The adrenergic receptor antagonist carvedilol interacts with serotonin 2A receptors both in vitro and in vivo

There is increasing support for the potential clinical use of compounds that interact with serotonin 2A (5-HT_2A) receptors. It is therefore of interest to discover novel compounds that interact with 5-HT_2A receptors. In the present study, we used computational chemistry to identify critical ligand structural features of 5-HT_2A receptor binding and function. Query of compound databases using those ligand features revealed the adrenergic receptor antagonist carvedilol as a high priority match. As carvedilol is used clinically for cardiovascular diseases, we conducted experiments to assess whether it has any interactions with 5-HT_2A receptors. In vitro experiments demonstrated that carvedilol has high nanomolar affinity for 5-HT_2A receptors. In vivo experiments demonstrated that carvedilol increases the ethanol-induced loss of the righting reflex and suppresses operant responding in mice, and that these effects are attenuated by pretreatment with the selective 5-HT_2A receptor antagonist M100907. Moreover, carvedilol did not induce the head-twitch response in mice, suggesting a lack of psychedelic effects. However, carvedilol did not activate canonical 5-HT_2A receptor signaling pathways and antagonized serotonin-mediated signaling. It also reduced the head-twitch response induced by 2,5-Dimethoxy-4-iodoamphetamine, suggesting potential in vivo antagonism, allosteric modulation, or functional bias. These data suggest that carvedilol has functionally relevant interactions with 5-HT_2A receptors, providing a novel mechanism of action for a clinically used compound. However, our findings do not clearly delineate the precise mechanism of action of carvedilol at 5-HT_2A receptors, and additional experiments are needed to elucidate the role of 5-HT_2A receptors in the behavioral and clinical effects of carvedilol.

Involvement of the monoaminergic system in the antidepressant-like activity of chromium chloride in the forced swim test

Bio-metal chromium(III) is a crucial microelement for the proper functioning of living organisms. Previous preclinical and clinical studies reported its potential antidepressant properties. The aim of the present study was to examine the effect of antidepressants and noradrenergic and dopaminergic receptor antagonists on chromium chloride (CrCl₃) activity in the forced swim test (FST) in mice and rats. Imipramine (5 mg/kg), fluoxetine (5 mg/kg) and reboxetine (5 mg/kg) but not bupropion (1 mg/kg), administered jointly with CrCl₃ at a dose of 6 mg/kg, reduced the immobility time in the FST in mice. The reduction of the immobility time induced by the active dose (12 mg/kg) of CrCl₃ was completely abolished by propranolol (2 mg/kg, β-adrenoceptor antagonist), SCH 23390 (0.5 mg/kg, a dopamine D₁ receptor antagonist), and partially by prazosin (1 mg/kg, an α₁-adrenoceptor antagonist), yohimbine (1 mg/kg, an α₂-adrenoceptor antagonist) and sulpiryd (50 mg/kg, a dopamine D₂/D₃ receptor antagonist) administration. The locomotor activity was significantly reduced by CrCl₃ + reboxetine treatment, which did not influence the reboxetine enhancement of the antidepressant-like effect of CrCl₃ in the FST. Moreover, CrCl₃ at a dose of 32 mg/kg (although not at 12 mg/kg) significantly reduced the immobility and enhanced the climbing (but not swimming) time in the FST in rats, which indicates the involvement of the noradrenergic pathway in this effect. The present study indicates that the antidepressant-like activity of chromium in the FST is dependent (although to a different extent) on the noradrenergic, dopaminergic and serotonin systems.

Nanosuspension based in situ gelling nasal spray of carvedilol: development, in vitro and in vivo characterization

The objective of the present investigation was to develop in situ gelling nasal spray formulation of carvedilol (CRV) nanosuspension to improve the bioavailability and therapeutic efficiency. Solvent precipitation-ultrasonication method was opted for the preparation of CRV nanosuspension which further incorporated into the in situ gelling polymer phase. Optimized formulation was extensively characterized for various physical parameters like in situ gelation, rheological properties and in vitro drug release. Formation of in situ gel upon contact with nasal fluid was conferred via the use of ion-activated gellan gum as carrier. In vivo studies in rabbits were performed comparing the nasal bioavailability of CRV after oral, nasal, and intravenous administration. Optimized CRV nanosuspension prepared by combination of poloxamer 407 and oleic acid showed good particle size [d (0.9); 0.19 μm], zeta potential (+10.2 mV) and polydispersity (span; 0.63). The formulation containing 0.5% w/v gellan gum demonstrated good gelation ability and desired sustained drug release over period of 12 h. In vivo pharmacokinetic study revealed that the absolute bioavailability of in situ nasal spray formulation (69.38%) was significantly increased as compared to orally administered CRV (25.96%) with mean residence time 8.65 h. Hence, such in situ gel system containing drug nanosuspension is a promising approach for the intranasal delivery in order to increase nasal mucosal permeability and in vivo residence time which altogether improves drug bioavailability.

Management of acute coronary syndromes in developing countries: acute coronary events-a multinational survey of current management strategies

BACKGROUND

The burden of cardiovascular diseases is predicted to escalate in developing countries. We investigated the descriptive epidemiology, practice patterns, and outcomes of patients hospitalized with acute coronary syndromes (ACS) in African, Latin American, and Middle Eastern countries.

METHODS

In this prospective observational registry, 12,068 adults hospitalized with a diagnosis of ACS were enrolled between January 2007 and January 2008 at 134 sites in 19 countries in Africa, Latin America, and the Middle East. Data on patient characteristics, treatment, and outcomes were collected.

RESULTS

A total of 11,731 patients with confirmed ACS were enrolled (46% with ST-elevation myocardial infarction [STEMI], 54% with non-ST elevation-ACS). During hospitalization, most patients received aspirin (93%) and a lipid-lowering medication (94%), 78% received a β-blocker, and 68% received an angiotensin-converting enzyme inhibitor. Among patients with STEMI, 39% did not receive fibrinolysis or undergo percutaneous coronary intervention. All-cause death at 12 months was 7.3% and was higher in patients with STEMI versus non-ST elevation-ACS (8.4% vs 6.3%, P < .0001). Clinical factors associated with higher risk of death at 12 months included cardiac arrest, antithrombin treatment, cardiogenic shock, and age >70 years.

CONCLUSIONS

In this observational study of patients with ACS, the use of evidence-based pharmacologic therapies for ACS was quite high, yet 39% of eligible patients with STEMI received no reperfusion therapy. These findings suggest opportunities to further reduce the risk of long-term ischemic events in patients with ACS in developing countries.

[Assessment by logistic model of hemodynamic changes during general anesthesia]

The anesthesia induction with strong anesthetic agents generally reduces blood pressure. Cardiovascular agents used during anesthesia induce hemodynamic changes. The time courses of systolic (sBP) and diastolic blood pressure (dBP) and heart rate (HR) are expressed as sigmoidal curve. We have found that the hemodynamic changes can be precisely curve-fitted with a logistic function giving non-linear curve. The four parameters of the logistic function present the first asymptote, the last asymptote, the slope at the inflection point, and the time to the inflection point. Moreover, each logistic parameter is used for the effects of drug dose, age and sex differences of subjects on the hemodynamic change. In this review, we introduce the analyses with the logistic function for the changes in sBP, and dBP during preintubation period and HR, sBP, and dBP during infusion of landiolol hydrochloride, an ultra-short-acting beta1-adrenergic receptor blocking agent, which is used for subjects with tachycardia during general anesthesia. The logistic parameters are useful for assessing the hemodynamic response during general anesthesia. The assessment method of the hemodynamic change using the logistic model contributes much to the management of anesthesia.

Activation of BKCa channels via cyclic AMP- and cyclic GMP-dependent protein kinases by eugenosedin-A in rat basilar artery myocytes

BACKGROUND AND PURPOSE

The study investigated whether eugenosedin-A, a 5-hydroxytryptamine and alpha/beta adrenoceptor antagonist, enhanced delayed-rectifier potassium (K(DR))- or large-conductance Ca(2+)-activated potassium (BK(Ca))-channel activity in basilar artery myocytes through cyclic AMP/GMP-dependent and -independent protein kinases.

EXPERIMENTAL APPROACH

Cerebral smooth muscle cells (SMCs) were enzymatically dissociated from rat basilar arteries. Conventional whole cell, perforated and inside-out patch-clamp electrophysiology was used to monitor K(+)- and Ca(2+)-channel activities.

KEY RESULTS

Eugenosedin-A (1 microM) did not affect the K(DR) current but dramatically augmented BK(Ca) channel activity in a concentration-dependent manner. Increased BK(Ca) current was abolished by charybdotoxin (ChTX, 0.1 microM) or iberiotoxin (IbTX, 0.1 microM), but not affected by a small-conductance K(Ca) blocker (apamin, 100 microM). BK(Ca) current activation by eugenosedin-A was significantly inhibited by an adenylate cyclase inhibitor (SQ 22536, 10 microM), a soluble guanylate cyclase inhibitor (ODQ, 10 microM), competitive antagonists of cAMP and cGMP (Rp-cAMP, 100 microM and Rp-cGMP, 100 microM), and cAMP- and cGMP-dependent protein kinase inhibitors (KT5720, 0.3 microM and KT5823, 0.3 microM). Eugenosedin-A reversed the inhibition of BK(Ca) current induced by the protein kinase C activator, phorbol myristyl acetate (PMA, 0.1 microM). Eugenosedin-A also prevented BK(Ca) current inhibition induced by adding PMA, KT5720 and KT5823. Moreover, eugenosedin-A reduced the amplitude of voltage-dependent L-type Ca(2+) current (I(Ca,L)), but without modifying the voltage-dependence of the current.

CONCLUSIONS AND IMPLICATIONS

Eugenosedin-A enhanced BK(Ca) currents by stimulating the activity of cyclic nucleotide-dependent protein kinases. Physiologically, this activation would result in the closure of voltage-dependent calcium channels and thereby relax cerebral SMCs.

Population pharmacokinetics of S(-)-carvedilol in healthy volunteers after administration of the immediate-release (IR) and the new controlled-release (CR) dosage forms of the racemate

Carvedilol is a beta(1)-, beta(2)-, and alpha(1)-adrenoreceptor blocker indicated for treatment of hypertension and mild-to-severe congestive heart failure. The objective of this study was to develop and evaluate a single population model that describes S(-)-carvedilol pharmacokinetics from both the immediate-release (IR) and the new controlled-release dosage forms of the racemate. Carvedilol IR data (1270 measurements) were obtained from 2 open-label studies (50 mg/25 mg Q12 hours for 2 doses). Carvedilol CR data (2058 measurements) were obtained from an open-label, nonrandomized, dose-rising (10, 20, 40, and 80 mg), 4-period balanced crossover study. All data were simultaneously analyzed using NONMEM V. Leverage analysis and internal evaluations were conducted for the final model. A 2-compartment model with first-order absorption and elimination provided the best fit. The model included different absorption rates (KAs) for the CR and IR morning (IR(AM)) and evening (IR(PM)) doses; incorporating change-points at certain times. Estimates of KAs indicated that the absorption was slower at equivalent times and extended for CR relative to IR carvedilol. Oral clearance of S(-)-carvedilol was 149 L/h. The IR(PM) and the CR doses had bioavailability (F(rel)) of 0.80 and 0.76, respectively, relative to the IR(AM) dose. The inter-subject variability in KAs was lower for the CR dosage form than the original IR dosage form. Estimation of interoccasion variability on KAs and F(rel) for the CR dosage form improved the fit. The model performed well in simulation and leverage analysis indicated its robustness. The model will be a useful tool for future simulation studies.

Forearm vasoconstrictor response in uncomplicated type 1 diabetes mellitus

BACKGROUND

According to the 'haemodynamic hypothesis', increased tissue perfusion predisposes to microangiopathy in diabetic patients. We hypothesized that the typical haemodynamic changes underlying the increased tissue perfusion can be explained by a decreased sympathetic nerve activity caused by chronic hyperglycaemia. In this study we investigated sympathetic activity in patients with uncomplicated type 1 diabetes mellitus (DM).

MATERIALS AND METHODS

In 15 DM patients (DM duration 6.3 +/- 3.8 year; HbA1c 7.9 +/- 1.3%) and 16 age- and sex-matched healthy volunteers (Control), sympathetic nervous system activity was measured at rest (baseline) and during sympathoneural stimulation (lower body negative pressure (LBNP)) by means of interstitial and plasma noradrenaline (NA) sampling and power spectral analysis. Muscle sympathetic nerve activity (MSNA) was measured before (baseline) and during a cold pressure test. Forearm blood flow was measured during forearm vascular alpha- and beta-adrenergic receptor blockade.

RESULTS

At baseline, forearm vascular resistance (FVR), plasma NA concentrations, MSNA and heart rate variability were similar in both groups. LBNP-induced vasoconstriction was significantly attenuated in the DM group compared with the Control group (DeltaFVR: 12 +/- 4 vs. 19 +/- 3 arbitrary units, P < 0.05). The responses of plasma NA and heart rate variability did not differ.

CONCLUSIONS

Baseline FVR and sympathetic nerve activity are normal in patients with uncomplicated type 1 diabetes. However, the forearm vasoconstrictor response to sympathetic stimulation is attenuated, which cannot be attributed to an impaired sympathetic responsiveness.

Severe hypertension in pregnancy: Hydralazine or labetalol

OBJECTIVE

The objective was to compare the safety and efficacy of intravenous labetalol and intravenous hydralazine for acutely lowering blood pressure in pregnancy.

STUDY DESIGN

Two hundred women with severe hypertension in pregnancy were randomized to receive hydralazine (5 mg as a slow bolus dose given intravenously, and repeated every 20 min up to a maximum of five doses) or labetalol (20-mg intravenous bolus dose followed by 40 mg if not effective within 20 min, followed by 80 mg every 20 min up to a maximum dose of 300 mg). The primary end point was successful lowering of blood pressure and maternal hypotension.

RESULTS

Women were similar with respect to characteristics at randomization. No significant differences were observed for maternal hypotension or persistent severe hypertension; only two patients in the hydralazine group presented with hypotension. Palpitations (p=0.01) and maternal tachycardia (p=0.05) occurred significantly more often in patients treated with hydralazine. The main neonatal outcomes were very similar per group; however, hypotension and bradycardia were significantly more frequent in the labetalol group. There were two neonatal deaths per antihypertensive drug group.

CONCLUSIONS

This randomized clinical trial shows that labetalol and hydralazine fulfill the criteria required for an antihypertensive drug to treat severe hypertension in pregnancy.

Different vascular responses in glabrous and nonglabrous skin with increasing core temperature during exercise

To elucidate the characteristics of vasomotor control in glabrous and nonglabrous skin during dynamic exercise, we compared the vascular responses in both areas to increasing core temperature during the cycle exercise for 30 min at different intensities in the range 20-60% of peak oxygen consumption (VO(2peak)) in a total of 13 male and four female subjects in two experimental protocols. Skin blood flow was monitored using laser Doppler flowmetry. In protocol 1, the slope of the relationship between esophageal temperature (T (es)) and cutaneous vascular conductance (CVC) in the early phase of the exercise decreased (P < 0.05) with increasing exercise intensity at glabrous sites (palm) but not nonglabrous sites (dorsal hand). In protocol 2, to examine whether a difference in vascular responses in the two areas is due to the adrenergic vasoconstrictor system, the release of norepinephrine from adrenergic nerves in forearm and palmar skin was blocked locally by iontophoresis of bretylium tosylate (BT). The administration of BT diminished completely the change of CVC in the palm during the exercise but did not alter the response in the forearm compared with the untreated site. In the two areas, neither the T (es) threshold for vasodilation nor the change in CVC above the threshold in the middle and late phase of the exercise was influenced by the intensity of the exercise. These results suggest that, in the early phase of the exercise, light-to-moderate exercise reduces in an intensity-dependent manner the thermal sensitivity for vasodilation in glabrous skin but not nonglabrous skin via an adrenergic vasoconstrictor pathway.

Ventricular Hypertrophy and Hypertension

Left ventricular hypertrophy (LVH) is a strong, independent predictor of cardiovascular events and all-cause mortality. Patients with LVH are at increased risk for stroke, coronary heart disease, congestive heart failure, and sudden cardiac death. Hypertension is a major influence on the development of LVH. The prognostic power of LVH is likely multifactorial. LVH represents both a manifestation of the effects of hypertension and other cardiac risk factors over time as well as an intrinsic condition causing pathologic changes in cardiac structure and function. Angiotensin II plays a central role in the development of LVH. Several antihypertensive treatments, especially angiotensin II receptor blockers, can reverse LVH and improve cardiovascular outcomes independent of blood pressure reduction. Further studies are required to determine if these agents should become first-line therapy for all patients with hypertension and LVH.

Study of effects of antiglaucoma eye drops on N-methyl-D-aspartate-induced retinal damage

PURPOSE

To study the effects of antiglaucoma eye drops on N-methyl-D-aspartate (NMDA)-induced retinal damage.

METHODS

Several antiglaucoma eye drops, beta-blockers, alpha/beta-blockers, an alpha1-blocker, an alpha2-agonist, and a prostaglandin derivative, were topically administrated to NMDA-treated rat eyes daily for 2 weeks, and the retinal thickness, the number of retrograde-labeled retinal ganglion cells (RGCs), and the results of a cDNA microarray analysis were studied.

RESULTS

Intravitreal administration of NMDA caused a significant decrease in the thickness of the retinal layers and induced upregulation of glial fibrillary acidic protein (GFAP). Topical administration of beta-blockers (timolol, betaxolol, and carteolol) and a prostaglandin derivative (latanoprost) showed almost no significant effects on retinal thickness, the number of RGCs, or expression of GFAP. In contrast, the alpha/beta-blockers (nipradilol and levobunolol), the alpha1-blocker (bunazosin HCl), and the alpha2-agonist (brimonidine) showed preservation effects on retinal thickness and the number of RGCs, and marked suppression of NMDA-induced upregulation of GFAP. Among 1101 genes related to cellular regulatory mechanisms, the expression of two genes, both for insulin-like growth factors, (IGF-1) and ErbB3, was altered upon administration of the alpha/beta-blockers, the alpha1-blocker, and the alpha2-agonist.

CONCLUSION

Our present study suggests that modulations of the alpha-adrenergic receptor, alpha1-blocking and alpha2-stimulation, by antiglaucoma eye drops may cause beneficial effects on NMDA-induced retinal damage in the rat.

Labedipinedilol-C: A Third-Generation Dihydropyridine-Type Calcium Channel Antagonist Displaying K+ Channel Opening, NO-Dependent and Adrenergic Antagonist Activities

Intravenous and oral labedipinedilol-C showed a dose-dependent long-lasting hypotension and a decrease of heart rate in normotensive and conscious spontaneously hypertensive rats (SHR). In isolated Wistar rat and guinea pig tissues, labedipinedilol-C competitively antagonized (-)isoproterenol-induced cardiac stimulation, tracheal relaxation, and phenylephrine-, CaCl2-, and high-K-induced aorta contractions in a concentration-dependent manner. The estimated pA2 and pKCa values were 8.22+/-0.04 and 7.11+/-0.52, respectively. [H]CGP-12177 binding to ventricle and lung tissues as well as [H]prazosin and [H]nitrendipine binding to brain membranes were inhibited by labedipinedilol-C with Ki values of 2.86, 9.03, 0.39, and 0.05 muM, respectively. The vasorelaxant effects of labedipinedilol-C on phenylephrine (10 microM)-induced contractions were attenuated by removing endothelium, by pretreatment with soluble guanylyl cyclase (sGC) inhibitors ODQ (10 microM) and methylene blue (10 microM), a NOS inhibitor L-NAME (100 microM), a K channel blocker TEA (10 mM), a KATP channel blocker glibenclamide (1 microM), and Ca-dependent K channel blockers apamin (1 microM) and charybdotoxin (0.1 microM). In human umbilical vein endothelial cells (HUVECs), labedipinedilol-C increased NO release, which was significantly inhibited by L-NAME. The Western blot analysis on HUVECs indicated that labedipinedilol-C increased the expression of eNOS. These results indicate that hypotension effects of labedipinedilol-C result from alpha-adrenoceptor and Ca entry-blocking activities and release of NO or NO-related substance from vascular endothelium. The endothelium-independent relaxation of vascular smooth muscle is probably linked to K channel opening and alpha-adrenoceptor-blocking activities.

Adrenoceptor subtypes in the control of burn-induced plasma extravasation

Burn trauma is known to induce a significant rise in circulating catecholamine levels and despite catecholamines being potent endogenous vasoactive agents with known actions on microvascular permeability, their effect on burn edema has been poorly investigated. The present study in rats investigated the role and importance of adrenergic receptor subtypes in the regulation of basal capillary permeability in normal skin and hyperpermeability in partial- and full-thickness skin burns. Edema was quantified by spectrophotometric analysis of extravasated Evans blue-albumin. Evaluation was based on intravenous administration of the following adrenergic agonists and antagonists: l-phenylephrine (alpha(1)-receptor agonist), prazosin (alpha(1)-receptor antagonist), clonidine (alpha(2)-receptor agonist), yohimbine (alpha(2)-receptor antagonist), prenalterol (beta(1)-receptor agonist), terbutaline (beta(2)-receptor agonist), or propranolol (beta(1)- and beta(2)-receptor antagonist). Results showed increased capillary permeability in normal skin following administration of terbutaline (p<0.01) and yohimbine (p<0.01). In partial-thickness burns, clonidine significantly (p<0.05) reduced edema formation, whereas in full-thickness burns edema was significantly reduced by clonidine (p<0.05) and l-phenylephrine (p<0.01). In conclusion, the inhibition of postburn edema induced by stimulation of alpha(1)-receptors (l-phylephrine) and alpha(2)-receptors (clonidine) could be secondary to increased vascular resistance and reduced tissue perfusion pressure and/or suppressed inflammatory reaction in the burn injury. In the treatment of burn patients, clonidine is particularly interesting since the agent has previously been proven to induce potent analgesia in thermally injured.

Regulation of postburn ischemia by α- and β-adrenoceptor subtypes

Deep skin burns are characterised by progressive ischemia secondary to vasoconstriction and thrombosis formation. Burn trauma elicits increased sympathetic activity and elevation of circulating catecholamines acting on adrenoceptors in vascular tissue playing an important role in the regulation of organ blood flow. The present study in rats investigated the role of alpha- and beta-adrenoceptors in the circulatory changes taking place in normal skin and in partial- and full-thickness skin burns using laser Doppler flowmetry. Evaluation was based on intravenous administration of the following adrenergic agonists and antagonists: l-phenylephrine (alpha(1)-agonist), prazosin (alpha(1)-antagonist), clonidine (alpha(2)-agonist), yohimbine (alpha(2)-antagonist), prenalterol (beta(1)-agonist), terbutaline (beta(2)-agonist), and propranolol (beta(1)- and beta(2)-antagonist). Blood flow in normal skin was reduced by phenylephrine (p<0.001), clonidine (p<0.001) and propranolol (p<0.01), and increased by prazosin (p<0.05), yohimbine (p<0.05), prenalterol (p<0.05) and terbutaline (p<0.01). In partial-thickness burns, blood flow was reduced by phenylephrine (p<0.01), clonidine (p<0.01) and propranolol (p<0.05). In full-thickness burns, only clonidine reduced perfusion (p<0.05). In conclusion, beta(1)- and beta(2)-adrenoceptors play important role in the physiological regulation of skin perfusion but are of lesser importance for postburn skin perfusion. Vasoconstrictive alpha(1)- and alpha(2)-adrenoceptors were shown to be tonically active in normal skin and in partial-thickness burns, exerting a negative effect on skin perfusion which was further potentiated by exogenous administration of alpha(1)- and alpha(2)-agonists and reversed by selective alpha-blockers. In full-thickness burns, activation of alpha(2)-receptors was shown to significantly impair skin circulation, raising a flag of warning for the use of clonidine to treat pain in burn patients.

Noradrenergic System Interacts With Genital Reflexes Induced by Cocaine in Paradoxical Sleep-Deprived Male Rats

Different doses of alpha-1, alpha-2, beta-1, and beta-2 adrenoceptor agonists or antagonists were administered to paradoxical sleep-deprived (PSD) rats prior to cocaine administration. Methoxamine reduced the percentage of rats displaying erection, whereas prazosin did not. Yohimbine significantly decreased this percentage. For beta-1 adrenoceptor drugs, both compounds reduced the percentage of rats displaying erection at the highest dose; beta-2 adrenoceptor drugs had no effect. Except for clonidine, all drugs significantly reduced the frequency of erection. Ejaculation was significantly decreased following yohimbine and beta-1 drugs, whereas it was completely abolished by prazosin. The results showed that noradrenergic drugs inhibited genital reflexes in PSD rats, with distinct responses in relation to their respective action over the adrenoceptor.

Sympathetic, sensory, and nonneuronal contributions to the cutaneous vasoconstrictor response to local cooling

Previous work indicates that sympathetic nerves participate in the vascular responses to direct cooling of the skin in humans. We evaluated this hypothesis further in a four-part series by measuring changes in cutaneous vascular conductance (CVC) from forearm skin locally cooled from 34 to 29 degrees C for 30 min. In part 1, bretylium tosylate reversed the initial vasoconstriction (-14 +/- 6.6% control CVC, first 5 min) to one of vasodilation (+19.7 +/- 7.7%) but did not affect the response at 30 min (-30.6 +/- 9% control, -38.9 +/- 6.9% bretylium; both P < 0.05, P > 0.05 between treatments). In part 2, yohimbine and propranolol (YP) also reversed the initial vasoconstriction (-14.3 +/- 4.2% control) to vasodilation (+26.3 +/- 12.1% YP), without a significant effect on the 30-min response (-26.7 +/- 6.1% YP, -43.2 +/- 6.5% control; both P < 0.05, P > 0.05 between sites). In part 3, the NPY Y1 receptor antagonist BIBP 3226 had no significant effect on either phase of vasoconstriction (P > 0.05 between sites both times). In part 4, sensory nerve blockade by anesthetic cream (Emla) also reversed the initial vasoconstriction (-20.1 +/- 6.4% control) to one of vasodilation (+213.4 +/- 87.0% Emla), whereas the final levels did not differ significantly (-37.7 +/- 10.1% control, -37.2 +/- 8.7% Emla; both P < 0.05, P > 0.05 between treatments). These results indicate that local cooling causes cold-sensitive afferents to activate sympathetic nerves to release norepinephrine, leading to a local cutaneous vasoconstriction that masks a nonneurogenic vasodilation. Later, a vasoconstriction develops with or without functional sensory or sympathetic nerves.

In Vivo and In Vitro Characterization of the Novel Antiarrhythmic Agent SSR149744C

SSR149744C (SSR, 2-butyl-3-[4-[3-(dibutylamino)pro-pyl]benzoyl]-1-benzofuran-5-carboxylate isopropyl fumarate), is a new non-iodinated benzofuran derivative. The aim of this study was to evaluate in vivo its electrophysiological, hemodynamic, and anti-adrenergic properties and to determine its mechanism of action using in vitro studies. In chloralose-anesthetized dogs, SSR149744C (1-10 mg/kg i.v.) prolonged the sinus cycle length, A-H interval, Wenckebach cycle length, atrial effective refractory period (ERP), and atrio-ventricular node ERP in a dose-dependent manner without change of ventricular ERP and HV, QRS, or QTc intervals. Arterial blood pressure and ventricular inotropism were slightly decreased. SSR149744C, which has no or low affinity for alpha 1 and beta 1 adrenergic and angiotensin II AT1 receptors, reduced isoproterenol-induced tachycardia and phenylephrine- or angiotensin II-induced hypertension in anaesthetized dogs. In guinea pig papillary muscle, SSR149744C did not modify the resting potential, action potential amplitude and duration, but reduced the dV/dt max of the depolarization phase in a frequency-dependent manner. In isolated guinea pig cardiomyocytes and transfected CHO cells, SSR149744C (0.01-30 microM) inhibited several potassium currents: IKr (IC50 approximately 10 microM), IKs (IC50 approximately 30 microM), IK(ACh) (IC50 = 0.09 microM), and IKv1.5 (IC50 = 2.7 microM), the L-type calcium current: ICa(L) (IC50 approximately 5 microM) and also the amplitude of [Ca2+]i transient and cell shortening. Therefore, SSR149744C appears to have a multifactorial mechanism of action, which combines the blockade of several ion channels with the inhibition of responses of alpha 1 and beta 1 adrenergic as well as AT1 receptor stimulation. Like amiodarone, SSR149744C possesses the pharmacological effects of class I, II, III, and IV antiarrhythmic agents, which may confer upon this new drug a strong antiarrhythmic potential without ventricular proarrhythmia and iodine-related amiodarone-like side-effects.

Glomus jugulare tumors with intracranial extension

Glomus tumors provide unique surgical challenges for both tumor resection and defect reconstruction. Tumors with intracranial extension compound these challenges. Surgical techniques have evolved, and now, with a multidisciplinary team, single-stage surgeries are the standard. In this paper the authors will report the results of the Otology Group protocol for surgical management of glomus tumors with intracranial extension. Particular attention will be paid to prevention of cerebrospinal fluid leaks with the use of vascularized tissue for defect reconstruction.

Nonhypotensive autonomic agents in veterinary ophthalmology

The parasympathetic and sympathetic divisions of the autonomic nervous system are involved in homeostatic control of a wide variety of ocular functions, including accommodation, pupillomotor control, lacrimation, eyelid position, and aqueous humor production. Familiarity with the functional anatomy of the autonomic nervous system is paramount to the understanding and application of the large number of autonomic drugs used in veterinary ophthalmology. The cholinergic and adrenergic agents discussed in this article are commonly employed to facilitate routine ophthalmic examination, in the diagnosis of autonomic dysfunction, and in the treatment of a variety of ocular diseases.

Evaluation of Carvedilol for the Treatment of Portal Hypertension

Development of bleeding gastroesophageal varices is a serious consequence of portal hypertension secondary to cirrhosis. Nonselective beta-blockers have been used to reduce portal pressures and prevent primary and secondary bleeding episodes. However, up to two thirds of patients may not respond appropriately to these agents. Nonselective beta-blockers combined with vasodilatory drugs result in enhanced lowering of portal pressures by targeting several mechanisms involved in this process. Unfortunately, this practice is associated with increased adverse effects, such as hypotension, and minimal reductions in mortality. Carvedilol possesses both nonselective beta-antagonist and alpha1-receptor antagonist activity. Given its combined mechanism of action, carvedilol presents a potential option for lowering portal pressures. Its effects on lowering portal pressures and its role in therapy are undefined. Using MEDLINE (1966-2003) and International Pharmaceutical Abstracts (1970-2003), the English-language literature was searched to identify human studies assessing carvedilol's effects on lowering portal pressure. In general, carvedilol therapy was associated with mean reductions of 16-43% in portal pressure, assessed by the hepatic venous pressure gradient (HVPG) after single and multiple doses. Studies comparing carvedilol with propranolol revealed equal or enhanced efficacy in lowering HVPG. Large percentages of patients had significant HVPG reductions to levels that prevent variceal bleeding. Carvedilol also was associated with substantial symptomatic hypotension, especially in patients with ascites or Child-Pugh class B or C cirrhosis. Efficacy and adverse effects generally seem to be dose related. Carvedilol appears to be a potentially viable option for treating portal hypertension. Further multiple-dose trials comparing carvedilol with standard therapy are needed to assess the agent's long-term safety and effectiveness in preventing variceal bleeding.

Efficacy of carvedilol treatment on cardiac function and cardiac sympathetic nerve activity in patients with dilated cardiomyopathy: comparison with metoprolol therapy

Carvedilol and metoprolol have been reported to be effective in the treatment of patients with chronic heart failure. However, to our knowledge, there have been no studies comparing the effects of the 2 drugs on cardiac function, including cardiac sympathetic nerve activity.

METHODS

We compared 15 patients with dilated cardiomyopathy (DCM) who were receiving carvedilol (group A) with 15 patients with DCM who were receiving metoprolol (group B). Before and after 1 y of treatment, cardiac (123)I-metaiodobenzylguanidine ((123)I-MIBG) uptake was assessed using the total defect score (TDS) and the heart-to-mediastinum (H/M) activity ratio from the delayed images. The New York Heart Association (NYHA) class and echocardiographic left ventricular ejection fraction (LVEF) also were assessed.

RESULTS

In both groups, the TDS decreased (in group A, from 25 +/- 14 to 16 +/- 14, P < 0.01; in group B, from 27 +/- 9 to 19 +/- 10, P < 0.01), the H/M increased (in group A, from 1.67 +/- 0.31 to 2.01 +/- 0.36, P < 0.01; in group B, from 1.68 +/- 0.21 to 1.93 +/- 0.32, P < 0.01), the LVEF increased (in group A, from 31% +/- 10% to 48% +/- 10%, P < 0.01; in group B, from 28% +/- 9% to 47% +/- 15%, P < 0.01), and the NYHA functional class improved (in group A, from 2.9 +/- 0.3 to 1.7 +/- 0.5, P < 0.01; in group B, from 2.8 +/- 0.6 to 1.7 +/- 0.6, P < 0.01). The change in LVEF was mildly correlated with the change in the TDS in group A (r = 0.41) as well as in group B (r = 0.53). In the patients with a favorable response in the TDS or H/M, the NYHA class improved more than in the patients without a favorable response (P < 0.05).

CONCLUSION

Carvedilol treatment can improve cardiac function, symptoms, and cardiac sympathetic nerve activity in patients with DCM to a similar extent as metoprolol treatment. The improvement of cardiac function and symptoms is related to the improvement of cardiac sympathetic nerve activity.

Pharmacologic management of integrative brain failure

Integrative brain failure is often a comorbidity of critical illness, and although not uncommon, is perhaps the least understood of all the various organ failure phenomena. Factors that contribute to integrative brain failure include inadequate management of pain, stress, anxiety, and the several underlying mechanisms that create agitation in the intensive care unit patient. Delirium, a resultant organic mental syndrome, is reversible when promptly recognized and aggressively managed. The nurse who is astute in clinical assessments and skillful in the management of the environment of care can prevent and control states of anxiety, irritability, restlessness, and sleep disturbances that contribute to the development of delirium.

Multiple dose pharmacokinetics of fiduxosin under fasting conditions in healthy elderly male subjects

Selective alpha1a-adrenoceptor antagonists are effective agents for treatment of benign prostatic hyperplasia, a disorder occurring in middle-aged and elderly males. The objective of this study was to determine the pharmacokinetics of fiduxosin, a novel alpha1a-adrenoceptor antagonist, following multiple dose administration. This was carried out in a Phase I, randomized, double-blind, placebo-controlled, parallel group, multiple oral dose study of fiduxosin. Single once-daily oral doses of 30, 60, 90 or 120 mg of fiduxosin or placebo were administered to healthy elderly male subjects (n = 48; 8 active and 4 placebo per dosing group) for 14 consecutive days. Fiduxosin plasma concentration-versus-time profiles for days 1, 7 and 14 were used to assess fiduxosin pharmacokinetics. Steady state was achieved by day 7. At steady-state mean Tmax (time to maximum plasma concentration), CL/F (apparent oral clearance) and Vbeta/F (apparent volume of distribution) ranges were 1.8-7.8 h, 27.3-47.2 L h(-1) and 846-1399 L, respectively. Tmax and VbetaF were independent of dose. Cmax (maximum plasma concentration), Cmin (minimum plasma concentration) and AUC24 (area under plasma concentration vs time curve from 0 to 24 h) for days 7 and 14 were linearly proportional with dose overthe 30-120 mg/day dose range and were unchanged from day 7 to day 14. It was concluded that fiduxosin multiple-dose pharmacokinetics were dose-independent and time-invariant over the 30-120 mg/day dose range under fasting conditions.

The involvement of alpha2-adrenoceptors in the anticonvulsive effect of swim stress in mice

RATIONALE

Various studies have shown that stressful manipulations in rats and mice lower the convulsant potency of GABA-related, but also some GABA-unrelated convulsants. The mechanism of this anticonvulsive effect of stress is still unknown.

OBJECTIVES

We tested the possible involvement of alpha2-adrenoceptors in the previously observed anticonvulsive effect of swim stress.

METHODS

The mice were, prior to exposure to swim stress and the IV infusion of picrotoxin, pre-treated with clonidine (an alpha2-adrenoceptor agonist), yohimbine (a non-selective alpha2-adrenoceptor antagonist), idazoxan (a selective alpha2-adrenoceptor antagonist), or niguldipine (an alpha1-adrenoceptor antagonist), and the latency to the onset of two convulsant signs was registered.

RESULTS

In control unstressed animals clonidine (0.1 and 1 mg/kg IP), yohimbine (2 mg/kg IP) and idazoxan (1 mg/kg IP) failed to affect the doses of picrotoxin needed to produce convulsant signs, while niguldipine (5 mg/kg IP) prolonged the latency, i.e. it enhanced the doses of picrotoxin producing running/bouncing clonus and tonic hindlimb extension. In swim stressed mice clonidine enhanced, while idazoxan decreased doses of picrotoxin needed to produce two convulsive signs. Yohimbine decreased the dose of convulsant needed to produce tonic hindlimb extension, while niguldipine enhanced doses of picrotoxin needed to produce both symptoms.

CONCLUSIONS

The results demonstrate the alpha2-adrenoceptor agonist-induced potentiation and alpha2-adrenoceptor antagonist-induced diminution of the anticonvulsive effect of stress. Additionally, they show the anticonvulsive effect of niguldipine in unstressed and stressed animals. Hence, the results suggest that alpha2-adrenoceptors are involved in the anticonvulsive effect of swim stress in mice.

Sympathetic innervation of mammary glands mediates suckling-induced reflex inhibition of milk yield in rats

Previous work has shown that physiologic activation of the sympathetic system may inhibit milk yield (ME) in rats. Thus, adrenal catecholamines (CAs) are released by suckling, but it is not known whether such inhibition results also from reflex activation by the same stimulus of neural sympathetics upon the mammary gland. The present experiments were designed to determine whether suckling inhibits ME induced by oxytocin (OT) in the urethane-anesthetized lactating rat, and whether such inhibition results from adrenal and/or neurally released CAs. Rats were isolated (6 h) from their pups and then anesthetized. OT (0.8 mU every 2 min) was administered intravenously to the mothers during suckling. Rats were either chronically implanted with cannulae into the lateral cerebral ventricles (intracerebroventricularly), bilaterally adrenalectomized (ADX), hypophysectomized (HX), spinal cord transected (SCT: T3-T4), or had the nipple area (NA) locally anesthetized before suckling. MEs were low in control, sham, ADX and HX rats, but not in rats given the beta-adrenergic blocker propranolol (PROP; intravenously or intracerebroventricularly injected), nor in SCT, NA or PROP-HX rats. As revealed by ductal resistance measurements as an indicator of ductal tone, suckling-induced inhibition of ME was due to ductal constriction within the mammary glands. These effects of suckling, however, could be prevented by prior activation of ductal mechanoreceptors. Together, these results indicate that suckling inhibits ME through the reflex activation of neurally mediated central beta-adrenergic mechanisms, and that these effects, in turn, can be regulated by ductal mechanoreceptor activation.

Adjunctive therapies in the treatment of acute coronary syndromes

Survival after myocardial infarction has been improving steadily in recent decades, in part because of more effective adjunctive medical therapies. However, the issue of underutilization of effective medical therapies remains. Adjunctive therapy for acute myocardial infarction should include aspirin, beta-adrenergic blocking agents, angiotensin-converting enzyme inhibitors, and lipid-lowering agents, all of which improve survival in the treatment and secondary prevention of myocardial infarction. This review presents the current knowledge supporting the use of specific adjunctive pharmacologic agents and also discusses the current status of other agents that are emerging or controversial.

[NO synthase activity in epitheliocytes of the rat bronchi following inhalation administration of adrenergic agonists and guanosine triphosphate]

NO synthase was studied in intact rats and in rats with bronchial asthma epitheliocytes after inhalation of phenotherol, propranolol, guanosine triphosphate (GTP) and combined inhalation of GTP with phenotherol. NO synthase mediator action on bronchial patency during adrenoagonists and GTP inhalation was demonstrated.

Adrenoceptor subtype involvement in suppression of prolactin secretion by noradrenaline

In sheep, injection of noradrenaline suppresses prolactin secretion by a direct effect at the pituitary gland. The aims of this study were to use primary cultures of ovine pituitary cells to examine the receptor subtypes that mediate the inhibitory effect of noradrenaline on prolactin secretion and, by using receptor antagonists in vivo, determine whether noradrenaline acts as a prolactin release-inhibiting factor (PIF). Noradrenaline and dopamine suppressed prolactin secretion from ovine pituitary cells with ED50s of 60.9+/-46.6 and 1.5+/-1.0x10-9 mol/l, respectively (P<0.05). The in-vitro prolactin release-inhibiting effect of noradrenaline (10-7 mol/l) was not blocked by the dopamine antagonists pimozide (D2) or SCH23390 (D1) but was blocked by each of the adrenoceptor antagonists (alpha1-adrenoceptor antagonists prazosin and WB4101, the alpha2-adrenoceptor antagonist yohimbine and the beta-adrenoceptor antagonist propranolol). The response to adrenoceptor agonists was also tested in vitro. The alpha1-adrenoceptor agonists phenylephrine and cirazoline significantly suppressed prolactin. Of the alpha2-agonists, clonidine had no effect whereas oxymetazoline and p-aminoclonidine both suppressed prolactin. The beta-adrenoceptor agonist isoproterenol also suppressed prolactin while the specific beta3-antagonist BRL37344 had no effect. When the adrenoceptor antagonists were tested in vivo in ewes manipulated to be in the luteal phase, only WB4101 significantly (P<0.05) increased plasma prolactin concentrations but this response was small and only observed in one of two experiments. In summary, these experiments suggest that adrenoceptors and not dopamine receptors are responsible for the inhibitory effect of noradrenaline on prolactin secretion in vitro but do not implicate a particular adrenoceptor subtype. The in-vivo experiments do not provide convincing evidence for a role for noradrenaline as a physiologically important PIF.

Antiadrenergic effect of chronic amiodarone therapy in human heart failure

OBJECTIVES

The aim of the present study was to evaluate the influence of amiodarone on neurochemical parameters of sympathetic nervous activity in patients with congestive heart failure.

BACKGROUND

Unlike most antiarrhythmic agents, amiodarone has been shown to exert a beneficial effect on survival in some studies of patients with congestive heart failure. The pharmacology of this agent is complex, and as such, the mode of its action is unclear in humans. Some experimental studies suggest that amiodarone exerts a sympatholytic effect.

METHODS

To evaluate the effect of amiodarone on sympathetic nervous activity, we measured the total systemic and cardiac norepinephrine (NE) spillover rate by isotope dilution in 58 patients with severe heart failure (left ventricular ejection fraction 20 +/- 1%), 22 of whom were receiving chronic amiodarone treatment. Release rates for dihydroxyphenylalanine (DOPA, a precursor of NE), and endogenous and radiolabeled dihydroxyphenylglycol (DHPG and 3H-DHPG, intraneuronal metabolites of NE and 3H-NE, respectively) were also determined to assess sympathetic neuronal integrity.

RESULTS

Amiodarone-treated patients had significantly lower cardiac spillover rates for NE (42%, p = 0.001), DOPA (74%, p < 0.001), DHPG (44%, p < 0.01) and 3H-DHPG (51%, p < 0.01) than those patients not treated with amiodarone. Hemodynamic assessment of amiodarone-treated patients revealed higher cardiac output (4.4 +/- 0.2 vs. 3.7 +/- 0.2 liters/min, p < 0.01), and slightly lower pulmonary capillary wedge pressure (18 +/- 2 vs. 22 +/- 1, p = NS) than in untreated patients. After correction for the potential confounding effect of hemodynamic differences, amiodarone-treated patients continued to demonstrate significantly lower spillover rates of NE, DOPA and DHPG from the heart.

CONCLUSIONS

These data indicate that amiodarone may exert beneficial effects on the failing human heart through a sympatholytic process, and this action appears to be relatively cardioselective.

Role of adrenoceptors in vasopressin, oxytocin and prolactin responses to conditioned fear stimuli in the rat

Conditioned fear or novel environmental stimuli suppress vasopressin (VP) and augment oxytocin (OT) and prolactin (PRL) release in rats. We examined the effects of intracerebroventricular (i.c.v.) injections of adrenoceptor antagonists on these neuroendocrine responses to conditioned fear or novel environmental stimuli in male rats. A beta1 antagonist, metoprolol, blocked the VP but not the OT or PRL response to conditioned fear stimuli, but did not abolish neuroendocrine responses to novel environmental stimuli. A beta2 antagonist, ICI118551, impaired the PRL but not the VP or OT response to fear or novel environmental stimuli. In rats injected with a alpha1 adrenoceptor antagonist, benoxathian, conditioned fear stimuli did not significantly induce the VP, OT or PRL responses. The effects of benoxathian were not due to a general reduction of arousal, since benoxathian did not prevent the VP, OT or PRL response to novel environmental stimuli. These data suggest that beta1 adrenoceptors play a selective role in the VP response to conditioned fear stimuli, as do beta2 adrenoceptors in the prolactin response to conditioned fear and novel environmental stimuli. We conclude that alpha1 adrenoceptors play a facilitative role in VP, OT, PRL responses to conditioned fear stimuli.

Pituitary-adrenal, hormonal changes during induced hypotension with labetol or isoflurane for middle-ear surgery

BACKGROUND

Pituitary-adrenal secretion during induced hypotension for middle-ear surgery has received little attention. Previous work failed to differentiate the effects of induced hypotension from surgical stimulation. We have undertaken a preliminary study examining the effects of hypotension, achieved with labetalol or isoflurane, on pituitary-adrenal secretion before, during and after middle-ear surgery.

METHODS

Twenty-four patients were allocated randomly to 3 groups. The control group were anaesthetised with isoflurane, and normotension maintained for 30 min before hypotension was induced with isoflurane and surgery started. In the labetalol group, this drug was given i.v. to obtain a mean arterial pressure (MAP) of 60 mm Hg for 30 min before surgery and hypotension maintained with labetalol during the operation. In the isoflurane group, hypotension was induced to a MAP of 60 mm Hg for 30 min before surgery and continued throughout the procedure. All 3 groups received metoprolol i.v. before hypotension was established. Blood samples were collected before induction of anaesthesia, during anaesthesia alone (normotensive or hypotensive), surgery with hypotension, and recovery. They were analysed for adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), cortisol and aldosterone.

RESULTS

Induced hypotension before surgery failed to stimulate release of ACTH, AVP and cortisol. No significant increase in these hormones occurred until the postoperative period. Aldosterone concentrations increased significantly during anaesthesia and hypotension in the labetalol and isoflurane groups (P<0.05) and continued to rise significantly in all 3 groups during surgery. However, there was no significant difference in aldosterone concentration before surgery between the control and the 2 hypotensive groups.

CONCLUSION

ACTH, AVP and cortisol secretion were not stimulated by induced hypotension to MAP of 60 mm Hg before surgery. Increased aldosterone secretion occurred and a further study with a larger sample size is needed.

Chronopharmacologic considerations when treating the patient with hypertension: a review

Recognition of the existence of circadian variation in exacerbation of cardiovascular disease may have relevance to clinical use of cardioactive agents. Physiologic rational for the chronobiology of cardiac disease exists and can provide a basis on which to examine the efficacy of agents to manage cardiac disease. The use of 24-hour ambulatory blood pressure monitoring (ABPM) devices have advanced our ability to describe the interplay of chronobiologic rhythms and pharmacodynamic response to antihypertensive medications. This review summarizes the studies evaluating the use of various antihypertensive medications in the context of using 24-hour blood pressure monitoring devices. The studies are described in an attempt to increase awareness of chronobiology and potential implications of designing chronotherapeutic regimens.

Oral and topical treatment of erectile dysfunction. Present and future

A great deal of progress has been made in the pharmacological treatment of erectile dysfunction. At present, however, the most effective therapies require intracavernosal injections with a number of associated drawbacks. An increasing number of oral and transdermal agents have been introduced clinically or are at various phases in their development. It is evident that severe end-organ disease probably will not result in successful systemic therapy. Nevertheless, in men with intact or mildly dysfunctional erectile mechanisms, noninvasive treatments can offer some measure of success. Further study of individual and synergistic activity of available compounds is underway.

Continuous thermodilution cardiac output: agreement with Fick and bolus thermodilution methods

OBJECTIVE

Cardiac outputs were determined with continuous thermodilution, bolus thermodilution, and the Fick method during pharmacologically varied hemodynamics.

DESIGN

Prospective comparison of techniques.

SETTING

University animal laboratory.

PARTICIPANTS

Swine.

INTERVENTIONS

Swine were anesthetized, tracheally intubated, and instrumented to measure continuous (QTDC) and bolus (QTDB) thermodilution cardiac outputs and sample arterial and mixed venous blood. Continuous thermodilution of blood was facilitated by computer modulation of a thermal filament wrapped around the portion of the pulmonary artery catheter residing in the right atrium and ventricle. QTDC was computed from the thermodilution curve monitored by the thermistor. Bolus thermodilution was performed in triplicate by injecting 10 mL of 5% dextrose in water (0 to 4 degrees C). Oxygen consumption (VO2) was calculated as the averaged minute rate of disappearance of spirometer oxygen over a 6-minute steady state. Cardiac output was determined with the direct Fick method (QF) by dividing VO2 by the difference in arterial and mixed venous oxygen content. Basal QTDC was increased and decreased with an intravenous infusion of dobutamine or labetalol, respectively. Data are summarized as mean +/- SD or 95% confidence interval (CI 95%). Agreement between methods of determining cardiac output was assessed by calculating bias, percent bias, and percent coefficient of determination (100 r2).

MEASUREMENTS AND MAIN RESULTS

Eighteen swine (38.9 +/- 1.2 kg) exhibited a range of QTDC from 2.2 to 14.8 L/min. Mean measurement variance of VO2, CaO2, CvO2, and QTDB was 1.5%, 1.5%, 2.0%, and 11.8%, respectively. Mean bias, percent bias, and 100 r2 was 0.004 +/- 1.05 L/min (CI 95%: 0.18 to 0.19 L/min), -0.37 +/- 13.8% (CI 95%: -2.75 to 2.01), and 89% between QTDC and QF, respectively. Bias, percent bias, and 100 r2 was 0.05 +/- 1.09 L/min (CI 95%: -0.14 to 0.23 L/min, 1.21 +/- 13.06% (CI 95%: -1.03 to 3.46%), and 91% between QTDC and QTDB, respectively. Bias, percent bias, and 100 r2 (Fig 6) was -0.04 +/- 0.69 L/min (CI 95%: -0.16 to -.08 L/min), -1.23 +/- 9.17% (CI 95%: -2.8 to 0.35%), and 94% between QTDB and QF, respectively.

CONCLUSION

Automatic cardiac output computed with continuous thermodilution appears accurate and reliable. Also, good agreement was confirmed between cardiac output derived by continuous and bolus thermodilution methods and bolus thermodilution and Fick methods.