Isoflurane provides better myocardial protection than midazolam in pediatric patients during open heart surgeries

Objectives: This study was designed to evaluate the applicability of anesthetic myocardial protection [pre-conditioning and minimization of reperfusion injury] using two anesthetic regimens on plasma levels of cardiac troponin T [cTnT], as a marker of myocardial ischemia, in pediatric patients assigned for surgical correction of congenital heart diseases using cardiopulmonary bypass [CPB]

Patients and Methods: The study included 60 patients [36 males and 24 females]. Patients were randomly allocated in 2 equal groups: Midazolam group received a continuous infusion of midazolam [0.2 mg/kg/hour] and Isoflurane group maintained by an end-tidal concentration of isoflurane of 1-1.5% throughout the operation. Six blood samples were taken for estimation of plasma cTnT levels immediately after induction of anesthesia [S1], 8- hours [S2], 16-hours [S3], 24-hours [S4], 36-hours [S5] and 48-hours [S6] after aortic cross-clamping

Results: Plasma cTnT levels estimated after aortic cross-clamping [S2-S6] showed a significant [P1<0.001] elevation in both groups compared to levels estimated in S1 sample. Moreover, plasma cTnT levels showed a progressive increase in all patients irrespective of anesthetic regimen used reaching a peak levels in S4 sample and started to decline thereafter but still significantly higher compared to levels estimated in S1 sample. Plasma cTnT levels estimated in S2 sample showed a non-significant increase in midazolam group compared to levels estimated in isoflurane group. On contrary, plasma cTnT levels estimated in midazolam group at 16, 24, 36 and 48 hours after aortic cross-clamping were significantly higher [P[6]=0.034, 0.01, <0.001 and =0.031, respectively] compared to levels estimated in isoflurane group. In midazolam group, there was a positive significant correlation between mechanical ventilation time and plasma cTnT levels estimated at 24-hours [r=0.413, p=0.023], respectively. However, such correlations were non-significant despite being positive in isoflurane group, [r=0.265, p>0.05]

Conclusion: It could be concluded that the hypothesis of anesthetic myocardial protection [preconditioning and minimization of reperfusion injury] is applicable for pediatric patients with congenital heart disease who are assigned for cardiac surgery. Isoflurane-based anesthesia minimized myocardial ischemic and reperfusion injury and provided efficient cardioprotection irrespective of the type of cardiac lesion

Comparison between two regimens of prophylactic tranexamic acid administration in re-operative coronary revascularization patients

Repeated cardiac operations are increasing in number and represent a group particularly at risk for bleeding. Bleeding during cardiac surgery is due in part to the activation of the fibrinolytic system and the systemic inflammatory response. Although tranexamic acid [TA] is used to reduce bleeding after cardiac surgery, there is large variation in the recommended dose. The dose of prophylactic tranexamic acid administered in CABG using CPB and in particular in redo cases has not been adequately studied. This prospective randomized double-blinded study aims to compare the efficacy of two regimens of prophylactic TA administration to reduce bleeding and blood transfusion in redo CABG. 120 adult patients undergoing redo coronary revascularization using CPB were randomly divided into two equal groups. Patients in group A received a loading dose infusion of TA 10 mg.kg[-1] over 20 minutes before sternotomy, followed by 1 mg.kg[-1] hr[-1] infusion over the following 6 hours. While patients in group B received a loading dose of TA of 25 mg.kg[-1] infused intravenously over 20 minutes before sternotomy, followed by placebo infusion over the following 6 hours. The anesthetic and surgical techniques and the anticoagulation protocol were standardized for all patients. There was no statistically significant difference between the two groups regarding the demographics, preoperative and operative characteristics. The postoperative platelet counts and prothrombin times show no statistically significant change between both groups, while the postoperative PIT [51.7 +/- 1.94 seconds versus 50.9 +/- 1.99 seconds] and hematocrit [23.2 +/- 0.95% versus 22.8 +/- 0.92%] show statistically significant higher level in Group A [p value <0.001]. The blood loss shows highly significant decrease in group A [1114.9 +/- 50.22 versus 1350.74 +/- 22.5 ml] [p value <0.001]. The use of red blood cell transfusion shows highly significant statistical decrease in group A [p value <0.001]. While the platelet and fresh frozen plasma transfusion show statistically significant decrease in group A [p value <0.05]. The percentage of patients not receiving any blood product transfusion during or after operation shows statistically significant decrease in group A [p value <0.05]. The data regarding risk of complications potentially caused by hypercoagulability shows no statistically significant change between both groups. Administration of tranexamic acid loading dose infusion of 10 mg.kg[-1] over 20 minutes before sternotomy, followed by 1 mg.kg[-1] hr[-1] infusion over the following 6 hours, offers a better antifibrinolytic effect than a loading dose of 25 mg.kg[-1] infused intravenously over 20 minutes before sternotomy, reducing blood loss and requirement for transfusion in patients undergoing redo coronary revascularization without increasing the risk of hypercoagulability

Efficacy of lung recruitment maneuver on shunt fraction and oxygenation in one lung ventilation during sevoflurane anaesthesia

Deterioration of gas exchange during one lung ventilation [OLV] is caused by both total collapse of the nondependent lung and partial collapse of the dependent lung. It was demonstrated that an alveolar recruitment strategy [ARS] improves lung function during general anesthesia in supine patients. The objective of this article was to study the impact of this ARS on arterial oxygenation in patients undergoing OLV for lobectomies. Twelve patients undergoing open lobectomies were studied at three time points: [1] during two- lung ventilation [TLV], [2] during OLV before, and [3] after ARS. The ARS maneuver was done as follows: Peak inspiratory pressure [PIP] and PEEP were sequentially increased from 30/10 to 35/15 in steps. Every level of pressure was maintained during 1 minute. The recruitment pressure of 40/20 cm H[2]O was applied for 1 minute. The ARS took approximately 5 min. Airway pressures were then gradually decreased, returning to baseline settings but maintaining a PEEP level of 8 cm H[2]O. After the ARS was completed, the ventilator was, set back to volume control. The percent of shunt fraction was calculated using the formula Qs/Qt=CcO[2]-CaO[2]/CcO[2]-CvO[2]. Hemodynamic parameters [HR, MAP, CVP, MPAP and Paw] were measured at three time points [TLV, OLV [pre], OLV[ARS] there was significant decrease of MAP [p<0.03] after recruitment in relation to pre-recruitment. Also there was significant increase of MPAP after recruitment [p<0.002] in relation to OLVpre. The paw increased significantly [p<0.04] at OLV[ARS] in relation to OLVpre. Pa 02 was statistically significant lower during OLV before [120 +/- 65] compared with OLV after the recruitment 266 +/- 83 [p <0.01] and to TLV 348 +/- 77, [P< 0.001]. Pao2 values of the one recruited lung were not significant from the ones during TLV. Shunt fraction was calculated using a standard formula based on the three compartment model proposed by Riley and colleagues, it is increased significantly from 15.4 +/- 6.0 in TLV to 29.3 +/- 8.3 in OLV pre [p<0.003] Alveolar recruitment of the dependent lung augments Pa02 values during one-lung ventilation and corrects the percent of increased shunt fraction of the dependent lung