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Ms. O’Sullivan is a 65-year-old woman who arrived in the PACU 30 minutes ago following a right colectomy. She was extubated in the operating room. Her vitals are: BP 140/90, pulse 120 (regular), respiratory rate 30, temperature 37.5°C, and finger oximetry 80%. She is anxious and agitated and says that she wants to “leave right now and go home.”

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1. Until proven otherwise, what is the cause of agitation and/or disorientation in the postoperative recovery unit?

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2. Explain several causes of postoperative hypoxemia.

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Respiratory Distress

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If you are sitting comfortably reading this chapter, you are using about 3% of your energy in the work of breathing. Interestingly, the “driver” of this lung work is blood acidosis (actually CSF hydrogen ion concentration)—not oxygen. You are exquisitely sensitive to PCO2/pH. If you hold your breath for a minute, at the end of that minute your only wish is for another breath—breathing is high on everyone’s list of fun things to do. However, at the end of a minute of apnea, your PCO2 has risen from 40 mm Hg to only about 48 mm Hg. Therefore, a relatively tiny decrease in arterial pH (or increase in PCO2) translates into a profound stimulus to breathe.

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Case Analysis
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Mrs. O’Sullivan’s respiratory rate has increased to 30. We could attribute this to her “agitation,” but were we to check her arterial blood gas at this time, we would find:

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  • PO2: 55 mm Hg
  • PCO2: 30 mm Hg
  • pH: 7.48
  • O2 sat: 80%

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She has a respiratory alkalosis and is actually “overbreathing.” Her only abnormality is the drop in her hemoglobin saturation (O2 sat) that confers a 20% (100% minus 80%) decrease in arterial oxygen content, which can be completely compensated by a 20% increase in her cardiac output, resulting in a rock stable systemic oxygen delivery. The patient’s agitation has unquestionably pumped up her cardiac output at least the necessary 20%—so, what’s the problem? You decide that “everything is fine,” so you reassure the patient and the nurses and leave to check on another patient.

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Answers
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  1. Fifteen minutes later you get a call that Mrs. O’Sullivan is climbing out of bed, making a lot of noise, and bothering the other patients (and the nurses)—so, “Can we sedate her?”

    Warning: if you depress this patient’s respiratory drive with a sedative now, you will receive a follow-up call in 30 minutes that she just suffered a cardiac arrest. Agitation/irritability/confusion in the PACU/ICU is hypoxemia until proven otherwise, and should be cause for alarm! In most of us, the symptoms of hypoxemia are not an alteration in breathing volume/rate/pattern. Acute hypoxemia just makes a patient feel anxious and ...

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