Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sodium cyanide was infused intravenously in 11 lightly anaesthetised and spontaneously breathing M. mulatta. In most, the EEG, ECG, respiratory rate, blood pressure, cerebral venous sinus pressure, end-tidal pCO2 and body temperature were recorded. Blood gases, pH, lactate and pyruvate were estimated in arterial and venous sinus blood samples. There was an initial hyperventilation with tetany in all animals. A rapid rate of cyanide infusion led to apnoea. An isoelectric or near-isoelectric EEG was usually precipitated by bradycardia often with additional hypotension. Neither epileptic seizures nor their EEG concomitants were seen at any stage. Three animals died of early heart failure. Brain damage was seen in 4 animals surviving up to 98 hr. White matter was involved in all. Ischaemic neuronal alterations, restricted to the striatum of one animal, were attributed to major circulatory complications. It was concluded that under these experimental conditions there is no evidence for hypoxic neuronal damage of purely histotoxic type.
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PMID:Cyanide intoxication in Macaca mulatta. Physiological and neuropathological aspects. 1 59

Sodium nitroprusside is an excellent agent for lowering blood pressure in hypertensive emergencies, for producing controlled hypotension during anesthesia, and for treating acute myocardial infarction and chronic heart failure. Toxic effects of this drug have been reported and above-normal cyanide and thiocyanate concentrations have been observed in the blood of a small proportion of subjects receiving nitroprusside. Nitrite, syanide, and thiocyanate are major decomposition products of nitroprusside, resulting from an in vitro reaction with human blood. On the basis of the conversion mechanism, we suggest that, in the cyanide/thiocyanate cycle, only cyanide is directly responsible for any acute toxicity attributed to sodium nitroprusside. In this work, the extent of cyanide production by erythrocytes in vitro was studied. The rate of detoxification of cyanide by human liver in vitro was experimentally determined and data from a search for a possible inhibitor of the nitroprusside/hemoglobin reaction are presented. Also, the possible mechanism of the nitroprusside/hemoglobin reaction is discussed.
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PMID:Some aspects of sodium nitroprusside reaction with human erythrocytes. 92 83

Sodium nitroprusside is a potent, effective, and readily reversible direct vasodilating agent. It is broken down by hemoglobin into cyanide, which is in part detoxified by liver and kidney to thiocyanate. Some cyanide, especially in nitroprusside- "resistant" individuals who need large amounts of the drug, appears to remain free to cause cyanide poisoning. Patients requiring inordinate amounts probably should not continue to receive the drug, although maximum dosage limits for long-term therapy are not established. Blood thiocyanate levels do not indicate the extent to which free cyanide is limiting oxygen utilization in essential tissue, nor do blood cyanide levels. Metabolic acidosis, elevated lactate levels, elevated lactate/pyruvate ratios, and elevated mixed venous blood oxygen content are at present the best indications of the presence of cyanide poisoning during nitroprusside administration. Nitroprusside appears useful for induction of hypotension during surgery, and for treatment of hypertensive emergencies from all causes, although continuance for more than a few days is probably unwise. The reductions of cardiac afterload and ventricular filling pressure by nitroprusside appear useful in treatment of severe myocardial failure or infarction, but studies of myocardial cyanide toxicity are needed before complete acceptance of this therapy is warranted. Initial dose rates between 0.5 and 1.5 mug/kg/min are recommended only as starting points for very careful titration. Total projected intra-operative dosage should be calculated as quickly as possible and should not exceed 3-3.5 mg/kg. It is hoped that future studies will reveal the maximum dose of nitroprusside that can safely be metabolized in a 24-hour period, and may indicate that cofactors of rhodanase such as thiosulfate, or cobalamins such as hydroxocobalamin, can be administered with nitroprusside to prevent cyanide poisoning.
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PMID:Sodium nitroprusside: pharmacology, toxicology and therapeutics. 96 81

From 1975 to 1993, our University Hospital performed 2789 graft procedures. During the same period, 12 poisoned, "brain-dead" patients were considered as organ donors. The toxic substances involved were: methaqualone (n = 1), benzodiazepine alone (n = 1), benzodiazepine plus tricyclic antidepressants (n =1), tricyclic antidepressants alone (n = 1), barbiturates (n = 2), insulin (n = 2), carbon monoxide (n = 1), cyanide (n = 1), methanol (n = 1), and acetaminophen (n = 1). From these intoxicated persons, 32 organ transplants were obtained, but only 23 could be followed for 1 month and only 20 for 1 year. The outcome at 1 month was favorable in 20 of the 23 patients. Two heart transplant patients died with 24h after grafting from stroke and acute heart failure, respectively. Preoperative hepatic encephalopathy was not corrected after grafting and was directly responsible for the death of a liver transplant patient. After 1 year, 15 of the 20 recipients were still alive. Chronic hepatic graft rejection led to a fatal outcome in one recipient and to second grafting in another. Finally, one recipient died from delayed neoplasia. Based on our experience, organ procurement may be considered in a few select cases of acute poisoning. Attention should, however, be drawn to possible graft damage due to some poisons.
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PMID:Outcome following organ removal from poisoned donors: experience with 12 cases and a review of the literature. 762 77

Experience with organ procurement from poisoned donors in brain death status is still limited in comparison with other etiologies. From 1963 to 1993, 2769 grafts (heart 141, kidney 1922, liver 623, pancreas 43) were performed in our University Hospital. Since 1975, among 1174 patients admitted to the ICU for acute poisoning, 12 patients who developed brain death status were considered for organ donation. The toxics involved were: methaqualone (1), benzodiazepines (1), benzodiazepines plus tricyclic antidepressants (2), barbiturates (2), insulin (2), carbon monoxide (1), cyanide (1), methanol (1), and acetaminophen (1). Exclusion criteria for organ removal were applied according to the nature of the toxin and the general criteria used for organ donation. The organs removed were: heart 5, heart valves for graft bank 2, kidneys 22, liver 4, pancreas 2, pancrease islet cells 2. Pertinent follow-up was obtained in 23 of 32 recipients. Immediate outcome was favorable in 20/23 patients (85%). Three patients died either from stroke, heart failure or preexisting encephalopathy. Two patients died from either chronic hepatic or renal graft rejection. None of these events could be directly related to a toxic origin. The one year survival rate of 75% is similar to that observed in the population who received organs from nonpoisoned donors. Organ procurement can be considered in few selected cases of acute poisoning. The accuracy of the diagnosis of irreversible brain damage is essential in this setting.
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PMID:Outcome following organ removal from poisoned donors in brain death status: a report of 12 cases and review of the literature. 852 98

The central integration of signals from pulmonary vagal C-fibers (or type-J receptors) with those arising from cardiac, peripheral chemoreceptor, and baroreceptor afferents to neurons within the nucleus of the solitary tract (NTS) was studied in an arterially perfused working heart-brain stem preparation of adult mouse. Pulmonary vagal C-fibers were excited by right atrial injection of phenylbiguanide (PBG) while cardiac receptors were stimulated by left ventricular injection of veratridine (1-3 micrograms/kg) or mechanically by distension of the left ventricle (20-50 microl perfusate) using an indwelling cannula. Carotid body chemoreceptors were activated by aortic injection of Na cyanide, whereas baroreceptors were stimulated by increasing arterial perfusion pressure. Stimulation of pulmonary C-fibers and cardiac, chemo-, and baroreceptors all produced a reflex bradycardia (23-133 bpm). Central respiratory activity, as recorded from the phrenic nerve, was depressed by stimulating pulmonary C-fibers and cardiac and baroreceptors but enhanced in amplitude and frequency during chemoreceptor stimulation. Twenty-seven NTS neurons were excited and three were inhibited after pulmonary C-fiber stimulation displaying decrementing discharges with a peak firing frequency of up to 42 Hz (15 +/- 2.2 Hz, mean +/- SE) that lasted for 8.8 +/- 0.9 s. These responses occurred <1 s from the end of the PBG injection that was within the pulmonary circulation time. None of these cells responded to increases in right atrial pressure. All cells excited by PBG were also driven synaptically after electrical stimulation of the ipsilateral cervical vagus nerve at a latency of 32.9 +/- 3.2 ms (range 20-62 ms). None of these neurons had ongoing activity related to central respiratory activity. Convergence from cardiorespiratory afferents to 21 neurons driven by pulmonary C-fibers was tested. Twenty-five percent of cells were selectively excited by chemical stimulation of cardiac receptors alone, 19% were driven by peripheral chemoreceptors, and 38% responded to both cardiac and chemoreceptor activation. In contrast, only 13% of the cells activated by PBG injection responded to stimulation of baroreceptors and only 6% to cardiac mechanoreceptor stimulation. None of these neurons were activated by increasing right atrial pressure. The data indicate a high proportion of afferent convergence from pulmonary C-fibers, cardiac receptors, and peripheral chemoreceptors in the NTS. However, these neurons appear not to integrate inputs from cardiovascular mechanoreceptors. The significance of the data is discussed in relation to pathological disease states such as pulmonary congestion and cardiac failure.
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PMID:Pattern of cardiorespiratory afferent convergence to solitary tract neurons driven by pulmonary vagal C-fiber stimulation in the mouse. 958 12

The mechanistic link between mitochondrial metabolism and inward rectifier K+ channel activity was investigated by studying the effects of a mitochondrial inhibitor, carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) on inward rectifiers of the Kir2 subfamily expressed in Xenopus oocytes, using two-electrode voltage-clamp, patch-clamp, and intracellular pH recording. FCCP inhibited Kir2.2 and Kir2.3 currents and decreased intracellular pH, but the pH change was too small to account for the inhibitory effect by itself. However, pre-incubation of oocytes with imidazole prevented both the pH decrease and the inhibition of Kir2.2 and Kir2.3 currents by FCCP. The pH dependence of Kir2.2 was shifted to higher pH in membrane patches from FCCP-treated oocytes compared to control oocytes. Therefore, the inhibition of Kir2.2 by FCCP may involve a combination of intracellular acidification and a shift in the intracellular pH dependence of these channels. To investigate the sensitivity of heteromeric channels to FCCP, we studied its effect on currents expressed by heteromeric tandem dimer constructs. While Kir2.1 homomeric channels were insensitive to FCCP, both Kir2.1-Kir2.2 and Kir2.1-Kir2.3 heterotetrameric channels were inhibited. These data support the notion that mitochondrial dysfunction causes inhibition of heteromeric inward rectifier K+ channels. The reduction of inward rectifier K+ channel activity observed in heart failure and ischemia may result from the mitochondrial dysfunction that occurs in these conditions.
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PMID:Regulation of inward rectifier K+ channels by shift of intracellular pH dependence. 1538 43

Metabolic inhibition (MI) contributes to contractile failure during cardiac ischemia and systolic heart failure, in part due to decreased excitation-contraction (E-C) coupling gain. To investigate the underlying mechanism, we studied subcellular Ca2+ release patterns in whole cell patch clamped rat ventricular myocytes using two-dimensional high-speed laser scanning confocal microscopy. In cells loaded with the Ca2+ buffer EGTA (5 mmol/L) and the fluorescent Ca2+-indicator fluo-3 (1 mmol/L), depolarization from -40 to 0 mV elicited a striped pattern of Ca2+ release. This pattern represents the simultaneous activation of multiple Ca2+ release sites along transverse-tubules. During inhibition of both oxidative and glycolytic metabolism using carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP, 50 nmol/L) and 2-deoxyglucose (2-DG, 10 mmol/L), there was a decrease in inward Ca2+ current (ICa), the spatially averaged Ca2+ transient, and E-C coupling gain, but no reduction in sarcoplasmic reticulum Ca2+ content. The striped pattern of subcellular Ca2+ release became fractured, or disappeared altogether, corresponding to a marked decrease in the area of the cell exhibiting organized Ca2+ release. There was no significant change in the intensity or kinetics of local Ca2+ release. The mechanism is not fully explained by dephosphorylation of L-type Ca2+ channels, because a similar degree of ICa"rundown" in control cells did NOT result in fracturing of the Ca2+ release pattern. We conclude that metabolic inhibition interferes with E-C coupling by (1) reducing trigger Ca2+, and (2) directly inhibiting sarcoplasmic reticulum Ca2+ release site open probability.
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PMID:Metabolic inhibition alters subcellular calcium release patterns in rat ventricular myocytes: implications for defective excitation-contraction coupling during cardiac ischemia and failure. 1571 1

Our previous study demonstrated a contribution of the paraventricular nucleus (PVN) of the hypothalamus in the processing of the carotid body (CB) chemoreflex. Nitric oxide (NO) (within the PVN), known to modulate autonomic function, is altered in rats with heart failure (HF). Therefore, the goal of the present study was to examine the influence of endogenous and exogenous NO within the PVN on the sympathoexcitatory component of the peripheral chemoreflex in normal and HF states. We measured mean arterial blood pressure, heart rate, renal sympathetic nerve activity (RSNA), and phrenic nerve activity (PNA) in sham-operated and HF rats (6-8 wk after coronary artery ligation) after incremental doses of potassium cyanide (25-100 mug/kg iv). There was potentiation of the reflex responses in HF compared with sham-operated rats. Bilateral microinjection of an inhibitor of NO synthase, N(G)-monomethyl-l-arginine (50 pmol), into the PVN augmented the RSNA and PNA response to peripheral chemoreceptor stimulation in sham-operated rats but had no effect in HF rats. Conversely, bilateral microinjection of a NO donor, sodium nitroprusside (50 nmol), into the PVN attenuated the RSNA response of the peripheral chemoreflex in sham-operated rats but to a smaller extent in HF rats. These data indicate that 1) NO within the PVN plays an important role in the processing of the CB chemoreflex and 2) there is an impairment of the NO function within the PVN of HF rats, which contributes to an augmented peripheral chemoreflex and subsequent elevation of sympathetic activity in HF.
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PMID:Altered nitric oxide mechanism within the paraventricular nucleus contributes to the augmented carotid body chemoreflex in heart failure. 1689 8

Most patients with acute heart failure present with increased left ventricular filling pressure and high or normal blood pressure; only a minority present with cardiogenic shock. In this context, therapy with vasodilators in the acute setting can improve both hemodynamics and symptoms. Vasodilators are usually given in conjunction with diuretics, although much of the acute effect of loop diuretics may be due to venodilation. Currently available agents include nitroglycerin, nitroprusside, and nesiritide. Nitroglycerin relieves pulmonary congestion primarily through direct venodilation, but may dilate coronary arteries and increase collateral blood flow at higher doses, an effect desirable in patients with ischemia. Tachyphylaxis may develop, necessitating incremental dosing. The major adverse effects of nitrates are hypotension and headache. Nitroprusside is a balanced arterial and venous vasodilator with a very short half-life, facilitating rapid titration. Afterload reduction lowers blood pressure and can increase stroke volume. The major complications of nitroprusside therapy are hypotension, and toxicity from accumulation of cyanide or thiocyanate, usually in patients with renal insufficiency treated for more than 24 h. Nesiritide, a recombinant form of human B-type natriuretic peptide (BNP), is a venous and arterial vasodilator that may also potentiate the effect of concomitant diuretics. Hypotension is the most common side effect. In addition, meta-analyses have suggested that nesiritide may worsen renal function and decrease survival at 30 days compared to conventional therapies. Resolution of these concerns awaits completion of appropriately powered prospective clinical trials. Angiotensin-converting enzyme (ACE) inhibitors have vasodilatory effects, but intravenous infusion of enalapril within 24 h of ischemic chest pain is not recommended. Oral ACE inhibition may be used to reduce afterload in other settings if blood pressure permits. Use of calcium antagonists in acute heart failure is not recommended.
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PMID:Vasodilators in acute heart failure. 1744 37


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