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PubMed1984

Comparison of sodium thiopental and methohexital for high-dose barbiturate anesthesia.

High-dose sodium thiopental is frequently used in neuroanesthesia. The authors performed a study to compare a shorter-acting barbiturate, methohexital, to sodium thiopental in producing high-dose barbiturate anesthesia. In two groups of five mongrel dogs each, regional cerebral blood flow (CBF) was determined using the radioactive-microsphere technique, and cardiovascular parameters were measured before, during, and 1 hour after a 1 1/2-hour period of deep barbiturate anesthesia with either sodium thiopental or methohexital. Doses of the barbiturates were adjusted to produce electroencephalogram burst suppression of greater than 30 seconds. Both agents produced a similar degree of cardiac depression, reduction in CBF, and decrease in cerebral metabolic rate of oxygen (CMRO2). Changes in cerebral and peripheral vascular resistance indicated that methohexital caused less vasoconstriction than sodium thiopental. When the barbiturate infusions were discontinued, CMRO2 and CBF returned more rapidly toward control values in the methohexital group than in the thiopental group. The more rapid recovery time and decrease in cerebral vascular resistance with methohexital suggest that it may have some advantage over sodium thiopental during certain neurosurgical procedures.

Anesthesia, Intravenous↗
PubMed1988

Cerebral blood flow, vasoreactivity, and oxygen consumption during barbiturate therapy in severe traumatic brain lesions.

Mean hemispheric cerebral blood flow (CBF) and intracranial pressure (ICP) were measured in 19 severely head-injured patients treated with barbiturate coma. The CBF was calculated from the clearance of tracer substance monitored by extracranial scintillation detectors after intravenous administration of xenon-133. In 11 of the patients cerebral arteriovenous oxygen differences were measured simultaneously. In all patients the effects of pronounced hyperventilation were recorded prior to initiation of barbiturate treatment. A normal CBF response to hyperventilation (delta CBF/delta PaCO2 greater than or equal to 1) was obtained in eight patients. In these patients induction of barbiturate coma was accompanied by physiological decreases in CBF and in the calculated cerebral metabolic rate of oxygen (CMRO2); they also exhibited a rapid and lasting decrease in ICP. A decreased or an abolished CO2 reactivity was recorded (delta CBF/delta PaCO2 less than 1) in 11 patients. In 10 of these 11 patients the physiological decreases in CBF and CMRO2 were not obtained during barbiturate treatment and the decrease in ICP was transitory. This study demonstrates a correlation between cerebral vasoreactivity, physiological effects of barbiturate therapy, and clinical outcome.

Adolescent↗
PubMed1989

[Barbiturate therapy in traumatic cerebral vascular disease: report of two cases].

We report two cases of traumatic cerebral vascular disease which were treated successfully with barbiturate. The first case sustained blunt trauma to the bilateral vertebral arteries, resulting in complete occlusion of both arteries. After ligation of the injured vertebral arteries, multiple cerebral infarction appeared. Cerebral angiography revealed dissection and stenosis of the bilateral internal carotid arteries. We treated this case with barbiturate (Thiamylal) in combination with administration of heparin. The second case sustained cerebral contusion and traumatic subarachnoidal hemorrhage as a result of a motor cycle accident. This patient deteriorated and cerebral angiography showed diffuse cerebral arterial vasospasms. When this was treated with induced hypertension, he developed recurrent subarachnoid hemorrhage. In order to protect the brain from ischemia without elevating blood pressure, we employed barbiturate therapy and the patient recovered without major neurological deficit. The condition of severe head injury with cerebral ischemia is complicated. Therefore it has been hard for neurosurgeons to cure the patient with this condition. But we treated it with barbiturate successfully. Barbiturate therapy in severe head injury with cerebral ischemia may decrease the mortality in that group of patients considered difficult to treat with the usual therapeutic modalities.

Adolescent↗
PubMed1986

[Efficacy and limitation of postoperative barbiturate therapy in severe head injury].

Efficacy and limitation of barbiturate therapy employed as postoperative treatment for acute traumatic intracranial hematomas were studied in 20 patients. The clinical cases in this series included 15 males and 5 females with mean age of 41.8 years who all were operated on for intracranial hematomas within 3 days after injury. Glasgow Coma Scale (GCS) score was less than 7 in all instances and intracranial pressure (ICP) as well as arterial pressure was monitored postoperatively with Gaeltec and Gould transducers. Barbiturate therapy (5 mg/kg of thiopental as an initial dose and loading dose of 2-3 mg/kg/hour) was given when ICP rose above 20 mmHg and maintained for 3 days after operation. The outcome of the patients was assessed by Glasgow Outcome Scale 3 months after injury. The response of barbiturate on ICP and the changes of cerebral perfusion pressure (CPP) during the therapy in relation to the outcome were studied. Final outcome of the patients revealed 5 of good (good recovery and moderate disability), 3 of poor (severe disability and vegetative state) outcomes and 60% of mortality rate. Eleven out of 20 patients responded to barbiturate therapy and 0-20 mmHg of ICP reduction (mean reduction of 10 mmHg) was obtained in these cases. Among these cases, 2 out of 3 dead patients were older than 60 years. There were no responses of barbiturate in 7 patients to whom the therapy was started when ICP rose above 40 mmHg. No response of the therapy on ICP was also observed in the patients with GCS score of 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Nursing management for barbiturate therapy in acute head injuries.

Barbiturate therapy is a controversial mode of therapy instituted in patients with acute head injuries after conventional means of treatment to decrease intracranial hypertension have been unsuccessful. Thiopental is a fast-acting central nervous system depressant and is one of the agents used for barbiturate therapy. Baseline laboratory values and access to four IV sites, including a Swan-Ganz catheterization site, should be obtained prior to institution of barbiturate therapy. While a patient is on barbiturate therapy, it is difficult to assess his clinical status. Nursing care for a patient on barbiturate therapy is an exciting challenge. It is the nurse's responsibility to continuously assess the patient's pressure readings, laboratory values, fluid balance, and pulmonary status to accurately interpret his clinical status.

Blood Chemical Analysis↗
PubMed1978

Structure-activity studies of barbiturates using pattern recognition techniques.

The relationship between molecular structure and duration of depressant effect for barbiturates was investigated. A data set of 160 5,5'-disubstituted barbiturates with various acyclic substituents was coded using 47 numerical descriptors including fragments, substructures, environmental descriptors, and molecular connectivity indexes. All descriptors were derived directly from the connection tables of the barbiturates. Using an interactive error-correction feedback algorithm, linear discriminant functions were developed that could dichotomize the data set with respect to several thresholds separating longer from shorter acting compounds. Feature selection was used to focus on the relatively few structural descriptors sufficient to support linear separability. For three specific thresholds, nine, 11, and nine descriptors were sufficient. The importance of these descriptors and the utility of the technique are discussed. Predictive abilities of approximately 94% were obtained for known barbiturates of the same general molecular types.

Animals↗
PubMed1992

Cholinergic mechanisms in physical dependence on barbiturates, ethanol and benzodiazepines.

The aim of this review is to summarize the effects of acute and chronic treatment with barbiturates, ethanol and benzodiazepines on cholinergic mechanisms in the brains of experimental animals. A single dose of each of these substances reduces the turnover of ACh in the brain. Long-term treatment has the opposite effect; complicated interactions including decreased content of ACh are induced. Barbiturates have been shown to bind stereospecifically to muscarinic and nicotinic receptors in the brain, but this has not been observed for ethanol or the benzodiazepines. The effects on the cholinergic system are affected by the length of treatment and choice of treatment regimen. No effect on cholinergic parameters, such as muscarinic receptors, in the brain is observed on withdrawal of ethanol or barbiturate treatment when the animals are still tolerant towards the substances. The increase in the number of muscarinic receptors observed in several brain regions on withdrawal is seen as a sign of cholinergic supersensitivity. The number of receptors returns to normal when abstinence convulsions have occurred. The assumption of a cholinergic influence is supported by the finding that atropine, given as a single dose on the day of withdrawal of barbital, can prevent the muscarinic receptor changes. Furthermore, long-term barbital or ethanol treatment can induce permanent persistent changes in the cholinergic system in the brain. Cognitive defects and a significant permanent reduction in the content of ACh can be measured in rats which have had long-term barbital treatment. Similarly, a reduced number of muscarinic receptors has been measured in different brain regions of chronic alcoholics. Accumulating data support the role of the cholinergic system in expressing symptoms of physical dependence on barbiturates, ethanol and benzodiazepines as well as in the permanent long-term effects observed after end of treatment.

Animals↗
PubMed1983

Optimization of a novel two-phase potentiometric titration method of barbiturates with mercury (II). Part I: Theory.

A two-phase potentiometric titration procedure for barbiturates with mercury(II) was developed. In the new titration procedure the barbituric acid derivative is dissolved in an aqueous borate buffer. An organic phase consisting of chloroform and benzyl alcohol is added, and the vigourously stirred contents of the titration vessel are titrated by a mercury(II) nitrate solution. The theory of the conditional formation constant in a two-phase system is derived to provide a basis for the selection of optimal titration conditions. It is shown that the new conditional formation constant of the two-phase system, K, increases if the mercury-barbiturate complex is extracted into the organic layer. By extraction of the barbituric acid derivative into the organic layer K is diminished, but this effect can be minimized by a correct choice of the pH of the aqueous layer. The influence of these factors on the pM jump in the equivalence point is demonstrated by calculation of the corresponding theoretical titration curves.

Barbiturates↗
PubMed1982

Differential effects of sedative and anticonvulsant barbiturates on specific [3H]GABA binding to membrane preparations from rat brain cortex.

The sensitivity to barbiturates of [3H]GABA binding to synaptosomal membrane fractions from rat cortex has been examined. We show that a range of anaesthetic/sedative barbiturates enhance GABA binding in the presence of chloride or other ions that interact with the associated ionophore. Furthermore, picrotoxinin and the anticonvulsant barbiturate phenobarbital antagonise the enhancement produced by pentobarbital. These effects are therefore comparable to those observed at benzodiazepine receptors and may be mediated through the chloride ionophore component of the receptor complex. Other classes of anticonvulsants failed to antagonise pentobarbital activation, suggesting that these interactions may occur at a specific barbiturate site in the membrane.

Animals↗
PubMed1983

Contrasting effects of a convulsant (CHEB) and an anticonvulsant barbiturate (phenobarbitone) on amino acid release from rat brain slices.

The effects of a convulsant barbiturate, 5(2-cyclohexylidine-ethyl)-5-ethyl barbituric acid (CHEB), and phenobarbitone (PhB) on the release of exogenous D-aspartate and GABA from slices of rat cerebral cortex were investigated. While PhB inhibited potassium-evoked release of D-aspartate more so than that of GABA, CHEB potently inhibited potassium-evoked GABA release and stimulated evoked D-aspartate release, in a concentration-dependent manner. These actions are consistent with the observed in vivo convulsant and anticonvulsant properties of these barbiturates. CHEB, but not PhB also elevated spontaneous efflux of both amino acids. The actions of these barbiturates were further studied in calcium- and sodium-free media, and in the presence of tetrodotoxin and ruthenium red, agents known to alter ion flux across neuronal membranes. The results obtained indicate that different ionic mechanisms may be involved in the release of excitatory and inhibitory amino acid transmitters.

Animals↗
PubMed1984

Barbiturates, alcohols and the CNS excitatory neurotransmission: specific effects on the kainate and quisqualate receptors.

The effects of barbiturates and straight-chain aliphatic alcohols on the responses of rat striatal neurons to excitatory amino acids have been investigated. The responses to N-methyl-D-aspartate, quisqualate, kainate, L-glutamate and L-aspartate were measured by the increase in 22Na+ efflux rate that they produce in brain slices. The responses to quisqualate and kainate, measured in the 22Na+ efflux assay, were found to be partially blocked by barbiturates whereas the responses to N-methyl-D-aspartate, glutamate and aspartate were not. The kainate and quisqualate-induced increases in 22Na+ efflux rate were much more readily blocked by the presence of aliphatic alcohols than were the responses to N-methyl-D-aspartate, glutamate and aspartate. These results strengthen the idea of the existence of 4 distinct receptors for excitatory amino acids in the rat striatum. They are consistent with the presence on the kainate and quisqualate receptors, but not on the N-methyl-D-aspartate and glutamate/aspartate receptors of a hydrophobic domain which would provide a site of interaction for barbiturates and alcohols. They suggest that receptors for excitatory amino acids can be targets for the actions of barbiturates and alcohols on the central nervous system, and may mediate some of the anesthetic and hypnotic effects of these drugs.

Alcohols↗
PubMed1996

Effects of barbiturates on hypoxic cultures of brain derived microvascular endothelial cells.

An in vitro model of the blood-brain barrier (BBB) consisting of porcine brain derived microvascular endothelial cells (BMEC) seeded onto collagen-coated polycarbonate membranes was used to investigate the effects of the barbiturates, methohexital and thiopental, on permeability properties of the endothelial cell monolayer under hypoxia. The permeability of cultured BMEC to ions and sucrose increased significantly during 6 h of hypoxia in a reversible manner. Cells were resistant to hypoxia for up to 24 h, but 48 h resulted in marked damage as assessed by the release of lactate dehydrogenase activity into the culture medium. The hypoxia-induced increase of the permeability was unchanged in the presence of superoxide dismutase (SOD) and catalase. Methohexital and thiopental decreased the hypoxia-induced permeability increase in a concentration-dependent manner and permeability changes were abolished completely at the barbiturate concentration of 50 micrograms/ml. The barbiturates had no effect on the intracellular cAMP content which started to decline after 3 h of hypoxia. Results suggest that barbiturates at high concentrations might be able to prevent permeability changes of the BBB during cerebral ischemia.

Animals↗
PubMed1975

Comparison of the action of different barbiturates on squid axon membranes.

Experiments utilizing squid giant axons have been carried out to determine if the duration of anesthesia obtained from phenobarbital, pentobarbital and hexobarbital can be explained by events related to their action at the nerve membrane level. For comparison, the barbiturates were perfused both outside and inside the squid axon at concentrations which produced an approximately equivalent depression of the maximum rate of rise of the action potential. The time to 50% maximum block and the time to 50% maximum recovery following washing, were compared for all three drugs. All three barbiturates were more potent from inside the squid axon than from the outside. This finding coupled with the fact that the time course of the drug effects was much shorter when applied inside as compared to outside suggests an internal site of action. There was no statistically significant difference between a short acting barbiturate and a long acting barbiturate with respect to their time course of action or recovery when they were both applied to either the inside or outside of the membrane.

Action Potentials↗
PubMed1984

Barbiturate recognition site on the GABA/benzodiazepine receptor complex is distinct from the picrotoxinin/TBPS recognition site.

The cage convulsant [35S]tert-butylbicyclophosphorothionate [( 35S]TBPS) labels a presumed sedative-convulsant receptor complex. The relative potencies of barbiturates in competing for [35S]TBPS binding parallels their potencies in enhancing benzodiazepine receptor binding. Barbiturates inhibit [35S]TBPS binding in a complex, mixed competitive fashion, leading to a decrease in both the apparent affinity of TBPS for its sites and the apparent number of TBPS sites. All of the barbiturates examined markedly accelerate the dissociation of [35S]TBPS from its recognition sites, while picrotoxinin does not affect the dissociation. These results suggest that the barbiturate and picrotoxinin/TBPS recognition sites are distinct but allosterically linked.

Allosteric Site↗
PubMed1984

Barbiturate and picrotoxin-sensitive chloride efflux in rat cerebral cortical synaptoneurosomes.

The effects of various barbiturates and picrotoxin in modifying the efflux of chloride (36Cl-) was studied in a novel subcellular preparation from rat cerebral cortex, the 'synaptoneurosome'. Dilution of synaptoneurosomes pre-loaded with 36Cl- resulted in rapid efflux of 36Cl- that could be measured as early as 10 s following dilution. In the presence of barbiturates such as pentobarbital and hexobarbital there was a significant increase in 36Cl- efflux which was not observed with the pharmacologically-inactive barbiturate, barbital. The effect of barbiturates in enhancing 36Cl- efflux was also stereospecific [(-)-DMBB greater than (+)-DMBB] and reversed by picrotoxin. By contrast, picrotoxin alone significantly inhibited 36Cl- efflux. These data demonstrate pharmacologically relevant Cl- transport for the first time in a subcellular brain preparation.

Animals↗
PubMed1980

The taste aversion induction properties of two long duration barbiturates.

The ability of sodium phenobarbital (60 mg/kg) and sodium barbital (80 mg/kg) to produce a taste aversion in 23 hr fluid deprived rats was examined using a discrimination or two bottle taste aversion task (0.125% sodium saccharin solution or water). The interaction of both barbiturates with the effects of 3.0 mEq/kg lithium chloride (LiCl) was also examined. Results indicate that phenobarbital treatment alone produces a stronger saccharin aversion than does barbital. Also, barbiturate treatment 24 hr after LICi administration does not attenuate saccharin avoidance, although phenobarbital treatment following LiCl administration was sufficient to induce a maximum aversion that did not extinguish after twenty days of continuous discrimination testing. These data suggest that the aversion inducing properties of the two barbiturates are dissimilar and that phenobarbital is the more effective agent in the production of saccharin aversion. In addition, barbiturate induced attenuation of conditioned taste aversion is apparently related to the periodic forced intake test model since it does not occur when a water and saccharin choice is available.

Animals↗
PubMed1991

Barbiturates inhibit intracellular Ca2+ rise induced by thrombin in rat platelets.

The effects of a number of barbiturates (anesthetic as well as anticonvulsant) on thrombin-induced calcium mobilization were tested in rat platelets using the fluorescent Ca2+ probe Fura-2. All drugs, except barbituric acid and Na-barbital, inhibited the thrombin-induced intracellular Ca2+ rise. Both the uptake of extracellular Ca2+ and the release of calcium from intracellular organelles were affected but influx was inhibited more strongly and at lower concentrations of the drugs (e.g. IC50 of thiopental was 0.83 mM for influx and 1.2 mM for intracellular release). Inhibitory potencies of the various barbiturates were markedly different. Thiopental was the most and barbital the least potent inhibitor. The order of inhibitory potency of the drugs appeared generally to follow their lipid solubility and the order of their hypnotic efficiency, with hexobarbital as the most conspicuous exception. Therefore, barbiturate treatment of cells perturbs agonist-induced calcium mobilization. This effect may be partially linked to their previously reported inhibitory action on two kinases, protein kinase C and phosphatidylinositol 4-phosphate kinase [1, 2].

Animals↗
PubMed1987

Mechanisms by which barbiturates suppress lymphocyte responses to phytohaemagglutinin stimulation.

Certain barbiturates (the intermediate- and short-acting drugs) reduce the growth of PHA-stimulated peripheral blood mononuclear cells, but phenobarbitone (a long-acting drug) is ineffective: replicative growth is more sensitive than activation. This action is associated with a marked reduction in the density of interleukin-2 receptors on the cell membrane and of the numbers of cells expressing them, but the growth rate cannot be restored by supplementation of the tissue culture medium with exogenous interleukin-2. The affected cells show swelling of the mitochondria and cytoplasmic fat globules: the presence of residual bodies and myelin figures indicate an increase in the rate of degradation of organelles. There was no appreciable increase in the number of necrotic cells seen on electron microscopy of cultures exposed to high concentrations of thiopentone or other potent barbiturates, but the presence of debris in the DNA cytogram at 72 h indicated some increase in the death rate of cells exposed to the growth suppressing barbiturates. It would be inadvisable to administer these short- and intermediate-acting barbiturates over long periods, particularly at high dosage, because of the potential danger of iatrogenic immunosuppression.

Adult↗