Blood gas analysis: acid–base, fluid, and electrolyte disorders
Acid-base homeostasis is vital for the maintenance of normal tissue and organ function, as both acidosis and alkalosis can have harmful and potentially life-threatening effects on the human body. Arterial blood gas analysis, combined with routine clinical history and examination, can provide useful information for the management of the critically ill cardiac patient. Most acid–base derangements are reversed by treatment of the underlying disease process, rather than by simple correction of the abnormal pH, and prognosis is determined by the nature of the underlying disease, rather than by the extent of pH value deviation. In this chapter, an approach is presented for prompt and accurate acid–base interpretation. Water and electrolyte disorders are common in the intensive cardiac care unit, particularly in patients with cardiac failure. Prompt recognition and treatment are required to prevent cardiovascular and neurological compromise. Therapeutic strategies range from simple electrolyte substitution and fluid management to extracorporeal filtration of excess fluid and electrolytes. These are discussed in this chapter.