Kinetics of acid-base parameters in conventional hemodialysis

Details about the acid-base changes in hemodialysis are scarce in the literature but are potentially relevant to adequate management of patients. We addressed the acid-base kinetics during hemodialysis and throughout the interdialytic period in a cross-sectional study of adults undergoing conventional hemodialysis. Samples for blood gas analysis were obtained from the arterial limb of the arteriovenous fistula before the first session of the week (HD1), immediately at the end of HD1, and on sequential collections at 15, 30, 45, 60, and 120 min post-HD1. Additional blood samples were collected after ∼20 h following the end of the first dialysis and immediately prior to the initiation of the second dialysis of the week. Thirty adult patients were analyzed (55±15 years, 50% men, 23% diabetic; dialysis vintage 69±53 months). Mean serum bicarbonate levels increased at the end of HD1 (22.3±2.7 mEq/L vs 17.5±2.3 mEq/L, P<0.001) and remained stable until 20 h after the end of the session. The mean values of pCO2 before HD1 were below reference and at 60 and 120 min post-HD1 were significantly lower than at the start (31.3±2.7 mmHg and 30.9±3.7 mmHg vs 34.3±4.1 mmHg, P=0.041 and P=0.010, respectively). The only point of collection in which mean values of pCO2 were above 35 mmHg was 20 h post-dialysis. Serum bicarbonate levels remained stable for at least 20 h after the dialysis sessions, a finding that may have therapeutic implications. During dialysis, the respiratory response for correction of metabolic acidosis (i.e., pCO2 elevation) was impaired.

Kinetics of acid-base parameters in conventional hemodialysis.

Details about the acid-base changes in hemodialysis are scarce in the literature but are potentially relevant to adequate management of patients. We addressed the acid-base kinetics during hemodialysis and throughout the interdialytic period in a cross-sectional study of adults undergoing conventional hemodialysis. Samples for blood gas analysis were obtained from the arterial limb of the arteriovenous fistula before the first session of the week (HD1), immediately at the end of HD1, and on sequential collections at 15, 30, 45, 60, and 120 min post-HD1. Additional blood samples were collected after ∼20 h following the end of the first dialysis and immediately prior to the initiation of the second dialysis of the week. Thirty adult patients were analyzed (55±15 years, 50% men, 23% diabetic; dialysis vintage 69±53 months). Mean serum bicarbonate levels increased at the end of HD1 (22.3±2.7 mEq/L vs 17.5±2.3 mEq/L, P<0.001) and remained stable until 20 h after the end of the session. The mean values of pCO2 before HD1 were below reference and at 60 and 120 min post-HD1 were significantly lower than at the start (31.3±2.7 mmHg and 30.9±3.7 mmHg vs 34.3±4.1 mmHg, P=0.041 and P=0.010, respectively). The only point of collection in which mean values of pCO2 were above 35 mmHg was 20 h post-dialysis. Serum bicarbonate levels remained stable for at least 20 h after the dialysis sessions, a finding that may have therapeutic implications. During dialysis, the respiratory response for correction of metabolic acidosis (i.e., pCO2 elevation) was impaired.

Capillary Blood Ketone Levels as an Indicator of Inadequate Breast Milk Intake in the Early Neonatal Period.

OBJECTIVE: To determine the utility of capillary blood ketone levels as an indicator of inadequate intake of breast milk in the early postnatal period. STUDY DESIGN: Levels of capillary blood beta-hydroxybutyrate (ßOHB), the main ketone body in the blood, were measured with a bedside ketone meter in 585 full-term neonates aged 48-95 hours who were breastfed exclusively. Relationships between weight-loss percentage, blood sodium, glucose, pH, partial pressure of carbon dioxide, base-deficit levels, and ßOHB levels were investigated. The diagnostic accuracy of ßOHB for predicting excessive weight loss (weight loss ≥10% of birth weight) and hypernatremic dehydration (blood sodium level ≥150 mEq/L) was determined. RESULTS: ßOHB levels were correlated positively with weight-loss percentage and blood sodium levels and were correlated negatively with blood glucose levels. The diagnostic accuracy of ßOHB was 0.846 (optimal cut off, 1.55 mmol/L; sensitivity, 80.9%, specificity, 74.0%) for predicting excessive weight loss and 0.868 (optimal cut off, 1.85 mmol/L; sensitivity, 94.3%; specificity, 69.9%) for predicting hypernatremic dehydration according to the area under the receiver operating characteristic curve. Multiple logistic analysis revealed that ßOHB and weight loss percentage were the only independent predictors of hypernatremic dehydration. Increases in ßOHB levels also were associated with worsening metabolic acidosis and hypocapnia. CONCLUSION: High ßOHB levels were associated with inadequate intake of breast milk in the early postnatal period. The use of bedside capillary blood ketone levels may be clinically useful as an indicator of dehydration, energy depletion, and acid-base imbalance in breastfeeding infants in the early postnatal period.

Magnesium: the forgotten electrolyte.

UNLABELLED: Magnesium (Mg++), Potassium (K+) and Calcium (CA++) are important electrolytes in keeping a stable electrical status. The purpose of this study was to measure them in critically ill patients. METHODS: We evaluated the electrolytes in 28 consecutive patients. Eighteen were females and 10 males with mean age of 62 +/- 5 years. RESULTS: The admission diagnosis in 95% of the cases was congestive heart failure. Sixty-four percent of the patients had subnormal values of Mg++, 53% subnormal values of K+, and 28% subnormal values of CA++. Fourteen percent showed lower values of the three electrolytes and 35% only of Mg++ and K+ concomitantly. Twenty-eight percent showed prolonged QTC interval. All patients with prolonged QTC interval had low Mg++ and K+ levels. Twenty five percent of the patients showed atrial fibrillation, 25% ventricular tachycardia, and 3% junctional tachycardia. The ventricular tachycardia group had more electrolyte abnormalities than those with atrial fibrillation. None of the patients received Mg++ replacement during critical management while 50% received K+ replacement. CONCLUSION: This data shows physician overlook the Importance of Mg++ and K+ deficiency in critically ill patients.

Acid-base and electrolyte status during early induced pregnancy toxaemia in goats.

Eleven Murciano-Granadina goats in late pregnancy were separated into two groups (1) control (n=6) and (2) fasting for 72 h to induce pregnancy toxaemia (n=5). Venous blood was taken daily to determine acid-base and electrolyte parameters. Significant decreases in blood pH, bicarbonate concentration and base excess, and a significant increase in anion gap were observed after 24h of fasting. These changes were significantly correlated with non-esterified fatty acid concentration. No significant changes were observed in pCO(2), and electrolyte or lactate concentrations. Clinical signs of pregnancy toxaemia in fasted goats appeared by 72h post-fasting. These signs and the changes in acid-base balance disappeared once feed was reintroduced. Blood pH, bicarbonate concentration, base excess and anion gap could be indicators of early pregnancy toxaemia in goats.

Lactate and base deficit are predictors of mortality in critically ill patients with cancer.

OBJECTIVE: Cancer patients frequently require admission to intensive care unit. However, there are a few data regarding predictive factors for mortality in this group of patients. The aim of this study was to evaluate whether arterial lactate or standard base deficit on admission and after 24 hours can predict mortality for patients with cancer. METHODS: We evaluated 1,129 patients with severe sepsis, septic shock, or postoperative after high-risk surgery. Lactate and standard base deficit collected at admission and after 24 hours were compared between survivors and non-survivors. We evaluated whether these perfusion markers are independent predictors of mortality. RESULTS: There were 854 hospital survivors (76.5%). 24 h lactate > 1.9 mmol/L and standard base deficit < -2.3 were independent predictors of intensive care unit mortality. 24 h lactate >1.9 mmol/L and 24 h standard base deficit < -2.3 mmol/Lwere independent predictors of hospital death. CONCLUSION: Our findings suggest that lactate and standard base deficit measurement should be included in the routine assessment of patients with cancer admitted to the intensive care unit with sepsis, septic shock or after high-risk surgery. These markers may be useful in the adequate allocation of resources in this population.

Lactate and base deficit are predictors of mortality in critically ill patients with cancer

OBJECTIVE: Cancer patients frequently require admission to intensive care unit. However, there are a few data regarding predictive factors for mortality in this group of patients. The aim of this study was to evaluate whether arterial lactate or standard base deficit on admission and after 24 hours can predict mortality for patients with cancer. METHODS: We evaluated 1,129 patients with severe sepsis, septic shock, or postoperative after high-risk surgery. Lactate and standard base deficit collected at admission and after 24 hours were compared between survivors and non-survivors. We evaluated whether these perfusion markers are independent predictors of mortality. RESULTS: There were 854 hospital survivors (76.5 percent). 24 h lactate .1.9 mmol/L and standard base deficit , -2.3 were independent predictors of intensive care unit mortality. 24 h lactate .1.9 mmol/L and 24 h standard base deficit , -2.3 mmol/Lwere independent predictors of hospital death. CONCLUSION: Our findings suggest that lactate and standard base deficit measurement should be included in the routine assessment of patients with cancer admitted to the intensive care unit with sepsis, septic shock or after highrisk surgery. These markers may be useful in the adequate allocation of resources in this population.

Effect of PaCO2 variation on standard base excess value in critically ill patients.

PURPOSE: The aim of this study was to investigate the impact of acute Paco(2) temporal variation on the standard base excess (SBE) value in critically ill patients. METHODS: A total of 265 patients were prospectively observed; 158 were allocated to the modeling group, and 107 were allocated to the validation group. Two models were developed in the modeling group (one including and one excluding Paco(2) as a variable determinant of SBE), and both were tested in the validation group. RESULTS: In the modeling group, the mathematical model including SIDai, SIG, l-lactate, albumin, phosphate, and Paco(2) had a predictive superiority in comparison with the model without Paco(2) (R(2) = 0.978 and 0.916, respectively). In the validation group, the results were confirmed with significant F change statistics (R(2) change = 0.059, P < .001) between the model with and without Paco(2). A high correlation (R = 0.99, P < .001) and agreement (bias = -0.25 mEq/L, limits of agreement 95% = -0.72 to 0.22 mEq/L) were found between the model-predicted SBE value and the SBE calculated using the Van Slyke equation. CONCLUSIONS: Acute Paco(2) temporal variation is related to SBE changes in critically ill patients.

Differences in acid-base behavior between intensive care unit survivors and nonsurvivors using both a physicochemical and a standard base excess approach: a prospective, observational study.

PURPOSE: This study aimed to test the hypothesis that intensive care unit survivors and nonsurvivors differ with regard to type and severity of acid-base disorders. MATERIALS AND METHODS: Prospective, observational, cohort study of 107 consecutive patients admitted in a 7-bed intensive care unit during a 6-month period that stayed at least 4 days. All acid-base variables for the first 3 days and the day of discharge were analyzed. RESULTS: Survivors had significant metabolic acidosis upon admission, which was due to hyperlactatemia, an excess of unmeasured anions, and principally, hyperchloremia. A progressive decrease in these anions in the presence of constant hypoalbuminemia led to normal standard base excess at discharge. Nonsurvivors had greater metabolic acidosis upon admission with acidifying variables in similar proportions to that of the survivors. On the day of death, nonsurvivors had a similar degree of metabolic acidosis but a different proportion of the anions (less chloride and more lactate) compared with the day of admission. Unmeasured anions were greater in nonsurvivors both on the day of admission and on the day of death. CONCLUSIONS: Intensive care unit survivors and nonsurvivors differed in the severity of metabolic acidosis; however, the proportion of the different anions causing the acidosis on admission was similar between these 2 groups.

El Laboratorio de Urgencia en la detección de errores preanalíticos. Exceso de Heparina en una muestra de sangre arterial para evaluación de gases, electrolitos y equilibrio ácido-base / The urgency laboratory in the preanalytical mistakes detection

Introducción: La utilización de solución de heparina sódica como anticoagulante en muestras de sangre para determinación de gases y electrolitos, si bien es una práctica muy empleada en nuestro medio, no es aconsejable ya que es la causa más importante de múltiples errores pre-analíticos de distinta magnitud. Objetivo: describir la detección de errores pre-analíticos en el laboratorio de urgencia en un caso clínico. Material y métodos: Dos muestras de sangre de un paciente para determinación de gases en sangre y electrolitos. La muestra N° 1 de sangre arterial fue tomada en una jeringa descartable Prexajet con solución de heparina sódica 25.000 UI/5ml siguiendo el método usual de obtener dicha solución directamente de la ampolla y descartando el exceso de líquido de la jeringa antes de realizar la punción a la paciente. La Muestra N° 2 se obtuvo con jeringa heparinizada para extracción de sangre arterial tamponada con calcio y liofilizada (BD A-Line, Becton-Dickinson). Las determinaciones fueron efectuadas con el equipo automático multiparamétrico de gases en sangre RAPIDLAB 865 (Bayer). Resultados: (Ver Tabla 1). Estos datos no se validaron por falta de lectura del Ca iónico, evidencia de error preanalítico por exceso de solución de heparina. (Ver Tabla 2) Estos datos se validaron y enviaron inmediatamente al profesional tratante. Conclusiones: El procedimiento adecuado propuesto es: a) Toma de muestra en jeringas con heparinato de litio liofilizado tamponado con calcio, anulando por completo los errores causados por la dilución. b) Saturación de la molécula de heparina con iones calcio para minimizar el error en la determinación de calcio iónico.

Experimental antegrade enema. Effects on water, electrolyte and acid-base balances with different solutions.

PURPOSE: To study the effects on the water, electrolyte, and acid-base balances in rabbits submitted to antegrade enema with different solutions through appendicostomy. METHODS: Forty male New Zealand rabbits were submitted to appendicostomy, and distributed in 4 groups, according to the antegrade enema solution: PEG group, polyethylene glycol electrolyte solution (n=10); ISS group, isotonic saline solution (n=10); GS group, glycerin solution (n=10); SPS group, sodium phosphate solution (n=10). After being weighed, arterial blood gas analysis, red blood count, creatinine and electrolytes were measured at 4 times: preoperatively (T1); day 6 postop, before enema (T2); 4h after enema (T3); and 24h after T3 (T4). RESULTS: In PEG group occurred Na retention after 4h, causing alkalemia, sustained for 24h with HCO3 retention. In ISS group occurred isotonic water retention and hyperchloremic acidosis after 4h, which was partially compensated in 24h. GS group showed metabolic acidosis after 4h, compensated in 24h. In SPS group occurred hypernatremic dehydration, metabolic acidosis in 4h, and hypokalemia, hypocalcemia, hypomagnesemia, and metabolic alkalosis with partially compensated dehydration in 24h. CONCLUSIONS: All solutions used in this study caused minor alterations on water, electrolyte or acid-base balances. The most intense ones were caused by hypertonic sodium phosphate solution (SPS) and isotonic saline solution (ISS) and the least by polyethyleneglycol electrolyte solution (PEG) and glycerin solution 12% (GS).

Experimental antegrade enema: effects on water, electrolyte and acid-base balances with different solutions

PURPOSE: To study the effects on the water, electrolyte, and acid-base balances in rabbits submitted to antegrade enema with different solutions through appendicostomy. METHODS: Forty male New Zealand rabbits were submitted to appendicostomy, and distributed in 4 groups, according to the antegrade enema solution: PEG group, polyethylene glycol electrolyte solution (n=10); ISS group, isotonic saline solution (n=10); GS group, glycerin solution (n=10); SPS group, sodium phosphate solution (n=10). After being weighed, arterial blood gas analysis, red blood count, creatinine and electrolytes were measured at 4 times: preoperatively (T1); day 6 postop, before enema (T2); 4h after enema (T3); and 24h after T3 (T4). RESULTS: In PEG group occurred Na retention after 4h, causing alkalemia, sustained for 24h with HCO3 retention. In ISS group occurred isotonic water retention and hyperchloremic acidosis after 4h, which was partially compensated in 24h. GS group showed metabolic acidosis after 4h, compensated in 24h. In SPS group occurred hypernatremic dehydration, metabolic acidosis in 4h, and hypokalemia, hypocalcemia, hypomagnesemia, and metabolic alkalosis with partially compensated dehydration in 24h. CONCLUSIONS: All solutions used in this study caused minor alterations on water, electrolyte or acid-base balances. The most intense ones were caused by hypertonic sodium phosphate solution (SPS) and isotonic saline solution (ISS) and the least by polyethyleneglycol electrolyte solution (PEG) and glycerin solution 12 percent (GS).

OBJETIVO: Estudar os efeitos no equilíbrio hídrico, eletrolítico e ácido-base, do enema anterógrado com diferentes soluções em coelhos através de apendicostomia. MÉTODOS: 40 coelhos Nova Zelândia, machos, submetidos a apendicostomia, distribuídos em quatro grupos segundo a solução de enema: grupo PEG (n = 10) solução de polietilenoglicol com eletrólitos; grupo SF (n = 10) solução fisiológica; grupo SG (n = 10) solução glicerinada; grupo FS (n = 10) solução de fosfato de sódio. Realizou-se pesagem, gasometria arterial, série vermelha, creatinina e ionograma, em quatro tempos: TI (pré-operatório); T2 (6o PO antes do enema); T3 (4h após enema); T4 (24h após T3). RESULTADOS: No PEG ocorreu retenção de Na em 4h, com alcalemia por retenção de HCO3, mantida por 24h. No SF ocorreu retenção hídrica isotônica e acidose hiperclorêmica em 4h, resolvidos parcialmente com 24h. No SG ocorreu acidose metabólica hiperclorêmica em 4h, compensada com 24h. No FS ocorreu desidratação hipenatrêmica, acidose metabólica com ânion gap elevado em 4h, hipopotassemia, hipocalcemia, hipomagnesemia e alcalose metabólica com recuperação parcial da desidratação em 24h. CONCLUSÕES: Todas as soluções empregadas neste estudo causam alterações de pouca intensidade no equilíbrio hídrico, eletrolítico ou ácido-base. As mais intensas foram causadas pela solução de fosfato de sódio e solução fisiológica, e as menos intensas pela solução de polietilenoglicol com eletrólitos e solução glicerinada.

Utility of base deficit, lactic acid, microalbuminuria, and C-reactive protein in the early detection of complications in the immediate postoperative evolution.

OBJECTIVE: To determine the utility of biochemical parameters such as lactic acid (LA), C-reactive protein (CRP), microalbuminuria (MAU), and base deficit (BD) as early markers of complications in the immediate postoperative evolution of elective open gastrointestinal surgeries. DESIGN AND METHODS: Sixty-two patients subject to elective open gastrointestinal surgery were evaluated during a period of 22 months. RESULTS: From the initial 62 patients, 2 were excluded, 29 (48.3%) evolved without complications, and 31 (51.6%) with complications. It was observed that the most significant areas under the ROC curve corresponded to BD in the preoperative period, LA on the first day, and CRP from the second to the seventh day after surgery. MAU was not a discriminating parameter since it did not reach a significant area under the curve (AUC) at any time. CONCLUSIONS: The biochemical markers that best relate to the presence of complications are BD in the preoperative period, LA on the first day, and CRP from the second to the seventh day after surgery.

Ventilación de alta frecuencia vs ventilación mecánica convencional en el manejo de la enfermedad de membrana hialina grave: estudio preliminar / High frequency ventilation vs conventional mechanical ventilation in the handling of severe hyaline membrane disease. preliminary study

Introduccion: En nuestro país existen pocos estudios clínicos sobre ventilación asistida neonatal. Más aún, no hay experiencia publicada con el uso de ventilación de alta frecuencia. Objetivo. evaluar la eficacia y seguridad de la ventilación de alta frecuencia por interruptor de flujo (VAFIF), comparada con la ventilación mecánica convencional (VMC), en niños con enfermedad de membrana hialina (EMH) grave. Material y métodos. Se evaluaron en forma prospectiva la evolución clínica, gasométrica y radiológica de 29 neonatos con EMH, manejados con VAFIF o VMC. Para efectos del análisis se tomaron en cuenta: resultados de gasometrías seriadas, índice de oxigenación (IO2) y gradiente alveolo-arterial de oxígeno (GA/aO2). Se observó la presión media de las vías aéreas (aW) empleada y la velocidad para reducir la fracción inspirada de oxígeno (FiO2) requerida y la duración total de la asistencia ventiladora. Resultados. Catorce pacientes se manejaron con VAFIF y el resto con VMC, sin diferencias en cuanto a sexo, peso y edad gestacional. La duración promedio en el ventilador fue de 6 días para los niños en VAFIF y de 13 en VMC (P=0.05). En relación a las gasometrías, no se apreciaron diferencias en el pH ni en los valores de PaCO2 durante las primeras 72 horas de manejo. Las curvas de PaO2 saturación de oxígeno arterial, IO2, y del GA/aO2 tuvieron mejoría significativa (P<0.01) en los pacientes manejados con VAFIF comparados con los de VMC. De igual manera la reducción en los requerimientos de oxígeno suplementatio (FiO2) fue más rápida en los pacientes en VAFIF (P<0.01). Los cambios radiológicos hacia la resolución de la EMH fueron mucho más evidentes y rápidos en el grupo manejado con VAFIF. No se apreciaron difeencias relevantes en la mortalidad, complicaciones o secuelas entre ambos grupos. Conclusiones. La VAFIFes una modalidad segura, que si bien no modificó la mortalidad en el presente trabajo, permitió reducir en forma importante la FiO2 y la duración de la ventilación asistida

[The anemic gap in depressed newborn infants]. / El hiato aniónico en el neonato deprimido.

Thirty cesarean section-delivered newborn were studied. Fifteen of them scored from 0 to 3 and, 8 and greater on the Apgar scale when measured at one and five minutes, respectively. The other 15 scored 8 or more at one minute and 9 at five minutes. Arterial electrolyte and blood gases were measured in samples obtained from the umbilical cord. The anion gap formula was then applied. The average weight of the depressed newborns was found to be less than for those of the control group. The mean gestational age for both groups was 39 weeks. The average values for electrolyte, bicarbonate and the anion gap were found to be practically the same in both groups. No correlation was found between the pH and the gap nor for the gap and the hydrogen ion concentration [H+]. The correlation between the gap and the bicarbonate was 0.78. No differences were seen between anion gap values for the newborn with lactic acidosis or hyperlactemia when compared to those of the control group. It is therefore concluded that the anion gap is not useful for the detection of newborns suffering from metabolic acidosis. Anion gap; bicarbonate; Apgar score; depressed neonates; metabolic acidosis.