Follow-up question blood gas analysis in the operating room
January 31, 2015 | 20,00 EUR | answered by Dr. med. Ralf Berg
Dear Dr. Berg,
I am back with a concern (you know, the one with the ascending PDA). This time I have a question regarding blood gas analyses (in the OR).
Let's assume you perform 2 capillary blood gas analyses. The results are as follows (temperature 37°):
BE: -1.7
Ph: 7.30
PCO2: 52.3 mmHg
PO2: 17.8 mmHg
SO2: Interferences (5)
BB: 46.3 mmol/L
30 minutes later, the following values are obtained:
BE: 1.0
Ph: 7.269
PCO2: 66.7 mmHg
PO2: 10.7 mmHg
BB: 49.0
O2 sat: 16.7%
I have the following questions:
Is it correct that capillary blood gas analyses are considered unreliable? Why are capillary blood gas analyses performed if they are not sufficiently informative? (I read about this on the internet, but I am not sure if I am correct).
Or is it the case that while capillary blood samples may not be as informative as arterial ones, they can still be used for diagnosis?
For example, as you can see, I have a very low PO2 value (once 17.2 and once 10.7 mmHg). Could it be that a capillary blood sample shows a PO2 value of 17.2, but in reality, I have a PO2 value of 30, 40, or even 50 mmHg?
In capillary blood gas values, are there only fluctuations, as opposed to arterial ones, or can capillary values not be taken seriously at all, and not used for evaluation?
The same applies to the SO2 value - once there are 5 interferences (what does "interferences" actually mean?) and once an O2 sat of only 16.7%, which seems very low.
Thank you in advance!
P.S.: One more question, could you possibly provide a response to the previous question (follow-up question)?
Best regards,
For the third time the answer very briefly so that it goes through in the end......the capillary BGAs are of course not to be discarded......
They are always worse than arterial BGAs, but indications and deviations from normal also exist here.
In your case, you can definitely see:
1. the partial pressure of CO2 is elevated, and has further increased after 30 minutes.
2. the partial pressure of oxygen is decreased and has deteriorated further.
3. under normal conditions, the arterial PO2 differs from the venous/capillary pO2 by 3-4% in extreme cases (coronary vessels) by 7%.
Everything else is no longer physiological, so pathological.
In a hypoxia/circulatory depression/poisoning, etc., the oxygen fall can continue to rise, and with doubling of the physical exhaustion it may have reached 30, but it seems unlikely that there was an arterial partial pressure of 50 mmHg of oxygen.
One can already take this as evidence that there was hypoxia, which also increased after 30 minutes.
The FiO2, the fraction of erythrocytes with oxygen molecule, could not be determined in the first BGA due to interference = interfering signals. What the (5) means, I do not know. Possibly an indication of what kind of error (error no. 5 of the manual (assumption)) has occurred. And the oxygen saturation of 16.7 not only sounds very low but is too low. Unfortunately, if one does not know where this value was derived from (usually the finger, but the earlobe is also conceivable), one cannot say whether hypoxia or hypotension, or finger cooling was causative. With rising SPA, all causes are possible.
If I now review everything, the following has PROBABLY happened:
With rising SPA, there was a drop in blood pressure, reduced spontaneous breathing, and ultimately an unquantifiable hypoxia. It is not entirely clear whether and what countermeasures were taken. It is clear that within the first 30 minutes, the situation was not normalized, only the third BGA is normal again. The situation was surely recognized (otherwise a BGA would not have been done, especially not repeatedly, it is not a routine measure), why artificial respiration was only initiated passively is not clear. Monitoring in the intensive care unit is okay. Ultimately, the problem was managed. However, I find it unfortunate that there is so little open communication with you. For the complication of rising, the anesthetist, unless a dosing error was made during the injection, cannot prevent it. This complication is named in the consent form and is often typical and unavoidable. That it took a bit long, at least as evidenced by the monitor data, until normality returned should be a reason to discuss the case in the department. However, since it was timely, and you were not harmed, there is no legal or liability relevance. Unfortunately, it is often the case that liability insurers silence the parties until their experts have assessed the liability risks.
If you want, simply call me directly, it is not as exhausting as these long comments. Before a judicial review, you can also seek the arbitration board of the responsible state medical association. This process is free for you, and since it is voluntary, it requires the consent of both parties. Then a specialist assesses all documents and gives an evaluation to the chamber lawyer as to whether a so-called medical error is present, or whether damage has occurred from the incident. In the former case, the chamber lawyer prosecutes (which is also free for you), in the latter case, a settlement is proposed for damage, or the damage allegation is rejected. Both parties still have the option of going to court afterward if they do not agree with the decision. In approximately 20% (figures from BAW), an error is found, which is confirmed in 90% of cases in court on appeal, in about 80% there is nothing found, which is confirmed in over 95% of cases in subsequent court proceedings.
I apologize for the technical wait time and hope that this answer will now be transmitted. With best regards, R. C. Berg
