Onset Of Cardiopulmonary Bypass Research Articles

Vascular Reactivity during Cardiopulmonary Bypass in Patients at Punjab Institute of Cardiology and Shalamar Hospital Lahore, Pakistan

Background: The operative treatment of cardiac diseases remains associated with systemic inflammation and a suboptimal outcome in many patients. These inflammatory changes are manifested by systemic hypotension, myocardial failure, increased vascular permeability and consequent dysfunction of organs such as the lungs, gut and brain. In general terms, sympathetic innervations of the small arteries and arterioles allows vasoconstriction, thereby increasing resistance to blood flow, whereas innervations of the large arteries and veins decreases the volume in these vessels, resulting in the redistribution of blood volume. This study was conducted to determine the effect of vasodilator drugs on duration of vasodilatation in patients undergoing coronary artery bypass grafting (CABG) with Cardiopulmonary bypass (CPB).Methods: We evaluated prospectively the effect of vasodilator medications before CABG surgery on hemodynamic variables and use of vasoactive drugs. We studied 30 patients with good left ventricular function allocated randomly to continue vasodilator drugs before cardiac surgery. Arterial pressure, Cardiac output, systemic vascular resistance and use of vasoactive drugs were recorded during anaesthesia, perioperative and in the early postoperative period.Results: Patients who using vasodilator drugs before cardiac surgery had not significant relationship between vasodilator drugs and vessels reactivity (vasoconstriction & vasodilatation). However, these patients required more vasodilator drugs to control hypertension after CPB and in the early postoperative period.Conclusion: There was no difference in hypotension at the onset of CPB or in the use of vasodilator drugs before cardiac surgery. We conclude that vasodilator drugs before cardiac surgery did not have sufficient effect to be recommended routinely.

Modification of Vancomycin Dosing in Cardiac Surgery With Cardiopulmonary Bypass.

This study aims to assess the risk factors for insufficient vancomycin concentrations for its prophylactic use in adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and to modify the dosing regimen to achieve appropriate plasma concentrations. A total of 27 patients with vancomycin dosing of 1 to 1.5g based on a weight cutoff of 67kg were included, of which only 13 (48.15%) had vancomycin plasma concentration >15mg/L at surgical closure. Risk factors of vancomycin concentration <15mg/L at surgical-site closure were confirmed by multivariate logistic regression analysis, which showed that CPB duration was an independent predictor. Patients with CPB duration >4hours had significantly lower vancomycin concentrations and lower proportion in achieving target vancomycin concentration at the end of CPB and surgical closure. For patients with CPB >4hours, the modified dosing regimen that a second dose of 0.5 to 0.75g added at 4hours since the onset of CPB improved the target achievement of vancomycin concentration at surgical closure. Taken together, CPB duration >4hours was the risk factor for insufficient vancomycin concentration at surgical closure, while our modified dosing could improve the vancomycin concentrations for its prophylactic use in patients undergoing cardiac surgery with CPB.

Multimodal measurement of glycocalyx degradation during coronary artery bypass grafting.

Glycocalyx shedding and subsequent endothelial dysfunction occur in many conditions, such as in sepsis, in critical illness, and during major surgery such as in coronary artery bypass grafting (CABG) where it has been shown to associate with organ dysfunction. Hitherto, there is no consensus about the golden standard in measuring glycocalyx properties in humans. The objective of this study was to compare different indices of glycocalyx shedding and dysfunction. To this end, we studied patients undergoing elective CABG surgery, which is a known cause of glycocalyx shedding. Sublingual glycocalyx thickness was measured in 23 patients by: 1) determining the perfused boundary region (PBR)-an inverse measure of glycocalyx thickness-by means of sidestream dark field imaging technique. This is stated double, 2) measuring plasma levels of the glycocalyx shedding products syndecan-1, hyaluronan, and heparan sulfate and 3) measuring plasma markers of impaired glycocalyx function and endothelial activation (Ang-2, Tie-2, E-selectin, and thrombomodulin). Measurements were performed directly after induction, directly after onset of cardiopulmonary bypass (CPB), and directly after cessation of CPB. We assessed changes over time as well as correlations between the various markers. The PBR increased from 1.81 ± 0.21 μm after induction of anesthesia to 2.27 ± 0.25 μm (p < 0.0001) directly after CPB was initiated and did not change further during CPB. A similar pattern was seen for syndecan-1, hyaluronan, heparan sulfate, Ang-2, Tie-2, and thrombomodulin. E-selectin levels also increased between induction and the start of CPB and increased further during CPB. The PBR correlated moderately with heparan sulfate, E-selectin, and thrombomodulin and weakly with Syndecan-1, hyaluronan, and Tie-2. Shedding markers syndecan-1 and hyaluronan correlated with all functional markers. Shedding marker heparan sulfate only correlated with Tie-2, thrombomodulin, and E-selectin. Thrombomodulin correlated with all shedding markers. Our results show that glycocalyx thinning, illustrated by increased sublingual PBR and increased levels of shedding markers, is paralleled with impaired glycocalyx function and increased endothelial activation in CABG surgery with CPB. As correlations between different markers were limited, no single marker could be identified to represent the glycocalyx in its full complexity.

Modifying priming techniques in cardiopulmonary bypass circuit in known case of sickle-cell trait undergoing open heart surgery.

Modifying cardiopulmonary bypass (CPB) circuit's priming technique before the onset of CPB in cardiac patients known with sickle-cell disease or sickle cell trait has been observed to be of substantial significance in dealing with such challenges without having any life-threatening consequences. We modified our routine heparinized crystalloid priming of the CPB circuit with partial exchange transfusion by adding donor blood (packed red blood cells), fresh frozen plasma (FFP), and bicarbonate. This has helped us bring down the overall sickle cell hemoglobin in the blood thereby reducing its risk of sickling.

Dynamic responses of renal oxygenation at the onset of cardiopulmonary bypass in sheep and man.

The renal medulla is susceptible to hypoxia during cardiopulmonary bypass (CPB), which may contribute to the development of acute kidney injury. But the speed of onset of renal medullary hypoxia remains unknown. We continuously measured renal medullary oxygen tension (MPO2) in 24 sheep, and urinary PO2 (UPO2) as an index of MPO2 in 92 patients, before and after induction of CPB. In laterally recumbent sheep with a right thoracotomy (n = 20), even before CPB commenced MPO2 fell from (mean ± SEM) 52 ± 4 to 41 ±5 mmHg simultaneously with reduced arterial pressure (from 108 ± 5 to 88 ± 5 mmHg). In dorsally recumbent sheep with a medial sternotomy (n = 4), MPO2 was even more severely reduced (to 12 ± 12 mmHg) before CPB. In laterally recumbent sheep in which a crystalloid prime was used (n = 7), after commencing CPB, MPO2 fell abruptly to 24 ±6 mmHg within 20-30 minutes. MPO2 during CPB was not improved by adding donor blood to the prime (n = 13). In patients undergoing cardiac surgery, UPO2 fell by 4 ± 1 mmHg and mean arterial pressure fell by 7 ± 1 mmHg during the 30 minutes before CPB. UPO2 then fell by a further 12 ± 2 mmHg during the first 30 minutes of CPB but remained relatively stable for the remaining 24 minutes of observation. Renal medullary hypoxia is an early event during CPB. It starts to develop even before CPB, presumably due to a pressure-dependent decrease in renal blood flow. Medullary hypoxia during CPB appears to be promoted by hypotension and is not ameliorated by increasing blood hemoglobin concentration.

The evaluation of prevalence of poor distal leg perfusion in totally endoscopic cardiac surgeries: a cohort study

Introduction To ensure patient safety during Totally Endoscopic Cardiac Surgeries (TECS), patients are peripherally cannulated for coupling to the Cardiopulmonary Bypass (CPB) (1). Despite its necessity, the cannulated leg might experience clinically relevant ischemia (CRI), defined as a minimum of 15% Tissue Oxygenation Index (TOI) drop, lasting at least 4 minutes, possibly leading to poor peri- and postoperative clinical outcomes (2). TOI-values were assessed using non-invasive, Near-Infrared Spectroscopy (NIRS; 200NX-NIRO, Hamamatsu®, Japan) measurements of the skin covering the ipsilateral calf muscles. NIRS enables the quantification of the TOI, based on the difference in light absorption between oxygenated en deoxygenated haemoglobin molecules. The 200NX-NIRO has shown great sensitivity and specificity in the clinical setting (3-5). The objective was to evaluate the prevalence of poor distal leg perfusion related to short-term, peri-operative, CPB-time, since these data remain largerly unknown. Methods All consecutive patients 18 years or older, and scheduled for a TECS-based valve surgery (YIL AVR and/or MVATS), coronary surgery (ENDO ACAB or ENDO CABG), or a combination were included. Perioperative TOI-values were assessed at: baseline (B) = 5 minutes before insertion of the femoral arterial cannula (FAC); Event 1 (E1) = insertion of the FAC; Event 2 (E2) = onset of CPB; Event 3 (E3) = offset of CPB; Event 4 (E4) = removal of the FAC. Results 116 patients were included for statistical analysis. Differences between TOI-values were analysed using Wilcoxon signed rank tests. CRI in the cannulated leg was demonstrated in 18,80% (n = 22) of all cases, and showed significantly lower TOI-values for all events (E1, E2, E3 and E4) compared to the baseline TOI-value (Figure 1): p Discussion Although not all patients showed CRI in the cannulated leg, some degree of hypoperfusion was demonstrated over all cannulated legs. However, these are interim results and thus, further research regarding postoperative follow-up is necessary and might offer insights on how to prevent or prematurely treat ischemia and/or ischemia-related complications in the subclinical stage.

Microcirculatory perfusion disturbances following cardiopulmonary bypass: a systematic review

BackgroundMicrocirculatory perfusion disturbances are associated with increased morbidity and mortality in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Technological advancements made it possible to monitor sublingual microcirculatory perfusion over time. The goal of this review is to provide an overview of the course of alterations in sublingual microcirculatory perfusion following CPB. The secondary goal is to identify which parameter of sublingual microcirculatory perfusion is most profoundly affected by CPB.MethodsPubMed and Embase databases were systematically searched according to PRISMA guidelines and as registered in PROSPERO. Studies that reported sublingual microcirculatory perfusion measurements before and after onset of CPB in adult patients undergoing cardiac surgery were included. The primary outcome was sublingual microcirculatory perfusion, represented by functional capillary density (FCD), perfused vessel density (PVD), total vessel density (TVD), proportion of perfused vessels (PPV), and microvascular flow index (MFI).ResultsThe search identified 277 studies, of which 19 fulfilled all eligibility criteria. Initiation of CPB had a profound effect on FCD, PVD, or PPV. Seventeen studies (89%) reported one or more of these parameters, and in 11 of those studies (65%), there was a significant decrease in these parameters during cardiac surgery; the other 6 studies (35%) reported no effect. In 29% of the studies, FCD, PVD, or PPV normalized by the end of cardiac surgery, and in 24% percent of the studies, this effect lasted at least 24 h. There was no clear effect of CPB on TVD and a mixed effect on MFI.ConclusionCPB during cardiac surgery impaired sublingual microcirculatory perfusion as reflected by reduced FCD, PVD, and PPV. Four studies reported this effect at least 24 h after surgery. Further research is warranted to conclude on the duration of CPB-induced microcirculatory perfusion disturbances and the relationship with clinical outcome.Trial registrationPROSPERO, CRD42019127798

Microvascular Alterations During Cardiac Surgery Using a Heparin or Phosphorylcholine-Coated Circuit

Heparin biocompatible coating frequently is used to reduce inflammation and blood coagulation during cardiopulmonary bypass (CPB) in cardiac surgery. Whether heparin coating is protective or damaging to the vascular endothelium is unclear. The authors investigated whether heparin-coated (HC) circuits are associated with better preservation of microcirculatory perfusion and glycocalyx dimensions compared with nonheparin phosphorylcholine-coated (PC) circuits. Prospective, randomized blinded study. Tertiary university hospital. A total of 26 adults undergoing elective coronary artery bypass graft surgery with CPB. PC (n = 13) versus HC circuits (n = 13). Sublingual microcirculatory perfusion was measured before, during, and after CPB using sidestream dark field imaging and analyzed for perfused vessel density and perfused boundary region, an inverse parameter for glycocalyx dimensions. Onset of CPB was associated with an increase in perfused boundary region in the PC group that continued until the third postoperative day (2.0 ± 0.2 to 2.5 ± 0.2 µm; p = 0.018). This was paralleled by increased plasma syndecan-1 levels in the PC group. Contrastingly, both parameters remained unaltered in the HC group compared with baseline levels. CPB decreased perfused vessel density in both groups (CPB v pre-CPB: PC: 17 ± 2 to 13 ± 2 mm/mm2, p = 0.006; HC: 16 ± 2 to 11 ± 2 mm/mm2, p = 0.003) and remained equally altered in the first 3 postoperative days. The use of an HC circuit is associated with better preservation of the endothelial glycocalyx compared with PC circuits, whereas microcirculatory perfusion was disturbed equally in both groups. Hence, CPB-induced microcirculatory perfusion disturbances seem to be coating independent.

Adjusted calculation model of heparin management during cardiopulmonary bypass in obese patients: A randomised controlled trial.

Anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW). This may be inaccurate in obese patients and lead to heparin overdose with a risk of bleeding. To validate the efficacy and safety of an adjusted calculation model of heparin dosing based on ideal body weight (IBW) rather than TBW in obese CPB patients, with an expected target mean plasma heparin concentration of 4.5 IU ml after onset of CPB in the experimental group. Randomised controlled study. University hospital. Sixty obese patients (BMI ≥ 30 kg m) scheduled for CPB were included from January to June 2016. Patients received a bolus dose of unfractionated heparin of either 300 IU kg of TBW or 340 IU kg of IBW before onset of CPB. Additional adjusted boluses were injected to maintain an activated clotting time (ACT) of at least 400 s. Plasma heparin concentration and ACT were measured at different time points. Total heparin doses and transfusion requirements were recorded. The target heparin concentration of 4.5 IU ml was reached in the IBW group at the onset of CPB and maintained at all time points during CPB. Heparin concentrations were significantly higher in the TBW group after the bolus (6.52 ± 0.97 vs. 4.54 ± 1.13 IU ml, P < 0.001) and after cardioplegia (5.10 ± 1.03 vs. 4.31 ± 1.00 IU ml, P = 0.02). Total heparin doses were significantly higher in the TBW group. Mean ACT was significantly lower in the IBW group but remained over 400 s during CPB. The correlation between heparin and ACT was poor. Peri-operative bleeding and transfusion requirements were comparable. No thrombotic event occurred in the CPB circuit. The current IBW-adjusted regimen of heparin administration may be used efficiently in obese CPB patients, thereby avoiding overdose which cannot be accurately assessed by ACT monitoring alone. ClinicalTrials.gov identifier: NCT02675647.

Reduction of vascular leakage by imatinib is associated with preserved microcirculatory perfusion and reduced renal injury markers in a rat model of cardiopulmonary bypass

BackgroundCardiopulmonary bypass during cardiac surgery leads to impaired microcirculatory perfusion. We hypothesized that vascular leakage is an important contributor to microcirculatory dysfunction. Imatinib, a tyrosine kinase inhibitor, has been shown to reduce vascular leakage in septic mice. We investigated whether prevention of vascular leakage using imatinib preserves microcirculatory perfusion and reduces organ injury markers in a rat model of cardiopulmonary bypass. MethodsMale Wistar rats underwent cardiopulmonary bypass after treatment with imatinib or vehicle (n=8 per group). Cremaster muscle microcirculatory perfusion and quadriceps microvascular oxygen saturation were measured using intravital microscopy and reflectance spectroscopy. Evans Blue extravasation was determined in separate experiments. Organ injury markers were determined in plasma, intestine, kidney, and lungs. ResultsThe onset of cardiopulmonary bypass decreased the number of perfused microvessels by 40% in the control group [9.4 (8.6–10.6) to 5.7 (4.8–6.2) per microscope field; P<0.001 vs baseline], whereas this reduction was not seen in the imatinib group. In the control group, the number of perfused capillaries remained low throughout the experiment, whilst perfusion remained normal after imatinib administration. Microvascular oxygen saturation was less impaired after imatinib treatment compared with controls. Imatinib reduced vascular leakage and decreased fluid resuscitation compared with control [3 (3–6) vs 12 ml (7–16); P=0.024]. Plasma neutrophil-gelatinase-associated-lipocalin concentrations were reduced by imatinib. ConclusionsPrevention of endothelial barrier dysfunction using imatinib preserved microcirculatory perfusion and oxygenation during and after cardiopulmonary bypass. Moreover, imatinib-induced protection of endothelial barrier integrity reduced fluid-resuscitation requirements and attenuated renal and pulmonary injury markers.

Guidelines for the Diagnosis and Management of Critical Illness-Related Corticosteroid Insufficiency (CIRCI) in Critically Ill Patients (Part II): Society of Critical Care Medicine (SCCM) and European Society of Intensive Care Medicine (ESICM) 2017.

This part II of the guidelines for the diagnosis and management of critical illness-related corticosteroid insufficiency (CIRCI) in critically ill patients is related to acute illnesses that may be complicated by CIRCI. We followed strictly the same methodology as for part I (Supplemental Digital Co

The Effect of Autologus Blood Priming on Cerebral Oximetry in Congenital Cardiac Surgery Patients

Hemodilution is one of the sequelae of cardiopulmonary bypass (CPB). Autologous blood priming (retrograde autologous priming [RAP]/venous antegrade priming [VAP]) and acute normovolemic hemodilution (ANH) may be effective techniques to minimize hemodilution. The primary objective of this study is to investigate the impact of RAP/VAP combined with ANH on changes in cerebral saturations. A retrospective analysis of 52 patients undergoing congenital cardiac surgery requiring CPB between July 2014 and March 2015 was performed. Bivariate analysis correlated RAP/VAP and ANH volumes. SrO2 change scores were regressed on all covariates using multivariable least-squares models. The average percent of circulating blood volume (CBV) removed during RAP/VAP was 21 ± 10% in the cyanotic group and 15 ± 5% in the acyanotic group (p =.006). There was a decrease in SrO2 from 70 ± 11% at baseline to 55 ± 13% at CPB initiation, although this decrease did not differ by cyanosis (p = .668) or use of ANH (p = .566). Bivariate correlation and multivariable regression analysis of the SrO2 change score further demonstrated no statistically significant correlation between percent of CBV removed during RAP/VAP or ANH and the magnitude of the decline in SrO2. RAP and VAP help minimize hemodilution at the onset of CPB. This study further supports the use of these techniques in a pediatric population by demonstrating declines in SrO2 during RAP/VAP were consistent among cyanotic and acyanotic, including those who underwent ANH.

Renal tubular injury during cardiopulmonary bypass as assessed by urinary release of N-acetyl-ß-D-glucosaminidase.

Acute kidney injury (AKI) is a common complication with a major impact on morbidity and mortality after cardiac surgery with cardiopulmonary bypass (CPB). The aim of the present study was to perform a detailed analysis on the release of the tubular injury biomarker N-acetyl-b-D-glucosaminidase (NAG) during and early after CPB and to describe independent predictors of maximal tubular injury. We hypothesized that renal tubular injury occurs early after the onset of CPB. In this prospective observational study, we included 61 patients undergoing open cardiac surgery with an expected CPB duration exceeding 60min. The urinary NAG levels were measured at 30min intervals during CPB, as well as early (30min) after CPB and post-operatively. Independent predictors of tubular injury were identified using an Interquantile multivariate regression model. Already 30min after the onset of CPB, NAG excretion was significantly increased (P<0.001), followed by a sixfold peak increase after discontinuation of CPB (P<0.001). In the multivariable regression model, CPB duration (P<0.05) and the degree of rewarming during CPB (P<0.05), were independent predictors of peak NAG excretion. In cardiac surgery, a renal tubular cell injury is seen early after onset of CPB with a peak biomarker increase early after end of CPB. The magnitude of this tubular injury is independently related to CPB duration and the degree of rewarming. Efforts made to decrease the CPB duration and to avoid hypothermia and the need for rewarming may decrease the risk for tubular injury.

Accuracy of predicted haemoglobin concentration on cardiopulmonary bypass in paediatric cardiac surgery: effect of different formulae for estimating patient blood volume.

When applying a blood-conserving approach in paediatric cardiac surgery with the aim of reducing the transfusion of homologous blood products, the decision to use blood or blood-free priming of the cardiopulmonary bypass (CPB) circuit is often based on the predicted haemoglobin concentration (Hb) as derived from the pre-CPB Hb, the prime volume and the estimated blood volume. We assessed the accuracy of this approach and whether it may be improved by using more sophisticated methods of estimating the blood volume. Data from 522 paediatric cardiac surgery patients treated with CPB with blood-free priming in a 2-year period from May 2013 to May 2015 were collected. Inclusion criteria were body weight <15 kg and available Hb data immediately prior to and after the onset of CPB. The Hb on CPB was predicted according to Fick's principle from the pre-CPB Hb, the prime volume and the patient blood volume. Linear regression analyses and Bland-Altman plots were used to assess the accuracy of the Hb prediction. Different methods to estimate the blood volume were assessed and compared. The initial Hb on CPB correlated well with the predicted Hb (R2=0.87, p<0.001). A Bland-Altman plot revealed little bias at 0.07 g/dL and an area of agreement from -1.35 to 1.48 g/dL. More sophisticated methods of estimating blood volume from lean body mass did not improve the Hb prediction, but rather increased bias. Hb prediction is reasonably accurate, with the best result obtained with the simplest method of estimating the blood volume at 80 mL/kg body weight. When deciding for or against blood-free priming, caution is necessary when the predicted Hb lies in a range of ± 2 g/dL around the transfusion trigger.

REGIONAL CEREBRAL OXYGEN SATURATION IN VALVE SURGERY

Objective: To investigate regional cerebral oxygen saturation values and determine the correlation between regional cerebral oxygen saturation and cardiac output, cardiac index in valve surgical patients. Subjects and methods: A total of 51 valve surgical patients were enrolled in the study. Regional cerebral oxygen saturation and cardiac output (CO), cardiac index (CI) were measured during the phases of pre-induction, post-induction, onset of cardiopulmonary bypass (CPB), during CPB, the end of the CPB and before leaving theatre. Results: Regional cerebral oxygen saturation when patients breath room air was 63.5 ± 7.7% in right brain and 62.9 ± 6.8% in left one, and in the range from 56.7 ± 10.5% to 65.2 ± 10.5% during studying points. This values was lowest during CPB, 56.7 ± 10.5% and 57.3 ± 9.8% in in right brain and in left one, respectively. Regional cerebral oxygen saturation correlated positively with CO, CI during studying pointsexcept for CPB time. Conclusion: Baseline regional cerebral oxygen saturation was 63.5 ± 7.7% in right brain and 62.9 ± 6.8% in left one. The lowest values were during CPB. Regional cerebral oxygen saturationcorrelated well with CO, CI except for CPB time. Key words: Regional cerebral oxygen saturation, cardiac output, cardiac index

Changes in intraocular pressure during cardiopulmonary bypass.

The aim of the present study was to investigate the changes in intraocular pressures (IOP) in patients who underwent pulsatile and non-pulsatile cardiopulmonary bypass (CPB). A total of 42 patients operated for elective coronary bypass surgery (CABG) on CPB were randomly allocated to pulsatile (Group P) and non-pulsatile (Group N) groups. Pulsatile flow was applied to Group P patients during crops-clamp period. The IOP measurements were made before and after the induction of anesthesia, before the onset of CPB, on the 5th, 15th, 30th, 45th, and 60thmin of CPB, after CPB and at the end of the operation. The results of repetitive measurements were analyzed at different intervals and in two groups. The second IOP measurements of right and left eyes displayed statistically significant decreases from the baseline level [11.9±2.9 (p=0.0001) and 12.5±3.2 (p=0.0001), respectively]. The significant decrease in the IOP values persisted in the repeated measurements except for the 5thmin of CPB values [17.0±3.5 (p=0.346) and 16.7±3.6 (p=0.399)]. Comparison of two groups demonstrated significant differences at pre-CPB (right 12.8±2.3 vs. 10.8±2.4; p=0.013 and left 13.3±2.4 vs. 11.5±2.5; p=0.023), and 5thmin of CPB measurements (right 18.5±3.1 vs. 15.9±3.4; p=0.015; left 18.2±3.0 vs. 15.7±3.6; p=0.019). We noted a steady decrease in repeated IOP measurements except for the transient increase in CPB values on 5thmin. The IOP values were higher in pulsatile CPB group in pre-CPB and 5thmin of CPB measurements; however, the difference was not significant in the repeated measurements.

Abstract PR363

Background & Objectives: Postoperative brain damage is a serious problems in cardiac surgery patients. Dexmedetomidine and isoflurane have been reported to have neuroprotective properties in animal. But no report currently compares dexmedetomidine combined with isoflurane and isoflurane anesthesia on brain injury after cardiac surgery. Materials & Methods: 97 patients scheduled for valve replacement surgery with cardiopulmonary bypasses were randomly divided into 2 groups: dexmedetomidine and isoflurane (D-I, n=50) and isoflurane alone (I, n=47). Anesthesia was maintained with either dexmedetomidine and isoflurane or isoflurane alone combined with sufentanil. Dexemedetomidine was infused at 0.6 μg/kg for 15 min as a bolus, followed with 0.2 μg/kg/h until the end of surgery. The inhaled concentration of isoflurane was adjusted to keep the bispectral index (BIS) 40-50 throughout the procedure in both groups. Jugular blood samples were drawn for analysis of matrix metalloproteinase-9(MMP-9) and glial fibrillary acidic protein levels(GFAP) peri-operatively: before induction; 5 min after cardiopulmonary bypass(CPB) onset;after CPB; the first day after operation and the second day after operation. Plasma lactate levels in arterial and jugular venous blood were also quantified at the same five time points. Antisaccadic eye movement(ASEM) test and Mini-Mental State Examination(MMSE) were tested on the day before operation and the seventh day postoperatively. Results: Serum MMP-9 and GFAP concentration increased after CPB and decreased to basal levels on the second morning after surgery in both groups. MMP-9 concentration in group D-I were lower on times of CPB off and the first day after operation. However lower GFAP concentration in group D-I were found on times of 5 min after CPB onset and CPB off. No significant differences were found between the two groups when the difference of arterial and jugular bulb venous blood lactate levels were compared except 5 minutes after CPB on. The MMSE score of total patients was declined significantly from the baseline values of 26.9±1.4 to 25.4±1.5 on the seventh day after operation(p< 0.001). The ASEM scores also decreased significantly from the baseline values of 16.4±3.8 to 13.7±6.8 postoperatively (p< 0.001). No difference were found in postoperative MMSE (p=0.787)and ASEM impairment (p=0.439) between the treatment groups. Conclusion: Dexmedetomidine combined with isoflurane can decrease the biochemical markers of brain injury but does not improve cognitive function after cardiac surgery compared with isoflurane alone.

Abstract PR283

Background & Objectives: The objective of this study was to evaluate the effect of hypothermic cardiopulmonary bypass (CPB) on cerebral oxygen saturation (rSO2), internal jugular bulb venous oxygen saturation (SjvO2), mixed venous oxygen saturation (SvO2), and bispectral index (BIS) used to monitor cerebral oxygen balance in pediatric patients. Materials & Methods: Sixty American Society of Anesthesiologists Class II-III patients aged 1 to 4 years old with congenital heart disease scheduled for elective cardiac surgery were included in this study. Temperature, BIS, rSO2, mean arterial pressure, central venous pressure, cerebral perfusion pressure (CPP), and hematocrit were recorded. Internal jugular bulb venous oxygen saturation and SvO2 were obtained from blood gas analysis at the time points: after induction of anesthesia (T0), beginning of CPB (T1), ascending aortic occlusion (T2), 20 minutes after initiating CPB (T3), coronary reperfusion (T4), separation from CPB (T5), and at the end of operation (T6). The effect of hypothermia or changes in CPP on rSO2, SjvO2, SvO2, and BIS were analyzed. Results: Compared with postinduction baseline values, rSO2 significantly decreased at all-time points: onset of extracorporeal circulation, ascending aortic occlusion, 20 minutes after CPB initiation, coronary reperfusion, and separation from CPB (P<0.05). Compared with measurements made following induction of anesthesia, SjvO2 significantly increased with initiation of CPB, ascending aortic occlusion, 20 minutes after initiating CPB, coronary reperfusion, and separation from CPB (P<0.05). Compared with induction of anesthesia, BIS significantly decreased with the onset of CPB, aortic cross clamping, 20 minutes after initiating CPB, and coronary reperfusion (P<0.05). Bispectral index increased following separation from CPB. There was no significant change in SvO2 during cardiopulmonary bypass (P > 0.05). Correlation analysis demonstrated that rSO2 was positively related to CPP (r =0.687, P=0.000), with a low linear correlation to temperature (r=0.453, P=0.000). Internal jugular bulb venous oxygen saturation was negatively related to temperature (r=-0.689, P=0.000). Bispectral index was positively related to both temperature (r=0.824, P=0.000) and CPP (r=0.782, P=0.000). Cerebral oxygen saturation had a positive linear correlation with CPP and a low linear correlation to temperature. Internal jugular bulb venous oxygen saturation had a negative linear correlation to temperature. Conclusion: Pre-and and early postbypass periods are vulnerable times for adequate cerebral oxygenation. Anesthetic management must aim to optimize the supply and demand relationship Disclosure of Interest: None declared

Transient dilutional acidosis but no lactic acidosis upon cardiopulmonary bypass in patients undergoing coronary artery bypass grafting.

IntroductionDilutional acidosis may result from the introduction of a large fluid volume into the patients’ systemic circulation, resulting in a considerable dilution of endogenous bicarbonate in the presence of a constant carbon dioxide partial pressure. Its significance or even existence, however, has been strongly questioned. Blood gas samples of patients operated on with standard cardiopulmonary bypass (CPB) were analyzed in order to provide further evidence for the existence of dilutional acidosis.Material and methodsBetween 07/2014 and 10/2014, a total of 25 consecutive patients scheduled for elective isolated coronary artery bypass grafting with CPB were enrolled in this prospective observational study. Blood gas samples taken regularly after CPB initiation were analyzed for dilutional effects and acid-base changes.ResultsAfter CPB initiation, hemoglobin concentration dropped from an average initial value of 12.8 g/dl to 8.8 g/dl. Before the beginning of CPB, the mean value of the patients’ pH and base excess (BE) value averaged 7.41 and 0.5 mEq/l, respectively. After the onset of CPB, pH and BE values significantly dropped to a mean value of 7.33 (p < 0.0001) and –3.3 mEq/l (p < 0.0001), respectively, within the first 20 min. In the following period during CPB they recovered to 7.38 and –0.5 mEq/l, respectively, on average. Patients did not show overt lactic acidosis.ConclusionsThe present data underline the general existence of dilutional acidosis, albeit very limited in its duration. In patients undergoing coronary artery bypass grafting it seems to be the only obvious disturbance in acid-base homeostasis during CPB.

Impaired microcirculatory perfusion in a rat model of cardiopulmonary bypass: the role of hemodilution.

Although hemodilution is attributed as the main cause of microcirculatory impairment during cardiopulmonary bypass (CPB), this relationship has never been investigated. We investigated the distinct effects of hemodilution with or without CPB on microvascular perfusion and subsequent renal tissue injury in a rat model. Male Wistar rats (375-425 g) were anesthetized, prepared for cremaster muscle intravital microscopy, and subjected to CPB (n = 9), hemodilution alone (n = 9), or a sham procedure (n = 6). Microcirculatory recordings were performed at multiple time points and analyzed for perfusion characteristics. Kidney and lung tissue were investigated for mRNA expression for genes regulating inflammation and endothelial adhesion molecule expression. Renal injury was assessed with immunohistochemistry. Hematocrit levels dropped to 0.24 ± 0.03 l/l and 0.22 ± 0.02 l/l after onset of hemodilution with or without CPB. Microcirculatory perfusion remained unaltered in sham rats. Hemodilution alone induced a 13% decrease in perfused capillaries, after which recovery was observed. Onset of CPB reduced the perfused capillaries by 40% (9.2 ± 0.9 to 5.5 ± 1.5 perfused capillaries per microscope field; P < 0.001), and this reduction persisted throughout the experiment. Endothelial and inflammatory activation and renal histological injury were increased after CPB compared with hemodilution or sham procedure. Hemodilution leads to minor and transient disturbances in microcirculatory perfusion, which cannot fully explain impaired microcirculation following cardiopulmonary bypass. CPB led to increased renal injury and endothelial adhesion molecule expression in the kidney and lung compared with hemodilution. Our findings suggest that microcirculatory impairment during CPB may play a role in the development of kidney injury.