Haemodilutional Effect of Standard Fluid Management Limits the Effectiveness of Acute Normovolaemic Haemodilution in AAA Surgery—Results of a Pilot Trial

Decreased Transfusion Requirements with Use of Acute Normovolemic Hemodilution in Open Aortic Aneurysm Repair

OBJECTIVES

Acute normovolemic hemodilution (ANH) is an operative blood conservation technique involving the removal and storage of patient blood after induction of anesthesia, while maintaining normovolemia with crystalloid and/or colloid replacement. Developed and used predominately in cardiac surgery, ANH has been applied to the vascular surgery population but data regarding impact on transfusion requirements in this population is limited. The objective of this study is to compare transfusion requirements and coagulopathy in patients undergoing open abdominal aortic aneurysm repair (oAAA) employing ANH to those receiving only product replacement as clinically indicated.

METHODS

This is a retrospective review of patients undergoing elective oAAA at a quaternary aortic referral center from 2017-2019. Those eligible for ANH, no active cardiac ischemia, no valvular disease, normal LV/RV function, CKD < stage 3, HCT > 38%, normal coagulation profile, were included in the study. Patient demographics and characteristics were collected as were operative variables including extent of aneurysm, clamp site, visceral/renal ischemia time, operative time, and transfusion requirements. Post-operative morbidity, mortality, and length of stay were analyzed. Patients with and without ANH were matched and compared. Continuous measures were analyzed with Wilcoxon rank sum tests and t-tests.

RESULTS

Over the study period, 209 oAAA were performed, 76 patients met inclusion criteria; 27 patients underwent ANH while 49 did not. Patients with ANH had less PRBC transfusion intraoperative (Median [25^th,75^th]: 0 [0,1] vs. 1[0,2] units, p=0.02), at 24 hours(0[0,1] vs. 1[0,2] units, p=0.008), at 48 hours (0[0,1] vs. 1[0,2], p=0.007) and throughout the admission (0[0,1] vs. 2[0,2], p=0.011). There was no difference in intraoperative platelet or cryoprecipitate transfusions. At 48-hours, ANH had significantly higher platelet counts (142 ±35.8 vs. 124±37.6 x10(3)/mcL, p=0.044), lower PTT, and lower INR. There was no difference in MI, RTOR, or mortality (1 death overall). ANH patients had shorter LOS (7.0±2.7 vs 8.8±4.8 days, p=0.041).

CONCLUSIONS

ANH during oAAA results in less intraoperative and post-operative PRBC with improved coagulation parameters and a shorter hospital LOS.

Practice guidelines for perioperative blood management: an updated report by the American Society of Anesthesiologists Task Force on Perioperative Blood Management*

The American Society of Anesthesiologists Committee on Standards and Practice Parameters and the Task Force on Perioperative Blood Management presents an updated report of the Practice Guidelines for Perioperative Blood Management.

Supplemental Digital Content is available in the text.

Transfusion triggers for guiding RBC transfusion for cardiovascular surgery: a systematic review and meta-analysis*

OBJECTIVE

Restrictive red cell transfusion is recommended to minimize risk associated with exposure to allogeneic blood. However, perioperative anemia is an independent risk factor for adverse outcomes after cardiovascular surgery. The purpose of this systematic review and meta-analysis is to determine whether perioperative restrictive transfusion thresholds are associated with inferior clinical outcomes in randomized trials of cardiovascular surgery patients.

DATA SOURCES

The Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE from inception to October 2013; reference lists of published guidelines, reviews, and associated articles, as well as conference proceedings. No language restrictions were applied.

STUDY SELECTION

We included controlled trials in which adult patients undergoing cardiac or vascular surgery were randomized to different transfusion thresholds, described as a hemoglobin or hematocrit level below which RBCs were transfused.

DATA EXTRACTION

Two authors independently extracted data from included trials. We pooled risk ratios of dichotomous outcomes and mean differences of continuous outcomes across trials using random-effects models.

DATA SYNTHESIS

Seven studies (enrolling 1,262 participants) met inclusion criteria with restrictive and liberal transfusion thresholds most commonly differing by a hemoglobin of 1 g/dL or hematocrit of 6-7%, resulting in decreased transfusions by 0.71 units of RBCs (95% CI, 0.31-1.09, p = 0.0002) without an associated change in adverse events: mortality (risk ratio, 1.12; 95% CI, 0.65-1.95; p = 0.60), myocardial infarction (risk ratio, 0.94; 95% CI, 0.30-2.99; p = 0.92), stroke (risk ratio, 1.15; 95% CI, 0.57-2.32; p = 0.70), acute renal failure (risk ratio, 0.98; 95% CI, 0.64-1.49; p = 0.91), infections (risk ratio, 1.23; 95% CI, 0.85-1.78; p = 0.27), or length of stay. There was no between-trial heterogeneity for any pooled analysis. Including four pediatric trials (456 participants) and 10 trials utilizing only intraoperative acute normovolemic hemodilution (872 participants) did not substantially change the results except that unlike the transfusion threshold trials, the hemodilution trials did not reduce the proportion of patients transfused (interaction p = 0.01).

CONCLUSIONS

Further randomized controlled trials are necessary to determine the optimal transfusion strategy for patients undergoing cardiovascular surgery.

Anesthesia for Open Abdominal Aortic Aneurysm Repair

Abdominal aortic aneurysms (AAAs) are the 13th leading cause of death in the United States 1 and approximately 40,000 patients undergo elective AAA repair each year.2 With the population aging, this number is expected to increase. Although the use of endovascular AAA repair is becoming more common, open repair, first reported by Dubost et al. in 1951 remains the gold standard.2 This chapter will review the etiology, risk factors, diagnosis, pathophysiology, operative technique, perioperative management, and postoperative complications of patients undergoing open AAA repair.

Intravenous fluids for abdominal aortic surgery

BACKGROUND

Surgery on the abdominal aorta to treat aneurysms or occlusive disease is a major undertaking which requires intensive physiological support and fluid management. Blood products are often used but the main fluid replacement is with crystalloids or colloids. For years there has been controversy over which fluid is optimal and a number of studies have examined the subject. This is an update of a Cochrane review first published in 2000 and previously updated in 2002.

OBJECTIVES

To determine the effectiveness of different non-blood replacement fluids used in abdominal aorta procedures with a view to identifying the optimal fluid for use.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (August 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 3) for publications describing randomised controlled trials of non-blood replacement fluids in abdominal aortic surgery. In addition, the reference lists from retrieved trials were screened for further information about trials.

SELECTION CRITERIA

Randomised controlled trials assessing the effects of at least one specific non-blood fluid used for replacement therapy in operations on, and confined to, the abdominal aorta.

DATA COLLECTION AND ANALYSIS

Data were extracted and then entered into the Review Manager software where statistical analyses were performed.

MAIN RESULTS

Thirty-eight trials involving 1589 patients were included. Patients undergoing aortic surgery had various physiological parameters measured before and after their operation (these were cardiac, respiratory, haematological, and biochemical). Patients were randomised to a fluid type. This review demonstrated that no single fluid affects any outcome measure significantly more than another fluid across a range of outcomes. The death rate in these studies was 2.45% (39 patients).

AUTHORS' CONCLUSIONS

Despite the confirmed beneficial effects of colloids in this review, further studies are still required. There are no studies examining the effects of combination fluid therapy. The primary research outcome was death, for which results were limited; therefore, future studies should pay more attention to short-term outcomes such as minimising the need for allogenic blood transfusion, complications (organ failure), and length of stay in both the intensive care unit and hospital.

The Effect of Acute Normovolaemic Haemodilution on the Inflammatory Response and Clinical Outcome in Abdominal Aortic Aneurysm Repair—Results of a Pilot Trial

OBJECTIVES

To determine the effect of acute normovolaemic haemodilution (ANH) on the inflammatory response and clinical outcome in elective open abdominal aortic aneurysm (AAA) repair.

DESIGN

Randomised controlled clinical trial.

METHODS

Thirty-six patients were randomised to undergo ANH or act as controls. Cell salvage was permitted in both groups. Heterologous blood was transfused according to pre-determined triggers. Outcome measures were markers of the systemic inflammatory response in serum and urine observed at multiple time points, and clinical recovery.

RESULTS

Median 890 (range 670-1620) ml of blood was removed at ANH in 16 patients. There were no differences in peri-operative changes in neutrophil count ( P = 0.13), serum C-reactive protein ( P = 0.38), interleukin-6 ( P = 0.50), total antioxidant capacity ( P = 0.73), urinary secretion of albumin ( P = 0.97) or retinol binding protein ( P = 0.41). There were no differences in the mortality and morbidity rates, systemic inflammatory response syndrome, ITU or hospital stay.

CONCLUSIONS

ANH, when used in combination with cell salvage, made no impact on systemic inflammatory response and clinical outcome when compared to cell salvage alone after AAA repair. ANH cannot be recommended for routine use in patients undergoing abdominal aortic aneurysm surgery when cell salvage is available.