A patient has coronary artery bypass graft surgery and is transported to the surgical intensive care unit at noon. He is placed on mechanical ventilation. Interpret his initial arterial blood gas levels:

• pH 7.31
• PaCO2 48 mm Hg
• Bicarbonate 22 mEq/L
• PaO2 115 mm Hg
• O2 saturation 99%

Rationale:

A. Pink-tinged sputum may occur postoperatively due to minor irritation or small amounts of bleeding from the respiratory tract. While it should be monitored, it does not require immediate intervention unless it becomes massive or bright red.

B. Mild to moderate pain at the chest tube site is expected postoperatively and can be managed with analgesics. Pain alone, without other acute signs, does not indicate an emergency.

C. Tracheal deviation is a sign of tension pneumothorax, which is a life-threatening emergency. Immediate intervention is required to relieve pressure in the pleural space and restore ventilation. The nurse should notify the provider immediately and prepare for emergency measures, such as needle decompression or chest tube adjustment.

D. Excessive drainage from a mediastinal chest tube may indicate postoperative hemorrhage, which can rapidly lead to hypovolemic shock. Immediate assessment and provider notification are necessary to prevent severe complications and initiate interventions.

E. Acute shortness of breath in a patient with a mediastinal chest tube can indicate pneumothorax, tube blockage, or cardiac/respiratory compromise. This is an urgent situation requiring immediate assessment, oxygen support, and provider notification.

Rationale:

A. pH 7.30; HCO3 22; PCO2 60; PO2 66 is incorrect because this reflects respiratory acidosis (low pH, elevated CO2). In the early stages of a pulmonary embolism, the client typically hyperventilates due to hypoxemia and anxiety, which lowers CO2 rather than increasing it. Elevated CO2 is more consistent with hypoventilation, not acute embolism.

B. pH 7.38; HCO3 22; PCO2 45; PO2 96 is incorrect because these values are essentially normal. A pulmonary embolism causes impaired perfusion and ventilation-perfusion (V/Q) mismatch, leading to hypoxemia. Normal oxygen levels would not be expected 15 minutes after an acute embolic event.

C. pH 7.47; HCO3 23; PCO2 25; PO2 82 is correct. Fifteen minutes after the onset of a Pulmonary embolism, the client typically develops acute respiratory alkalosis. The embolus blocks pulmonary blood flow, causing hypoxemia. In response, the client hyperventilates to compensate for low oxygen levels. Hyperventilation decreases PaCO2 (25 mm Hg), which increases pH (7.47), producing respiratory alkalosis. The HCO3 remains normal because renal compensation has not yet occurred (it takes hours to days). The PO2 is decreased (82 mm Hg), reflecting impaired oxygen exchange.

D. pH 7.30; HCO3 28; PCO2 65; PO2 75 is incorrect because this reflects respiratory acidosis with metabolic compensation (elevated CO2 and elevated bicarbonate). This pattern would be more consistent with chronic respiratory failure, not the early phase of an acute pulmonary embolism.