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complications. Eighty‑two percent of these 113 cases a concentration of more than 0.8 mmol/L was reached by
demonstrated some form of circulatory compromise a needle‑type H sensor (Unisense, Aarhus, Denmark).
2
within 24 h after surgery.
Experimental protocol and groups
Postoperative hyperbaric oxygen (HBO) therapy has been Fifty male SD rats were divided randomly into five groups
used in plastic surgery in the treatment of random skin with 10 animals in each group: (1) a sham‑operated
flaps, axial skin flaps, and flaps with survival problems with group (sham: no IR, HBO, HRS or normal saline injection).
satisfactory results. [2,3] The effect of HBO preconditioning Rats in the sham group underwent the same surgery
has also been studied in many animal models including as the rats in the other four groups but without the
stroke and spinal cord injury. In a study using a rat period of ischemia; (2) IR group: 6 h of ischemia was
[5]
[4]
skin flap model, HBO preconditioning was found to induced by clamping the right pedicle, followed by an
improve skin flap survival and depress tumor necrosis injected intraperitoneally of 5 mL/kg normal saline, 10 min
factor‑α (TNF‑α) expression in skin tissue. [6] prior to reperfusion; (3) HRS‑treated group: 6 h of ischemia
was induced by clamping the right pedicle, followed by an
In 2007, Ohsawa et al. reported that inhalation of H intraperitoneally injection of 5 mL/kg HRS, 10 min prior to
[7]
2
could selectively mitigate •OH (oxhydryl), generating reperfusion; (4) HBO group: 6 h of ischemia was induced
an antioxidant effect in a rat model of middle cerebral by clamping the right pedicle after HBO preconditioning
artery occlusion without affecting the signaling of other for 4 times; and (5) HBO and HRS group: 6 h of ischemia
reactive oxygen species (ROS). Subsequently, H was shown was induced by clamping the right pedicle after HBO
2
to have protective effects on ischemic/reperfusion (IR) preconditioning for 4 times. 5 mL/kg HRS was administered
injury in various organs including the liver, heart, kidneys by an intraperitoneally injection, 10 min prior to reperfusion.
and small intestine. [8‑11] The authors have independently
verified this protective effect. [12] Hyperbaric oxygen preconditioning
Rats in the HBO and HBO + HRS groups were treated
It is widely accepted that IR injury is a critical factor in with HBO 2 days before surgery. Treatment included
flap failure while apoptosis is one important feature of HBO exposure 4 times for 60 min every 12 h
the IR process. [13,14] In this study, the synergistic effects (total exposure time of 4 h). 2 L/min of 100% oxygen
of HBO preconditioning and hydrogen‑rich saline (HRS) was supplied continuously at 0.25 MPa during the
treatment were evaluated for their effects on skin flap HBO treatment. Compression and decompression were
survival and apoptosis in a rat IR skin flap model.
performed at 5 psi/min. The time at which the HBO
chamber pressure reached 0.25 MPa and remained stable
METHODS was recorded. Calcium carbonate crystals were placed in
the chamber to prevent CO accumulation. Flap surgery
2
Animals began 2 h following the final HBO treatment.
All protocols were approved by the Committee on Animal
Rights Protection of Peking Union Medical College Hospital Skip flap survival and perfusion evaluation
and were in accordance with the National Institutes of Skin flap survival was evaluated 72 h after reperfusion by
Health guidelines for the care and use of laboratory general observation of survival and necrotic phenomena
animals. Adult male Sprague‑Dawley (SD) rats weighing and subsequently confirmed by laser speckle contrast
280‑320 g were used in this study. The rats were housed in analysis cameras (Perimed AB, Stockholm, Sweden).
individual cages under standard conditions with 22‑25 °C The surviving and necrotic areas were measured. The
and 12 h of a light‑dark cycle. The rats were fed a normal percentage of flap survival was defined as the ratio of the
diet with water provided ad lib pre‑ and post‑operatively. surviving area to the original flap area.
Epigastric skin flap preparation To evaluate skin flap perfusion, the rats were secured
An extended epigastric adipocutaneous flap (6 cm × 9 cm) onto the operative bed such that the entire flap, including
was raised over the abdomen in each animal. The left part of the normal abdominal skin, was exposed. The
[12]
superficial epigastric artery and vein were ligated, and PeriScan PSI system (Perimed AB, Stockholm, Sweden)
the right was retained as the pedicle. The pedicle artery was positioned above the rats, imaging an area of
and vein were occluded with a microvascular clamp and 11 cm × 7.5 cm. The image acquisition rate was 3 Hz
and lasted for 3 min. The ambient temperature was
6 h of skin flap ischemia was induced. The flap was then maintained between 22 °C and 25 °C during this process.
resutured with a silicone sheet of 0.1 mm deep to it to Perfusion of the necrotic and survival areas was analyzed.
prevent neovascularization from the wound bed. The Vascular flow was measured using perfusion units (PUs).
clamp was removed, and the flap was reperfused at the
end of the ischemic period. Heparin (50,000 U/L in 0.5 mL Rats were sacrificed on the 3rd postoperative day with
saline) was injected into the left epigastric artery to avoid overdose anesthesia after skin flap survival and perfusion
thrombus formation prior to ligation. evaluation. The survival flaps were harvested for sampling.
Hydrogen‑rich saline production TdT‑mediated dUTP‑X nick end labeling staining
Hydrogen was dissolved in normal saline (20 mL) for and apoptotic index evaluation
20 min with a speed of 0.2 L/min to a supersaturated level. Tissue samples (1 cm in size) were taken from the proximal
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HRS was freshly prepared prior to each use, ensuring that areas of the harvested flaps. Samples were sectioned into
Plast Aesthet Res || Vol 2 || Issue 6 || Nov 12, 2015 333