Disorders of acid-base status are common in the critically ill and prompt recognition is central to clinical decision making. The bicarbonate/carbon dioxide buffer system plays a pivotal role in maintaining acid-base homeostasis, and measurements of pH, PCO₂, and HCO₃ ^- are routinely used in the estimation of metabolic and respiratory disturbance severity. Hypoventilation and hyperventilation cause primary respiratory acidosis and primary respiratory alkalosis, respectively. Metabolic acidosis and metabolic alkalosis have numerous origins, that include alterations in acid or base intake, body fluid losses, abnormalities of intermediary metabolism, and renal, hepatic, and gastrointestinal dysfunction. The concept of the anion gap is used to categorize metabolic acidoses, and urine chloride excretion helps define metabolic alkaloses. Both the lungs and kidneys employ compensatory mechanisms to minimize changes in pH caused by various physiologic and disease disturbances. Treatment of acid-base disorders should focus primarily on correcting the underlying cause and the hemodynamic and electrolyte derangements that ensue. Specific therapies under certain conditions include renal replacement therapy, mechanical ventilation, respiratory stimulants or depressants, and inhibition of specific enzymes in intermediary metabolism disorders.

酸碱状态紊乱在危重病人中很常见，及时识别对于临床决策至关重要。碳酸氢盐/二氧化碳缓冲系统在维持酸碱平衡方面发挥着关键作用，pH、PCO ₂和HCO ₃ ^的测量通常用于估计代谢和呼吸紊乱的严重程度。通气不足和通气过度分别导致原发性呼吸性酸中毒和原发性呼吸性碱中毒。代谢性酸中毒和代谢性碱中毒有多种起因，包括酸或碱摄入量的改变、体液流失、中间代谢异常以及肾、肝和胃肠功能障碍。阴离子间隙的概念用于对代谢性酸中毒进行分类，尿液氯化物排泄有助于定义代谢性碱中毒。肺和肾都采用补偿机制来最大限度地减少各种生理和疾病干扰引起的 pH 值变化。酸碱失衡的治疗应主要集中于纠正根本原因以及随之而来的血流动力学和电解质紊乱。某些情况下的具体治疗包括肾脏替代治疗、机械通气、呼吸兴奋剂或抑制剂以及中间代谢紊乱中特定酶的抑制。