From the Guidelines
Hyperchloremia is most commonly caused by excessive administration of chloride-rich fluids like normal saline, while hypocarbia is primarily due to alveolar hyperventilation triggered by various factors including anxiety, pain, or mechanical overventilation. The causes of hyperchloremia and hypocarbia can be multifaceted, involving both physiological and pathological processes. Hyperchloremia, characterized by elevated serum chloride levels above 106 mEq/L, can result from dehydration, which concentrates electrolytes in the blood, as well as from the administration of large volumes of 0.9% saline, a practice that can lead to hyperchloremic acidosis, renal vasoconstriction, and acute kidney injury (AKI) 1. Other potential causes include renal tubular acidosis, certain medications, adrenal disorders, and bromide intoxication. On the other hand, hypocarbia, or decreased carbon dioxide levels in the blood (typically below 35 mmHg), is often a consequence of alveolar hyperventilation. This can be triggered by anxiety, pain, fever, high altitude, early sepsis, pulmonary disorders, central nervous system disorders affecting respiratory control, metabolic acidosis, and mechanical overventilation in patients on ventilators.
Key Causes and Considerations
- Hyperchloremia:
- Excessive administration of 0.9% saline, which can lead to hyperchloremic acidosis and AKI 1.
- Dehydration.
- Renal tubular acidosis.
- Certain medications.
- Adrenal disorders.
- Bromide intoxication.
- Hypocarbia:
- Alveolar hyperventilation due to anxiety, pain, fever, or high altitude.
- Early sepsis.
- Pulmonary disorders like asthma or pneumonia.
- Central nervous system disorders affecting respiratory control.
- Metabolic acidosis.
- Mechanical overventilation in patients on ventilators.
Given the potential for significant morbidity and mortality associated with hyperchloremia and hypocarbia, particularly in the context of critical illness or perioperative care, it is crucial to address the underlying cause of these conditions rather than solely treating the electrolyte or gas abnormality. For instance, switching from 0.9% saline to balanced crystalloid solutions can help mitigate hyperchloremia 1, while anxiety-induced hypocarbia may be managed with breathing techniques or anxiolytics. The most recent and highest quality evidence supports the use of buffered intravenous solutions in the perioperative period to reduce the risk of hyperchloremic acidosis and its complications 1.
From the Research
Causes of Hyperchloremia
- Hyperchloremia can occur when water losses exceed sodium and chloride losses, when the capacity to handle excessive chloride is overwhelmed, or when the serum bicarbonate is low with a concomitant rise in chloride as occurs with a normal anion gap metabolic acidosis or respiratory alkalosis 2.
- Excessive administration of normal saline can result in hyperchloremic metabolic acidosis, leading to higher mortality rates 3.
- Hyperchloremia can be caused by changes in fluid balance, such as water excess or deficit, resulting in changes in sodium and other electrolyte concentrations 4.
- Hyperchloremic acidosis can occur in critically ill patients, and is associated with decreases in plasma bicarbonate 5.
- Hyperchloremic acidosis can also occur during the recovery phase of diabetic ketoacidosis, due to a difference in volume of distribution between bicarbonate and organic anions 6.
Causes of Hypocarbia
- Hypocarbia, or low carbon dioxide levels in the blood, can be caused by respiratory alkalosis, which can occur when the serum bicarbonate is low with a concomitant rise in chloride 2.
- Hypocarbia can also be caused by changes in fluid balance, such as water excess or deficit, resulting in changes in sodium and other electrolyte concentrations 4.
- There is no direct evidence in the provided studies to suggest other specific causes of hypocarbia, however, it is often associated with hyperchloremia as seen in the case of normal anion gap metabolic acidosis or respiratory alkalosis 2, 3, 4, 5, 6.