Measurement Of Tissue pH Research Articles

Simultaneous measurement of fetal tissue pH and transcutaneous pO 2 during labor

Simultaneous measurement of fetal heart rate (FHR), uterine contractions (UC), continuous fetal tissue pH (TpH) and transcutaneous pO 2 (tc pO 2) was attempted in 40 high-risk parturients monitored for an average duration of 117 ± 74 min. There were only two failures (9%) in the last 23 cases, with satisfactory recording of all parameters in 78% of the total. At present, the feasibility of simultaneous biochemical monitoring is limited to the active phase of labor. Fetal scalp and umbilical arterial blood pH and pO 2 were obtained as well. The biochemical data showed a good correlation between tc pO 2, scalp capillary pO 2 and umbilical artery pO 2 ( P < 0.02). The correlation was not significant between similar pH comparisons, although an average difference of 0.04 pH units was observed between the final TpH and umbilical artery pH. Both fetal TpH and tc pO 2 fell progressively during labor. Preliminary findings comparing TpH, tc pO 2 and FHR suggest that changes in tc pO 2 rapidly reflect changing maternal and fetal conditions, while TpH responds more slowly and less sensitively.

The measurement of tissue pH at calcifying fronts by 31P NMR spectroscopy

The measurement of tissue pH at calcifying fronts by 31P NMR spectroscopy

Microcirculation and hemorrhagic shock

Blood loss is followed by compensatory cardiovascular readjustments that favor the maintenance of blood flow to central vital organs rather than to peripheral tissues. The microcirculatory changes that occur in skeletal muscle in shock states are of major importance, since skeletal muscle is not only the largest cell mass of the body but also one of the major target organs for neurohumorally mediated compensatory vascular readjustments. Intravital microscopic studies show that the microvascular blood flow in skeletal muscle is intermittent in the early posthemorrhagic period. This probably reflects an interplay between α-adrenergic vasoconstrictor and β-adrenergic vasodilator activities, which serves to enhance a compensatory mobilization of interstitial fluid into the vascular compartment. A period of complete microcirculatory arrest is then seen, followed by reperfusion engaging only 30% to 50% of the capillaries that were seen perfused in resting skeletal muscle. The microvascular blood flow in shock is further characterized by a pronounced heterogeneity in distribution. Many capillaries remain constantly unperfused, while in others a slow, intermittent blood flow is seen. Obstruction of many capillaries by white blood cells and their slow passage through other capillaries seem to be the main reasons for the maldistribution of capillary blood flow in shock. Red blood cell aggregates obstructing capillary blood flow are not seen. The heterogeneous tissue perfusion is accompanied by local variations in cellular hypoxic injury, as is evidenced by multifocal measurements of tissue oxygen tension and by cellular transmembrane potential registrations. The blood-tissue exchange of substances is impaired because of the reduction in capillary surface area and changes within the interstitial compartment. Therefore, shock-induced metabolic changes in skeletal muscle remain mainly local and are not at all, or only to a limited extent, reflected in central blood. Following volume treatment the heterogeneity in capillary perfusion persists, since white blood cells often remain trapped in capillaries and obstruct blood flow. Treatment of shock with hypertonic solutions, ATP-MgCl 2, or steroids could be beneficial by enhancing the mobilization of trapped white blood cells. Microcirculatory disturbances and their local metabolic consequences in skeletal muscle of critically ill patients can be monitored in the intensive care unit by the use of microelectrodes for continuous or intermittent measurements of tissue gas tensions (P 0 2 , P CO 2 ), tissue pH, and tissue potassium levels.

Clinical Problems of Continuous Fetal Tissue pH Measurement During Labor

Clinical Problems of Continuous Fetal Tissue pH Measurement During Labor

Naftidrofuryl for severe ischaemia: Assessment using skin pH micro-electrode measurements

SummaryTissue pH measurements in patients with peripheral vascular disease can provide an indication of tissue perfusion and metabolic status in areas affected by ischaemia. Using micro-electrodes which have been specially developed to measure tissue pH in the skin (pHs) it is possible to show a pH gradient along the lower limb in patients with severe ischaemia, which can be reversed by successful surgical treatment. The vasoactive drug naftidrofuryl has been shown to have properties which can improve oxidative metabolism within ischaemic cells without necessarily causing any haemodynamic alterations. These properties may be beneficial in patients with peripheral vascular disease. The micro-electrode method of pHs measurement was used to assess the effects of conservative management in patients with severe lower limb ischaemia due to peripheral vascular disease. Forty patients were randomly allocated into two groups who received either conventional conservative treatment alone, or conservative treatment p...

High Plasma HCO-3 Protects Gastric Mucosa Against Acute Ulceration in the Rat

The role of ambient HCO - 3 in the protection of gastric mucosa against luminal acid was studied with exogenously administered HCO - 3 . The glandular portion of rat gastric mucosa readily ulcerates when exposed to physiologic concentrations of luminal acid (50–150 mM HCl) during short-term hemorrhagic shock. Intravenous infusion of NaHCO 3 during the experiment, with consequent high-HCO - 3 metabolic alkalosis, significantly decreased the incidence and severity of mucosal lesions. In contrast, low-HCO - 3 respiratory alkalosis of similar degree, induced by mandatory hyperventilation, had no protective action against ulceration, suggesting that it is, indeed, the presence of HCO - 3 in the tissue rather than the attendant alkalinity per se that accounts for the protection during treatment with NaHCO 3 . Systemic administration of acetazolamide abolished the protection afforded by NaHCO 3 , suggesting that carbonic anhydrase is needed for utilization of NaHCO 3 for protection of the mucosa. The disparity in the susceptibility to ulceration between the experimental groups was not attributable to differences in mucosal blood flow during the shock as judged by gastric [ 14 C]aniline clearance. Direct measurement of tissue pH with a pH-sensitive microelectrode within the lamina propria of the mucosa indicated that, despite roughly equal rates of H + back diffusion, the degree of intramural acidification during hemorrhagic shock was significantly less in the alkalotic rats than in the controls, but no major differences in tissue pH existed between rats with metabolic alkalosis and those with respiratory alkalosis. Thus, HCO - 3 deficiency (and treatment with acetazolamide) seems to enhance susceptibility of the gastric mucosa to ulceration by decreasing its ability to tolerate intramucosal acidity.

Residual metabolism of the hypothermic-arrested pig heart

Fourteen Yorkshire pigs were anesthetized and placed on cardiopulmonary bypass. The hearts were cooled to 15°C and arrested with periodic injections of 50 ml of a cold ( T = 4°C) crystalloid cardioplegic solution containing 35 meq/liter K + for 2 hr. The hearts were then reperfused with warm oxygenated blood for 1 hr. A needle pH electrode (MI-408C, Microelectrodes, Inc., Londonderry, N. H.) was placed into the myocardium and measurements of tissue pH were taken during arrest and reperfusion. Tissue samples were taken during arrest and reperfusion and analyzed for their content of ATP, ADP, AMP, CP, and lactic acid. Blood samples were taken during reperfusion for measurement of CPK. Tissue concentrations of ATP and CP fell during arrest from 4.10 and 6.54 to 3.40 and 1.45 m M respectively. The concentrations of H + and of lactic acid rose during arrest from 2.8 × 10 −8 M and 10.48 m M to 27.5 × 10 −8 M and 18.95 m M, respectively. During reperfusion ATP continued to fall to 2.95 m M while blood CPK rose from 50.81 to 159.49 IU/L. The rise of H + during hypothermic arrest indicates the presence of residual metabolism which may have irreversibly changed the enzyme system for regulating the concentration of tissue ATP. Evidence for this conclusion is given by the escape of CPK into blood during reperfusion.

The Continuous Measurement of Tissue pH in the Human Fetus during Labour using a New Application Technique

The subcutaneous tissue pH (tpH) of 61 fetuses has been measured continuously during labour using the tissue pH electrode designed by Stamm (Stamm et al, 1976) and adapted for use by Roche Medical and Laboratory Systems. These 61 fetuses fell chronologically into two groups: Group 1 comprised 31 fetuses in whom the original method of fixation to the fetal scalp was used, and Group 2 comprised 30 fetuses in whom the fixation apparatus incorporated the latest technical developments of the double spiral electrocardiograph (ECG) electrode and the fetal tpH Applicator Tool Set Model 678449. Better results were obtained with Model 678449.

The influence of cord complications on fetal pH, neonatal Apgar score, and the acid base state and oxygenation of the umbilical artery and vein.

Continuous monitoring of fetal scalp tissue pH (tpH), acid base and oxygenation measurements of the blood of the umbilical artery and vein, and APGAR scoring was performed in 152 deliveries. The effect of cord complication on tpH (120, 90, 60, 30, 15, 10, 5, and 0 minutes before delivery), the status of the umbilical artery and vein (pH, pCO2, base excess, standard bicarbonate, pO2, and oxygen saturation), and the APGAR scores (one and five minutes after delivery) were investigated. Thirty-two per cent of the deliveries were associated with on or more cord complication(s). Cord complications in general did not influence the APGAR scores, the acid base state, or the oxygenation of the fetus and newborn. In the very few cases of tight cord complication(s) tpH showed a marked decrease during the last 30 minutes of labour, the umbilical blood was slightly acidotic, but the APGAR scores were normal (8-10 one and five minutes after delivery). No cases of prolapse of the cord were found. Cord complications are very common but in most cases completely harmless.

Measurement of tissue pH in skin by glass microelectrodes

Measurement of tissue pH in skin by glass microelectrodes

Continuous tissue pH measurement in critically ill adults with a miniaturised glass electrode

A continuously reading subcutaneous pH electrode has been developed which gives relatively stable readings when applied to any well perfused part of the body. The results obtained with this electrode have been compared with the actual pH of the arterial blood measured by conventional methods. Thirty patients were studied and one hundred and sixty three observations were made. The correlation coefficient (r) between tissue pH (pHt) and arterial pH (pHa) was 0.76 (P< 0.01). The response time of the electrode in vitro was less than one minute and, in vivo , stabilization of the recording occurred in less than three minutes. It was found that the discrepancy between pHa and pHt gave a good indication of the adequacy of tissue perfusion.

Sinusoidal fetal heart rate: II. Continuous tissue pH studies

Two cases of SHR in labor monitored by continuous fetal tissue pH measurements are presented. Both showed onset of the pattern in the absence of fetal acidosis, a fall in TpH following the appearance of the abnormal FHR pattern, and fetal compensation with a good perinatal outcome. These patients demonstrate that the fetus may tolerate a SHR and recover from preacidosis and acidosis. Continuous pH measurement may be helpful in conservative management of patients with abnormal FHR patterns.

Continuous Measurement of Tissue pH in the Human Fetus

Continuous Measurement of Tissue pH in the Human Fetus

An evaluation of a continuous tissue pH monitor in the fetal and neonatal goat

The validity of continuous tissue pH measurements was established in the fetal and neonatal goat model. Simultaneous determinations of tissue, arterial, and venous pH were done during alterations in acid-base status. A highly significant correlation was found between tissue and blood pH levels (r = 0.89, p < 0.001). These data confirm the accuracy of the tissue pH instrumentation in predicting core blood pH status and support the potential usefulness of the instrumentation in perinatal medicine for continuous fetal acid-base monitoring.

Continuous Measurement of Tissue and Coronary Venous pH during Myocardial Ischaemia in Dogs

Continuous Measurement of Tissue and Coronary Venous pH during Myocardial Ischaemia in Dogs

Measurement of tissue and intravascular pH with polymer membrane electrodes: S.M. Cobbe and P.A. Poole-Wilson. Cardiothoracic Institute, 2 Beaumont Street, London, England

Measurement of tissue and intravascular pH with polymer membrane electrodes: S.M. Cobbe and P.A. Poole-Wilson. Cardiothoracic Institute, 2 Beaumont Street, London, England

Continuous Measurement of Tissue pH in the Human Fetal Scalp

Summary A method for continuous measurement of scalp tissue pH is described. The tissue pH probe was found to be robust and values for tissue pH were close to those for scalp blood pH. Combining the pH and fetal heart rate (FHR) electrodes in the one mechanical assembly facilitated application to the fetal scalp in early labour but the combined assembly electrode was found to have some disadvantages and manufacture of a separate tissue pH electrode is recommended. Continuous monitoring of scalp tissue pH enables closer study of the physiological basis of changes in fetal acid base status and should prove useful to the obstetrician in management of high risk pregnancies during labour.

Continuous tissue pH measurement on the fetus during delivery.

Tissue pH values of 70 fetuses have been measured continuously during labor using the micro-electrode designed by Stamm. Significant correlation between continuous tissue pH and corresponding micro blood values can be shown. However, the relationship between patterns of tissue pH and capillary pH values seems not to be very constant. Therefore, the reliability of individual tissue pH measurements is still questionable.

Continuous measurement of tissue pH in the human fetal scalp.

A method for continuous measurement of scalp tissue pH is described. The tissue pH probe was found to be robust and values for tissue pH were close to those for scalp blood pH. Combining the pH and fetal heart fate (FHR) electrodes in the one mechanical assembly facilitated application to the fetal scalp in early labour but the combined assembly electrode was found to have some disadvantages and manufacture of a separate tissue PH electrode is recommended. Continuous monitoring of scalp tissue pH enables closer study of the physiological basis of changes in fetal acid base status and should prove useful to the obstetrician in management of high risk pregnancies during labour.

Principle and characteristics of the ROCHE tissue pH electrode.

A miniaturized probe for continuous measurement of tissue (interstitial fluid) pH is described. The electrode design follows closely the concept described by Stamm and co-workers. The pH sensitive tip has a length of 1 mm and is made of a Li-Ba-Si glass of low electrical resistivity. The reference electrode with a capillary type liquid junction is an integrated part of the electrode assembly. This paper summarizes the important design features of the electrode and describes its in vitro characteristics.