CURRENT Essentials of Critical Care.pdf

Chapter 5 Fluids, Electrolytes, & Acid-Base 69■■■Respiratory AlkalosisEssentials of Diagnosis• Arterial pH 7.45; decreased PaCO 2 and compensatory reductionin serum HCO 3 ; due to increased and excessive alveolarventilation• Decreased cerebral perfusion with confusion, lightheadedness,anxiety, irritability• Circumoral paresthesias, tetany, seizures; indistinguishable fromhypocalcemia• Cardiac arrhythmias when pH 7.6• Flattened ST segment or T-waves• Other clinical features associated with underlying etiologyDifferential Diagnosis• Meningoencephalitis • Hypoxemia• Pulmonary fibrosis • Pulmonary embolism• Pulmonary edema • Anxiety, pain• Fever • Sepsis• Liver disease, hepatic failure • Salicylate toxicity• High altitude• Pregnancy and elevated progesterone states• Mechanical ventilation with overventilation• Central nervous system lesions: herniation, cerebrovascular accidentTreatment• Address and treat underlying disorders• Remove and avoid any central suppressing agents• Avoid excessive minute ventilation on mechanical ventilator• Increasing workload on ventilator (SIMV, CPAP, lengtheningventilator circuit tubing) to counteract primary respiratory alkalosisineffective, dangerous, and not recommended• Paralysis with subsequent mechanical ventilation can be consideredin severe cases■ PearlPrimary hyperventilation must be distinguished from compensationfor metabolic acidosis. The difference is that in respiratory alkalosis,low PaCO 2 is primary and pH is above normal, whereas in metabolicacidosis pH is in the acidic range and low HCO 3 represents the primarydisturbance.ReferenceFoster GT: Respiratory alkalosis. Respir Care 2001;46:384.[PMID: 11262557]