Cardiopulmonary Bypass Hematocrit Research Articles

Hematocrit and Renal Failure in Aortic Arch Surgery: A Society of Thoracic Surgeons Database Study

BackgroundThis study examined the association between cardiopulmonary bypass (CPB) hematocrit and postoperative acute renal failure (ARF) in patients undergoing aortic arch surgery with hypothermic circulatory arrest. MethodsThe Society of Thoracic Surgeons Adult Cardiac Surgery Database was queried from 2011 to 2019 for patients undergoing aortic arch surgery with hypothermic circulatory arrest. A multivariable logistic regression model estimated the adjusted odds of postoperative ARF on the basis of CPB hematocrit. Effects were stratified by preoperative kidney function and the duration of hypothermic circulatory arrest by using interaction terms. The study also investigated the association between postoperative ARF and major postoperative outcomes by using multivariable regression models. ResultsOn adjusted analysis, higher CPB hematocrit (>20%-25%, >25%-30%, >30%) was associated with lower odds of ARF as compared with lower CPB hematocrit (≤20%) (>20-25%, aOR, 0.78; 95% CI, 0.65-0.93; P = .006; >25%-30%, aOR, 0.65; 95% CI, 0.50-0.84; P = .0007; >30%, aOR, 0.45; 95% CI, 0.28-0.72; P = .0008). The predicted probability of postoperative ARF by CPB hematocrit was higher in patients with lower preoperative renal function (estimated glomerular filtration rate, <60 mL/min/1.73 m2) (interaction P = .03). The association between hematocrit and postoperative ARF was not significantly modified by hypothermic circulatory arrest time (interaction P = .74). All postoperative outcomes were significantly worse in patients with postoperative ARF (all P < .0001). ConclusionsAmong patients undergoing aortic arch surgery, a higher CPB hematocrit level is associated with reduced likelihood of postoperative ARF. Preoperative renal function, but not hypothermic circulatory arrest duration, significantly modified this association. The maintenance of higher CPB hematocrit may reduce the incidence of postoperative ARF, especially for patients with poor preoperative renal function.

The effect of various blood management strategies on intraoperative red blood cell transfusion in first-time coronary artery bypass graft patients.

Effective blood management during cardiac surgery requires a multifactorial effort to limit exposure to allogeneic blood products. The present study evaluated the distribution of intraoperative interventions in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass. Records from patients undergoing non-reoperative surgery at 120 hospitals between January 2017 and December 2017 were reviewed, and red blood cell transfusion quartiles established. The 31 hospitals with the lowest transfusion rates fell into the first quartile (low transfusion group, n = 3,186 patients), while 29 hospitals with the highest transfusion were in the fourth quartile (high transfusion group, n = 2,561). A survey was sent to assess the blood management techniques: acute normovolemic hemodilution, autologous prime, fluid management, intraoperative autotransfusion, ultrafiltration, and transfusion triggers. All data are presented as mean (standard deviation). Patients in the low transfusion group had red blood cell transfusion rate of 5.5%, while the high transfusion group was 28.3%. There was no difference in gender or age. Fluid management was reduced in the low transfusion group with smaller prime volumes and anesthesia volumes, but higher crystalloid use during cardiopulmonary bypass. The low transfusion group did not use acute normovolemic hemodilution as often and had lower sequestered volumes when used. When ultrafiltration was used, the low transfusion quartile group removed more volume (1,555.9 ± 955.2 vs. 1,326.1 ± 918.9 mL, p ⩽ 0.001). In the low transfusion group, nadir hematocrit on-cardiopulmonary bypass averaged 1.6% lower and 3.0% lower for transfusion post-cardiopulmonary bypass. Intraoperative red blood cell units averaged 0.11 ± 0.50 U in low transfusion group compared to 0.63 ± 1.14 U in the high transfusion group. Mixed-effects logistic regression identified first in operating room and first on cardiopulmonary bypass hematocrit, estimated blood volume and nadir hematocrit transfusion trigger as the strongest predictors for red blood cell transfusion. Significant variation exists in the transfusion of red blood cell in coronary artery bypass graft patients undergoing cardiopulmonary bypass which may be related to the application of intraoperative blood management techniques.

How detrimental is reexploration for bleeding after cardiac surgery?

ObjectiveTo establish the risk factors and impact of reexploration for bleeding in a large modern cardiac surgical cohort. MethodsAt a tertiary referral center, baseline, index procedural, reexploration, outcome, and readmission characteristics of 16,793 consecutive adult cardiac surgery patients were prospectively entered into dedicated clinical databases. Correlates of reexploration for bleeding, as well as its association with outcomes and readmission, were examined with multivariable regression models. ResultsThe mean patient age was 65.9 ± 12.1 years, and 11,991 patients (71.4%) patients were male. Perioperative mortality was 2.8% (458 of 16,132) in those who did not undergo reexploration for bleeding and 12.0% (81 of 661) in those who underwent reexploration for bleeding, corresponding to an odds ratio of 3.4 ± 0.5 (P <.001) over other predictors of mortality, including Euroscore II. Mortality was highest in patients who underwent reexploration after the day of index surgery (odds ratio, 6.4 ± 1.1). Hospital stay was longer in patients who underwent reexploration for bleeding (median, 12 days, vs 7 days in patients who did not undergo reexploration; P <.001), to an extent beyond any other correlate. Reexploration for bleeding also was independently associated with new-onset postoperative atrial fibrillation, renal insufficiency, intensive care unit readmission, and wound infection. Risk factors for reexploration for bleeding were tricuspid valve repair, on-pump versus off-pump coronary artery bypass grafting, emergency status, cardiopulmonary bypass (CPB) duration, low body surface area, and lowest CPB hematocrit of <24%. ConclusionsReexploration for bleeding is a lethal and morbid complication of cardiac surgery, with a detrimental effect that surpasses that of any other known potentially modifiable risk factor. All efforts should be made to minimize the incidence and burden of reexploration for bleeding, including further research on transfusion management during CPB.

The effectiveness of acute normolvolemic hemodilution and autologous prime on intraoperative blood management during cardiac surgery.

Intraoperative blood management during cardiac surgery is a multifaceted process incorporating various interventions directed at optimizing oxygen delivery and enhancing hemostasis. The purpose of this study was to evaluate the effects of acute normovolemic hemodilution (ANH) and autologous priming (AP) on preserving the hematocrit during cardiopulmonary bypass (CPB). Case records from a national registry of adult patients who underwent cardiac surgery between January and October 2016 were reviewed. Groups were determined as follows: ANH, AP, ANH+AP or Neither. Primary endpoint was first the hematocrit on CPB with secondary endpoints of hematocrit drift and red blood cell (RBC) transfusion rate. Eighteen thousand and twenty-four (18,024) consecutive patients were reviewed. The first CPB hematocrit was lowest in the ANH group (26.5%±4.4%) and highest in ANH+AP patients (27.5%±4.8%) (p<0.001). The change in hematocrit was greatest in the ANH group (8.3%±3.9%) compared to both the AP (6.4%±3.8%) and ANH+AP (6.9%±4.1%) groups (p<0.001). Intraoperative RBC transfusions were as follows: ANH 26 (7.8%), AP 2,531 (20.0%), ANH+AP 287 (10.3%) and Neither 592 (26.7%) (p<0.001). Regression results show that the use of ANH will result in the greatest decline in hematocrit values. When combined with AP, higher hematocrits and lower transfusions were seen.

The Risk of Acute Kidney Injury With Co-Occurrence of Anemia and Hypotension During Cardiopulmonary Bypass Relative to Anemia Alone

Postoperative acute kidney injury (AKI) is a common serious consequence of cardiac surgery. One recent study found higher AKI rates when anemia and hypotension occurred during cardiopulmonary bypass (CPB) relative to anemia alone. To revalidate this post hoc observation we analyzed detailed data from a large cardiac surgery cohort. Patient, procedural, and outcome data were collected for nonemergent aortocoronary bypass and valve surgeries between July 2001 and September 2012. The occurrence of AKI (as defined by the Acute Kidney Injury Network criteria) was analyzed relative to known renal risk factors, and CPB hematocrit and blood pressure determinations in univariate and multivariable linear regression analyses. In our 3,963-patient cohort, we did not observe different AKI rates with the co-occurrence of anemia and hypotension relative to anemia alone (41.6% versus 44.3%; p = 0.39). Secondary analyses using linear definitions for AKI, CPB anemia, and hypotensive burden, and assessing for coincident timing also did not demonstrate significant association of anemia and hypotension with AKI risk relative to anemia alone. In a large cohort of cardiac surgery patients, we did not confirm any association of cardiac surgery-related AKI risk with the co-occurrence of hypotension and anemia during CPB relative to anemia alone. More detailed analyses also failed to support an anemia-hypotension interaction. Additional studies are required to better understand the relationship among anemia, hypotension during CPB, and postoperative AKI, but existing evidence is insufficient to support changes in clinical practice.

Influence of Intraoperative Fluid Volume on Cardiopulmonary Bypass Hematocrit and Blood Transfusions in Coronary Artery Bypass Surgery

A hematocrit (Hct) of less than 25% during cardiopulmonary bypass (CPB) and transfusion of homologous packed red blood cells (PRBC) are each associated with an increased probability of adverse events in cardiac surgery. Although the CPB circuit is a major contributor to hemodilution intravenous (IV) fluid volume may also significantly influence the level of hemodilution. The objective of this study was to explore the influence of asanguinous IV fluid volume on CPB Hct and intraoperative PRBC transfusion. After Institutional Review Board approval, a retrospective chart review of 90 adult patients that had undergone an elective, isolated CABG with CPB was conducted. Regression analysis was used to determine if pre-CPB fluid volume was associated with the lowest CPB Hct and the incidence of an intraoperative PRBC transfusion. In separate multivariate analyses, higher pre-CPB fluid volume was associated with lower minimum CPB Hct (p&lt; .0001), and higher minimum CPB Hct was associated with a decreased probability of PRBC transfusion (p&lt; .0001). Compared to patients that received &lt;1600 mL (n= 55) of pre-CPB fluid, those that received &gt;1600 mL (n= 35) had a decreased mean low CPB Hct (22.4% vs 25.6%,p&lt; .0001), an increased incidence of a CPB Hct &lt;25% (74% vs. 38%,p= .0008) and PRBC transfusion (60% vs. 16%,p&lt; .0001), and increased median PRBC units transfused (2.0 vs 1.0,p= .1446) despite no significant difference in gender, age, patient size, baseline Hct, or CPB prime volume. Patients that received a PRBC transfusion (n= 30) received a significantly higher volume of pre-CPB fluid than nontransfused patients (1800 vs. 1350 mL,p= .0039). These findings suggest that pre-CPB fluid volume can significantly contribute to hemodilutional anemia in cardiac surgery. Optimizing pre-CPB volume may preserve baseline Hct and help limit intraoperative hemodilution.

Factors That Influence the Ability to Perform Autologous Priming

The purpose of this study was to determine which factors impact the ability to perform autologous priming (AP) of the extracorporeal circuit. Second, the effects of differential AP on transfusion and volume requirements were evaluated. After institutional review board approval, demographic, operative, volumetric, and transfusion data were prospectively collected on 100 adult patients undergoing cardiopulmonary bypass (CPB). Two analyses were conducted: AP Taken and percent AP Given. For each analysis, three groups were created based on standard distribution. Group A included patients within less than mean – 1 SD (≤500 mL AP Taken or ≥90% AP Given back), group B included patients within mean ± 1 SD (501–1299 mL AP Taken or 11%–89% AP Given back), and group C included patients greater than mean + 1 SD (≥1300 mL AP Taken or ≤10% AP Given back). Weight, pre-CPB hematocrit, clinical severity, and pre-CPB volume balance did not differ between the groups. Significant differences existed in AP Taken and percent AP Given between individual perfusionists. More AP was given back with higher urine output (group A: 846 ± 700 mL, group B: 613 ± 414 mL, group C: 384 ± 272 mL;p= .004), more autotransfusion [group A: 0 (0,1300 mL), group B: 0 (0,500 mL), group C: 0 (0,250 mL);p= .008], and less AP Taken [group A: 800 (0,1300 mL), group B: 1000 (200,1600 mL), group C: 1000 (800,1600 mL);p= .001]. When more AP was taken, CPB hematocrit was higher (group A: 22.3% ± 4.8%, group B: 25.6% ± 4.7%, group C: 26.6% ± 4.3%;p= .032), and fewer patients received red blood cells (group A: 64.3%, group B: 28.3%, group C:14.3%;p= .017). Some perfusionists were able to remove more AP before CPB. When more AP was taken, CPB hematocrit was higher, fewer patients received a transfusion, and less AP was given back. More AP was also given back with higher urine output and higher blood loss to the autotransfusion device.

Prediction of massive blood transfusion in cardiac surgery

In cardiac surgery with cardiopulmonary bypass (CPB), excessive blood loss requiring the transfusion of multiple red blood cell (RBC) units is a common complication that is associated with significant morbidity and mortality. The objective of this study was to develop a prediction rule for massive blood transfusion (MBT) that could be used to optimize the management of, and research on, at-risk patients. Data were collected prospectively over the period from 2000 to 2005, on patients who underwent surgery with CPB at one hospital. Patients who received > or = five units of RBC within one day of surgery were classified as MBT. Logistic regression was used to appropriately select and weigh perioperative variables in the prediction rule, which was developed on the initial 60% of the sample and validated on the remaining 40%. Of the 10,667 patients included, 925 (8.7%) had MBT. The clinical prediction rule included 12 variables (listed in order of predictive value: CPB duration, preoperative hemoglobin concentration, body surface area, nadir CPB hematocrit, previous sternotomy, preoperative shock, preoperative platelet count, urgency of surgery, age, surgeon, deep hypothermic circulatory arrest, and type of procedure) and was highly discriminative (c-index = 0.88). In the validation set, those classified as low-, moderate-, and high-risk by a simple risk score derived from the prediction rule had a 5%, 27%, and 58% chance of MBT, respectively. A clinical prediction rule was developed that accurately identified patients at low-risk or high-risk for MBT. Studies are needed to determine the external generalizability and clinical utility of the prediction rule.

Echocardiographic comparison of the standard end-hole cannula, the soft-flow cannula, and the dispersion cannula during perfusion into the aortic arch

Background Dislodgement of aortic arch atheroma caused by a perfusion “jet” from the aortic cannula may be a major cause of atheroemboli during coronary artery surgery when using cardiopulmonary bypass (CPB). Two very different cannulas, the Soft-Flow aortic cannula and the Dispersion cannula, which have been designed to reduce exit velocity (cm/s) during perfusion, are compared with a standard steel tip cannula and to each other. Methods To demonstrate any significant differences transesophageal echocardiography (TEE) was used to measure exit velocity of each cannula at a distance of 1, 2, and 3 cm from the tip and compare flow morphology within the aortic arch. Nine patients in whom the cannula tip could be identified and colored Doppler imaging could demonstrate representative morphology were randomly assigned into one of three groups of 3 patients each: group I, a standard steel-tip end-hole cannula (7.3 mm); group II, the Soft-Flow cannula (8.0 mm); and group III, the Dispersion cannula (8.0 mm). Results The standard steel tip cannula demonstrated a long narrow perfusion jet. The Soft-Flow cannula morphology was made up of multiple smaller exiting jets. The Dispersion cannula demonstrated a broad wedge-shaped perfusion pattern. Perfusion hemodynamics (cardiopulmonary bypass hematocrit in d/L, cardiopulmonary bypass blood flow in L/m, mean arterial pressure during cardiopulmonary bypass mm Hg, and perfusion line pressure in mm Hg) were not significantly different between each group. The mean velocities between group I (318 ± 63 cm/s at 1 cm, 296 ± 60 cm/s at 2 cm, 271 ± 85 cm/s at 3 cm) and group II (351 ± 31 cm/s at 1 cm, 240 ± 103 cm/s at 2 cm, 171 ± 120 cm/s at 3 cm) were not statistically different. Group III (the Dispersion cannula) demonstrated significantly reduced velocities (174 ± 22 cm/s at 1 cm, 138 ± 23 cm/s at 2 cm, 90 ± 36 cm/s at 3 cm) when compared with the other two groups ( p < 0.05, analysis of variance). Conclusions The Dispersion cannula is significantly different with a lower perfusion velocity and the elimination of the exiting jet or jets. This cannula warrants further clinical study as it may reduce atheroemboli during cardiopulmonary bypass.

LOW HEMATOCRIT BUT NOT PERFUSION PRESSURE DURING CPB IS PREDICTIVE FOR RENAL FAILURE FOLLOWING CABG SURGERY

Introduction. Acute renal failure (ARF) requiring dialysis occurs in 1% to 5% of patients following cardiac surgery, and remains a cause of major morbidity and mortality. While some preoperative risk factors have been characterized [1], the influence of intraoperative factors on the occurrence of ARF following cardiac surgery is less well understood. We examined the hypothesis that low hematocrit and low perfusion pressure during cardiopulmonary bypass (CPB) influence the development of ARF following coronary artery bypass graft (CABG) surgery. Methods. With IRB approval, perioperative data for 1404 first time CABG surgical patients from February 1st 1995 to February 1st 1997 was gathered from the Duke Heart Center and Anesthesia Databases including: age, sex, race, weight, history of stroke, peripheral vascular disease (PVD), congestive heart failure (CHF), diabetes (DM), obstructive lung disease (COPD), carotid bruit (PreCarBr), serum creatinine (PreCr), ejection fraction (PreEF), CPB duration, number of grafts, lowest CPB hematocrit (MinHct), lowest inflow (LowinflT) and nasopharyngeal (LowNpT) temperatures, and requirement for intraaortic balloon pump post CPB (IABP). Radial mean arterial pressure (MAP) was recorded automatically every minute using the Arkive Information Management System, and the time-pressure integral representing total MAP area <50mmHg during CPB (TM<50) was calculated. Postoperative ARF was identified as moderate (a rise of >or=to1.0mg/dl Cr) or severe (requiring dialysis). Association of variables with ARF was assessed by univariate and multivariate analysis, p<.05 was considered significant. Results. 95 of the 1404 CABG patients developed ARF (moderate-89, severe-6). MinHct was significantly lower, assessed by multivariate analysis, in the ARF group (18.8 +/- 3.6 vs 19.4 +/- 3.8%), while TM<50 was similar in both groups (ARF: 162 +/- 195 vs nonARF: 141 +/- 166 mmHg.min). Association of other variables is presented in Table 1.Table 1Discussion. We found the lowest hematocrit during CPB to be an independent predictor of ARF following CABG surgery, whereas an index of low perfusion pressure during CPB (TM<50) was not associated with post CABG ARF. Several previously reported perioperative risk factors [1] were also associated with ARF in our study. These data question the wisdom of tolerating severe anemia during CPB for CABG surgery.