A 37-year-old man with nonischemic 4-chamber dilated cardiomyopathy and low-output cardiac failur... more A 37-year-old man with nonischemic 4-chamber dilated cardiomyopathy and low-output cardiac failure (estimated ejection fraction of 10%) underwent awake craniotomy for a low-grade oligodendroglioma resection under monitored anesthesia care. The cerebrovascular and cardiovascular physiologic challenges and our management of this patient are discussed.
Propofol has not been studied directly in animals subject to cerebral ischemia in the conscious s... more Propofol has not been studied directly in animals subject to cerebral ischemia in the conscious state. Strokes are usually induced in animals while they are anesthetized, making it difficult to eliminate anesthetic interactions as a complicating factor. Therefore, to compare the neuroprotective effects of propofol to the unanesthetized state, experiments were performed using a model that induces a stroke in the conscious rat. Cerebral ischemia was induced in awake Wistar rats by a local intracerebral injection of the potent vasoconstrictor endothelin. Four days before the strokes were induced, a guide cannula was implanted for the injection of endothelin. On the day of the experiment, endothelin (6.0 pmol in 3 microl) was injected into the striatum. Propofol (25 or 15 mg. kg-1. h-1) or intralipid (vehicle) were infused for 4 h starting immediately after the endothelin injection. In another series, the propofol infusion was begun 1 h after the endothelin injection and continued for 4...
OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm s... more OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm surgery. METHODS: One hundred fourteen patients undergoing cerebral aneurysm clipping with (n = 52) (World Federation of Neurological Surgeons score <=III) and without (n = 62) acute aneurysmal subarachnoid hemorrhage (SAH) were randomized to normothermic (target esophageal temperature at clip application of 36.5°C) and hypothermic (target temperature of 33.5°C) groups. Neurological status was prospectively evaluated before surgery, 24 and 72 hours
Cardiac injury and dysfunction are common after aneurysmal subarachnoid hemorrhage (SAH) and are ... more Cardiac injury and dysfunction are common after aneurysmal subarachnoid hemorrhage (SAH) and are most likely caused by excessive catecholamine release within the myocardium (1 -3) . Whether the occurrence of cardiac dysfunction negatively impacts neurological outcomes, however, remains controversial. The primary aim of this study was to quantify the effects of specific cardio-
Oxygen-centered free radicals cause brain injury associated with trauma and stroke. These reactiv... more Oxygen-centered free radicals cause brain injury associated with trauma and stroke. These reactive oxygen species may be detoxified by endogenous antioxidants, but cell death occurs after antioxidants become depleted. General anesthetics penetrate into brain parenchyma, where they may abrogate oxidative injury to neurons by several mechanisms that prevent the initiation of free radical chain reactions or terminate the propagation of highly reactive radicals. First, general anesthetics may inhibit free radical generation because these drugs slow cerebral utilization of oxygen and glucose, inhibit oxidative metabolism in neutrophils, and prevent redox changes in hemoglobin. Second, antioxidant anesthetics, such as thiopental and propofol, directly scavenge reactive oxygen species and inhibit lipid peroxidation. Finally, anesthetics may prevent the elevation of extracellular glutamate concentration and inhibit the activation of excitatory glutamatergic receptors that augment oxidative stress after ischemia.
The use of remifentanil for sedation during awake epilepsy surgery has been described in a case r... more The use of remifentanil for sedation during awake epilepsy surgery has been described in a case report. However, little information is available regarding the effect of remifentanil on the quality of intraoperative electrocorticography (ECoG). This study was designed to investigate the effect of sedative doses of remifentanil on ECoG interictal spike activity among patients undergoing awake anterior temporal lobectomy for refractory epilepsy. Ten adult patients were studied prospectively. After baseline EcoG recordings were obtained, remifentanil was administered as a continuous infusion at 0.1 microg/kg/min and the ECoG recorded continuously for 15 minutes. Recordings obtained before and during the administration of remifentanil were compared with respect to spike frequency and location. A trend toward a small decrease in spike frequency was observed as patients became increasingly somnolescent and background ECoG activity slowed. The difference was not statistically significant. Blood pressure and heart rate were not adversely affected by the administration of remifentanil. Respiratory rates decreased in all patients (mean decrease, 8 breaths/min) and one patient transiently developed a respiratory rate of 4 breaths per minute that elicited a decrease in the rate of remifentanil administration. Remifentanil administered at sedation doses does not adversely affect intraoperatively recorded interictal spike activity. Further investigation of the use of this drug during awake epilepsy surgery is warranted.
Inhibition of the NMDA receptor likely contributes to ketamine&#39;s neurodepressive properti... more Inhibition of the NMDA receptor likely contributes to ketamine&#39;s neurodepressive properties. Magnesium also inhibits the NMDA receptor by binding to a site associated with the ketamine-binding domain. Electrophysiological studies suggest that magnesium prevents ketamine from binding to the NMDA receptor and thereby prevents ketamine inhibition. We undertook an in vivo study to determine if magnesium deficiency was associated with an increased sensitivity to ketamine. Weanling rats were maintained on a Mg(2+)-deficient or control diet for 14 days. In Study I, rats were anaesthetized then sacrificed and the Mg2+ concentrations in the brain and plasma were measured. In a second prospective study, experimental animals were rendered hypomagnesaemic and the potency of 125 mg.kg-1 ip ketamine was evaluated. Animals were then were fed a Mg(2+)-containing diet and ketamine sensitivity was re-examined 14 days later. The Mg(2+)-deficient diets rendered the rats hypomagnesaemic as indicated by the brain and plasma concentration of Mg2+. In Study 2, the time to loss of righting reflex was shorter; 1.9 +/- 0.3 min (n = 12) and 2.6 +/- 0.2 min (n = 16, P &lt; 0.05), whereas the latency to toe pinch was prolonged: 25.0 +/- 5.8 min (n = 12) vs 3.1 +/- 2.1 min (n = 16, P &lt; 0.05) in the Mg(2+)-deficient compared with age-matched control animals, respectively. The hypomagnesaemic animals had a higher death rate following ketamine injection. The increased sensitivity to ketamine was no longer apparent when the animals were re-tested following replenishment of Mg2+. Hypomagnesaemia is associated with an increased sensitivity to ketamine.
Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 2003
P Pu ur rp po os se e: : To compare the recovery profiles, efficacy and safety of remifentanil an... more P Pu ur rp po os se e: : To compare the recovery profiles, efficacy and safety of remifentanil and morphine for transitional analgesia with fentanyl in patients undergoing elective craniotomy for supratentorial mass lesions.
Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) a... more Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) among the elderly. This study evaluated the safety and efficacy of propofol PCS among elderly patients undervooing hip or knee a~throplasty. Methods= Forty patients, aged 65-78 yr, undergoing hip or knee arthroplasty under regional anaesthesia were randomized to receive propofol PCS (dose = 0,3 mg,kg ~, delay=three min: n = 20)or anaesthetist-administered midazolam-fentanyl sedation (n=20), Sedation, anxiety and discomfort visual analogue scores (VAS) were measured, by an independent observer, preoperatively, immediately at the end of surgery and one hour following admission to the postanaesthetic care unit (PACU). Cognition was evaluated, using an abbreviated M~ni Mental Status Examination, preoperatively and in the PACU, Patient satisfaction, based on VAS and a brief questionnaire, was measured in the PACU. The incidence of intraoperative complications was also compared. Results: Patient satisfaction was high in each group. Sedation and anxiety VAS were similar in each group, A high incidence of pain with drug injection was noted among patients receiving propofot (80%). -ri-ansient deeper levels of sedation (6 vs I; P=O.05) were observed more commonly in the propofol PCS group. Conclusion: Propofol PCS provides effective sedation, Using a propofol dose of 0.3 mg.kg , transient episodes of deeper sedation were noted more frequently among patients receiving PCS. These episodes did not require intervention but, suggest that this propofol PCS dose approaches the limit of safety and should be fuT~ther reduced for some elderly patients.
Neurolept anaesthesia is used during awake craniotomy for epilepsy surgery. This study compares a... more Neurolept anaesthesia is used during awake craniotomy for epilepsy surgery. This study compares analgesia, sedation and the side effects of the newer opioids sufentanil and alfentanil, with those of fentanyl in patients undergoing awake craniotomy. Thirty patients were randomized into three groups, each received droperidol, dimenhydrinate and the chosen opioid as a bolus followed by an infusion. The opioid doses used were fentanyl 0.75 #g" kg -1 plus 0.01 I~g" kg-l" min-t; sufentanil 0.075 l~g" kg -1 plus 0.0015 gg" kg -~" min -t, and alfentanil 7.5 vg" kg -1 plus 0.5 #g" kg -I" min -1. There were no differences in the requirements for droperidol, dimenhydrinate or in the incidence of complications among 'the three groups. The total doses of the opioids required were fentanyl 4.9 5:L3 vg" kg -1, sufentanil 0.6 + 0.2 ~g" kg -1 and alfentani1149 5:36 I~g" kg-!. Two patients became uncooperative requiring general anaesthesia. The conditions for surgery, electrocorticography and for stimulation testing were satisfactory in all other patients. We conclude that the newer opioids did not offer any benefit over fentanyl. Le traitement chirurgical de l~pilepsie par craniotomie se fait souvent dt l~tat vigile sous neuroleptanalgdsie. Cette dtude vise d comparer l'analgdsie, la sddation et les effets secondaires des nouveaux morphiniques sulfentanil et alfentanil avec le fentanyt chez des malades en cours de cranitomie vigile. Trente patients sont distribuds au hasard en trois groupes, chacun recevant drop$ridol, dimenhydrhlate et un des morphiniques en bolus suivi d'un perfusion. La posologie est pour le fentanyl de 0,75
Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 1999
To examine the learning ability of rats shortly after recovery from a bolus dose of propofol by a... more To examine the learning ability of rats shortly after recovery from a bolus dose of propofol by assessing learning on a swim-to-platform task. Also, muscarinic blockade was used as a pharmacological test of whether learning shortly after propofol anesthesia resembles normal learning. Propofol anesthetized rats (15-20 mg x kg(-1) i.v.) were trained on a swim-to-platform task five to seven minutes after recovering from surgical anesthesia and tested two to three hours later In addition, the muscarinic antagonist scopolamine hydrobromide (5 mg x kg(-1) s.c.) was given to a subgroup of rats before testing. During 10 trials, the number of times a given rat took 10 sec or longer to locate and climb onto a visible platform was tabulated and counted as errors. When trained shortly after recovery from the anesthetic, propofol anesthetized rats made 3.2 +/- 0.4 compared with 1.0 +/- 0.1 errors in controls (P &lt; 0.0001). Two to three hours later both groups performed equally well. Rats trained after propofol anesthesia and given scopolamine before testing made 0.7 +/- 0.5 errors and performed as well as normal controls, 1.2 +/- 0.2 errors when subjected to the same procedures without propofol anesthesia, and better than scopolamine-treated untrained rats, 5.5 +/- 0.7 errors, (P &lt; 0.05). Training five to seven minutes after recovery from propofol anesthesia resulted in normal retention of the swim- to-platform task. It also produced the same resistance to the disruptive effects of scopolamine as did training in rats that were not anesthetized. Thus, the ability to learn recovers rapidly after propofol anesthesia induced by a single intravenous bolus dose.
Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) a... more Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) among elderly patients undergoing operative procedures under local or regional anaesthesia. This prospective, randomized study evaluated the safety of propofol PCS, and the attitude among elderly patients toward self-administration of sedation during cataract surgery. Methods: Prospective, randomized study conducted in a University affiliated, tertiary-care hospital. Fifty-five elderly patients (aged 65-79 yr) were randomized to receive propofol patient-controlled sedation (PCS) (n = 28) or no intraoperarive sedation (n = 27) during cataract surgery performed under peribulbar block. The PCS parameters consisted of a lockout interval of three minutes and a PCS dose of 0.3 mg. kg -/. Study groups were compared with respect to sedation, anxiety and discomfort visual analogue scores (VAS), cognitive functioning, patient satisfaction and the incidence of intraoperative complications. Results: Patients in the PCS group administered a mean propofol dose of 65 • 49 mg during procedures with a mean duration of 46 rain. The incidence of intraoperative complica-
The concentrations of glutamate and ascorbate in brain extracellular fluid increase following sei... more The concentrations of glutamate and ascorbate in brain extracellular fluid increase following seizure activity, trauma and ischemia. Extracellular ascorbate concentration also rises following intracerebral glutamate injection. We hypothesized that glutamate triggers the release of ascorbate from astrocytes. We observed in primary cultures of rat cerebral astrocytes that glutamate increased ascorbate efflux significantly within 30 min. The half-maximal effective concentration of glutamate was 180 " 30 mM. Glutamate-stimulated efflux of ascorbate was attenuated by hypertonic media. 4,4 X -diisothiocyanatostilbene-2,2 X -disulfonic acid inhibited both Na q -dependent glutamate Ž Ž uptake and ascorbate efflux. Two other inhibitors of volume-sensitive organic anion channels 1,9-dideoxyforskolin and 5-nitro-2-3-. . phenylpropylamino benzoic acid did not slow glutamate uptake but prevented stimulation of ascorbate efflux. Glutamate also stimulated the uptake of ascorbate by ascorbate-depleted astrocytes. In contrast, glutamate uptake was not affected by intracellular ascorbate, thus ruling out a putative glutamate-ascorbate heteroexchange mechanism. These results are consistent with activation by glutamate of ascorbate-permeant channels in astrocytes. q
A 37-year-old man with nonischemic 4-chamber dilated cardiomyopathy and low-output cardiac failur... more A 37-year-old man with nonischemic 4-chamber dilated cardiomyopathy and low-output cardiac failure (estimated ejection fraction of 10%) underwent awake craniotomy for a low-grade oligodendroglioma resection under monitored anesthesia care. The cerebrovascular and cardiovascular physiologic challenges and our management of this patient are discussed.
Propofol has not been studied directly in animals subject to cerebral ischemia in the conscious s... more Propofol has not been studied directly in animals subject to cerebral ischemia in the conscious state. Strokes are usually induced in animals while they are anesthetized, making it difficult to eliminate anesthetic interactions as a complicating factor. Therefore, to compare the neuroprotective effects of propofol to the unanesthetized state, experiments were performed using a model that induces a stroke in the conscious rat. Cerebral ischemia was induced in awake Wistar rats by a local intracerebral injection of the potent vasoconstrictor endothelin. Four days before the strokes were induced, a guide cannula was implanted for the injection of endothelin. On the day of the experiment, endothelin (6.0 pmol in 3 microl) was injected into the striatum. Propofol (25 or 15 mg. kg-1. h-1) or intralipid (vehicle) were infused for 4 h starting immediately after the endothelin injection. In another series, the propofol infusion was begun 1 h after the endothelin injection and continued for 4...
OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm s... more OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm surgery. METHODS: One hundred fourteen patients undergoing cerebral aneurysm clipping with (n = 52) (World Federation of Neurological Surgeons score <=III) and without (n = 62) acute aneurysmal subarachnoid hemorrhage (SAH) were randomized to normothermic (target esophageal temperature at clip application of 36.5°C) and hypothermic (target temperature of 33.5°C) groups. Neurological status was prospectively evaluated before surgery, 24 and 72 hours
Cardiac injury and dysfunction are common after aneurysmal subarachnoid hemorrhage (SAH) and are ... more Cardiac injury and dysfunction are common after aneurysmal subarachnoid hemorrhage (SAH) and are most likely caused by excessive catecholamine release within the myocardium (1 -3) . Whether the occurrence of cardiac dysfunction negatively impacts neurological outcomes, however, remains controversial. The primary aim of this study was to quantify the effects of specific cardio-
Oxygen-centered free radicals cause brain injury associated with trauma and stroke. These reactiv... more Oxygen-centered free radicals cause brain injury associated with trauma and stroke. These reactive oxygen species may be detoxified by endogenous antioxidants, but cell death occurs after antioxidants become depleted. General anesthetics penetrate into brain parenchyma, where they may abrogate oxidative injury to neurons by several mechanisms that prevent the initiation of free radical chain reactions or terminate the propagation of highly reactive radicals. First, general anesthetics may inhibit free radical generation because these drugs slow cerebral utilization of oxygen and glucose, inhibit oxidative metabolism in neutrophils, and prevent redox changes in hemoglobin. Second, antioxidant anesthetics, such as thiopental and propofol, directly scavenge reactive oxygen species and inhibit lipid peroxidation. Finally, anesthetics may prevent the elevation of extracellular glutamate concentration and inhibit the activation of excitatory glutamatergic receptors that augment oxidative stress after ischemia.
The use of remifentanil for sedation during awake epilepsy surgery has been described in a case r... more The use of remifentanil for sedation during awake epilepsy surgery has been described in a case report. However, little information is available regarding the effect of remifentanil on the quality of intraoperative electrocorticography (ECoG). This study was designed to investigate the effect of sedative doses of remifentanil on ECoG interictal spike activity among patients undergoing awake anterior temporal lobectomy for refractory epilepsy. Ten adult patients were studied prospectively. After baseline EcoG recordings were obtained, remifentanil was administered as a continuous infusion at 0.1 microg/kg/min and the ECoG recorded continuously for 15 minutes. Recordings obtained before and during the administration of remifentanil were compared with respect to spike frequency and location. A trend toward a small decrease in spike frequency was observed as patients became increasingly somnolescent and background ECoG activity slowed. The difference was not statistically significant. Blood pressure and heart rate were not adversely affected by the administration of remifentanil. Respiratory rates decreased in all patients (mean decrease, 8 breaths/min) and one patient transiently developed a respiratory rate of 4 breaths per minute that elicited a decrease in the rate of remifentanil administration. Remifentanil administered at sedation doses does not adversely affect intraoperatively recorded interictal spike activity. Further investigation of the use of this drug during awake epilepsy surgery is warranted.
Inhibition of the NMDA receptor likely contributes to ketamine&#39;s neurodepressive properti... more Inhibition of the NMDA receptor likely contributes to ketamine&#39;s neurodepressive properties. Magnesium also inhibits the NMDA receptor by binding to a site associated with the ketamine-binding domain. Electrophysiological studies suggest that magnesium prevents ketamine from binding to the NMDA receptor and thereby prevents ketamine inhibition. We undertook an in vivo study to determine if magnesium deficiency was associated with an increased sensitivity to ketamine. Weanling rats were maintained on a Mg(2+)-deficient or control diet for 14 days. In Study I, rats were anaesthetized then sacrificed and the Mg2+ concentrations in the brain and plasma were measured. In a second prospective study, experimental animals were rendered hypomagnesaemic and the potency of 125 mg.kg-1 ip ketamine was evaluated. Animals were then were fed a Mg(2+)-containing diet and ketamine sensitivity was re-examined 14 days later. The Mg(2+)-deficient diets rendered the rats hypomagnesaemic as indicated by the brain and plasma concentration of Mg2+. In Study 2, the time to loss of righting reflex was shorter; 1.9 +/- 0.3 min (n = 12) and 2.6 +/- 0.2 min (n = 16, P &lt; 0.05), whereas the latency to toe pinch was prolonged: 25.0 +/- 5.8 min (n = 12) vs 3.1 +/- 2.1 min (n = 16, P &lt; 0.05) in the Mg(2+)-deficient compared with age-matched control animals, respectively. The hypomagnesaemic animals had a higher death rate following ketamine injection. The increased sensitivity to ketamine was no longer apparent when the animals were re-tested following replenishment of Mg2+. Hypomagnesaemia is associated with an increased sensitivity to ketamine.
Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 2003
P Pu ur rp po os se e: : To compare the recovery profiles, efficacy and safety of remifentanil an... more P Pu ur rp po os se e: : To compare the recovery profiles, efficacy and safety of remifentanil and morphine for transitional analgesia with fentanyl in patients undergoing elective craniotomy for supratentorial mass lesions.
Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) a... more Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) among the elderly. This study evaluated the safety and efficacy of propofol PCS among elderly patients undervooing hip or knee a~throplasty. Methods= Forty patients, aged 65-78 yr, undergoing hip or knee arthroplasty under regional anaesthesia were randomized to receive propofol PCS (dose = 0,3 mg,kg ~, delay=three min: n = 20)or anaesthetist-administered midazolam-fentanyl sedation (n=20), Sedation, anxiety and discomfort visual analogue scores (VAS) were measured, by an independent observer, preoperatively, immediately at the end of surgery and one hour following admission to the postanaesthetic care unit (PACU). Cognition was evaluated, using an abbreviated M~ni Mental Status Examination, preoperatively and in the PACU, Patient satisfaction, based on VAS and a brief questionnaire, was measured in the PACU. The incidence of intraoperative complications was also compared. Results: Patient satisfaction was high in each group. Sedation and anxiety VAS were similar in each group, A high incidence of pain with drug injection was noted among patients receiving propofot (80%). -ri-ansient deeper levels of sedation (6 vs I; P=O.05) were observed more commonly in the propofol PCS group. Conclusion: Propofol PCS provides effective sedation, Using a propofol dose of 0.3 mg.kg , transient episodes of deeper sedation were noted more frequently among patients receiving PCS. These episodes did not require intervention but, suggest that this propofol PCS dose approaches the limit of safety and should be fuT~ther reduced for some elderly patients.
Neurolept anaesthesia is used during awake craniotomy for epilepsy surgery. This study compares a... more Neurolept anaesthesia is used during awake craniotomy for epilepsy surgery. This study compares analgesia, sedation and the side effects of the newer opioids sufentanil and alfentanil, with those of fentanyl in patients undergoing awake craniotomy. Thirty patients were randomized into three groups, each received droperidol, dimenhydrinate and the chosen opioid as a bolus followed by an infusion. The opioid doses used were fentanyl 0.75 #g" kg -1 plus 0.01 I~g" kg-l" min-t; sufentanil 0.075 l~g" kg -1 plus 0.0015 gg" kg -~" min -t, and alfentanil 7.5 vg" kg -1 plus 0.5 #g" kg -I" min -1. There were no differences in the requirements for droperidol, dimenhydrinate or in the incidence of complications among 'the three groups. The total doses of the opioids required were fentanyl 4.9 5:L3 vg" kg -1, sufentanil 0.6 + 0.2 ~g" kg -1 and alfentani1149 5:36 I~g" kg-!. Two patients became uncooperative requiring general anaesthesia. The conditions for surgery, electrocorticography and for stimulation testing were satisfactory in all other patients. We conclude that the newer opioids did not offer any benefit over fentanyl. Le traitement chirurgical de l~pilepsie par craniotomie se fait souvent dt l~tat vigile sous neuroleptanalgdsie. Cette dtude vise d comparer l'analgdsie, la sddation et les effets secondaires des nouveaux morphiniques sulfentanil et alfentanil avec le fentanyt chez des malades en cours de cranitomie vigile. Trente patients sont distribuds au hasard en trois groupes, chacun recevant drop$ridol, dimenhydrhlate et un des morphiniques en bolus suivi d'un perfusion. La posologie est pour le fentanyl de 0,75
Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 1999
To examine the learning ability of rats shortly after recovery from a bolus dose of propofol by a... more To examine the learning ability of rats shortly after recovery from a bolus dose of propofol by assessing learning on a swim-to-platform task. Also, muscarinic blockade was used as a pharmacological test of whether learning shortly after propofol anesthesia resembles normal learning. Propofol anesthetized rats (15-20 mg x kg(-1) i.v.) were trained on a swim-to-platform task five to seven minutes after recovering from surgical anesthesia and tested two to three hours later In addition, the muscarinic antagonist scopolamine hydrobromide (5 mg x kg(-1) s.c.) was given to a subgroup of rats before testing. During 10 trials, the number of times a given rat took 10 sec or longer to locate and climb onto a visible platform was tabulated and counted as errors. When trained shortly after recovery from the anesthetic, propofol anesthetized rats made 3.2 +/- 0.4 compared with 1.0 +/- 0.1 errors in controls (P &lt; 0.0001). Two to three hours later both groups performed equally well. Rats trained after propofol anesthesia and given scopolamine before testing made 0.7 +/- 0.5 errors and performed as well as normal controls, 1.2 +/- 0.2 errors when subjected to the same procedures without propofol anesthesia, and better than scopolamine-treated untrained rats, 5.5 +/- 0.7 errors, (P &lt; 0.05). Training five to seven minutes after recovery from propofol anesthesia resulted in normal retention of the swim- to-platform task. It also produced the same resistance to the disruptive effects of scopolamine as did training in rats that were not anesthetized. Thus, the ability to learn recovers rapidly after propofol anesthesia induced by a single intravenous bolus dose.
Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) a... more Purpose: Little information is available regarding the use of patient-controlled sedation (PCS) among elderly patients undergoing operative procedures under local or regional anaesthesia. This prospective, randomized study evaluated the safety of propofol PCS, and the attitude among elderly patients toward self-administration of sedation during cataract surgery. Methods: Prospective, randomized study conducted in a University affiliated, tertiary-care hospital. Fifty-five elderly patients (aged 65-79 yr) were randomized to receive propofol patient-controlled sedation (PCS) (n = 28) or no intraoperarive sedation (n = 27) during cataract surgery performed under peribulbar block. The PCS parameters consisted of a lockout interval of three minutes and a PCS dose of 0.3 mg. kg -/. Study groups were compared with respect to sedation, anxiety and discomfort visual analogue scores (VAS), cognitive functioning, patient satisfaction and the incidence of intraoperative complications. Results: Patients in the PCS group administered a mean propofol dose of 65 • 49 mg during procedures with a mean duration of 46 rain. The incidence of intraoperative complica-
The concentrations of glutamate and ascorbate in brain extracellular fluid increase following sei... more The concentrations of glutamate and ascorbate in brain extracellular fluid increase following seizure activity, trauma and ischemia. Extracellular ascorbate concentration also rises following intracerebral glutamate injection. We hypothesized that glutamate triggers the release of ascorbate from astrocytes. We observed in primary cultures of rat cerebral astrocytes that glutamate increased ascorbate efflux significantly within 30 min. The half-maximal effective concentration of glutamate was 180 " 30 mM. Glutamate-stimulated efflux of ascorbate was attenuated by hypertonic media. 4,4 X -diisothiocyanatostilbene-2,2 X -disulfonic acid inhibited both Na q -dependent glutamate Ž Ž uptake and ascorbate efflux. Two other inhibitors of volume-sensitive organic anion channels 1,9-dideoxyforskolin and 5-nitro-2-3-. . phenylpropylamino benzoic acid did not slow glutamate uptake but prevented stimulation of ascorbate efflux. Glutamate also stimulated the uptake of ascorbate by ascorbate-depleted astrocytes. In contrast, glutamate uptake was not affected by intracellular ascorbate, thus ruling out a putative glutamate-ascorbate heteroexchange mechanism. These results are consistent with activation by glutamate of ascorbate-permeant channels in astrocytes. q
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Papers by Adrian Gelb