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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Use of continuous transtracheal oxygen delivery systems combined with rhythmic chest compressions can provide excellent oxygenation and ventilation during cardiopulmonary resuscitation. However, occasional displacement of the transtracheal catheter results in life-threatening pneumomediastinal complications. We investigated using the pharyngeal lumen of a pharyngeal-tracheal lumened airway (PtL) as an alternative delivery system for continuous oxygen flow in 21 large mongrel dogs. Excellent ventilation was possible in anesthetized, apneic, and paralyzed dogs in normal sinus rhythm from the "bellows" effect of chest compressions. The hypercapnia and respiratory acidemia resulting from 5 min of complete apnea in ten dogs during normal sinus rhythm was readily corrected (p less than 0.01). In an additional 11 dogs, external chest compressions were performed and oxygen was delivered continuously via the PtL during 20 min of ventricular fibrillation. During this period of cardiac arrest, pH declined (7.38 +/- 0.01 vs 7.19 +/- 0.02; p less than 0.01), but PaCO2 (35 +/- 1 vs 38 +/- 3 mm Hg) and PaO2 (67 +/- 2 vs 68 +/- 3 mm Hg) were not significantly different from prearrest values. Successful resuscitation was achieved in 8 of 11 (73 percent) animals, which is similar to the results in historical controls with endotracheal intubation. No pneumomediastinal complications were seen with use of the PtL. We conclude that using the pharyngeal lumen of the PtL for continuous delivery of oxygen combined with external chest compressions can provide a safe and effective mode of oxygenation and ventilation during cardiac arrest.
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PMID:Oxygenation and ventilation during cardiopulmonary resuscitation utilizing continuous oxygen delivery via a modified pharyngeal-tracheal lumened airway. 173 83

In order to minimize heat loss cold stress induces peripheral vasoconstriction via the sympathetic nervous system. This effect is most pronounced in the extremities. Vasoconstriction does not appear in the head-neck region--a fact of great importance in emergency situations. In order to compensate for heat loss shivering is an early event, where involuntary muscle contractions increase metabolic rate 2-6 fold. Early tachycardia and elevated blood-pressure, followed by progressive bradycardia and lowered pressure are common cardiovascular effects of hypothermia. Death due to ventricular fibrillation or asystole occurs between 28 degrees-25 degrees C. Cold stress causes an osmolal diuresis with sodium and chloride as the main constituents. The natriuresis is of tubular origin and could be due to impaired autoregulation in the kidney and/or depend on the natriuretic polypeptide. The augmented urine flow decreases blood volume, lowers physical working capacity and increases blood viscosity--all negative events in a hazardous situation. Sudden immersion initiates hyperventilation for 1-2 minutes with an increasing risk of drowning. Thereafter ventilation decreases to rates consistent with metabolic requirements. In severe hypothermia carbon dioxide retention causes respiratory and metabolic acidosis. Hypothermia induces progressive depression of mental functions starting with apathy and bizarre behaviour and ending in lethargy and coma often between 30 degrees-28 degrees C. The paradoxal feeling of heat with undressing in agony could depend on cerebral receptor disturbances.
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PMID:Human physiology under cold exposure. 181 74

We examined the efficiency of continuous transtracheal O2 insufflation (TOI) as a method of ventilation during cardiopulmonary resuscitation (CPR) in a canine model. The tip of the insufflation catheter was placed 1 cm above the carina. The effects of TOI at flow rates of 0.2, 0.5, and 1.0 l/kg per min during and after CPR were examined in dogs with induced ventricular fibrillation. During CPR, adequate oxygenation and ventilation were maintained with TOI at flow rates of 0.5 and 1.0 l/kg per min, but not at 0.2 l/kg per min. After CPR, TOI was adequate to maintain oxygenation, but not ventilation. TOI alone did not prevent post-CPR hypercarbia in successfully resuscitated animals. Still, this study suggests that TOI might be useful as a temporary measure for emergency ventilation during CPR, especially in situations such as upper airway abnormalities, when mask ventilation or endotracheal intubation is not feasible.
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PMID:Transtracheal O2 insufflation (TOI) as an alternative method of ventilation during cardiopulmonary resuscitation. 196 48

During cardiopulmonary resuscitation (CPR), arterial pH and carbon dioxide tension (PCO2) do not reflect the marked acidosis and hypercapnia seen in venous blood samples during CPR. Epinephrine causes an increase in myocardial and cerebral blood flow during CPR, but the influence on regional venous PCO2 and pH is as yet unknown. Fourteen pigs were allocated to receive either 0.9% saline (n = 7), or 45 micrograms/kg epinephrine (n = 7) after 5 min of ventricular fibrillation and 3 min of open-chest CPR. Blood samples were obtained during CPR from the aorta, pulmonary artery, great cardiac vein, and sagittal sinus before and 90 s and 5 min after drug administration. Regional blood flow was measured with tracer microspheres. Plasma catecholamines were quantified by high-performance liquid chromatography in arterial blood. PCO2 90 s after drug administration in arterial, mixed venous, myocardial venous, and cerebral venous blood were (means +/- SD) 36 +/- 8, 67 +/- 9, 74 +/- 14, and 79 +/- 19 mmHg in the control group and 35 +/- 11, 62 +/- 12, 73 +/- 10, and 71 +/- 14 mmHg in the epinephrine group. pH values 90 s after drug administration in the same blood samples were 7.29 +/- 0.11, 7.11 +/- 0.09, 7.04 +/- 0.09, and 7.07 +/- 0.10 in the control group and 7.31 +/- 0.13, 7.17 +/- 0.07, 7.08 +/- 0.08, and 7.07 +/- 0.12 in the epinephrine group. Despite a significant increase in myocardial and cerebral blood flow after epinephrine, PCO2 and pH in all blood samples were not different from those of the control group. (ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of epinephrine on systemic, myocardial, and cerebral acid-base status during cardiopulmonary resuscitation. 199 Sep 8

Adequate oxygenation of apneic subjects can be maintained by constant flow transtracheal oxygen (TTO), but this method alone is associated with hypercapnia. The "bellows" effect of external chest compressions (ECC) might prevent this problem if the airway were kept open by TTO. In dogs, we investigated the utility of TTO delivered at 15 L/min by a percutaneously placed intratracheal catheter, plus ECC (TTO/ECC) as an alternative method of ventilation during CPR. TTO was applied to anesthetized, paralyzed dogs in normal sinus rhythm (NSR) at various rates of ECC and during ventricular fibrillation (VF) at an ECC rate of 80/min. During NSR and VF, hypercapnia did not develop and arterial oxygen saturations were maintained above 90 percent. During NSR, the PaCO2 decreased and the pH increased as the ECC rate increased. For many of the animals, coronary perfusion pressure remained above 20 mm Hg during VF, suggesting that these animals could be resuscitated to NSR. In another phase, after 15 min of VF using TTO/ECC, seven of nine animals were defibrillated. We conclude that ventilatory and hemodynamic support adequate to permit successful resuscitation to NSR is provided by the combination of TTO/ECC to apneic dogs during VF.
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PMID:Continuous transtracheal oxygen delivery during cardiopulmonary resuscitation. An alternative method of ventilation in a canine model. 249 66

Hyperventilation therapy is often recommended after an episode of global cerebral ischemia (cardiac arrest), even though several workers have shown that under such circumstances the cerebral vasculature is unresponsive to changing PaCO2. However, no study has examined the effects of prolonged PaCO2 changes. We therefore studied the cerebrovascular effects of a 3-h period of continuous hypercarbia (40 to 45 torr) or hypocarbia (15 to 20 torr) in cats resuscitated from 12 min of electrically induced ventricular fibrillation. There were no differences in postresuscitation cerebral blood flow (CBF) or EEG, but intracranial pressure was lower in the hypocapnic animals. Furthermore, hypocapnic cats retained some CBF responsiveness to varying PaCO2 levels, while no such response was noted in previously hypercapnic animals. These findings suggest that some measurable changes in postarrest cerebrovascular behavior can result from prolonged hypocapnia (possibly related to tissue pH alterations). Whether such changes will have clinical utility is unclear.
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PMID:Cerebrovascular effects of prolonged hypocarbia and hypercarbia after experimental global ischemia in cats. 392 54

Five Merino sheep were dosed 3 g/kg of dry, finely-milled Homeria glauca (Natal yellow tulp) plant material. An electrocardiogram was recorded and the arterial and central venous blood pressure, blood gases, haematological variables, plasma electrolytes (Na+, K+, Ca2+, Mg2+, Cl- and PO4(2-) ) and a variety of serum enzymes and chemical constituents were measured hourly until death (3 sheep) or until sheep were in extremis (2 sheep). Heart rate rose progressively as a result of sinus and, later, ventricular tachycardia. Systolic blood pressure rose, but there was little change in the mean and diastolic arterial pressures and central venous pressure. There was progressive hypoxaemia, hypercarbia and acidaemia with depletion of plasma bicarbonate. Haemoconcentration, hyperkalaemia and hypochloraemia were found along with rising serum creatinine and plasma glucose. Rises in serum enzymes indicated widespread tissue damage. Electrocardiographic recordings were being made at the moment of death in 3 of the 5 sheep. In these 3 sheep the cause of death was ventricular fibrillation.
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PMID:Some physiopathological features of experimental Homeria glauca (Wood & Evans) N. E. Br. poisoning in Merino sheep. 664 61

Asystole can be the presenting ECG finding of accidental hypothermia when the core temperature is less than 28 degrees C. Even two hours of persistent asystole does not represent irreversible cardiac compromise. With cardiopulmonary support and active rewarming, resuscitation and survival without serious sequelae can be achieved. Case reports and electrophysiology studies suggest that asystole is a primary manifestation of hypothermia potentiated by carbon dioxide retention. However, ventricular fibrillation in this setting is probably a secondary complication of resuscitation efforts, being precipitated by hypocapnic alkalosis, physical manipulation of the heart, and rewarming.
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PMID:Recovery after prolonged asystolic cardiac arrest in profound hypothermia. A case report and literature review. 698 23

During the global myocardial ischemia of cardiac arrest and during regional myocardial ischemia due to local impairment of coronary blood flow, intramyocardial carbon dioxide tensions (Pmco2) of ischemic myocardium increase to levels exceeding 400 Torr. The mechanism of such myocardial hypercarbic acidosis is as yet incompletely understood, specifically whether these increases in Pmco2 are due to increased oxidative metabolism, decreased CO2 removal, or buffering of metabolic acids. We therefore measured Pmco2 and the total CO2 content of rat hearts harvested before, during, and after resuscitation from cardiac arrest. Pmco2 significantly increased from an average of 63 to 209 Torr during a 4-min interval of untreated ventricular fibrillation. This was associated with concurrent decreases in intracellular pH from an average of 7.03 to 6.02 units. The total CO2 content of the myocardium simultaneously decreased from 17.0 to 16.5 mmol/kg. Accordingly, increases in Pmco2 and [H+] were observed in the absence of increases in the total CO2 content and therefore the calculated myocardial bicarbonate. These observations in the rat model implicate buffering of metabolic acids by bicarbonate rather than increases in CO2 production or decreases in CO2 removal as the predominant mechanism accounting for myocardial hypercarbia.
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PMID:Mechanisms of myocardial hypercarbic acidosis during cardiac arrest. 761 73

To investigate the response of the carotid blood flow and general circulation to hypercapnia in chronic nonpulsatile blood flow, we performed 18 carbon dioxide gas inhalation studies on three calves undergoing a centrifugal biventricular bypass with ventricular fibrillation. An ultrasonic flow probe was put on the carotid artery during biventricular bypass pump implantation, and pump flows were maintained at 90, 100, and 120 ml/kg per minute for 1 week each. The carbon dioxide inhalation studies were performed twice a week. Hypercapnia was induced by administering pure carbon dioxide gas through a nasal tube at flow rates of 0, 5, 7.5, 10, 12.5, and 15 L/min for 5 minutes each at three different nominal pump flow rates, and the resultant arterial blood gas and hemodynamic changes were recorded. No significant correlation existed between the carotid blood flow and mean aortic pressure, which varied from 70 to 140 mm Hg, but the carotid blood flow correlated significantly (p < 0.01) with the systemic pump flow rate. A significant (p < 0.01) linear relationship was found between the carotid blood flow and arterial carbon dioxide tension. For each 1 mm Hg change in arterial carbon dioxide tension, there was a 2.8 % change in the carotid blood flow. The percent changes in the carotid blood flow in response to arterial carbon dioxide tension were calculated as 2.9%, 3.7%, and 2.5% for each 1 mm Hg change in arterial carbon dioxide tension at pump flows of 90, 100 and 120 ml/kg per minute. No significant differences in the carotid blood flow response to hypercapnia were detected among the three systemic pump flow rates. These results thus suggested that chronic nonpulsatile blood flow had no detrimental effects on cerebral autoregulation.
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PMID:Chronic nonpulsatile blood flow. I. Cerebral autoregulation in chronic nonpulsatile biventricular bypass: carotid blood flow response to hypercapnia. 796 84


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