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

Abstract

Objective: 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. Design: Prospective, randomized blinded study. Setting: Tertiary university hospital. Participants: A total of 26 adults undergoing elective coronary artery bypass graft surgery with CPB. Interventions: PC (n = 13) versus HC circuits (n = 13). Measurements and Main Results: 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 mm; 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/mm 2 , p = 0.006; HC: 16 § 2 to 11 § 2 mm/mm 2 , p = 0.003) and remained equally altered in the first 3 postoperative days. Conclusion: 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.

Severe Impairment of Microcirculatory Perfused Vessel Density Is Associated With Postoperative Lactate and Acute Organ Injury After Cardiac Surgery

“…3,19 A number of potential causes have been suggested for the early loss of microcirculatory coherence with systemic hemodynamics, which include blood exposure to extracorporeal cardiopulmonary bypass circuitry, postoperative systemic inflammatory response syndrome (SIRS), ischemic-reperfusion injury, endothelial injury, impaired red blood cell rheology, or patient-specific hemodynamic endpoints that were outside generally accepted targets. 5,[20][21][22][23] The most notable changes in patients' postoperative microcirculation were an increased heterogeneity, also referred to as a type 1 phenotype of microcirculatory dysfunction. 12 A type 1 loss represents microcirculatory dysfunction that is heterogeneous and can cause regional tissue hypoxia due to various cellular insults, including endothelial dysfunction, hemorheological changes, or abnormal vasomotor tone due to pathologic nitric oxide release or oxidative stress.…”

The Endothelial Glycocalyx: Physiology and Pathology in Neonates, Infants and Children

“…However, the time course of PBR changes described in adults differs from that in infants. While PBR values were shown to further increase during the first three postoperative days in adults following surgery on cardiopulmonary bypass (Dekker et al, 2019(Dekker et al, , 2020, in infants PBR values were already decreasing 24 h after surgery (Nussbaum et al, 2015). As the studies vary largely with respect to the underlying cardiac disease (congenital heart defect vs. coronary artery disease), surgical procedures applied and presence of cardiac risk factors, it is impossible to draw a conclusion from these studies regarding possible agedependent differences in shedding and recovery of the glycocalyx.…”

“…In healthy mature newborns (mean age 3 days) the PBR was 2.14 ± 0.25 μm ( Puchwein-Schwepcke et al, 2021 ) versus a PBR of 1.88 ± 0.2 μm measured in healthy adults (mean age 20.7 years) ( Astapenko et al, 2019 ). Likewise, infants with cardiac defects (mean age 8.9 month) had a higher baseline PBR than adult cardiac patients (median age 64–69 years) before undergoing surgery on cardiopulmonary bypass (2.5 μm [2.44–2.7 IQR] vs. 2.0 ± 0.2 μm, respectively) ( Nussbaum et al, 2015 ; Dekker et al, 2019 ; Dekker et al, 2020 ). At present it remains unclear whether these differences in PBR magnitude are due to methodological differences (e.g., measurements obtained sublingually versus the fossa auricularis of the ear conch) or truly reflect an age-dependence in PBR values.…”

A review on the physiological and pathophysiological role of endothelial glycocalyx

“…Therefore, in the updated Starling's Rule, the primary determinant of transcapillary filtration is subglycocalyx (and not interstitial oncotic pressure). [ 9–11 ]…”