Effects of hyperbaric oxygen on the replanted extremity subjected to prolonged warm ischaemia

Abstract

In this investigation, the influence of hyperbaric oxygen (HBO) therapy on the survival of a replanted extremity subjected to prolonged warm ischaemia is evaluated. Among the relative contraindications to replantation are prolonged warm ischaemia time, since an obstruction to blood reflow ('no-reflow phenomenon') may occur in amputated parts that are subjected to more than 6h of warm ischaemia. Twenty-three rat hindlimbs were amputated and subjected to 4h of normothermic ischaemia. The average weight of the animals was 500 gm, and re-plantation of the hindlimb was performed by bone fixation followed by microvascular anastomosis of the femoral vessels. Limb re-vascularisation was confirmed at the end of all procedures by the milk test, clinical assessment and pulse oximetry recordings (>90%). Eleven animals served as a control group and no further therapy was instituted, whereas 12 animals served as the study (replantation) group and were subjected to HBO therapy for 3 days postoperatively. The therapy was conducted in a large animal chamber for 90 min at 2.5 ata. Limb survival was assessed by capillary refill upon compression, skin turgor assessment and colour. Confirmation of clinical findings was conducted with daily pulse oximetry readings of >90%. Animals were followed up for 7 days at which point all animals were euthanized or were euthanized earlier if a non-viable limb was present. Two of the 11 limbs in the control group survived following re-plantation, whereas eight of the 12 limbs in the experimental HBO group survived at least 7 days following replantation. This difference was statistically significant (p=0.0361) using chi-square analysis and Fisher's exact test. Although re-plantation of an amputated extremity after prolonged warm ischaemia is considered a relative contraindication due to the possibility of poor outcomes, our results indicate that the window for replantation may be increased if adjunctive HBO therapy is employed in the postoperative period.