I feel stupid even asking this question but I had a patient last night come from PACU following spinal surgery. She was an obese woman and the family reported that they thought she had sleep apnea but she had not been diagnosed. Patient came up on 4L NC. After I gave 1 mg of Dilaudid IV her sats dropped (I saw 66% at one point) so I put her on a nonrebreather mask. Patient later developed mental status changes although she could answer all orientation questions but she seemed a bit odd and slightly confused. Sats mostly maintained in the high 90s but occasionally she would get down to low 80s and I would have trouble getting her back up to 90s. I called doc and got stat ABGs and order for BIPAP. ABGs came back with pH 7.1 and PCO2 90. Doc said he couldn't understand how her gasses got this bad. Patient was awake and talking to family at this point. Is it possible that I did something wrong with the nonrebreather mask that was causing this patient to re-breathe her own CO2. Patient improved on BIPAP and was discharged today so she is apparently fine. Did I do something to cause this situation? Could sleep apnea alone have caused this? Sorry so long--thanks for any help.
Nov 8, '07
Tridil is right on.
Obese patients sometimes are natural CO2 retainers because of the physical weight of their chest wall (see Pickwickian syndrome or Obesity Hypoventilation Syndrome). I have had more than a couple patients like this. They are like COPD-ers in that they rely on a drop in pO2 to breathe as opposed to a rise in pCO2 like the rest of us. Their bodies are used to the increased pCO2 because of constant shallowing breathing and subsequent hypoventilation.
Anyway, my guess is that she was already a little more hypercapneic than usual from the surgery, and that combined with the high flow oxygen and narcotic allowed for a nice, steady increase in her pCO2 to a level that was high enough to make her loopy. The fact that her pCO2 was so high doesn't surprise me because remember, people like this (much like COPD patients) are used to being slightly hypercapneic. It would take more of a bump for them to show any signs or symptoms of the increase.
So, you did nothing wrong. That was not something one would easily catch unless they were quite familiar with the situation.
Last edit by VandyNurse714 on Nov 8, '07