutyric acid (GABA) and arginine was concomitantly reduced. Isoflurane (1.5% and 3.0%) reduced glutamate release during ED by 27% and 28% (p < 0.05 as compared with release without isoflurane), respectively, whereas the tissue content was slightly increased. Similarly, GABA release was reduced by 25% and 25% (p < 0.05 as compared with release without isoflurane) accompanied by an insignificant enhancement in tissue content as compared with ED without isoflurane. Isoflurane reduced the release of taurine and most of the other amino acids. The total amount of all amino acids (both released and retained) was not significantly altered by the anesthetic. These observations demonstrate that isoflurane can modify the changes in amino acid handling induced by energy deprivation.

Volatile anaesthetics depolarize neural mitochondria by inhibiton of the electron transport chain.

BACKGROUND: The mitochondrial membrane potential (DeltaPsim) controls the generation of adenosine triphosphate (ATP) and reactive oxygen species, and sequesteration of intracellular Ca2+[Ca2+]i. Clinical concentrations of sevoflurane affect the DeltaPsim in neural mitochondria, but the mechanisms remain elusive. The aim of the present study was to compare the effect of isoflurane and sevoflurane on DeltaPsim in rat pre-synaptic terminals (synaptosomes), and to investigate whether these agents affect DeltaPsim by inhibiting the respiratory chain. METHODS: Synaptosomes were loaded with the fluorescent probes JC-1 (DeltaPsim) and Fura-2 ([Ca2+]i) and exposed to isoflurane or sevoflurane. The effect of the anaesthetics on the electron transport chain was investigated by blocking complex I and complex V. RESULTS: Isoflurane 1 and 2 minimum alveolar concentration (MAC) decreased the normalized JC-1 ratio from 0.92 +/- 0.03 in control to 0.86 +/- 0.02 and 0.81 +/- 0.01, respectively, reflecting a depolarization of the mitochondrial membrane (n = 9). Isoflurane 2 MAC increased [Ca2+]i. In Ca2+-depleted medium, isoflurane still decreased DeltaPsim while [Ca2+]i remained unaltered. The effect of isoflurane was more pronounced than for sevoflurane. Blocking complex V of the respiratory chain enhanced the isoflurane- and sevoflurane-induced mitochondrial depolarization, whereas blocking complex I and V decreased DeltaPsim to the same extent in control, isoflurane and sevoflurane experiments. CONCLUSIONS: Isoflurane and sevoflurane may act as metabolic inhibitors by depolarizing pre-synaptic mitochondria through inhibition of the electron transport chain, although isoflurane seems to inhibit mitochondrial function more significantly than sevoflurane. Both agents inhibit the respiratory chain sufficiently to cause ATP synthase reversal.

[Action mechanisms of intravenous anesthetics]. / Virkningsmekanismer for intravenøse anestesimidler.

Intravenous anaesthetic agents depress the activity of the brain by acting on receptor-operated ion channels. Barbiturates enhance gamma-aminobutyric acid (GABA)-mediated inhibition, depress glutamate-mediated excitation, and hyperpolarize the membrane by increased potassium conductance. Benzodiazepines facilitate GABA-mediated inhibition by binding to a benzodiazepine recognition site on the GABA receptor complex, and affect potassium channels. Opioids bind to opioid receptors and hyperpolarize the membrane by enhanced potassium and calcium conductances. Ketamine depresses excitatory synaptic transmission by acting on glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype. Propofol acts at a recognition site on the GABA receptor, which differs from the binding sites of both barbiturates and benzodiazepines.

Isoflurane hyperpolarizes neurones in rat and human cerebral cortex.

The effect of the anaesthetic gas isoflurane was studied by intracellular recordings in neurones from rat hippocampal cortex and neurones from human neocortex in vitro. Anaesthetic concentrations of isoflurane abolished spontaneous activity and reduced synaptically evoked activity without rendering individual cells inexcitable or preventing evoked synaptic activity to increased afferent input. Induced epileptiform activity was not observed. Isoflurane reversibly hyperpolarized the cell membrane in a dose-dependent manner, isoflurane 1.5, 3 and 5% causing 4 +/- 1, 6 +/- 2 and 8 +/- 2 mV (mean +/- SD) hyperpolarization, respectively. The hyperpolarization was accompanied by a reduction in the input resistance, 18 +/- 3% for 3% isoflurane. The effects remained unchanged after synaptic transmission was blocked. Five experiments with intracellular recordings from human cortical neurones in vitro showed identical results.

The effect of isoflurane on unmyelinated and myelinated fibres in the rat brain.

The effect of isoflurane on unmyelinated and myelinated fibres of the rat brain was investigated in vitro. The amplitude of the unmyelinated fibre potential (the prevolley of the hippocampal CA1 region) was reduced in a dose-dependent manner with increasing isoflurane concentrations (up to 5%). The conduction velocity was slightly decreased. The minimal alveolar concentration (MAC) anesthetizing 50% of the animals is 1.38%. At this concentration the presynaptic volley was reduced by 18% and the conduction velocity was decreased by about 1%. The effect on myelinated fibres (fimbria) was small and significantly different from the effect on unmyelinated fibres (P = 0.03 and 0.005 at 1 and 2% isoflurane, respectively.

Isoflurane effects in rat hippocampal cortex: a quantitative evaluation of different cellular sites of action.

In order to evaluate quantitatively the effects of an inhalation anaesthetic on neuronal excitability and on synaptic transmission in the central nervous system, we have examined the action of isoflurane on slices from rat hippocampal cortex. Isoflurane 1.5% (1.38% anaesthetize 50% of tested rats (MAC)) reduced orthodromically evoked activity in pyramidal cells by 62%. This was due to the combined effects on afferent fibres, excitatory synapses and pyramidal cells. The effect on the postsynaptic neurones was almost as strong as the effect on the excitatory synapses: the population spike evoked by a given synaptic current was reduced by 24%, and the field-EPSP in response to a given afferent fibre volley by 27%. The presynaptic fibre volley was reduced by 17%.

The effect of isoflurane on excitatory synaptic transmission in the rat hippocampus.

The purpose of this investigation was to study the effect of isoflurane on excitatory synaptic transmission. Rat hippocampal slices maintained in vitro were used as a model. Isoflurane caused a dose-dependent reduction of the excitatory postsynaptic potential (EPSP); 1.5% isoflurane reduced the EPSP by 35 +/- 9% (mean +/- s.d.) and 3% by 57 +/- 11%. Neither spontaneous nor potassium-stimulated efflux of the glutamate analogue D-(3H)aspartate was changed, but the content of D-(3H)aspartate in slices loaded during isoflurane was reduced to 83 +/- 12% of control (P less than 0.05). The intracellularly recorded response to direct application of glutamate increased by 37 +/- 20% during isoflurane (3%) and 50 +/- 5% during halothane (2%). Isoflurane (3%) enhanced the response to the glutamate receptor agonist quisqualate by 44 +/- 19%, whereas the N-methyl-D-aspartate response was unchanged. Isoflurane enhanced the tetanic depression of the population spike. The present results suggest that isoflurane reduces excitatory synaptic transmission by a presynaptic mechanism.