Child-Pugh versus MELD score in predicting survival in patients undergoing transjugular intrahepatic portosystemic shunt

BACKGROUND

In patients undergoing transjugular intrahepatic portosystemic shunt (TIPS), prognostic scores may identify those with a poor prognosis or even those with a clear survival benefit. The Child-Pugh score (CPS) is well established but several drawbacks have led to development of the model of end stage liver disease (MELD).

AIM

The aim of the study was to compare the predictive power of CPS and MELD, to validate the original MELD formula, and to assess the predictive value of the determinants used in the two prognostic scores outside of a study setting.

PATIENTS

A total of 501 patients underwent elective TIPS placement and 475 patients fulfilled the inclusion criteria.

METHODS

Data of all patients undergoing elective TIPS in one university hospital and four community hospitals in Vienna, Austria, between 1991 and 2001, were analysed retrospectively. The main statistical tests were Cox proportional hazards regression model, the log rank test, Kaplan-Meier analysis, and concordance c statistics.

RESULTS

Median follow up was 5.2 years and median survival was 4.6 years. During follow up, 230 patients died, 75 within three months after TIPS placement. In stepwise proportional hazards analyses, independent predictors of death were creatinine level, bilirubin level, age, and refractory ascites. MELD was better in predicting survival in a stepwise Cox model but both scores were equally predictive in c statistics for one month, three month, and one year survival. Renal function was the strongest independent predictor of survival.

CONCLUSIONS

Although MELD was the primary predictor of overall survival in multivariate analysis, c statistics showed that both scores can be used for patients undergoing TIPS with equal accuracy. For assessing prognosis in patients undergoing TIPS implantation, there seems little reason to replace the well established Child-Pugh score.

Anaesthetic care of patients undergoing primary hip and knee arthroplasty: consensus recommendations from the International Consensus on Anaesthesia-Related Outcomes after Surgery group (ICAROS) based on a systematic review and meta-analysis

BACKGROUND

Evidence-based international expert consensus regarding anaesthetic practice in hip/knee arthroplasty surgery is needed for improved healthcare outcomes.

METHODS

The International Consensus on Anaesthesia-Related Outcomes after Surgery group (ICAROS) systematic review, including randomised controlled and observational studies comparing neuraxial to general anaesthesia regarding major complications, including mortality, cardiac, pulmonary, gastrointestinal, renal, genitourinary, thromboembolic, neurological, infectious, and bleeding complications. Medline, PubMed, Embase, and Cochrane Library including Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, NHS Economic Evaluation Database, from 1946 to May 17, 2018 were queried. Meta-analysis and Grading of Recommendations Assessment, Development and Evaluation approach was utilised to assess evidence quality and to develop recommendations.

RESULTS

The analysis of 94 studies revealed that neuraxial anaesthesia was associated with lower odds or no difference in virtually all reported complications, except for urinary retention. Excerpt of complications for neuraxial vs general anaesthesia in hip/knee arthroplasty, respectively: mortality odds ratio (OR): 0.67, 95% confidence interval (CI): 0.57-0.80/OR: 0.83, 95% CI: 0.60-1.15; pulmonary OR: 0.65, 95% CI: 0.52-0.80/OR: 0.69, 95% CI: 0.58-0.81; acute renal failure OR: 0.69, 95% CI: 0.59-0.81/OR: 0.73, 95% CI: 0.65-0.82; deep venous thrombosis OR: 0.52, 95% CI: 0.42-0.65/OR: 0.77, 95% CI: 0.64-0.93; infections OR: 0.73, 95% CI: 0.67-0.79/OR: 0.80, 95% CI: 0.76-0.85; and blood transfusion OR: 0.85, 95% CI: 0.82-0.89/OR: 0.84, 95% CI: 0.82-0.87.

CONCLUSIONS

Recommendation: primary neuraxial anaesthesia is preferred for knee arthroplasty, given several positive postoperative outcome benefits; evidence level: low, weak recommendation.

RECOMMENDATION

neuraxial anaesthesia is recommended for hip arthroplasty given associated outcome benefits; evidence level: moderate-low, strong recommendation. Based on current evidence, the consensus group recommends neuraxial over general anaesthesia for hip/knee arthroplasty.

TRIAL REGISTRY NUMBER

PROSPERO CRD42018099935.

Society of Anesthesia and Sleep Medicine Guideline on Intraoperative Management of Adult Patients With Obstructive Sleep Apnea

The purpose of the Society of Anesthesia and Sleep Medicine Guideline on Intraoperative Management of Adult Patients With Obstructive Sleep Apnea (OSA) is to present recommendations based on current scientific evidence. This guideline seeks to address questions regarding the intraoperative care of patients with OSA, including airway management, anesthetic drug and agent effects, and choice of anesthesia type. Given the paucity of high-quality studies with regard to study design and execution in this perioperative field, recommendations were to a large part developed by subject-matter experts through consensus processes, taking into account the current scientific knowledge base and quality of evidence. This guideline may not be suitable for all clinical settings and patients and is not intended to define standards of care or absolute requirements for patient care; thus, assessment of appropriateness should be made on an individualized basis. Adherence to this guideline cannot guarantee successful outcomes, but recommendations should rather aid health care professionals and institutions to formulate plans and develop protocols for the improvement of the perioperative care of patients with OSA, considering patient-related factors, interventions, and resource availability. Given the groundwork of a comprehensive systematic literature review, these recommendations reflect the current state of knowledge and its interpretation by a group of experts at the time of publication. While periodic reevaluations of literature are needed, novel scientific evidence between updates should be taken into account. Deviations in practice from the guideline may be justifiable and should not be interpreted as a basis for claims of negligence.

Centrally induced reduction in sympathetic tone-a postsynaptic alpha-adrenoceptor-stimulating action of imidazolines

Naphazoline or oxymetazoline (both 30 mug/kg) were injected into the cisterna magna of anaesthetized cats and reduced blood pressure, heart rate and the electrical discharge rate of small fibre bundles of the preganglionic sympathetic splanchnic nerve. Cats were depleted of endogenous noradrenaline by pretreatment with reserpine (5 mg/kg, 18 h) and alpha-methyl-p-tyrosine (twice 300 mg/kg, 18 and 2 h). In these animals, intracisternal injection of 30 mug/kg oxymetazoline exerted a decrease of sympathetic discharges similar to that described for non-pretreated animals. In noradrenaline-depleted cats intracisternal injection of 1 mug/kg clonidine also decreased the sympathetic discharges. It is concluded that these imidazolines exert their sympathoinhibitory and cardiovascular effects by stimulation of postsynaptic alpha-adrenoceptors in the CNS.

Peripheral nerve block anesthesia/analgesia for patients undergoing primary hip and knee arthroplasty: recommendations from the International Consensus on Anesthesia-Related Outcomes after Surgery (ICAROS) group based on a systematic review and meta-analysis of current literature

BACKGROUND

Evidence-based international expert consensus regarding the impact of peripheral nerve block (PNB) use in total hip/knee arthroplasty surgery.

METHODS

A systematic review and meta-analysis: randomized controlled and observational studies investigating the impact of PNB utilization on major complications, including mortality, cardiac, pulmonary, gastrointestinal, renal, thromboembolic, neurologic, infectious, and bleeding complications.Medline, PubMed, Embase, and Cochrane Library including Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, NHS Economic Evaluation Database, were queried from 1946 to August 4, 2020.The Grading of Recommendations Assessment, Development, and Evaluation approach was used to assess evidence quality and for the development of recommendations.

RESULTS

Analysis of 122 studies revealed that PNB use (compared with no use) was associated with lower ORs for (OR with 95% CIs) for numerous complications (total hip and knee arthroplasties (THA/TKA), respectively): cognitive dysfunction (OR 0.30, 95% CI 0.17 to 0.53/OR 0.52, 95% CI 0.34 to 0.80), respiratory failure (OR 0.36, 95% CI 0.17 to 0.74/OR 0.37, 95% CI 0.18 to 0.75), cardiac complications (OR 0.84, 95% CI 0.76 to 0.93/OR 0.83, 95% CI 0.79 to 0.86), surgical site infections (OR 0.55 95% CI 0.47 to 0.64/OR 0.86 95% CI 0.80 to 0.91), thromboembolism (OR 0.74, 95% CI 0.58 to 0.96/OR 0.90, 95% CI 0.84 to 0.96) and blood transfusion (OR 0.84, 95% CI 0.83 to 0.86/OR 0.91, 95% CI 0.90 to 0.92).

CONCLUSIONS

Based on the current body of evidence, the consensus group recommends PNB use in THA/TKA for improved outcomes.

RECOMMENDATION

PNB use is recommended for patients undergoing THA and TKA except when contraindications preclude their use. Furthermore, the alignment of provider skills and practice location resources needs to be ensured. Evidence level: moderate; recommendation: strong.

The dopamine autoreceptor agonist B-HT 920 stimulates denervated postsynaptic brain dopamine receptors in rodent and primate models of Parkinson's disease: a novel approach to treatment

B-HT 920 (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]azepine), an agonist at alpha 2-adrenoceptors and at dopamine autoreceptors, was tested with respect to stimulation of postsynaptic brain dopamine receptors in mice, rats and rhesus monkeys. In mice B-HT 920 (0.2-20 mg/kg s.c.) injected 4 h after reserpine did not stimulate locomotor activity; this was in contrast to apomorphine (0.1-10 mg/kg s.c.) which elicited locomotor activity in a dose-dependent manner. However, B-HT 920 was effective in inducing locomotor activity when injected 12, 24 and 48 h after reserpine. This effect was dose-dependent and increased with the duration of reserpine pretreatment. In naive rats, B-HT 920 (0.02-2.0 mg/kg s.c.) only decreased exploratory activity and did not elicit stereotyped activity in doses up to 4 mg/kg s.c. This was in contrast to the stereotypy-inducing effect of apomorphine (2.0 and 4.0 mg/kg s.c.). In rats with unilateral striatal ibotenic acid lesion, B-HT 920 (0.2-2.0 mg/kg s.c.) was ineffective in producing significant ipsilateral rotation, whereas apomorphine (0.5-10.0 mg/kg s.c.) was very potent in this model. In rats with unilateral 6-OH-dopamine lesions of the medial forebrain bundle B-HT 920 elicited strong contralateral rotation in a dose-dependent manner (0.02-1.0 mg/kg s.c.). In this model B-HT 920 was equi-effective but long acting when compared with apomorphine. The contralateral rotation produced by B-HT 920 was antagonized by the D2-antagonist sulpiride but not by the D1-antagonist SCH 23390. In rhesus monkeys with severe parkinson-like symptoms induced by MPTP, B-HT 920 in doses of 10 micrograms/kg i.m. and higher restored normal behavior, resulting in complete relief of parkinson symptoms in all animals with 100 micrograms/kg i.m. It is concluded that the property of B-HT 920 to stimulate the 'denervated' supersensitive (reserpine, 6-OH-dopamine, MPTP) but not the normosensitive postsynaptic dopamine receptor in the striatum may represent a novel principle for a specific approach to dopamine substitution treatment of Parkinson's disease.

The central modulatory effect of clonidine on the cardiodepressor reflex after suppression of synthesis and storage of noradrenaline

Rats were decerebrated and treated with a beta-adrenoceptor blocker (toliprolol, Kö 592, 5 mg/kg). Increases of blood pressure were repeatedly elicited by i.v. injection of angiotensin (0.03-0. 125 mug/kg) ant eh accompanying reflex bradycardia was measured. The vagally mediated reflex bradycardia was significantly increased by clonidine, 3o mug/kg i.v., in non-pretreated animals as well as after pretreatment with reserpine (7.5 mg/kg s.c., 20 hr) and alpha-methyl-p-tyrosine-methylester (250 mg/kg i.p., 5 hr), separately or in combination. The facilitatory effect of clonidine was antagonized in all groups by i.v. injection of the alpha-adrenoceptor blocking drugs, phentolamine (5 mg/kg) and piperoxan (1 mg/kg). In the control periods before clonidine, reflex bradycardia was similar in pretreated animals to that in animals without pretreatment. It was concluded therefore that catecholamines have no essential transmitter functions in the cardiodepressor reflex loop. Therefore, the action of clonidine on cardiovascular centers in the medulla is independent of endogenous noradrenaline storage and synthesis. A direct effect is assumed on central alpha-adrenoceptors, which have a modulatory 'effector' function on the cardiodepressor reflex.

Relation between central sympathoinhibitory and peripheral pre- and postsynaptic alpha-adrenoceptors as evaluated by different clonidine-like substances in rats

A series of 8 clonidine-like substances were tested in rats on central sympathoinhibition (heart rate decrease in vagotomized rats, D50 = dose which decreased heart rate by 50 beats/min), peripheral postsynaptic activity (blood pressure increase in spinal rats, PD30 = dose which increased blood pressure 30 mm Hg) and peripheral presynaptic activity (inhibition of tachycardia as elicited by electrical stimulation in the spinal canal of pithed rats, ID50 = dose which inhibited for 50%). The D50, PD30 and ID50 were converted in moles/kg and the negative logarithms thereof were correlated. There was a good correlation between the central effect (D50) and both peripheral effects (PD30 and ID50, respectively; r = 0.89 and 0.91, respectively) provided one drug with low lipoid affinity was omitted from calculation (St 600). There was also good correlation between both peripheral effects (PD30 and ID50; r = 0.94) and this could be extended to other imidazolines which are not acting centrally as antihypertensives (oxymetazoline, naphazoline, St 91, tramazoline; r = 0.90). The results were interpreted by (1) the agonistic activity of the clonidine-like drugs mainly at alpha 2-adrenoceptors and (2) the presence of alpha 2-adrenoceptors at peripheral presynaptic, peripheral postsynaptic as well as central cardiovascular sites.

Investigation into some imidazoline compounds, with respect to peripheral alpha-adrenoceptor stimulation and depression of cardiovascular centers

Peripheral alpha-adrenoceptor stimulation was tested by means of hypertensive effects of the drugs following i.v. injection in spinal rats. Naphazoline (NP), oxymetazoline (OM), St 91-2-(2,6-diethylphenylimino)-2-imidazolidine--and St 1697--2-(2-ethyl, 6-methylphenylimino)-2-imidazolidine--were 3 to 5 times more potent in tthis respect thatn clonidine (CLON) whereas St 363--2-(2,4-dichlorophenylimino)-2-imidazolidine--and xylazine (XY) exerted only approx. 1/20 the effect of that of clonidine. Sympathoinhibitory activity after i.v. injection was tested by the bradycardiac effect in vagotomized rats; St 1697, St 363 and XY were active, approx. 1/10-1/30 of CLON, whereas NP, OM and St 91 were inactive. However, following intracisternal (i.ci.) injection of cardiovascular depression, typical for clonidine: (1) in dogs with blocked beta-adrenoceptors, the drugs facilitated the vagally meditated cardiodepressor reflex in response to baroreceptor stimulation by i.v. injection of angiotensin; (2) in dogs treated with atropine and in (3) vagotomized cats (only NP, OM and St 363) a long lasting decrease in heart rate was observed. Some of the experiments were complicated by increases in blood pressure, due to the "leakage" of small amounts of the highly vasopressor active drugs, from the cisternal spaces into the peripheral circulation. The majority of results indicated, that the central cardiovascular depressor effects of the tested drugs depend on their alpha-adrenoreceptor stimulating potency and on their ability to penetrate from cerebrospinal fluid or from the blood to cardiovascular centers. Relationships between the ability for penetration and the lipoid affinity are discussed.

Binding of an imidazolidine (clonidine), an oxazoloazepin (B-HT 933) and a thiazoloazepin (B-HT 920) to rat brain alpha-adrenoceptors and relation to cardiovascular effects

The specific binding to alpha-adrenoceptors in crude plasma membrane preparations of the rat brain was studied by means of 3H-clonidine (specific radioactivity 26.7 Ci/mmole). Equilibrium binding of 3H-clonidine could be described adequately according to a two-site model with a minor population of high affinity sites (KD1 = 0.4 nM) and a major population of low affinity sites (KD2 = 6.1 nM). The heterogeneity of 3H-clonidine binding was also indicated by a biphasic association rate in kinetic binding studies. In competition experiments with 3H-clonidine concentrations of 0.5 or 4.0 nM respectively, concentration-dependent displacement was observed with the non-radioactive compounds: clonidine, B-HT 920 (2-amino-6-allyl-5, 6, 7, 8-tetrahydro-4H-thiazolo-[5, 4-d]-azepin-dehydrochloride) and B-HT 933 (2-amino-6-ethyl-4, 5, 7, 8-tetrahydro-6H-oxazolo-[5, 4-d]-azepin-dihydrochloride). IC50 values of 3, 21 and 160 nM or 10, 63 and 380 nM respectively were thereby evaluated. Cardiovascular effects were estimated in rats. The blood pressure increase in spinal animals was taken as parameter for alpha-adrenoceptor stimulation at peripheral vascular sites. The bradycardic effect in vagotomized animals was taken as parameter for central nervous sympathoinhibition. The ranking order of the potency of the three drugs was the same in both in vivo tests and parallels the in vitro binding affinities at both binding sites: clonidine greater than B-HT 920 greater than B-HT 933. These results indicate the similarity of the alpha-adrenoceptor structures in brain membrane preparations, at peripheral vascular sites and at central sympathoinhibitory sites.

Presynaptic activity of the imidazolidine derivative ST 587, a highly selective alpha 1-adrenoceptor agonist

St 587 increased the blood pressure of pithed rats. When the antagonists prazosin (alpha 1) and rauwolscine (alpha 2) were used the drug was shown to be a more selective alpha 1-adrenoceptor agonist than methoxamine. St 587 inhibited the tachycardia elicited by sympathetic stimulation in pithed rats. This effect was presynaptic and due to stimulation of alpha 1-adrenoceptors, as revealed by the different antagonism exerted by prazosin and yohimbine (alpha 2), respectively. The existence of presynaptic alpha 1-adrenoceptors is discussed.

Factor Xa and prothrombin: mechanism of action of FEIBA

A complex consisting of activated factor X (FX) (enzyme) and prothrombin (substrate), both highly purified from human plasma and virus inactivated, was formulated, characterised biochemically as well as in animal studies, and given the name Partial Prothrombinase (PPT). In vitro, PPT shortened the clotting time of a high-titre human factor VIII (FVIII) inhibitor plasma in a manner similar to that of the activated prothrombin complex concentrate FEIBA and triggered coagulation in plasma samples in which factor V (FV) is present. In vivo, the ability of PPT to activate coagulation in both chimpanzees and baboons was equivalent to that of FEIBA. PPT also triggered coagulation in a von Willebrand factor(vWF)-deficient dog and controlled bleeding in rabbits with antibody-induced haemophilia A. Thus, studying the mechanism of action of PPT also explains the therapeutic principle of FEIBA.

Modulation of motor activity by alpha 1- and alpha 2-adrenoceptor stimulation in mice

The influence of two alpha-adrenoceptor agonists, clonidine and B-HT 920, on motor activity was tested in mice. Both, clonidine and B-HT 920 (2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]-azepine) in the dose range 30--300 micrograms/kg s.c. effectively inhibited exploratory activity. On the other hand only clonidine, which stimulates alpha 2- and alpha 1-adrenoceptors increased locomotor activity in mice treated with reserpine (5 mg/kg) and apomorphine (3 mg/kg) in the doses of 0.3 and 1 mg/kg i.p. The highly selective alpha 2-agonist B-HT 920 was ineffective under these conditions up to 30 mg/kg i.p. It is concluded, that in mice "sedative" alpha-adrenoceptors are of the alpha 2- and "excitatory" of the alpha 1-type.

Centrally mediated cardiovascular effects of B-HT 920 (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]-azepine dihydrochloride), a hypotensive agent of the "clonidine type"

Intravenous injection of 30 micrograms/kg of B-HT 920 (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]-azepine dihydrochloride) into cats lead initially to an increase in blood pressure and then to a long-lasting decrease in blood pressure and heart rate. The central site of the hypotensive and bradycardiac action was demonstrated by the significantly greater effect after intracisternal (i.ci.) than after intravenous injection of B-HT 920, 3 micrograms/kg. The drug decreased the rate of spontaneous discharges in preganglionic splanchnic nerve fibers of normal and noradrenaline-depleted cats (3 micrograms/kg, i.ci.). Vagally mediated reflex bradycardia elicited by angiotensin injection in beta-adrenoceptor-blocked dogs was facilitated by intracisternal injection of 10 micrograms/kg B-HT 920. Both sympathoinhibition and vagal reflex facilitation were antagonized by the alpha-adrenoceptor-blocking agent piperoxan (50 micrograms/kg, i.ci). Therefore, B-HT 920 can be classified as an agent of the clonidine type, despite its different chemical structure. Quantitative differences between B-HT 920 and clonidine are discussed with respect to the greater alpha 2/alpha 1 adrenoceptor activity ratio of the former drug, as reported previously.

Localization in the CNA of adrenoceptors which facilitate a cardioinhibitory reflex

In dogs (pentobarbitone, 25 mg/kg) the brain was removed rostrally to the pons, leaving the cerebellum intact (decerebrate animals). In other animals the cerebellum was additionally removed (bulbar animals). In all animals beta-adrenoceptors were blocked by toliprolol (5 mg/kg s.c.). Angiotensin (0.025-0.3mug/kg) was repeatedly injected i.v. and the resulting maximal reflex bradycardia was recorded. Intracisternal (i.ci.) injection of clonidine, 0.5 to 1 mug/kg, in decerebrate or i.v. injection of 10 or 30 mug/kg in bulbar animals significantly facilitated the reflex bradycardia. This effect was antagonised by a subsequent injection of piperoxan 50 mug/kg i.ci. in decerebrate or 1 mg/kg i.v. in bulbar animals. It is concluded that the facilitatory action of clonidine is mediated by alpha-adrenoceptors within the medulla oblongata.

Possible function of alpha 1-adrenoceptors in the CNS in anaesthetized and conscious animals

The influence of St 587 (2-(2-chloro-5-trifluoromethylphenylimino)imidazolidine), a selective alpha 1-adrenoceptor agonist which easily penetrates the blood-brain barrier, was tested on behavior and cardiovascular functions, respectively. The substance (up to 10 mg/kg subcutaneously (s.c.)) did not increase the exploratory activity of naive mice. The hexobarbitone 'sleeping' time in mice was reduced in a dose-dependent manner (St 587 ED50 = 14.4 mg/kg s.c.). Haloperidol 10 mg/kg s.c. induced catalepsy which was antagonized by St 587 in a dose-dependent manner (ED50 = 2.7 mg/kg i.p.). Conversely, the alpha 1-adrenoceptor-blocking agents prazosin and corynanthine elicited catalepsy in mice which had been treated with a subthreshold dose (2 mg/kg s.c.) of haloperidol; the ED50 values of the antagonists were 0.26 and 4.7 mg/kg i.p., respectively. In anaesthetized cats blood pressure and heart rate were not affected by 100 micrograms/kg St 587 injected into the left vertebral artery. In conscious dogs with beta-adrenoceptors blocked, the drug was without effect (100 micrograms/kg intracisternally) on vagally mediated reflex bradycardia, as evoked by intravenous noradrenaline injection. As a positive control the alpha 2-adrenoceptor agonist B-HT 920 which is equipotent to St 587 with respect to peripheral vasopressor effects in rats was injected with 10 micrograms/kg intracisternally and facilitated the reflex bradycardia. It is concluded that alpha 1-adrenoceptors within the brain mediate behavioral activation in states of CNS depression but remain without effect on cardiovascular centers.

alpha 2-Adrenoceptor agonistic effect of B-HT 920 in isolated perfused hindquarters of rats

In isolated perfused hindquarters of rats pretreated with reserpine the alpha 2-adrenoceptor selective agonist B-HT 920 decreased the flow dose-dependently. This effect was strongly antagonized by yohimbine and less by prazosin, and the reverse potency was demonstrated for methoxamine. With increasing concentrations of B-HT 920, a half maximal effect was achieved with 10(-6.64) M. This value is discussed wih respect to the antagonistic potency of B-HT 920 at alpha 1-adrenoceptors with a pA2 of 4.9.

alpha-Adrenoceptor subtypes in cardiovascular regulation

A great deal of experimental observations at alpha-adrenoceptors may be explained if two points are considered: (1) the alpha 1-/adrenoceptor ratio (selectivity ratio) of a given drug and (2) the ratio of alpha 1-/adrenoceptors in the target organ or tissue. The alpha 1-/alpha 2-selectivity ratio for 10 agonists was determined in pithed rats by their hypertensive effect in the presence or absence of the antagonists rauwolscine or prazosin, respectively. Treatment with a beta-blocking agent made it possible to test drugs with additional beta-adrenergic potencies (phenylethylamines). Methoxamine exerted the highest alpha 1-/alpha 2-selectivity ratio, the azepine derivative B-HT 920 the lowest ratio, i.e., the highest selectivity for alpha 2-adrenoceptors. Using the two selective agonists methoxamine and B-HT 920, respectively, the alpha 1-/alpha 2-adrenoceptor ratio (importance) in several target systems was estimated (determination of equieffective doses). Results indicated the prevalence of alpha 1-adrenoceptors in the nictitating membrane, and the equal importance of both subtypes at peripheral postsynaptic vascular sites in rats, as well as in cats. At presynaptic sites (cardiac nerve, rats), alpha 2-adrenoceptors are prevalent. A comparison of equieffective doses of B-HT 920 and clonidine in cats indicated the alpha 2-nature of the central adrenoceptors which mediate hypotension.

Effects of alpha 1-acid glycoprotein in different rodent models of shock

It was the aim of the present study to investigate the effects of the acute phase protein alpha 1-acid glycoprotein in different models of shock. The human plasma preparation used was without effect on mortality in lipopolysaccharide-injected mice when administered in two different doses (1 or 0.33 g/kg i.v.) and according to different treatment schedules. The same preparation significantly increased survival rate (48 h) in rats with septic peritonitis. This effect was seen when alpha 1-acid glycoprotein (200 mg/kg i.v.) was given 15 min prior to and 24 h after cecal puncture. All other dose regimes tested were without significant effect on survival rate. A hemorrhagic/hypovolemic shock model (including a defined trauma) in rats resuscitated with 200 mg/kg alpha 1-acid glycoprotein resulted in significantly higher values of mean arterial blood pressure, cardiac output and stroke volume when compared to corresponding values obtained after resuscitation with Ringer's solution or 200 mg/kg albumin i.v. (free of alpha 1-acid glycoprotein; placebo formulation). Taking all other possible mechanisms of alpha 1-acid glycoprotein into consideration, the partially protective effects of the preparation are explained by enhancing the capillary barrier function and thereby maintaining perfusion of vital organs.