Acidosis, Respiratory Key Features • Low arterial pH (< 7.35), increased PCO 2 (> 48 mm Hg) • Respiratory acidosis results from decreased alveolar ventilation and subsequent hypercapnia • Acute respiratory failure – Associated with severe acidosis and only a small increase in the plasma bicarbonate – After 6–12 hours, the primary increase in Pco 2 evokes a renal compensation to excrete more acid and to generate more HCO3 – – Complete metabolic compensation by the kidney takes several days • Chronic respiratory acidosis – Generally seen in patients with underlying lung disease, such as chronic obstructive pulmonary disease – Renal excretion of acid as NH4Cl results in hypochloremia – When chronic respiratory acidosis is corrected suddenly, posthypercapnic metabolic alkalosis ensues until kidneys excrete excess HCO3 – over 2–3 days Clinical Findings • Acute respiratory acidosis: somnolence, confusion, mental status changes, myoclonus, asterixis • Severe hypercapnia – Increases cerebral blood flow, cerebrospinal fluid pressure, and intracranial pressure – Papilledema and pseudotumor cerebri may be seen Diagnosis • Low arterial pH (< 7.35), increased Pco 2 (> 48 mm Hg) • Serum HCO3 – is elevated (> 32 mEq/L or > 32 mmol/L) but does not fully correct the pH • If the disorder is chronic, hypochloremia is seen Treatment • Administer naloxone, 0.04–2.0 mg every 2–3 minutes intravenously or subcutaneously (or intramuscularly) x 3 doses if needed, for possible opioid overdose • For all forms of respiratory acidosis, treatment must aim to improve ventilation Content adapted from CURRENT Medical Diagnosis & Treatment 2013.
Posted on: Mon, 22 Dec 2014 14:05:58 +0000
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