Reply: Blood Congestion Can Be Rescued by Hemodilution in a Random-Pattern Skin Flap
Di Lorenzo et al. described that they use hemodilution with saline containing a proton-pump inhibitor, an antiplatelet drug, and prednisolone 12 hours before microsurgical flap transfer to seek better flap survival. Although preoperative hemodilution protocols are not yet standardized, we agree with their idea regarding the importance and potential benefits of perioperative systemic conditioning, including hemodilution. We do yet not routinely use intentional preoperative hemodilution but believe that the clinical application of the theory is promising and that further studies are needed to verify and establish a standard protocol. What we currently apply hemodilution for is to avoid unnecessary blood transfusion and infuse crystalloids or colloids for recovering the loss of plasma volume during or after flap surgery.
As for their concern about the use of colloids, we usually use a combination of crystalloids and colloids for hemorrhage or hypovolemia unless blood products are required. There is controversy regarding crystalloids versus colloids and which one is more effective and safer for maintaining plasma volume in shock patients. A multicenter, randomized, controlled study showed that patients with severe sepsis receiving hydroxyethyl starch had an increased risk of death on day 90 and were more likely to require renal-replacement therapy compared with those receiving Ringer acetate.2 In contrast, a systematic review researching 59 articles concluded that the current general restrictions on the use of colloids for volume replacement are not supported by scientific evidence.3 They also indicated that acute kidney injury was significantly reduced by colloid therapy compared with crystalloid therapy in patients with traumatic injuries.3
Circulatory shock, a critical low blood perfusion to tissues, is classified into four main types based on underlying cause: hypovolemic (such as hemorrhage), cardiogenic, distributive (such as sepsis), and obstructive. We believe that colloid therapy is more effective for acute hemorrhagic shock compared with crystalloid therapy, although it may be harmful for septic shock without loss of colloids because kidneys can be damaged by colloid overload. In addition, adverse effects of hydroxyethyl starch such as acute renal failure seem to correlate to its molecular weight. Hydroxyethyl starch 70/0.5 (Salinhes; Fresenius Kabi Japan, Tokyo, Japan), very low-molecular-weight hydroxyethyl starch, is considered less harmful than hydroxyethyl starch 130/0.4 (Voluven; Fresenius Kabi, Bad Homburg, Germany) or hydroxyethyl starch 130/0.42 (Tetraspan; B. Braun, Melsungen, Germany), low-molecular-weight hydroxyethyl starch used in European countries. It was indicated that hydroxyethyl starch 70/0.5, but not Ringer acetate, increased the hepatic blood flow, suggesting that it is also effective for promoting flap circulation.4 Thus, we regard the low-molecular-weight hydroxyethyl starch as an appropriate solution used in flap surgery unless patients have serious risks such as renal dysfunction or disorder of blood coagulation.