Dramatic rise in plasma viremia after CD8(+) T cell depletion in simian immunodeficiency virus-infected macaques

To determine the role of CD8(+) T cells in controlling simian immunodeficiency virus (SIV) replication in vivo, we examined the effect of depleting this cell population using an anti-CD8 monoclonal antibody, OKT8F. There was on average a 99.9% reduction of CD8 cells in peripheral blood in six infected Macaca mulatta treated with OKT8F. The apparent CD8 depletion started 1 h after antibody administration, and low CD8 levels were maintained until day 8. An increase in plasma viremia of one to three orders of magnitude was observed in five of the six macaques. The injection of a control antibody to an infected macaque did not induce a sustained viral load increase, nor did it significantly reduce the number of CD8(+) T cells. These results demonstrate that CD8 cells play a crucial role in suppressing SIV replication in vivo.

Distinct pathogenic sequela in rhesus macaques infected with CCR5 or CXCR4 utilizing SHIVs

Infection of macaques with chimeric simian-human immunodeficiency virus (SHIV) provides an excellent in vivo model for examining the influence of envelope on HIV-1 pathogenesis. Infection with a pathogenic CCR5 (R5)-specific enveloped virus, SHIVSF162P, was compared with infection with the CXCR4 (X4)-specific SHIVSF33A.2. Despite comparable levels of viral replication, animals infected with the R5 and X4 SHIV had distinct pathogenic outcomes. SHIVSF162P caused a dramatic loss of CD4+ intestinal T cells followed by a gradual depletion in peripheral CD4+ T cells, whereas infection with SHIVSF33A.2 caused a profound loss in peripheral T cells that was not paralleled in the intestine. These results suggest a critical role of co-receptor utilization in viral pathogenesis and provide a reliable in vivo model for preclinical examination of HIV-1 vaccines and therapeutic agents in the context of the HIV-1 envelope protein.

The absolute bioavailability of caffeine in man

The absolute bioavailability of orally administered caffeine was investigated in 10 healthy adult male volunteers, aged 18.8 to 30.0 years. The subjects were administered a 5 mg/kg dose of caffeine as either an aqueous oral solution or an intravenous infusion, on separate occasions about 1 week apart, in a randomized crossover fashion. Plasma samples were collected over the 24-h period following each dose and assayed for their caffeine content using a high-performance liquid chromatographic technique. The oral absorption was very rapid, reaching a peak (Tp) plasma concentration after 29.8 +/- 8.1 min (mean +/- SEM). In addition, the variation in the maximum plasma concentration (Cmax) was low, 10.0 +/- 1.0 micrograms/ml. The absolute bioavailability was assessed by comparing the areas under the plasma concentration vs. time curves for the intravenous and oral doses of caffeine. The rapid absorption resulted in essentially complete bioavailability of the oral caffeine, F(%) = 108.3 +/- 3.6%. The caffeine plasma half-lives varied from 2.7 to 9.9 h, indicating substantial inter-subject variability in its elimination.

A multivariate study of determinants of vigorous exercise in a community sample

The purpose of this study was to explore the associations between several social learning theory variables and self-reported vigorous exercise and to consider the implications for exercise promotion. A random sample of adults in San Diego, California, was surveyed by mail. The 2,053 respondents (response rate, 43.4%) overrepresented Caucasian, affluent, and well-educated groups. A model of 24 variables accounted for 0.27 of the variance in exercise, and results strongly supported social learning theory. The strongest correlates were self-efficacy (i.e., confidence in the ability to exercise in specific situations), perceived barriers to exercise, modeling, dietary habits, support from friends, and age. Smoking was inversely associated with exercise in men only. We encourage researchers to conduct intervention trials to test the hypotheses generated in this study.

Physiology is pivotal for interactions between salinity and acute copper toxicity to fish and invertebrates

The present paper presents original data and a review of the copper (Cu) toxicity literature for estuarine and marine environments. For the first time, acute Cu toxicity across the full salinity range was determined. Killifish, Fundulus heteroclitus, eggs were hatched in freshwater (FW), 2.5, 5, 10, 15, 22 and 35 ppt (seawater, SW) and juveniles were allowed to acclimate for 7 days prior to acute toxicity testing. Sensitivity was highest in FW (96 h LC50: 18 microg/l), followed by SW (96 h LC50: 294 microg/l) with fish at intermediate salinities being the most tolerant (96 h LC50 > 963 microg/l at 10 ppt). This approximately 50-fold, non-linear variation in sensitivity could not be accounted for by Cu speciation or competition among cations but can be explained by physiology. The relative Na(+) gradient from the blood plasma to the water is greatest in FW followed by SW and is smallest at 10 ppt. Regression of Cu toxicity versus the equilibrium potential for Na(+), which reflects the relative Na(+) gradient, revealed that 93% of the variation can be attributed to Na(+) gradients and thus osmoregulatory physiology. Examination of the existing literature on acute Cu toxicity in SW (defined as >25 ppt) confirmed that early life stages generally are most sensitive but this pattern may be attributable to size rather than developmental stage. Regardless of developmental stage and phylogeny, size clearly matters for Cu sensitivity. The existing literature on the influence of salinity on acute Cu toxicity as well as studies of mechanisms of Cu toxicity in fish and invertebrates are reviewed.

Compact radio emission indicates a structured jet was produced by a binary neutron star merger

The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size and displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after the merger by using a global network of 32 radio telescopes. The apparent source size is constrained to be smaller than 2.5 milli-arc seconds at the 90% confidence level. This excludes the isotropic outflow scenario, which would have produced a larger apparent size, indicating that GW170817 produced a structured relativistic jet. Our rate calculations show that at least 10% of neutron star mergers produce such a jet.

The ability of an oligomeric human immunodeficiency virus type 1 (HIV-1) envelope antigen to elicit neutralizing antibodies against primary HIV-1 isolates is improved following partial deletion of the second hypervariable region

Partial deletion of the second hypervariable region from the envelope of the primary-like SF162 virus increases the exposure of certain neutralization epitopes and renders the virus, SF162DeltaV2, highly susceptible to neutralization by clade B and non-clade B human immunodeficiency virus (HIV-positive) sera (L. Stamatatos and C. Cheng-Mayer, J. Virol. 78:7840-7845, 1998). This observation led us to propose that the modified, SF162DeltaV2-derived envelope may elicit higher titers of cross-reactive neutralizing antibodies than the unmodified SF162-derived envelope. To test this hypothesis, we immunized rabbits and rhesus macaques with the gp140 form of these two envelopes. In rabbits, both immunogens elicited similar titers of binding antibodies but the modified immunogen was more effective in eliciting neutralizing antibodies, not only against the SF162DeltaV2 and SF162 viruses but also against several heterologous primary HIV type 1 (HIV-1) isolates. In rhesus macaques both immunogens elicited potent binding antibodies, but again the modified immunogen was more effective in eliciting the generation of neutralizing antibodies against the SF162DeltaV2 and SF162 viruses. Antibodies capable of neutralizing several, but not all, heterologous primary HIV-1 isolates tested were elicited only in macaques immunized with the modified immunogen. The efficiency of neutralization of these heterologous isolates was lower than that recorded against the SF162 isolate. Our results strongly suggest that although soluble oligomeric envelope subunit vaccines may elicit neutralizing antibody responses against heterologous primary HIV-1 isolates, these responses will not be broad and potent unless specific modifications are introduced to increase the exposure of conserved neutralization epitopes.

Mucosal transmission and induction of simian AIDS by CCR5-specific simian/human immunodeficiency virus SHIV(SF162P3)

Nonhuman primate models are increasingly used in the screening of candidate AIDS vaccine and immunization strategies for advancement to large-scale human trials. The predictive value of such macaque studies is largely dependent upon the fidelity of the model system in mimicking human immunodeficiency virus (HIV) type 1 infection in terms of viral transmission, replication, and pathogenesis. Herein, we describe the efficient mucosal transmission of a CCR5-specific chimeric simian/human immunodeficiency virus, SHIV(SF162P3). Female rhesus macaques were infected with SHIV(SF162P3) after a single atraumatic application to the cervicovaginal mucosa. The disease course of SHIV(SF162P3)-infected monkeys is similar and as varied as natural HIV infection in terms of viral replication, gradual loss of CD4(+) peripheral blood mononuclear cells, and the development of simian AIDS-defining opportunistic infections. The SHIV(SF162P3)/macaque model should facilitate direct preclinical assessment of HIV vaccine strategies in addition to antiviral compounds directed towards envelope target cell interactions. Furthermore, this controlled model provides the setting to investigate immunologic responses and putative host-specific susceptibility factors that alter viral transmission and subsequent disease progression.

Intergeniculate leaflet and suprachiasmatic nucleus organization and connections in the golden hamster

The intergeniculate leaflet (IGL) is a distinct subdivision of the lateral geniculate complex which receives retinal input and projects upon a circadian pacemaker, the suprachiasmatic nucleus (SCN). In the present study, we have analyzed the organization of the IGL and its connections in the hamster, a species commonly used in circadian rhythm studies. The location of the IGL is defined by the presence of retinal afferents demonstrated by anterograde transport of cholera toxin-HRP, neuropeptide Y-containing neurons and axons, cells retrogradely labeled from the regions of the SCN and contralateral IGL, and substance P-containing axons. It is a long nucleus extending the entire rostrocaudal axis of the geniculate. The most rostral IGL lies between the lateral dorsal thalamus, ventrolateral part, and the horizontal cerebral fissure. It then enlarges ventral to the rostral dorsal lateral geniculate, medial to the optic tract. The mid-portion of the leaflet is a thin lamina intercalated between the dorsal and ventral geniculate nuclei. The extended caudal portion of the nucleus lies lateral and ventral to the medial geniculate and is contiguous with the zona incerta and the lateral terminal nucleus. The IGL contains populations of neuropeptide Y (NPY+) and enkephalin (ENK+) neurons which project to the retinorecipient portion of the SCN. In addition to the immunoreactive perikarya, the IGL contains plexuses of NPY+, ENK +, substance P-, serotonin-, and glutamic acid decarboxylase-immunoreactive axons.

Retrograde transport studies demonstrate that, in addition to the NPY+ neurons, there is a population of non-NPY+ neurons projecting upon the SCN. There is also a reciprocal projection upon the IGL from neurons in the SCN region, particularly the retrochiasmatic area. The hamster SCN differs from the rat in containing a distinct subdivision of substance P-immunoreactive neurons.

Cyclodextrins in the treatment of a mouse model of Niemann-Pick C disease

Niemann-Pick type C (NPC) is a neurodegenerative disorder characterized by greatly altered somatic cholesterol metabolism. The NPC1 gene has recently been cloned and shown to have sequence homology to other sterol-sensing proteins. We have used a mouse model with a disrupted npc1 gene to study the effects of the cholesterol-mobilizing compound, 2-hydroxypropyl-beta-cyclodextrins (HPBCD), on the clinical course of this disorder. Treatment with two HPBCDs, with varying levels of 2-hydroxypropyl substitution, had effects in delaying neurological symptoms and in decreasing liver cholesterol storage while a third HPBCD was without effect. The ameliorating effect was not improved by longer exposure times (commencement of exposure in utero), however, it is not known if there is transplacental transfer of HPBCDs. The combination of HPBCD with probucol or nifedipine (which have previously been shown to lower liver cholesterol in this animal model) markedly decreased liver storage of unesterified cholesterol without altering the depressed levels of esterified cholesterol. The slight effects of the HPBCDs on neurological symptoms may be partially due to their apparent non-permeation of the blood-brain barrier (BBB). This non-permeation was assayed with radioactive tracers and was also present in the mdr1a knockout mice which have greatly increased BBB permeability for many drugs. Intrathecal delivery of HPBCD by an Alzet osmotic minipump did not improve its efficacy in ameliorating neurological symptoms.

Depletion of brain serotonin by 5,7-DHT modifies hamster circadian rhythm response to light

The midbrain raphe complex innervates the circadian rhythm regulating system by direct projections to the suprachiasmatic nucleus (SCN) and the intergeniculate leaflet (IGL). The present experiments examined the changes in circadian rhythm regulation consequent to the depletion of brain serotonin by central 5,7-dihydroxytryptamine (DHT) application. Adult male hamsters with access to running wheels were entrained to a light-dark cycle 14:10 (LD) of photoperiod, pre-treated with desmethylimipramine and given bilateral lateral ventricle infusions of 75 micrograms DHT/2.5 microliters 0.5% ascorbic acid in saline or vehicle only. Two separate experiments were performed. Four weeks after surgery, animals were transferred to either constant light (LL; Experiment 1) or constant dark (DD; Experiment 2). Animals remained in LL for 85 days, then were transferred to DD for 50 days, followed by a return to LD 14:10 for 14 days. Animals in Expt. 2 remained in DD for 55 days, were given 3 days food deprivation, then, beginning 35 days later, were periodically exposed to 30 min light pulses as a phase response curve (PRC) to light was generated. DHT treatment induced rapid appearance of advanced activity onset, delayed offset and longer duration of the nocturnal activity phase. DHT animals in LL had circadian locomotor rhythms much longer than control animals (24.43 +/- 0.04 vs 24.19 +/- 0.05 h) and normal circadian rhythmicity was rapidly lost by DHT animals in LL. There was no effect of DHT on circadian period in DD, but the DHT treated animals in DD had a larger phase delay region of the PRC than did controls and this was associated with an overall change in the temporal properties of the PRC. Serotonin immunohistochemistry showed an approximate 90% loss of cells from the dorsal raphe nucleus and decreased density of the serotonergic terminal field in the SCN and IGL. The results support the view that the serotonergic system modulates the phasic actions of light on the hamster circadian rhythm system. The data also indicate that hamsters can have a Type 0 PRC.

In vitro evaluation of pluronic F127-based controlled-release ocular delivery systems for pilocarpine

The overall objective of this study was to develop pluronic F127 (PF127)-containing formulations of pilocarpine hydrochloride (PHCL) suitable for controlled-release ocular delivery of PHCL. Various aqueous formulations were evaluated containing 1% w/v PHCL and 25% w/v PF127 alone or with one of the following additives present: poly(ethylene glycol) 4600 (PEG), poly(vinylpyrrolidone) 10,000 (PVP), poly(vinyl alcohol) 10,000 (PVA), methylcellulose 15 cP (MC), and hydroxypropyl methylcellulose 80-120 cP (HPMC). The in vitro dissolution of the PF127 formulations and the pilocarpine release profiles from them were obtained simultaneously at 34 degrees C and room temperature using a membraneless in vitro model. It was observed that the PEG- and PVP-containing PF127 formulations of PHCL dissolved the quickest and released the drug at a significantly faster rate than the control PF127 formulation, which had no additive present. The PF127 formulations of PHCL containing MC or HPMC exhibited the slowest dissolution rates and released the drug the slowest. The same rank order was observed at each temperature for the dissolution and PHCL release profiles of each formulation. On the basis of the in vitro results, the PF127 formulations of PHCL containing MC or HPMC as an additive showed potential for use as controlled-release ocular delivery systems for PHCL.

Controlled-release delivery system for the alpha-MSH analog melanotan-I using poloxamer 407

The overall objective of these studies was to develop a controlled-release formulation of Melanotan-I (MT-I) containing poloxamer 407 (P407). Various aqueous formulations were evaluated containing MT-I and 25% w/v P407 alone, or with one of the following additives present, i.e., poly(vinylpyrrolidone) 10000 (PVP), methylcellulose (MC), or hydroxypropyl methylcellulose (HPMC). The in-vitro release profiles of MT-I from the P407 formulations and the dissolution of the gel were obtained simultaneously using a membraneless in-vitro model. These data were obtained at 37 degrees C and room temperature (24 degrees C). It was observed that the PVP-containing P407 formulations of MT-I accelerated the dissolution of gel and the release of the peptide compared to the control formulation. The formulations containing MC or HPMC exhibited the slowest dissolution rates and release of MT-I. The same rank order was observed for the dissolution and release profiles of MT-I from the various formulations at both temperatures. The in-vivo release kinetics of selected formulations were analyzed in guinea pigs following intraperitoneal administration. The plasma concentration-time profiles showed an extended release of the peptide formulated with gel compared to the intraperitoneal administration of MT-I in solution. On the basis of the in-vitro and in-vivo results, the P407 formulations of MT-I with MC or HPMC as an additive showed potential for use as a controlled-release delivery system for MT-I.

Comparative pharmacokinetics of caffeine in young and elderly men

The pharmacokinetic behavior of caffeine was compared in a group of eight healthy young men aged 20.5 +/- 2.0 years (mean +/- SD), and in a group of eight healthy, elderly men aged 71.2 +/- 3.9 years. Each subject was given a 5 mg/kg dose of caffeine as either an aqueous oral solution or an intravenous infusion over 30 min using a randomized crossover design. Plasma and urine samples were collected for 24 hr following each dose and analyzed for caffeine content using high-performance liquid chromatography. The peak times (tmax), peak concentrations (Cmax), and the percentage of the peroral dose systemically available, F(%), were essentially identical in both age groups, indicating that caffeine was absorbed rapidly and completely after peroral administration. These results also indicated that the first-pass metabolism observed in rats following the peroral administration of caffeine does not occur in either human group studied here. The elimination of caffeine during its terminal disposition phase was log-linear. Several between-group comparisons of other pharmacokinetic parameters were made. Although the average elimination rate constant was greater in the elderly, the difference did not reach statistical significance, possibly because of the considerable intersubject variability in the elimination rate of caffeine, with half-lives ranging from 2.27 to 9.87 hr. The average apparent volume of distribution was significantly lower in the elderly subjects while the clearances were slightly, but not significantly, larger in the elderly subjects. It appears that most aspects of the pharmacokinetic behavior of caffeine are very similar in young and elderly men.

Liver-directed gene transfer in non-human primates

To develop a primate model for liver-directed gene therapy, we studied several gene transfer vehicles and routes in eight rhesus monkeys (Macaca mulatta). For this purpose, we used first-generation, replication-deficient adenoviral vectors carrying the Escherichia coli lacZ gene (Ad.CMVlacZ) or a lacZ-containing plasmid (pCMV beta) with lipofectamine for transfection. The reporter gene construct was infused into either the portal vasculature, common bile duct, or saphenous vein. Adenovirus-mediated gene transfer via the portal vein resulted in expression of lacZ in over 70% of hepatocytes by days 3-7, but was accompanied by acute hepatitis. Adenovirus-mediated gene transfer via the common bile duct resulted in lacZ expression in less than 10% of hepatocytes and was accompanied by portal inflammation. The animals mounted a significant immune response, as demonstrated by adenoviral antigen-induced T-cell proliferation and production of neutralizing anti-adenovirus antibodies and antibodies to E. coli beta-galactosidase (beta-Gal). Activation of the immune response was associated with rapid decrease of the reporter gene by days 13-21. Lipofectamine-mediated gene transfer was inefficient, and no lacZ expression in the liver was detected. To limit the host immune response, 4 animals were immunosuppressed by cyclophosphamide/prednisone and then infused with the Ad.CMVlacZ via the portal vein or the saphenous vein. The monkeys showed sustained expression of lacZ for up to 35 days with no evidence of inflammation. The primates transduced via the saphenous vein showed a level of beta-Gal expression in the liver similar to that of the portal vein-infused animals. In conclusion, adenovirus-mediated gene transfer to non-human primate livers via the portal vein or saphenous vein is efficient, but it results in transient expression and is accompanied by an immune response to both vector and transgene products and acute hepatitis, whereas lipofectamine-mediated transfer is inefficient. Manipulation of the host immune response may expand potential applications of adenoviral vectors for liver-directed gene transfer.

Organization of the hamster intergeniculate leaflet: NPY and ENK projections to the suprachiasmatic nucleus, intergeniculate leaflet and posterior limitans nucleus

The intergeniculate leaflet (IGL) is an integral part of the circadian visual system. It receives direct retinal input and relays photic information to the circadian clock in the suprachiasmatic nucleus (SCN) through a geniculohypothalamic tract (GHT). In both rat and hamster, neuropeptide Y immunoreactive (NPY-IR) IGL cells project through the GHT to the SCN. However, the hamster GHT also contains enkephalin-IR (ENK-IR) fibers, presumably of IGL origin. In the present investigations, the IGL was examined for NPY-, ENK-, or dual-IR cells. Their projections to the SCN, contralateral IGL and pretectum were also studied. The results show that the hamster IGL contains both NPY- and ENK-IR neurons and that about 50% of these are immunoreactive to both peptides. Double-label retrograde analysis indicates that cells of each peptide class project to the SCN. Similarly, IGL neurons, many of which are NPY- and ENK-IR, project to the pretectum, particularly the posterior limitans nucleus. While numerous IGL neurons project contralaterally, very few are NPY- or ENK-IR. The distribution of SCN- and pretectum-projecting cells, in conjunction with the distribution of peptide-IR neurons, allows expansion of the IGL definition to include the region medial to the ventral lateral geniculate nucleus (VLG). The VLG is ventrolateral to the IGL and does not contain either neurons projecting to the SCN nor NPY- or ENK-IR cells, but does have numerous neurons projecting to the pretectum. The results substantiate and expand the previous definition of the hamster IGL, elaborate the species difference in IGL organization, and demonstrate the increased breadth of the circadian visual system.

Multicenter double-blind study of ticlopidine in the treatment of intermittent claudication and the prevention of its complications

In this multicenter trial 169 patients with chronic intermittent claudication due to obstructive peripheral vascular disease were randomized in a double-blind fashion into two parallel groups receiving either 250 mg ticlopidine or placebo, twice daily. At entry, the two groups (83 ticlopidine, 86 placebo) were well matched for the major clinical features apart from an excess of women in the ticlopidine group. At six months, 167 patients were alive, 2 having died of malignant disease (1 from each group). At this stage, 39 patients from the ticlopidine group and 29 from the placebo group (p = 0.04) had increased their walking distance by more than 50% of baseline values. For the groups as a whole pain-free and total walking distance were greater in the ticlopidine group than in the placebo group (194 vs 124 meters, p = 0.03 and 236 vs 170 meters, p = 0.04, respectively). Two patients from the ticlopidine group vs 9 patients from the placebo group (p = 0.03) developed significant cardiovascular events during the study. These results indicate that ticlopidine has a beneficial effect both in the treatment of the symptoms and the prevention of vascular complications in patients with intermittent claudication.

Intravenous regional sympatholysis: a double-blind comparison of guanethidine, reserpine, and normal saline

This double-blind, randomized study was designed to compare the effectiveness of intravenous regional sympatholysis using guanethidine, reserpine and normal saline. Twenty-one patients with reflex sympathetic dystrophy of an upper or lower extremity were enrolled and received intravenous regional blockade (IVRB) with one of the three medications. There was significant pain relief in all three groups at 30 min. There were no significant differences among the three groups in the degree of pain relief, the number of patients obtaining pain relief in the 30 min after the block, or the number of patients reporting more than 50% pain relief for more than 24 hr. The saline group's high rate of pain relief could be partially due to a mechanism of tourniquet-induced analgesia.

Potential role of nitric oxide in a model of chronic colitis in rhesus macaques

BACKGROUND/AIMS

Excess nitric oxide formation, via the inducible NO synthase isoform, has been implicated in the pathogenesis of experimental and clinical inflammatory bowel disease. The aim of this study was to assess the site, enzyme source, and magnitude of NO production in juvenile rhesus macaques with idiopathic colitis.

METHODS

NO production was assessed systemically from plasma and urine levels of reactive nitrogen intermediates and locally by the formation of [3H]citrulline from [3H]arginine and reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry. Inducible NO synthase gene expression was assessed by reverse-transcription polymerase chain reaction.

RESULTS

Plasma and urine levels of reactive nitrogen intermediates were greater in colitic animals than in control monkeys by 13- and 5-fold, respectively. NADPH diaphorase activity in normal animals was confined to the myenteric plexus. In colitis, staining was also apparent in crypt abscesses and superficial epithelial and mucosal bands. Gene expression for inducible NO synthase was only found in colitic specimens. Colonic [3H]citrulline formation was markedly elevated in colitic specimens, and the inducible isoform accounted for 58% of total activity.

CONCLUSIONS

It is proposed that excess NO, formed via the inducible form of NO synthase, contributes to the mucosal inflammation and symptoms of this idiopathic colitis model.

Brachial plexus block with a new local anaesthetic: 0.5 per cent ropivacaine

A new local anaesthetic, ropivacaine hydrochloride, was used in a concentration of 0.5 per cent in 32 patients receiving a subclavian perivascular block for upper extremity surgery. One group (n = 15) received 0.5 per cent ropivacaine without epinephrine and a second group (n = 17) received 0.5 per cent ropivacaine with epinephrine in a concentration of 1:200,000. Anaesthesia was achieved in 87 per cent of the patients in both groups in all of the C5 through T1 brachial plexus dermatomes. Motor block was profound with 100 per cent of patients in both groups developing paresis at both the shoulder and hand and 100 per cent developing paralysis at the shoulder. There was a rapid initial onset of sensory block (a mean of less than four minutes for analgesia) with a prolonged duration (a mean of greater than 13 hr of analgesia). The addition of epinephrine did not significantly affect the quality or onset of sensory or motor block. The duration of sensory block was reduced by epinephrine at T1 for analgesia and at C7, C8, and T1 for anaesthesia. The duration of sensory block in the remaining brachial plexus dermatomes as well as the duration of motor block was not effected by epinephrine. There was no evidence of cardiovascular or central nervous system toxicity in either group with a mean dose of 2.5-2.6 mg.kg-1 ropivacaine.

Plasma concentrations of ropivacaine given with or without epinephrine for brachial plexus block

The purpose of this study was to determine the pharmacokinetic properties of the local anaesthetic ropivacaine used with or without epinephrine for brachial plexus block. Seventeen ASA physical status I or II adult patients undergoing elective orthopaedic surgery received a single injection of 33 ml ropivacaine for subclavian perivascular block and 5 ml to block the intercostobrachial nerve in the axilla. One group (n = 8) received 0.5 per cent ropivacaine without epinephrine (190 mg) and the other (n = 9) received 0.5 per cent ropivacaine with epinephrine 1:200,000 (190 mg). Plasma ropivacaine concentrations were measured from peripheral venous blood samples taken for 12 hr after drug administration. Ropivacaine base was determined in plasma using gas chromatography and a nitrogen-sensitive detector. The mean peak plasma concentration (Cmax) was 1.6 +/- 0.6 mg.L-1 and 1.3 +/- 0.4 mg.L-1 after administration of ropivacaine with and without epinephrine. The median time to peak plasma concentration (tmax) was 0.75 hr and 0.88 hr and the mean area under the plasma concentration curve AUC0-12h was 7.7 +/- 3.6 and 7.0 +/- 3.4 mg.l hr-1. The differences were not statistically significant. The terminal phase of the individual plasma concentration-time curves showed a varying and sometimes slow decline possibly indicating a sustained systemic uptake of ropivacaine from the brachial plexus. No central nervous system or cardiovascular symptoms attributed to systemic plasma concentrations of the drug were observed, with the dose (1.90-3.28 mg.kg-1) of ropivacaine used. It is concluded that the addition of epinephrine does not alter the pharmacokinetic properties of ropivacaine when used for subclavian perivascular brachial plexus block.