Fauzia Anis Khan, Mueenullah Khan, Shemila Abbasi.
Arterial to end-tidal carbon dioxide difference in neurosurgical patients undergoing craniotomy: a review of practice.
J Pak Med Assoc Jan ;57(9):446-8.

Objective: To see if PETCO2 reflects PaCO2 with acceptable accuracy. Methods: In this audit the anaesthetic chart of fifty consecutive patients, age 12 years and above undergoing craniotomy for intracranial pathology, were reviewed. Results: The difference between end tidal carbon dioxide (ETCO2) value corresponding to the time of taking the arterial sample and the PaCO2 was calculated. The mean end tidal CO2 was 29.3+ 2.8 and the mean PaCO2 was 32.63+ 4.5. The mean difference between the two values was calculated as 4.09 + 3.0. The regression coefficient was 0.496, which showed a moderate association. A wide variability was observed in the results. Conclusion: Based on our results we recommend that arterial samples should be taken to determine PaCO2 in neurosurgical patients where maintenance of cerebral blood flow is crucial e.g. cerebral aneurysm surgery (JPMA 57:446:2007).

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