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Query: UMLS:C0042510 (ventricular fibrillation)
 10,091 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prognostic indices for survival after cardiopulmonary resuscitation (CPR) were investigated in 14 male Sprague-Dawley rats (500 +/- 50 g) and in 16 domestic pigs (25 +/- 4 kg). Arterial and venous blood gas and lactate measurements in association with the coronary perfusion pressure (CPP) and the end-expiratory CO2 concentration (ETCO2) were evaluated. Additional parameters in the porcine studies were coronary venous blood gas measurements and intramyocardial pH. Volume controlled ventilation was established and catheters were placed in the thoracic aorta and in the right atrium in both animal species. Additionally in the pigs, the pulmonary artery and the great cardiac vein were catheterized and intramyocardial pH was measured with a glass pH electrode placed in the diaphragmatic left ventricular myocardium. Ventricular fibrillation was induced with a direct current and external chest compression was initiated after four minutes in the rats and after three minutes in the pigs. Transthoracic DC defibrillation was attempted with 10J after two minutes of compression in the rats and with 300J after eight minutes of compression in the pigs. Eight of 14 rats and eight of 16 pigs were successfully resuscitated. Significant veno-arterial gradients for pH and pCO2 but not for lactate were observed during CPR in both animal species. With the exception of arterial pH in the pigs (p less than 0.05), neither arterial nor venous blood gas measurements nor intramyocardial pH separated resuscitated from non-resuscitated animals. However, CPP and ETCO2 significantly separated resuscitated from non-resuscitated animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Determinants of survival in cardiopulmonary resuscitation]. 211 83

The relative myocardial irritant properties of halothane, isoflurane, and pentobarbital were evaluated in chickens. Sixteen adult male broiler chickens were randomly assigned to 1 of 3 groups: group-1 chickens were anesthetized with pentobarbital (30 mg/kg, IV), group-2 chickens were anesthetized with halothane (end tidal halothane 1.2%), and group-3 chickens were anesthetized with isoflurane (end tidal isoflurane 2.1%). Birds in any 2 of the 3 treatment groups were tested on any 1 day. Local anesthesia was induced, and blood pressure, heart rate, ECG, and blood gas variables were measured before general anesthesia was induced. Positive-pressure ventilation with an inspired O2 fraction greater than 0.95 was adjusted to result in an end tidal CO2 concentration that reflected a Paco2 similar to that obtained prior to anesthesia and ventilation. All measurements were repeated. The threshold for ventricular fibrillation in response to electrical stimulation of the heart was then determined for all birds. Effects of anesthesia on hemodynamic and blood gas variables were similar in all 3 groups. Compared with halothane or pentobarbital, isoflurane anesthesia resulted in a significantly (P less than 0.05) lower threshold for electrical fibrillation of the heart.
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PMID:Effect of halothane, isoflurane, and pentobarbital anesthesia on myocardial irritability in chickens. 233 73

Previous studies from our institution demonstrated significant hypercarbic acidosis in the mixed venous (pulmonary artery) blood in animals and human patients during cardiac arrest and cardiopulmonary resuscitation (CPR). In the present study, the acid-base state of the myocardium during cardiac arrest was investigated. Cardiac arrest was electrically induced in 11 pentobarbital-anesthetized and mechanically ventilated domestic pigs. Precordial compression was begun 3 minutes after onset of ventricular fibrillation and continued for 8 minutes. During CPR, there was rapid onset of profound myocardial acidosis with an increase in intramyocardial [H+] from 54 +/- 5 to 146 +/- 20 nmol/l (7.27 +/- 0.04 to 6.88 +/- 0.20 pH units). Great cardiac vein PCO2 increased from 57 +/- 2 to 158 +/- 12 mm Hg. Profound hypercarbic acidosis in great cardiac vein blood was associated with myocardial lactate production to levels of 8.1 +/- 0.7 mmol/l. Only moderate decreases in cardiac vein bicarbonate concentrations from 31 +/- 1 to 23 +/- 1 mmol/l were observed. These acid-base changes were almost completely reversed over an interval of 60 minutes after the animals were successfully resuscitated by DC countershock. The PCO2 in cardiac vein blood was significantly greater than that of mixed venous blood, demonstrating disproportionate myocardial production of CO2 during CPR. Accordingly, it is CO2 production during ischemia that is implicated as the predominant mechanism accounting for myocardial [H+] increases during cardiac arrest. Important clinical implications for buffer therapy during CPR and, in particular, treatment with bicarbonate emerge from these observations.
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PMID:Myocardial acidosis associated with CO2 production during cardiac arrest and resuscitation. 250 12

There is controversy regarding the use of alkalinizing agents during reperfusion after cardiac arrest. The potential deleterious effects of sodium bicarbonate (bicarb) administration, including paradoxic cerebral acidosis, have led to the search for alternative agents. Tromethamine (tris) is a non-CO2-generating buffer that has been proposed for use during cardiopulmonary resuscitation. The purpose of this experiment was to compare the ability of tris with bicarb to correct brain pH (pH B) during reperfusion after a 12-minute cardiac arrest. Adult mongrel dogs were instrumented and placed in the bore of a Bruker Biospec 1.89 tesla superconducting magnet system. Ventricular fibrillation was induced; after 12 minutes, cardiopulmonary bypass was initiated and maintained for two hours with minimum flows of 80 mL/kg/min. Bicarb (n = 5) or tris (n = 5) were administered to correct arterial pH as rapidly as possible. 31P NMR spectra were obtained at baseline and throughout ischemia and reperfusion. The pH B was determined with the inorganic phosphate relative to the phosphocreatine resonance signal shift. Profile analysis indicates a difference between groups (P less than .02) related to an initial delay in pH B correction in the tris group. By 48 minutes of reperfusion, pH B did not differ between the groups. Moreover, there was no evidence of paradoxic cerebral acidosis in the bicarb group. Although tris corrects blood pH as quickly as bicarb, it is less effective in correcting pH B. Absence of paradoxic acidosis may be caused by efficient elimination of CO2 by cardiopulmonary bypass.
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PMID:The effect of CO2 and non-CO2-generating buffers on cerebral acidosis after cardiac arrest: A 31P NMR study. 253 65

One minute following electrically induced ventricular fibrillation, 12 anaesthetized pigs (hybrids between German and Belgian pedigree swine of 29 kg average body weight) were resuscitated for 30 min with a mechanical thorax compressor and ventilator. Six animals were given 1 mval sodium bicarbonate per kilogram body weight via a central venous line during the first ten minutes of resuscitation, and then 0.5 mval/kg body weight during both of the remaining ten minute intervals. The remaining 6 animals served as control group. In the control group constant volume ventilation led to a fall in the arterial partial pressure of CO2 because perfusion was diminished in relation to ventilation and despite the slowly developing metabolic acidosis this initially led to an increase in pH. At the end of the period of observation an arterial base deficit of 10 mmol/l was measured. Infusion of sodium bicarbonate led to a metabolic alkalosis and to an arterial base excess which at 10 min reached a maximum value of 13.8 mmol/l. In the bicarbonate group serum osmolality rose as a result of the sodium application from 293-334 mosm/l. In contrast, the osmolality of the control group only rose to 309 mosm/l.
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PMID:[Sodium bicarbonate administration in cardiopulmonary resuscitation. Results of an animal experimental study]. 298 85

End-tidal CO2 concentration (ETCO2) may serve as a simple noninvasive measurement of the blood flow generated by precordial compression during cardiopulmonary resuscitation (CPR). In a mechanically ventilated porcine preparation of ventricular fibrillation, onset of fibrillation was associated with a rapid decrease in ETCO2 from 4.0 +/- 0.2% to less than 0.7 +/- 0.2%. With precordial compression, it increased to 1.9 +/- 0.3%. Animals that were successfully defibrillated after 12 min of CPR demonstrated an immediate increase in ETCO2. The ETCO2 increased from 1.9 +/- 0.3% to 4.9 +/- 0.3% over an interval of between 30 and 60 sec. These changes in ETCO2 were closely related to proportionally similar decreases and increases in cardiac output (CO), and a close correlation between ETCO2 and CO was demonstrated (r = .92). A similar highly significant correlation between ETCO2 and CO was also demonstrated during open-chest cardiac massage (r = .95). ETCO2 therefore serves as a noninvasive measure of pulmonary blood flow and therefore CO. In 17 successfully resuscitated animals. ETCO2 during precordial compression averaged 1.7 +/- 0.2%, whereas it was only 0.5 +/- 0.1% in five animals in whom resuscitation procedures were unsuccessful (p less than .001). Accordingly, ETCO2 prognosticates outcome during CPR and immediately identifies restoration of spontaneous circulation.
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PMID:Expired carbon dioxide: a noninvasive monitor of cardiopulmonary resuscitation. 312 Dec 9

A standardized method of cardiopulmonary resuscitation in rodents has been developed for anesthetized, mechanically ventilated rats. Ventricular fibrillation was induced and maintained by an alternating current delivered to the right ventricular endocardium. After 4 min of ventricular fibrillation, the chest was compressed with a pneumatic piston device. Eight of 14 animals were successfully resuscitated with DC countershock after 6 min of cardiac arrest. In confirmation of earlier studies from our laboratories in dogs, pigs, and human patients, this rodent model of cardiopulmonary resuscitation demonstrated large venoarterial [H+] and PCO2 gradients associated with reduced pulmonary excretion of CO2 during the low-flow state. Mean aortic pressure, coronary perfusion pressure, and end-tidal CO2 during chest compression were predictive of successful resuscitation.
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PMID:Cardiopulmonary resuscitation in the rat. 314 35

The authors report that total cardiopulmonary bypass (CPBP) for severe heart failure can be safely maintained for several days through peripheral cannulation alone. In two healthy sheep under general anesthesia, the authors cannulated the right external jugular vein and the right subclavian artery. A special spring was attached to a 7F Swan-Ganz catheter and positioned at the level of the pulmonary artery (PA) valve, rendering it partially incompetent. The extracorporeal circuit included a venous reservoir, a roller pump, a membrane lung, and a blood pulsator set at 25 beats/min. Ventricular fibrillation was induced with 110 VAC. Extracorporeal blood flow was raised to 100-120 ml/kg min. Mechanical pulmonary ventilation was changed to 5% CO2 in room air. During bypass, the wedge pressure (WP) averaged 9-13 mmHg, PA pressure 7-13 mmHg, and central venous pressure 1-9 mmHg. After 38 and 48 hr respectively the hearts were defibrillated with DC shock. There was total heart failure with no ejection from right or left. We continued with TCPBP. The right heart recovered after 1 and 3 hr respectively. After 7 and 5 hr, respectively, there was some aortic ejection. By 11 and 4 hr, respectively, the sheep were off bypass and on room air, with return to baseline cardiac function. Throughout the recovery the WP averaged 4-8 mmHg. At autopsy, all hearts were soft and normal in appearance. Histologic examination of the lungs and the heart was unremarkable. The authors conclude that the PA spring readily decompressed the LV. Ventilating lungs with 5% CO2 in air during CPBP sustained excellent lung function.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Long-term closed chest partial and total cardiopulmonary bypass by peripheral cannulation for severe right and/or left ventricular failure, including ventricular fibrillation. The use of a percutaneous spring in the pulmonary artery position to decompress the left heart. 319 50

The determinants of reperfusion arrhythmias were investigated in 63 open-chest dogs undergoing a 25-minute coronary artery occlusion followed by reperfusion. Heart rate correlated positively with the occurrence of reperfusion ventricular tachycardia (VT) and ventricular fibrillation (VF). Collateral flow during ischemia (radioactive microspheres) exhibited a strong negative correlation with the incidence of both VT and VF upon reperfusion. Importantly, a sensitive coupling was present, whereby small differences in flow were associated with large differences in rhythm disorders. The rise in intramyocardial CO2 tension (another index of severity of ischemia) was greater in dogs exhibiting reperfusion VT (p less than 0.001) and VF (p less than 0.08); however, this variable was significantly correlated with collateral flow (r = -0.57, p less than 0.01). The size of the occluded coronary bed, determined by postmortem perfusion, was not consistently related to VT; within a given range of occluded bed sizes, the incidence of VT was inversely related to collateral flow. Thus, reperfusion-induced VT is relatively independent of the size of the occluded bed, and is determined primarily by the degree of myocardial hypoperfusion. In contrast, VF did not develop with occluded beds less than 25% of the left ventricular mass; above this critical occluded bed size, its incidence was inversely related to collateral perfusion. Reperfusion VF is therefore determined by the association of a large occluded bed with a poor collateral flow. This study identifies and systematically analyzes three major determinants of reperfusion arrhythmias: (1) the severity of antecedent ischemia, estimated either from the degree of flow reduction or the rise in intramural CO2 tension; (2) the amount of ischemic/reperfused myocardium; and (3) the heart rate. In addition to conceptual interest and clinical implications, the findings have important implications for the design of future studies aimed at evaluating antiarrhythmic interventions in experimental models.
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PMID:Factors that determine the occurrence of reperfusion arrhythmias. 333 79

Twenty-six healthy mixed-breed dogs (25 to 35 kg) underwent hypothermic (27 C) cardiopulmonary bypass. The heart was arrested with cold (4 C) cardioplegic solution, and left ventriculostomy performed. Postoperative mortality was 11.5% (3/26). Two deaths were attributable to ventricular fibrillation the night after surgery, and one death 2 weeks later was the result of pulmonary embolization. All other dogs recovered promptly and were well at follow-up evaluation 6 weeks later. The most important considerations were (1) the surgical approach, ie, combining left lateral thoracotomy with cannulation of the right atrium and left femoral artery for cardiopulmonary bypass (CPB) (avoiding median sternotomy and aortic arch perfusion), (2) the adherence to strict criteria for CPB perfusion, consisting of blood flow of at least 2.2 L/m2/min, PCV no less than 25%, gas flow through the oxygenator (97% O2, 3% CO2) of at least 3.5 L/min, maintenance of a mean arterial blood pressure greater than 60 mm of Hg, and heparinization to maintain activated clotting time over 480 seconds, (3) the use of dipyridamole infusion to preserve platelets during CPB, resulting in decreased postoperative blood loss and (4) the monitoring of cardiac, respiratory, renal, and neurologic functions before, during, and after the operation, with particular emphasis on fluid balance and electrolytes. We concluded that a high success rate is possible for open-heart surgery in the dog requiring cardiopulmonary bypass, but only through meticulous surgical technique and the combined application of many monitoring techniques, with timely intervention to correct serious departures from homeostasis.
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PMID:Technique and postoperative management for successful cardiopulmonary bypass and open-heart surgery in dogs. 357 Sep 42


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