Mixed venous versus central venous oxygen saturation in patients undergoing on pump beating coronary artery bypass grafting

To examine the validity of central venous oxygen saturation [ScvO 2] as a numerical substitution of mixed venous oxygen saturation [SvO 2] in adult patients undergoing normothermic on pump beating coronary artery bypass grafting [CABG]. Prospective clinical observational study was done at King Khalid University Hospital, King Saud University, Riyadh, Kingdom of Saudi Arabia. Thirty four adult patients scheduled for coronary artery surgery were included. Patients were monitored by a pulmonary artery catheter [PAC] as a part of our routine intraoperative monitoring. SvO 2 and ScvO 2 were simultaneously measured 15 minutes [T1] and 30 minutes [T2] after induction of anesthesia, 15 and 30 minutes after initiation of cardiopulmonary bypass [T3 and T4], and 15 and 30 minutes after admission to intensive care unit [T5 and T6]. ScvO 2 showed higher reading than SvO 2 all through our study. Our results showed perfect positive statistically significant correlation between SvO 2 and ScvO 2 at all data points. Individual mean of difference [MOD] between both the readings at study time showed MOD of 1.34 and 1.44 at T1 and T2 simultaneously. This MOD was statistically insignificant, but after on pump beating normothermic bypass was initiated; MOD was 5.2 and 4.4 at T3 and T4 with high statistical significance. In ICU, MOD continues to have high statistical significance, MOD was 6.3 at T5 and at T6 it was 4.6. In on pump beating CABG patients; ScvO 2 and SvO 2 are not interchangeable numerically. ScvO 2 is useful in the meaning of trend; our data suggest that ScvO 2 is equivalent to SvO 2, only in the course of clinical decisions as long as absolute values are not required

effect of positive pressure ventilatory patterns on post-bypass lung functions

This study aimed at evaluating the effect of application of different patterns of positive ventilatory pressure either during or after cardiopulmonary bypass [CPB], on lung functions. 30 patients undergoing coronary artery revascularisation under the management of CPB were randomly allocated into 3 groups. Group I [VCM] 10 patients were subjected to manual vital capacity manoeuvre [VCM] before weaning off the CPB. Group II [CPAP] 10 patients were subjected to continuous positive airway pressure [CPAP] of 10 cm H[2]O during CPB. Group III [PEEP] 10 patients were subjected to positive end expiratory pressure [PEEP] of 7 cmH[2]O after weaning off the CPB. Measurements included the PO[2] PCO[2] together with derived calculated parameters as the alveolar-arterial oxygen difference [P [A-a] DO[2]] and shunt fraction, as welt as the dynamic lung compliance being recorded directly from the anesthetic and ventilatory equipments. All readings were taken on closed chest and on FiO[2] of 0.5. Intraoperative anesthetic and surgical data as well as postoperative extubation time and length of ICU stay were also evaluated. Statistical analysis of ventilatory parameters showed no significant differences for both PO[2] and PCO[2] in between the studied groups. Alveolar-Arterial oxygen difference mean values were comparable in the 3 studied groups. The mean values of intrapulmonary shunt fraction showed a significant difference in relation to the baseline values in Group I [VCM] and Group III [PEEP] at 30 minutes after ICU admission and 4 hours post CPB with estimated P value <0.01 and <0.05 respectively, while in Group II [CPAP] mean values started to be significant after chest closure with a P value <0.05, but there was no significant intergroup differences with a P value >0.01. Dynamic lung compliance mean values showed no intergroup statistical significance. Maintenance of ventilatory parameters was achieved in all the positive pressure ventilatory methods applied, either being applied during or after CPB