Blood pH Determinations Research Articles

Intravenous electrolyte solution containing 84 mEq/L of lactate corrects metabolic acidosis in goats

This study aimed to investigate the alkalinizing potential of an intravenous electrolyte solution formulated with a high concentration of sodium lactate in acidotic goats. Two solutions containing 84 mEq/L of lactate (L84) or bicarbonate (B84) were formulated. Six healthy Saanen goats were used in this study. Acute ruminal lactic acidosis (ARLA) was induced (15 g sucrose/kg) in all six goats. After 16 h, metabolic acidosis was established and the goats were treated by infusion of L84 or B84 at a speed of 25 ml/kg/h for four continuous hours; the total volume was equivalent to 10 % of their bodyweight. Each goat was induced twice, and the second induction was performed at least 30 days after complete clinical recovery from the first induction. Samples of venous blood and urine were collected at −16 h (before ARLA induction), 0 h, 2 h, 4 h (end of the infusion), 6 h, 12 h, and 24 h after the beginning of the infusion. Laboratory tests included the determination of blood pH, pCO2, HCO3−, BE, Na+, K+, Cl−, total plasma protein, l-lactate, d-lactate, and creatinine. For the urine samples, the pH, density, and concentrations of Na+, K+, Cl−, l-lactate, and creatinine were determined. The results were compared using two-way repeated-measures ANOVA. The metabolic acidosis due to ARLA was moderate. Both solutions (L84 and B84) corrected the metabolic acidosis and dehydration without differences between them. All goats completely recovered 3–4 days later. Taken all together, the electrolyte solution containing 84 mEq/L of lactate (L84) was effective in the treatment of metabolic acidosis induced by ARLA in goats.

Sodium bicarbonate improves sprint performance in endurance cycling

ObjectivesOral sodium bicarbonate intake (NaHCO3) may improve performance in short maximal exercise by inducing metabolic alkalosis. However, it remains unknown whether NaHCO3 also enhances all-out performance at the end of an endurance competition. Therefore, the present study investigated the effect of stacked NaHCO3 loading on sprint performance following a 3-h simulated cycling race. DesignDouble-blind randomized placebo-controlled cross-over study. MethodsEleven trained male cyclists (22.3 (18.3–25.3) year; 73.0 (61.5–88) kg; VO2max: 63.7 (57–72) mlkg−1min−1) ingested either 300mgkg−1 body weight NaHCO3 (BIC) or NaCl (PL). NaHCO3 or NaCl was supplemented prior to (150mgkg−1) and during (150mgkg−1) a 3-h simulated cycling race with a 90-s all-out sprint (90S) at the end. Capillary blood samples were collected for determination of blood pH, lactate and HCO3− concentrations. Analysis of variance (lactate, pH, HCO3−) and paired t-test (power) were applied to compare variables across condition (and time). ResultsNaHCO3 intake improved mean power during 90S by ∼3% (541±59W vs. 524±57W in PL, p=0.047, Cohen’s D=0.28, medium). Peak blood lactate concentration and heart rate at the end of 90S were higher (p<0.05) in BIC (16.2±4.1mmoll1, 184±7bpm) than in PL (12.4±4.2mmoll−1, 181±5bpm). NaHCO3 ingestion increased blood [HCO3−] (31.5±1.3 vs. 24.4±1.5mmoll−1 in PL, p<0.001) and blood pH (7.50±0.01 vs. 7.41±0.03 in PL, p<0.05) prior to 90S. ConclusionsNaHCO3 supplementation prior and during endurance exercise improves short all-out exercise performance at the end of the event. Therefore, sodium bicarbonate intake can be applied as a strategy to increase success rate in endurance competitions.

A simple electrochemical pH sensor based on black phosphorus nanosheets

In this work, black phosphorus nanosheets (BPNSs) were prepared by liquid exfoliation in N-methyl-2-pyrrolidone (NMP) and characterized by TEM, AFM, Raman spectroscopy and UV–vis absorption spectroscopy. A novel electrochemical sensor was constructed based on the BPNSs and used to measure pH. As the pH of the solution increases, the oxidation current of the BPNSs decreases. The oxidation degree of the BPNSs may be responsible for their different electrochemical responses to pH. The zeta potentials of the BPNSs also appear to be more negative at higher pH values. The results show that the sensor has a linear response in the pH range 1.0–8.0. The resulting electrochemical sensor could thus be used for accurate pH measurement and was successfully applied to the determination of pH in blood and food samples. The proposed method is simple but is shown to have high accuracy, versatility and applicability.

Does NaHCO3 intake increase muscle fatigue resistance of individuals trained during intermittent high intensity exercise performed on the isokinetic dynamometer?

Oral sodium bicarbonate intake (NaHCO3) may improve performance in short maximal exercise by inducing metabolic alkalosis. However, it remains unknown whether NaHCO3 also enhances all-out performance at the end of an endurance competition. Therefore, the present study investigated the effect of stacked NaHCO3 loading on sprint performance following a 3-h simulated cycling race.Double-blind randomized placebo-controlled cross-over study.Eleven trained male cyclists (22.3 (18.3–25.3) year; 73.0 (61.5–88) kg; VO2max: 63.7 (57–72) ml kg−1 min−1) ingested either 300 mg kg−1 body weight NaHCO3 (BIC) or NaCl (PL). NaHCO3 or NaCl was supplemented prior to (150 mg kg−1) and during (150 mg kg−1) a 3-h simulated cycling race with a 90-s all-out sprint (90S) at the end. Capillary blood samples were collected for determination of blood pH, lactate and HCO3− concentrations. Analysis of variance (lactate, pH, HCO3−) and paired t-test (power) were applied to compare variables across condition (and time).NaHCO3 intake improved mean power during 90S by ∼3% (541 ± 59 W vs. 524 ± 57 W in PL, p = 0.047, Cohen’s D = 0.28, medium). Peak blood lactate concentration and heart rate at the end of 90S were higher (p < 0.05) in BIC (16.2 ± 4.1 mmol l 1, 184 ± 7 bpm) than in PL (12.4 ± 4.2 mmol l−1, 181 ± 5 bpm). NaHCO3 ingestion increased blood [HCO3−] (31.5 ± 1.3 vs. 24.4 ± 1.5 mmol l−1 in PL, p < 0.001) and blood pH (7.50 ± 0.01 vs. 7.41 ± 0.03 in PL, p < 0.05) prior to 90S.NaHCO3 supplementation prior and during endurance exercise improves short all-out exercise performance at the end of the event. Therefore, sodium bicarbonate intake can be applied as a strategy to increase success rate in endurance competitions.

Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs

To compare the cardiopulmonary effects of continuous rate infusions (CRIs) of alfaxalone-2-hydroxypropyl-beta-cyclodextrin (HPCD) and propofol in healthy dogs. 6 young adult medium-sized healthy crossbred dogs. A crossover design was used with a washout period of 6 days between anesthetic treatments. Each dog was sedated with acepromazine (0.02 mg/kg, IV) and hydromorphone (0.05 mg/kg, IV). Anesthesia was induced with propofol (4 mg/kg) or alfaxalone-HPCD (2 mg/kg). After endotracheal intubation, anesthesia was maintained with the same agent (propofol, 0.25 mg/kg/min; alfaxalone-HPCD, 0.07 mg/kg/min) for 120 minutes. Dogs spontaneously breathed 100% oxygen. Measurements included end-tidal partial pressure of carbon dioxide, heart and respiratory rates, mean arterial blood pressure, thermodilution-derived cardiac output, and body temperature. Paired arterial and mixed venous blood samples were collected for determination of blood pH, PaCO(2), and PaO(2). Data were recorded prior to induction; 5, 15, 30, 60, 90, and 120 minutes after induction of anesthesia; and 20 minutes after stopping the CRI, when feasible. Stroke volume and systemic vascular resistance were calculated. Quality of anesthetic induction and recovery and interval to recovery were recorded. Both propofol and alfaxalone-HPCD produced excellent induction of anesthesia, maintenance, and recovery. Respiratory depression was evident with both anesthetics. Clinically acceptable, mild hemodynamic changes were similar for both anesthetics. Alfaxalone-HPCD produced clinically acceptable anesthetic quality and hemodynamic values ideal for use as a CRI. Ventilation may need to be supported if hydromorphone is used at these propofol and alfaxalone-HPCD infusion rates.

An all-solid-state reference electrode based on the layer-by-layer polymer coating

A solid-state reference electrode (SSRE) was fabricated by layering a silicone rubber (SR) film containing KCl on an AgCl surface, then a perfluorinated ionomer film, and finally a polyurethane-based membrane containing an ionophore, a lipophilic ionic additive, and a plasticizer, respectively. The addition of SiCl4 to the polyurethane-based membrane layer enhanced the strength of the membrane in an aqueous solution. The morphologies of the membranes were studied separately by SEM. The fabrication of the Ag/AgCl electrode through this layer-by-layer polymer coating improved the electrode stability enormously. In addition, the potential drift of the SSRE according to the pH of the medium was minimized by introducing a H+-ion-selective ionophore (tridodecylamine; TDDA) into the outmost polymer membrane. The cyclic voltammetric and potentiometric responses using the SSRE and a conventional reference electrode, respectively, were consistent. The SSRE exhibited little potential variation even in the case of the addition of very high concentrations of various salts, such as Na salicylate, LiCl, KCl, CaCl2, MgCl2, KNO3, NaCl, and NaHCO3. The practicability of the proposed SSRE was tested for the determination of blood pH and pCO2 in a flow cell system. The SSRE fabricated in the present study was stable over two years.

Is lactic acidosis a cause of exercise induced hyperventilation at the respiratory compensation point?

Objectives: The respiratory compensation point (RCP) marks the onset of hyperventilation (“respiratory compensation”) during incremental exercise. Its physiological meaning has not yet been definitely determined, but the most common explanation...

Influence on fetal blood pH when adding amniotic fluid: an in vitro model.

To assess the effect of contamination with amniotic fluid in different quantities on fetal capillary blood pH. In vitro model. Department of Obstetrics, St Pölten Hospital. Venous umbilical blood and amniotic fluid from 35 women who underwent amniotomy during labour. Venous umbilical blood was mixed in vitro with amniotic fluid in diluted series (venous umbilical blood/amniotic fluid, 10:1 to 1:1). In every case two parallel runs of the dilution series in an inverted fashion were performed to rule out a possible time-dependent bias of the pH measurements. pH change in dilutions of umbilical venous blood with amniotic fluid: 10:1, +0.07 (0.02); 8:1, +0.08 (0.02); 6:1, +0.08 (0.03); 4:1, +0.07 (0.02); 2:1, +0.09 (0.03); 1:1, +0.12 (0.05); all P < 0.001. Amniotic fluid pH increases, whereas umbilical blood pH decreases slightly over time since collection. Dilutions of umbilical venous blood with amniotic fluid resulted in a significant pH rise. There was no significant difference between the two inversely performed dilution series. Amniotic fluid influences in vitro fetal venous blood pH immediately after contact. This observation indicates the possible masking of a fetus in distress by fetal scalp blood pH determination when amniotic fluid contaminates the sample.

Influence on fetal blood pH when adding amniotic fluid: an in vitro model

Objective To assess the effect of contamination with amniotic fluid in different quantities on fetal capillary blood pH. Design In vitro model. Setting Department of Obstetrics, St Pölten Hospital. Sample Venous umbilical blood and amniotic fluid from 35 women who underwent amniotomy during labour. Methods Venous umbilical blood was mixed in vitro with amniotic fluid in diluted series (venous umbilical blood/amniotic fluid, 10:1 to 1:1). In every case two parallel runs of the dilution series in an inverted fashion were performed to rule out a possible time-dependent bias of the pH measurements. Main outcome measures pH change in dilutions of umbilical venous blood with amniotic fluid: 10:1, +0.07 (0.02); 8:1, +0.08 (0.02); 6:1, +0.08 (0.03); 4:1, +0.07 (0.02); 2:1, +0.09 (0.03); 1:1, +0.12 (0.05); all P < 0.001. Results Amniotic fluid pH increases, whereas umbilical blood pH decreases slightly over time since collection. Dilutions of umbilical venous blood with amniotic fluid resulted in a significant pH rise. There was no significant difference between the two inversely performed dilution series. Conclusion Amniotic fluid influences in vitro fetal venous blood pH immediately after contact. This observation indicates the possible masking of a fetus in distress by fetal scalp blood pH determination when amniotic fluid contaminates the sample.

Doppler ultrasonography of the umbilical cord in complicated pregnancies.

Ninety-two gravid women had Doppler insonation of the umbilical cord after diagnosis of various pregnancy complications. Calculations of the systolic-diastolic (S/D) ratio were plotted against a nomogram of values developed at the Hospital of the University of Pennsylvania. An S/D ratio greater than the 95th percentile for gestational age correctly predicted 58% of women who became preeclamptic and 61% of infants who were small for gestational age (SGA). Of those fetuses with an elevated S/D ratio, 42% suffered fetal distress as defined by an abnormal fetal heart rate tracing, a 1- or 5-minute Apgar score less than 5 or 7, respectively, or a cord blood pH determination less than 7.20; 60% required operative delivery; and 49% stayed in the hospital longer than 5 days or were admitted to the Neonatal Intensive Care Unit (NICU). All these values are significantly greater than those obtained in a control group of uncomplicated pregnancies or a group of women with similar pregnancies, but with normal measurements of the umbilical artery S/D ratio. Moreover, 69% of abnormally elevated umbilical artery S/D ratios were detected at or before 30 weeks' gestation. Calculation of an S/D ratio of the umbilical cord greater than the 95th percentile for gestational age is an early and sensitive predictor of poor perinatal outcome.

Questioning the Practice of Routine Umbilical Cord Blood pH Sampling at Delivery

The objective of this study was to review the results of the practice of routine cord blood pH determination in order to ascertain its value and cost-effectiveness in patient care. Retrospective study of all deliveries in two hospitals for 1 year was carried out, correlating pH with outcome. Two teaching hospital obstetric services with somewhat different patient populations but similar practices were selected for the study. The participants comprised all 3,183 delivered patients on whom samples were obtained and 398 without sampling. Babies were followed up by chart review through the time of transfer or discharge.Cord arterial pH values averaged 7.31 +/− 0.08 S.D., with 103 (3.2%) showing values > −2 S.D. (<7.16); only 19.4% of these had low Apgar scores (<7) at 5 minutes. Of all babies delivered, 61 (1.9%) had low Apgar scores, but only one-third had low pH values. Both the low Apgar and low pH groups had increased frequencies of prolonged hospital stays and of anomalies. Those with low pH but without low Apgar scores generally behaved as normal newborns and were discharged at expected times. Low pH was associated with normal Apgars in 2.6% of cases.True asphyxial events and findings of early neurologic abnormality were very rare. Correlations between low pH or Apgar scores and outcomes were uncommon. The practice cost consumers over $100,000. The data raise serious questions as to the utility of routine, nonselective sampling of vigorous newborns.

Response of Fetal Heart Rate to Scalp Stimulation Related to Fetal Acid-Base Status

The correlation of the response of the fetal heart rate (FHR) to scalp stimulation and the acid-base status of the fetal scalp blood (FSB pH) was studied in 104 term fetuses during labor. The mean FHR was determined for the 5-minute period before the preparation for fetal scalp blood pH determination and 1 minute following FSB pH. The analysis was performed for three pH groups: (a) Normal (pH more than 7.25, = 73); (2) preacidotic (pH 7.20 to 7.25, = 16); and (3) acidotic (pH less than 7.20, = 15). The pH was confirmed at delivery by determination of umbilical cord blood acid-base status. Regression analysis of the number of fetuses responding by changing their heart rate against time was significant only for the nonacidotic fetuses. There was no significant difference in the number of subjects whose mean FHR increased, decreased, or remained unchanged between the three pH groups. Furthermore, there was no difference between the three pH groups in the number of fetuses who demonstrated significant mean heart rate changes (p less than 0.05) following the stimulation compared to those who did not. Further analysis between fetuses in the three pH groups who increased FHR 15 beats/min or more following stimulation did not discriminate between groups. We conclude that scalp stimulation results in a FHR response in all three pH categories. However, the net change in the mean heart rate following the stimulation may be negative or positive. The magnitude and the direction of this change in FHR is not significantly related to FSB pH.(ABSTRACT TRUNCATED AT 250 WORDS)

The syndrome of renal tubular acidosis and nerve deafness. Discordant manifestations in dizygotic twin brothers

The syndrome of renal tubular acidosis (RTA) and nerve deafness is a distinct nosological entity that is inherited as an autosomal recessive trait. We studied a pair of dizygotic twin brothers both with nerve deafness but only one with RTA. Distal RTA was diagnosed in twin A because of inappropriately high urinary pH (6.9) and low net acid excretion (40.0 muEq/min per 1.73 m2) in the presence of hyperchloraemic metablic acidosis, and fractional bicarbonate excretion of 1.6% at a normal serum bicarbonate concentration. The urine minus blood PCO2 differences (U-B PCO2) during a neutral sodium phosphate load and in alkaline urine induced by bicarbonate supplementation were: 11 and 0 mm Hg, respectively. Twin A developed nephrocalcinosis and, after a 9.5-year follow-up period, was 5.3 cm taller than his brother. Twin B remained asymptomatic. Periodic determinations of blood pH and serum bicarbonate were normal and urine pH decreased to 4.6 in the face of ammonium chloride-induced metabolic acidosis. The U-B PCO2 assessed in alkaline urine was 33.5 mm Hg. Audiograms demonstrated bilateral nerve deafness in both brothers. The presence of deafness without RTA has not been previously reported in this syndrome. This report also shows that a primary distal acidification defect is responsible for the RTA observed in this syndrome.

Kinetic Modeling of Intracellular pH and Comparison with 31P NMR Experimental Values in Dialysed Uremic Patients

Changes in intra-erythrocytic pH values over time, during and after bicarbonate hemodialysis, were studied with 31P Nuclear Magnetic Resonance. Simultaneously, pH values of whole blood were obtained by a gazometric method. A two-compartment model appeared to be the simplest kinetic model to explain the shifts in proton concentrations in extra- and intra-cellular media. Non-linear regression was used to determine exchange constant values. There was a very good correlation between the experimental and calculated proton concentrations. This model can describe all patients but individual experimental constants must be determined. Under these conditions a single blood pH determination before dialysis will permit determination of the initial intra-erythrocytic pH and monitoring of intra-erythrocytic pH during hemodialysis.

Fetal distress during labour in diabetic pregnancy.

The frequency of fetal distress in labour was studied in 46 diabetic women and in 46 non-diabetic matched controls. Fetal distress was assessed by electronic fetal heart rate (FHR) monitoring and fetal scalp blood pH determinations in late first stage of labour. Ominous FHR and/or low pH (less than 7.26) was more common in the diabetic group than in the control group (17.4% and 10.9%, respectively) but the difference was not statistically significant. The frequency of caesarean section and low Apgar score at 1 min was significantly higher in the diabetic group (P less than 0.05). There was no correlation between maternal blood glucose regulation and the occurrence of fetal distress in the diabetic group. The results suggest that fetal distress may be slightly more common in labour in diabetic women compared with controls managed in a similar way. Careful FHR monitoring and liberal use of fetal scalp blood pH determinations is recommended.

On the use of monocrystalline antimony pH electrodes in gastro-oesophageal functional disorders.

Monocrystalline antimony electrodes have been shown to be suitable for thein vivo determination of pH in blood, tissue and in the upper gastro-intestinal canal. Thanks to their small dimensions it has been possible to mount them into conventional manometry catheters for oesophageal investigation. The monocrystalline antimony pH electrode has several advantages over the conventional pH glass electrode; better accuracy, shorter rise time, smaller dimensions. The monocrystalline antimony electrode has been used for long-term registration of gastro-oesophageal reflux, for the oesophageal acid clearing test and for identification of the pH gradient zone between the gastric and oesophageal mucosa. Its use in combination with pressure sensors has added a new dimension to the diagnosis of functional disorders in the gastro-oesophageal region.

Haematological assessment of generally used freshwater fish blood anticoagulants

Heparin injection B.P., containing 0·5% phenol as preservative, disodium ethylenediamine tetra‐acetate (EDTA), trisodium citrate (TSC) and ammonium potassium oxalate (APO) were compared as anticoagulants for routine haematological investigations in Cyprinus carpio and Sarotherodon mossambicus. The acidic nature and haemolytic effects of EDTA and APO render them unsuitable for use with fish blood. TSC was required in higher concentrations (than heparin) for effective anticoagulation and this was undesirable for the determination of blood pH and pCO2 and certain other parameters. Several important interspecies differences in the reactions towards the anticoagulants are also reported. In general, heparin proved to be the anticoagulant of choice, although unsuitable for some assays.

The significance of sinusoidal fetal heart rate pattern during labor and its relation to fetal status and neonatal outcome.

Twenty-seven cases of sinusoidal fetal heart rate were studied. This group had a mean scalp pH of 7.288, significantly lower (p less than 0.005) than that of the control group. The mean one-minute Apgar score was 7.148, significantly lower (p less than 0.001) than the control group's mean score. Almost half (48,15%) of the fetuses had a one-minute Apgar score of 7 or less. Every fetus was viable. Amplitude of the pattern was found to correlate with neonatal depression, the larger the amplitude, the more profound the depression. Over 96% of the fetuses had cord-related deceleration patterns, and nearly 63% had obvious cord complications. It is postulated that sinusoidal patterns are an umbilical cord-related phenomenon, resulting from an alternating hypovolemia and hypervolemia. Clinicians are urged to scrutinize carefully any cases of this pattern, and perform an immediate fetal scalp blood pH determination. If the pH determination obtained is less than 7.25, the authors suggest intervention and operative delivery.

Redesigned Apparatus for Anaerobic Measurement of Blood pH at Low Temperatures

A newly designed apparatus for anaerobic measurement of blood pH at low temperatures is presented. This apparatus features a larger glass electrode surface area, which is necessary to overcome the increased resistance of the glass as blood pH determinations at 0-15 C. are undertaken. Utilization of this equipment has confirmed the deltapH per degree C. of whole blood to be 0.0156, while intracellular pH of blood has a deltapH per degree C. of 0.0165.

Calculations and Correction Factors Used in Determination of Blood pH and Blood Gases

Abstract Measurement of blood pH, po2 and pco2 also involves calculation of two or more derived quantities and correction of the measured values in cases where the body temperature of the patient differs from the temperature of measurement. References to the pertinent calculations and the temperature corrections are scattered through the literature of several medical specialties, and much new information has been gathered in recent years that directly affects these calculations. This review explains each of the derived quantities and correction factors most used in this field and also provides the best available data for the calculations, in a form that can readily be adapted to electronic data processing.