Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0042510 (ventricular fibrillation)
 10,091 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anoxia has been compared with ischaemia. The abrupt restoration of either oxygen of flow may accelerate cardiac damage. Anoxic stimulation of glycolysis (Pasteur effect) is inhibited during ischaemia by lactate and proton accumulation at the levels of phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase. Anaerobic glycolysis provides lactate and ATP; breakdown of the latter provides protons. During partial respiration thought to occur in partial ischaemia, continued production of CO2 is a factor contributing to intracellular acidosis; mitochondrial ATP when formed by continued respiration also yields protons when ultimately broken down. The endoproducts of aerobic glycolysis (pyruvate and NADH) are transported into the mitochondria by the malate-aspartate cycle and by pyruvate dehydrogenase activity. Adenine nucleotide transferase activity normally transfers the mitochondrially-made ATP to the cytoplasm, but acyl CoA accumulates in ischaemia (or during perfusions with high circulating free fatty acids) to inhibit the transferase. The mitochondrial creatine kinase is thought to transform ATP transported outwards into creatine phosphate which can permeate the outer mitochondrial membrane. Further compartmentation of ATP may be by other creatine kinase isoenzymes or in relation to the cell membrane. The glycogenolytic-sarcoplasmic reticulum complex links a glycogen pool to the sarcoplasmic reticulum. Cyclic AMP may regulate admission of calcium to the cell during the plateau of the action potential and promote calcium uptake by the sarcoplasmic reticulum by phosphorylation of phospholamban. The latter promotes the activity of the calcium-transport ATPase. Calcium and cyclic AMP may also interact at the level of the contractile proteins where cyclic AMP phosphrylates troponin. Cyclic GMP generally has opposite effects to cyclic AMP and undergoes opposite changes in the frog cardiac cycle to those of cyclic AMP. A present it is reasonable to suppose that physiological effects of adrenaline or of cholinergic agents on the myocardium are mediated by cyclic AMP or cyclic GMP, respectively, but this hypothesis still lacks firm support. There is an association between tissue cyclic AMP and ventricular fibrillation after coronary ligation, and direct evidence for a role of cyclic AMP in promoting arrhythmias has been obtained by studies on the ventricular fibrillation threshold in the rat heart. However, there are other mechanisms, involving first the effects of substrates on the action potential duration, and secondly, the fast channel, which can also give rise to the development of malignant arrhythmias.
 ...
PMID:Myocardial metabolism and heart disease. 3 41

Cardiac arrhythmias have frequently been reported in association with respiratory failure. The possible additive role of pharmacologic agents in precipitating cardiac disturbances in patients with respiratory failure has only recently been emphasized. The effects of aminophylline on the ventricular fibrillation threshold during normal acid-base conditions and during respiratory failure were studied in anesthetized open chest dogs. The ventricular fibrillation threshold was measured by passing a gated train of 12 constant current pulses through the ventricular myocardium during the vulnerable period of the cardiac cycle. During the infusion of aminophylline, the ventricular fibrillation threshold was reduced by 30 to 40 percent of the control when pH and partial pressures of oxygen (PO2) and carbon dioxide (CO2) were kept within normal limits. When respiratory failure was produced by hypoventilation (pH 7.05 to 7.25; PC02 70 to 100 mm Hg: P02 20 to 40 mm Hg), infusion of aminophylline resulted in an even greater decrease in ventricular fibrillation threshold to 60 percent of the control level. These experiments suggest that although many factors may contribute to the increased incidence of ventricular arrhythmias in respiratory failure, pharmacologic agents, particularly aminophylline, may play a significant role.
 ...
PMID:Effects of aminophylline on the threshold for initiating ventricular fibrillation during respiratory failure. 23 69

The effects of Forane anesthesia for deep surface hypothermia with 30 minutes of total circulatory occlusion were evaluated. With 100% O2 6 of 7 dogs developed motor disorders postoperatively, while 3 of 5 with 98% O2/2% CO2 and none with 95% O2/5% CO2 developed motor disorders. Cooling was uneventful except for 1 episode of ventricular fibrillation in the 5% CO2 group at 23 degrees C. Resuscitation was easy, but the early rewarming period was characterized by repeated episodes of ventricular fibrillation and delayed recovery of cardiac function, especially in the 100% O2 group. Blood lactate levels remained low during cooling and gradually increased during rewarming in all groups, with the highest levels in the 100% O2 group and the lowest in the 5% CO2 group. It is concluded that Forane can be used for surface hypothermia with 30 minutes' circulatory occlusion when administered in 95% O2/5% CO2. A Comparison of these results with previously reported series indicates that Forane is inferior to ether but may be superior to halothane for surface hypothermia.
 ...
PMID:The use of Forane anesthesia for surface-induced deep hypothermia. 24 Mar 30

The experiments were carried out in 33 dogs 60 min. to 12 hours after cardiac arrest was induced for 3-5 min by ventricular fibrillation. In 11 dogs closed chest cardiac massage was performed 30 min. and in 222 dogs defibrillation was used to restore heart function. The pulmonary and peripheral circulation was assessed on the basis of changes in arterial and venous blood pressure, cardiac output, vascular resistance, pulmonary shunting and capnographic determinations. The values of VA, VA/Vmin, V/Q, VDph, VD/VT, DuO2 and DuCO2, Pa-E'CO2, PaO2 were determined. Measurements of acid base balance, lactate and pyruvate levels and certain elements of blood clotting and fibrinolysis systems were performed. Moreover, lung biopsy was examined by light and electron microscopes. Functional determinations confirmed the presence of disturbances of lung perfusion and alveolar ventilation as well as disturbances in oxygen exchange at cellular level. The author suggests the term Resuscitation Lung Syndrome for these disturbances.
 ...
PMID:Certain parameters of pulmonary circulation dynamics and gas exchange in the lungs and morphotic changes in lung tissue in dogs during cardiac arrest and immediately after resuscitation. 102 72

The influence of halothane, ether, carbon dioxide, and perfusion rewarming on the electrocardiogram was studied in 37 dogs subjected to surface-induced deep hypothermia. Significant anesthetic-related differences in P-R, QRS, Q-T and R-R intervals during cooling were not apparent; however, reduced arterial pressure, ventricular fibrillation, and a greater tendency for bradycardia requiring supportive measures were noted at low temperatures with halothane anesthesia. The use of 95% O2/5% CO2 significantly reduced the QTc at low temperatures; Other phenomena, including the occurrence and significance of J waves, are discussed. The relationship of the electrocardiogram to clinical and pathological results was evaluated and indicates that (1) properly managed resuscitation (manual massage and defibrillation) is not a serious hazard, (2) ether in 100% oxygen is the agent of choice for surface-induced deep hypothermia with prolonged circulatory arrest, and (3) halothane may be used in a procedure combining surface cooling and perfusion rewarming if given in a mixture of oxygen and carbon dioxide.
 ...
PMID:Electrocardiographic changes during surface-induced deep hypothermia. The influence of ether, halothane, carbon dioxide, and perfusion rewarming. 112 62

1. The ventricular fibrillation threshold (VFT) was measured in the isolated heart of the rabbit perfused via the aorta with McEwen's solution at 37 degrees C by applying a single 10 ms pulse of current during the vulnerable period of late systole. The arrhythmia induced was either fibrillation or a rapid tachycardia. 2. Gassing the McEwen's solution with 5% CO2 in N2 (anoxia) instead of with carbogen caused a negative inotropic and chronotropic effect and significantly lowered the VFT. Although anoxia releases noradrenaline from the heart the effect of anoxia on the VFT was not prevented by beta-adrenoceptor blockade with propranolol or pindolol or by previous treatment with reserpine. 3. Perfusion with adenosine (5 muM) which is released from the heart muscle by anoxia, or with dipyridamole (10 muM) which protects the adenosine from binding or destruction by the tissues, or with both combined failed to alter the VFT significantly. Furthermore neither adenosine nor dipyridamole significantly altered the effect of anoxia on the VFT. 4. Anoxia, adenosine and dipyridamole significantly increased the duration of the induced arrhythmia when compared with that of the controls. 5. Anoxia and adenosine significantly shortened the vulnerable time, i.e., the minimal time after the R-wave of the ECG at which the pulse had to be applied to induce the arrhythmia. 6. Perfusion with the McEwen's solution gassed with 5% CO2 in air (hypoxia) significantly lowered the VFT but the effect was not as great as with anoxia. Isoprenaline when infused lowered the VFT but this effect was not potentiated by hypoxia. 7. The results indicate that (a) anoxia lowers the VFT in the perfused isolated heart of the rabbit and that this effect is not due to adenosine or noradrenaline released by the anoxia and (b) hypoxia does not sensitize the heart to the arrhythmic effect of isoprenaline.
 ...
PMID:The effect of anoxia on the ventricular fibrillation threshold in the rabbit isolated heart. 117 59

Nineteen anaesthetized piglets were investigated. After catheterization and a stabilization period, ventricular fibrillation was induced with a transthoracic DC shock, after which a 10-min period of cardiopulmonary resuscitation (CPR) took place. CPR included manual chest compression and mechanical ventilation with pure oxygen. After 1 min of CPR, an infusion of alkaline buffer was begun and completed within 5 min. A total of 50 mmol of either sodium bicarbonate (n = 6) or tris buffer mixture (n = 7) were given. These two groups were compared with a third control group (n = 6) receiving the same volume of normal saline. After 8 min of CPR all animals were given 0.5 mg adrenaline i.v., and after 10 min DC shocks were used to revert the heart back to normal sinus rhythm. Our results demonstrate that blood flow and not ventilation is the limiting factor for the efficient disposal of CO2 during CPR. This also applied when the demand for CO2 transport was increased by administration of sodium bicarbonate. The respiratory exchange ratio increased 1.9-fold, indicating that the transport of carbon dioxide was less affected than that of oxygen. The estimated alveolo-arterial oxygen tension difference, shunt, and overall ventilation/perfusion ratio increased, creating an inverse hyperbolic relationship between arterial PCO2 and PO2. The difference between mixed venous and arterial PCO2 correlated well to the mixed venous PCO2, implying more efficient pulmonary elimination of PCO2 when the mixed venous PCO2 was high. Pulmonary gas exchange during CPR appears to be independent of alkaline buffer therapy in the form of sodium bicarbonate or tris buffer mixture.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Gas exchange as monitored in mixed venous and arterial blood during experimental cardiopulmonary resuscitation. 163 65

Since the last revision of the American Heart Association's guidelines in 1985, several new developments of clinical importance have occurred in the field of cardiopulmonary resuscitation. These include enhanced access to and earlier use of defibrillation, the use of high-dose epinephrine when standard doses fail, the assessment of resuscitative efforts with end-tidal CO2 monitoring and the addition of two new drugs, amiodarone (for refractory ventricular fibrillation) and adenosine (for paroxysmal supraventricular tachycardia). Time will determine the ultimate role of these advancements in the management of cardiac arrest.
 ...
PMID:New developments in cardiopulmonary resuscitation. 200 Jul 28

Capnography is a valuable tool in the management of cardiac arrest, since end-tidal CO2 (PetCO2) correlates well with cardiac output and there are no other suitable noninvasive ways to measure this important variable during resuscitation. Animal studies also suggest that PetCO2 correlates well with the likelihood of resuscitation, but this has never been confirmed in humans. We prospectively studied 55 adult, nontraumatic prehospital cardiac arrest patients. PetCO2 was monitored with an in-line sensor on arrival in the ED and throughout the arrest, which was managed by the usual advanced cardiac life-support treatment guidelines. Chest compression was carried out mechanically. Patients were assessed for return of spontaneous pulse as evidence of initial resuscitation; hospital discharge and long-term survival were not examined. Fourteen patients developed spontaneous pulses and were resuscitated, and 41 were not. The length and aggressiveness of treatment and CPR were not different between the two groups, nor were there differences in down time, resuscitation time, or other factors known to affect outcome. Patients who developed a pulse had a mean PetCO2 of 19 +/- 14 (SD) torr at the start of resuscitation, and those who did not had a mean PetCO2 of 5 +/- 4 torr (p less than .0001). This difference was significant both in nonperfusing rhythms (asystole and ventricular fibrillation) and in potentially perfusing rhythms (electromechanical dissociation). An initial PetCO2 of 15 torr correctly predicted eventual return of pulse with a sensitivity of 71%, a specificity of 98%, a positive predictive value of 91%, and a negative predictive value of 91%. A receiver operating curve was generated for sensitivity and specificity of the test at varying PetCO2 thresholds.
 ...
PMID:Prediction of outcome of cardiopulmonary resuscitation from end-tidal carbon dioxide concentration. 210 6

We investigated the aortic, mixed venous, and great cardiac vein acid-base changes in eight domestic pigs during cardiac arrest produced by ventricular fibrillation and during cardiopulmonary resuscitation (CPR). The great cardiac vein PCO2 increased from a control value of 52 +/- 2 to 132 +/- 28 (SD) Torr during CPR, whereas the arterial PCO2 was unchanged (39 +/- 4 vs. 38 +/- 4). The coronary venoarterial PCO2 gradient, therefore, increased remarkably from 13 +/- 2 to 94 +/- 29 Torr. The simultaneously measured great cardiac vein lactate concentrations increased from 0.24 +/- 0.06 to 7.3 +/- 2.34 mmol/l. Much more moderate increases in the lactate content of aortic blood from 0.64 +/- 0.25 to 2.56 +/- 0.27 mmol/l were observed. Increases in great cardiac vein PCO2 and lactate were highly correlated during CPR (r = 0.91). After successful CPR, the coronary venoarterial PCO2 gradient returned to normal levels within 2 min after restoration of spontaneous circulation. Lactate content was rapidly reduced and lactate extraction was reestablished within 30 min after CPR. These studies demonstrate marked but reversible acidosis predominantly as the result of myocardial CO2 production during CPR.
 ...
PMID:Increases in coronary vein CO2 during cardiac resuscitation. 211 25


1 2 3 4 5 Next >>