The Effect of Hyperbaric Oxygen on Ischemia–Reperfusion Injury

Improving the ischemia-reperfusion injury in vascularized composite allotransplantation: Clinical experience and experimental implications

Long-time ischemia worsening transplant outcomes in vascularized composite allotransplantation (VCA) is often neglected. Ischemia-reperfusion injury (IRI) is an inevitable event that follows reperfusion after a period of cold static storage. The pathophysiological mechanism activates local inflammation, which is a barrier to allograft long-term immune tolerance. The previous publications have not clearly described the relationship between the tissue damage and ischemia time, nor the rejection grade. In this review, we found that the rejection episodes and rejection grade are usually related to the ischemia time, both in clinical and experimental aspects. Moreover, we summarized the potential therapeutic measures to mitigate the ischemia-reperfusion injury. Compare to static preservation, machine perfusion is a promising method that can keep VCA tissue viability and extend preservation time, which is especially beneficial for the expansion of the donor pool and better MHC-matching.

Comparison of ischemic preconditioning and BotulinumA Toxin injection for the prevention of ischemia-reperfusion injury in musculocutaneous flaps

Background/aim

The aim of the study was to evaluate the protective effect of Botulinum A toxin injection against ischemia-reperfusion injury.

Materials and methods

Thirty-two Sprague-Dawley rats were divided into: control, ischemia-reperfusion, ischemic preconditioning, and botulinum groups. In all groups the musculocutaneous pedicle flap was occluded for 4 h, and then reperfused to induce ischemia-reperfusion injury. Serum and tissue myeloperoxidase (MPO) and nitric oxide (NO) levels were measured at 24 h and at 10 days.

Results

Tissue MPO levels did not differ significantly between the ischemic preconditioning and botulinum groups at 24 h but was significantly lower in the botulinum group at 10 days. Tissue NO levels were significantly higher in the ischemic preconditioning group compared to the botulinum group at 24 h and at 10 days. Serum MPO showed no significant difference between these two groups at 24 h but was significantly lower in the ischemic preconditioning group compared to the botulinum group at 10 days. Serum NO levels were not significantly different at 24 h but significantly higher in the botulinum group at 10 days.

Conclusion

Findings show that botulinum has a protective effect against the ischemia-reperfusion injury via increased NO and decreased MPO levels in tissue. Based on tissue NO levels, ischemic preconditioning was significantly higher than botulinum.

Study of the Effect of Hyperbaric Oxygen Therapy on the Viability of Dorsal Cutaneous Flaps in Tobacco-Exposed Rats

BACKGROUND

Smoking causes a threefold increase in the risk of surgical complications in flaps. Hyperbaric oxygen therapy (HBOT) increases the viability of chronic wounds. However, there are few studies concerning the effects of HBOT on surgical flaps in patients who smoke. This study aimed to analyze the effect of HBOT on the viability of cutaneous flaps in tobacco-exposed rats.

METHODS

Twenty Wistar rats were exposed to tobacco smoke for two months. Following this period, all animals underwent a dorsal cutaneous flap (3 × 10 cm) surgery and were divided into two groups: control (n = 10) and HBOT (n = 10). HBOT was performed in seven daily sessions (2 ATA, 90 min). After seven days, the animals were euthanized. The outcomes were total area, viable area, viable area/total area rate, analysis of dermal appendages and angiogenesis (hematoxylin-eosin), and gene expression analysis of iNOS and VEGF-a biomarkers.

RESULTS

The HBOT group showed an increase in viable area compared with the control group (84% versus 47%, p = 0.009, respectively). The HBOT group also showed an increase in appendage units (1.69 ± 0.54 versus 1.87 ± 0.58, p = 0.04) and angiogenesis density (1.29 ± 0.45 versus 1.82 ± 0.64, p < 0.001) compared to the control group. There was a difference between the control and HBOT groups in iNOS levels (0.926 ± 1.4 versus 0.04 ± 0.1 p = 0.002, respectively). However, this study did not show a difference between the groups concerning the gene expression of VEGF-a.

CONCLUSION

The use of hyperbaric oxygen therapy increased the viability of cutaneous flaps in tobacco-exposed rats and decreased iNOS mRNA levels; however, it did not change VEGF-a levels. Level of Evidence IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Ischemia-reperfusion injury in a rat microvascular skin free flap model: A histological, genetic, and blood flow study

Ischemia reperfusion injury is associated with tissue damage and inflammation, and is one of the main factors causing flap failure in reconstructive microsurgery. Although ischemia-reperfusion (I/R) injury is a well-studied aspect of flap survival, its biological mechanisms remain to be elucidated. To better understand the biological processes of ischemia reperfusion injury, and to develop further therapeutic strategies, the main objective of this study was to identify the gene expression pattern and histological changes in an I/R injury animal model. Fourteen rats (n = 7/group) were randomly divided into control or ischemia-reperfusion group (8 hours of ischemia). Microsurgical anastomoses were objectively assessed using transit-time-ultrasound technology. Seven days after surgery, flap survival was evaluated and tissue samples were harvested for anatomopathological and gene-expression analyses.The I/R injury reduced the survival of free flaps and histological analyses revealed a subcutaneous edema together with an inflammatory infiltrate. Interestingly, the Arginase 1 expression level as well as the ratio of Arginase 1/Nitric oxide synthase 2 showed a significant increase in the I/R group. In summary, here we describe a well-characterized I/R animal model that may serve to evaluate therapeutic agents under reproducible and controlled conditions. Moreover, this model could be especially useful for the evaluation of arginase inhibitors and different compounds of potential interest in reconstructive microsurgery.

Heat Shock Protein 70 (HSP70) Reduces Hepatic Inflammatory and Oxidative Damage in a Rat Model of Liver Ischemia/Reperfusion Injury with Hyperbaric Oxygen Preconditioning

Background

Several clinical conditions can cause hepatic ischemia/reperfusion (I/R) injury. This study aimed to determine the mechanism of the protective effect of hyperbaric oxygen preconditioning (HBO₂P) on hepatic ischemia/reperfusion (I/R) injury in a rat model, and to investigate the effects on HBO₂P and I/R injury of blocking HSP70 using antibody (Ab) pretreatment.

Material/Methods

Male Sprague-Dawley rats underwent HBO₂P for 60 min at 2.0 atmosphere absolute (ATA) pressure for five consecutive days before surgical hepatic I/R injury, performed by clamping the portal vein and hepatic lobe. Four groups studied included: the non-HBO₂P+ non-I/R group, which underwent sham surgery (N=10); the non-HBO₂P + I/R group (N=10); the HBO₂P + I/R group (N=10); and the HBO₂P + HSP70-Ab + I/R group (N=10) received one dose of HSP70 antibody one day before hepatic I/R injury. Serum lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and hepatic malondialdehyde (MDA) and myeloperoxidase (MPO) were measured biochemically. Rat liver tissues were examined histologically.

Results

In rats with hepatic I/R injury without HSP70 antibody pre-treatment, HBO₂P significantly reduced hepatic injury and levels of LDH, AST, ALT, TNF-α, IL-6, MDA, and MPO levels; in comparison, the group pre-treated with an antibody to inhibit HSP70 (the HBO₂P + HSP70-Ab + I/R group) showed significant reversal of the beneficial effects of HBO₂P on hepatic I/R injury (p<0.05).

Conclusions

In a rat model of hepatic I/R injury with HBO₂P, HSP70 reduced hepatic inflammatory and oxidative damage.

Postconditioning Ozone Alleviates Ischemia-Reperfusion Injury and Enhances Flap Endurance in Rats

Introduction: Muscle-flap transferring is a routine approach utilized in reconstructive operations; however, flap morbidity is often a source of post-operative difficulty. Ischemia-Reperfusion Injury (IRI) is an important contributor to the viability of flaps after transferring. The goal of this research was for assess the probable useful impacts of ozone on flap survival in a rat muscle-flap design. Materials and Methods: We examined the effects of postconditioning ozone administration on viability of pedicled composite flaps. Twenty-eight Wistar rats were randomized into four groups: sham-operated (S), ischemia-reperfusion (IR), sham-operated + ozone (O), IR + ozone (IR + O), respectively. The animals were sacrificed on the eighth day. In a general histological evaluation, flap tissues were examined with a light microscope, and apoptotic cells were counted. The Apoptotic Index (AI) was then calculated. Flap-tissue samples were sent for analyses of malondialdehyde (MDA), catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and protein carbonyl (PCO), and blood samples were sent for analyses of Total Oxidant Score (TOS), and Total Antioxidant Capacity (TAC). Data were evaluated statistically using the Kruskal-Wallis test. Results: The histomorphometric score was remarkably greater in O (p = .002). The AI was greater in IR (p = .002). The antioxidant parameters values as regards SOD, GSH-Px, CAT, and TAC were found to be greater in O (p < .005). The oxidant parameters values as regards MDA, PCO, TOS were found to be greater in IR (p < .005). Discussion: The current research indicates that ozone application can attenuate the muscle-flap injury brought about by IR through triggering the increase of the antioxidant capacity.

Ischaemia-reperfusion injury and hyperbaric oxygen pathways: a review of cellular mechanisms

Ischaemia-induced tissue injury has wide-ranging clinical implications including myocardial infarction, stroke, compartment syndrome, ischaemic renal failure and replantation and revascularization. However, the restoration of blood flow produces a 'second hit' phenomenon, the effect of which is greater than the initial ischaemic event and characterizes ischaemia-reperfusion (IR) injury. Some examples of potential settings of IR injury include: following thrombolytic therapy for stroke, invasive cardiovascular procedures, solid organ transplantation, and major trauma resuscitation. Pathophysiological events of IR injury are the result of reactive oxygen species (ROS) production, microvascular vasoconstriction, and ultimately endothelial cell-neutrophil adhesion with subsequent neutrophil infiltration of the affected tissue. Initially thought to increase the amount of free radical oxygen in the system, hyperbaric oxygen (HBO) has demonstrated a protective effect on tissues by influencing the same mechanisms responsible for IR injury. Consequently, HBO has tremendous therapeutic value. We review the biochemical mechanisms of ischaemia-reperfusion injury and the effects of HBO following ischaemia-reperfusion.

Etanercept protects myocutaneous flaps from ischaemia reperfusion injury: An experimental study in a rat tram flap model

Background Being an inevitable component of free tissue transfer, ischemia-reperfusion injury tends to contribute to flap failure. TNF-α is an important proinflammatory cytokine and a prominent mediator of the ischemia-reperfusion injury. Etanercept, a soluble TNF-α binding protein, has shown anti-inflammatory and anti-apoptotic effects in animal models of renal and myocardial ischemia-reperfusion injury. We have designed an experimental study to investigate the effect of etanercept on myocutaneous ischemia-reperfusion injury on transverse rectus abdominis myocutaneous flap model in rats. Methods Twenty-four male Sprague-Dawley rats were divided into 3 groups: In group 1 (sham), the TRAM flap was raised and sutured back without further intervention. In group 2 (control), the flap was raised and the ischemia-reperfusion protocol was followed. In group 3, etanercept (10 mg/kg, i.v.) was administered 10 minutes before reperfusion. At the end of the reperfusion period, biochemical and histolopathological evaluations were performed on serum and tissue samples. Results In the etanercept group the IMA and 8-OHdG levels (p = 0.005 and p = 0.004, respectively) were found significantly lower, and the GSH and SOD levels (p = 0.01 and p < 0.001, respectively) significantly higher in comparison to the control group. The histopathological analysis has revealed a lower degree of hyalinization, degenerated muscle fibers and nuclear change in the etanercept group compared to the control group. Conclusion The results of our experimental study indicate that etanercept offers protection against ischemia-reperfusion injury in skeletal muscle tissue, enhancing the TRAM flap viability. The ability of etanercept to induce ischemic tolerance suggests that it may be applicable in free-flap surgery.

Effect of hyperbaric oxygen therapy on healing in an experimental model of degloving injury in tails of nicotine-treated rats

The aim of this study was to investigate the effect of hyperbaric oxygen (HBO) therapy on healing in an experimental model of a degloving injury of the tails of nicotine-treated rats. Thirty-two male Sprague-Dawley rats were randomized to four groups (n = 8): nicotine (group 1); HBO (group 2); nicotine + HBO (group 3); and control (group 4). The mean length of the necrotic parts of the tails at the degloving injury site was significantly higher in group 1 compared with groups 2, 3, and 4, and was significantly lower in group 2 compared with groups 1, 3, and 4. The mean histopathological stage of ulcers at the degloving injury site was statistically significantly higher (more severe) in group 1 compared with groups 2, 3, and 4, and was statistically significantly lower in group 2 compared with groups 1, 3, and 4. It appears that the negative effects of nicotine on wound healing in degloving injuries are negated by the positive effects of immediate HBO therapy.

The effect of hyperbaric oxygen on nitric oxide synthase activity and expression in ischemia-reperfusion injury

BACKGROUND

Hyperbaric oxygen (HBO) mitigates ischemia-reperfusion (IR) injury via a nitric oxide mechanism that is nitric oxide synthase (NOS) dependent. The purpose of this study was to investigate this NOS-dependent mechanism by examining isoform-specific, tissue-specific, and time-specific upregulation of NOS mRNA, protein, and enzymatic activity.

METHODS

We raised a gracilis flap in Wistar rats that were separated into early and late phases. Treatment groups included nonischemic control, IR, HBO-treated ischemia-reperfusion (IR-HBO), and nonischemic HBO control. We harvested tissue-specific samples from gracilis, rectus femoris, aorta, and pulmonary tissues and processed them by reverse transcription polymerase chain reaction and Western blot to determine upregulation of isoform-specific NOS mRNA and protein. We also harvested tissue for NOS activity to investigate upregulation of enzymatic activity. Data are presented as mean ± standard error of the mean with statistics performed by analysis of variance. P ≤ 0.05 was considered significant.

RESULTS

There was no increase in NOS mRNA in the early phase. In the late phase, there was a significant increase in endothelial-derived NOS (eNOS) mRNA in IR-HBO compared with IR in gracilis muscle (79.4 ± 22.3 versus 36.1 ± 4.5; P < 0.05) and pulmonary tissues (91.0 ± 31.2 versus 30.2 ± 3.1; P < 0.01). There was a significant increase in the late-phase eNOS pulmonary protein IR-HBO group compared with IR (235.5 ± 46.8 versus 125.2 ± 14.7; P < 0.05). Early-phase NOS activity was significantly increased in IR-HBO compared with IR in pulmonary tissue only (0.049 ± 0.009 versus 0.023 ± 0.003; P < 0.05).

CONCLUSIONS

The NOS-dependent effects of HBO on IR injury may result from a systemic effect involving an early increase in eNOS enzymatic activity followed by a late-phase increase in eNOS protein expression within the pulmonary tissues.

A comparison of the effects of epidural and spinal anesthesia with ischemia-reperfusion injury on the rat transverse rectus abdominis musculocutaneous flap

The purpose of this study is to compare the effects of spinal and epidural anesthesia on a rat transverse rectus abdominus myocutaneous flap ischemia-reperfusion injury model.Forty Sprague-Dawley rats were divided into 4 experimental groups: group I (n = 10), sham group; group II (n = 10), control group; group III (n = 10), epidural group; and group IV (n = 10), spinal group. After the elevation of the transverse rectus abdominus myocutaneous flaps, all groups except for the sham group were subjected to normothermic no-flow ischemia for 4 hours, followed by a reperfusion period of 2 hours. At the end of the reperfusion period, biochemical and histopathological evaluations were performed on tissue samples.Although there was no significant difference concerning the malonyldialdehyde, nitric oxide, and paraoxonase levels in the spinal and epidural groups, the total antioxidant state levels were significantly increased, and the total oxidative stress levels were significantly decreased in the epidural group in comparison to the spinal group. The pathological evaluation showed that findings related to inflammation, nuclear change rates and hyalinization were significantly higher in the spinal group compared with the epidural group.Epidural anesthesia can be considered as a more suitable method that enables a decrease in ischemia-reperfusion injuries in the muscle flaps.

Effects of hyperbaric oxygen and N-acetylcysteine in survival of random pattern skin flaps in rats

OBJECTIVE

Our aim is to investigate the role of HBO (hyperbaric oxygen), NAC (N-acetylcysteine), and HBO plus NAC on the necrosis area of random rat's skin flaps of a modified McFarlane flap design.

MATERIALS AND METHODS

Thirty-two male Wistar rats were randomly divided into four groups: G-S (sham: n = 8), G-NAC (NAC: n = 8), G-HBO (HBO: n = 8), and G-HN (HBO plus NAC: n = 8). A rectangular skin flap (2 × 8 cm(2)) was dissected from the muscular dorsal layer, preserving the cranial pedicle. Polyethylene film was placed over the muscular layer and an interrupted 3.0 nylon suture was employed to fix the flap into the original place. On the eighth day, full-thickness biopsy samples (2 × 1 cm(2)) were collected from the proximal, middle, and cranial areas of the skin flap, and in a site away from the flap labelled as the control area.

RESULTS

The measurements of necrotic areas in the groups were 18.3% in G-S, 24.3% in G-NAC, 12.6% in G-HBO, and 14.9% in G-HN. Significant difference was observed between the groups G-HBO and G-HN as well as G-NAC.

CONCLUSION

HBO is associated with reduced area of necrosis of skin flap. The G-NAC group was associated with poor results when examined in isolation. The association between HBO and NAC did not produce favourable results with respect to the use of HBO alone. These findings suggest that the diffusion of oxygen through the interstitial space was the determining factor of more favourable results of HBO.

Spatio-temporal course of macrophage-like cell accumulation after experimental embolic stroke depending on treatment with tissue plasminogen activator and its combination with hyperbaric oxygenation

Inflammation following ischaemic stroke attracts high priority in current research, particularly using human-like models and long-term observation periods considering translational aspects. The present study aimed on the spatio-temporal course of macrophage-like cell accumulation after experimental thromboembolic stroke and addressed microglial and astroglial reactions in the ischaemic border zone. Further, effects of tissue plasminogen activator (tPA) as currently best treatment for stroke and the potentially neuroprotective co-administration of hyperbaric oxygen (HBO) were investigated. Rats underwent middle cerebral artery occlusion and were assigned to control, tPA or tPA+HBO. Twenty-four hours, 7, 14 and 28 days were determined as observation time points. The accumulation of macrophage-like cells was semiquantitatively assessed by CD68 staining in the ischaemic area and ischaemic border zone, and linked to the clinical course. CD11b, ionized calcium binding adaptor molecule 1 (Iba), glial fibrillary acidic protein (GFAP) and Neuronal Nuclei (NeuN) were applied to reveal delayed glial and neuronal alterations. In all groups, the accumulation of macrophage-like cells increased distinctly from 24 hours to 7 days post ischaemia. tPA+HBO tended to decrease macrophage-like cell accumulation at day 14 and 28. Overall, a trend towards an association of increased accumulation and pronounced reduction of the neurological deficit was found. Concerning delayed inflammatory reactions, an activation of microglia and astrocytes with co-occurring neuronal loss was observed on day 28. Thereby, astrogliosis was found circularly in contrast to microglial activation directly in the ischaemic area. This study supports previous data on long-lasting inflammatory processes following experimental stroke, and additionally provides region-specific details on glial reactions. The tendency towards a decreasing macrophage-like cell accumulation after tPA+HBO needs to be discussed critically since neuroprotective properties were recently ascribed to long-term inflammatory processes.

Hyperbaric oxygen therapy protects the liver from apoptosis caused by ischemia-reperfusion injury in rats

PURPOSE

: The present paper aimed to investigate the role of hyperbaric oxygen treatment (HBO) and the apoptosis in rat liver ischemia-reperfusion injury (IRI).

METHODS

: Thirty-seven male Wistar rats were subjected to 30 minutes of hepatic ischemia and 30 minutes of reperfusion and randomly distributed into six groups: G-I/R (n = 8), control without HBO; G-HBO/I (n = 8), HBO only during the ischemia period; G-HBO/R (n = 8), HBO only during the reperfusion period; G-HBO-I/R (n = 8), HBO during both the ischemia and reperfusion periods; G-Sh (n = 3), HBO without ischemia or reperfusion as sham group; G-C (n = 2) for control of current apoptosis expression on the normal liver tissue. HBO was carried out using a transparent, cylindrical acrylic chamber with a pressure of 2.0 ATA. Hepatic samples were stained for caspase-3 cleavage.

RESULTS

: Apoptotic cells were identified in all groups. In the hepatic specimens of animals HBO-treated during ischemia (GHBO-I), there was a significant decrease (P < 0.001) in the number of cells undergoing apoptosis (1.62 +/- 0.91). The apoptotic index showed no significant difference in the animals HBO-treated during ischemia/reperfusion (5.75 +/- 1.28) compared with the G-I/R (3.5 +/- 0.75), which had no HBO treatment. The apoptosis index (11.25 +/- 1.90) was significantly higher (P < 0.01) in HBO-treated animals during the reperfusion period when compared with any of the other groups.

CONCLUSION

: A favorable effect was obtained when hyperbaric oxygen was administered early during ischemia. The hyperbaric oxygen in later periods of reperfusion was associated with a more severe apoptosis index. (c) 2009 Wiley-Liss, Inc. Microsurgery 2009.

Effect of hyperbaric oxygen on survival of composite grafts in rats

Most treatment with hyperbaric oxygen (HBO) in plastic surgery is for wounds, burns, crush injuries, and infections. We aimed to find out if HBO increases the survival of composite grafts in rats. Twenty Sprague-Dawley rats were randomly assigned to two equal groups (treatment and control). A template 30 x 30 mm was placed on the skin and a composite graft taken from the upper back was harvested and then resutured to the fascia in situ. The treated group was placed in a hyperbaric chamber set at 202 kPa and 100% oxygen for 90 minutes daily for two weeks. Control animals were given no treatment. After death the mean surviving internal surface area of the graft was 372.5 (117.9) mm2 in the control group and 561.3 (85.7) mm2 in the experimental group (p=0.001). Treatment with HBO improved the surviving area of composite grafts in rats, and the beneficial effect was prominent only on the inner surface of the graft.

Endothelial-neutrophil interactions during ischemia and reperfusion injury: basic mechanisms of hyperbaric oxygen

Ischemia/reperfusion injury plays a central role in the development of tissue injury during multiple central nervous system diseases including acute stroke. Neutrophil adhesion to the endothelium indicates a major component of ischemia/reperfusion pathophysiology, and may be a target for therapeutic intervention. Hyperbaric oxygen has been documented to reduce ischemia/reperfusion injury in a number of different experimental models and in a single human randomized clinical trial. One mechanism responsible for the beneficial effect of hyperbaric oxygen in treatment of ischemia/reperfusion injury involves suppression of neutrophil-endothelial adhesion. This review intends to describe the current basic mechanisms responsible for hyperbaric oxygen-mediated inhibition of neutrophil-endothelial interactions following ischemia/reperfusion injury.

Hyperbaric oxygenation attenuates renal ischemia-reperfusion injury in rats

BACKGROUND

Oxygen-derived free radicals play an important role in ischemia-reperfusion injury (IR). Hyperbaric oxygenation (HO) decreases free radical production. The aim of this study was to determine the effect of HO treatment on renal ischemia-reperfusion injury in rats.

METHODS

Rats were divided into four groups. All groups underwent right nephrectomy. Group I served as the control group; group II had left renal ischemia-reperfusion; group III was pretreated with HO; and group IV, ischemia-reperfusion and HO pretreatment. Tissue malondialdehyde (MDA) and glutathione (GSH) levels were measured, and histopathologic damage scored.

RESULTS

HO pretreatment significantly decreased tissue MDA levels and histopathologic scores among rats with IR. There was an increased GSH in HO-pretreated rats with IR; however, the difference was not significant.

CONCLUSION

HO prior to ischemia displayed a beneficial effect on renal IR by reducing oxygen radical peroxidation of lipid membranes.

Hyperbaric Oxygen Therapy Attenuates Renal Ischemia/Reperfusion Injury in Rats

OBJECTIVE

Renal ischemia/reperfusion (I/R) injury occurs in both native and transplanted kidneys. Hyperbaric oxygen (HBO) has been shown to prevent I/R injury in different tissues. The aim of this study was to evaluate the effect of HBO on renal I/R injury in rats.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly assigned to one of three groups. The Control group (n = 6) received right nephrectomy. The I/R (n = 6) and I/R+HBO groups (n = 6) received 30 min left renal ischemia followed by 24 h of reperfusion after right nephrectomy. The I/R+HBO group (n = 6) received additional HBO therapy for 60 min at 2.5 absolute atmospheres starting at the initial 15th minute of reperfusion.

RESULTS

In the I/R group, blood urea nitrogen (BUN) and creatinine levels increased significantly compared with the Control and I/R+HBO groups (p < 0.05). BUN and creatinine levels were similar in the Control and I/R+HBO groups. Kidney samples from I/R group rats revealed severe tubular damage and neutrophil infiltration at histopathological examination. The animals treated with HBO showed markedly improved lesions and less neutrophil infiltration compared with the I/R group (p < 0.05).

CONCLUSIONS

HBO exhibited marked protection against I/R injury in this study as measured using BUN and creatinine levels and renal histopathology. However, further studies are needed to clarify the renoprotective effect of HBO on I/R injury.

Hyperbaric oxygen therapy and liver transplantation

Liver transplantation is the treatment of choice for end stage liver disease and is often used for primary liver malignancies. The main limitation of its wider application is the availability of suitable donor organs. The use of marginal donor organs, split-liver transplantation and living-related liver transplantation techniques contribute to increase the donor pool. However, the use of these techniques is associated with a higher risk of post transplantation organ dysfunction, predominantly due to ischaemia, preservation and reperfusion injury (IPRI). A number of studies have demonstrated that hyperbaric oxygen (HBO) therapy influences IPRI and consequential acute cellular rejection. This article reviews the rationale of HBO therapy in the field of transplantation with particular emphasis on liver transplantation.

Hyperbaric oxygen protects from sepsis mortality via an interleukin-10-dependent mechanism

OBJECTIVE

This study was performed to determine whether hyperbaric oxygen (HBO2) therapy is protective in cecal ligation and puncture (CLP)-induced sepsis and if protection is dependent on oxygen dosing. We also wished to determine whether HBO2 affected bacterial clearance or altered macrophage production of interleukin-10 (IL-10)s in the setting of CLP sepsis. Finally, we wished to determine whether the mechanism of HBO2 protection in sepsis was dependent on IL-10 production.

DESIGN

Prospective, experimental study.

SETTING

University experimental research laboratory.

SUBJECTS

C57BL/6 and C57BL/6 IL-10 mice.

INTERVENTIONS

Sepsis was induced by CLP. Mice were randomized to receive a 1.5-hr HBO2 treatment at either 1, 2.5, or 3 atmospheres absolute every 12 hrs or HBO2 at 2.5 atmospheres absolute every 24 hrs. Mice were also harvested at 24 hrs for determination of bacterial load and isolation and study of CD11b peritoneal macrophages.

MEASUREMENTS AND MAIN RESULTS

Survival was monitored for 100 hrs after CLP +/- HBO2 treatment. HBO2 significantly improved survival when administered at 2.5 atmospheres absolute every 12 hrs. Other treatment schedules were not protective, and treatment at 3.0 atmospheres absolute significantly worsened survival outcome. Bacterial load was significantly reduced in splenic homogenates but not peritoneal fluid at 24 hrs. Macrophages isolated from HBO2-treated mice demonstrated enhanced IL-10 secretion in response to lipopolysaccharide as compared with CLP controls. Mice genetically deficient in IL-10 expression treated with HBO2 at 2.5 atmospheres absolute every 12 hrs were not protected from CLP-induced mortality.

CONCLUSION

HBO2 may be protective in CLP sepsis within a window of oxygen dosing. The mechanism of HBO2 protection may be potentially linked in part to expression of IL-10, as peritoneal macrophages demonstrated enhanced IL-10 expression and IL-10 mice were not protected by HBO2 treatment.

Potential effects of hyperbaric oxygen therapy in acute pancreatitis

BACKGROUND

To extract from the biomedical published reports, the effects of hyperbaric oxygen (HBO) on inflammatory disease, in particular acute pancreatitis.

METHODS

This review will explain these effects and evaluate potential mechanisms of action of HBO in acute pancreatitis. A Medline/PubMed search (January 1966 to July 2004) with manual cross-referencing was conducted, including all relevant articles investigating the molecular and systemic effects of HBO on inflammatory diseases, particularly focusing on the studies of acute pancreatitis. All publication types, languages and subsets were searched.

RESULTS

Original and review articles and short communications were extracted. The selected original articles covered the molecular and systemic effects of HBO and the effects in inflammatory disease states. The major findings are that HBO can act as an anti-inflammatory agent and as an antimicrobial agent. Many of the effects of HBO would be beneficial in the treatment of acute severe pancreatitis. Work carried out to date in animal models of acute pancreatitis shows promising improvements in severity but studies are limited to date.

CONCLUSION

Acute pancreatitis impairs the pancreatic and systemic microcirculation and causes acute inflammation. These processes are potentially improved by HBO therapy.

Biological effect of far-infrared therapy on increasing skin microcirculation in rats

BACKGROUND/PURPOSE

Insufficient microcirculation of skin leads to acute and chronic tissue ischemia in cases of trauma, reconstructive surgery, diabetes mellitus and peripheral arterial occlusive disease. The autonomic nervous system and nitric oxide (NO) play important roles in maintaining blood perfusion of the skin. Far-infrared (FIR) therapy provides low energy of light emitted from an artificial radiator and has been used to treat many vascular-related disorders. Nevertheless, the mechanisms through which FIR works remain unclear. The present study aims to test the hypothesis that the effect of FIR is through increasing skin microcirculation by a mechanism other than its thermal effect.

METHODS

Sixty rats were used in the present study. A WS TY301 FIR emitter was placed 20 cm above the rats. Skin temperature and blood flow were continuously measured by a K-type thermocouple. Under laboratory control, the abdominal skin temperature steadily increased from 38-39 degrees C, and was kept at constant temperature. Skin microcirculation was measured with a continuous laser Doppler flowmeter.

RESULTS

There was no significant change of skin blood flow during FIR treatment. Skin blood flow increased significantly soon after the removal of the FIR emitter. The stimulating effect on skin blood flow was more significant in the rats treated with FIR for 45 min and could be sustained as long as 60 min. These findings suggested a non-thermic biological effect of FIR on skin microcirculation. The promotive effect of FIR on increasing skin blood flow was not influenced by pretreatment of APP (atropine, propranolol and phentolamine), but was suppressed by pretreatment with NG-nitro-L-arginine methyl ester (an endothelial nitric oxide synthase inhibitor).

CONCLUSION

In conclusion, FIR therapy exerts a NO-related biological effect to increase skin microcirculation in rats. This might bring into perspective the clinical application of FIR to treat ischemic disease by augmenting L-arginine/NO pathway.

Dichloroacetate Reduces Tissue Necrosis in a Rat Transverse Rectus Abdominis Musculocutaneous Flap Model

OBJECTIVE

Ischemia-related complications may occur during postmastectomy transverse rectus abdominis musculocutaneous (TRAM) flap reconstruction. The aim of our study was to investigate whether necrosis of susceptible flap regions could be reduced by dichloroacetate (DCA)-induced stimulation of oxidative metabolism in hypoxic tissue.

METHODS

The study was a randomized control trial using male Sprague-Dawley rats. A pedicled TRAM flap based upon the right inferior epigastric artery was elevated and reapproximated. Animals were randomly assigned to 1 of 5 treatment groups (n = 6). Group I received no DCA; groups II through V were administered 75 mg/kg DCA orally 24 hours preoperative; in addition, groups II through IV received 75 mg/kg/d DCA orally postoperative for 4 days; group III also received 75 mg/kg DCA (IP) intraoperatively; groups IV and V were given 15 mg/kg/d DCA orally for 6 days before the 24-hour preoperative treatment. Four days postsurgery, skin paddles were photographed and assessed for viability. Underlying TRAM muscle was biopsied for histologic analysis. Blood lactate levels were measured at pre- and postoperative time points. The mean percentages of viable skin paddle were as follows: 32.0%+/- 4.0% (group I), 68.1% +/- 6.2% (group II), 84.3% +/- 5.9% (group III), 92.8% +/- 2.0% (group IV), 82.6% +/- 5.8% (group V).

RESULTS

Statistically significant differences were found in all experimental (DCA) groups relative to the controls (P < 0.01). Group IV (6-day DCA preconditioning, plus 24-hour preoperative and 4-day postoperative treatment) displayed the greatest improvement in flap viability, significantly better than other DCA groups (P < 0.01). Group IV also had significantly lower serum lactate levels than controls (P < 0.05). Histologic examination of muscle biopsies revealed reductions in inflammation and necrosis correlating with DCA treatment and skin paddle survival.

CONCLUSIONS

This study indicates that DCA may provide a useful pharmacologic tool for reducing ischemia-related necrosis in TRAM flaps.

Effects of hyperbaric oxygen exposure on experimental hepatic ischemia reperfusion injury: relationship between its timing and neutrophil sequestration

Recent studies have shown that hyperbaric oxygen therapy (HBOT) reduces neutrophil endothelial adherence in venules and also blocks the progressive arteriolar vasoconstriction associated with ischemia-reperfusion (I-R) injury in the extremities and the brain. In order to elucidate the effects of HBOT after I-R in digestive organs, particularly in the liver, we evaluated the following: 1) the relationship between timing of HBOT and tissue damage; and 2) HBOT's effects on neutrophil sequestration. Using a hepatic I-R (45 minute) model in male rats, survival rate, liver tissue damage, and neutrophil accumulation within the sinusoids in the HBOT-treated group (Group H) were compared to those in the nontreated group (Group C). For the HBOT-treated group, HBOT was administered as 100% oxygen, at 2.5 atm absolute, for 60 minutes. When HBOT was given 30 minute after I-R, the survival rate was much better in Group H than in Group C. HBOT performed within 3 hours of I-R markedly suppressed increases in the malondialdehyde level in tissues of the liver and lessened the congestion in the sinusoids. In addition, HBOT just after I-R caused decreased number of cells stained by the naphthol AS-D chloroacetate esterase infiltrating into the sinusoids. HBOT 3 hours after reperfusion, however, showed no clear effects upon neutrophil sequestration compared to Group C. These results indicate that HBOT performed within 3 hours of I-R alleviates hepatic dysfunction and improves the survival rate after I-R. Herein, we propose 1 possible mechanism for these beneficial effects: early HBOT given before neutrophil-mediated injury phase may suppress the accumulation of neutrophils after I-R. In conclusion, we believe that the present study should lead to an improved understanding of HBOT's potential role in hepatic surgery.

Pretreatment with hyperbaric oxygen and its effect on neuropsychometric dysfunction and systemic inflammatory response after cardiopulmonary bypass: A prospective randomized double-blind trial

OBJECTIVE

Animal studies have shown that pretreatment with hyperbaric oxygen can induce central nervous system ischemic tolerance and also modulate the inflammatory response. We evaluated this therapy in patients undergoing cardiopulmonary bypass.

METHODS

Sixty-four patients were prospectively randomized to group A (n = 31; atmospheric air, 1.5 atmospheres absolute) or group B (n = 33; hyperbaric oxygen, 2.4 atmospheres absolute) before on-pump coronary artery bypass grafting. Age, sex, body mass index, diabetes, hypertension, smoking, coronary disease severity, left ventricular function, Parsonnet score, Euroscore, bypass time, myocardial ischemia time, and number of grafts were comparable in both groups. Canadian Cardiovascular Society angina, New York Heart Association dyspnea, and previous myocardial infarction were significantly higher in group B. Inflammatory markers were analyzed before surgery and 2 and 24 hours after bypass. Neuropsychometric testing was performed 48 hours before surgery and 4 months after surgery and included trail making A and B, the Rey auditory verbal learning test, grooved peg board, information processing table A, and digit span forward and backward. Neuropsychometric dysfunction was defined as more than 1 SD deterioration in more than 2 neuropsychometric tests. Chi-square tests, Fisher tests, t tests, and analysis of variance were used as appropriate for statistical analysis.

RESULTS

Group A had a significant postoperative increase in the inflammatory markers soluble E-selectin, CD18, and heat shock protein 70. This was not observed in group B. Neuropsychometric dysfunction was also significantly higher in group A compared with group B. There was no difference in any other early postoperative clinical outcome.

CONCLUSIONS

Our results seem to indicate that pretreatment with hyperbaric oxygen can reduce neuropsychometric dysfunction and also modulate the inflammatory response after cardiopulmonary bypass. However, further multicenter randomized trials are needed to clinically evaluate this form of therapy.

Preconditioned hyperbaric oxygenation protects the liver against ischemia-reperfusion injury in rats

Hyperbaric oxygen (HBO) therapy is an effective adjunct in treating ischemia-reperfusion (I/R) injury of brain, small intestine, testis, and crushing extremities. This study was designed to test the hypotheses that preconditioning the rats with HBO could protect the liver against subsequent I/R injury. Daily treatment with one-dose HBO (90 min, 2.5 ATA) was brought about for male Sprague Dawley rats for 1 to 3 days before an I/R injury of liver. Hepatic expression of heat-shock protein 70 (Hsp70), total concentration of glutathione (GSH), activity of catalase, superoxide dismutase (SOD), and serum AST and ALT were estimated before and after HBO, as well as after I/R injury. The results showed that activity of hepatic catalase was decreased by one dose, but not three doses, of HBO as compared with baseline data. However, hepatic Hsp70 expression fluctuated insignificantly. AST and ALT increase less in rats preconditioned with one-dose HBO as compared with those without HBO or with three-dose HBO. Our results showed preconditioning by one-dose HBO protects rat liver against subsequent ischemia-reperfusion injury.