Chapter 14: Concepts of Acid-Base Balance

35 to 7.45, essential for survival. Acids are defined as substances that release hydrogen ions, while bases are substances that bind these ions; buffering systems including bicarbonate, phosphate, and protein buffers provide the immediate defense by maintaining hydrogen ion equilibrium throughout body fluids. The critical 1:20 ratio of carbonic acid to bicarbonate is necessary to preserve blood's slightly alkaline state. Disruption of acid-base equilibrium severely compromises enzyme activity, hormone function, electrolyte distribution, and cellular excitability, creating life-threatening conditions. The carbonic anhydrase equation illustrates the central relationship between carbon dioxide and hydrogen ion production, demonstrating how increased carbon dioxide lowers pH while decreased carbon dioxide raises pH. The body employs three integrated defense mechanisms to maintain pH stability: chemical buffering acts as the first line of defense, the respiratory system provides rapid compensation through ventilation adjustments within minutes, and the renal system ensures long-term balance by regulating hydrogen and bicarbonate excretion or reabsorption. Acidosis develops when hydrogen ions accumulate or bicarbonate is depleted, dropping pH below 7.35; it arises from respiratory failure, kidney disease, diabetic ketoacidosis, or diarrhea and manifests as confusion, lethargy, muscle weakness, hypotension, bradycardia, and Kussmaul respirations, with accompanying hyperkalemia. Respiratory acidosis stems from hypoventilation or impaired gas exchange, while metabolic acidosis results from overproduction of acids such as lactic acid or ketoacids, inadequate hydrogen ion elimination, or bicarbonate loss. Conversely, alkalosis occurs when hydrogen ions are lost or bicarbonate accumulates, raising pH above 7.45; metabolic alkalosis develops from prolonged vomiting, gastric suctioning, or excessive bicarbonate intake, while respiratory alkalosis emerges from hyperventilation due to anxiety, pain, fever, or mechanical ventilation. Alkalosis produces hypocalcemia and hypokalemia, triggering neuromuscular excitability with positive Chvostek and Trousseau signs, paresthesia, hyperreflexia, and risk for falls and dysrhythmias. Arterial blood gas analysis serves as the gold standard diagnostic tool for evaluating pH, carbon dioxide, oxygen, and bicarbonate levels; when one system fails, compensatory mechanisms in the other system activate to restore balance. Treatment interventions target underlying causes while supporting electrolyte replacement and ventilatory adjustments.