Arterial Plasma Concentrations Research Articles

SAFETY AND EFFICACY OF INTRAOSSEOUS ROPIVACAINE IN LOWER EXTREMITY (SORE) STUDY

IntroductionDay stay surgery for anterior cruciate ligament (ACL) reconstructions is an increasingly common practice and has driven clinicians to come up with postoperative pain regimes that allow same day mobilisation and a safe and timely discharge. There is a paucity of literature surrounding the use of intraosseous (IO) ropivacaine used as a Bier's block to provide both intraoperative and postoperative analgesia in lower limb surgery.MethodsThis patient blinded, pilot study randomised 15 patients undergoing ACL reconstruction to receive either IO ropivacaine 1.5 or 2.0 mg/kg; or 300 mg of ropivacaine as local infiltration (standard of care). Toxic plasma levels of ropivacaine have been defined in the literature and therefore the primary outcome for this study was arterial plasma concentration of ropivacaine as a means to determine its safety profile. Samples were taken via an arterial line at prespecified times after tourniquet deflation. Secondary outcomes that we were interested in included immediate postoperative pain scores using the visual analogue scale (VAS) and perioperative opioid equivalent consumption.ResultsParticipants had a mean age of 27.8 (SD 9.2) years and 87% (13/15) were male. All patients in the intervention group receiving IO ropivacaine had plasma concentrations well below the threshold for central nervous system (CNS) toxicity (0.60 µg/ml). The highest plasma concentration was achieved in the intervention group receiving 1.5 mg/kg dose of ropivacaine reaching 3.59 mg/ml. This would equate to 0.22 µg/ml of free plasma ropivacaine. There were no differences across the three groups regarding pain scores or perioperative opioid consumption.ConclusionsThis study demonstrates that IO administration of 0.2% ropivacaine is both safe and effective in reducing perioperative pain in patients undergoing ACL reconstruction. There may be scope to increase the IO dose further or utilise other analgesics via the IO regional route to improve perioperative pain relief.

PET Evaluation of the Novel F-18 Labeled Reversible Radioligand [18F]GEH200449 for Detection of Monoamine Oxidase-B in the Non-Human Primate Brain.

Positron emission tomography (PET) using radioligands for the enzyme monoamine oxidase B (MAO-B) is increasingly applied as a marker for astrogliosis in neurodegenerative disorders. In the present study, a novel reversible fluorine-18 labeled MAO-B compound, [18F]GEH200449, was evaluated as a PET radioligand in non-human primates. PET studies of [18F]GEH200449 at baseline showed brain exposure (maximum concentration: 3.4-5.2 SUV; n = 5) within the range of that for suitable central nervous system radioligands and a regional distribution consistent with the known localization of MAO-B. Based on the quantitative assessment of [18F]GEH200449 data using the metabolite-corrected arterial plasma concentration as input function, the Logan graphical analysis was selected as the preferred method of quantification. The binding of [18F]GEH200449, as calculated based on regional estimates of the total distribution volume, was markedly inhibited (occupancy >80%) by the administration of the selective MAO-B ligands L-deprenyl (0.5 and 1.0 mg/kg) or rasagiline (0.75 mg/kg) prior to radioligand injection. Radioligand binding was displaceable by the administration of L-deprenyl (0.5 mg/kg) at 25 min after radioligand injection, thus supporting reversible binding to MAO-B. These observations support that [18F]GEH200449 is a reversible MAO-B radioligand suitable for applied studies in humans.

EFFECT OF RENAL DENERVATION ON THE PLASMA ADIPONECTIN CONCENTRATION IN PATIENTS WITH RESISTANT HYPERTENSION

Objective: Adiponectin is produced by white adipose tissue and has anti-diabetic, anti-atherosclerotic, anti-thrombotic, anti-inflammatory, and cardioprotective properties. In patients with arterial hypertension plasma concentration of adiponectin is lower than in healthy subjects. Renal denervation (RDN) i.e. percutaneous ablation of fibers from the sympathetic nervous system located in the wall of the renal arteries by radio frequency waves, is a method of resistant arterial hypertension treatment. The aim of this single center, interventional, clinical study was to assess the effect of RDN on the plasma adiponectin concentration in patients with resistant arterial hypertension. Design and method: Twenty-six patients (12 women, 14 men) aged 54.0±7.8 years with resistant hypertension who underwent RDN using Simplicity catheters (Medtronic, Inc., Northridge, CA) were enrolled in the study. Plasma adiponectin concentration was determined using the Human Adiponectin ELISA Kit (Otsuka Pharmaceutical Co, Tokyo, Japan) before the RDN and 6 and 12 months after this procedure. Results: Blood pressure (BP) values before RDN and 6 and 12 months after RDN were as follow: systolic BP - 190.4±24.5, 160.8±14.5, 155.7±17.9 mmHg (p<0.001) and diastolic BP - 111.7±18.9, 88.9±8.3, 91.2±10.2 mmHg (p<0.001), respectively. Body mass index (BMI) before RDN, 6 and 12 months after RDN were 31.5±4.2, 30.5 ±4.4, 30.2±4.0 kg/m2, (p = 0.057), respectively. Plasma adiponectin concentration before the RDN and 6 and 12 months after RDN were 6.93±4.85, 7.94±3.97, 8.83±6.12 [μg/ml] (p = 0.007), respectively. In the follow up i.e. 6 and 12 months after RDN plasma adiponectin concentration increases significantly in responders (systolic BP decrease higher or equal 25 mmHg) (7.93±6.14, 8.87±4.68, 10.57±7.51 [μg/mL]; respectively]; p = 0.03, and did not change significantly in low-responders to RDN (systolic BP decrease < 25 mmHg) (5.76±2.45, 6.86±2.76, 6.81±3.19 [μg/mL]; respectively; p = 0.2). Conclusions: 1. Plasma adiponectin concentration increases significantly after successful RDN in patients with resistant arterial hypertension. 2. Higher plasma adiponectin concentration may participate - beyond blood pressure reduction - in the cardiovascular benefits related to successful RDN, however clinical consequences of our results need further investigations.

Safety and efficacy of intraosseous ropivacaine in lower extremity (SORE) study.

Day stay surgery for anterior cruciate ligament (ACL) reconstructions is an increasingly common practice and has driven clinicians to develop postoperative pain regimes that allow same day mobilization and a safe and timely discharge. There is a paucity of literature surrounding the use of intraosseous (IO) ropivacaine used as a Bier's block to provide both intraoperative and postoperative analgesia in lower limb surgery. This patient blinded, pilot study randomized 15 patients undergoing ACL reconstruction to receive either IO ropivacaine 1.5 or 2.0mg/kg; or 300 mg of ropivacaine as local infiltration. The primary outcome for this study was arterial plasma concentration of ropivacaine. Samples were taken via an arterial line at prespecified times after tourniquet deflation. Secondary outcomes included immediate postoperative pain scores using the visual analogue scale and perioperative opioid equivalent consumption. All patients in the intervention group receiving IO ropivacaine had plasma concentrations well below the threshold for central nervous system (CNS) toxicity (0.60 μg/mL). The highest plasma concentration was achieved in the intervention group receiving 1.5mg/kg dose of ropivacaine reaching 2.93 mg/mL. This would equate to 0.18 μg/mL of free plasma ropivacaine. There were no differences across the three groups regarding pain scores or perioperative opioid consumption. This study demonstrates that IO ropivacaine is both safe and effective in reducing perioperative pain in patients undergoing ACL reconstruction. There may be scope to increase the IO dose further or utilize other analgesics via the IO regional route to improve perioperative pain relief.

Insulin Infusion Is Linked to Increased NPPC Expression in Muscle and Plasma C-type Natriuretic Peptide in Male Dogs.

The purpose of this study was to assess insulin-stimulated gene expression in canine skeletal muscle with a particular focus on NPPC, the gene that encodes C-type natriuretic peptide, a key hormonal regulator of cardiometabolic function. Four conscious canines underwent hyperinsulinemic, euglycemic clamp studies. Skeletal muscle biopsy and arterial plasma samples were collected under basal and insulin-stimulated conditions. Bulk RNA sequencing of muscle tissue was performed to identify differentially expressed genes between these 2 steady-state conditions. Our results showed that NPPC was the most highly expressed gene in skeletal muscle in response to insulin infusion, rising 4-fold between basal and insulin-stimulated conditions. In support of our RNA sequencing data, we found that raising the plasma insulin concentration 15-fold above basal elicited a 2-fold (P = 0.0001) increase in arterial plasma concentrations of N-terminal prohormone C-type natriuretic peptide. Our data suggest that insulin may play a role in stimulating secretion of C-type natriuretic peptide by skeletal muscle. In this context, C-type natriuretic peptide may act in a paracrine manner to facilitate muscle–vascular bed crosstalk and potentiate insulin-mediated vasodilation. This could serve to enhance insulin and glucose delivery, particularly in the postprandial absorptive state.

Volutrauma Increases Exhaled Pentanal in Rats: A Potential Breath Biomarker for Ventilator-Induced Lung Injury.

Mechanical ventilation injures lungs, but there are currently no reliable methods for detecting early injury. We therefore evaluated whether exhaled pentanal, a lipid peroxidation product, might be a useful breath biomarker for stretch-induced lung injury in rats. A total of 150 male Sprague-Dawley rats were investigated in 2 substudies. The first randomly assigned 75 rats to 7 hours of mechanical ventilation at tidal volumes of 6, 8, 12, 16, and 20 mL·kg-1. The second included 75 rats. A reference group was ventilated at a tidal volume of 6 mL·kg-1 for 10 hours 4 interventional groups were ventilated at a tidal volume of 6 mL·kg-1 for 1 hour, and then for 0.5, 1, 2, or 3 hours at a tidal volume of 16 mL.kg-1 before returning to a tidal volume of 6 mL·kg-1 for additional 6 hours. Exhaled pentanal was monitored by multicapillary column-ion mobility spectrometry. The first substudy included cytokine and leukocyte measurements in blood and bronchoalveolar fluid, histological assessment of the proportion of alveolar space, and measurements of myeloperoxidase activity in lung tissue. The second substudy included measurements of pentanal in arterial blood plasma, cytokine and leukocyte concentrations in bronchoalveolar fluid, and cleaved caspase 3 in lung tissue. Exhaled pentanal concentrations increased by only 0.5 ppb·h-1 (95% confidence interval [CI], 0.3-0.6) when rats were ventilated at 6 mL·kg-1. In contrast, exhaled pentanal concentrations increased substantially and roughly linearly at higher tidal volumes, up to 3.1 ppb·h-1 (95% CI, 2.3-3.8) at tidal volumes of 20 mL·kg-1. Exhaled pentanal increased at average rates between 1.0 ppb·h-1 (95% CI, 0.3-1.7) and 2.5 ppb·h-1 (95% CI, 1.4-3.6) after the onset of 16 mL·kg-1 tidal volumes and decreased rapidly by a median of 2 ppb (interquartile range [IQR], 0.9-3.2), corresponding to a 38% (IQR, 31-43) reduction when tidal volume returned to 6 mL·kg-1. Tidal volume, inspiratory pressure, and mechanical power were positively associated with pentanal exhalation. Exhaled and plasma pentanal were uncorrelated. Alveolar space decreased and inflammatory markers in bronchoalveolar lavage fluid increased in animals ventilated at high tidal volumes. Short, intermittent ventilation at high tidal volumes for up to 3 hours increased neither inflammatory markers in bronchoalveolar fluid nor the proportion of cleaved caspase 3 in lung tissue. Exhaled pentanal is a potential biomarker for early detection of ventilator-induced lung injury in rats.

Effect of nutritional status on nutrient and gas utilization by the mammary gland of lactating sows

Milk synthesis being a continuous process in lactating sows, the mammary gland has to adapt its metabolism in response to extreme short-term changes in nutrient availability in the arterial bloodstream, due to the feeding pattern. The objective of the present study was to better quantify and understand these adaptations. The effect of morning refeeding after an overnight 16-h feed withdrawal was measured on the uptake of energy-supplying nutrients, amino acids (AA), and some vitamins and minerals. After farrowing, catheters were fitted in the right anterior mammary vein and in the carotid artery of six sows. Blood samples were drawn on days 7, 14, and 21 of lactation, every 30 from 60 min before the morning meal to 300 min after the morning meal. Plasma concentrations of glucose, lactate, triglycerides (TG), non-esterified fatty acids (NEFA), glycerol, α-amino nitrogen (N), vitamins B12, and folates were determined on all samples. Riboflavin and AA concentrations were only measured 30 min before the meal and 120 min after the meal. Arterial and venous plasma concentrations of glucose, lactate, and α-amino N increased after the meal (P < 0.01), and concentrations of NEFA, glycerol, and TG decreased (P < 0.01). Mammary arteriovenous concentration difference increased after the meal for glucose, lactate, and α-amino N (P < 0.01), remained constant for TG, and decreased for NEFA (P < 0.01) and glycerol (P < 0.05). Arterial concentrations of all AA increased after the meal, but changes of arteriovenous difference with the meal differed among AA. Arteriovenous difference of energy (7.6 kJ/l plasma) concentration was similar in feed-deprived and fed sows, but the contribution of the various nutrients differed, and the respiratory quotient was lower (P < 0.01) before the meal (0.95) than after the meal (1.54). The relative contributions of glucose, lactate, TG, NEFA, and AA to arteriovenous difference in energy concentration were 50.2, 3.8, 25.1, 0, and 20.8% in fed and 24.6, 2.2, 24.9, 32.9, and 15.0% in feed-deprived sows, respectively. The daily mammary extraction of vitamin B12, estimated from arteriovenous differences was higher than the amount of this vitamin bioavailable from the diet, probably contributing to the 50% decrease in plasma concentration between day 7 and day 21 of lactation. For both riboflavin and folates, arteriovenous differences in plasma concentrations were small or not different from zero. These results indicate that the mammary gland has a great capacity to adapt nutrient uptake very rapidly and modify its metabolism according to the nutrients available in the bloodstream.

Prospective clinical validation of the Eleveld propofol pharmacokinetic-pharmacodynamic model in general anaesthesia

BackgroundTarget-controlled infusion (TCI) systems incorporating pharmacokinetic (PK) or PK-pharmacodynamic (PK-PD) models can be used to facilitate drug administration. Existing models were developed using data from select populations, the use of which is, strictly speaking, limited to these populations. Recently a propofol PK-PD model was developed for a broad population range. The aim of the study was to prospectively validate this model in children, adults, older subjects, and obese adults undergoing general anaesthesia. MethodsThe 25 subjects included in each of four groups were stratified by age and weight. Subjects received propofol through TCI with the Eleveld model, titrated to a bispectral index (BIS) of 40–60. Arterial blood samples were collected at 5, 10, 20, 30, 40, and 60 min after the start of propofol infusion, and every 30 min thereafter, to a maximum of 10 samples. BIS was recorded continuously. Predictive performance was assessed using the Varvel criteria. ResultsFor PK, the Eleveld model showed a bias < ±20% in children, adults, and obese adults, but a greater bias (−27%) in older subjects. Precision was <30% in all groups. For PD, the bias and wobble were <5 BIS units and the precision was close to 10 BIS units in all groups. Anaesthetists were able to achieve intraoperative BIS values of 40–60 using effect-site target concentrations about 85–140% of the age-adjusted Ce50. ConclusionsThe Eleveld propofol PK-PD model showed predictive precision <30% for arterial plasma concentrations and BIS predictions with a low (population) bias when used in TCI in clinical anaesthesia practice.

Uptake of dietary amino acids into arterial blood during continuous enteral feeding in critically ill patients and healthy subjects

Amino acid availability is a regulatory factor of protein anabolism and is partly dependent on enteral amino acid uptake. During continuous enteral feeding, enteral amino acid uptake may vary considerably, but this has not been documented systematically. In this pragmatic study, we investigated patients in the intensive care unit (n=10) and healthy adults (n=10). The time course of essential amino acid concentrations in arterial plasma and the uptake of dietary phenylalanine were recorded during 12hours of continuous enteral feeding, using a 13C-labeled phenylalanine tracer. Plasma essential amino acid concentrations and 13C-phenylalanine enrichment reached a tentative steady state after no more than 4.5h from start of tracer infusion. There was a large intra- and inter-individual variability in both cohorts. No periodicity could be detected in the temporal variation. During continuous enteral feeding, uptake of amino acids shows large intra- and inter-individual variation. A tentative steady state of 13C-phenylalanine uptake is eventually reached. Registered at Australian New Zealand Clinical Trials Registry, trial ID ACTRN12616000593437.

Compromised Glutamine - Glutamate Metabolism in a Pseudomonas Aeruginosa Induced Hyperdynamic Sepsis-Recovery Pig Model During an Anabolic Nutritional Intervention

Abstract Objectives Optimal feeding in patients recovering from sepsis is critical to preserve muscle mass. In sepsis, glutamine (Gln) is considered a conditional essential amino acid and low plasma level of its precursor glutamate (Glu), is associated with higher mortality. An essential amino acid (EAA) mixture restores protein anabolism in the early recovery phase of acute septicemia in the pig. However, it is unclear whether interorgan Glu-Gln kinetics is also improved. Therefore, we measured the interorgan kinetics of Glu-Gln during a nutritional intervention with a balanced free amino acid (TAA) or EAA mixture in the early recovery phase of acute septicemia in the pig. Methods In catheterized pigs (±25 kg), acute septicemia was present for 6 hours (Pseudomonas aeruginosa: 3e,8 CFU/ml/h IV). At t = 6 h, recovery was started by a single dose gentamycin (5 mg/kg) and intra-gastric continuous feeding of a balanced free TAA or EAA mixture (pig muscle profile, 31 mg N/kg bw/h, 30% daily intake and dextrose 781 mg/kg bw/h) for 6 hours. We studied 3 groups (Healthy: H-TAA n = 12; Sepsis: S-TAA n = 13, S-EAA n = 12) over the last 3 hours of the intervention by measuring arterial and venous plasma concentrations (expressed as mean[low, high 95%CI]) and organ net balances of the portal drained viscera (PDV), liver, kidneys and hindquarter (HQ, muscle). Statistics: Net balances were tested with Wilcoxon Signed Rank Test. Group comparisons with ANOVA. Significance: P &amp;lt; 0.05. Results Plasma concentrations : Gln was increased only in S-EAA (23 [14,32]%) group. In contrast, Glu substantially decreased in S-TAA and S-EAA (32[25,40]; 35[28,43]%) groups. Net PDV balance:Increased Gln uptake in S-EAA (P = 0.0020), but zero balance of Glu. Net HQ balance: Gln release was higher in S-TAA and S-EAA(P = 0.0028;0.0143). However, no changes in Glu uptake. Net liver balance: Gln uptake was higher in S-TAA and S-EAA (P = 0.0155;0.0056). Reduced Glu release in S-TAA (P = 0.0250). Net kidney balance: Zero balance for Gln, Glu uptake decreased in S-TAA (P = 0.0403). Conclusions In the present model of an early recovery of septicemia, interorgan Glu-Gln metabolism and Glu plasma levels are not restored by anabolic intervention, suggesting additional supplementation needs. Funding Sources NIH R01GM084447 and S10RR027047.

Differences and Effects of Metabolic Fate of Individual Amino Acid Loss in High-Efficiency Hemodialysis and Hemodiafiltration

The objective of the study was to quantify the loss and arterial blood concentration of the three main classes of amino acids (AAs)-nonessential amino acids (NEAAs), essential amino acids (EAAs), and branched-chain amino acids-as resulting from high-efficiency hemodialysis (HED) and hemodiafiltration (HDF). We moreover aimed to identify the different fates and metabolic effects manifested in patients undergoing hemodialysis and the consequences on body composition and influence of nutritional decline into protein energy wasting. Identical dialysis monitors, membranes, and dialysate/infusate were used to ensure consistency. Ten patients were recruited and randomized to receive treatment with on-line modern HED and HDF. Arterial plasma concentrations of individual AAs were compared in healthy volunteers and patients undergoing hemodialysis, and AA levels outflowing from the dialyzer were evaluated. Baseline AA plasma levels of patients undergoing hemodialysis were compared with findings obtained 1year later. A severe loss of AA with HED/HDF was confirmed: a marked loss of total AAs (5g/session) was detected, corresponding to more than 65% of all AAs. With regard to individual AAs, glutamine displayed a consistent increase (+150%), whereas all other AAs decreased after 12months of HD/HDF. Only a few AAs, such as proline, cysteine, and histidine maintained normal levels. The most severe metabolic consequences may result from losses of EAAs such as valine, leucine, and histidine and from NEAAs including proline, cysteine, and glutamic acid eliciting the onset of hypercatabolism threatening muscle mass loss. Dialysis losses, together with the effect of chronic uremia, resulted in a reduction of fundamental EAAs and NEAAs, which progressively led our patients after 12months to a deterioration of lean mass toward sarcopenia. Therefore, the reintroduction of a correctly balanced AA supplementation in patients undergoing HD to prevent or halt decline of hypercatabolism into cachexia is recommended.

Carotid body‐specific shRNA knockdown of PKCɛ blunts TRPV1‐dependent asthmatic bronchoconstriction

RationaleAggravated airway bronchoconstriction and mucus production in response to allergen and/or bradykinin (i.e., airway hyperresponsiveness) is a primary defining symptom of asthma. Recently, we discovered a critical role for the carotid bodies: inhaled allergen causes an increase in arterial plasma concentrations of asthmakines which excite the carotid bodies via a transient receptor potential vanilloid 1 channel (TRPV1) dependent mechanism. Elevated carotid body excitation in turn increases efferent vagal activity, resulting in heightened bronchoconstriction. While our data demonstrate that the carotid bodies are strongly excited by multiple Th‐2 cytokines, in the ovalbumin primed and sensitized Brown Norway rat model of asthma, the primary asthmakine is likely lysophosphatidic acid (LPA). However, the cellular link between LPA receptors and TRPV1 has not been identified. Here we show that the effect of LPA on the carotid bodies is likely mediated by PKCɛ‐dependent phosphorylation of TRPV1.MethodsLentivirus vectors containing shRNA to knockdown PKCɛ or scrambled sequence were injected bilaterally into the carotid bodies of asthmatic rats (n=7, each). The responses of carotid bodies to LPA (5μM), and their subsequent responses to TRPV1 blockade (AMG9810, 10μM) were tested using the en bloc perfused carotid body preparation. The effects of carotid body‐specific PKCɛ knockdown on changes in lung mechanics in response to inhaled bradykinin were tested using the Flexivent system.ResultsCarotid bodies from asthmatic rats injected with PKCɛ knockdown sequence mounted smaller responses to LPA than those injected with scrambled sequence. No difference in LPA response was detected between groups following TRPV1 blockade, suggesting the primary target for PKCɛ is TRPV1. Asthmatic rats with carotid bodies injected with PKCɛ knockdown sequence had reduced lung resistance in response to bradykinin at 1, 10 and 20 minutes. Similar results were obtained using a PKCɛ inhibitory peptide.ConclusionWe show for the first time that carotid body‐mediated bronchoconstriction in asthmatic rats occurs through LPA receptor activation of PKCɛ and subsequent TRPV1‐mediated carotid sinus nerve excitation. Targeting carotid body LPA receptors, PKCɛ and/or TRPV1 may provide a new therapeutic target to reduce asthmatic airway hyperresponsiveness.Support or Funding InformationCIHR, Alberta Innovates, Alberta Lung Association and the Parker B. Francis Foundation.

Net Absorption and Metabolism of β-Hydroxy- β-Methyl Butyrate during Late Gestation in a Pig Model.

The leucine metabolite, β-hydroxy-β-methyl butyrate (HMB), is widely used in human nutrition and animal production as a nutritional supplement. Although the HMB usage during late gestation has been demonstrated to have a positive effect on fetal development, knowledge on net absorption and metabolism of HMB and impact of HMB on branched chain amino acids (BCAAs) metabolism is lacking. To address this, we conducted a study using pigs during the perinatal period as a model organism. Eight-second parity sows were fitted with indwelling catheters in the femoral artery and in the portal, hepatic, femoral, and mesenteric veins. Eight hourly sets of blood samples were taken starting 30 min before the morning meal on day –10 and day –3 relative to parturition. Four control (CON) sows were fed a standard lactation diet from day –15 and throughout the experiment, and 4 HMB sows were fed the control diet supplemented with 15 mg Ca(HMB)2/kg body weight mixed in one third of the morning meal from day –10 until parturition. Blood gases, plasma metabolites, milk compositions, and apparent total tract digestibility of nutrients were measured. Arterial plasma concentrations of HMB (p < 0.001), Cys (p < 0.001), and Lys (p < 0.10) were increased in HMB supplemented sows, while arterial plasma triglycerides concentration was decreased (p < 0.05). The net portal recovery of Ala and Asp were increased in HMB sows (p < 0.05). Sows fed HMB had increased hepatic vein flow and net hepatic fluxes of Met, Asn, and Gln (p < 0.05). In contrast, the femoral extraction rates of Ala and Ser were decreased by dietary HMB supplementation (p < 0.05). Dietary HMB treatment and sampling time relative to feeding had an interaction on arterial concentrations, net portal fluxes, and femoral extraction rates of BCAAs. The net portal recovery of HMB was 88%, while 14% of supplemented HMB was excreted through urine and 4% through feces. Moreover, the gastrointestinal tract metabolized 8% while the liver metabolized 12%. Finally, 26% of the daily intake of HMB was secreted via colostrum at the day of farrowing. This study demonstrated that dietary HMB supplementation increased net uptake of amino acids and increased fatty acid oxidation through improving blood flow and insulin sensitivity during the late gestation. Most importantly, oral HMB administration could maintain a stable postprandial absorption and altered metabolism in BCAAs. Net portal flux of HMB at 5.5 to 6.5 h after feeding approached zero, indicating that HMB ideally should be administrated two or three times, daily.

Relationship between acute hypercarbia and hyperkalaemia during surgery.

BACKGROUNDThe relationship between hyperkalaemia and metabolic acidosis is well described in the critical care setting; however, the relationship between acute respiratory acidosis and plasma potassium concentration is less well understood. In a controlled model of increasing levels of hypercarbia, we tested the hypothesis of whether increasing levels of hypercarbia are associated with changes in plasma potassium concentrations.AIMTo determine whether increasing levels of hypercarbia are associated with changes in plasma potassium concentrations.METHODSWe performed a post-hoc study examining changes in serum potassium in 24 patients who received increased levels of hypercarbia during cardiac surgery. Arterial blood gases and plasma concentrations of potassium were measured at baseline, 3 min prior to, and then every 3 min for 15 min during the intervention of hypercarbia. The primary endpoint was the absolute change in serum K+ at 15 min compared to the baseline K+ value. The following secondary endpoints were evaluated: (1) The association between CO2 and serum K+ concentration; and (2) The correlation between plasma pH and serum K+ concentrations.RESULTSDuring the intervention, PaCO2 increased from 43.6 mmHg (95%CI: 40.1 to 47.1) at pre-intervention to 83.9 mmHg (95%CI: 78.0 to 89.8) at 15 min after intervention; P < 0.0001. The mean (SD) serum potassium increased from 4.16 (0.35) mmol/L at baseline to 4.28 (0.33) mmol/L at 15 min (effect size 0.09 mol/L; P = 0.22). There was no significant correlation between PaCO2 and potassium (Pearson’s coefficient 0.06; 95%CI: -0.09 to 0.21) or between pH and potassium (Pearson’s coefficient -0.07; 95%CI: -0.22 to 0.09).CONCLUSIONAcute hypercarbia and subsequent respiratory acidaemia were not associated with hyperkalaemia in patients undergoing major surgery.

Mammary gland metabolite utilization in response to exogenous glucose or long-chain fatty acids at low and high metabolizable protein levels

We investigated mammary gland metabolism in lactating dairy cattle in response to energy from glucogenic (glucose; GG) or lipogenic (palm olein; LG) substrates at low (LMP) and high (HMP) metabolizable protein levels. According to a 6 × 6 Latin square design, 6 rumen-fistulated second-lactation Holstein-Friesian dairy cows (97 ± 13 d in milk) were abomasally infused with saline (LMP-C); isoenergetic infusions (digestible energy basis) of 1,319 g/d glucose (LMP-GG), 676 g/d palm olein (LMP-LG), or 844 g/d essential AA (EAA; HMP-C); or isoenergetic infusions of 1,319 g/d glucose + 844 g/d EAA (HMP-GG) or 676 g/d palm olein + 844 g/d EAA (HMP-LG). Each experimental period consisted of 5 d of continuous infusion followed by 2 d of rest. A total mixed ration (42% corn silage, 31% grass silage, and 27% concentrate on a dry matter basis) formulated to meet 100 and 83% of net energy and metabolizable protein requirements, respectively, was fed at 90% of ad libitum intake by individual cow. Arterial and venous blood samples were collected on d 5 of each period. Infusing GG or LG at the HMP level did not affect milk yield or composition differently than at the LMP level. Neither GG nor LG infusion stimulated milk protein or lactose yield, but fat yield tended to decrease with GG and tended to increase with LG. Infusion of GG increased arterial plasma concentrations of glucose and insulin and decreased concentrations of β-hydroxybutyrate (BHB), nonesterified fatty acids, long-chain fatty acids (LCFA), total AA, EAA, and group 2 AA. Infusion of LG increased arterial triacylglycerides (TAG) and LCFA but did not affect EAA concentrations. Compared with the LMP level, the HMP level increased arterial concentrations of BHB, urea, and all EAA groups and decreased the concentration of total non-EAA. Mammary plasma flow increased with GG and was not affected by LG or protein level. Uptake and clearance of total EAA and group 2 AA were affected or tended to be affected by GG × AA interactions, with their uptakes being lower and their clearances higher with GG, but only at the LMP level. Infusion of LG did not affect uptake or clearance of any AA group. The HMP level increased uptake and decreased clearance of all EAA groups and decreased non-EAA uptake. Infusion of GG tended to increase mammary glucose uptake, and tended to decrease BHB uptake only at the LMP level. Infusion of LG increased mammary uptake of TAG and LCFA and increased or tended to increase clearance of TAG and LCFA. We suspect GG increased mammary plasma flow to maintain intramammary energy and AA balance and stimulated lipogenesis in adipose, accounting for depressed arterial BHB and group 2 AA concentrations. Mammary glucose uptake did not cover estimated requirements for lactose and fat synthesis at the HMP level, except during HMP-GG infusion. Results of this study illustrate flexibility in mammary metabolite utilization when absorptive supply of glucogenic, lipogenic, and aminogenic substrate is increased.

Microliter-ordered automatic blood sampling system for fully quantitative analysis of small-animal PET.

The objective of the present study was to develop a fully automated blood sampling system for kinetic analysis in mice positron emission tomography (PET) studies. Quantitative PET imaging requires radioactivity concentrations in arterial plasma to estimate the behavior of an administered radiopharmaceutical in target organs. Conventional manual blood sampling has several drawbacks, such as the need for troubleshooting in regard to blood collection, necessary personnel, and the radiation exposure dose. We recently developed and verified the operability of a fully automated blood sampling system (automatic blood dispensing system-ABDS). Here, we report the results of fully quantitative measurements of the cerebral metabolic rate of glucose (CMRglc) in mice using the ABDS. Under 1% isoflurane anesthesia, a catheter was inserted into the femoral artery of nine wild-type male mice. Immediately after injection of 18F-fluorodeoxyglucose (FDG) (13.2 ± 3.93MBq in 0.1mL saline), arterial blood samples were drawn using the ABDS and then analyzed using CD-Well, a system we previously developed that can measure radioactivity concentration (Bq/μL) using a few microliters of blood in the plasma and whole blood separately. In total, 16 blood samplings were conducted in 60min as follows: 10s × 9; 70s × 2; 120s × 1; 250s × 1; 10min × 2; and 30min × 1. Dynamic PET scans were conducted concurrently using a small-animal PET/computed tomography (CT) (PET/CT) scanner. Full kinetics modeling using a two-tissue-three-compartment model was applied to calculate CMRglc. Blood volume was also estimated. No significant differences were observed between the manual and ABDS measurements. A proportional error was detected only for plasma. The mean ± standard deviation CMRglc value in the mice was 5.43 ± 1.98mg/100g/min (30.2 ± 11 μmol/min/100g), consistent with a previous report. The automated microliter-ordered blood sampling system developed in the present study appears to be useful for absolute quantification of CMRglc in mice PET studies.

Pharmacokinetic/Pharmacodynamic Model of CW002, an Investigational Intermediate Neuromuscular Blocking Agent, in Healthy Volunteers.

CW002 is an investigational nondepolarizing, neuromuscular blocking agent with a rapid onset and intermediate duration of action in animals. This is a single ascending dose, healthy subject study exploring tolerability, pharmacokinetics, and potency. Population pharmacokinetic and pharmacokinetic/pharmacodynamic models were developed using plasma drug concentration data from a previously published dose-response study in 28 healthy subjects receiving single doses of CW002 during sevoflurane anesthesia. Subjects included in the models were from five different dose cohorts (cohorts 3, 4, 5, 6, and 8 receiving 0.04, 0.06, 0.08, 0.10, and 0.14 mg/kg, respectively). Serial arterial plasma concentrations and muscle twitch heights were monitored. A four-compartment model was fit to the concentration-time data, whereas a transit compartment with a sigmoid Emax model was fit to the pharmacokinetic/pharmacodynamic data. The population pharmacokinetics of CW002 was linear with very low interindividual variability in clearance (10.8%). Simulations were conducted to predict the onset and offset of effect at 2×, 3×, and 4× ED95. The time to 80% block was predicted to be 1.5, 0.8, and 0.7 min for 2×, 3×, and 4× ED95 doses, respectively. The simulated 25 to 75% recovery index was independent of dose. CW002 has predictable pharmacokinetics and is likely to have a rapid onset with an intermediate duration of action at 3× ED95. This model provides information to inform critical decisions (e.g., dose, study design) for continued development of CW002.

Does intranasal dexmedetomidine provide adequate plasma concentrations for sedation in children: a pharmacokinetic study

BackgroundAtomised intranasal dexmedetomidine administration is an attractive option when sedation is required for paediatric diagnostic procedures, as vascular access is not required. The risk of haemodynamic instability caused by dexmedetomidine necessitates better understanding of its pharmacokinetics in young children. To date, intranasal dexmedetomidine pharmacokinetics has only been studied in adults. MethodsEighteen paediatric patients received dexmedetomidine 1 or 2 μg kg−1 intranasally or 1 μg kg−1 i.v. Plasma concentrations were determined by liquid chromatography/mass spectrometry. Non-compartmental analysis provided estimates of Cmax and Tmax. Volume of distribution, clearance, and bioavailability were estimated by simultaneous population PK analysis of data after intranasal and i.v. administration. Dexmedetomidine plasma concentration-time profiles were evaluated by simulation for intranasal and i.v. administration. ResultsAn average peak plasma concentration of 199 pg ml−1 was achieved 46 min after 1 μg kg−1 dosing and 355 pg ml−1 was achieved 47 min after 2 μg kg−1 dosing. A two-compartment pharmacokinetic model, with allometrically scaled parameters, adequately described the data. Typical bioavailability was 83.8% (95% confidence interval 69.5–98.1%). ConclusionMean arterial plasma concentrations of dexmedetomidine in infants and toddlers approached 100 pg ml−1, the low end reported for sedative efficacy, within 20 min of an atomised intranasal administration of 1 μg kg−1. Doubling the dose to 2 μg kg−1 reached this plasma concentration within 10 min and achieved almost twice the peak concentration. Peak plasma concentrations with both doses were reached within 47 min of intranasal administration, with an overall bioavailability of 84%.

An attenuated rate of leg muscle protein depletion and leg free amino acid efflux over time is seen in ICU long-stayers

BackgroundThere is extensive documentation on skeletal muscle protein depletion during the initial phase of critical illness. However, for intensive care unit (ICU) long-stayers, objective data are very limited. In this study, we examined skeletal muscle protein and amino acid turnover in patients with a prolonged ICU stay.MethodsPatients (n = 20) were studied serially every 8–12 days between days 10 and 40 of their ICU stay as long as patients stayed in the ICU. Leg muscle protein turnover was assessed by measurements of phenylalanine kinetics, for which we employed a stable isotope-labeled phenylalanine together with two-pool and three-pool models for calculations, and results were expressed per 100 ml of leg volume. In addition, leg muscle amino acid flux was studied.ResultsThe negative leg muscle protein net balance seen on days 10–20 of the ICU stay disappeared by days 30–40 (p = 0.012). This was attributable mainly to an increase in the de novo protein synthesis rate (p = 0.007). It was accompanied by an attenuated efflux of free amino acids from the leg. Leg muscle protein breakdown rates stayed unaltered (p = 0.48), as did the efflux of 3-methylhistidine. The arterial plasma concentrations of free amino acids did not change over the course of the study.ConclusionsIn critically ill patients with sustained organ failure and in need of a prolonged ICU stay, the initial high rate of skeletal muscle protein depletion was attenuated over time. The distinction between the acute phase and a more prolonged and more stable phase concerning skeletal muscle protein turnover must be considered in study protocols as well as in clinical practice.Trial registrationAustralian New Zealand Trial Registry, ACTRN12616001012460. Retrospectively registered on 1 August 2016.

The Relationship between Liver Dysfunction, Electrocardiographic Abnormalities and Metabolism in Rat

Introduction: Liver disorders may lead to many critical complications such as electrical heart abnormalities. The aim of this study was to investigate the relationship between the severity of liver dysfunctions, electrocardiogram variables and oxygen consumption. Methods: Female Sprague Dawley rats were divided into 4 groups of sham, partial portal vein ligation (PPVL), common bile duct ligation (CBDL), and combination of them (CBDL+ PPVL). 28 days after the first surgery, animals were anesthetized; ECG recorded and right femoral artery and vein cannulated. Blood gas parameters and complete blood count were measured and the arterial-venous oxygen content difference (A-VO2) calculated. Results: QT interval and QTc in the CBDL+PPVL and CBDL groups were longer than those of the sham and PPVL groups. Furthermore, there were abnormal and bizarre T waves in the CBDL and CBDL+PPVL groups. In the CBDL+PPVL group, arterial O2 pressure was lower while arterial CO2 pressure and plasma concentration of HCO3- were higher than those of the other groups. A-VO2 in the CBDL+PPVL group was also lower than those of the other groups, and in the CBDL group was less than that of the PPVL group. Conclusions: In this study, we detected bizarre T waves and increased QT interval and QTc in the ECG of cirrhotic rats, which could be partly linked to the severity of liver dysfunction and reduction of metabolism.