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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acid-base terminology including the sue of SI units is reviewed. The historical reasons why nomograms have been particularly used in acid-base work are discussed. The theoretical basis of the Henderson-Hasselbalch equation is considered. It is emphasized that the solubility of CO2 in plasma and the apparent first dissociation constant of carbonic acid are not chemical constants when applied to media of uncertain and varying composition such as blood plasma. The use of the Henderson-Hasselbalch equation in making hypothermia corrections for PCO2 is discussed. The Astrup system for the in vitro determination of blood gases and derived parameters is described and the theoretical weakness of the base excess concept stressed. A more clinically-oriented approach to the assessment of acid-base problems is presented. Measurement of blood [H+] and PCO2 are considered to be primary data which should be recorded on a chart with in vivo CO2-titration lines (see below). Clinical information and results of other laboratory investigations such as plasma bicarbonate, PO2,P50 are then to be considered together with the primary data. In order to interpret this combined information it is essential to take into account the known ventilatory response to metabolic acidosis and alkalosis, and the renal response to respiratory acidosis and alkalosis. The use is recommended of a chart showing the whole-body CO2-titration points obtained when patients with different initial levels of non-respiratory [H+] are ventilated. A number of examples are given of the use of this [H+] and PCO2 in vivo chart in the interpretation of acid-base data. The aetiology, prognosis and treatment of metabolic alkalosis is briefly reviewed. Treatment with intravenous acid is recommended for established cases. Attention is drawn to the possibility of iatrogenic production of metabolic alkalosis. Caution is expressed over the use of intravenous alkali in all but the severest cases of metabolic acidosis. The role of 2,3-diphosphoglycerate on tissue oxygenation is stressed and use of intravenous sodium phosphate as an alternative to intravenous bicarbonate is mentioned.
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PMID:The physiological assessment of acid-base balance. 23 27

Preserved stored blood undergoes metabolic changes depending on the duration of storage. These metabolic changes include a deprivation of 2,3-diphosphoglycerate (2,3-DPG), acidosis and hyperkalemia. The preservative contains citrate as an anticoagulant which binds the ionised serum calcium. 2,3-DPG depleted erythrocytes show a clearly elevated oxygen affinity. Following massive transfusion, these changes can also occur in the recipient. Under these conditions, patients with coronary artery disease show impaired heart function. Prejudicial changes concerning other vital systems have not yet been definitely proved. Acidosis, hypocalcemia and hyperkalemia can take place under massive transfusion. Normally the body's own compensatory mechanisms ensure sufficient recompensation; however, under hypothermia or shock these mechanisms can be impaired. Disturbances of the electrolyte and acid base system are safely detected by ECG and regularly performed acid base analysis.
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PMID:[Metabolic disorders caused by blood transfusions]. 306 47

Blood may provide superior cardioplegia compared with crystalloid cardioplegic solution. However, the results are controversial. This may be due to a leftward shift of the hemoglobin (Hb)-O2 dissociation curve induced by hypothermia, increasing the oxygen affinity for Hb. This effect may negate the potential benefit of blood cardioplegia. The oxygen affinity for Hb can be decreased by increasing the red cell 2,3-diphosphoglycerate (2,3-DPG), and hence, more oxygen can be delivered to the myocardium. The present investigation was undertaken to study the effects of 2,3-DPG-enriched blood cardioplegia on the functional recovery of the myocardium and changes in the coronary sinus red blood cell (RBC) adenosine-triphosphate (ATP), lactate, and RBC DPG after one and a half hours of reperfusion following one hour of ischemic cardiac arrest in dogs. The dogs were divided into three groups: crystalloid (CR); stored blood (SB), and high 2,3-DPG blood (HDPG) cardioplegic groups. Incubation of canine RBC in phosphoenal pyruvate (PEP) led to a 36% increase in DPG and a rightward shift in the Hb-O2 dissociation curve. There was a 4 mm Hg shift in the P50. When compared with the CR group, there was a significant decrease in the cardiac index (CI) and left ventricular work index (LVWI) and a significant increase in the total systemic vascular resistance (TSVR) in the SB group. The CI and LVWI of the HDPG group were similar to those of the CR group, but the TSVR was significantly greater in the former group. The LVWI was significantly greater and the TSVR smaller in the HDPG group as compared with those in the SB group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:High 2,3-DPG blood cardioplegia and myocardial preservation during cardiopulmonary bypass. 334 90

The Oxygen Status Algorithm is a computer program which uses measurements from a pH & blood gas analyser and a hemoximeter to calculate the oxygen status and the acid-base status of the arterial blood. Version 3 features on-line data collection from the analyser; storage of up to 2000 patient cases in a Lotus 123 file format; printing of a Cumulated Patient Report in addition to the Patient Status Report; combination of arterial and mixed venous data for calculation of the shunt and the oxygen consumption rate (when cardiac output is keyed in); calculation of reference values for fetal haemoglobin for newborns (when gestational age is keyed in). Examples of applications answer the following questions: 1) Does hyperventilation improve the oxygen supply to the tissues? No, for a normal person a slight hypoventilation with a pCO2 of 8.5 kPa provides a maximal oxygen extraction tension. 2) What is the optimal hyperventilation at the top of Mt. Everest (ambient pressure 33 kPa)? Hyperventilation to a pCO2 of about 1.4 kPa provides a maximal oxygen extraction tension of 2.4 kPa for an unacclimatized person. 3) Which change in haemoglobin oxygen affinity would be equivalent to a decrease in arterial pO2 to 6.3 kPa? The oxygen extraction tension would decrease to 4.0 kPa and the same value would be caused by a decrease in half-saturation tension to 2.8 kPa, a decrease which could be due to a moderate alkalaemia (pH = 7.54) combined with a moderately decreased 2,3-diphosphoglycerate concentration (3.4 mmol/L). 4) Is temperature correction of the measured pO2 and pCO2 to the actual body temperature needed? Yes, for example, omitting temperature correction even when the patient temperature is only slightly decreased to 36 degrees C would result in a negative value for the calculated arterio-venous shunt fraction when the actual value, using temperature correction, is 11%. 5) Does the alpha-stat approach of pCO2 and pH regulation in hypothermia, where pH is allowed to rise as in blood in vitro, cause a fall in mixed venous pO2 below the critical value? No, although the mixed venous pO2 will be lower than with the pH-stat approach (constant pH at body temperature), it remains above the critical mixed venous pO2 level. The program is intended for clinical routine use as well as teaching purposes. It has context sensitive help as well as an extensive help index. A number of "demo" cases are provided with annotations in a separate file.
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PMID:Oxygen status algorithm, version 3, with some applications. 859 66

Semi-fossorial ground squirrels face challenges to respiratory gas transport associated with the chronic hypoxia and hypercapnia of underground burrows, and such challenges are compounded in species that are native to high altitude. During hibernation, such species must also contend with vicissitudes of blood gas concentrations and plasma pH caused by episodic breathing. Here, we report an analysis of hemoglobin (Hb) function in six species of marmotine ground squirrels with different altitudinal distributions. Regardless of their native altitude, all species have high Hb-O2 affinities, mainly due to suppressed sensitivities to allosteric effectors [2,3-diphosphoglycerate (DPG) and chloride ions]. This suppressed anion sensitivity is surprising given that all canonical anion-binding sites are conserved. Two sciurid species, the golden-mantled and thirteen-lined ground squirrel, have Hb-O2 affinities that are characterized by high pH sensitivity and low thermal sensitivity relative to the Hbs of humans and other mammals. The pronounced Bohr effect is surprising in light of highly unusual amino acid substitutions at the C-termini that are known to abolish the Bohr effect in human HbA. Taken together, the high O2 affinity of sciurid Hbs suggests an enhanced capacity for pulmonary O2 loading under hypoxic and hypercapnic conditions, while the large Bohr effect should help to ensure efficient O2 unloading in tissue capillaries. In spite of the relatively low thermal sensitivities of the sciurid Hbs, our results indicate that the effect of hypothermia on Hb oxygenation is the main factor contributing to the increased blood-O2 affinity in hibernating ground squirrels.
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PMID:Hemoglobin function and allosteric regulation in semi-fossorial rodents (family Sciuridae) with different altitudinal ranges. 2417 89