Severe alveolar hypoventilation in a patient with metabolic alkalosis

Perioperative apnea in infants with hypertrophic pyloric stenosis: A systematic review

BACKGROUND

Infantile hypertrophic pyloric stenosis (IHPS) leads to excessive vomiting and metabolic alkalosis, which may subsequently cause apnea. Although it is generally assumed that metabolic derangements should be corrected prior to surgery to prevent apnea, the exact incidence of perioperative apneas in infants with IHPS and the association with metabolic alkalosis are unknown. We performed this systematic review to assess the incidence of apnea in infants with IHPS and to verify the possible association between apnea and metabolic alkalosis.

METHODS

We searched MEDLINE, Embase, and Cochrane library to identify studies regarding infants with metabolic alkalosis, respiratory problems, and hypertrophic pyloric stenosis. We conducted a descriptive synthesis of the findings of the included studies.

RESULTS

Thirteen studies were included for analysis. Six studies described preoperative apnea, three studies described postoperative apnea, and four studies described both. All studies were of low quality or had other research questions. We found an incidence of 27% of preoperative and 0.2%-16% of postoperative apnea, respectively. None of the studies examined the association between apnea and metabolic alkalosis in infants with IHPS.

CONCLUSIONS

Infants with IHPS may have a risk to develop perioperative apnea. However, the incidence rates should be interpreted with caution because of the low quality and quantity of the studies. Therefore, further studies are required to determine the incidence of perioperative apnea in infants with IHPS. The precise underlying mechanism of apnea in these infants is still unknown, and the role of metabolic alkalosis should be further evaluated.

Peritoneal dialysis as therapy for electrolyte and acid base disorders

Peritoneal dialysis (PD) does not demand special equipment and its fluid composition can be easily changed according to the individual condition. Nine patients with chronic or acute renal failure presented severe metabolic alkalosis (MA). Hemodialysis (HD) proved virtually ineffective and the MA persisted. Physiological saline solution was adopted as the main component of the PD fluid for the treament of MA. By this method, CI– can be shifted from PD fluid to extracellular fluid (ECF) and HCO3– from ECF to PD fluid by ionic gradient. Therefore, pH and base excess (BE) of these patients both improved to the normal range after several fluid exchanges. The lowering effect of BE (ΔBE/L) ranged from 0.99 to 2.6. Hyposaline and normo-osmol solution (Na+ 70 mEq/L) were used for one patient with hypernatremia and consciousness disturbance. Serum (S)-Na decreased from 170 to 138 mEq/L, and consciousness became almost clear with the use of 15 L of PD fluid. Hypersaline solution (Na+ 190 mEq/L) was used for two patients with hyponatremia (S-Na 113 and 121 mEq/L). S-Na rose to within the normal range after 16 and 9 L in the two cases. A fluid mixed with distilled water, 10% NaCl and 7% NaHCO3 (HCO3– 34 - 68 mEq/L) was used to treat lactic acidosis in two patients. By this method, HCO3– can be shifted from PD fluid to ECF and lactic acid from ECF to PD fluid. Two patients recovered from prolonged shock, and pH was corrected by 10 L and 4 L, respectively. PD should be considered for application in other diseases besides renal failure.

Milk-alkali syndrome caused by ingestion of antacid tablets

The authors report the case of a 66-year-old man suffering from a milk-alkali syndrome caused by the ingestion of large amounts of antacid tablets. The milk-alkali syndrome is a rare metabolic disorder but remains an important cause of hypercalcaemia. The symptoms of the syndrome are the triad of hypercalcaemia, metabolic alkalosis and renal insufficiency. The primary disorders are the ingestion of an excess of calcium and absorbable alkali as well as their decreased renal excretion. Fully reversible in early stages, it may lead to irreversible complications like chronic renal failure and soft tissue calcification in more advanced stages. The physiopathological mechanism of the syndrome will be reviewed in this report. The association with chronic obstructive pulmonary disease and respiratory acidosis may play a precipitating role.

Hydrochloric acid for treating metabolic alkalosis

Six patients with severe metabolic alkalosis were treated with intravenous hydrochloric acid (HCl) infusion. HCl was given through a central venous catheter, at a concentration of 0.1 mEq per ml. At least two of the following criteria were considered for initiation of the therapy: An arterial pH of greater than 7.45, a base excess (BE) of greater than +7 mmol/L, a PaCO2 of greater than 50 mmHg. The HCl amount was calculated using the BE formula, however, two thirds was infused for avoiding excessive acid loading. Patients were monitored by the blood gases, serum electrolytes, hemoglobin, hematocrit, bilirubin determinations and blood smear findings. While a significant decrease was noticed in pH and BE values, moderate changes were detected in PaCO2 due to different ventilatory status of the cases. All laboratory test results remained within normal limits and no complication was encountered. The advantage of the therapy is that less volume is needed for the correction of alkalosis, particularly in the cases requiring fluid restriction. HCl therapy, moreover, is a safe and time-saving method because of having rapid response to the treatment in the critically ill surgical patients.

Prevention of metabolic alkalosis induced by gastric fluid loss using H2 receptor antagonist

Gastric fluid loss is a common cause of metabolic alkalosis. We studied various acid-base parameters in 20 patients undergoing continuous nasogastric (NG) suctioning for periods ranging from 3 to 17 days. Ten patients received cimetidine 300 mg intravenously every 6 hr (cimetidine-treated group). The remaining 10 patients received an antacid compound through the NG tube (control group). The rise in plasma bicarbonate concentration was significantly greater in the control group as compared to the cimetidine-treated group. As expected, gastric acid output was considerably lower in the cimetidine-treated group than in the control group. We conclude that cimetidine administration may be used in preventing metabolic alkalosis associated with gastric fluid loss by inhibiting gastric secretion of HCl.

Compensatory hypoventilation in metabolic alkalosis

Although hyperventilation is a well-known compensatory mechanism in metabolic acidosis, compensatory hypoventilation has been inconsistent and controversial in metabolic alkalosis. Six healthy subjects were studied under baseline conditions and during steady-state metabolic acidosis (seven episodes) and alkalosis (14 episodes). Minute ventilation (VE) fell in metabolic alkalosis and rose in metabolic acidosis. These changes in ventilation were entirely due to reduction and elevation of tidal volume (VT) respectively, while respiratory frequency (f) remained unchanged. Alveolar ventilation fell during metabolic alkalosis and resulted in elevation of arterial PCO2 in all subjects. The ventilatory response to arterial PCO2 in all subjects. The ventilatory response to CO2 breathing was also diminished. There was a linear relationship between PaCO2 and plasma [HCO-3] in metabolic acidosis and alkalosis which was defined as PaCO2 (mm Hg = 0.7 [HCO-a] + 20 (+/- SEM), r = 0.95. Although arterial PO2 and plasma [K+] fell during metabolic alkalosis, minute ventilation did not change upon breathing oxygen and there was no correlation between changes in plasma [K+] and plasma H+ regulation.

Lysine hydrochloride for the control of metabolic alkalosis: a clinical report

Many physiopathological states can produce metabolic alkalosis that must be promptly corrected as soon as it is dangerous. In our study we report the effectiveness of lysine hydrochloride to correct this condition in patients. This drug lowers the pH, reduces the bicarbonate stores, and leads to normal blood gases.

Severe hypercapnia associated with a non-respiratory alkalosis

A case of hypoventilation in response to a non-respiratory alkalosis is presented. It is postulated that the degree of hypoventilation encountered was a normal response and that a fall in intracellular hydrogen ion concentration was responsible for the hypoventilation. This explains why the alkalosis associated with potassium deficiency is not associated with hypoventilation since the intracellular hydrogen ion concentration then remains constant. The renal response in this condition is responsible for maintaining the alkalosis and seems to be aimed at sodium conservation and hence plasma volume control rather than defence of acid-base balance.

Respiratory failure

Patients with respiratory failure should be approached in a systematic way, with emphasis both in diagnosis and treatment on arterial blood gases. The intelligent assessment of oxygenation, ventilation and acid-base balance, based on physiologic principles, can make the management of these patients very rewarding. The physiologic principles outlined here should be well understood by anyone entrusted with the care of these patients. They provide the cornerstone of diagnosis and management, and will remain valid long after current clinical dogma has been revised.

A diagram to facilitate the understanding and therapy of mixed acid base disorders

A diagram based on in-vivo relationships between arterial hydrogen ion activity (H+) and carbon dioxide tension (PCO2) in primary abnormalities of acid base homeostasis is presented. It is designed to facilitate the interpretation of pH data by including the 95% confidence limits described in patients with simple metabolic and respiratory acid base disorders. These bands have been formulated from observation of simple acid base abnormalities and indicate the appropriate respiratory or renal compensatory response to the primary pH defect. A plot which falls outside these limits therefore indicates the presence of a mixed acid base disorder. The diagram presents a physiological approach to clinical disorders of pH regulation demonstrating maintenance of intra-cellular fluid homeostasis during primary extracellular fluid disturbances. Diagnostic and therapeutic advantages are further illustrated and discussed in six case reports.