Comments on: Acid base answer http://www.medrants.com/archives/4289 Internal medicine, American health care, and especially medical education Sat, 11 Feb 2012 15:15:48 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: cory http://www.medrants.com/archives/4289/comment-page-1#comment-527285 cory Thu, 28 May 2009 11:55:07 +0000 http://www.medrants.com/?p=4289#comment-527285 Good for your teacher on the blood gas point. And the CO2/ventilation comment is spot-on. People often use hyperventilate as a lay term (when it's precise meaning is low CO2) when they mean tachypnea (rapid respiratory rate). Acid-base problems can't be divined precisely without blood gases and blood gases are becoming a lost art. Couple of points to mention- the natural acid base status of advanced stable cirrhosis is a mild respiratory alkalosis- reasons may include - stimuli to breathe including ascites, chronic anemia, mild hypoxemia from AV shunting, and increased progesterone levels. I never used less than 40% FIO2 on the ventilator (with the possible exception of a CO2 retainer who we were looking to wean and we were going with slightly lower pO2's). Yes, I know the pO2 of 112 is more than adequate but if anything goes wrong with a patient, barotrauma, pulmonary complication, cardiac problem providing an FIO2 of 40%, which is nontoxic and has no obvious downsides (except possibly in the occasional CO2 retaining COPD patient) provides an extra margin of safety. The risk-benefit of FIO2 of 40% at all times as opposed to lower FIO2s seems indisputable and no one has ever explained to me why it might not be right. I used to ask this of every visiting professor in the ICU and never got a satisfactory answer why a minimum FIO2 of 40% shouldn't be the default. Good for your teacher on the blood gas point. And the CO2/ventilation comment is spot-on. People often use hyperventilate as a lay term (when it’s precise meaning is low CO2) when they mean tachypnea (rapid respiratory rate). Acid-base problems can’t be divined precisely without blood gases and blood gases are becoming a lost art.

Couple of points to mention- the natural acid base status of advanced stable cirrhosis is a mild respiratory alkalosis- reasons may include – stimuli to breathe including ascites, chronic anemia, mild hypoxemia from AV shunting, and increased progesterone levels.

I never used less than 40% FIO2 on the ventilator (with the possible exception of a CO2 retainer who we were looking to wean and we were going with slightly lower pO2′s). Yes, I know the pO2 of 112 is more than adequate but if anything goes wrong with a patient, barotrauma, pulmonary complication, cardiac problem providing an FIO2 of 40%, which is nontoxic and has no obvious downsides (except possibly in the occasional CO2 retaining COPD patient) provides an extra margin of safety. The risk-benefit of FIO2 of 40% at all times as opposed to lower FIO2s seems indisputable and no one has ever explained to me why it might not be right. I used to ask this of every visiting professor in the ICU and never got a satisfactory answer why a minimum FIO2 of 40% shouldn’t be the default.

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