Aspirin, also known as acetylsalicylic acid, is a widely used medication for pain relief, fever reduction, and anti-inflammatory purposes. An overdose occurs when someone takes more than the recommended amount, either accidentally or intentionally. This can significantly disrupt the body’s delicate internal acid-base balance, potentially leading to serious conditions like acidosis or alkalosis.
Understanding Acid-Base Balance
The human body maintains a tightly regulated acid-base balance, measured by pH, which is important for proper bodily function. A pH of 7.0 is neutral; values below 7.0 are acidic, and values above 7.0 are alkaline (or basic). Blood pH remains within a narrow range of 7.35 to 7.45.
Acidosis occurs when the body’s pH falls below this healthy range, making the blood too acidic. Conversely, alkalosis occurs when the pH rises above this range, making the blood too alkaline. The body possesses natural buffering systems, primarily involving the lungs and kidneys, which continuously work to keep pH levels stable. The lungs regulate carbon dioxide, an acidic compound, while the kidneys control the excretion or reabsorption of acids and bases.
The Dual Impact of Aspirin Overdose
Aspirin overdose results in a complex acid-base disturbance, characterized by both respiratory alkalosis and metabolic acidosis. This dual impact often unfolds sequentially, with respiratory alkalosis appearing first, followed by metabolic acidosis. This combination of primary respiratory alkalosis and primary metabolic acidosis is characteristic of salicylate poisoning.
Respiratory alkalosis occurs initially due to aspirin’s direct effects on the brain’s respiratory center. As the overdose progresses, metabolic acidosis develops. This dynamic disruption of the body’s pH equilibrium means an aspirin overdose involves both conditions.
Mechanisms of pH Disruption
Aspirin, or salicylate, causes pH imbalances through distinct mechanisms. Salicylates directly stimulate the brainstem’s respiratory center, leading to increased breathing rate and depth (hyperventilation). This rapid breathing causes the body to exhale more carbon dioxide, an acidic blood component. The reduction of carbon dioxide in the bloodstream decreases blood acidity, resulting in respiratory alkalosis.
As the overdose progresses, salicylates contribute to metabolic acidosis through several pathways. One mechanism is the uncoupling of oxidative phosphorylation, disrupting energy production and leading to overproduction of lactic acid and other organic acids. Salicylates also impair kidney function, reducing the body’s ability to excrete these accumulated acids. Additionally, increased fatty acid metabolism can generate ketone bodies, further contributing to metabolic acidosis. This metabolic acidosis develops later and is associated with severe toxicity.
Recognizing and Responding to Aspirin Overdose
Recognizing the signs of aspirin overdose is important for prompt medical intervention. Common initial symptoms include ringing in the ears (tinnitus), nausea, vomiting, and rapid breathing (hyperventilation). As toxicity progresses, individuals might experience confusion, dizziness, fever, and even seizures. Vomiting can occur several hours after ingestion, and dehydration may result from increased breathing, vomiting, and fever.
Given the potential for severe, life-threatening complications related to pH imbalances, immediate medical attention is necessary for any suspected aspirin overdose. Medical professionals assess overdose severity by measuring blood salicylate levels and analyzing blood gases to determine acid-base status. Treatment involves administering activated charcoal to prevent further drug absorption from the gastrointestinal tract, and intravenous fluids correct dehydration and electrolyte imbalances. Sodium bicarbonate is administered to make blood and urine more alkaline, aiding kidney excretion of aspirin. In severe cases, hemodialysis may be required to remove salicylates and restore fluid, electrolyte, and pH balance.