Assessment of splanchnic perfusion during cardiopulmonary bypass by continuous gastric tonometry and transesophageal echocardiography

Abdominal complications after cardiac surgery while relatively uncommon are associated with a significant mortality. Perioperative splanchnic ischemia appears to be an important cause of these complications. The aim of this study was to evaluate the effects of normothermic cardiopulmonary bypass [CPB] on splanchnic blood flow using Transesophageal echocardiography [TEE] Doppler-measured superior mesenteric artery blood flow and continuous gastric tonometry during coronary artery bypass graft surgery [CABG]. Twenty patients undergoing elective on-pump CABG were included in that Single-arm prospective observational study. Superior mesenteric artery blood flow [SMA-BF] was measured with duplex ultrasound using TEE probe, while gastric mucosal perfusion was assessed using continuous gastric tonometry during CABG surgery under normothermic [>35°C] CPB. Measurements were made six times: Tl [after induction of anesthesia], T2 [after initiation of CPB], T3 [30 min on bypass], T4 [60 min on bypass], T5 [5 min after weaning from CPB], T6 [end of surgery]. Also blood samples were collected for arterial blood lactate levels. SMA-BF showed a highly significant decrease from baseline value [p value < 0.01] after initiation of CPB [T2] till its end [T4] and increased shortly after bypass then decreased again significantly below baseline at the end of surgery [T6]. While gastric mucosal CO[2]gap [Pg-aCO[2] gap] showed a highly significant increase from baseline value [p value < 0.01] 30 minutes after CPB initiation [T3] then 5 minutes after weaning from CPB [T5] and at the end of surgery [T6], however no correlation was found between both variables. This study showed that normothermic CPB is associated with a significant reduction of both SMA-BF and gastric mucosal blood flow, however the splanchnic blood flow reduction alone cannot account for mucosal ischemia which may even become worse when blood flow is restored. Transesophageal echo-Doppler allows the intraoperative measurement of blood flow distribution to splanchnic viscera and may be considered a reliable tool specially when coupled with arterial lactate measurement and gastric tonometry to expect which patients well develop splanchnic ischemia during CPB

impact of preemptive phosphodiesterase III inhibition on left ventricular diastolic performance after valve replacement for aortic stenosis

Left ventricular diastolic dysfunction [LVDD] in aortic stenosis is an important independent risk factor for early and late postoperative mortality. We hypothesized that enoximone or milrinone, administered after releasing the aortic cross-clamp improved the diastolic function of the left ventricle as assessed by transesophageal echocardiography [TEE] in patients with aortic stenosis undergoing aortic valve replacement. Forty-five adult patients with valvular aortic stenosis and preserved systolic function scheduled for primary aortic valve replacement were randomly assigned to one of three equal groups; in group M [milrinone group, n = 15] patients received milrinone with a loading dose of 50 microg/kg followed by an infusion of 0.5 microg/kg/min for 6 hours. In group E [enoximone group, n = 15] patients were given enoximone after release of aortic cross-clamp, with an initial bolus of 0.5 mg/kg followed by a continuous infusion of 2.5 microg/kg/min for 6 hours, and in group C [control group, n = 15] patients received saline bolus and infusion at the same time and interval as the first two groups. Hemodynamic parameters and transesophageal echocardiographic assessment of left ventricular end-diastolic area [EDA], transmitral inflow velocity, and tissue doppler imaging [TDI] of the mitral annulus parameters were assessed pre-bypass [Tl], post-bypass [12] after administration of the test drug and separation from CPB, and at the end of the operation after chest closure [T3]. Cardiac index showed a statistically significant increase [p < 0.05], while the systemic vascular resistance showed statistically significant decrease [p < 0.05] in T2 and T3 compared to Tl in the three groups. Cardiac index was significantly higher [p < 0.05] and the systemic vascular resistance was significantly lower [p < 0.05] in T2 and T3 in both the milrinone and enoximone groups compared to the control group at the same intervals. Left ventricular end-diastolic area showed a decrease in all groups which was statistically significant [p < 0.05] comparing T2 and T3 to Tl but without intergroup difference. Peak E-wave velocity, peak A-wave velocity and E/A ratio of the transmitral flow were comparable in the three groups. E-wave deceleration time was significantly decreased [p < 0.05] in T2 and T3 in the three groups. Tissue Doppler analysis of the peak early mitral annular velocity revealed no significant difference between the three groups. The administration of milrinone or enoximone after release of aortic cross-clamp in valve replacement for aortic stenosis did not improve ventricular diastolic function and failed to show increase in the indices of compliance and relaxation compared to the control

Effect of lung insufflation with oxygen or air during cardiopulmonary bypass on post-bypass pulmonary dysfunction

Cardiopulmonary bypass [CPB] causes various abnormalities in the physical and functional properties of the lungs that initiate increases in pulmonary capillary endothelial permeability, decreases in lung compliance, and impaired gas exchange during the immediate postoperative period. This prospective randomized clinical trial was designed to investigate the effect of insufflating the lungs with 100% oxygen or air versus totally disconnecting the lungs and leaving them to collapse during cardiopulmonary bypass. Fifty-six adult patients undergoing CABG surgery with total CPB and aortic cross-clamping were included. Patients were randomly allocated to 1 of 3 groups that differed only in respiratory management during CPB; Group I [O [2] group, n=19] received 100% oxygen insufflation at 4 L/min. Group II [Air group, n=19] received air [FiO[2] 0.2] at the same flow rate. Group III [Collapse group, n=18] were totally disconnected from the anesthesia machine, and their lungs were left to collapse. PaO[2]/FiO[2] was significantly reduced in O2and Collapse groups in the post-CPB measurement compared to baseline but not in Air group [p<0.05]. In the postoperative period PaO[2]/FiO[2] was significantly higher in Air group compared to O[2] group, measured at 1 hour and 4 hours postoperatively [473 + 60 vs 407 + 90, and 476 +/- 39 vs 416 +/- 73 respectively, p<0.05] denoting a more rapid recovery of the lungs. Static and dynamic lung compliance were significantly reduced in the post-CPB and postoperative measurements in 0[2] and Collapse groups, but not in Air group [p<0.05]. Bronchoalveolar lavage [BAL] cytolines [TNF-alpha and IL-8] were significantly elevated in the post-CPB measurement in 02 group compared to baseline [12.1 [0 -42.1] vs 1 [0 - 17] pg, and 674 [50 - 8767] vs 217 [<10 - 2076] pg respectively, p<0.05], but not in Air or Collapse groups. TNF-alpha and IL-8 were significantly higher in O[2] group in the post-CPB measurement compared to both other groups [p<0.05]. Lung insufflation with air [without the application of mechanical ventilation or CPAP] during CPB has attenuated post-CPB pulmonary dysfunction compared to insufflation with 100% oxygen or disconnecting the lungs and leaving them to collapse. Oxygen on the other hand has caused an inflammatory response as evident by an increase in BAL cytokines

protective effect of magnesium on the neurocognitive function in hypothermic circulatory arrest and retrograde cerebral perfusion for aortic arch surgery

Background: Neuropsychological dysfunction is a major complication of thoracic aortic surgery with hypothermic circulatory arrest [HCA]. Magnesium has been shown to have neuroprotectant effect in acute stroke and in short term neurological dysfunction after cardiopulmonary bypass. We sought to study the effect of magnesium on the neuropsychological function after HCA for aortic arch surgery using retrograde cerebral perfusion [RCP]

Methods: Forty patients scheduled for elective thoracic aortic surgery including the arch using HCA with RCP were randomly assigned to two equal groups. The magnesium group received magnesium sulfate to increase plasma magnesium level between 1.5 to 2 folds throughout the operation and for 24 hours, while the placebo group received normal saline over the same period as a control. The patients' neurocognitive state was assessed by cognitive P300 visual evoked potentials and the revised Wechsler Adult Intelligence Scale done the day before the operation and 2 weeks postoperatively. P300 was assessed as area under the curve [AUC] between 280 and 600 ms and center of this area [Ct [time], Cv [voltage]]. The ratio of these parameters acquired by target [TG] and non-target [NTG] stimulus [TG/NTG], was calculated to assess concentration on TG stimulus and defined as concentration index [CI: CI[AUC], CI[Ct], and CI[Cv]]

Results: There were no stroke, seizure, or hospital mortality in either group. Preoperatively, in the magnesium group, AUC and Cv acquired by TG stimulus in both Cz and Fz leads were significantly altered postoperatively [P value <0.05]. In the placebo group, no significant postoperative change was observed in all leads on TG stimulus. Postoperative CI [Ct] in the placebo group, were significantly impaired in all leads. The revised Wechsler Adult Intelligence Scale shows significant decline between baseline and postoperative scores in three subtests [digit span P value <0.05, arithmetic, and picture completion P value <0.01] for magnesium group and four [digit span, arithmetic, picture completion, and picture arrangement P value <0.01] for placebo group. Statistical difference between groups in test score changes was found in one subtest [picture arrangement P value <0.05]

Conclusion: Magnesium administration in patients undergoing aortic arch surgery with hypothermic circulatory arrest using retrograde cerebral perfusion did not affect the neurocognitive outcome assessed by cognitive P300 visual evoked potentials and the revised Wechsler Adult Intelligence Scale, further work is needed to prove any protective value for magnesium in this context