Asthma, PICU — Evaluation of Hypoxemia and Hypercarbia — Clinical Pathway: Inpatient and ICU

Acute Asthma Exacerbation Clinical Pathway — PICU

Evaluation of Hypoxemia and Hypercarbia

Hypoxemia usually due to ventilation-perfusion mismatch

  • Decreased ventilation: mucus plugging, regional atelectasis, bronchospasm
  • Inappropriate perfusion: systemic beta agonist effect (vasodilation)
SpO2 Air Entry (PASS) FiO2 Recommendations
> 90% Adequate < 50% No change needed
< 90% Adequate (PASS 0-3) Any Consider stopping continuous albuterol
< 90% Poor (PASS 4-6) < 50% Consider continuing continuous albuterol via NIPPV
< 90% Poor (PASS 4-6) > 50% Prompt alert to attending physician
  • Most commonly patients are tachypneic (respiratory alkalosis/low CO2)
  • RISING CO2 is concerning and can be indicative of worsening status and impending respiratory failure
  • Hypercarbia can have agitating or sedating effects
  • Generally mental status can be helpful in determining when to be concerned regarding hypercarbia.
Mental Status Role of blood gas
Reassuring
  • Limited utility in assessing for hypercarbia
  • Early in treatment can be helpful to evaluate for coexisting metabolic acidosis
Agitated/drowsy
  • Obtaining blood gas is suggested
  • If hypercapneic (pCO2 > 45)
    • Consider NIPPV per pathway which may help reverse hypercarbia
    • Discuss endpoints of failure with RT/RN/Medical team
  • If not hypercapneic (pCO2 > 45)
    • Consider TCOM for continued monitoring
Combative/obtunded
  • Obtaining blood gas is suggested
  • If hypercapneic (pCO2 > 45)
    • Ominous sign
    • Consider intubation and mechanical ventilation
    • Any trial of NIPPV requires a clear plan for the timing and criteria for treatment failure
  • If not hypercapneic (pCO2 > 45)
    • Concerning for unrelated CNS insult
    • Notify attending physician for additional work-up