Responses to voluntary hyperventilation in children with separation anxiety disorder: implications for the link to panic disorder

BACKGROUND

Biological theories on respiratory regulation have linked separation anxiety disorder (SAD) to panic disorder (PD). We tested if SAD children show similarly increased anxious and psychophysiological responding to voluntary hyperventilation and compromised recovery thereafter as has been observed in PD patients.

METHODS

Participants were 49 children (5-14 years old) with SAD, 21 clinical controls with other anxiety disorders, and 39 healthy controls. We assessed cardiac sympathetic and parasympathetic, respiratory (including pCO2), electrodermal, electromyographic, and self-report variables during baseline, paced hyperventilation, and recovery.

RESULTS

SAD children did not react with increased anxiety or panic symptoms and did not show signs of slowed recovery. However, during hyperventilation they exhibited elevated reactivity in respiratory variability, heart rate, and musculus corrugator supercilii activity indicating difficulty with respiratory regulation.

CONCLUSIONS

Reactions to hyperventilation are much less pronounced in children with SAD than in PD patients. SAD children showed voluntary breathing regulation deficits.

Acute effects of fructose consumption on uric acid and plasma lipids in patients with impaired renal function

OBJECTIVE

Metabolic disturbances are common in patients with renal function impairment and are related to high rates of cardiovascular incidents and mortality. Kidney transplantation leads to improved survival but may lead to additional metabolic alterations caused by immunosuppressive drugs and improved nutrition.

MATERIALS AND METHODS

The short-term effect of oral fructose load on serum uric acid (UA), plasma lipids, and blood pressure (BP) was studied in 85 patients with chronic kidney disease (CKD) and impairment of renal function (glomerular filtration rate 50-65 ml/min per 1.73 m(2)), comprising 55 renal transplant recipients (RTR) treated with standard triple immunosuppressive therapy including a calcineurin inhibitor (CNI) cyclosporine A (CsA) or tacrolimus (Tac) and 30 non-transplanted patients with CKD. Both non-transplanted CKD patients and RTR had stable renal function and a comparable degree of kidney dysfunction. All subjects received orally 70 g of fructose dissolved in 200 ml of water. Serum UA, lipids, and blood pressure were measured at baseline and 60, 120, 180, and 240 minutes after fructose administration.

RESULTS

There was a significant increase of serum UA concentration (p<0.001) in both CKD patients and RTR--CsA- or Tac-treated patients comparable in the latter. Total cholesterol (TC), LDL, and HDL cholesterol significantly decreased and serum triglycerides (TG) markedly increased in RTR, whereas in CKD patients all serum lipid fractions increased. Blood pressure was unaffected by fructose intake.

CONCLUSION

Both non-transplanted and transplanted patients with mild renal function impairment show similar acute purine metabolic disturbances following oral administration of fructose but in the latter dietary fructose may induce a smaller hyperlipidemic response.

Proline rich-oligopeptides: diverse mechanisms for antihypertensive action

Bradykinin-potentiating peptides from Bothrops jararaca (Bj) discovered in the early 1960s, were the first natural inhibitors of the angiotensin-converting enzyme (ACE). These peptides belong to a large family of snake venom proline-rich oligopeptides (PROs). One of these peptides, Bj-PRO-9a, was essential for defining ACE as effective drug target and development of captopril, an active site-directed inhibitor of ACE used worldwide for the treatment of human arterial hypertension. Recent experimental evidences demonstrated that cardiovascular effects exerted by different Bj-PROs are due to distinct mechanisms besides of ACE inhibition. In the present work, we have investigated the cardiovascular actions of four Bj-PROs, namely Bj-PRO-9a, -11e, -12b and -13a. Bj-PRO-9a acts upon ACE and BK activities to promote blood pressure reduction. Although the others Bj-PROs are also able to inhibit the ACE activity and to potentiate the BK effects, our results indicate that antihypertensive effect evoked by them involve new mechanisms. Bj-PRO-11e and Bj-PRO-12b involves induction of [Ca(2+)]i transients by so far unknown receptor proteins. Moreover, we have suggested argininosuccinate synthetase and M3 muscarinic receptor as targets for cardiovascular effects elicited by Bj-PRO-13a. In summary, the herein reported results provide evidence that Bj-PRO-mediated effects are not restricted to ACE inhibition or potentiation of BK-induced effects and suggest different actions for each peptide for promoting arterial pressure reduction. The present study reveals the complexity of the effects exerted by Bj-PROs for cardiovascular control, opening avenues for the better understanding of blood pressure regulation and for the development of novel therapeutic approaches.

Endothelial permeability in vitro and in vivo: protective actions of ANP and omapatrilat in experimental atherosclerosis

Increased arterial endothelial cell permeability (ECP) is considered an initial step in atherosclerosis. Atrial natriuretic peptide (ANP) which is rapidly degraded by neprilysin (NEP) may reduce injury-induced endothelial cell leakiness. Omapatrilat represents a first in class of pharmacological agents which inhibits both NEP and angiotensin converting enzyme (ACE). We hypothesized that ANP prevents thrombin-induced increases of ECP in human aortic ECs (HAECs) and that omapatrilat would reduce aortic leakiness and atherogenesis and enhance ANP mediated vasorelaxation of isolated aortas. Thrombin induced ECP determined by I(125) albumin flux was assessed in HAECs with and without ANP pretreatment. Next we examined the effects of chronic oral administration of omapatrilat (12 mg/kg/day, n=13) or placebo (n=13) for 8 weeks on aortic leakiness, atherogenesis and ANP-mediated vasorelaxation in isolated aortas in a rabbit model of atherosclerosis produced by high cholesterol diet. In HAECs, thrombin-induced increases in ECP were prevented by ANP. Omapatrilat reduced the area of increased aortic leakiness determined by Evans-blue dye and area of atheroma formation assessed by Oil-Red staining compared to placebo. In isolated arterial rings, omapatrilat enhanced vasorelaxation to ANP compared to placebo with and without the endothelium. ANP prevents thrombin-induced increases in ECP in HAECs. Chronic oral administration of omapatrilat reduces aortic leakiness and atheroma formation with enhanced endothelial independent vasorelaxation to ANP. These studies support the therapeutic potential of dual inhibition of NEP and ACE in the prevention of increased arterial ECP and atherogenesis which may be linked to the ANP/cGMP system.

Duration and magnitude of blood pressure below cerebral autoregulation threshold during cardiopulmonary bypass is associated with major morbidity and operative mortality

OBJECTIVES

Optimizing blood pressure using near-infrared spectroscopy monitoring has been suggested to ensure organ perfusion during cardiac surgery. Near-infrared spectroscopy is a reliable surrogate for cerebral blood flow in clinical cerebral autoregulation monitoring and might provide an earlier warning of malperfusion than indicators of cerebral ischemia. We hypothesized that blood pressure below the limits of cerebral autoregulation during cardiopulmonary bypass would be associated with major morbidity and operative mortality after cardiac surgery.

METHODS

Autoregulation was monitored during cardiopulmonary bypass in 450 patients undergoing coronary artery bypass grafting and/or valve surgery. A continuous, moving Pearson's correlation coefficient was calculated between the arterial pressure and low-frequency near-infrared spectroscopy signals and displayed continuously during surgery using a laptop computer. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was compared between patients with and without major morbidity (eg, stroke, renal failure, mechanical lung ventilation >48 hours, inotrope use >24 hours, or intra-aortic balloon pump insertion) or operative mortality.

RESULTS

Of the 450 patients, 83 experienced major morbidity or operative mortality. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was independently associated with major morbidity or operative mortality after cardiac surgery (odds ratio, 1.36; 95% confidence interval, 1.08-1.71; P = .008).

CONCLUSIONS

Blood pressure management during cardiopulmonary bypass using physiologic endpoints such as cerebral autoregulation monitoring might provide a method of optimizing organ perfusion and improving patient outcomes from cardiac surgery.

Short-term reduction in intrinsic heart rate during biventricular pacing after cardiac surgery: a substudy of a randomized clinical trial

BACKGROUND

The Biventricular Pacing After Cardiac Surgery trial investigates hemodynamics of temporary pacing in selected patients at risk of left ventricular dysfunction. This trial demonstrates improved hemodynamics during optimized biventricular pacing compared with atrial pacing at the same heart rate 1 and 2 hours after bypass and reduced vasoactive-inotropic score over the first 4 hours after bypass. However, this advantage of biventricular versus atrial pacing disappears 12 to 24 hours later. We hypothesized that changes in intrinsic heart rate can explain variable effects of atrial pacing in this setting.

METHODS

Heart rate, mean arterial pressure, cardiac output, and medications depressing heart rate were analyzed in patients randomized to continuous biventricular pacing (n = 16) or standard of care (n = 18).

RESULTS

During 30-second testing periods without pacing, intrinsic heart rate was lower in the paced group 12 to 24 hours after bypass (76.5 ± 17.5 vs 91.7 ± 13.0 beats per minute; P = .040) but not 1 or 2 hours after bypass. Cardiac output (4.4 ± 1.2 vs 3.6 ± 1.9 L/min; P = .054) and stroke volume (53 ± 2 vs 42 ± 2 mL; P = .051) increased overnight in the paced group. Vasoactive medication doses were not different between groups, whereas dexmedetomidine administration was prolonged over postoperative hours 12 to 24 in the paced group (793 ± 528 vs 478 ± 295 minutes; P = .013).

CONCLUSIONS

These observations suggest that hemodynamic benefits of biventricular pacing 12 to 24 hours after cardiopulmonary bypass lead to withdrawal of sympathetic drive and decreased intrinsic heart rate. Depression of intrinsic rate increases the apparent benefit of atrial pacing in the chronically paced group but not in the control group. Additional study is needed to define clinical benefits of these effects.

Effects of hypocretin and norepinephrine interaction in bed nucleus of the stria terminalis on arterial pressure

Forebrain neuronal circuits containing hypocretin-1 (hcrt-1) and norepinephrine (NE) are important components of central arousal-related processes. Recently, these two systems have been shown to have an overlapping distribution within the bed nucleus of the stria terminalis (BST), a limbic structure activated by stressful challenges, and which functions to adjust arterial pressure (AP) and heart rate (HR) to the stressor. However, whether hcrt-1 and NE interact in BST to alter cardiovascular function is unknown. Experiments were done in urethane-α-chloralose anesthetized, paralyzed, and artificially ventilated male Wistar rats to investigate the effect of hcrt-1 and NE on the cardiovascular responses elicited by l-glutamate (Glu) stimulation of BST neurons. Microinjections of hcrt-1, NE or tyramine into BST attenuated the decrease in AP and HR to Glu stimulation of BST. Additionally, combined injections of hcrt-1 with NE or tyramine did not elicit a greater attenuation than either compound alone. Furthermore, injections into BST of the α2-adrenergic receptor (α2-AR) antagonist yohimbine, but not the α1-AR antagonist 2-{[β-(4-hydroxyphenyl)ethyl]aminomethyl}-1-tetralone hydrochloride, blocked both the hcrt-1 and NE-induced inhibition of the BST cardiovascular depressors responses. Finally, injections into BST of the GABAA receptor antagonist bicuculline, but not the GABAB receptor antagonist phaclofen, blocked the hcrt-1 and NE attenuation of the BST Glu-induced depressor and bradycardia responses. These data suggest that hcrt-1 effects in BST are mediated by NE neurons, and hcrt-1 likely acts to facilitate the synaptic release of NE. NE neurons, acting through α2-AR may activate Gabaergic neurons in BST, which in turn through the activation of GABAA receptors inhibit a BST sympathoinhibitory pathway. Taken together, these data suggest that hcrt-1 pathways to BST through their interaction with NE and Gabaergic neurons may function in the coordination of cardiovascular responses associated with different behavioral states.

Lesion of the commissural nucleus of the solitary tract/A2 noradrenergic neurons facilitates the activation of angiotensinergic mechanisms in response to hemorrhage

In the present study, we investigated the effects of lesions of A2 neurons of the commissural nucleus of the solitary tract (cNTS) alone or combined with the blockade of angiotensinergic mechanisms on the recovery of arterial pressure (AP) to hemorrhage in conscious rats. Male Holtzman rats (280-320g) received an injection of anti-dopamine-beta-hydroxylase-saporin (12.6ng/60nl; cNTS/A2-lesion, n=28) or immunoglobulin G (IgG)-saporin (12.6ng/60nl, sham, n=24) into the cNTS and 15-21days later had a stainless steel cannula implanted in the lateral ventricle. After 6days, rats were submitted to hemorrhage (four blood withdrawals, 2ml/300g of body weight every 10min). Both cNTS/A2-lesioned and sham rats had similar hypotension to hemorrhage (-62±7 and -73±7mmHg, respectively), however cNTS/A2-lesioned rats rapidly recovered from hypotension (-5±3mmHg at 30min), whereas sham rats did not completely recover until the end of the recording (-20±3mmHg at 60min). Losartan (angiotensin type 1 receptor antagonist) injected intracerebroventricularly (100μg/1μl) or intravenously (i.v.) (10mg/kg of body weight) impaired the recovery of AP in cNTS/A2-lesioned rats (-24±6 and -35±7mmHg at 30min, respectively). In sham rats, only i.v. losartan affected the recovery of AP (-39±6mmHg at 60min). The results suggest that lesion of the A2 neurons in the cNTS facilitates the activation of the angiotensinergic pressor mechanisms in response to hemorrhage.

Reduced angiotensin II levels cause generalized vascular dysfunction via oxidant stress in hamster cheek pouch arterioles

OBJECTIVES

We investigated the effect of suppressing plasma angiotensin II (ANG II) levels on arteriolar relaxation in the hamster cheek pouch.

METHODS

Arteriolar diameters were measured via television microscopy during short-term (3-6days) high salt (HS; 4% NaCl) diet and angiotensin converting enzyme (ACE) inhibition with captopril (100mg/kg/day).

RESULTS

ACE inhibition and/or HS diet eliminated endothelium-dependent arteriolar dilation to acetylcholine, endothelium-independent dilation to the NO donor sodium nitroprusside, the prostacyclin analogs carbacyclin and iloprost, and the KATP channel opener cromakalim; and eliminated arteriolar constriction during KATP channel blockade with glibenclamide. Scavenging of superoxide radicals and low dose ANG II infusion (25ng/kg/min, subcutaneous) reduced oxidant stress and restored arteriolar dilation in arterioles of HS-fed hamsters. Vasoconstriction to topically-applied ANG II was unaffected by HS diet while arteriolar responses to elevation of superfusion solution PO2 were unaffected (5% O2, 10% O2) or reduced (21% O2) by HS diet.

CONCLUSIONS

These findings indicate that sustained exposure to low levels of circulating ANG II leads to widespread dysfunction in endothelium-dependent and independent vascular relaxation mechanisms in cheek pouch arterioles by increasing vascular oxidant stress, but does not potentiate O2- or ANG II-induced constriction of arterioles in the distal microcirculation of normotensive hamsters.

The efficacy and safety of a pharmacologic protocol for maintaining coronary artery bypass patients at a higher mean arterial pressure during cardiopulmonary bypass. 1998

A recent randomized trial of higher versus lower mean arterial pressure (MAP) during cardiopulmonary bypass (CPB) showed that higher MAP on CPB was associated with a lower incidence of overall cardiac and neurologic morbidity and mortality in coronary artery bypass graft surgery (CABG) patients. Cardiopulmonary bypass MAP was controlled pharmacologically while CPB flow was held constant for any given period. The objective of the present study was to assess the efficacy and safety of this pharmacologic protocol. Two hundred forty-eight patients participated in the study; the mean age was 65.8 ± 9.4 years, 20% were women, and the mean preoperative ejection fraction was 48%. The low-flow corrected CPB MAP attained for the low and high MAP groups was 56.7 ± 5.0 mmHg and 77.7 ± 7.1 mmHg, respectively (p = 0.0001). Major cardiac and neurologic outcomes, postoperative blood loss, renal dysfunction, intensive care unit (ICU) stay, and duration of intubation were not found to be significantly associated with any drug in the pharmacologic protocol. These findings support that the pharmacologic protocol used to maintain CABG patients at higher MAP on CPB is both efficacious and safe.

Nitric oxide and AQP2 in hypothyroid rats: a link between aging and water homeostasis

OBJECTIVE

Hypothyroid state and aging are associated with impairment in water reabsorption and changes in aquaporin water channel type 2 (AQP2). Nitric oxide (NO) is involved in AQP2 trafficking to the apical plasma membrane in medullary collecting duct cells. The purpose of this study was to investigate whether aging and hypothyroidism alter renal function, and whether medullary NO and AQP2 are implicated in maintaining water homeostasis.

MATERIALS/METHODS

Sprague-Dawley rats aged 2 and 18months old were treated with 0.02% methimazole (w/v) during 28days. Renal function was examined and NO synthase (NOS) activity ([(14)C (U)]-L-arginine to [(14)C (U)]-L-citrulline assays), NOS, caveolin-1 and -3 and AQP2 protein levels were determined in medullary tissue (Western blot). Plasma membrane fraction and intracellular vesicle fraction of AQP2 were evaluated by Western blot and immunohistochemistry.

RESULTS

A divergent response was observed in hypothyroid rats: while young rats exhibited polyuria with decreased medullary NOS activity, adult rats exhibited a decrease in urine output with increased NOS activity. AQP2 was increased with hypothyroidism, but while young rats exhibited increased AQP2 in plasma membrane, adult rats did so in the cytosolic site.

CONCLUSIONS

Hypothyroidism contributes in a differential way to aging-induced changes in renal function, and medullary NO and AQP2 would be implicated in maintaining water homeostasis.

Intermedin enhances sympathetic outflow via receptor-mediated cAMP/PKA signaling pathway in nucleus tractus solitarii of rats

Direct administration of intermedin (IMD) into the brain elicits cardiovascular effects different from the systemic administration. Nucleus tractus solitarii (NTS) is an important region for the cardiovascular regulation. The present study was designed to determine the effect of IMD on modulating the sympathetic outflow and its related molecular mechanism in the NTS. Renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) were recorded in anesthetized rats. Site-specific microinjection of IMD (20pmol) bilaterally into the NTS significantly increased RSNA and MAP. IMD-evoked increases of RSNA and MAP were almost abolished by pretreatment with receptor antagonist ADM22-52, an adenylyl cyclase (AC) inhibitor SQ22536, or a protein kinase A (PKA) inhibitor Rp-cAMP. However, pretreatment with another receptor antagonist calcitonin gene-related peptide (CGRP)8-37 did not suppress the increases of RSNA and MAP induced by IMD. Furthermore, IMD increased the cyclic adenosine monophosphate (cAMP) level, which was inhibited by ADM22-52 pretreatment in the NTS. These results suggest that IMD participates in the sympathetic nerve activity and central regulation of the cardiovascular system and a receptor-mediated cAMP/PKA signaling pathway is involved in IMD-induced effects in the NTS.

Evaluation of the inflammatory response in a two-hit acute lung injury model using [18F]FDG microPET

The aim of this study was to investigate whether a two-hit acute lung injury (ALI) model is better than a one-hit model in simulating ALI, and to evaluate the inflammatory response in the lungs in these two models using micro-positron emission tomography (microPET) with [¹⁸F]fluorodeoxyglucose (FDG). Sprague Dawley rats were divided into four groups; rats in the lipopolysaccharide (LPS; n=10) and LPS-HCl (n=10) groups were challenged by the intraperitoneal administration of 5 mg/kg LPS, while rats in the normal saline (NS; n=3) and HCl (n=10) groups received the same volume of normal saline solution. Sixteen hours following the administration, the rats in the HCl and LPS-HCl groups received an acid instillation (IT) of 0.5 ml/kg HCl (pH=1.2), while the rats in the remaining two groups received the same volume of normal saline solution. The mean arterial blood pressure (MAP) and blood gas concentrations were measured in all four groups. MicroPET was performed 4 h following HCl IT and the lungs were excised for histopathological examination. The rats in the LPS-HCl group exhibited a higher arterial PaO₂ and a lower arterial PaCO₂ compared with the rats in the remaining groups. The MAP decreased markedly in the LPS-HCl group, but remained stable in the LPS, HCl and NS groups. MicroPET results identified that the region of interest ratio in the LPS-HCl group (9.00±1.41) was significantly higher compared with those in the LPS (4.01±0.60) and HCl (3.33±0.55) groups (P<0.01). In addition, histological examination showed that the mean lung injury score in the LPS-HCl group (12.70±0.95) was significantly higher compared with those in the HCl (8.40±1.26) and LPS (7.00±0.82) groups (P<0.01). The present study demonstrates that LPS pretreatment significantly magnifies and prolongs the inflammatory response to subsequent acid IT in the lungs. Moreover, it is simpler to induce ALI using the two-hit model than with the one-hit model, and [¹⁸F]FDG microPET is a useful tool for evaluating the inflammatory reaction during ALI.

Neuropeptide W increases mean arterial pressure as a result of behavioral arousal

Neuropeptide W (NPW), an endogenous ligand for G protein-coupled receptors NPBWR1 (GPR7) and NPBWR2 (GPR8), has been detected in neurons in limbic and reticular activating system areas known to be important in arousal, as well as hypothalamic nuclei known to be important in food and water intake and the neuroendocrine response to stress. In rat, central administration of NPW increased mean arterial pressure (MAP) and behaviors associated with locomotion and grooming. We hypothesized that the NPW-induced increase in MAP was secondary to those increases in physical activity. Since peptides that stimulate arousal have been shown to increase sympathetic activity (e.g., orexin), we tested the ability of the mixed α1- and α2-adrenergic antagonist, phentolamine, to block the NPW-23-induced rise in MAP. Phentolamine pretreatment abrogated the NPW-induced MAP increase. However, we noticed the animals no longer exhibited NPW-associated behavioral arousal when pretreated with phentolamine. Anesthesia also blocked the NPW-induced increase in MAP, although the animals still were able to respond with an increase in MAP to centrally administered ANG II. Additionally, pretreatment with an orexin type 1 receptor antagonist significantly reduced the behavioral action of NPW-23 and completely blocked the peptide's action to increase MAP, suggesting that orexin neurons are downstream targets of NPW. Our results suggest that NPW increased MAP secondary to increased behavioral arousal.

Selective heart rate reduction with ivabradine unloads the left ventricle in heart failure patients

OBJECTIVES

The study aimed to determine whether isolated heart rate (HR) reduction with ivabradine reduces afterload of patients with systolic heart failure.

BACKGROUND

The effective arterial elastance (Ea) represents resistive and pulsatile afterload of the heart derived from the pressure volume relation. HR modulates Ea, and, therefore, afterload burden.

METHODS

Among the patients with systolic heart failure (ejection fraction ≤35%) randomized to either placebo or ivabradine in the SHIFT (Systolic Heart Failure Treatment With the If Inhibitor Ivabradine Trial), 275 patients (n = 132, placebo; n = 143, ivabradine 7.5 mg twice a day) were included in the echocardiographic substudy. Ea, total arterial compliance (TAC), and end-systolic elastance (Ees) were calculated at baseline and after 8 months of treatment. Blood pressure was measured by arm cuff; stroke volume (SV), ejection fraction, and end-diastolic volume were assessed by echocardiography.

RESULTS

At baseline Ea, TAC, HR, and Ees did not differ significantly between ivabradine- and placebo-treated patients. After 8 months of treatment, HR was significantly reduced in the ivabradine group (p < 0.0001) and was accompanied by marked reduction in Ea (p < 0.0001) and improved TAC (p = 0.004) compared with placebo. Although contractility remained unchanged, ventricular-arterial coupling was markedly improved (p = 0.002), resulting in a higher SV (p < 0.0001) in the ivabradine-treated patients.

CONCLUSIONS

Isolated HR reduction by ivabradine improves TAC, thus reducing Ea. Because Ees is unaltered, improved ventricular-arterial coupling is responsible for increased SV. Therefore, unloading of the heart may contribute to the beneficial effect of isolated HR reduction in patients with systolic heart failure.

Co-localization of hypocretin-1 and leucine-enkephalin in hypothalamic neurons projecting to the nucleus of the solitary tract and their effect on arterial pressure

Experiments were done to investigate whether hypothalamic hypocretin-1 (hcrt-1; orexin-A) neurons that sent axonal projections to cardiovascular responsive sites in the nucleus of the solitary tract (NTS) co-expressed leucine-enkephalin (L-Enk), and to determine the effects of co-administration of hcrt-1 and D-Ala2,D-Leu5-Enkephalin (DADL) into NTS on mean arterial pressure (MAP) and heart rate. In the first series, in the Wistar rat the retrograde tract-tracer fluorogold (FG) was microinjected (50nl) into caudal NTS sites at which L-glutamate (0.25 M; 10 nl) elicited decreases in MAP and where fibers hcrt-1 immunoreactive fibers were observed that also contained L-Enk immunoreactivity. Of the number of hypothalamic hcrt-1 immunoreactive neurons identified ipsilateral to the NTS injection site (1207 ± 78), 32.3 ± 2.3% co-expressed L-Enk immunoreactivity and of these, 2.6 ± 1.1% were retrogradely labeled with FG. Hcrt-1/L-Enk neurons projecting to NTS were found mainly within the perifornical region. In the second series, the region of caudal NTS found to contain axons that co-expressed hcrt-1 and L-Enk immunoreactivity was microinjected with a combination of hcrt-1 and DADL in α-chloralose anesthetized Wistar rats. Microinjection of DADL into NTS elicited depressor and bradycardia responses similar to those elicited by microinjection of hcrt-1. An hcrt-1 injection immediately after the DADL injection elicited an almost twofold increase in the magnitude of the depressor and bradycardia responses compared to those elicited by hcrt-1 alone. Prior injections of the non-specific opioid receptor antagonist naloxone or the specific opioid δ-receptor antagonist ICI 154,129 significantly attenuated the cardiovascular responses to the combined hcrt-1-DADL injections. Taken together, these data suggest that activation of hypothalamic-opioidergic neuronal systems contribute to the NTS hcrt-1 induced cardiovascular responses, and that this descending hypothalamo-medullary pathway may represent the anatomical substrate by which hcrt-1/L-Enk neurons function in the coordination of autonomic-cardiovascular responses during different behavioral states.

The effect of optimising cerebral tissue oxygen saturation on markers of neurological injury during coronary artery bypass graft surgery

BACKGROUND

Surgical revascularisation of the coronary arteries is a cornerstone of cardiothoracic surgery. Advanced age and the incidence of preoperative co-morbidity in patients presenting for coronary artery bypass graft surgery increases the potential for stroke and other perioperative outcomes. It is hypothesised that by using interventions during cardiac surgery to improve cerebral oxygenation, the risk of patients enduring adverse neurological outcomes would be reduced.

METHODS

Forty patients (mean age 55.3, standard deviation 9.74 and range from 39 to 72 years) undergoing on-pump coronary artery bypass graft surgery were recruited at Inkosi Albert Luthuli Central Hospital, South Africa. Patients were randomised into a control group (n=20) and interventional group (n=20). Intraoperative regional cerebral oxygen saturation (rSO2) monitoring with active display and Murkin treatment intervention protocol was administered for the interventional group. Arterial blood samples for the measurement of serum S100B were taken pre and postoperatively. An enzyme immunoassay (ELISA) was used for the quantitative and comparative measurement of human S100B concentrations for both groups. A prioritised intraoperative management protocol to maintain rSO2 values above 75% of the baseline threshold during cardiopulmonary bypass was followed.

RESULTS

There was a highly significant difference in the change in S100B concentrations post surgery between the interventional (37.3picograms per millilitre) and control groups (139.3pg/ml). The control group showed a significantly higher increase in S100B concentration over time than the intervention group (p<0.001). There was a significant difference in cerebral desaturation time (p<0.001) between the groups. The mean desaturation time for the control group was 63.85min as compared to 24.7min in the interventional group. Cerebral desaturation occurred predominantly during aortic cross clamping, distal anastomosis of coronary arteries and aortic cross clamp release. Predictors of cerebral oxygen desaturation included, partial pressure of carbon dioxide (pCO2), temperature, pump flow rate (LMP), mean arterial pressure (MAP), haematocrit, heart rate (HR) and patient oxygen saturation (SpO2).

CONCLUSION

Monitoring brain oxygen saturation during on-pump CABG together with an effective treatment protocol to deal with cerebral desaturation must be advocated.

An examination of cardiovascular collapse induced by eastern brown snake (Pseudonaja textilis) venom

The Pseudonaja genus (Brown snakes) is widely distributed across Australia and bites account for significant mortality. Venom-induced consumption coagulopathy (VICC) and, less often, early cardiovascular collapse occur following envenoming by these snakes. We have previously examined possible mechanism(s) behind the early cardiovascular collapse following Papuan taipan (Oxyuranus scutellatus) envenoming. In the present study, we investigate early cardiovascular collapse in anaesthetized rats following administration of eastern brown snake (Pseudonaja textilis) venom, and prevention of this effect with prior administration of 'priming' doses (i.e. doses of venom which caused a transient hypotensive response) of venom. P. textilis venom (5-10 μg/kg, i.v.) induced cardiovascular collapse in anaesthetized rats, characterized by a rapid decrease in systolic blood pressure until non recordable. Prior administration of 'priming' doses of P. textilis venom (2 and 3 μg/kg) or, at least, 4-5 doses of O. scutellatus (2 μg/kg, i.v.) or Daboia russelii limitis (20 μg/kg, i.v.) venoms prevented cardiovascular collapse induced by P. textilis venom. Moreover, early collapse was also inhibited by prior administration of 2 discrete doses of Acanthophis rugosus venom. Prior administration of commercial polyvalent snake antivenom (500-3000 units/kg, i.v.) or heparin (300 units/kg, i.v.) also inhibited P. textilis venom-induced cardiovascular collapse. Our results indicate that P. textilis venom-induced cardiovascular collapse can be prevented by prior administration of sub-lethal doses of venom from P. textilis, O. scutellatus, A. rugosus and D. russelii limitis. This suggests that sudden cardiovascular collapse following envenoming is likely to involve a common mechanism/pathway activated by different snake venoms.

Control of hypertension in the critically ill: a pathophysiological approach

Severe acute arterial hypertension can be associated with significant morbidity and mortality. After excluding a reversible etiology, choice of therapeutic intervention should be based on evaluation of a number of factors, such as age, comorbidities, and other ongoing therapies. A rational pathophysiological approach should then be applied that integrates the effects of the drug on blood volume, vascular tone, and other determinants of cardiac output. Vasodilators, calcium channel blockers, and beta-blocking agents can all decrease arterial pressure but by totally different modes of action, which may be appropriate or contraindicated in individual patients. There is no preferred agent for all situations, although some drugs may have a more attractive profile than others, with rapid onset action, short half-life, and fewer adverse reactions. In this review, we focus on the main mechanisms underlying severe hypertension in the critically ill and how using a pathophysiological approach can help the intensivist decide on treatment options.

Impact of periprocedural bleeding on incidence of contrast-induced acute kidney injury in patients treated with percutaneous coronary intervention

OBJECTIVES

This study sought to evaluate the association between contrast-induced acute kidney injury (CI-AKI) after percutaneous coronary intervention and severity of bleeding estimated from periprocedural hemoglobin (Hb) measurement.

BACKGROUND

The relationship between CI-AKI and bleeding in contemporary practice remains controversial.

METHODS

In a retrospective analysis of the prospectively maintained Japan Cardiovascular Database-Keio Interhospital Cardiovascular Studies (JCD-KICS) multicenter registry, we divided 2,646 consecutive patients into 5 groups according to the change of Hb level after compared with before percutaneous coronary intervention: patients without a decrease in Hb level (group A) and patients with a decreased Hb level: <1 g/dl (group B); 1 to <2 g/dl (group C); 2 to <3g/dl (group D); and >3 g/dl (group E). CI-AKI was defined as an increase in serum creatinine level ≥ 0.5 mg/dl or ≥ 25% above baseline values at 48 h after administration of contrast media. Procedure and outcome variables were compared.

RESULTS

The mean patient age was 67 ± 11 years. Of the 2,646 patients, CI-AKI developed in 315 (11.9%). The CI-AKI incidence was 6.2%, 7.5%, 10.7%, 17.0%, and 26.2%, in groups A through E, respectively (p < 0.01), whereas the incidence of major bleeding was 0.7%, 1.3%, 2.0%, 4.1%, and 28.3%, respectively (p < 0.01). CI-AKI was associated with higher rates of mortality (5.4% vs. 0.6%, p < 0.01) and of composite of heart failure, cardiogenic shock, and death (16.5% vs. 2.8%, p < 0.01).

CONCLUSIONS

Periprocedural bleeding was significantly associated with CI-AKI, with CI-AKI incidence correlating with bleeding severity.

Pressor and renal regional hemodynamic effects of urotensin II in neonatal pigs

Renal expression of the peptide hormone urotensin II (UII) and its receptor (UTR) are dependent on kidney maturation and anatomical regions. However, renal regional hemodynamic effects of UII in neonates are unclear. Here, we investigated regional hemodynamic responses to acute intrarenal arterial administration of UII in newborn pigs. Western immunoblotting and immunofluorescence confirmed UTR expression and membrane localization in newborn pig renal afferent arterioles and afferent arteriolar smooth muscle cells respectively. Intrarenal arterial bolus injections of human UII (hUII; 1-100  ng/kg) resulted in a dose-dependent decrease in total renal blood flow (RBF) and an increase in mean arterial pressure (MAP) and renal vascular resistance (RVR) in newborn pigs. Moreover, hUII dose dependently reduced cortical blood flow (CBF) but increased medullary blood flow (MBF) in the piglets. hUII-induced MAP elevation and hemodynamic changes were inhibited by urantide, a UTR antagonist, but not losartan, a type 1 angiotensin II receptor antagonist. U-73122, a phospholipase C (PLC) inhibitor, and 2-aminoethoxydiphenyl borate, an inositol 1,4,5 trisphosphate (IP₃) receptor antagonist, attenuated hUII-induced MAP and RVR elevations, RBF and CBF reductions, but not MBF increase. These findings indicate that intrarenal arterial administration of hUII elevates blood pressure and induces region-selective renal hemodynamic changes in newborn pigs. Our data also suggest that the PLC/IP₃ signaling pathway contributes to hUII-induced alterations in MAP, RBF, RVR, and CBF but not MBF in newborn pigs.

Urinary exosome miRNome analysis and its applications to salt sensitivity of blood pressure

OBJECTIVES

To investigate microRNAs (miRNAs) in urinary exosomes and their association with an individual's blood pressure response to dietary salt intake.

DESIGN AND METHODS

Human urinary exosomal miRNome was examined by microarray.

RESULTS

Of 1898 probes tested, 194 miRNAs were found in all subjects tested. 45 miRNAs had significant associations with salt sensitivity or inverse salt sensitivity.

CONCLUSION

The expression of 45 urinary exosomal miRNAs associates with an individual's blood pressure response to sodium.

Contribution of iNOS/sGC/PKG pathway, COX-2, CYP4A1, and gp91(phox) to the protective effect of 5,14-HEDGE, a 20-HETE mimetic, against vasodilation, hypotension, tachycardia, and inflammation in a rat model of septic shock

We have previously demonstrated that a stable synthetic analog of 20-hydroxyeicosatetraenoic acid (20-HETE), N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-HEDGE), prevents vascular hyporeactivity, hypotension, tachycardia, and inflammation in rats treated with lipopolysaccharide (LPS) and mortality in endotoxemic mice. These changes were attributed to decreased production of inducible nitric oxide (NO) synthase (iNOS)-derived NO, cyclooxygenase (COX)-2-derived vasodilator prostanoids, and proinflammatory mediators associated with increased cyctochrome P450 (CYP) 4A1-derived 20-HETE and CYP2C23-dependent antiinflammatory mediator formation. The aim of this study was to determine whether decreased expression and activity of iNOS, soluble guanylyl cyclase (sGC), protein kinase G (PKG), COX-2, gp91(phox) (NOX2; a superoxide generating NOX enzyme), and peroxynitrite production associated with increased expression of COX-1 and CYP4A1 and 20-HETE formation in renal and cardiovascular tissues of rats contributes to the effect of 5,14-HEDGE to prevent vasodilation, hypotension, tachycardia, and inflammation in response to systemic administration of LPS. Mean arterial pressure fell by 28mmHg and heart rate rose by 47beats/min in LPS (10mg/kg, i.p.)-treated rats. Administration of LPS also increased mRNA and protein expression of iNOS and COX-2 associated with a decrease in COX-1 and CYP4A1 mRNA and protein expression. Increased NOS activity, iNOS-heat shock protein 90 complex formation (an index for iNOS activity), protein expression of phosphorylated vasodilator stimulated phosphoprotein (an index for PKG activity), gp91(phox), p47(phox) (NOXO2; organizer subunit of gp91(phox)), and nitrotyrosine (an index for peroxynitrite production) as well as cGMP (an index for sGC activity), 6-keto-PGF1α (a stable metabolite PGI2) and PGE2 levels (indexes for COX activity), and nitrotyrosine levels by LPS were also associated with decreased CYP hydroxylase activity as measured by 20-HETE formation from arachidonic acid in renal microsomes of LPS-treated rats. These effects of LPS, except iNOS mRNA and COX-1 protein expression, were prevented by 5,14-HEDGE (30mg/kg, s.c.; 1h after LPS). A competitive antagonist of vasoconstrictor effects of 20-HETE, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (30mg/kg, s.c.; 1h after LPS) reversed the effects of 5,14-HEDGE, except iNOS and COX-1 mRNA and protein expression as well as expression of CYP4A1 mRNA. These results suggest that increased CYP4A1 expression and 20-HETE formation associated with suppression of iNOS/sGC/PKG pathway, COX-2, and gp91(phox) participate in the protective effect of 5,14-HEDGE against vasodilation, hypotension, tachycardia, and inflammation in the rat model of septic shock.

Cavoaortic shunt improves hemodynamics with preserved oxygen delivery in experimental right ventricular failure during left ventricular assist device therapy

OBJECTIVE

Right heart failure is a major cause of morbidity and mortality after left ventricular assist device (LVAD) implantation. This study evaluated the approach of a cavoaortic shunt included in the LVAD circuit, which would aim to relieve venous congestion and improve hemodynamics with preserved oxygen delivery during induced right ventricular failure.

METHODS

Right ventricular failure was induced by coronary ligation in 10 pigs. An LVAD was implanted and a cavoaortic shunt was created from the right atrium and included in the assist circuit. Hemodynamic measures and blood gas analyses were analyzed. Oxygen delivery and oxygen consumption were estimated.

RESULTS

Right atrial pressure decreased from more than 20 mm Hg to 17.2 mm Hg (14.8-18.4) with the LVAD and to 14.1 mm Hg (11.2-15.5) (P < .01) with the LVAD and cavoaortic shunt. Mean arterial pressure increased from 70.9 mm Hg (67.6-79.8) to 81.5 mm Hg (70.8-92.6) (P = .02) with addition of the shunt into the assist circuit. Cardiac output increased from 3.5 L/min (2.6-4.2) to 4.9 L/min (3.5-5.6) (P < .01) with cavoaortic shunting. Oxygen delivery with the cavoaortic shunt was 337 mL/min (± 70) as compared with left ventricular assist alone at 258 mL/min (± 52) (P < .01). Oxygen consumption was restored during use of the cavoaortic shunt.

CONCLUSIONS

A cavoaortic shunt combined with an LVAD during right ventricular failure reduces central venous pressures, increases systemic arterial pressure, and enables increased cardiac output compared with device therapy alone. This was feasible with preserved oxygen delivery.

High ferritin and low transferrin saturation are associated with pre-diabetes among a national representative sample of U.S. adults

BACKGROUND & AIMS

Iron overload is known to cause diabetes. However, the underlying mechanism is poorly understood. We therefore studied the association of different markers of iron metabolism, namely ferritin, erythrocyte protoporphyrin and transferrin saturation (TSAT, as defined by a percentage of transferrin that is saturated with iron) with pre-diabetes (preDM) in US adults without chronic kidney disease, anemia, and iron deficiency.

METHODS

Data on 2575 participants of the National Health and Nutrition Examination Survey (NHANES) 1999-2002 who were free of diabetes, chronic kidney disease, iron deficiency, and anemia were analyzed. Data on 3876 participants of the NHANES III (1988-1994) were used as replication. Homeostasis model assessment of insulin resistance (HOMA-IR), blood glycosylated hemoglobin level (HbA1C), fasting glucose, insulin, and preDM (defined as a fasting plasma glucose 100-125 mg/dl or an HBA1C value 5.7-6.4%) were measured as the outcomes.

RESULTS

Logistic regression analyses indicated independent associations of high ferritin (Ptrend = 0.028) and low TSAT (P(trend) = 0.029) with preDM after adjusting for sociodemographics, physical activity (active/sedementary), metabolic and inflammatory markers (triglycerides, total cholesterol, HDL cholesterol, mean arterial pressure, CRP, white cell count, and albumin), and liver enzymes (GGT, Alk phos, AST, and ALT). The NHANES III data showed similar associations. Combining the results showed a more significant association for high ferritin (P(meta) = 0.016) and low TSAT (P(meta) = 0.002). Moreover, TSAT was associated with HbA1C, fasting glucose, insulin, and HOMA-IR (P(meta) ≤ 0.001).

CONCLUSIONS

Higher ferritin and lower TSAT are associated with higher risk of preDM in a general population without confounding diseases. Further research is needed to examine the underlying mechanism of these two indices, especially TSAT, in the pathophysiology of preDM.