Distúrbios ácido-base nas doenças hepáticas / Acid-base disorders in liver diseases

O objetivo deste artigo foi abordar as controvérsias científicas acerca dos distúrbios ácido-base nas doenças hepáticas. Nos estágios avançados da doença hepática, os distúrbios ácido-base atuam de forma complexa, comprometendo a qualidade de vida do paciente e desafiando o manejo clínico. A literatura apresenta a alcalose respiratória como uma das principais alterações, porém há uma longa discussão sobre o mecanismo fisiopatológico; em especial, citam-se a hipóxia, a hipocapnia e o nível de progesterona. Nas desordens metabólicas, com destaque para a acidose, os estudos apontam principalmente o lactato, os unmeasured ions ou íons não medidos e as alterações hidroeletrolíticas, mas cada componente desse sobressai-se dependendo da fase da doença estudada, compensada ou descompensada. As controvérsias dos distúrbios ácido-base nas doenças hepáticas devem-se ora à complexidade da fisiopatologia da própria doença, ora à necessidade de mais estudos esclarecedores.

The aim of this study is to address the scientific controversy about acid-base disorders in liver diseases. In the end stage of liver diseases, the acid-base disorder has a complex performance, impairing the patient's quality of life and challenging the clinic management. Although the literature shows respiratory alkalosis as one of the main alterations, there is a long discussion about the pathophysiological mechanism, specially regarding hypoxia, hypocapnia, and progesterone level. In metabolic disorders, especially acidosis, the studies mainly indicate the lactate, unmeasured ions, and hydroelectrolytic alterations, but, depending on the disease phase, either compensated or decompensated, each element has a particular action. The controversy about acid-base disorders in liver diseases is associated with the complexity of this condition, as well as with the necessity of more specialized research.

Avaliação hemogasométrica em cadelas com piometra / Hemogasometric evaluation in bitches with pyometra

A piometra é uma afecção comum em cadelas com uma etiologia hormonal associada à infecção bacteriana, levando ao acúmulo de exsudato uterino. Desequilíbrios ácido-base e hidroeletrolíticos são complicações que contribuem para a progressão da doença, o que piora o estado geral da paciente e pode levá-la ao óbito. O objetivo do presente trabalho foi caracterizar os distúrbios ácido-base e eletrolíticos em cadelas com piometra, além de avaliar se a terapia hídrica pré-cirúrgica (Ringer lactato) é efetiva na correção desses desequilíbrios. Vinte cadelas com piometra foram submetidas à hemogasometria em oito tempos preestabelecidos. Concluiu-se que o distúrbio ácido-base mais frequente foi a alcalose respiratória e que a terapia hídrica no pré-cirúrgico com solução Ringer lactato foi efetiva na correção da acidose metabólica e proporcionou melhora na alcalose respiratória, embora não tenha corrigido quadros de alcalose metabólica.

Pyometra is a common disease in dogs with a hormonal etiology associated with a bacterial infection and leading to accumulation of uterine exudates. Acid-base and electrolyte disturbances are complications that contribute to disease progression, worsening the condition of the patient, possibly leading death. The aim of this study was to characterize the acid-base and electrolyte disturbances in dogs with pyometra, and to evaluate whether preoperative fluid therapy (Ringer's lactate) is effective in correcting these imbalances. Twenty bitches with pyometra were subjected to blood gas analysis in eight pre-set times. It was concluded that the acid-base disorder was the most frequent respiratory alkalosis and fluid therapy in the preoperative Ringer 's lactate solution was effective in the correction of metabolic acidosis, although this has not corrected metabolic alkalosis frames and has provided improved alkalosis breathing .

Ocorrência do SNP c.767G>T no gene DNM1responsável pelo colapso induzido pelo exercício em cães da raça Labrador Retriever no estado de São Paulo / Occurrence of DNM1 SNP c.767G>T responsible for exercise-induced collapse in Labrador Retriever in the Sao Paulo state

O colapso induzido pelo exercício (EIC) é considerado uma síndrome autossômica recessiva que afeta principalmente cães da raça Labrador Retriever. A doença é caracterizada por fraqueza muscular e colapso após exercício intenso. Usualmente, ocorre recuperação clínica após o episódio, mas alguns animais podem vir a óbito. Os sinais clínicos são decorrentes do polimorfismo de base única (SNP) c.767G>T no gene Dynamin 1 (DNM1). O objetivo deste trabalho foi determinar a ocorrência deste SNP em 321 cães da raça Labrador Retriever do Estado de São Paulo. Primers específicos para a amplificação de todo o exon 6 do gene DNM1 foram usados nas PCRs utilizando DNA a partir de amostras de sangue ou swab bucal, a avaliação final foi realizada com sequenciamento direto dos produtos da PCR. Dentre os 321 animais estudados, 3,4 % (11/321) eram homozigotos para o SNP c.767G>T no gene DNM1 e 24,6% (79/321) eram heterozigotos. Somente um dos 11 animais homozigotos apresentavam sinais clínicos compatíveis com a EIC. Este é o primeiro estudo sobre a ocorrência deste SNP no Brasil e considerando que quase 25% dos animais estudados eram heterozigotos, a genotipagem dos animais para este SNP pode ser importante antes dos acasalamentos para cães desta raça. A EIC deve ser considerada nos diagnósticos diferenciais de enfermidades neuromusculares em cães da raça Labrador Retriever.

The exercise-induced collapse (EIC) is considered an autosomal recessive syndrome that mainly affects Labrador Retriever dogs. The disease is characterized by muscle weakness and collapse after intense exercise. Recovery usually occurs after exercise but some animals may die. The clinical signs occurs due to the single-nucleotide polymorphism (SNP) c.767G>T in Dynamin 1 (DNM1) gene. The aim of this study was to evaluate the occurrence of this SNP in 321 Labrador Retriever dogs from São Paulo state. Specific primers for amplification of the entire exon 6 of the DNM1 gene were used in a PCR performed with DNA from blood or buccal swab samples, direct sequencing was performed for the final evaluation. Among 321 animals studied, 3.4% (11/321) of animals were homozygous for the DNM1 SNP (c.767G>T) and 24.6% (79/321) were heterozygous. Only one of the 11 homozygous animals in this study had previous clinical signs compatible with this disease. This is the first study that evaluated the occurrence of DNM1 SNP (c.767G>T) gene in Brazil and considering that almost 25% of the studied animals were heterozygous, the routinely evaluation of this SNP may be important before this breed mating The EIC should be include in the differential diagnosis of neuromuscular diseases in Labrador Retriever dogs.

Acid-base balance of dairy cows and its relationship with alcoholic stability and mineral composition of milk / Equilíbrio ácido-base de vacas leiteiras e sua relação com a estabilidade alcoólica e composição mineral do leite

This study aimed to associate the occurrence of acid-base disorders with the alcoholic stability of milk from animals in the field, and to evaluate differences between the mineral composition of milk that was both stable and unstable in alcohol. The sample comprised 96 dairy cows, where the milk and blood of each corresponding animal was collected. The mineral composition of stable and unstable milk in alcohol was different and may be related to acid-base disturbances. The average amount of phosphate was lower in the milk that was unstable in alcohol, while potassium was greater. Frequency of the alcoholically unstable milk cases was higher in the cows with acid-base disturbances. Respiratory alkalosis was the disorder that was most observed.

Esse trabalho teve como objetivo associar a ocorrência de distúrbios ácido-base com a estabilidade alcoólica do leite de animais a campo, bem como avaliar diferenças entre a composição mineral de leites estáveis e instáveis ao álcool. A amostragem compreendeu 96 vacas leiteiras, das quais o leite e o sangue correspondente de cada animal foram coletados. A composição mineral entre leites estáveis e instáveis ao álcool foi diferente e também pode estar relacionada aos distúrbios ácido-básicos. A quantidade média de fosfato foi menor no leite instável ao álcool, enquanto a de potássio foi maior. A frequência de amostras de leite com instabilidade alcoólica foi maior nas vacas com distúrbios ácido-básicos. A alcalose respiratória foi o desequilíbrio mais observado.

A case of Gitelman syndrome with severe hyponatraemia and hypophosphataemia

Gitelman syndrome (GS) is a renal tubular disorder of the thiazide-sensitive sodium chloride cotransporter, which is located in the distal tubule of the loop of Henle. We present a rare case of GS complicated by severe hyponatraemia and hypophosphataemia. A 17-year-old boy was admitted to our institution with fever and lethargy. The workup revealed typical features of GS, i.e. hypokalaemia, hypomagnesaemia and metabolic alkalosis. In this report, we discuss the differential diagnoses and rationale for accepting GS as the most likely diagnosis. This case was complicated by severe hyponatraemia (115 mmol/L) and hypophosphataemia (0.32 mmol/L). We concluded that the syndrome of inappropriate secretion of antidiuretic hormones could not be ruled out and that respiratory alkalosis was the most likely aetiology of hypophosphataemia. This case report also generates an interesting discussion on water and electrolyte metabolism.

Analytical calculation and acid-base analysis for detection of mixed disorders in critical care medicine.

Aim: The purpose of the study was to validate the systematic six-step arterial blood gas (ABG) analysis in critically ill patients to diagnose mixed ABG disorders. Materials and method: The study was conducted in the ICU of a tertiary care hospital (between 1 June and 30 September, 2007) for 4 months. A total of 560 ABG samples were evaluated from 183 patients. 50 samples were randomly picked and evaluated by single step, quick look method and six-step approaches for detecting mixed ABG disorders. Results: Single, quick and six-step methods when applied on same data, revealed higher number of mixed disorders with systematic six-step approach. Quick-step method revealed only 48% mixed disorders while six-step analysis confirmed 62% having mixed disorders, from the samples which initially appeared to be single disorder. Metabolic acidosis with respiratory acidosis (26%) was the commonest disorder. Metabolic acidosis with respiratory alkalosis (20%), respiratory alkalosis with metabolic alkalosis (6%), metabolic alkalosis with respiratory acidosis (4%), metabolic acidosis with NGMA (4%) and metabolic acidosis with metabolic alkalosis (2%) were the other mixed disorders seen. Conclusion: Mixed disorders as suspected on clinical grounds can only be validated after complete analysis by six-step approach in critically ill patients. pH, PaCO2, and HCO3 – allow determination of primary disorder, but it is only the inequality between predicted and actual compensatory response for simple acid-base disorders which reveals a mixed disorder.

Intoxicación accidental por amitraz / Accidental poisoning with amitraz

Se presenta el caso de una niña de cuatro años de edad que ingirió amitraz, un acaricida, accidentalmente. Presentó pupilas mióticas, irritabilidad y somnolencia, bradicardia, hipotensión arterial, hipotermia, alcalosis respiratoria e hiperglicemia. Recibió fluidos, se hizo aspiración gástrica y se le administró carbón activado. A las 12 horas, la paciente estuvo recuperada y no hubo secuelas en el seguimiento.

This is the case of a 4 year-old who accidentally ingested amitraz, an acaricide. She developed miotic pupils, irritability and somnolence, bradycardia, arterial hypotension, respiratory alkalosis and hyperglycemia. She received fluids, gastric aspiration was done and activated charcoal was administrated. Twelve hours later, the patient was fully recovered and there was no sequelae on following up.

Acute respiratory alkalosis occurring after endoscopic third ventriculostomy: A case report / 대한마취과학회지

An endoscopic third ventriculostomy was performed in a 55-year-old man with an obstructive hydrocephalus due to aqueductal stenosis. The vital signs and laboratory studies upon admission were within the normal limits. Anesthesia was maintained with nitrous oxide in oxygen and 6% desflurane. The patient received irrigation with approximately 3,000 ml normal saline during the procedure. Anesthesia and operation were uneventful. However, he developed postoperative hyperventilation in the recovery room, and arterial blood gas analysis revealed acute respiratory alkalosis. We report a rare respiratory alkalosis that occurred after an endoscopic third ventriculostomy.

Comportamento dos valores espirométricos e da gasometria arterial em pacientes com cirrose hepática / Behavior of the spirometrics values and the arterial gasometria in patients with hepatic cirrhosis

Introdução: As complicações associadas à cirrose hepática são muitas, dentre elas a ascite e a síndrome hepatopulmonar, que podem ocasionar alterações na função pulmonar. Objetivo: Verificar o comportamento dos valores espirométricos e da gasometria arterial em pacientes com cirrose hepática. Método: Participaram desta pesquisa cinco pacientes que apresentavam comprometimento moderado (Child B) a severo (Child C) da função hepática. Os pacientes foram submetidos a uma avaliação para verificação de dados clínicos, além da realização de espirometria e gasometria arterial. A análise de dados foi realizada de forma descritiva, na qual dos dados de cada paciente foram analisados isoladamente. Resultados: Foi observado nesta pesquisa que os classificados como Child B não apresentaram alterações nos valores da espirometria e na gasometria. Entre os classificados como Child C, o paciente A apresentou alcalose metabólica com aumento de PaO2 e os pacientes D e E apresentaram alcalose respiratória com PaO2 próximo ao limite inferior, sendo que apenas o paciente D apresentou distúrbio restritivo leve. Conclusão: Verificou-se baixa ocorrência de hipoxemia e também de alterações nos valores da espirometria dinâmica. Quanto à gasometria arterial, a principal alteração observada está associada com a alcalose respiratória, ocorrendo em dois casos, seguida pela alcalose metabólica, que ocorreu em um caso.

Distúrbios ácido-base na leishmaniose visceral / Acid-base disorders in visceral leishmaniasis

Defeitos na capacidade de acidificação e concentração urinárias têm sido descritos em pacientes portadores de leishmaniose visceral. Foram avaliados os distúrbios do equilíbrio ácido-base presentes nos pacientes com calazar, bem como os fatores relacionados. Metodologia: Foram estudados 59 pacientes com formas crônicas de calazar e comparados a um grupo controle. A gasometria arterial foi colhida em jejum; o pH urinário, a acidez titulável e a amônia urinária foram determinadas em urinas colhidas sob óleo mineral. A amônia foi dosada pela técnica de Berthelot e a acidez titulável, pela técnica de Palmer. Resultados: Todos os pacientes tinham hipoalbuminemia, hipergamaglobulimenia e hiponatremia. O grupo I compreendeu 75,5% dos pacientes, que apresentaram quadro misto de alcalose respiratória e alcalose metabólica. Hipocloremia ocorreu em 37,6%; hipocalemia associada a um potássio urinário elevado foi observada em 24,8% dos casos. Hipomagnesemia com perda renal de magnésio e potássio foi detectada em 44% dos casos. O grupo II, constituído por 24,5% dos pacientes, apresentou quadro de acidose metabólica. A excreção urinária de H+, a acidez titulável e a amônia foram semelhantes nos dois grupos. Um elevado pH urinário e uma carga elétrica urinária positiva confirmaram no grupo II a presença de acidose tubular renal distal. O equilíbrio ácido-base, pelo modelo stewart-Figge, mostra diminuição da diferença de íons fortes (SIDa), elevação do SIG e diminuição da concentração de ácidos fracos. Conclusões: Alcalose respiratória crônica e alcalose metabólica associada 9grupo I) foram observadas em 75.5% dos casos e relacionaram-se com o quadro de pneumonite intersticial, anemia, febre e disfunção hepática. Hipomagnesemia com depleção de potássio e magnésio estava presente.

Defects in the ability of urinary acidification and concentration have been described in patients with visceral leishmaniasis. We assessed disorders present acid-base balance in patients with kala-azar, as well as the related factors. Methodology: We studied 59 patients with chronic forms of leishmaniasis and compared to a control group. The arterial blood gas was collected in fasting, urinary pH, titratable acidity and urinary ammonium were determined in urine collected under mineral oil. Ammonia was measured by the Berthelot technique and acidity, the technique of Palmer. Results: All patients had hypoalbuminemia, and hyponatremia hipergamaglobulimenia. Group I comprised 75.5% of patients, who had mixed picture of respiratory alkalosis and metabolic alkalosis. Hypochloremia occurred in 37.6%, hypokalemia associated with a high urinary potassium was observed in 24.8% of cases. Hypomagnesemia with renal loss of magnesium and potassium was detected in 44% of cases. Group II, consisting of 24.5% of patients presented with metabolic acidosis. The urinary excretion of H +, acidity and ammonia were similar in both groups. A high urinary pH and urinary a positive electric charge in the group II confirmed the presence of distal renal tubular acidosis. The acid-base balance by Stewart-Figge model shows decrease in strong ion difference (AIDS), an increase of GIS and decreased concentration of weak acids. Conclusions: Chronic respiratory alkalosis and metabolic alkalosis associated 9grupo I) were observed in 75.5% of cases and were related to the picture of interstitial pneumonitis, anemia, fever and liver dysfunction. Hypomagnesemia with depletion of potassium and magnesium was present. Metabolic acidosis (group II) was observed in 24.5% of patients presenting with.

Distúrbios do equilíbrio ácido-básico na prática clínica / Disorders of basic acid balance in clinical practice

Na prática médica, o distúrbio do equilíbrio ácido-básico possui grande relevância. Muitas funções metabólicas e fisiológicas dependem do pH. Alterações no pH em geral, decorrem de patologias concomitantes (EX: sepse, insuficiência renal, pneumonia, etc...) e, dependendo do grau de alteração, representam um risco eminente de vida ao paciente,O equilíbrio ácido – básico é um assunto de importância para todas as especialidades. Porém, seu entendimento prático é revestido de diversos graus de dificuldade.

Bedside cardiopulmonary characteristics distinguishing portopulmonary hypertension from primary pulmonary hypertension

The presence of pulmonary hypertension in combination with portal hypertension, otherwise termed porto-pulmonary hypertension [PPHTN], is a well-recognized complication of chronic liver disease. Primary pulmonary hypertension [IryPH] is another type of pulmonary hypertension with obscure aetiology that has similarities to PPHTN. The cardiopulmonary clinical characterestics of both types may be hard to distinguish from each other although they aren't synonymus. To differentiate the bedside cardiopulmonary profile of PPHTN from that of IryPH. A total of 20 patients with PPHTN [Group A] were recruited during the period from August 2005 to September 2007 and compared to a group of 20 patients with IryPH [GroupB]. Clinical assessment, trans-thoracic echocardiography, ECG, chest radiography, room air arterial blood gas measurements and respiratory function tests were done for all patients in addition to the diagnostic liver assessment investigations. Dyspnea on exertion, and cyanosis were main complaints of both groups. Patients with PPHTN [Group A] exhibited less elevated pulmonary pressures than patients with IryPH [mean pulmonary pressure, 51 +/- 2.1 mm Hg versus 62 +/- 2.3 mmHg, [P <0.05]. Chest radiography, Echocardiographic, and ECG findings secondary to pulmonary hypertension were different than group B [p, 0.08]. Echocardiographic signs of diastolic dysfunction were unexpectedly more in group A. Arterial blood gas measurements indicate that PPHTN exhibits a significant accentuation of the chronic respiratory alkalosis [p, 0.04] and has an increased alveolar-arterial gradient [P, 0.000] when compared to patients with IryPH. However, restrictive pulmonary dysfunction and reduced diffusion were more found in IryPH [Group B] [p, 0.05]. PPHTN and IryPH patients possess characteristics common to both groups, but, more importantly, they also have distinctive cardiopulmonary characteristics that allow differentiation. Despite tendency to have less degree of PH, PPHTN patients have more accentuated respiratory alkalosis and more increased alveolar aterial gradient than patients with primary PH also IryPH patients have more restrictive pulmonary functions. Cardiac Diastolic dysfunction is also more prominent in patients with PPHTN than in IryPH patients

Survey of relationship between asthma and epilepsy

Asthma attacks can result in respiratory alkalosis and decreased level of Ionized calcium and cerebral Vasoconstriction. Different studies indicate that Alkalosis and decreased level of CO2 can increase convulsive activities and neuronal excitability. This condition may increase level of Dopamin and risk of convulsion. This study was conducted to survey the relationship between asthma and epilepsy. In an Analitical- cross sectional study 400 Asthmatic patients who were reffered to outpatient clinic of Tabriz university of Medical sciences from January 2004 to July 2006, were concurrently surveyed for Epilepsy too. The results analyzed with Z test for one proportion. Number of patients who had two disease of asthma and Epilepsy concurrently was 12 which 7 of them were male and 5 female respectively. Mean age of patients was 5 +/- 2/3 with confidence interval [Ci = 3/5 - 6/5] Comparison of Asthmatic patients who were epileptic with Normal population was significant [P=0/009] Considering epilepsy prevalence rate of%1 in normal population and%3 in asthmatic patients and risk of respiratory alkalosis in asthmatic it is slrongly recommended to have special attention to Asthma attacks, in epileptic too

Hypocalcemia in acute respiratory alkalosis

The objective was to compare the two procedures of treatment for hypocalcemia in acute respiratory alkalosis performed by rebreathing into a small paper bag with that of the IV calcium replacement therapy. 25 patients with clinical manifestations of hypocalcemia admitted to the Department of Emergency, Cho Ray Hospital were prospectively included in this study. Patients were divided into two groups according to the time of day they visited the emergency department. Group I was treated by IV calcium replacement. Group II was treated rebreathing into a small paper bag without drug. In conclusion, group I had 3.80.8 minute and group II had 4.41.17 minute to disappear the manifestations of hypocalcemia. The average statistical test between these two groups in this study has shown that the two procedures were not different statistical significance

Complications of mandibular third molar extraction : two case reports of hyperventilation syndrome and displacement of roots into submandibular space

Vital respiratory indexes of secondary school students at Sapa and Yen Binh

This cross-sectional study involved 339 students aged 12-15 at Sapa and Yen Binh regions. It measured and compared indexes such as vital capacity (VC), forced expiratory volume 1 (FEV1), and Tiffeneau index. Results: there weren’t significant differences between VC, FEV1 and Tiffeneau indexes of students in both sexes of 2 regions (p0.9), and between FEV1 and height (r>0.9)

The Interpretation of Respiratory Acidosis and Respiratory Alkalosis / 대한구급학회지

No abstract available.

The Study of Plasma D-lactate Level and Acid-base Imbalance in Cirrhotic Patients / 대한신장학회잡지

PURPOSE: D-lactate, optical isomer of L-lactate is not a human metabolite. Once the D-lactate enters the human body, it is mainly metabolized in liver. The metabolism of D-lactate can be changed in patients with decompensated liver cirrhosis with the exposure of antibiotics and the frequent trial of lactulose, if neccessory. The aim of this study is to analyze blood D-lactate level in cirrhotic patients and it's relationship with the degree of hepatic insufficiency and acid-base imbalance. METHODS: Plasma L-lactate and D-lactate levels were measured in 40 cirrhotic patients classified by Child-Pugh system with L-LDH and D-LDH with comparison of their changes before and after the use of antibiotics and lactulose(n=14). Also, acid-base disorders were analyzed in 35 cirrhotic patients, and plasma L, D-lactate levels were determined in each acid-base disorder. RESULTS: Plasma D-lactate level was not significantly elevated in cirrhotic patients compared to the control group(2.34+/-.48 mmol/L vs. 1.63+/-.26 mmol/ L, p=NS), but some patients(n=4, 10%) revealed abnormally elevated D-lactate level. The plasma L, D- lactate levels were not different in subgroups classified by Child-Pugh system as well as by underlying causes of liver cirrhosis, and plasma D-lactate level was not sugnificnatly different before and after the exposure of antibiotics and lactulose. Plasma D-lactate level was significantly increased in 3 patients with respiratory alkalosis and metabolic acidosis(12+/-.98 mmol/L) compared to others(p<0.05). CONCLUSION: These results suggest that, regardless of its decompensated degree and exposure to drugs, a subset of patients with liver cirrhosis can develop elevation of D-lactate in blood, particularly when metabolic acidosis is accompanied.

Desequilibrios ácido-básicos en pacientes de la sala de terapia intensiva / Acid-base imbalance in patients admitted to the Intensive Care Unit

Para valorar la frecuencia de presentación y la letalidad de los trastornos ácido-básicos diagnosticados en la sala de terapia intensiva se llevó a cabo un estudio prospectivo con 100 pacientes ingresados consecutivamente a partir del 1 de noviembre de 1999, de los cuales se obtuvieron 1 108 informes de hemogasometrías arteriales y se agruparon estos resultados según las anormalidades documentadas. Se comprobó que el 76 porciento de los estudios mostraba algún desequilibrio ácido-básico, con predominio marginal de los mixtos. La alcalosis respiratoria simple (27,6 porciento) y la combinación de ésta con acidosis metabólica (22,7 porciento) fueron las combinaciones más frecuentes. Todos los trastornos, con excepción de la alcalosis respiratoria simple y la acidosis respiratoria simple, presentaron letalidad igual o mayor que el 65 porciento, y sobresalió la asociación de acidosis respiratoria con alcalosis metabólica (89 porciento). La validación estadística fue con la técnica de chi cuadrado, y se consideró significativa la p<0,05. Estos resultados sugieren la necesidad de prevenir y tratar precozmente los desequilibrios ácido-básicos en las unidades de terapia intensiva