Pathophysiology of acid base balance: the theory practice relationship

There are many disorders/diseases that lead to changes in acid base balance. These conditions are not rare or uncommon in clinical practice, but everyday occurrences on the ward or in critical care. Conditions such as asthma, chronic obstructive pulmonary disease (bronchitis or emphasaemia), diabetic ketoacidosis, renal disease or failure, any type of shock (sepsis, anaphylaxis, neurogenic, cardiogenic, hypovolaemia), stress or anxiety which can lead to hyperventilation, and some drugs (sedatives, opioids) leading to reduced ventilation. In addition, some symptoms of disease can cause vomiting and diarrhoea, which effects acid base balance. It is imperative that critical care nurses are aware of changes that occur in relation to altered physiology, leading to an understanding of the changes in patients' condition that are observed, and why the administration of some immediate therapies such as oxygen is imperative.

Severe metabolic alkalosis due to pyloric obstruction: case presentation, evaluation, and management

A 46-year-old man presented to the emergency room with severe metabolic alkalosis, hypokalemia, and respiratory failure requiring intubation and mechanical ventilation. The cause of his acid-base disorder was initially unclear. Although alkalosis is common in the intensive care unit, metabolic alkalosis of this severity is unusual, carries a very high mortality rate, and requires careful attention to the pathophysiology and differential diagnosis to effectively evaluate and treat the patient. A central concept in the diagnosis of metabolic alkalosis is distinguishing chloride responsive and chloride nonresponsive states. Further studies are then guided by the history and physical examination in most cases. By using a systematic approach to the differential diagnosis, we were able to determine that a high-grade gastric outlet obstruction was the cause of the patients' alkalosis and to offer effective therapy for his condition. A literature review and algorithm for the diagnosis and management of metabolic alkalosis are also presented.

Intestinal Ileus as a Possible Cause of Hypobicarbonatemia

The possible occurrence of metabolic acidosis in patients with intestinal ileus is not well recognized. We describe a patient with acute alcohol-induced pancreatitis and a large transverse colon ileus in which plasma bicarbonate dropped rapidly in the absence of an increase in the plasma anion gap. The urinary anion gap and ammonium excretion were consistent with an appropriate renal response to metabolic acidosis and against the possibility of respiratory alkalosis. The cause of the falling plasma bicarbonate was ascribed to intestinal bicarbonate sequestration owing to the enhancement of chloride-bicarbonate exchange in a dilated paralyzed colon.

A case of recurrent renal failure associated with metabolic alkalosis induced by protracted vomiting

We describe a case of recurrent deterioration of renal function in a 54-year-old man who was found to have metabolic alkalosis, with a maximum PaCO(2) of 73.9 mmHg and a bicarbonate concentration of 55.3 mmol/l. He had a gradual exacerbation of nausea and vomiting due to atrophic gastritis, with a scarred, deformed pyloric part of the stomach and a duodenal bulb secondary to chronic peptic ulcer. His metabolic alkalosis and deteriorated renal function were corrected by intravenous saline with or without potassium chloride. However, his recovered creatinine clearance was at most 60 l/day (41.6 ml/min). A renal biopsy revealed cellular infiltration of mononuclear cells and atrophic change in the tubulointerstitium, suggesting chronic interstitial nephritis. Latent renal insufficiency and dehydration induced by protracted vomiting may easily induce a rapid and recurrent deterioration of renal function, and control of vomiting seemed to be the cardinal measure. Initially, his nausea and vomiting seemed to be successfully controlled by medication, however, they later became persistent and surgical correction of the stomach was carried out. Postoperative recovery was smooth, and the patient's vomiting and recurrent deterioration of renal function finally settled.

Metabolic alkalosis in a hemodialysis patient – successful treatment with a proton pump inhibitor

Hemodialysis patients develop metabolic acidosis due to their impaired excretion of daily produced protons (H+). The following report will show a rare case of severe metabolic alkalosis (predialysis pH 7.52, base excess (BE) +17) in a hemodialysis woman caused by self-provoked upper gastrointestinal H+ losses based on an eating disorder. Treatment with a proton pump inhibitor resulted in the normalization of acid/base homeostasis (predialysis pH 7.40, BE +1.6).

Metabolic Alkalosis, Bedside and Bench

Although significant contributions to the understanding of metabolic alkalosis have been made recently, much of our knowledge rests on data from clearance studies performed in humans and animals many years ago. This article reviews the contributions of these studies, as well as more recent work relating to the control of renal acid-base transport by mineralocorticoid hormones, angiotensin, endothelin, nitric oxide, and potassium balance. Finally, clinical aspects of metabolic alkalosis are considered.

Acid-Base and Potassium Disorders in Liver Disease

Acid-base and potassium disorders occur frequently in the setting of liver disease. As the liver's metabolic function worsens, particularly in the setting of renal dysfunction, hemodynamic compromise, and hepatic encephalopathy, acid-base disorders ensue. The most common acid-base disorder is respiratory alkalosis. Metabolic acidosis alone or in combination with respiratory alkalosis also is common. Acid-base disorders in patients with liver disease are complex. The urine anion gap may help to distinguish between chronic respiratory alkalosis and hyperchloremic metabolic acidosis when a blood gas is not available. A negative urine anion gap helps to rule out chronic respiratory alkalosis. In this disorder a positive urine anion gap is expected owing to suppressed urinary acidification. Distal renal tubular acidosis occurs in autoimmune liver disease such as primary biliary cirrhosis, but often is a functional defect from impaired distal sodium delivery. Potassium disorders are often the result of the therapies used to treat advanced liver disease.

Hyponatremic dehydration as a presentation of cystic fibrosis

BACKGROUND

The purpose of this study is to present a case report of a child with hyponatremic dehydration diagnosed after CF and to review the cases of 13 patients with CF who had the same initial presentation in our hospital.

METHODS

This report reviewed the clinical records of children diagnosed with CF to ascertain the prevalence of metabolic alkalosis with electrolyte depletion as the presentation of CF. It also used sweat tests to diagnose a child with CF.

RESULTS

The laboratory tests of a 12-month-old girl presented 3 times to the ;pediatric emergency department with vomiting and weight loss showed hyponatremia, hypochloremia, and metabolic alkalosis. The patient was subsequently diagnosed with CF by means of 2 positive sweat tests. Meanwhile, the review of the clinical records of all children diagnosed with CF from 1985 to 2004 (N = 77) showed that the prevalence of metabolic alkalosis with electrolyte depletion as the presentation of CF was 16.8%. The age of the infants ranged from 3 to 14 months. All episodes took place during summer.

CONCLUSIONS

There are not many causes of metabolic alkalosis with hyponatremic dehydration, and one of them is CF. This report emphasizes sodium depletion as a common sign of CF presentation. This is most important in countries where the neonatal screening test for CF is not available because the disease may be asymptomatic or oligosymptomatic for several months or even years. Cystic fibrosis should be considered in differential diagnosis of any child presenting with unexplained hyponatremic dehydration.

Diagnosis and management of metabolic alkalosis

Elevated pH and elevated plasma bicarbonate level above normal characterise metabolic alkalosis. When bicarbonate is elevated pCO2 must also be elevated to maintain pH to its normal range. Therefore with metabolic alkalosis, the compensation is to decrease alveolar ventilation, and increase pCO2. The causes of metabolic alkalosis are gastro-intestinal hydrogen and chloride loss and due to renal cause. For metabolic alkalosis to continue both generation and maintenance of high levels of bicarbonate are necessary. The diagnosis of metabolic alkalosis is established by noting pH, serum bicarbonate (elevated) and pCO2 (compensatory) elevation. To establish the causes it is necessary to determine intravascular volume, supine and standing blood pressure and renin angiotension alolosterone axis. In chloride responsive alkalosis in which the conditions are extracellular volume depletion, hypokalaemia and hypochloraemia correction of intravascular volume with sodium chloride is needed. In severe metabolic alkalosis of any cause dilute hydrochloric acid (0.1 N HCl) may be infused intravenously but haemolysis may be a complication. In emergency situation with severe hypokalaemia dialysis with higher K+, Cl- and low HCO3- bath will be appropriate.

[A man with a classic serious milk-alkali syndrome and a carcinoma of the stomach]

A 42-year-old man was transferred to the Emergency Department after his friends had found him unresponsive and confused in his room. He had been experiencing upper abdominal complaints for a period of several months. He had taken large amounts of a calcium carbonate/magnesium subcarbonate preparation (Rennie) and had consumed at least 3 litres of dairy products per day. His behaviour was reported as being more and more abnormal during the previous few weeks. On admission he was confused and agitated and had involuntary movements of his limbs. Laboratory investigation indicated a triple acid base disorder, i.e. metabolic alkalosis, respiratory alkalosis and high anion gap metabolic acidosis, with severe dehydration. The metabolic alkalosis was caused by the intake of large amounts of dairy and antacids: milk-alkali syndrome. The metabolic acidosis was the result of hypovolaemia and pre-renal renal failure and the respiratory alkalosis was caused by hyperventilation due to the organic psychosyndrome. The patient was treated with volume expansion by isotonic saline and the administration of potassium and he was sedated with low-dose midazolam, which led to a full respiratory compensation of the metabolic alkalosis. A few days following admission, both the plasma calcium concentration and renal function returned to normal; the acid-base disorder completely normalized and the organic psychosyndrome disappeared. On gastroduodenoscopy a gastric ulcer was found; biopsies revealed a signet ring cell adenocarcinoma of the stomach.

Acid-base balance in heart failure

In end-stage heart failure, various acid-base disorders can be discovered due to the renal loss of hydrogen ions and hydrogen ion movements into cells, the reduction of the effective circulating volume, hypoxemia and renal failure. This justifies the occurrence of metabolic alkalosis, metabolic acidosis, respiratory alkalosis, as well as respiratory acidosis alone or in combination. Several studies have been published on the acid-base state in heart failure. In a 1951 study, Squires et al analyzed the distribution of body fluid in congestive heart failure by taking into consideration the abnormalities in serum electrolyte concentration and in acid-base equilibrium. A recent study by Milionis et al, analyzed 86 patients with congestive heart failure receiving conventional treatment; the majority of these patients exhibited hypokalemia, hyponatremia, hypocalcemia and hypophosphatemia. Disorders in acid-base balance were noted in 37.2% of patients. In a recent study, 70 patients with severe congestive heart failure before heart transplantation showed high-normal pH, slightly reduced pCO 2 and a slight loss of hydrogen ions. After heart transplantation, stability of blood pH and hydrogen ion concentrations was found. In contrast, bicarbonate and pCO 2 increased significantly. The data led us to formulate the diagnosis of a mixed acid-base disorder that includes respiratory alkalosis and metabolic alkalosis before heart transplantation. In heart failure, the presence of acid-base imbalance associated with the activation of mechanisms that lead to salt and water retention reveals evidence concerning the pivotal role of the kidney in determining the outcome of these patients.

Clinical presentation of metabolic alkalosis in an adult patient with cystic fibrosis

In subtropical and tropical climates, dehydration is common in cystic fibrosis patients with respiratory exacerbations. This may lead to a clinical presentation of metabolic alkalosis with associated hyponatraemia and hypochloraemia. An adult cystic fibrosis patient who presented with a severe respiratory exacerbation accompanied by metabolic alkalosis is presented and the effects of volume correction are reported.

[A mixed acid-base disorder revealing a cystic dystrophy of aberrant pancreatic tissue]

We report about a patient presenting with a mixed acid-base disorder. His blood gas analysis showed a metabolic acidosis caused by renal failure and lactic acidosis combined with a hypochloraemic alkalosis. The underlying pathology was a cystic dystrophy of aberrant pancreatic tissue leading to excessive vomiting, extracellular dehydration with a renal failure and hypochloraemia.

An unusual presentation of cystic fibrosis in an adult

The diagnosis of cystic fibrosis (CF) generally is made within the first few years of life, although some cases will not be diagnosed until adulthood. For most patients the diagnosis is suggested by typical CF-related symptoms such as chronic respiratory infection or maldigestion. The authors describe an adult patient with newly diagnosed CF whose presenting abnormalities consisted of hypokalemia and metabolic alkalosis. These are known complications of CF but are not common presenting features that lead to the diagnosis of CF. The authors discuss their patient's presentation and review his metabolic manifestations of CF.