Blood Acid-base Status Research Articles

Greater Fatigue During Repeated-Sprint Exercise with Shortened Recovery is not Associated with Changes in Systemic Acid-Base Balance

Repeated-sprint activity leads to a decline in mechanical performance (power output), a phenomenon called muscle fatigue. Changes in acid-base status (i.e., metabolic acidosis) have previously been suggested to contribute to fatigue during repeated-sprint exercise. One way to test this hypothesis would be to determine if differences in fatigue, as a result of different repeated-sprint protocols, could be explained by differences in acid-base status. PURPOSE: The present study investigated the effects of varying the recovery time between consecutive sprints on repeated-sprint exercise performance and possible contributing mechanisms. METHODS: Eight young men completed two trials of 18, 4-s cycling sprints, in a random order, on two occasions. In one trial the exercise protocol consisted of 3 sets of 6 sprints separated by 20-s passive recovery intervals. Between each set of sprints subjects rested for 180 s (short recovery protocol; SRP). In the second trial, the exercise protocol consisted of 6 sets of 3 sprints, also separated by 20-s passive recovery intervals. Between each set of sprints subjects rested for 180 s (long recovery protocol; LRP). RESULTS: Relative to the first sprint, PPO decreased more during the SRP compared with LRP over the first 6 sprints (16.1% vs. 8.2%; P = 0.03), 12 sprints (19.4% vs. 11.8%; P = 0.05), and 18 sprints (23.3% vs. 11.7%; P = 0.004). Similarly, the decrease in TW was higher in SRP compared with LRP at any time point (10.1% – 12.6%; P = 0.01–0.003). Relative to the LRP, the SRP trial resulted in a substantial decrease in total work after sprint 6(−6.1%;P=0.002), sprint 12 (−6.2%; P=0.002) and sprint 18 (−7.4%; P=0.003). Despite these differences in repeated-sprint exercise performance, changes in blood acid-base status (pH, lactate, HCO3-), cardiovascular load (heart rate) and rating of perceived exertion (RPE) did not differ between the two conditions at any time point (i.e., rest, sprint 6, sprint 12 and sprint 18). CONCLUSION: Differences in repeated-sprint exercise performance, associated with the reduction of the available rest time between sprints, could not be explained by acute changes in systemic acid-base status.

Changing Dietary Cation-Anion Difference for Dairy Cows Fed with Two Contrasting Levels of Concentrate in Diets

High-producing dairy cows are commonly fed diets containing a high proportion of rapidly degradable starch, which can cause subacute acidosis and reduce dry matter (DM) intake. Because of the properties of nonmetabolizable cations and anions, increasing the dietary cation-anion difference (DCAD = Na + K−Cl−S in mEq/kg of DM) may prevent a drop in DM intake. To test this hypothesis, 48 Holstein cows were blocked into 2 groups of 24 and assigned to two 3×3 Latin squares in a split-plot design. Each group received one level of concentrate at either 20% or 40% on a dry matter (DM) basis. The diet containing 20% concentrate was formulated to supply 4% rapidly degradable starch, whereas the diet containing 40% concentrate supplied 22% rapidly degradable starch. Diets in each square were formulated to provide a DCAD of 0, 150, or 300 mEq/kg of DM. The 3 values were obtained by manipulating Na and Cl contents. Intake, 4% fat-corrected milk yield, and milk fat percentage, as well as blood nonesterified fatty acids and β-hydroxybutyrate increased with DCAD, but only on the diet providing 40% concentrate. The yield of trans-10C18:1 and odd-chain fatty acids decreased with increasing DCAD, whereas trans-11C18:1 increased. Again, this occurred only with the diet providing 40% concentrate. Blood pH and HCO3 concentration increased along with DCAD, irrespective of the concentrate level. A positive DCAD led to increasing DM intake and fat-corrected milk yield in dairy cows fed highly degradable diets. The mechanism involved may be a localized rumen buffering effect, together with the ability of positive DCAD to maintain blood acid-base status in cows faced with a massive acid input.

An investigation of the role of carbonic anhydrase in aquatic and aerial gas transfer in the African lungfishProtopterus dolloi

Experiments were performed on bimodally breathing African lungfish Protopterus dolloi to examine the effects of inhibition of extracellular vs total (extracellular and intracellular) carbonic anhydrase (CA) activity on pulmonary and branchial/cutaneous gas transfer. In contrast to previous studies on Protopterus, which showed that the vast majority of CO(2) is excreted into the water through the gill and/or skin whereas O(2) uptake largely occurs via the lung, P. dolloi appeared to use the lung for the bulk of both O(2) uptake (91.0+/-2.9%) and CO(2) excretion (76.0+/-6.6%). In support of the lung as the more important site of CO(2) transfer, aerial hypercapnia (P(CO(2))=40 mmHg) caused a significant rise in partial pressure of arterial blood CO(2) (Pa(CO(2))) whereas a similar degree of aquatic hypercapnia was without effect on Pa(CO(2)). Intravascular injection of low levels (1.2 mg kg(-1)) of the slowly permanent CA inhibitor, benzolamide, was without effect on red blood cell CA activity after 30 min, thus confirming its suitability as a short-term selective inhibitor of extracellular CA. Benzolamide treatment did not affect CO(2) excretion, blood acid-base status or any other measured variable within the 30 min measurement period. Injection of the permeant CA inhibitor acetazolamide (30 mg kg(-1)) resulted in the complete inhibition of red cell CA activity within 10 min. However, CO(2) excretion (measured for 2 h after injection) and arterial blood acid-base status (assessed for 24 h after injection) were unaffected by acetazolamide treatment. Intra-arterial injection of bovine CA (2 mg kg(-1)) caused a significant increase in overall CO(2) excretion (from 0.41+/-0.03 to 0.58+/-0.03 mmol kg(-1) h(-1)) and an increase in air breathing frequency (from 19.0+/-1.3 to 24.7+/-1.8 breaths min(-1)) that was accompanied by a slight, but significant, reduction in Pa(CO(2)) (from 21.6+/-1.6 to 19.6+/-1.8 mmHg). The findings of this study are significant because they (i) demonstrate that, unlike in other species of African lungfish that have been examined, the gill/skin is not the major route of CO(2) excretion in P. dolloi, and (ii) suggest that CO(2) excretion in Protopterus may be less reliant on carbonic anhydrase than in most other fish species.

Placental Compared with Umbilical Cord Blood to Assess Fetal Blood Gas and Acid-Base Status

Placental Compared with Umbilical Cord Blood to Assess Fetal Blood Gas and Acid-Base Status

Cord blood thyroid-stimulating hormone level and risk of acidosis at birth

Objective Cord blood thyroid-stimulating hormone level is elevated in neonates who had undergone more perinatal stresses. The present study aimed to evaluate the cord blood acid–base status in neonates with elevated thyroid-stimulating hormone level. Study design The study population consisted of 2366 singleton, term pregnancies. Subjects were categorized by their cord blood thyroid-stimulating hormone level into four quartiles, and cord blood acid–base parameters were compared among the four groups. The correlations between cord acid–base parameters and thyroid-stimulating hormone level were also studied. Results Cord blood pH was significantly lower in the highest (arterial, 7.27 ± 0.08; venous, 7.32 ± 0.07) and second highest thyroid-stimulating hormone quartile groups (arterial, 7.29 ± 0.07; venous, 7.34 ± 0.06) compared to the lowest quartile group (arterial, 7.30 ± 0.06; venous, 7.35 ± 0.05). Incidences of cord arterial pH ≤7.20 were 4.7%, 6.8%, 10.9%, and 17.3% in lowest to the highest thyroid-stimulating hormone quartile groups, respectively. There was a significant negative correlation between cord blood thyroid-stimulating hormone level and cord arterial and venous pH ( r = −0.26, P < 0.001). When stratified according to the mode of delivery, the negative correlations remained significant in neonates delivered vaginally and by intrapartum emergency cesarean section but not in neonates delivered by elective cesarean section. Conclusion Incidence of cord blood acidosis is significantly higher in neonates with elevated thyroid-stimulating hormone level. This findings support the postulation that stress-induced elevation of cord blood thyroid-stimulating hormone level may be mediated through intrapartum fetal hypoxia.

Food mineral composition and acid–base balance in rabbits

Alkali-rich diets are often recommended in human medicine to prevent the pathological consequences of nutritional acid load in conditions of impaired renal function. This study was undertaken in rabbits as common laboratory animals for basic medical research to explore the impact of high versus low dietary alkali intake on systemic acid-base balance and renal control in a typical herbivore. Male rabbits (2.3-4.8 kg) were kept in a metabolism cage. The 24h urine and arterial blood samples were analysed for acid-base data. The metabolic CO2 production was measured to calculate alveolar ventilation. Three randomized groups of animals were fed ad libitum with rabbit chow providing sufficient energy but variable alkali load, assessed by the ashes' cation-anion difference. The average daily nutritional alkali load (+/- SEM) was 67.1 +/- 2.2 mEq x kg(-1) (N = 58) in the group on high, 45.4 +/- 2.5 mEq x kg(-1) (N = 31) in the group on normal and 1.7 +/- 0.5 mEq x kg(-1) (N = 11) in the group on low alkali food. Respective mean arterial base excess values (BE) were 1.4 +/- 0.3 mM, 0.3 +/- 0.4 mM and 0.0 +/- 0.3 mM, being significantly higher on high alkali food (P < 0.05) than in the other groups. Arterial PCO2, alveolar ventilation and metabolic CO2 production were not significantly different between groups. On normal and high-alkali chow, an alkaline urine (pH(u) > 8.0) with 18-20 mmol x kg(-1) bicarbonate/carbonate was excreted daily, typically containing an insoluble precipitate of 35-60% carbonate. On low-alkali diet, the mean pH(u) decreased to 6.26 +/- 0.14, due to a strong reduction of daily excreted soluble bicarbonate and precipitated carbonate to 1.2 +/- 0.6 and 0.7 +/- 0.2 mmol x kg(-1), respectively. Thereby, nearly complete fractional base reabsorption of 97.8 +/- 0.7 % was reached. Herbivore nutritional alkali-load elicited large rates of renal base excretion including precipitates, to which the urinary tract of the rabbits appeared to be adapted. Dietary base variations were more accurately reflected in the urine than by the blood acid-base status. A strongly base-deficient diet exerted maximum impact on renal base saving mechanisms, implying a critical precondition for growing susceptibility to metabolic acidosis also in the rabbit.

Thyrotoxic Periodic Paralysis

Thyrotoxic periodic paralysis (TPP), a hyperthyroidism-related hypokalemia and muscle-weakening condition resulting from a sudden shift of potassium into cells, has been seen increasingly in Western countries. Failure to recognize TPP may lead to improper management. Many patients with TPP have no obvious symptoms related to hyperthyroidism. Therefore, several important clues may help in diagnosing and managing TPP: presentation in an adult male with no family history of periodic paralysis; presence of systolic hypertension, tachycardia, high QRS voltage, first-degree atrioventricular block on electrocardiography; presence of low-amplitude electrical compound muscle action potential on electromyography and no notable changes in amplitudes after low doses of epinephrinine; and typical acid-base and electrolyte findings such as normal blood acid-base state, hypokalemia with low urinary potassium excretion, hypophosphatemia associated with hypophosphaturia, and hypercalciuria. Immediate therapy with potassium chloride supplementation may foster a rapid recovery of muscle strength, but with a risk of rebound hyperkalemia. Nonselective beta-blockers may provide an alternative choice. Long-term therapy with definite control of hyperthyroidism completely abolishes attacks. Early diagnosis and prompt treatment of TPP prevent life-threatening complications of this treatable and curable disorder.

Effects of handling intensity and live weight on blood acid-base status in finishing pigs.

The objective of this study was to determine the effect of live weight on the plasma acid-base response of pigs subjected to various handling intensities. Eighty pigs (equal numbers of barrows and gilts) were used in a completely randomized block design with a 2 x 2 x 2 factorial arrangement of the following treatments: 1) live weight (light [104 kg] vs. heavy [128 kg]), 2) handling intensity (low vs. high), and 3) gender (barrows vs. gilts). Before the handling test, pigs were weighed, venous blood samples were taken to establish baseline levels, and rectal temperature was measured. Pigs were allowed to rest for 2 h before being subjected to the handling treatments, which consisted of moving the pigs through a course (12.2 m long x 0.91 m wide), for a total of eight laps. Animals on the high-intensity treatment were moved rapidly through the course and subjected to a total of 16 single shocks (two shocks per lap) with an electric livestock goad, whereas pigs on the low-intensity treatment were moved at their own pace using a moving panel and a paddle. Rectal temperature and a venous blood sample were taken immediately after handling and at 2 h after handling. Blood plasma was assayed for pH, partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2), saturated oxygen (SO2), total carbon dioxide (TCO2), bicarbonate (HCO3), base excess, and lactate. Live weight had no effect on the baseline measurements. After handling, light pigs had higher (P < 0.05) blood SO2 (65.6 vs. 57.2+/-2.80%) and showed a greater (P < 0.05) increase in PO2 from baseline to post-handling than heavy pigs (15.6 vs. 8.3+/-2.63 mmHg). Post-handling, pigs on the high- compared with the low-intensity handling treatment had greater (P < 0.001) lactate (19.1 vs. 4.9+/-0.56 mmol/L) and PO2 (51.6 vs. 36.5+/-2.44 mmHg) with lower (P < 0.001) TCO2 (18.6 vs. 34.7+/-0.64 mmol/L), pH (7.02 vs. 7.36+/-0.015), HCO3 (16.7 vs. 33.0+/-0.62 mmol/L), and base excess (-14.2 vs. 7.5+/-0.75) values. There were no effects of gender on blood measurements or rectal temperatures. Results from this study highlight a major effect of pig handling intensity, a limited effect of live weight, and no effect of gender on blood acid-base responses to handling.

Cord blood acid-base status at delivery after successful external cephalic version.

This study was designed to evaluate whether cord blood acidosis is more likely in infants born after successful external cephalic version. This retrospective cohort study included 89 singleton deliveries with successful version performed over a 2-year period. Their cord blood acid-base parameters were compared to 89 pregnancies with spontaneous cephalic presentation (control group). There was no significant difference between the version and control groups in birthweight and Apgar scores. There was no difference between the version and control groups in cord arterial pH (7.26 vs. 7.26), arterial pCO(2) (7.04 vs. 7.09 kPa), arterial pO(2) (2.34 vs. 2.59 kPa), arterial base excess (-5.59 vs. -5.64 mmol/L), venous pH (7.32 vs. 7.33), venous pCO(2) (5.73 vs. 5.63 kPa), venous pO(2) (3.86 vs. 3.84 kPa), or venous base excess (-5.03 vs. -5.12 mmol/L). There was also no significant difference in the number of fetuses with cord arterial pH <7.20 between the two groups. Neonates delivered after successful external cephalic version are not more likely to be born with acidosis. Our study provides further support for the safety of external cephalic version for term breech pregnancies.

Cord blood acid-base status at delivery after successful external cephalic version

Cord blood acid-base status at delivery after successful external cephalic version

Combined ACTH and glucocorticoid treatment improves survival and organ maturation in premature newborn calves

Glucocorticoids play an important role in prenatal organ maturation in many species. In humans, maternal treatment with synthetic glucocorticoids improves neonatal adaptation of prematurely born infants. In cows, pre-term calf survival is improved following a single maternal glucocorticoid administration. We hypothesized that stimulation of endogenous cortisol secretion by adrenocorticotropin (ACTH) treatment combined with maternal dexamethasone treatment, would be even more efficient in stimulating organ maturation in the prematurely delivered calf. Three groups of premature calves were delivered by caesarian section at 90% of gestation length from dams which were either untreated or injected with dexamethasone before delivery, combined with either prenatal or postnatal ACTH treatment to the calf. During the first 24 h after birth, thermoregulation, blood chemistry, liver values and organ weights were recorded. In the untreated calves, survival was significantly correlated with blood oxygenation, sodium and calcium levels at the moment of birth. There were marked maturational effects of the treatments on body temperature regulation, blood acid-base status, oxygenation, glucose, insulin, IGF-1 levels, weight of the heart, liver, gastrointestinal tract and thymus weight. For many of the measured metabolic, endocrine and organ weight parameters, the intrauterine ACTH treatment was associated with improved values relative to the postnatal ACTH treatment, which appeared to have no immediate effect on calf viability. In conclusion, the premature calf delivered by caesarian section at 90% of gestation length showed blood chemistry, metabolic, endocrine and organ growth characteristics that indicated severe prematurity. However, the maturation of organ function in newborn premature calves following maternal glucocorticoid injections was further enhanced if is was preceded by intra-fetal injections of ACTH.

Ruminal fermentative parameters and blood acido-basic balance changes during the onset and recovery of induced latent acidosis in sheep

Four ruminal cannulated Texel wethers were used to study the long-term effects of an acidotic diet on ruminal parameters and blood acid-base status. The short-term events around feeding and the recovery of the animals were followed after this nutritional disturbance. Sheep were limit-fed consecutively a control diet H (100% hay) (one week), an acidotic diet W (60% wheat + 40% hay) (2 weeks), and again the control diet (2 weeks). Mean, minimum and maximum ruminal pH were lower, and the time and area under pH 6.0 were higher (P 0.05). All ruminal parameters, except for ammonia, recovered to initial levels during the H diet redistribution (P < 0.05) while blood parameters decreased (pH, P < 0.05; bicarbonates (HCO3 - ), total CO2 content (TCO2), base excess in whole blood (Beb) and in extra cellular fluid (Beecf), P < 0.01). This decrease, initiated during the distribution of the acidotic diet, suggests a mobilization of body alkaline reserves and a longer recovery time in blood than in the rumen. We observed a non-lactic but butyric latent acidosis, linked to Entodiniomorph proliferation, suggesting an intermediate stage before the onset of acute lactic acidosis.

Vaginal breech delivery: is it still an option?

Objective: To provide local data on term breech delivery for future guidance. Study design: Retrospective, ‘intended-mode-of-delivery’ analysis of 711 antenatally uncomplicated singleton breech deliveries at ≥37 weeks: 445 (63%) planned for vaginal delivery (VD) (no fetal growth restriction, fetal weight 2000–4000 g, adequate pelvic size, maternal consent) and 266 for cesarean section (CS). Outcome measures: Apgar score, cord blood acid–base status, childhood deaths and disability. Results: Perinatal mortality was nil in both groups. Low 1-min Apgar scores and low arterial cord blood pH were significantly more frequent in planned VD, but not low Apgar scores at 5 or 10 min or low venous pH. Metabolic acidosis, neonatal intensive care, neonatal seizures, birth trauma, childhood death (CS=1), and neurodevelopmental handicaps (CS=2, VD=1) were equally common. Conclusion: Our results do not disqualify selective vaginal breech delivery at term and beyond as an option.

Buffer administration during CPR promotes cerebral reperfusion after return of spontaneous circulation and mitigates post-resuscitation cerebral acidosis

To explore the effects of alkaline buffers on cerebral perfusion and cerebral acidosis during and after cardiopulmonary resuscitation (CPR), 45 anaesthetized piglets were studied. The animals were subjected to 5 min non-interventional circulatory arrest followed by 7 min closed chest CPR and received either 1 mmol/kg of sodium bicarbonate, 1 mmol/kg of tris buffer mixture, or the same volume of saline ( n=15 in all groups), adrenaline (epinephrine) boluses and finally external defibrillatory shocks. Systemic haemodynamic variables, cerebral cortical blood flow, arterial, mixed venous, and internal jugular bulb blood acid–base status and blood gases as well as cerebral tissue pH and PCO 2 were monitored. Cerebral tissue acidosis was recorded much earlier than arterial acidaemia. After restoration of spontaneous circulation, during and after temporary arterial hypotension, pH in internal jugular bulb blood and in cerebral tissue as well as cerebral cortical blood flow was lower after saline than in animals receiving alkaline buffer. Buffer administration during CPR promoted cerebral cortical reperfusion and mitigated subsequent post-resuscitation cerebral acidosis during lower blood pressure and flow in the reperfusion phase. The arterial alkalosis often noticed during CPR after the administration of alkaline buffers was caused by low systemic blood flow, which also results in poor outcome.

Relationship between meat quality and blood acid-base measurements in pigs

Pale soft exudative pork (PSE) is a major problem affecting swine industries worldwide that results in significant economic loss because it reduces processing and saleable product yields. The PSE condition results from a rapid rate of muscle glycolysis early postmortem and a rapid drop in muscle pH while the temperature of the carcass is still high. Stress prior to slaughter can increase the rate of glycolysis and postmortem acidification. Blood acid-base has been used as an indicator of stress in pigs. The objective of this experiment was to investigate the relationship between blood acid-base status at slaughter and fresh meat quality in pigs.

History of nutrition and acid-base physiology.

In the 17th century the notion of nutrition and diet changed in northern European countries. First chemical experiments fostered the idea that salts resulted from a union of acids and bases. Digestion was no more regarded as a process of cooking but a succession of fermentations controlled by a balanced production of acids and alkali. Life seemed to depend on the equilibrium of acids and alkalis. In the 19th century food was systematically analysed for the content of energy and macronutrients and first scientifically based nutritional standards were formulated. The preferred use of processed food from the new food industry resulted in epidemics of nutritional disorders. Acidosis seemed to be a plausible pathogenic factor. Practitioners (S Ishizuka, H Hay, FX Mayr) formulated holistic doctrines integrating the concept of balance of acids and bases and recommending food with an excess of alkali. New micromethods to determine the concentration of electrolytes and blood acid-base status promoted physiological and clinical research into acid-base metabolism in the 1960s. In the new physiologically based terminology of systemic acid-base status, the relationship between blood acid-base status and net acid intake or excretion was, however, incorrectly simplified. In the 1970s metabolic acidosis was observed in patients on chemically defined diets and parenteral nutrition. Based on the data of comprehensive acid-base balance studies, calculation models were used to estimate renal net acid excretion from nutrient intake and to predict the potential renal acid load of single foods. Extrapolating current trends to the future, one can say that acid-base physiology will probably remain a challenge in nutrition and functional medicine over the next few years. The challenge will include new concepts for the manipulation of nutritional acid load in sports, dietetics and preventive medicine as well as new definitions of the upper intake level of potential renal acid load in functional foods and the monitoring of renal net acid excretion in populations.

Acute Heat Stress-Induced Alterations in Blood Acid-Base Status and Skeletal Muscle Membrane Integrity in Broiler Chickens at Two Ages: Implications for Meat Quality

The effects of acute heat stress (AHS) on indices of respiratory thermoregulation and skeletal muscle damage (myopathy) were examined in broiler chickens at two ages (35 and 63 d of age); the relationships of these responses with changes in meat quality were assessed. Exposure to AHS significantly increased deep-body temperatures, panting-induced acid/base disturbances, and plasma creatine kinase (CK) activities, reflecting heat stress-induced myopathy (HSIM). The extent of the hyperthermia and disturbances in acid/base status and myopathy was significantly (P < 0.05) higher in the older birds. Consistent with AHS-induced alterations in thermoregulatory indices and muscle membrane integrity were changes in breast muscle glycolytic metabolism as indicated by lower muscle pH immediately postslaughter (pHi), increased water loss, and increased incidence of breast muscle hemorrhages. Values of pHi were lower and hemorrhage scores greater in the AHS birds at 63 d; drip losses were significantly higher in the 35-d-old birds. Exposure to AHS did not affect breast meat eating quality, although overall reductions in flavor attributes were observed in the older birds. We concluded that exposure to AHS induced disturbances in blood acid/base status and had a detrimental effect upon skeletal muscle membrane integrity. Muscle from broilers exhibited an increased sensitivity to AHS exposure with age. Alterations in antemortem blood acid/base status and muscle membrane integrity induced by AHS were associated (though not necessarily causally) with adverse effects upon breast meat quality. It is recommended that preslaughter exposure of broiler chickens to AHS should be avoided in order to reduce alterations in muscle metabolism and membrane integrity and undesirable meat characteristics.

Lipid peroxidation, antioxidant defence and acid-base status in cord blood at birth: the influence of diabetes.

Pregnancy complicated by poor control of diabetes is associated with a higher risk of embryopathies, spontaneous abortions and perinatal mortality. A number of authors suggest an involvement of reactive oxygen species (ROS) in diabetic pregnancy. Determining lipid peroxidation products (LP), scavenging enzyme activities and the umbilical cord blood's acid-base balance may contribute to an adequate diagnosis of the neonate at birth. Nevertheless, such measurements seem to have limited value in practical clinical routine. The present study evaluates LP, antioxidant defence and acid-base status related to diabetic pregnancy. Twenty-eight women with type 1 diabetes (PGDM), 19 with gestational diabetes (GDM) and 13 control cases were investigated. An additional control group consisted of 15 healthy patients with negative diabetic history; all women underwent vaginal delivery. Immediately after delivery cord blood samples and placental tissue were collected for malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) determination. Additionally, pH, pCO2, pO2 and base excess were measured in both vessels and compared to identify and exclude double venous samples. MDA levels in both cord blood and placental homogenates were significantly higher in both pregestational and gestational diabetic groups, but SOD activity was significantly diminished. Cord blood GSH was markedly elevated in PGDM and GDM. We have also shown significant differences in acid-base parameters in infants of PGDM group. Statistical analysis was performed using the Mann-Whitney U-test. These findings indicate an excessive oxidative stress in pregnancy complicated by diabetes mellitus. Evaluating LP products and scavenging enzyme activities may be valuable, sensitive indexes of fetal/neonatal threat in diabetic pregnancy in humans. Since oxidative stress is an important pathway for fetal injury, we believe that obtaining adequate measurements at the time of birth would contribute to clarifying the fetal/neonatal status in a medical and legal context and might be of value in altering therapy in newborn infants.

Accuracy of base excess--an in vitro evaluation of the Van Slyke equation.

To evaluate the precision, bias and CO2 invariance of base excess as determined by the Van Slyke equation over a wide P(CO2) range at normal and low hemoglobin concentrations. Prospective in vitro study. University research laboratory. Normal human blood, both undiluted and diluted with plasma. Two experiments were conducted. In the first, blood unmodified or after adding HCl or sodium bicarbonate was rendered hypercarbic (P(CO2) >70 torr) by gas equilibration. Rapid Pco2 reduction in > or =10 steps to a final P(CO2) < or =20 torr was then performed. In the second experiment, blood unmodified or diluted to a hemoglobin concentration of approximately 4 G% was mixed anaerobically (9:1, vol:vol) with varying concentrations of lactic acid in saline (0-250 mmol/L). In the first experiment, blood gas analysis at each step during the progressive P(CO2) reduction revealed that base excess remained nearly constant (SD all specimens < or =0.6 mmol/L) whereas P(CO2) changed by >80 torr. In the second experiment, simultaneous blood gas and plasma lactate analyses showed that changes in base excess correlated closely with changes in both plasma and whole blood lactate concentrations (r2 > or = 0.91) despite concurrent P(CO2) elevations as great as 200 torr. Quantification by base excess of change in whole blood lactate concentration was precise with slight negative bias (mean negative bias, 1.1+/-1.9 mmol/L) in both diluted and undiluted blood. There was significant underestimation of change in plasma lactate concentration in undiluted blood, presumably because base excess is a whole blood variable. Base excess calculated using the Van Slyke equation accurately quantifies metabolic (nonrespiratory) acid-base status in blood in vitro. This accuracy is little affected by large simultaneous alterations in P(CO2), or by very low hemoglobin concentrations similar to that used to calculate standard base excess.

Lipid peroxidation in umbilical arterial blood at birth: the effects of breech delivery.

To determine oxygen free radical activity in breech presentation at birth and relate it to umbilical cord blood acid-base status. A series of 63 singleton deliveries (28 cephalic deliveries as controls), 23 breech deliveries with normoacidemia, and 12 breech deliveries with mild acidaemia) had determination of malondialdehyde and acid-base parameters. The delivery suite in the Department of Obstetrics and Gynaecology at the Süleyman Demirel University, Isparta, Turkey. Sixty-three singleton infants born at term with spontaneous or induced labour and initially normal fetal heart rate tracing. After delivery, umbilical cord arterial and venous blood samples were collected for the determination of malondialdehyde concentrations. Oxygen saturation, pO2, pCO2, pH, and base excess were also measured. Umbilical cord arterial and venous blood gases and malondialdehyde levels. There was a significant correlation between umbilical arterial and venous levels of malondialdehyde and all acid-base parameters (P < 0.001). There were negative correlations between malondialdehyde levels and pH, pO2 and bicarbonate, while there was a positive correlation between malondialdehyde concentrations and pCO2. A positive correlation between malondialdehyde levels and base excess was present in the control group and total breech group (n = 35). The malondialdehyde levels in the total breech group, nonacidaemic breech group (n = 23) and the mildly acidaemic breech group (n = 12) were significantly higher than those in the control group (P < 0.0001). However, acid-base parameters in the nonacidaemic breech group were not statistically different from those in the control group. Lipid peroxidation products (malondialdehyde) existed to some extent in the umbilical cords of newborns with normal acid-base parameters in breech delivery. Our data support the contention that lipid peroxide may be a more sensitive measure for metabolic dysfunctions due to fetal hypoxia than acid-base balance.