title: The Effect of Normovolemic and Hypervolemic Hemodilution on a Perforator Flap with Twisted Pedicle Model: Experimental Study in Rats.
abstract: BACKGROUND
  Several studies showed the detrimental effect of pedicle torsion on flap survival; however, the impact of hemodilution in this peculiar condition has never been investigated. This study evaluated the effect of acute normovolemic and hypervolemic hemodilution on flap survival in a perforator flap with twisted pedicle model.
  
  
  METHODS
  Sixty-three female Wistar rats were divided into three groups of 21 rats each: group 1, superficial inferior epigastric artery flap, which was elevated bilaterally and transposed back to the abdominal wall with different angles of rotation (i.e., 90, 180, 270, and 360 degrees); group 2, surgery with previous acute normovolemic hemodilution; and group 3, surgery with previous acute hypovolemic hemodilution. Normovolemic hemodilution was obtained, simultaneously removing 2 cc of blood and replacing it with an equal volume of isotonic sodium chloride 0.9% (two-thirds) plus hydroxyethyl starch 6% (one-third). Hypervolemic hemodilution was obtained by hemodilution and a 20 percent blood volume expansion. Microangiography of the flap and histopathologic analyses were performed.
  
  
  RESULTS
  Mean hematocrit values after hemodilution were 27.80 ± 0.04 percent for the acute normovolemic hemodilution group and 27.01 ± 0.03 percent for the acute hypovolemic hemodilution group. Twisting the pedicle at 90, 180, and 270 degrees had no effect on flap survival in all groups. However, 360-degree pedicle torsion showed flap edema, congestion, and necrosis.
  
  
  CONCLUSIONS
  The authors' hemodilution protocol is an effective and reliable method that could be used to further investigate the impact of the hemodynamic changes that occur during hemodilution on flap microcirculation. The results obtained sustain the existence of a strong correlation between necrosis rate and hemodilution.
authors.affiliation: Antalya, Turkey; and Rome, Italy From the Departments of Plastic, Reconstructive and Aesthetic Surgery and Pathology, Akdeniz University School of Medicine; and Sant'Andrea Hospital, School of Medicine and Psychology, "Sapienza" University of Rome.
authors.forename: Matteo
authors.initials: M
authors.lastname: Amoroso
authors.forename: Özlenen
authors.initials: Ö
authors.lastname: Özkan
authors.forename: Cumhur İbrahim
authors.initials: Cİ
authors.lastname: Başsorgun
authors.forename: Önur
authors.initials: Ö
authors.lastname: Ögan
authors.forename: Kerim
authors.initials: K
authors.lastname: Ünal
authors.forename: Benedetto
authors.initials: B
authors.lastname: Longo
authors.forename: Fabio
authors.initials: F
authors.lastname: Santanelli Di Pompeo
authors.forename: Ömer
authors.initials: Ö
authors.lastname: Özkan
mesh_terms: D000818:Animals; D005260:Female; D006085:Graft Survival; D006438:Hemodilution / Q000379:methods*; D061525:Perforator Flap / Q000098:blood supply*; D051381:Rats; D017208:Rats, Wistar; D054159:Torsion, Mechanical
references.citation: Khouri RK. Avoiding free flap failure. Clin Plast Surg. 1992;19:773–781
references.citation: Izquierdo R, Dobrin PB, Fu K, Park F, Galante G. The effect of twist on microvascular anastomotic patency and angiographic luminal dimensions. J Surg Res. 1998;78:60–63
references.citation: Demirseren ME, Yenidunya MO, Yenidunya S. Island rat groin flaps with twisted pedicles. Plast Reconstr Surg. 2004;114:1190–1194
references.citation: Demir A, Acar M, Yldz L, Karacalar A. The effect of twisting on perforator flap viability: An experimental study in rats. Ann Plast Surg. 2006;56:186–189
references.citation: Chang CH, Lim SY, Pyon JK, Bang SI, Oh KS, Mun GH. The influence of pedicle length on the viability of twisted perforator flaps in rats. J Reconstr Microsurg. 2009;25:533–538
references.citation: Ozbek MR, Deune EG, Cooley BC, Khouri RK. Experimental reproduction of free flap errors: A new model of thrombosis. Ann Plast Surg. 1994;32:474–477
references.citation: Bektas G, Ozkan O, Cinpolat A, Bassorgun IC, Ciftcioglu MA, Ozkan O. Comparing the effects of pedicle torsion on axial or perforator flaps; improving the perforator flap resistance to pedicle torsion with delay phenomenon. J Reconstr Microsurg. 2014;30:531–538
references.citation: Seyhan T, Ertas NM, Bahar T, Borman H. Simplified and versatile use of gluteal perforator flaps for pressure sores. Ann Plast Surg. 2008;60:673–678
references.citation: Jakubietz RG, Jakubietz DF, Gruenert JG, Schmidt K, Meffert RH, Jakubietz MG. Reconstruction of soft tissue defects of the Achilles tendon with rotation flaps, pedicled propeller flaps and free perforator flaps. Microsurgery. 2010;30:608–613
references.citation: Amoroso M, Özkan Ö, Başsorgun CI, et al. The effect of normovolemic and hypervolemic hemodilution on a microsurgical model: Experimental study in rats. Plast Reconstr Surg. 2015;136:512–519
references.citation: Katsaros J. Use of the island tensor fasciae latae flap to cover a chest-wall defect. Plast Reconstr Surg. 1982;69:1007–1009
references.citation: Wong CH, Cui F, Tan BK, et al. Nonlinear finite element simulations to elucidate the determinants of perforator patency in propeller flaps. Ann Plast Surg. 2007;59:672–678
references.citation: Georgiade GS, Voci VE, Riefkohl R, Scheflan M. Potential problems with the transverse rectus abdominis myocutaneous flap in breast reconstruction and how to avoid them. Br J Plast Surg. 1984;37:121–125
references.citation: Almeida MF, da Costa PR, Okawa RY. Reverse-flow island sural flap. Plast Reconstr Surg. 2002;109:583–591
references.citation: Gokrem S, Sarifakioğlu N, Toksoy K, Terzioğlu A, Aslan G. Effects of 360-degree pedicle torsion on island skin flaps: Experimental study in rats. J Reconstr Microsurg. 2005;21:313–316
references.citation: Lee HJ, Lim SY, Pyon JK, et al. The influence of pedicle tension and twist on perforator flap viability in rats. J Reconstr Microsurg. 2011;27:433–438
references.citation: Topalan M, Bilgin SS, Ip WY, Chow SP. Effect of torsion on microarterial anastomosis patency. Microsurgery. 2003;23:56–59