Background: End-tidal carbon dioxide pressure (ETCO2) is commonly used as an indicator of arterial partial pressure of carbon dioxide (PaCO2) which reflects adequacy of ventilation during major surgeries. While accurate determination of PaCO2 level is an important aspect of anesthetic management of the patient it is all the way more important in neurosurgeries where changes in PaCO2 can have a profound effect on cerebral blood flow. Moreover practice of reducing intracranial pressure by means of hyperventilation is often used to reduce intracranial pressure in neurosurgical patients. There has also been some controversy in recent anesthetic literature about whether end tidalCO2 (ETCO2) is an accurate reflection of PaCO2. This study was aimed to evaluate the relationship between ETCO2 and arterial PaCO2 in neurosurgical patients undergoing craniotomy and to assess the predictive value of ETCO2 as an indicator of PaCO2 level.

Aims and Objectives:

1.      To study the correlation in between arterial to end tidal CO2 in neurosurgical patients undergoing

craniotomy.

1.      To study the correlation in between arterial to end tidal CO2 in neurosurgical patients undergoing craniotomy.

Materials and Methods: This was a prospective study conducted on 30 patients aged between 18 to 60 years who were posted for elective craniotomy under general anaesthesia at a major hospital in an urban area. The patients were included in the study after approval of the institutional ethical committee and written informed valid consent obtained from the patient. Patients were taken to operation theatre and routine pre anesthetic examination was done. Vitals were noted. All patients were anaesthetized using standard balanced general anaesthesia as per attending anesthesiologist and set protocol for neurosurgery cases. PaCO2 and PETCO2 were recorded immediately after induction followed by every hourly till end of surgery. Data was collected and statistical analysis was done with the help of SPSS Software version 15.

Results: Total 30 patients were studied. Out of these cases 18 were males and 12 were females with a maleto female ratio being 1: 0.66. The analysis of age group of the patients revealed that majority (36.66%) of the patients belonged to age group of 31-40 years. The percentage of patients in the age group of 21-30 years and 41-50 years was similar (20%). 12 (40%) patients belonged to ASA I category and 18 (60%) patients belonged to ASA II category. There was no patient belonging to other ASA categories as belonging to ASA I or ASA II category was the inclusion criteria of our study. Most common indication for surgery was meaningioma which was seen in 15 (50%) patients followed by glioma, Cerebellopontine angle tumor, schwannoma and glioblastoma which was seen in 6 (20%), 4 (13.33%), 3 (10%) and 2 (7.66%) patients respectively. All surgeries were uneventful. The analysis of PaCO2 and ETCO2 with respective to mean and standard deviations of pulse rate, Mean arterial pressure and central venous pressure during surgeries showed stable pulse rate, MAP and CVP throughout the surgical procedures thereby ruling out the fluctuations of these parameters as a cause of changes in PaCO2 and ETCO2. The data was analyzed for correlation between PaCO2 and ETCO2 at different intervals during craniotomy. Statistically significant correlation was found between PaCO2 and ETCO2 at baseline, 1hr, 2hr, 3hr and 4hrduring surgery.

Conclusion: In Our study there was a statistically significant correlation between PaCO2 and ETCO2 during elective neurosurgery patients undergoing craniotomy under general anaesthesia. Our study concludes that end-tidal CO2 (ETCO2) reflects arterial CO2 with acceptable accuracy and hence capnometry can be relied upon as a reflection of arterial PaCO2 in neurosurgical patients undergoing craniotomy.

Keywords: End tidal Co2, PaCO2, capnometry, Craniotomy.