An overdose of salicylate (acetylsalicylic acid) results in which of the following? (1 Point) A. Metabolic acidosis followed by respiratory alkalosis B. Respiratory alkalosis followed by metabolic acidosis C. Metabolic alkalosis followed by respiratory alkalosis D. None of the above
The correct answer and explanation is:
The correct answer is B. Respiratory alkalosis followed by metabolic acidosis.
When a person overdoses on salicylates (such as acetylsalicylic acid, commonly known as aspirin), it can lead to a series of physiological disturbances that initially affect the respiratory system and then the metabolic processes. Here’s how it unfolds:
- Respiratory Alkalosis:
Initially, salicylate toxicity leads to an increase in the rate and depth of breathing, also known as hyperventilation. This occurs because salicylates directly stimulate the respiratory centers in the brain, leading to increased ventilation. Hyperventilation causes an excessive loss of carbon dioxide (CO₂) from the body, which results in respiratory alkalosis. In respiratory alkalosis, the blood becomes more alkaline (increased pH) due to the decrease in CO₂ and bicarbonate levels. - Metabolic Acidosis:
After the initial phase of respiratory alkalosis, as the overdose continues, there are further metabolic disturbances. Salicylates can cause a buildup of lactic acid and ketones, which increases the acidity of the blood. Additionally, salicylates interfere with cellular metabolism, impairing the oxidative phosphorylation in mitochondria, leading to the production of organic acids. This results in metabolic acidosis, a condition where the blood becomes more acidic (decreased pH). The body attempts to compensate by increasing ventilation (respiratory alkalosis), but the metabolic acidosis persists and often worsens.
Thus, the typical progression of symptoms in salicylate poisoning is respiratory alkalosis followed by metabolic acidosis. This sequence is critical for diagnosis and treatment, as interventions typically involve addressing both respiratory and metabolic imbalances.