Standard Bicarbonate Research Articles

Cardiopulmonary resuscitation: a retrospective review.

The outcome of patients admitted to intensive care after a cardiac arrest was determined by reviewing intensive care unit records at four hospitals for 1993 and 1994. Of the 112 patients identified, 49 survived intensive care of whom 28 were discharged from hospital. In January 1996, 26 of the 28 patients could be traced; 22 of these were still alive. Seven factors were significantly different between survivors and nonsurvivors. At the cardiac arrest these were the number of direct current shocks (p < 0.05) and adrenaline doses (p < 0.01) given. In intensive care the factors were the presence of reactive pupils (p < 0.01), Glasgow Coma Score (p < 0.001), APACHE II score (p < 0.05), arterial standard bicarbonate (p < 0.05) and the use of inotropes (p < 0.05). It was not possible to use individual variables to predict outcome at the time of intensive care unit admission. The results suggest that neurological function is an important determinant of outcome and more sensitive neurophysiological testing might be a useful prognostic tool.

Early increase in blood nitric oxide, detected by electron paramagnetic resonance as nitrosylhaemoglobin, in haemodialysis.

The objective of this study was to determine intradialytic blood levels of nitric oxide (NO), in patients undergoing chronic haemodialysis. This was done by detection of nitrosylhaemoglobin by a sensitive technique of spin trap electron paramagnetic resonance at 0, 5, 15, 60, 180 and 240 min of a 4-h standard bicarbonate dialysis, using the same dose (6000 U) of heparin and different dialysis membranes. The study group included 12 patients treated with cellulose-derived dialysis membranes (nine with cuprophan and three with cellulose triacetate) and 10 patients treated with synthetic membranes (five with polysulfone and five with polymethylmethacrylate). Control groups included 11 normal subjects and six patients with end-stage renal failure who were receiving intermittent peritoneal dialysis. Basal blood levels of nitrosylhaemoglobin in haemodialysis patients were significantly higher than normals, but similar to peritoneal dialysis patients. A significant increase (P < 0.01) in nitrosylhaemoglobin level was detected at 15 min of haemodialysis irrespective of the membrane used. A decrease to basal levels at 180 min was observed in all but two cuprophan-treated patients who, in contrast to the others, had a symptomatic hypotension at the end of the session and a further increase in blood nitric oxide. Patients undergoing peritoneal dialysis did not show any change in blood levels of nitrosylhaemoglobin during the first 180 min of the procedure. Thus, a constant increase in nitrosylhaemoglobin levels was observed early in haemodialysis, but not in peritoneal dialysis patients. Very preliminary evidence was obtained for a role of nitric oxide in the vascular instability at the end of haemodialysis in a few patients who had hypotensive episodes.

Pathophysiology of Severe Diarrhoea and Suggested Intravenous Fluid Therapy in Calves of Different Ages Under Field Conditions

Bouda 1., 1. Doubek. M. Medina-Cruz. L. Paasch M., E. Candanosa A., R. Dvorak, V. Soska: Pathophysiology of Severe Diarrhoea and Suggested Intravenous Fluid Therapy in Calves of Different Ages under Field Conditions. Acta vet. Bmo 1997, 66: 87-94. Selected clinical and biochemical variables were studied in 2 groups of severely dehydrated. diarrhoeic calves before and after fluid therapy. Group 1 (n = 10) included calves aged 2 to 7 d, Group 2 (n = 9) calves aged 8 to 14 d. Clinical examination and blood sampling for biochemical and haematological analyses were performed in each animal before and after fluid therapy. Samples of faeces for microbiological examination were taken before intravenous (IV) rehydration. Solutions used for IV rehydration contained salts of NaC!, NaHC03, KCI and glucose in different quantities for calves in Groups 1 and 2. These rehydration solutions were infused IV at a volume of 41 to each calf during 3 hours and then followed by oral rehydration. In Group 1, rotavirus in faeces was diagnosed in 50.0 % of all calves; combined infectious agents rotavirus and Cryptosporidillm spp. occurred in 10.0 %, none of the calves had in faeces coronavirus, enterotoxigenic E. coli K99 and Salmonella spp.; that means in 40% of calves of this group no infectious agents were isolated. In Group 2, coronavirus was found in 11.1 %, combined infectious agents rota virus and Cryptosporidiwn spp. were diagnosed in 55.5%. none of the calves had enterotoxigenic E. coli K99 or Salmonella spp in faeces. Before IV rehydration diarrhoeic calves in Group 2 presented mean blood values of pH 7.12, base excess (BE) -14.72 mmolll, standard bicarbonate (SB) 9.86 mmolll which were significantly lower (P<O.OS) than in calves in Group 1 before IV rehydration, where pH was 7.16. BE -11.68 mmolll and SB 12.S4 mmolli. In both groups of calves before IV rehydration these low values of blood pH. BE. SB and normal value of pCO,. corresponded to partially compensated metabolic acidosis. The differences in blood values of pH, BE. SB. PCV. urea and K in both groups before and after rehydration were significant (P < 0.(1). The metabolic acidosis together with hyperkalemia, prerenal uremia and haemoconcentration were restored after fluid therapy. Rehydration was successful in 79.0 % of all diarrhoeic calves. Calves aged 8 d or older suffering from severe diarrhoea needed more bicarbonate for IV rehydration than diarrhoeic calves younger than 8 d. The suggested composition and volume of solutions for IV rehydration used in this study simplify fluid therapy in severely diarrhoeic calves of different ages in lateral or sternal recumbency without suckling reflex and under field conditions. Neonatal diarrhoea, dehydration. metaholic acidosis, hyperkalemia, uremia, packed cell volullle, fluid therapy, calf

The effect of low-dose acetazolamide on the ventilatory CO2 response curve in the anaesthetized cat.

1. The effect of 4 mg kg-1 acetazolamide (I.V.) on the slope (S) and intercept on the Pa,CO2 axis (B) of the ventilatory CO2 response curve of anaesthetized cats with intact or denervated carotid bodies was studied using the technique of dynamic end-tidal forcing. 2. This dose did not induce an arterial-to-end-tidal PCO2 (P(a-ET),CO2) gradient, indicating that erythrocytic carbonic anhydrase was not completely inhibited. Within the first 2 h after administration, this small dose caused only a slight decrease in mean standard bicarbonate of 1.8 and 1.7 mmol l-1 in intact (n = 7) and denervated animals (n = 7), respectively. Doses of acetazolamide larger than 4 mg kg-1 (up to 32 mg kg-1) caused a significant increase in the P(a-ET),CO2 gradient. 3. In carotid body-denervated cats, 4 mg kg-1 acetazolamide caused a decrease in the CO2 sensitivity of the central chemoreflex loop (Sc) from 1.52 +/- 0.42 to 0.96 +/- 0.32 l min-1 kPa-1 (mean +/- S.D.) while the intercept on the Pa,CO2 axis (B) decreased from 4.5 +/- 0.5 to 4.2 +/- 0.7 kPa. 4. In carotid body-intact animals, 4 mg kg-1 acetazolamide caused a decrease in the CO2 sensitivity of the peripheral chemoreflex loop (Sp) from 0.28 +/- 0.18 to 0.19 +/- 0.12 l min-1 kPa-1. Se and B decreased from 1.52 +/- 0.55 to 0.84 +/- 0.21 l min-1 kPa-1, and from 4.0 +/- 0.5 to 3.0 +/- 0.6 kPa, respectively, not significantly different from the changes encountered in the denervated animals. 5. It is argued that the effect of acetazolamide on the CO2 sensitivity of the peripheral chemoreflex loop in intact cats may be caused by a direct effect on the carotid bodies. Both in intact and in denervated animals the effects of the drug on Sc and B may not be due to a direct action on the central nervous system, but rather to an effect on cerebral vessels resulting in an altered relationship between brain blood flow and brain tissue PCO2.

Acid‐base metabolism after bladder substitution with

Objectives To assess acid‐base metabolism after bladder substitution with the ileal Kock reservoir, using capillary blood‐gas analysis, measurement of the renal excretion of ammonium and titratable acid and the evaluation of renal function by plasma clearance of 51Cr‐labelled ethylenediamine tetra‐acetic acid (51Cr‐EDTA). Patients, subjects and methods The investigation comprised both a cross‐sectional study, with initial measurements after surgery, and a longitudinal study, with pre‐operative measurements, both groups of patients being followed for 2 years after inclusion. The cross‐sectional study included 26 patients (median age 66 years, range 44–75), with a median post‐operative follow‐up of 1.2 years (range 0.3–3.7), and 16 control subjects (median age 62 years, range 34–80), and the longitudinal study comprised seven patients (median age 57 years, range 42–68). Results The median values for capillary blood pH, carbon dioxide pressure, standard bicarbonate and standard base excess were significantly lower in patients with a bladder substitute than in the control subjects. An acid‐base chart showed that the values for 44% of patients and none of the controls were within the area representing mild metabolic acidosis. This difference could not be attributed to differences in renal function because the 51Cr‐EDTA clearance was normal and similar in the two groups of patients and among patients and controls. Nevertheless, the median values for each of the variables measured by blood‐gas analysis were within the reference interval of the normal population. Net acid excretion was similar in patients with a bladder substitute and control subjects, but urinary pH was significantly higher in the patients. Accordingly, the renal excretion of ammonium was significantly higher and the excretion of titratable acid significantly lower in patients after ileal bladder substitution. Conclusions The results are consistent with the hypothesis that bladder substitution with the ileal Koch reservoir results in an acid load to the body, caused mainly by ammonium reabsorption in the reservoir. The acid load is compensated by an increased renal excretion of ammonium but causes a mild metabolic acidosis in about half the patients.

Investigation into intraerythrocytic and extraerythrocytic acid-base and electrolyte changes after long-term ammonium chloride administration in dogs

Abstract Objectives To investigate the effect of ammonium chloride-induced urine acidification on acid-base status (ABS) of blood, plasma, and erythrocytes, and to compare the diagnostic value of acid-base analysis for erythrocytes with that for blood and plasma. Design Ammonium chloride (100 mg/kg of body weight) was administered orally every 12 hours for 8 consecutive days. The ABS was determined daily in venous blood, plasma, and lysed, packed erythrocytes (erythrolysate) and in urine. In plasma and erythrocytes, concentrations of sodium (Na+) and potassium (K+) were analyzed. Animals 16 clinically normal (8 treated and 8 control) dogs. Procedure The acid-base analysis (standard pH, standard bicarbonate concentration, base excess, and carbon dioxide tension) in blood, plasma, and erythrocytes was determined by use of the CO2, O2 gas equilibration method. Determination of urine ABS (pH, concentrations of acids and bases, net acid-base excretion, and baseacid quotient) was performed by titration methods. Determination of concentrations of Na+ and K+ in erythrocytes was performed by flame photometry, and in plasma, by use of ion-specific electrodes. Results Ammonium chloride caused metabolic acidosis in blood and plasma, but no change of ABS in erythrocytes. The concentrations of K+ in plasma and erythrocytes did not change in treated dogs; however, the concentrations of Na+ in plasma and erythrocytes decreased significantly (P &lt;0.05) after ammonium chloride administration. Urinary acid excretion increased significantly (P&lt;0.05) in treated dogs; urine pH was between 4.51 and 5.49 at all times. Conclusions Ammonium chloride administration (100 mg/kg, PO, q 12 h) causes substantial blood and urine acidification but does not influence erythrocyte ABS. In this study, determination of erythrocyte ABS did not provide any additional benefit in diagnosing metabolic acidosis, compared with analysis of blood. (Am J Vet Res 1996; 57:743–749)

Metabolic alkalosis following orthotopic liver transplantation

Objective: To determine the incidence, causative factors and impact of post-operative metabolic alkalosis in liver transplant recipients. Design: Retrospective. Setting: Post-operative intensive care unit. Subjects: Eighty adult liver transplant recipients. Interventions: Arterial blood gases were assessed on post-operative days one, two and three. Endpoints: Metabolic alkalosis was defined as the presence of a standard bicarbonate level ≥ 26 mEq/l in one or more determinations. Measurements and main results: Sixty-five patients (81%) developed post-operative metabolic alkalosis (Group 1). They had required a greater transfusion of intraoperative blood (28±22 units versus 14±10 units; p<0.01) and fresh frozen plasma (38.5±27.4 units versus 17.3±7.8 units; p<0.01) than the 15 patients without metabolic alkalosis (Group 2). There were no differences in the intraoperative infusion of sodium bicarbonate, type of fluids employed to restore blood volume, type of graft preservation solution, degree of preo...

The effect of physostigmine on acid-base status in arterial and venous blood of anaesthetized rabbits following hypovolemic shock

1. 1. The effects of physostigmine (70 μg kg −1intravenously) on acid-base status in arterial and venous blood were studied in anaesthetized rabbits subjected to hemorrhagic hypovolemia. 2. 2. Hemorrhagic shock was produced using intermittent bleeding of 50% of the estimated blood volume, during 30 min. Experimental group was treated with physostigmine (70 μg kg −1 body mass, intravenously) and the control group with the same volume (0.1 ml) of saline, immediately after bleeding. Blood samples were taken before and after bleeding (0, 15 and 60 min). 3. 3. It was found that physostigmine increased the mean arterial blood pressure, did not change the heart rate, and improved survival of the animals. 4. 4. These effects of physostigmine were associated with significant decrease in venous pH, produced mainly by increased PCO 2. This can partly be explained in terms of additional vasoconstriction due to physostigmine action. 5. 5. In arterial blood decreased pH, decreased standard bicarbonate, negative values of excess base and decreased PCO 2 were observed both in physostigmine-treated and the control group of animals, indicating partly respiratory compensated metabolic acidosis. These findings indicate that the hypertensive effect of physostigmine in shock was not accompanied by more severe disturbance in arterial acid-base status than was observed in hypovolemic shock alone.

The VCO2/VO2 relationship during heavy, constant work rate exercise reflects the rate of lactic acid accumulation.

Oxygen uptake (VO2) kinetics have been reported to be modified when lactic acid accumulates; however little attention has been given to the simultaneous carbon dioxide production (VCO2) kinetics. To demonstrate how VCO2 changes as a function of VO2 when lactic acid is buffered by bicarbonate, eight healthy subjects performed 6-min constant work rate cycle ergometer exercise tests at moderate, heavy and very heavy exercise intensities. VCO2 and VO2 were measured breath-by-breath, and arterial blood samples were obtained every 7.5 s during the first 3 min of exercise, and were analyzed for pH, partial pressure of carbon dioxide, standard bicarbonate, and lactate. VCO2 abruptly increased relative to VO2 between 40 and 50 s after the start of exercise for the high exercise intensities. These gas exchange events were observed to correlate well with the time and VO2 at which lactic acid increased and plasma bicarbonate decreased (r = 0.90, r = 0.95, respectively). We conclude that bicarbonate buffering of lactic acid can be determined from the acceleration of VCO2 relative to VO2 kinetics in response to constant work rate exercise and the increase is quantitatively related to the magnitude of the lactic acid increase. This is easily visualized from a plot of VCO2 as a function of VO2.

Effects of sulfate supplementation on performance, acid-base balance, and nutrient metabolism in Angora kids

Twelve Angora goat kids (BW: mean ± SE = 18.1 + 0.6 kg; castrated males) were individually fed isonitrogenous and isocaloric diets containing 0.11 (basal), 0.20, 0.28 or 0.38% S of dietary DM (added as CaSO 4). During the 8-wk growth phase, sulfate supplementation up to 0.20% S in the diet increased average daily gain (ADG) by 44%, dry matter intake (DMI) by 17%, and feed conversion efficiency (FE, ADG/DMI) by 23% compared with average Angora kids fed the other diets. Clean mohair production was numerically highest for kids fed the 0.28% S diet, but mohair fiber diameter was not affected ( P > 0.20) by added S. Mohair staple length tended to increase quadratically ( P < 0.20) with sulfate supplementation. Average daily gain ( P < 0.05) and DMI ( P < 0.0001) were lower for Angora than for Alpine kids (70 vs. 95 g and 762 vs. 1125 g/d, respectively), but FE was higher ( P > 0.20) for Angora than Alpine kids. Plasma free cysteine was quadratically increased by S supplementation in Angora kids. Blood pH did not differ between breeds. Blood HCO 3 −, total CO 2 content, pCO 2, base excess in extra-cellular fluids, and standard bicarbonate were lower ( P < 0.05) in Angora than in Alpine kids, but blood partial pressure of O 2 and oxygen saturation were higher ( P < 0.05) in Angora than in Alpine kids, perhaps due to increased heat dissipation via respiration by Angora kids. Plasma glucose, urinary outputs of creatinine and uric acid were lower ( P < 0.05), and plasma free cysteine concentration higher ( P < 0.01) for Angora than for Alpine kids. Ruminal l-lactate concentration ( P < 0.001) and purine N content in isolated bacteria ( P < 0.01) were lower, but ruminal NH 3-N content ( P < 0.10) was higher, and ruminal sulfide-S content ( P < 0.20) tended to be higher for Angora than for Alpine kids. Angora kids were faunated, whereas Alpine kids were fauna-free. The N/S ratio in isolated rumen bacteria was lower ( P < 0.10) for Angora than for Alpine kids. Calculated by regression, ADG was maximum with 0.22% S ( N S = 10.4:1 ) for Angora kids vs. 0.21% S for Alpine kids.

Identification of Catechol‐Protein Conjugates in Neostriatal Slices Incubated with [3H]Dopamine: Impact of Ascorbic Acid and Glutathione

There is evidence to suggest that degeneration of dopaminergic neurons in Parkinson's disease and certain other conditions results from the action of reactive species generated during the oxidation of dopamine. We, therefore, have begun to explore the conditions under which such reactive species are formed. Tissue slices prepared from rat neostriatum were incubated in a standard Krebs bicarbonate buffer for up to 120 min. In the presence of [3H]dopamine (0.01-100 microM), binding of tritium to the acid-insoluble protein fraction was detected. Binding was attenuated by the addition of ascorbate (0.085-0.85 mM) or glutathione (0.01-1.0 mM) to the buffer. Acid hydrolysis of the protein revealed the presence of cysteinyl-dopamine and cysteinyl-dihydroxyphenylacetic acid residues. These results suggest that dopamine oxidizes to form reactive metabolites, presumably quinones, that then bind to nucleophilic sulfhydryl groups on protein cysteinyl residues. The findings further suggest that the extent to which reactive metabolites are formed is determined in part by the balance between the availability of dopamine and the antioxidant environment.

Effects of detomidine in young water buffalo

SUMMARY Following preliminary studies with detomidine hydrochloride in 10 young buffaloes (Bubalus bubalis), the effects of an intramuscular injection of 40 /ixg.kg −1 were studied in 6 healthy buffaloes of VA to 2 years of age, weighing between 85 and 140 kg. Arterial blood pressure, central venous pressure, heart rate, electrocardiogram, electroencephalogram, respiratory rate, arterial pH, arterial and venous blood gases and rectal temperature were monitored before, and for an hour after, intramuscular injection of detomidine. Marked ataxia and sternal recumbency occurred within 10 minutes of injection, and an apparent complete recovery occurred in about 90 minutes. The electroencephalograms never demonstrated the high-voltage-low-frequency wave forms normally associated with sedation, but the animals appeared well sedated. After injection there was marked decrease in heart rate which then tended to increase but it remained significantly (P Rectal temperature, arterial pH, arterial carbon dioxide tension, standard bicarbonate and cranial vena caval oxygen tension did not show any significant variation. Respiratory rate and arterial oxygen tension decreased significantly.

Are laboratory values in bone marrow aspirate predictable for venous blood in paediatric patients?

In an emergency situation, early laboratory results are important, but often difficult to obtain. If venous access cannot be established, the intraosseous route may be used as an alternative. This study investigated the predictive value of bone marrow aspirate in performing laboratory studies. Thirty children underwent general anaesthesia for bone marrow aspiration (iliac crest) for oncologic or haematologic reasons. The aspirate and a peripheral venous blood sample, which was obtained simultaneously, were subjected to different laboratory tests and the results were compared by means of confidence interval analyses of the individual ratios of venous/bone marrow values. Based on these analyses, a high predictability of bone marrow values were found for haemoglobin, sodium, chloride, glucose, bilirubin, urea, creatinine, pH, and standard bicarbonate. Moderate, but clinically useful predictability was found for haematocrit, potassium, and total protein, while bone marrow values of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, P co 2, P O 2, thrombocytes and leukocytes were systematically different from values in venous blood. Our data suggest that the intraosseous route is not only an important emergency alternative to intravenous access for administering fluids and drugs but may also serve as a reliable alternative for obtaining initial diagnostic laboratory studies when intravascular access is not obtainable.

Effect-kinetics on brain protection of two codergocrine-mesylate preparations (Aramexe retard® and Hydergine®) by EEG mapping and psychometry under hypoxia

In a double-blind, placebo-controlled study the effect-kinetics on brain protection of a new retard formulation of codergocrine-mesylate (CDM) (Aramexe retard®, 5 mg) were investigated and compared with a standard CDM drug (5 mg Hydergine®) utilizing blood gas analysis, EEG mapping and psychometry. A transient, reversible hypoxic hypoxidosis (i.e. impairment of cerebral metabolism due to hypoxia) was experimentally induced by a fixed gas combination of 9.8% oxygen (O 2) and 90.2% nitrogen (N 2) (found at an altitude of 6000 m), which was inhaled for 23 min under normobaric conditions by 18 healthy volunteers. After an adaptation session they received randomized 5 mg Aramexe retard, 5 mg Hydergine and placebo. Evaluation of blood gases, EEG mapping and psychometry was carried out at 0,2, 4,6, and 8 h after oral drug administration — each time under normoxic and hypoxic conditions. Blood gas analysis demonstrated a drop in SaO 2 from 99% under normoxia to 70% under hypoxia, in P o 2 from 100 to 33 mmHg, and in P co 2 from 36 to 31 mmHg, while pH increased from 7.43 to 7.48. Base excess and standard bicarbonate remained stable. Under hypoxia EEG mapping exhibited an increase in δ/θ, a decrease of α and increase of β activity, as well as a slowing of the centroid of the total power spectrum, which reflects deterioration of vigilance. Both CDM preparations significantly attenuated this vigilance decrement, with 5 mg Hydergine showing its encephalotropic peak effect in the second hour, 5 mg Aramexe retard in the sixth and eighth hours. At the behavioral level, hypoxic hypoxidosis induced a deterioration of the noo- and thymopsyche (by 53% under placebo), which was significantly mitigated by both 5 mg Aramexe retard (19%) and Hydergine (32%).

Increase of calcitriol during treatment with protein-reduced diet in patients with renal failure.

Vitamin D metabolites 25-OH-D3 (calcifediol) and 1,25-(OH)2-D3 (calcitriol) were measured in plasma in 16 patients with advanced chronic renal failure during treatment with a protein-restricted diet for 6 months. The glomerular filtration rate (GFR) decreased only marginally, from 8.3 to 7.9 ml/min, during the study while there was a significant decrease of serum urea levels after the initiation of the protein-reduced diet. Calcitriol levels rose significantly (p < 0.05) after 3 months from 17.1 to 27.7 pg/ml but fell after another 3 months to nearly their initial values, 15.3 pg/ml. The serum phosphate levels changed during the same periods from 1.99 to 1.67 to 1.93 mmol/l. There were significant inverse correlations between the calcitriol and phosphate levels at the start and after 3 months but not after 6 months. There was also a significant correlation between the changes in calcitriol and initial GFR. A subgroup of patients with decreased or unchanged calcitriol concentrations during dietary treatment had significantly higher serum phosphate and creatinine and significantly lower standard bicarbonate concentrations. Multivariate regression analysis for the pooled set of data with calcitriol as the dependent variable showed significant values for GFR (p < 0.02), body mass index (p < 0.02), and serum phosphate concentrations (p < 0.04). These results show the importance of phosphate control and renal function for the regulation of calcitriol synthesis.

Comparison of Gas Exchange, Lactate, and Lactic Acidosis Thresholds in Patients with Chronic Obstructive Pulmonary Disease

During an incremental exercise test, three consequences of the onset of anaerobic metabolism can be observed: rise in blood lactate (lactate threshold, LT); fall in standard bicarbonate (lactic acidosis threshold, LAT); nonlinear increase in CO2 output (V-slope gas exchange threshold, GET). We compared these thresholds in 31 patients with COPD. We found that the GET and LAT overestimated the LT. A better relationship was found between LAT and GET, even though GET was significantly higher than LAT (by 124 ml/min; p < 0.0001). However, since the bias is appreciably greater at lower LAT values (likely because VCO2 kinetics are slower than VO2 kinetics), we separated the studies into two groups: (A) tests where LAT occurred within the first 2 min of the increasing work rate period, and (B) tests where LAT occurred after 2 min. For Group A, there was a substantial bias between LAT and GET (323 ml/min, p < 0.0001), whereas the bias was much smaller (only 5.4%, though statistically significant) for Group B (57 ml/min, p < 0.01). We conclude that when lactic acidosis occurs after the first 2 min of incremental exercise, the GET closely approximates the point at which blood bicarbonate begins to fall.

Inspiratory muscle performance relative to the anaerobic threshold in patients with COPD

Rehabilitation programmes in chronic obstructive pulmonary disease (COPD) require exercise training above the anaerobic threshold. However, not all COPD patients develop metabolic acidosis during exercise. The hypothesis of this study was that non-exercise variables, characterizing the mechanical load on the inspiratory muscles during breathing at rest, can be used to reliably predict which patients with COPD are not able to develop metabolic acidosis during exercise. Thirty participants with COPD performed a symptom-limited cycle ergometer test. The oesophageal pressure/time index (PTIoes: the product of pressure magnitude and duration), the mean rate of pressure development during inspiration (Poes/TI), and the mean airway resistance (Raw)/maximal oesophageal pressure (Poesmax) ratio served as indices for the mechanical load on the inspiratory muscles. The oxygen uptake (VO2) at which plasma standard bicarbonate was seen to decrease from its baseline value was taken as the anaerboic threshold (AT). Mean Raw was significantly higher in those patients in whom the AT could not be detected. No other lung function parameters measured at rest allowed the accurate selection of those patients who did or did not develop exercise metabolic acidosis. On the other hand, Raw/Poesmax, PTIoes and Poes/TI were significantly different in the two patient groups. Additionally, whereas in the patient group with identifiable AT exercise hyperpnoea produced a non-linear increase of Poes/TI with respect to PTIoes above the AT, in the patient group without identifiable AT there was a linear relationship between Poes/TI and PTIoes throughout exercise. We conclude that the determination of inspiratory muscle load indices at rest may be useful in pulmonary rehabilitation programmes, for identifying those patients with COPD who do not develop exercise induced metabolic acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Normalization of uremic acidosis in hemodialysis patients with a high bicarbonate dialysate.

Uremic acidosis accompanies chronic renal failure in hemodialysis patients because of a retention of nonvolatile acids. Standard bicarbonate (39 mEq/L) and acetate (38 mEq/L) dialysates do not completely correct the acidosis. The acid-base and biochemical effect of a high-bicarbonate (42 mEq/L) dialysate was evaluated in 38 patients during high-efficiency and high-flux dialysis over 12 wk. All patients were dialyzed on standard bicarbonate dialysate before the study and for 8 wk after the study. In order to monitor potential excessive alkalosis, predialysis and postdialysis arterial blood gases were measured in seven patients who initially had a normal predialysis pH. Serum chemistries revealed no significant changes in predialysis BUN, calcium, ionized calcium, or phosphorus during the 12-wk study. There was no change in postdialysis ionized calcium or phosphorus. Predialysis and postdialysis serum total CO2 (STCO2) increased over the 12-wk study (P < 0.0001). By week 12, 75% of the hemodialysis patients had an STCO2 > 23 mEq/L and no patient had an STCO2 > 30 mEq/L predialysis. After the 8-wk washout, all chemistries were no different from prestudy concentrations. Predialysis blood gases in seven patients with normal predialysis HCO3 revealed a significant increase (P < 0.009) in PCO2 and HCO3 over the 12-wk study; predialysis pH and PO2 did not change. There was no significant change in postdialysis blood gases. It was concluded that: (1) a high-bicarbonate dialysate corrects predialysis acidosis in 75% of hemodialysis patients without causing progressive alkalemia, hypoxia, or hypercarbia; and (2) predialysis BUN, calcium, ionized calcium, and phosphorus are unaffected by high-bicarbonate dialysate.

Effects of sodium bicarbonate on cardiorespiratory measurements and exercise capacity in thoroughbred horses.

We examined the effects of sodium bicarbonate in 6 Thoroughbred horses during submaximal and maximal treadmill exercise. Cardiorespiratory function was assessed together with the effect on exercise capacity by determining the run time to fatigue at maximal intensities. To discriminate between sodium bicarbonate's alkalinising effects and the fluid shifts that could result from the high osmotic load, we administered an equimolar solution of sodium chloride as a control. The horses were given sodium bicarbonate (1 g/kg bwt) or an equivalent number of moles of sodium chloride by nasogastric tube. Arterial blood samples were collected before exercise and 5 h after treatment, resulting in mean standard bicarbonate values of 39.6 mmol/l in horses treated with sodium bicarbonate compared with 24.2 mmol/l in horses that received saline. The horses were exercised on a treadmill at 40, 60 and 80% of their VO2max for 4, 2 and 2 mins respectively. The horses were walked for 3 mins and accelerated rapidly to a speed approximately equivalent to 110% VO2max and run until fatigued. The horses ran for 170 +/- 20 secs (mean +/- sem) after administration of sodium bicarbonate compared with 128 +/- 13 secs after receiving sodium chloride (P < 0.02). At rest and throughout submaximal and maximal exercise, the bicarbonate-treated horses had significantly lower arterial oxygen tensions and higher arterial carbon dioxide tensions. There were no differences in cardiac output, heart rate, oxygen uptake or carbon dioxide production between the saline and bicarbonate treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiology of incomplete renal tubular acidosis in recurrent renal stone formers: evidence of disturbed calcium, bone and citrate metabolism.

Urinary acidification, bone metabolism and urinary excretion of calcium and citrate were evaluated in 10 recurrent stone formers with incomplete renal tubular acidosis (iRTA), 10 recurrent stone formers with normal urinary acidification (NUA) and 10 normal controls (NC). Patients with iRTA had lower plasma standard bicarbonate after fasting (P < 0.01) and lower urinary excretion of titratable acid (P < 0.05) and citrate (P < 0.01) compared with NUA patients and NC, and higher urinary excretion of ammonia (P < 0.05) compared with NC (P < 0.05). Hypercalciuria was found in 6 of 10 patients with iRTA compared with 3 of 10 with NUA, and 0 of 10 NC. The citrate/calcium ratio in urine was significantly reduced in iRTA compared with the value in NUA (P < 0.01), and in NUA compared with NC (P < 0.05). Biochemical markers of bone formation (serum osteocalcin) and bone resorption (urinary hydroxyproline) were significantly increased in iRTA compared with NUA and NC (P < 0.01), indicating increased bone turnover in stone formers with iRTA. Stone formers with iRTA thus presented with disturbed calcium, bone and citrate metabolism--the same metabolic abnormalities which characterize classic type 1 RTA. Mild non-carbonic acidosis during fasting may be a pathophysilogical factor of both nephrolithiasis and disturbed bone metabolism in stone formers with iRTA.