Platelet-rich plasma (PRP) is autologous serum containing not only high concentrations of platelets, but also abundant growth factors and cytokines, such as transforming growth factor-β (TGF-β), epidermal and vascular endothelial growth factors (EGF and VEGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), and insulin-like growth factor-1 (IGF-1). PRP is widely used, with applications ranging from orthopedic procedures and sports injuries to urology surgery and cardiac surgery.[6]
Most recent studies demonstrated that PRP application in AAD surgery is an effective way for blood conservation in the perioperative period. In whole blood exposed to the CPB circuit, the platelets are activated, and coagulation factors are consumed during CPB. The use of PRP can maintain normal platelet function, preserve plasma volume, and ultimately reduce the transfusion volume.[11] But whether it can decrease postoperative complications and improve short-term outcomes is under debate. Some studies showed that PRP can decrease the length of ICU stay[7, 8], decrease the mean number of ventilator days[7–9] and the incidence of tracheostomy[7, 9], and decrease the length of hospital stay[8, 10], while another study showed that PRP application might increase the risk of postoperative acute kidney injury, without decreasing the length of hospital stay or in-hospital mortality.[11]
Consistent with the abovementioned studies, we found that the incidence of perioperative cryoprecipitate transfusion was reduced in the PRP group compared to the non-PRP group. Unexpectedly, we observed no significant differences in other blood product transfusions between the two groups, including packed red blood cells and fresh frozen plasma. The differences from previous studies may result from different blood transfusion standards and programs in the different centers. Additionally, we made the following observations.
1) Increased serum albumin and total protein levels in the first postoperative examination
Serum albumin levels are decreased after cardiac surgery due to surgical injury, blood loss, systematic inflammation, hypermetabolism, and so on[12, 13]. Serum albumin levels serve as a marker of the host response to a severe operative insult.[14] In patients with low serum albumin levels, complication and mortality rates after CABG or other cardiac surgeries are high.[12, 15, 16] As for patients with AAD, a recent study showed that albumin levels are associated with a high risk of in-hospital mortality.[13]
In PRP which is re-transfused to the body, the albumin concentration is nearly the same as in blood and therefore PRP application can increase serum albumin. Additionally, high concentrations of platelets and growth factor in PRP (TGF-β, VEGF) may also play a key role by stimulating epithelial and endothelial cell regeneration, boost angiogenesis and collagen deposition, and consequently accelerate the healing process.[17, 18] Better wound healing of surgical incisions and tears can reduce serum albumin leakage or exudation to the extravascular space. At the same time, various growth factors in PRP were proven to exert some modulatory effects on acute and chronic inflammation.[17] For example, TGF-β was reported to prevent excessive leukocyte recruitment at the lesion sites[19] and HGF seems to have a crucial anti-inflammatory function by inhibiting NF-κB signaling.[20] By regulating and inhibiting excessive inflammation, PRP can reduce systematic protein consumption and thus slow down albumin catabolism in the perioperative period. Additionally, some other growth factors (such as IGF-1) in PRP were reported to promote protein synthesis and increase serum albumin and total protein levels in some liver diseases or injuries.[21–23] Interestingly, we found that serum total protein showed the same trends as serum albumin. Taken together, albumin in PRP, reduced protein degradation, reduced protein catabolism, and increased protein production may also contribute to the increase in serum albumin levels.
2) The proportion of patients with pleural effusion is reduced
Pleural effusion demonstrated by serial CT is a common finding in patients with AAD (87.5%).[24] It is a common complication of cardiac surgery, and it is associated with postoperative mortality and significant resource consumption.[25] The most common conditions that result in effusion are cardiac failure, pneumonia, and increased pleural membrane permeability.[26]
In the present study, the proportion of patients with pleural effusion in the first postoperative CTA report was significantly lower in the PRP group than in the non-PRP group. This may be explained as follows. Better surgical wound healing and higher plasma colloid oncotic pressure due to increased serum albumin levels can reduce fluid leakage or exudation into the pleural space. Furthermore, recent studies demonstrated that PRP attenuated these cardiac pathological changes by exerting anti-inflammatory effects and promoting cardiomyocyte repair in high-dose isoproterenol-induced cardiotoxicity and LPS-induced cardiac injury rat models.[27, 28] Mishra found that PRP-treated mice had a greater left ventricular ejection fraction after undergoing ischemia and ischemia–reperfusion than PBS controls.[29] Furthermore, after acute myocardial infarction for 8 weeks, PRP was reported to structurally and functionally improve the injured heart muscle in pigs.[30] Therefore, PRP may mediate the repair and regeneration of cells in the early stage of cardiac injury and thus improve cardiac output, which may play a key role in decreasing the incidence of postoperative pleural effusion.
However, there were no differences in the proportion of patients with pericardial effusion between the two groups, though the association between pericardial and pleural effusion has been previously reported in studies primarily investigating pericardial effusion.[25]
3) There were no differences in other postoperative outcomes between the PRP and non-PRP groups
Although the mean levels of Scr and BUN were higher in the PRP group than in the non-PRP group, no statistically significant differences were found. These results contrast with those of Tong, who showed that patients in the PRP group showed higher Scr and lactic acid levels, which were associated with a higher incidence of acute kidney injury on postoperative day 1–3.[11] The diversion may come from different transfusion amounts, anesthesia routines, or operation details. Simultaneously, the results showed no differences in AST and ALT levels, which serve as markers of acute liver injury, between the two groups.