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.

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.

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 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.

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

Acid base balance in seriously ill surgical cases and its prognostic significance.

Acid base changes are common in surgical patients. The present study was conducted in 50 seriously ill surgical patients over a period of 56 hours. A wide range of pH was observed with 72% observations outside the normal limits. Alkalosis was observed in 44% of total observations while acidosis was noted in 28%. A higher mortality was seen in cases with alkalosis.