Question

4. Metabolic acidosis often occurs in patients with impaired circulation following cardiac arrest. Mechanical hyperventilation cannot be used as a treatment if they have acute lung injury (ALI). Instead, a compound called Tris is used.

1. If no ALI is present, how would mechanical hyperventilation help?

2. Would treatment of acidosis with sodium bicarbonate be effective in treating patients with metabolic acidosis a) in the presence and b) in the absence of ALI?

3. Explain how Tris works to treat metabolic acidosis, and why this would be acceptable for patients with ALI.

Answer 1

a, For the early initiation mechanical hyperventilation, can fulfill the patient high respiratory drive and there will be less chance of ALI. Hyperventilation increases blood PH and normalizes cellular function. hypocapnia affects arterial blood oxygenation, hyperventilation increases the arterial o2tension and normalizes the acid-base condition.
b, Metabolic acidosis compromises normal cellular function. using sodium bicarbonate to treat metabolic acidosis is controversial. Tris hydroxymethyl aminomethane(THAM) can be an effective method to control acidosis, THAM excreted by the kidney, so co2 production will not rise, it control the arterial PH and decreases arterial co2 tension. it is an effective alteration for sodium bicarbonate for treating acidosis with ALI.
c, Permissive hypercapnia acceptable to treat patients with ALI. patient tolerate respiratory acidosis until renal compensation correct arterial PH. THAM has more buffering capacity than bicarbonate, it will be effective in metabolic acidosis. THAM avoided respiratory compensation with mechanical ventilation to avoid lung injury.