Blood pH Measurements Research Articles

Capillary blood parameters are gestational age, birthweight, delivery mode and gender dependent in healthy preterm and term infants.

The measurement of blood pH and gas analytes (BPGA), soon after birth, constitutes the first-line standard of care procedure in high-risk newborns. However, no data is available in capillary blood on perinatal bias such as gestational age (GA), weight at birth (BW), delivery mode, and gender. The aims of the present study were to investigate whether in a cohort of healthy preterm (PT) and term (T)infants BPGA were GA, BW, delivery mode and gender dependent, thus affecting BPGA reliability as diagnostic test. We performed a prospective case-control study in 560 healthy infants (PT: n=115, T: n=445). BPGA was measured within 24-h from birth. Perinatal characteristics, outcomes, and clinical examination were also recorded. PT infants showed higher (p<0.001) carbon dioxide partial pressure (pCO2), fraction of fetal hemoglobin (HbF), base excess (BE), bicarbonate (HCO3), and lower lactate (Lac) levels. When corrected for delivery mode, higher (p<0.001) HbF, BE, HCO3, and lower Lac levels were found. Similarly, higher (p<0.05, for all) pCO2, HbF, BE, HCO3 and lower Lac levels were found between female and male PT and T infants. Repeated multiple logistic regression analysis showed that BPGA was GA, BW, delivery mode and gender dependent. The present results showing that BPGA can be affected by a series of perinatal outcomes open the way to further investigations providing longitudinal BPGA reference curves in the transitional phase, thus empowering BPGA role as a reliable diagnostic and therapeutic strategies efficacy marker.

Prevalence of Perinatal Asphyxia Using Apgar Scores and Cord Blood pH and the Relationship between the Two Methods: A Study of FMC Umuahia.

Perinatal asphyxia contributes significantly to neonatal morbidity and mortality. It occurs worldwide, and the Apgar score is the most widely used method of diagnosis. Recently, umbilical cord arterial pH has been reported as the most objective way to assess fetal acidosis at birth as it predicts the adverse outcome of perinatal asphyxia. It is imperative to establish the concordance between these two diagnostic methods to reinforce the practicality of the Apgar score as the preferred diagnostic tool for perinatal asphyxia in developing nations, such as Nigeria. To determine the prevalence of perinatal asphyxia by using the Apgar score and arterial cord blood pH and the relationships between these methods at the Federal Medical Center (FMC), Umuahia. This cross-sectional study enrolled 245-term newborns. Perinatal asphyxia was diagnosed using both Apgar scoring and arterial cord blood pH measurements. Data obtained were analyzed using SPSS version 20 and a P value < 0.05 was considered significant. Perinatal asphyxia was reported in 33.1% and 31.4% by using the Apgar score and arterial cord blood pH, respectively. There was a moderate agreement between the two methods for diagnosing perinatal asphyxia (κ = 0.44), and no statistically significant difference was observed in the prevalence of perinatal asphyxia between these methods (McNemar's χ2 = 0.27, P = 0.699). Furthermore, a strong positive correlation was observed between the Apgar score at 1 and 5 minutes of life and arterial cord blood pH (rs = 0.87, P ≤ 0.001 and rs = 0.80, P ≤ 0.001 respectively). The prevalence of perinatal asphyxia by the two methods was high, and there was no significant difference between both methods of assessing perinatal asphyxia. Thus, the diagnosis of perinatal asphyxia can effectively be made using either the Apgar score or arterial cord blood pH, affirming the practicality and reliability of the Apgar score in resource-limited healthcare settings.

The therapeutic effect of a novel parenteral formulation of dihydroxyacetone in aluminum phosphide-intoxicated patients

Background and objectivesAluminum phosphide (AlP), known as “rice tablet,” is widely used as an effective pesticide. However, AlP poisoning is a common cause of mortality in many countries, such as Iran. Unfortunately, there is no specific antidote for AlP toxicity to date. AlP releases phosphine gas when it is exposed to moisture or acid. Phosphine is a potent mitochondrial toxin that could significantly inhibit cellular energy metabolism. AlP poisoning is an emergency condition that needs instant and effective intervention. Dihydroxyacetone (DHA) is a simple saccharide used for several pharmacological as well as cosmetic purposes. Previously, we found that DHA could significantly prevent mitochondrial impairment induced by toxic agents such as cyanide and phosphine in various in vitro and in vivo experimental models. MethodsHospitalized patients (n = 111) were evaluated for eligibility criteria. Among these patients, n = 35 cases were excluded due to incomplete data (n = 11) and suspicion of poisoning with poisons other than AlP (n = 24). Meanwhile, n = 76 cases with confirmed AlP poisoning were included in the study. AlP-poisoned patients who did not receive DHA (n = 18) were used as the control group.Patients (n = 58) received at least one dose of DHA (500 ml of 5 % DHA solution w/v, i.v.) as an adjuvant therapy in addition to the routine treatment of AlP poisoning. Arterial blood gas (ABG), blood pH, bicarbonate levels, and other vital signs and biochemical measurements were monitored. Moreover, the mortality rate and hospitalization time were evaluated in DHA-treated and AlP-poisoned patients without DHA administration. Several biomarkers were assessed before (upon hospitalization) and after DHA treatment. The routine tests for AlP-poisoned patients in this study were the measurement of electrolytes (K+ and Na+), WBC, RBC, hemoglobin, INR, carbonate (HCO3), blood pH, PaCO2, and PaO2 and SGPT, SGOT, BUN, Cr. ResultsUpon patients' admission, significant decreases in blood pH (acidosis), blood PaO2, and HCO3 levels were the hallmarks of AlP poisoning. It was found that DHA significantly alleviated biomarkers of AlP poisoning and tremendously enhanced patients’ survival rate (65.52 % in DHA-treated vs 33.34 % in the control group) compared to patients treated based on hospital routine AlP poisoning protocols (no DHA). No significant adverse effects were evident in DHA-treated patients in the current study. Interpretation and conclusionsThese data suggest that parenteral DHA is a novel and effective antidote against AlP poisoning to be used as an adjuvant in addition to routine supportive treatment. Trial registrationIR.SUMS.REC.1394.102.

Cerebral blood flow velocity and oxygenation in neonatal aortic arch repair at two perfusion temperatures.

(i) To monitor cerebral blood flow velocity (CBFv) throughout aortic arch repair surgery and during the recovery period. (ii) To examine the relationship between transcranial doppler ultrasound (TCD) and near-infrared spectroscopy (NIRS) during cardiac surgery. (iii) To examine CBFv in patients cooled to 20°C and 25°C. During aortic arch repair and after surgery, measurements of TCD, NIRS, blood pH, pO2, pCO2, HCO3, lactate, Hb, haematocrit (%) and temperature (core and rectal) were recorded in 24 neonates. General linear mixed models were used to examine differences over time and between two cooling temperatures. Repeated measures correlations were used to determine the relationship between TCD and NIRS. CBFv changed during arch repair (main effect of time: P = 0.001). During cooling, CBFv increased by 10.0 cm/s (5.97, 17.7) compared to normothermia (P = 0.019). Once recovering in paediatric intensive care unit (PICU), CBFv had increased from the preoperative measurement by 6.2 cm/s (0.21, 13.4; P = 0.045). CBFv changes were similar between patients cooled to 20°C and 25°C (main effect of temperature: P = 0.22). Repeated measures correlations (rmcorr) identified a statistically significant but weak positive correlation between CBFv and NIRS (r = 0.25, P≤0.001). Our data suggested that CBFv changed throughout aortic arch repair and was higher during the cooling period. A weak relationship was found between NIRS and TCD. Overall, these findings could provide clinicians with information on how to optimise long-term cerebrovascular health.

Performance Testing of Paper-based Electrochemical Sensor for Blood pH Measurements

Performance Testing of Paper-based Electrochemical Sensor for Blood pH Measurements

A Study on Correlation of Umbilical Cord Arterial Blood pH with Perinatal Asphyxia &amp; Early Neonatal Outcome

Background: Perinatal asphyxia is one of the major causes of neonatal morbidity &amp; mortality. Asphyxia can damage almost every organ of neonate. Our purpose was to determine the correlation of cord blood pH with birth asphyxia &amp; early neonatal outcome. Subjects and Methods: A prospective study was conducted over a period of one year at STH Haldwani. We enrolled 108 term neonates with signs of fetal distress, thick MSL, non-reassuring NST &amp; there were subjected for estimation of umbilical cord blood pH, APGAR score, outcome looked were resuscitation needed, NICU admission, delay in feed &amp; encephalopathy (sarnat &amp; sarnat stage). Results: In our study, cord blood pH had significant correlation with perinatal asphyxia(R=-0.926). Area under ROC curved showed that mean pH &lt;7.1 (ROC=0.998) is very significant in predicting the adverse outcome. Conclusion: Cord blood pH is very sensitive and specific &amp; has good correlation in predicting the birth asphyxia &amp; adverse neonatal outcome. Measurement of cord blood pH is recommended in all the neonates with signs of fetal distress.

Plasma β-Hydroxybutyrate for the Diagnosis of Diabetic Ketoacidosis in the Emergency Department.

Diabetic ketoacidosis (DKA) is a common emergency department presentation of both new-onset and established diabetes mellitus (DM). β-Hydroxybutyrate (BOHB) provides a direct measure of the pathophysiologic derangement in DKA as compared with the nonspecific measurements of blood pH and bicarbonate. Our objective was to characterize the relationship between BOHB and DKA. This is a cross-sectional retrospective study of pediatric patients with DM presenting to an urban pediatric emergency department between January 1, 2016, and September 30, 2018. Analyses were performed on each patient's initial, simultaneous BOHB and pH. Diagnostic test characteristics of BOHB were calculated, and logistic regression was performed to investigate the effects of age and other key clinical factors. Among 594 patients with DM, with median age of 12.3 years (interquartile range, 8.7-15.9 years), 176 (29.6%) presented with DKA. The inclusion of age, transfer status, and new-onset in the statistical model did not improve the prediction of DKA beyond BOHB alone. β-Hydroxybutyrate demonstrated strong discrimination for DKA, with an area under the curve of 0.95 (95% confidence interval, 0.93-0.97). A BOHB value of 5.3 mmol/L predicted DKA with optimal accuracy (90.6% of patients were correctly classified). The sensitivity, specificity, and positive and negative predictive values of this cut point were 76.7% (95% confidence interval, 69.8%-82.7%), 96.4% (94.2%-98.0%), 90.0% (84.0%-94.3%), and 90.8% (87.7%-93.3%), respectively. β-Hydroxybutyrate accurately predicts DKA in children and adolescents. More importantly, because plasma BOHB is the ideal biochemical marker of DKA, BOHB may provide a more optimal definition of DKA for management decisions and treatment targets.

Associations between early intra-arrest blood acidaemia and outcomes of adult in-hospital cardiac arrest: A retrospective cohort study

Resuscitation guidelines list acidaemia as a potentially reversible cause of cardiac arrest without specifying the threshold defining acidaemia. We examined the association between early intra-arrest arterial blood gas (ABG) data and outcomes of in-hospital cardiac arrest (IHCA). This single-centred retrospective study reviewed patients with IHCA between 2006 and 2015. Early intra-arrest ABG data were measured within 10min of initiating cardiopulmonary resuscitation. The ABG analysis included measurements of blood pH, PaCO2, and HCO3-. Among the 1065 included patients, 60 (5.6%) achieved neurologically intact survival. Mean blood pH was 7.2. Mean PaCO2 and HCO3- levels were 59.7mmHg and 22.1mmol/L, respectively. A blood pH of 7.2 was identified by a generalised additive models plot to define severe acidaemia. The PaCO2 level was higher in patients with severe acidaemia (mean: 74.5 vs. 44.1mmHg) than in those without. Multivariable logistic regression analyses indicated that blood pH>7.2 was associated with a favourable neurological recovery (odds ratio [OR]: 2.79, 95% confidence interval [CI]: 1.43-5.46; p-value=0.003) and blood pH was positively associated with survival at hospital discharge (OR: 5.80, 95% CI: 1.62-20.69; p-value=0.007). Early intra-arrest blood pH was associated with IHCA outcomes, while levels of PaCO2 and HCO3- were not. A blood pH of 7.2 could be used as the threshold defining severe acidaemia during arrest and help profile patients with IHCA. Innovative interventions should be developed to improve the outcomes of patients with severe acidaemia, such as novel ventilation methods.

Exercise-Induced Dyspnea in Children and Adolescents: Differential Diagnosis.

Exercise-induced dyspnea in children and adolescents can occur for many reasons. Although asthma is the common cause, failure to prevent exercise-induced asthma by pretreatment with a bronchodilator, such as albuterol, indicates that other etiologies should be considered. Other causes of exercise-induced dyspnea include exercise-induced vocal cord dysfunction, exercise-induced laryngomalacia, exercise-induced hyperventilation, chest wall restrictive abnormalities, cardiac causes, and normal physiologic limitation. When exercise-induced dyspnea is not from asthma, cardiopulmonary exercise testing with reproduction of the patient's dyspnea is the means to identify the other causes. Cardiopulmonary exercise testing monitors oxygen use, carbon-dioxide production, end-tidal pCO2 (partial pressure of carbon dioxide), and electrocardiogram. Additional components to testing are measurement of blood pH and pCO2 when symptoms are reproduced, and selective flexible laryngoscopy when upper airway obstruction is observed to specifically identify vocal cord dysfunction or laryngomalacia. This approach is a highly effective means to identify exercise-induced dyspnea that is not caused by asthma. [Pediatr Ann. 2019;48(3):e121-e127.].

Evaluation of an alternative treatment protocol by aglepristone to induce parturition in ewes with an experimental model of early pregnancy toxemia

A new protocol with aglepristone to induce parturition in ewes with pregnancy toxemia has been reported in the present manuscript. Four experimental groups were defined: Group AG5 (n = 10), Group DEX (n = 10), Group NC (n = 5) and Group PT (n = 5) in which ewes were injected twice with 10 mg/kg of aglepristone and 5 ml dexamethasone in first two groups, respectively; whereas negative control and pregnancy toxemia groups received no treatment for parturition induction. Different clinical parameters associated with parturition in ewes and their newborns were investigated. Blood hematology and biochemical measurements were carried out both in ewes and lambs. Blood pH values of lambs were recorded during the study. The injection time-lambing time, injection time-vaginal discharge intervals, placental expulsion periods, placental weight and vaginal delivery interval between lambs, hematological and biochemical results were not statistically different among the groups (p > 0,05). Increased NEFA and β-HBA concentrations accompanied the disease and all ewes in AG, DEX and PT Groups developed clinical pregnancy toxemia (NEFA; P = 0,009) and β-HBA; (P = 0,039). The differences in rectal body temperature of lambs were not significant (p > 0,05), whereas birth weight was found statistically significant among groups (p < 0,05). Blood pH, biochemical and hematologic measurements of lambs had also significant differences depending on different time points. Parturition pathology by means of incomplete cervical dilatation was severely observed in DEX Group.The results of this study show that aglepristone application in pregnancy toxemia to induce parturition could precisely control lambing time without any side effects in either mothers or lambs. Apart from these, it could be speculated that dexamethasone seems to induce parturition causing crucial pathologies, which results in important and risky changes in newborns’ life. Incomplete cervical dilatation and continued ineffective uterine contractions could be a major factor of newborn losses because of placental separation and cessation of blood supply.

PENDEKATAN STEWART DALAM pH DARAH YANG MENDASARI ASIDOSIS METABOLIK

Metabolic acidosis is the most frequent acid-base disorder in patients of the Intensive Care Unit. By conventional approach based onpH value, [HCO3–], and base deficit (BD) from blood gas analyzer (BGA) measurement are often inappropriate with the clinical stateand inadequate in explaining the mechanism of the metabolic acidosis. The Stewart approach states that the blood pH is determinedby a strong ion difference (SID), the carbon dioxide tension (pCO2), the total concentration of non-volatile weak acid. The Stewartapproach may give a better understanding of the mechanisms that underlie the metabolic acidosis. The purpose of this study is to knowthe correlation of blood pH value measurement from BGA and calculation based on Stewart approach and identifying the mechanismsthat underlie a metabolic acidosis. In this study an analytic observational cross-sectional method was used. The examined subjectsconsisted of 71 patients who were admitted with a metabolic acidosis at the ICU from July up to August 2007. All patients were measuredfor their blood pH, pCO2, [HCO3–], BD, sodium, potassium, calcium, magnesium, chloride, lactate, albumin, and phosphate. The resultwas reported as the mean and standard deviation. The data were analyzed by Pearson's correlation test and linier multiple regression.Statistical significance was determined at p &lt; 0.05. The mean values of blood pH measurement from BGA and blood pH calculationbased on the Stewart approach were 7.33 (0.11) and 7.49 (0.11) (r = 0.681; p &lt; 0.001). Most patients had two underlying mechanisms ofmetabolic acidosis. Hyperlactatemia was present in 61.8%, hyperchloremia was present in 58.2% of patients. Based on this study so far,by using the Stewart approach there is an excellent and significant correlation between the blood pH measurement from BGA and bloodpH calculation. Hyperlactatemia and hyperchloremia are the main causes of the metabolic acidosis in patients of the ICU ward.

Intervention of the obstetrician during childbirth in a supposedly low-risk population and influence of parity

ObjectiveCompare obstetrician intervention and calling rates during labour and delivery between low-risk and high-risk women and study the influence of parity on these rates. Material and methodsDescriptive retrospective study conducted on 227 patients in a university maternity unit (level 3 university hospital maternity unit) between 1st and 30th January 2014. The low- and high-risk populations were characterised according to the French National Authority for Health (HAS) and NICE guidelines. The obstetrician intervention criteria were: Caesarean section, instrumental vaginal delivery, artificial delivery/uterus examination and postpartum haemorrhage. The obstetrical team also had to call the obstetrician in case of foetal heart rate abnormalities, scalp blood pH measurement, third and/or fourth degree perineal tears, labour dystocia, or any other severe event occurring during labour or delivery. ResultsIn univariate analysis, the obstetrician intervention rates were respectively 44.5% and 34.4% in the high- and low-risk groups (P=0.13). The obstetrician calling rates were similar between the two groups. Using logistic regression model including parity, the obstetrician intervention rate became significantly higher in the “high-risk” group (OR 2.044, 95% CI 1.129–3.703, P=0.018). In the low-risk population, the intervention rate was significantly increased for nulliparous women compared with multiparas (47.5% versus 9.7%, P<0.001, OR=8.2, CI 95% 2.2 to 46.9). ConclusionOne third of the women defined as low-risk patients appear to need an obstetrician intervention during labour and delivery, with a major influence of parity.

Self powered pH sensor using piezoelectric composite worm structures derived by ionotropic gelation approach

Multifunctional biopolymer-piezoelectric composite worm structures (wavy and linear) derived by ionotropic gelation technique is fundamentally reported. Mass production of composite wavy pattern worms (CWPWs) enable high energy conversion from low frequency mechanical energy to electrical energy, tunable piezoelectricity by tailored length dependent CWPWs, weight ratio of piezoelectric nanoparticles. Interestingly we found that, the peak–peak voltage and current decreases around 87% and 71% for CWPW devices when the CWPWs length decreased to 56.4% (L=1.95 to 0.85cm) respectively. We also tested, the pH dependent conductivity of composite linear worm (CLW) for clinical, food monitoring applications. Next, we demonstrate the generated piezoelectric potential of CWPW device holds as a promising independent power source unit to drive the CLW sensor under different pH solutions. The proposed work is non-invasive, flexible with robustness in long-term effective usage, biocompatibility, and battery-less operation for self powered biosensor in theranostics, blood pH measurement.

Comparative evaluation between ascorbic acid and N-acetyl cysteine for preventing tourniquet induced ischaemic reperfusion injury during lower limb surgery, a randomized controlled trial

BackgroundDuring tourniquet induced ischemic reperfusion, reactive oxygen species and cytokines appear and cause cellular damage and remote tissue injury.AimTo compare the effects of preoperative intravenous infusion of N-acetyl cysteine or ascorbic acid on the production of malonyldialdehyde as a marker of oxidative stress and IL-6 and IL-8 as markers of systemic inflammation after ischemic reperfusion as primary outcomes. Also both agents were compared regarding post-deflation hemodynamic effects and post-deflation changes in arterial pH and lactic acid as secondary outcomes.Patient and methods60 patients, scheduled for unilateral lower extremity surgery with a pneumatic tourniquet, were included. The study was designed as a randomized controlled parallel arms superiority trial. Baseline collection of blood samples was done and then patients were randomly classified into three groups: Group A; received 1 g Ascorbic acid, group N; received 10 mg/kg NAC and group C (control group): received 100 ml saline infusion. Epidural anesthesia was administrated. Two blood samples were drawn at each assessment time. One sample for arterial blood pH and lactic acid measurement and the other blood sample was centrifuged and stored at −20 °C for subsequent analysis of MDA, IL-6 and IL-8.ResultsLevels of MDA, IL-6, and IL-8 were significantly increased in group C after tourniquet release compared with the baseline. In groups A and N, MDA did not increase over baseline values, but IL-6 and IL-8 levels were increased and their levels were significantly less than in the control group. Changes in hemodynamics, pH and serum lactate were more evident in group C than groups A and N.ConclusionBoth N-acetyl cysteine and ascorbic acid reduce post-deflation increase in blood levels of markers of oxidative stress and markers of systemic inflammation and thus both are beneficial in preventing post-tourniquet deflation ischemic reperfusion injury in lower limb surgery.

Validation of the i-STAT system for the analysis of blood gases and acid-base status in juvenile sandbar shark (Carcharhinus plumbeus).

Accurate measurements of blood gases and acid-base status require an array of sophisticated laboratory equipment that is typically not available during field research; such is the case for many studies on the stress physiology, ecology and conservation of elasmobranch fish species. Consequently, researchers have adopted portable clinical analysers that were developed for the analysis of human blood characteristics, but often without thoroughly validating these systems for their use on fish. The aim of our study was to test the suitability of the i-STAT system, the most commonly used portable clinical analyser in studies on fish, for analysing blood gases and acid-base status in elasmobranchs, over a broad range of conditions and using the sandbar shark (Carcharhinus plumbeus) as a model organism. Our results indicate that the i-STAT system can generate useful measurements of whole blood pH, and the use of appropriate correction factors may increase the accuracy of results. The i-STAT system was, however, unable to generate reliable results for measurements of partial pressure of oxygen (PO2) and the derived parameter of haemoglobin O2 saturation. This is probably due to the effect of a closed-system temperature change on PO2 within the i-STAT cartridge and the fact that the temperature correction algorithms used by i-STAT assume a human temperature dependency of haemoglobin-O2 binding; in many ectotherms, this assumption will lead to equivocal i-STAT PO2 results. The in vivo partial pressure of CO2 (PCO2) in resting sandbar sharks is probably below the detection limit for PCO2 in the i-STAT system, and the measurement of higher PCO2 tensions was associated with a large measurement error. In agreement with previous work, our results indicate that the i-STAT system can generate useful data on whole blood pH in fishes, but not blood gases.

The specific morphological and biochemical features of inhalation poisoning with ammonia

This experimental study using the laboratory animals (rats and rabbits) has demonstrated the morphological and biochemical changes associated with inhalation poisoning with ammonia. Certain regular features of this form of intoxication were revealed. Specifically, the determination of the major biochemical characteristics of blood makes it possible to evaluate the performance of the hepatobiliary and cardiovascular systems. The results of blood pH measurement give evidence of its alkalinization.

Osmoregulatory bicarbonate secretion exploits H(+)-sensitive haemoglobins to autoregulate intestinal O2 delivery in euryhaline teleosts.

Marine teleost fish secrete bicarbonate (HCO3 −) into the intestine to aid osmoregulation and limit Ca2+ uptake by carbonate precipitation. Intestinal HCO3 − secretion is associated with an equimolar transport of protons (H+) into the blood, both being proportional to environmental salinity. We hypothesized that the H+-sensitive haemoglobin (Hb) system of seawater teleosts could be exploited via the Bohr and/or Root effects (reduced Hb-O2 affinity and/or capacity with decreasing pH) to improve O2 delivery to intestinal cells during high metabolic demand associated with osmoregulation. To test this, we characterized H+ equilibria and gas exchange properties of European flounder (Platichthys flesus) haemoglobin and constructed a model incorporating these values, intestinal blood flow rates and arterial–venous acidification at three different environmental salinities (33, 60 and 90). The model suggested red blood cell pH (pHi) during passage through intestinal capillaries could be reduced by 0.14–0.33 units (depending on external salinity) which is sufficient to activate the Bohr effect (Bohr coefficient of −0.63), and perhaps even the Root effect, and enhance tissue O2 delivery by up to 42 % without changing blood flow. In vivo measurements of intestinal venous blood pH were not possible in flounder but were in seawater-acclimated rainbow trout which confirmed a blood acidification of no less than 0.2 units (equivalent to −0.12 for pHi). When using trout-specific values for the model variables, predicted values were consistent with measured in vivo values, further supporting the model. Thus this system is an elegant example of autoregulation: as the need for costly osmoregulatory processes (including HCO3 − secretion) increases at higher environmental salinity, so does the enhancement of O2 delivery to the intestine via a localized acidosis and the Bohr (and possibly Root) effect.

A critical evaluation of automated blood gas measurements in comparative respiratory physiology

Precise measurements of blood gases and pH are of pivotal importance to respiratory physiology. However, the traditional electrodes that could be calibrated and maintained at the same temperature as the experimental animal are increasingly being replaced by new automated blood gas analyzers. These are typically designed for clinical use and automatically heat the blood sample to 37°C for measurements. While most blood gas analyzers allow for temperature corrections of the measurements, the underlying algorithms are based on temperature-effects for human blood, and any discrepancies in the temperature dependency between the blood sample from a given species and human samples will bias measurements. In this study we review the effects of temperature on blood gases and pH and evaluate the performance of an automated blood gas analyzer (GEM Premier 3500). Whole blood obtained from pythons and freshwater turtles was equilibrated in rotating Eschweiler tonometers to a variety of known PO2's and PCO2's in gas mixtures prepared by Wösthoff gas mixing pumps and blood samples were measured immediately on the GEM Premier 3500. The pH measurements were compared to measurements using a Radiometer BMS glass capillary pH electrode kept and calibrated at the experimental temperature. We show that while the blood gas analyzer provides reliable temperature-corrections for PCO2 and pH, PO2 measurements were substantially biased. This was in agreement with the theoretical considerations and emphasizes the need for critical calibrations/corrections when using automated blood gas analyzers.

Immobility reaction at birth in newborn infant

ObjectiveTo describe an immobility reaction (IR) that was not previously reported at or immediately after birth in human newborns. MethodWe analyzed 31 videos of normal term vaginal deliveries recorded from Time 0 of birth defined as the as the moment that lies between the birth of the thorax and the pelvis of the infant. We searched for perinatal factors associated with newborn's IR. ResultsIR at birth was observed in 8 of the 31 newborns. The main features of their behavior were immobilization, frozen face, shallow breathing and bradycardia. One of the 8 newborns had sudden collapse 2h after birth. We found significant relationships between maternal prenatal stress (PS) and IR (p=.037), and a close to significant one between infants’ lividness at Time 0 and IR (p=.053). The first breath of the 31 newborns occurred before and was not associated with the first cry (p<.001). DiscussionThe main features of IR at birth are similar to those of the universal most severe response to severe stress or danger. The relationship with PS suggests that children who had IR at birth might be at risk for similar disorders as those associated with PS. Sudden neonatal collapse of one of the IR newborns needs further research to determine if they are at risk for sudden infant death syndrome. ConclusionThis first report of an IR reaction at birth in human infants could open up new paths for improving early neonatal care. Further research is needed for maternal PS, stress hormones, umbilical cord blood pH measurements in IR newborns. The challenge of education and support for parents of IR newborns is outlined.

Correlation of Glucose Methodologies

The authors evaluated a new analyzer, Radiometer ABL 90 (Radiometer America, Inc, Westlake, OH), for use at the point of care in the neonatal intensive care unit for the measurement of blood gases, pH, electrolytes, ionized calcium, glucose, and lactate. In addition to correlation with the core laboratory blood gas analyzers, the instrument was compared with the NOVA StatStrip glucose meter (Waltham, MA) because the meter is in use in the neonatal intensive care unit for stand-alone glucose measurements. Twenty-four whole blood samples, ranging in glucose concentration between 12 and 777 mg/dL, as determined on the ABL 90, were analyzed, and results were compared. Statistical analysis showed excellent agreement between the blood gas glucose result and the NOVA glucose meter, ensuring little to no bias between the instruments.