Mr. P., age 65, was transferred to the ICU from the emergency department after s

Question

Mr. P., age 65, was transferred to the ICU from the emergency department after successful resuscitation from a cardiac arrest sustained out of the hospital. Initial diagnosis based on laboratory results and electrocardiography is acute anterior myocardial infarction. It is suspected that Mr. P. aspirated gastric contents during the cardiac arrest. He is orally intubated and receiving mechanical ventilation. His is on assist-control ventilation, respiratory set at 12 breaths/min, FiO2 of .40, PEEP 5 cm H2O. He opens his eyes to painful stimuli. An arterial blood gas is drawn upon arrival to the ICU and shows the following values: pH, 7.33; PaCO2, 40 mm Hg; HCO3-, 20 mEq/L; PaO2, 88 mm Hg; and SaO2, 99%. A decision is made to maintain the initial ventilator settings. The following day, Mr. P.’s chest radiograph shows progressive infiltrate. His oxygen saturation is dropping below 90% and he is demonstrating signs of hypoxemia: increased heart rate and premature ventricular contractions. Arterial blood gas analysis at this time shows pH, 7.35; PaCO2, 45 mm Hg; HCO3-, 26 mEq/L; PaO2, 58 mm Hg; and SaO2, 88%. The physician orders that the respiratory rate on the ventilator be increased to 16 breaths/min, FiO2 increased to .50, and PEEP increased to 10 cm H2O.What were the results of Mr. P.’s first arterial blood gas analysis? What factors are contributing to these results?
What factor is contributing to Mr. P.’s worsening condition the day after hospital admission?
Interpret the arterial blood gases done the day after the arrest.
Why did the physician change the ventilator settings after the second set of arterial blood gases?
What must the nurse assess after the addition of the PEEP? Why is this especially important for Mr. P.?

Explanation / Answer

Mr. P's first arterial blood gas analysis shows metabolic acidosis which is caused by lactic acidosis from hypoperfusion and/or beta-2 agonist effect of adrenaline administration.

The day after the admission Mr. P's condition was worsened most probably because of the development of aspiration pneumonitis from aspiration of acidic gastric contents.The results of ABG analysis done the day after the arrest demonstrate acute hypoxemia which shows chemical pneumonitis together with the chest radiographic findings characterized by the presence of infiltrates. To improve oxygenation and lung compliance , physician increased respiratory rate,FiO2 and PEEP. After the addition of PEEP,the nurse needs to assess volume status and cardiac output using a hemodynamic monitor. This is especially important in this case because hypotension and decreased cardiac output may occur with mechanical ventilation and PEEP, secondary to increased intrathoracic pressure, which can result in decreased venous return.

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