Hyperbaric oxygen treatment after rat peroneal nerve transection and entubulation

EFFECT OF HYPERBARIC OXYGEN THERAPY ON NERVE REGENERATION IN RATS

Objective:

To evaluate histological changes in peripheral nerves of rats after sciatic nerve neurorrhaphy, according to the time of exposure to hyperbaric oxygen chamber treatment.

Methods:

Twenty-five Wistar rats were divided into 5 groups according to the amount of exposure to hyperbaric oxygen chamber treatment. Group 1 was the control and there was no use of hyperbaric oxygen chamber; group 2 received one week of therapy; group 3, two weeks; group 4, three weeks; and group 5, four weeks. After the fourth postoperative week, the animals were submitted to euthanasia and a sciatic nerve sample sent for histological analysis. Axons proximal and distal to the neurorrhaphy were counted with axonal regeneration index measurement.

Results:

We observed that the number of axons distal to neurorrhaphy increases with the amount of hyperbaric oxygen chamber exposure, the results were more expressive from the third week of treatment. However, the statistical analysis found no significant difference between the groups.

Conclusion:

The descriptive analysis suggests benefit of using hyperbaric oxygen chamber directly proportional to the time of therapy. The study, however, did not present statistically relevant results, probably due to the reduced sample size. Subsequent studies with more significant sampling would be of great value. Level of Evidence II, Prospective Comparative Study.

A review on the neuroprotective effects of hyperbaric oxygen therapy

Hyperbaric oxygen therapy, intermittent breathing of 100% oxygen at a pressure upper than sea level, has been shown to be some of the neuroprotective effects and used therapeutically in a wide range of neurological disorders. This review summarizes current knowledge about the neuroprotective effects of hyperbaric oxygen therapy with their molecular mechanisms in different models of neurological disorders.

Effects of ozone therapy on facial nerve regeneration

Introduction

Ozone may promote moderate oxidative stress, which increases antioxidant endogenous systems. There are a number of antioxidants that have been investigated therapeutically for improving peripheral nerve regeneration. However, no previous studies have reported the effect of ozone therapy on facial nerve regeneration.

Objective

We aimed to evaluate the effect of ozone therapy on facial nerve regeneration.

Methods

Fourteen Wistar albino rats were randomly divided into two groups with experimental nerve crush injuries: a control group, which received saline treatment post-crush, and an experimental group, which received ozone treatment. All animals underwent surgery in which the left facial nerve was exposed and crushed. Treatment with saline or ozone began on the day of the nerve crush. Left facial nerve stimulation thresholds were measured before crush, immediately after crush, and after 30 days. After measuring nerve stimulation thresholds at 30 days post-injury, the crushed facial nerve was excised. All specimens were studied using light and electron microscopy.

Results

Post-crushing, the ozone-treated group had lower stimulation thresholds than the saline group. Although this did not achieve statistical significance, it is indicative of greater functional improvement in the ozone group. Significant differences were found in vascular congestion, macrovacuolization, and myelin thickness between the ozone and control groups. Significant differences were also found in axonal degeneration and myelin ultrastructure between the two groups.

Conclusion

We found that ozone therapy exerted beneficial effect on the regeneration of crushed facial nerves in rats.

Hyperbaric oxygen versus steroid in facial nerve injury: an experimental animal study

OBJECTIVE

The aim of this experimental study was to evaluate the effects of hyperbaric oxygen, methylprednisolone and combined hyperbaric oxygen-methylprednisolone treatments on traumatic facial nerve regeneration in rats.

SUBJECTS AND METHODS

After exposure to facial nerve injury, four groups of rats were created with five subjects in each group: Group 1 (hyperbaric oxygen), group 2 (control), group 3 (combined hyperbaric oxygen-methylprednisolone), group 4 (methylprednisolone). Facial nerve specimens from sacrificed animals were examined for axonal degeneration, vascular congestion, macro vacuolization, axon diameter and thickness of myelin sheath.

RESULTS

There were significant differences with regard to axonal degeneration, vascular congestion and axon diameter between group 3 and the control group. In addition to lower axonal degeneration and vascular congestion, a larger diameter of axons was observed in group 3. There were significant differences with regard to vascular congestion and axon diameter between group 4 and the control group. We observed thicker myelin and lower axonal degeneration in group 3 compared with group 4.

CONCLUSION

The combination therapy with hyperbaric oxygen and methylprednisolone had an additive beneficial effect on regeneration of the facial nerve and may provide better treatment outcomes than methylprednisolone or hyperbaric oxygen therapy alone.

Neurotrophic effects of perfluorocarbon emulsion gel: a pilot study

Background

Positive neurotrophic effects of hyperbaric oxygen treatment may be more easily achieved by applying a Perflourocarbon (PFC) emulsion gel to the repair site. PFCs are halogen substituted carbon oils with unique oxygen transport potentials that are capable of increasing oxygen availability in local tissues. The purpose of this study was to determine if the application of a PFC emulsion to a repaired nerve would improve recovery.

Materials and methods

The left tibial nerve of 21 immature female Sprague-Dawley rats was transected, immediately repaired, and then circumferentially coated with PFC gel (Group A, n = 7), PFC-less gel (Group B, n = 7), or nothing (suture only, Group C, n = 7). At eight weeks post surgery, electrophysiological testing and histological and morphological analysis was performed.

Results

No statistically significant differences between experimental groups were found for muscle size and weight, axon counts, or nerve conduction velocity. Group A had a significantly smaller G-ratio than Groups B and C (p < .0001).

Conclusion

Overall results do not indicate a functional benefit associated with application of a PFC emulsion gel to rodent tibial nerve repairs. A positive effect on myelination was seen.

Hyperbaric oxygenation in peripheral nerve repair and regeneration

Peripheral nerves are essential connections between the central nervous system and muscles, autonomic structures and sensory organs. Their injury is one of the major causes for severe and longstanding impairment in limb function. Acute peripheral nerve lesion has an important inflammatory component and is considered as ischemia-reperfusion (IR) injury. Surgical repair has been the standard of care in peripheral nerve lesion. It has reached optimal technical development but the end results still remain unpredictable and complete functional recovery is rare. Nevertheless, nerve repair is not primarily a mechanical problem and microsurgery is not the only key to success. Lately, there have been efforts to develop alternatives to nerve graft. Work has been carried out in basal lamina scaffolds, biologic and non-biologic structures in combination with neurotrophic factors and/or Schwann cells, tissues, immunosuppressive agents, growth factors, cell transplantation, principles of artificial sensory function, gene technology, gangliosides, implantation of microchips, hormones, electromagnetic fields and hyperbaric oxygenation (HBO). HBO appears to be a beneficial adjunctive treatment for surgical repair in the acute peripheral nerve lesion, when used at lower pressures and in a timely fashion (<6 hours).

Effect of hyperbaric oxygen therapy on nerve regeneration in early diabetes

Nerve regeneration in diabetes is essential for reversal of neuropathy as well as the recovery of nerves from injury due to acute nerve compression and entrapment. Endoneural hypoxia due to hyperglycemia-induced blood flow reductions is observed early in the course of diabetes, and the resultant ischemia plays a role in the diminished neural regeneration. Hyperbaric oxygen therapy is capable of producing tissue hyperoxia by raising oxygen tensions in ischemic tissues, and was shown to be beneficial in the reversal of experimental ischemic neuropathy. In this study, an experimental diabetes model was used to evaluate the functional and histomorphological effects of hyperbaric oxygen therapy on early diabetic nerve regeneration. Our results indicate that there is significant histomorphological impairment of nerve regeneration, even in very early stages of diabetes. However, no beneficial effects of hyperbaric oxygen therapy could be demonstrated at this stage.

The effect of hyperbaric oxygen treatment on early regeneration of sensory axons after nerve crush in the rat

Abstract The effect of hyperbaric oxygen treatment (HBO) on sensory axon regeneration was examined in the rat. The sciatic nerve was crushed in both legs. In addition, the distal stump of the sural nerve on one side was made acellular and its blood perfusion was compromised by freezing and thawing. Two experimental groups received hyperbaric exposures (2.5 ATA) to either compressed air (pO2 = 0.5 ATA) or 100% oxygen (pO2 = 2.5 ATA) 90 minutes per day for 6 days. Sensory axon regeneration in the sural nerve was thereafter assessed by the nerve pinch test and immunohistochemical reaction to neurofilament. HBO treatment increased the distances reached by the fastest regenerating sensory axons by about 15% in the distal nerve segments with preserved and with compromised blood perfusion. There was no significant difference between the rats treated with different oxygen tensions. The total number of regenerated axons in the distal sural nerve segments after a simple crush injury was not affected, whereas in the nerve segments with compromised blood perfusion treated by the higher pO2, the axon number was about 30% lower than that in the control group. It is concluded that the beneficial effect of HBO on sensory axon regeneration is not dose-dependent between 0.5 and 2.5 ATA pO2. Although the exposure to 2.5 ATA of pO2 moderately enhanced early regeneration of the fastest sensory axons, it decreased the number of regenerating axons in the injured nerves with compromised blood perfusion of the distal nerve stump.

Functional evaluation after rat sciatic nerve injury followed by hyperbaric oxygen treatment

Previous experimental studies have shown positive effects of hyperbaric oxygen treatment in the early regeneration phase in the first few days following a nerve injury. In this study, functional effects of hyperbaric oxygen treatment were studied in 2 series of rats after an injury to the sciatic nerve - a standardized crush injury and nerve transection and repair, respectively. Postoperatively the animals were treated with 100% oxygen at 2.5 atmospheres absolute pressure for 90 minutes and the treatment was employed twice daily for 7 days. The animals were evaluated with walking track analysis up to twice weekly. The experiments were terminated after 90 days when the tetanic force was measured in the tibial anterior and gastrocnemius muscles. No statistically significant differences were found in either of these tests. It is concluded that hyperbaric oxygen treatment, given in accordance with clinical protocols used in limb crush injuries and other peripheral conditions, was not effective in the restoration of gait or the muscular strength after 90 days in rats after these nerve injuries. This study does not support nerve crush injury or nerve transection and repair as indications for hyperbaric oxygen treatment.

A functional model system of an hypoxic nerve injury and its evaluation

OBJECTIVES/HYPOTHESIS

Develop an hypoxic peripheral nerve injury model with a controlled injury type and two types of clinically relevant physiological measurements of function during and after recovery. The model, controlling for injury and measurement variables, would have predictable outcomes in function. The functional model could test potential therapeutic interventions with greater sensitivity.

STUDY DESIGN

Twenty-one rats were used in preliminary studies evaluating peroneal nerve injury types and functional model evaluation. Forty-eight rats were used in a controlled and blinded evaluation of the injury model followed by treatment with hyperbaric oxygen (HBO) as a potential therapeutic intervention and evaluated with functional models.

METHODS

Preliminary studies compared nerve injuries: epineurectomy, epineurectomy with crush and transection with autograft for rate of return of function and final extent of return of function. The gait analysis model was also evaluated and modified to decrease variability. The final study evaluated peroneal epineurectomy and nerve crush injury with serial gait analysis during recovery, final elicited maximum force measurements, and histological analysis. Half of the animals were treated with HBO during recovery (ANOVA or regression statistical analysis were used to determine group differences.).

RESULTS

Preliminary studies suggested that the peroneal nerve injury model of an epineurectomy with crush of specified length and a modification of the gait analysis model would yield a useful and predictable injury outcome. The final study resulted in predicted and consistent injury outcomes. In the HBO treatment group, a 12% improvement in function 5 days after HBO treatment was demonstrated (P < .03), but no long-term or histological benefit was seen.

CONCLUSION

A reliable hypoxic nerve injury model has been developed and tested utilizing two functional methods as the primary outcome variables.

Effect of hyperbaric oxygen on the regeneration of experimental crush injuries of nerves

Hyperbaric oxygen has been successfully used on treatment of acute ischemic injuries involving soft tissues and chronic injuries. In nerve crush injuries, the mechanisms involved are very similar to those found in ischemic injuries. Consequently, it is logical to hypothesize that hyperbaric oxygen should improve nerve repair, which is a critical step on functional recovery. In the present study, we created standard nerve crush injuries on sciatic nerves of rats, which underwent treatment with hyperbaric oxygen. Results were assessed by functional evaluation using walking-track analysis. The functional recovery indexes observed did not differ from control group. We concluded that hyperbaric oxygen therapy, in the schedule used, had no influence on functional recovery after nerve crush injuries.