Paradoxical metabolic acidosis after vomiting in children with spinal muscular atrophy: A report of 9 patients

Background

Spinal muscular atrophy (SMA) is a hereditary neuromuscular disease that progresses toward restrictive respiratory failure due to muscle paralysis. We observed that SMA patients presented with a specific clinical and laboratory profile, consisting of severe metabolic acidosis following an episode of mild vomiting. This is an unusual, little-known, and life-threatening situation for these patients, as hyperventilation induced by metabolic acidosis can lead to exhaustion and to death by mixed acidosis.

Objective

The aim of our study was to describe this paradoxical acidosis after vomiting in SMA patients and to discuss the physiological basis of this condition.

Methods

We conducted a retrospective single-center study reviewing the clinical and laboratory data of SMA patients who were hospitalized in the intensive care unit for severe metabolic acidosis after vomiting.

Results

Our cohort comprised 11 cases. On arrival, the median pH of the patients was 7.23 with a median bicarbonate concentration of 11.7 mmol/L and almost half of them (45 %) had ketone bodies in the blood and/or urine. The median correction time was 24 h for pH and 48 h for bicarbonate concentrations after receiving intravenous hydration with a glucose solution.

Conclusions

We suggest that SMA patients are particularly sensitive to ketoacidosis induced by fasting, even after a few episodes of mild vomiting. Moreover, they have a low buffering capacity due to their severe amyotrophy, which favors metabolic acidosis. They must be quickly hydrated through a glucose-containing solution to avoid exhaustion, mixed acidosis, and death.