Kothai, S (2009) Comparison of the PaCO2 - EtCO2 Gradient between the Pre Cardio Pulmonary Bypass and the Post Cardio Pulmonary Bypass Period in Patients Undergoing Coronary Artery Bypass Graft. Masters thesis, Christian Medical College, Vellore.
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Abstract
INTRODUCTION: Knowledge and control of arterial CO2 is an essential part of anaesthesia especially during cardiac surgery. To determine the adequacy of alveolar ventilation it is important to know PaCO2. Capnography constitutes a useful and non invasive means of continuously measuring EtCO2 which usually correlates with PaCO2. In normal individuals the arterial- End tidal CO2 difference (PaCO2-EtCO2 gradient) may vary from 2-5 mm Hg. But several factors like hypotension, decrease in pulmonary blood flow can result in alteration in ventilation-perfusion ratio. This in turn, alters the alveolar dead space and affects arterial- alveolar CO2 difference. During cardio pulmonary bypass there is considerable alterations in ventilation-perfusion ratio and alveolar dead space which may extend into the post cardio pulmonary bypass period. It is important to know the PaCO2-EtCO2 gradient variation during cardiac surgery and identify the factors causing this variation. Hence we decided to study the Arterial – End tidal CO2 gradient in the pre cardio pulmonary bypass period and compare it to the post cardio pulmonary bypass period in patients undergoing coronary artery bypass graft. AIM OF THE STUDY: 1. To study and compare the relationship of PaCO2- EtCO2 gradient between pre cardio pulmonary bypass and post cardio pulmonary bypass period. 2. To find out if any factor affects this gradient. MATERIALS AND METHODOLOGY: We did a preliminary study on ten patients who underwent elective CABG surgery. The PaCO2-EtCO2 gradient was calculated in pre bypass and post bypass period. The main purpose of this preliminary study was 1. To study and compare the relationship of Arterial CO2 - End tidal CO2 gradient between the pre cardio pulmonary bypass and post cardio pulmonary bypass period. 2. To calculate the sample size required for the study. Sample Size: From the preliminary study, the sample size was calculated in order to derive statistically significant conclusions. The required sample size to show a significant change in PaCO2-EtCO2 gradient in pre cardio pulmonary and post cardio pulmonary bypass period was found to be 33 subjects with 80% power and at 5% level of significance. Inclusion Criteria: 1. All the patients undergoing elective CABG surgery. 2. Patients willing to participate in the study. Exclusion Criteria: 1. Patients with severe pulmonary disease (FEV1=< 50% of predicted value). 2. Patients not willing to participate in the study. METHOD OF STUDY: All the patients undergoing elective CABG were visited pre operatively, the nature of the study explained to them and written consent taken. They were pre medicated with Tab. Diazepam 5 mg the night before surgery and Tab. Diazepam 7.5 mg 30 min before induction. They were shifted to the operating room with O2 mask 6 Liters/min in propped up position. Monitoring was established with pulse oximeter and ECG. A peripheral venous catheter was inserted, 500 ml of normal saline infusion started. Radial artery cannulation was done subsequently for invasive arterial pressure monitoring. After pre oxygenation with 100% O2, Anaesthesia was induced with Inj. Midazolam 0.05-0.1 mg/kg; Inj. Fentanyl 2-3 mcg/kg and inhalational anaesthetic Sevoflurane 2-6 % conc (or) Isoflurane 2-3% conc. Patients were paralyzed with Vecuronium 0.1 mg/kg (or) Pancuronium 0.1 mg/kg and ventilated for maximum of 5 minutes. Hypotension during this period was managed with small bolus doses of Inj. Phenylephrine 25-50 mcg. Endotracheal intubation was done and bilateral air entry checked. A central venous catheter was inserted through Right Internal jugular vein for central venous pressure monitoring and for administration of inotropes. A naso pharyngeal temperature probe was inserted to measure the temperature. As a protocol of this institution, adrenaline infusion was started at 0.1 mcg/kg up to 0.2 mcg/kg in the post bypass period. CONCLUSION: This study has demonstrated that there is an increase in the PaCO2/EtCO2 gradient in the post CP Bypass period as compared to the pre CP Bypass time. The increase in the body temperature during weaning from CP Bypass correlates with the increase in gradient. The increased CO2 production results in an increase in PaCO2; but this does not result in a parallel increase in EtCO2 probably because of the increase in dead space induced by decrease in cardiac output in the post CP Bypass period. The occurrence of increased CO2 gradient in the post CP Bypass period suggests that we should corroborate ETCO2 monitoring with arterial blood gas estimation to see the adequacy of ventilation when fixing ventilator settings to avoid possible respiratory acidosis.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Paco2 - Etco2 Gradient ; Pre Cardio Pulmonary Bypass ;Post Cardio Pulmonary Bypass P; Patients ; Undergoing Coronary Artery Bypass Graft ; Comparison Study. |
| Subjects: | MEDICAL > Anaesthesiology |
| Depositing User: | Subramani R |
| Date Deposited: | 30 Apr 2018 02:53 |
| Last Modified: | 30 Apr 2018 02:53 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/7318 |
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