Na/H Exchange Inhibition Protects Newborn Heart From Ischemia/Reperfusion Injury by Limiting Na+-dependent Ca2+ Overload

The results of the Guardian/Expedition trials demonstrate the need for more precisely controlled studies to inhibit Na/H exchange (NHE1) during ischemia/reperfusion. This is because overwhelming evidence is consistent with the hypothesis that myocardial ischemic injury results in part from increases in intracellular Na (Nai) mediated by NHE1 that in turn promote Na/Ca exchanger-mediated increases in intracellular Ca ([Ca]i) and Ca-dependent cell damage. We used a more potent and specific NHE1 inhibitor HOE 694 (HOE) to test whether inhibition of NHE1 during ischemia limits increases in Nai and [Ca]i in newborns. NMR was used to measure pHi, Nai, [Ca]i, and ATP in isolated newborn rabbit hearts. Perfusion pressure, left ventricular developed pressure, and creatine kinase were measured. HOE was added before global ischemia. Results are reported as mean +/- SE. Nai (mEq/kg dry weight) rose from 11.6 +/- 0.9 before ischemia to 114.0 +/- 16.1 at the end of ischemia and recovered to 55.2 +/- 11.8 in the control group. During ischemia and reperfusion, the corresponding values for Nai in the HOE group (63.1 +/- 8.4 and 15.9 +/- 2.5, respectively, P < 0.05) were lower than control. In the control group [Ca]i (nM/L) rose from 331 +/- 41 to 1069 +/- 71 and recovered to 814 +/- 51, whereas in the HOE group [Ca]i rose less (P < 0.05): 359 +/- 50, 607 +/- 85, and 413 +/- 40, respectively. Total creatine kinase release was significantly reduced in the HOE group. Perfusion pressure and left ventricular developed pressure also recovered significantly better in the HOE group than in the control. In conclusion, NHE1 inhibition diminishes ischemia-induced increases in Nai and therefore [Ca], and thus diminishes myocardial injury in neonatal hearts

The impact of prescription pain reliever misuse and heroin use on morbidity and mortality by level of urbanicity: 2002-2014

Non-medical use of prescription pain relievers (PPRs), heroin, and more recently fentanyl, continue to have major public health consequences in the United States. This article analyzes trends in PPR and heroin use, emergency department and hospital stays, substance use treatment services, and mortality to assess the relative impact of the opioid crisis on rural versus more urbanized counties in the United States. Our findings suggest that while more urbanized counties have had greater increases in opioid use, rural and less urbanized counties tended to be more negatively impacted than larger and non-rural counties. Disparities in service availability highlight the need for a serious discussion on how resources are allocated in counties that have lower tax bases. Based on these results, we conclude that rural and less urbanized counties can benefit from real increases in resources for substance use prevention and treatment services, including the expansion of prescribers trained to screen and treat opioid use. Understanding the unique challenges of rural and less urbanized counties may help decrease the disparity in consequences found in this study

Effects of cold cardioplegia on pH, Na, and Ca in newborn rabbit hearts

Many studies suggest myocardial ischemia-reperfusion (I/R) injury results largely from cytosolic proton (H(i))-stimulated increases in cytosolic Na (Na(i)), which cause Na/Ca exchange-mediated increases in cytosolic Ca concentration ([Ca]i). Because cold, crystalloid cardioplegia (CCC) limits [H]i, we tested the hypothesis that in newborn hearts, CCC diminishes H(i), Na(i), and Ca(i) accumulation during I/R to limit injury. NMR measured intracellular pH (pH(i)), Na(i), [Ca]i, and ATP in isolated Langendorff-perfused newborn rabbit hearts. The control ischemia protocol was 30 min for baseline perfusion, 40 min for global ischemia, and 40 min for reperfusion, all at 37 degrees C. CCC protocols were the same, except that ice-cold CCC was infused for 5 min before ischemia and heart temperature was lowered to 12 degrees C during ischemia. Normal potassium CCC solution (NKCCC) was identical to the control perfusate, except for temperature; the high potassium (HKCCC) was identical to NKCCC, except that an additional 11 mmol/l KCl was substituted isosmotically for NaCl. NKCCC and HKCCC were not significantly different for any measurement. The following were different (P < 0.05). End-ischemia pH(i) was higher in the CCC than in the control group. Similarly, CCC limited increases in Na(i) during I/R. End-ischemia Na(i) values (in meq/kg dry wt) were 115 +/- 16 in the control group, 49 +/- 13 in the NKCCC group, and 37 +/- 12 in the HKCCC group. CCC also improved [Ca]i recovery during reperfusion. After 40 min of reperfusion, [Ca](i) values (in nmol/l) were 302 +/- 50 in the control group, 145 +/- 13 in the NKCCC group, and 182 +/- 19 in the HKCCC group. CCC limited ATP depletion during ischemia and improved recovery of ATP and left ventricular developed pressure and decreased creatine kinase release during reperfusion. Surprisingly, CCC did not significantly limit [Ca]i during ischemia. The latter is explained as the result of Ca release from intracellular buffers on cooling

Phosphorylation and Activation of the Plasma Membrane Na+/H+ Exchanger (NHE1) during Osmotic Cell Shrinkage

The Na+/H+ Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na+/H+ exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na+/H+ exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na+ transport capacity without affecting transport affinity (Km = 44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ 32P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na+ transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events

Hyperdense artery sign, symptomatic infarct swelling and effect of alteplase in acute ischaemic stroke

Alteplase improves functional outcomes of patients with acute ischaemic stroke, but its effects on symptomatic infarct swelling, an adverse complication of stroke and the influence of CT hyperdense artery sign (HAS) are unclear. This substudy of the Third International Stroke Trial aimed to investigate the association between HAS and symptomatic infarct swelling and effect of intravenous alteplase on this association. We included stroke patients whose prerandomisation scan was non-contrast CT. Raters, masked to clinical information, assessed baseline (prerandomisation) and follow-up (24-48 hours postrandomisation) CT scans for HAS, defined as an intracranial artery appearing denser than contralateral arteries. Symptomatic infarct swelling was defined as clinically significant neurological deterioration ≤7 days after stroke with radiological evidence of midline shift, effacement of basal cisterns or uncal herniation. Among 2961 patients, HAS presence at baseline was associated with higher risk of symptomatic infarct swelling (OR 2.21; 95% CI 1.42 to 3.44). Alteplase increased the risk of swelling (OR 1.69; 95% CI 1.11 to 2.57), with no difference between patients with and those without baseline HAS (p=0.49). In patients with baseline HAS, alteplase reduced the proportion with HAS at follow-up (OR 0.67; 95% CI 0.50 to 0.91), where HAS disappearance was associated with reduced risk of swelling (OR 0.25, 95% CI 0.14 to 0.47). Although alteplase was associated with increased risk of symptomatic infarct swelling in patients with or without baseline HAS, it was also associated with accelerated clearance of HAS, which in return reduced swelling, providing further mechanistic insights to underpin the benefits of alteplase

Prehospital transdermal glyceryl trinitrate in patients with ultra-acute presumed stroke (RIGHT-2): an ambulance-based, randomised, sham-controlled, blinded, phase 3 trial

Background: High blood pressure is common in acute stroke and is a predictor of poor outcome; however, large trials of lowering blood pressure have given variable results, and the management of high blood pressure in ultra-acute stroke remains unclear. We investigated whether transdermal glyceryl trinitrate (GTN; also known as nitroglycerin), a nitric oxide donor, might improve outcome when administered very early after stroke onset. Methods: We did a multicentre, paramedic-delivered, ambulance-based, prospective, randomised, sham-controlled, blinded-endpoint, phase 3 trial in adults with presumed stroke within 4 h of onset, face-arm-speech-time score of 2 or 3, and systolic blood pressure 120 mm Hg or higher. Participants were randomly assigned (1:1) to receive transdermal GTN (5 mg once daily for 4 days; the GTN group) or a similar sham dressing (the sham group) in UK-based ambulances by paramedics, with treatment continued in hospital. Paramedics were unmasked to treatment, whereas participants were masked. The primary outcome was the 7-level modified Rankin Scale (mRS; a measure of functional outcome) at 90 days, assessed by central telephone follow-up with masking to treatment. Analysis was hierarchical, first in participants with a confirmed stroke or transient ischaemic attack (cohort 1), and then in all participants who were randomly assigned (intention to treat, cohort 2) according to the statistical analysis plan. This trial is registered with ISRCTN, number ISRCTN26986053. Findings: Between Oct 22, 2015, and May 23, 2018, 516 paramedics from eight UK ambulance services recruited 1149 participants (n=568 in the GTN group, n=581 in the sham group). The median time to randomisation was 71 min (IQR 45–116). 597 (52%) patients had ischaemic stroke, 145 (13%) had intracerebral haemorrhage, 109 (9%) had transient ischaemic attack, and 297 (26%) had a non-stroke mimic at the final diagnosis of the index event. In the GTN group, participants' systolic blood pressure was lowered by 5·8 mm Hg compared with the sham group (p<0·0001), and diastolic blood pressure was lowered by 2·6 mm Hg (p=0·0026) at hospital admission. We found no difference in mRS between the groups in participants with a final diagnosis of stroke or transient ischaemic stroke (cohort 1): 3 (IQR 2–5; n=420) in the GTN group versus 3 (2–5; n=408) in the sham group, adjusted common odds ratio for poor outcome 1·25 (95% CI 0·97–1·60; p=0·083); we also found no difference in mRS between all patients (cohort 2: 3 [2–5]; n=544, in the GTN group vs 3 [2–5]; n=558, in the sham group; 1·04 [0·84–1·29]; p=0·69). We found no difference in secondary outcomes, death (treatment-related deaths: 36 in the GTN group vs 23 in the sham group [p=0·091]), or serious adverse events (188 in the GTN group vs 170 in the sham group [p=0·16]) between treatment groups. Interpretation: Prehospital treatment with transdermal GTN does not seem to improve functional outcome in patients with presumed stroke. It is feasible for UK paramedics to obtain consent and treat patients with stroke in the ultra-acute prehospital setting

The Abdominal Circulatory Pump

Blood in the splanchnic vasculature can be transferred to the extremities. We quantified such blood shifts in normal subjects by measuring trunk volume by optoelectronic plethysmography, simultaneously with changes in body volume by whole body plethysmography during contractions of the diaphragm and abdominal muscles. Trunk volume changes with blood shifts, but body volume does not so that the blood volume shifted between trunk and extremities (Vbs) is the difference between changes in trunk and body volume. This is so because both trunk and body volume change identically with breathing and gas expansion or compression. During tidal breathing Vbs was 50–75 ml with an ejection fraction of 4–6% and an output of 750–1500 ml/min. Step increases in abdominal pressure resulted in rapid emptying presumably from the liver with a time constant of 0.61±0.1SE sec. followed by slower flow from non-hepatic viscera. The filling time constant was 0.57±0.09SE sec. Splanchnic emptying shifted up to 650 ml blood. With emptying, the increased hepatic vein flow increases the blood pressure at its entry into the inferior vena cava (IVC) and abolishes the pressure gradient producing flow between the femoral vein and the IVC inducing blood pooling in the legs. The findings are important for exercise because the larger the Vbs the greater the perfusion of locomotor muscles. During asystolic cardiac arrest we calculate that appropriate timing of abdominal compression could produce an output of 6 L/min. so that the abdominal circulatory pump might act as an auxiliary heart

Blood pressure variability and leukoaraiosis in acute ischemic stroke

Higher blood pressure, blood pressure variability, and leukoaraiosis are risk factors for early adverse events and poor functional outcome after ischemic stroke, but prior studies differed on whether leukoaraiosis was associated with blood pressure variability, including in ischemic stroke. In the Third International Stroke Trial, blood pressure was measured in the acute phase of ischemic stroke immediately prior to randomization, and at 0.5, 1, and 24 h after randomization. Masked neuroradiologists rated index infarct, leukoaraiosis, and atrophy on CT using validated methods. We characterized blood pressure variation by coefficient of variance and three other standard methods. We measured associations between blood pressure, blood pressure variability, and leukoaraiosis using generalized estimating equations, adjusting for age, and a number of covariates related to treatment and stroke type/severity. Among 3017 patients, mean (±SD) systolic and diastolic blood pressure decreased from 155(±24)/82(±15) mmHg pre-randomization to 146(±23)/78(±14) mmHg 24 h later ( P < 0.005). Mean within-subject coefficient of variance was 0.09 ± 0.05 for systolic and 0.11 ± 0.06 for diastolic blood pressure. Patients with most leukoaraiosis were older and had higher blood pressure than those with least ( P < 0.0001). Although statistically significant in simple pairwise comparisons, no measures of blood pressure variability were associated with leukoaraiosis when adjusting for confounding variables ( P > 0.05), e.g. age. Our results suggest that blood pressure variability is not a potential mechanism to explain the association between leukoaraiosis and poor outcome after acute stroke

Prehospital transdermal glyceryl trinitrate for ultra-acute intracerebral hemorrhage

Background and Purpose—Pilot trials suggest that glyceryl trinitrate (GTN; nitroglycerin) may improve outcome when administered early after stroke onset. Methods—We undertook a multicentre, paramedic-delivered, ambulance-based, prospective randomized, sham-controlled, blinded-end point trial in adults with presumed stroke within 4 hours of ictus. Participants received transdermal GTN (5 mg) or a sham dressing (1:1) in the ambulance and then daily for three days in hospital. The primary outcome was the 7-level modified Rankin Scale at 90 days assessed by central telephone treatment-blinded follow-up. This prespecified subgroup analysis focuses on participants with an intracerebral hemorrhage as their index event. Analyses are intention-to-treat. Results—Of 1149 participants with presumed stroke, 145 (13%; GTN, 74; sham, 71) had an intracerebral hemorrhage: time from onset to randomization median, 74 minutes (interquartile range, 45–110). By admission to hospital, blood pressure tended to be lower with GTN as compared with sham: mean, 4.4/3.5 mmHg. The modified Rankin Scale score at 90 days was nonsignificantly higher in the GTN group: adjusted common odds ratio for poor outcome, 1.87 (95% CI, 0.98–3.57). A prespecified global analysis of 5 clinical outcomes (dependency, disability, cognition, quality of life, and mood) was worse with GTN; Mann-Whitney difference, 0.18 (95% CI, 0.01–0.35; Wei-Lachin test). GTN was associated with larger hematoma and growth, and more mass effect and midline shift on neuroimaging, and altered use of hospital resources. Death in hospital but not at day 90 was increased with GTN. There were no significant betweengroup differences in serious adverse events. Conclusions—Prehospital treatment with GTN worsened outcomes in patients with intracerebral hemorrhage. Since these results could relate to the play of chance, confounding, or a true effect of GTN, further randomized evidence on the use of vasodilators in ultra-acute intracerebral hemorrhage is needed

Effect of alteplase on the CT hyperdense artery sign and functional outcome after ischemic stroke

© 2015 American Academy of Neurology. STUDY FUNDING The startup phase of IST-3 was supported by a grant from the Stroke Association, UK (TSA 04/99). The expansion phase was funded by the Health Foundation UK (2268/1282). The scan reading development was funded by Chest, Heart Stroke Scotland (R100/7). The main phase of the trial is funded by UK Medical Research Council (MRC) (grant numbers G0400069 and EME 09-800-15) and managed by NIHR on behalf of the MRC-NIHR partnership; the Research Council of Norway; Arbetsmarknadens Partners Forsakringsbolag (AFA) Insurances Sweden; the Swedish Heart Lung Fund; The Foundation of Marianne and Marcus Wallenberg, Stockholm County Council; Karolinska Institute Joint ALF-project grants Sweden; the Polish Ministry of Science and Education (grant number 2PO5B10928); the Australian Heart Foundation; Australian National Health and Medical Research Council (NHMRC); the Swiss National Research Foundation; the Swiss Heart Foundation; the Foundation for Health and Cardio-/Neurovascular Research, Basel, Switzerland; the Assessorato alla Sanita, Regione dell'Umbria, Italy; and, Danube University, Krems, Austria. Boehringer-Ingelheim GmbH donated drug and placebo for the 300 patients in the double-blind phase, but thereafter had no role in the trial. The UK Stroke Research Network (SRN study ID 2135) adopted the trial on 1/5/2006, supported the initiation of new UK sites, and in some centers, and, after that date, data collection was undertaken by staff funded by the network or working for associated NHS organizations. IST-3 acknowledges the support of the NIHR Stroke Research Network, NHS Research Scotland (NRS), through the Scottish Stroke Research Network, and the National Institute for Social Care and Health Research Clinical Research Centre (NISCHR CRC). The central imaging work was undertaken at the Brain Imaging Research Centre (www.sbirc.ed.ac.uk), a member of the Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) collaboration (www.sinapse.ac.uk), at the Division of Clinical Neurosciences, University of Edinburgh. SINAPSE is funded by the Scottish Funding Council (SFC) and the Chief Scientist Office of the Scottish Executive (CSO). Additional support was received from Chest Heart and Stroke Scotland, DesAcc, University of Edinburgh, Danderyd Hospital R&D Department, Karolinska Institutet, Oslo University Hospital, and the Dalhousie University Internal Medicine Research Fund.Peer reviewedPublisher PD