Sympathetically induced paradoxical increases of the cutaneous blood flow in chronically inflamed rats

Enhanced healing of diabetic foot ulcers using local heat and electrical stimulation for 30 min three times per week

BACKGROUND

Electrical stimulation (ES) with heating is effective in healing chronic wounds. However, it this effect due to ES alone or both heating and ES? The aim of the present study was to deduce the individual roles of heat and ES in the healing of chronic wounds.

METHODS

The study was performed on 20 patients (mean age 48.4 ± 14.6 years) with non-healing diabetic foot ulcers (mean duration 38.9 ± 23.7 months) who received local dry heat (37°C; n = 10) or local dry heat + ES (n = 10) three times a week for 4 weeks. Patients were given ES using biphasic sine wave stimulation (30 Hz, pulse width 250 μs, current approximately 20 mA).

RESULTS

  Skin blood flow in and around the wound was measured with a laser Doppler flow imager. In the ES + heat group, the average wound area and volume decreased significantly by 68.4 ± 28.6% and 69.3 ± 27.1%, respectively (both P < 0.05), over the 1-month period. During the average session, blood flow increased to 102.3 ± 25.3% with local heat and to 152.3 ± 23.4% with ES + heat. In the group receiving treatment with local heat only, wounds that had not healed for at least 2 months showed 30.1 ± 22.6% healing (i.e. a decrease in wound area) after 1 month. Although this level of healing was significant, it was less than that observed in the ES + heat group (P<0.05).

CONCLUSIONS

  Local dry heat and ES work well together to heal chronic diabetic foot wounds; however, local heat would appear to be a relevant part of this therapy because ES alone has produced little healing in previous studies.

The combined effect of a three-channel electrode delivery system with local heat on the healing of chronic wounds

BACKGROUND

Historically, electrical stimulation (ES) has been used as a treatment for wound care. However, some studies show wounds healing with ES, whereas others do not. Part of the difficulty can be resolved by using heat to help dilate blood vessels, but an inherent problem with ES is uneven currents across the wound due to the use of only two electrodes. Therefore, we designed and tested a multi-electrode ES device in combination with local warming of the wound in non-healing chronic ulcers.

STUDY DESIGN

Eighteen subjects (mean +/- SD age, 35.7 +/- 21.3 years) with chronic ulcers (no healing for 26.1 +/- 24.6 months) received ES treatment three times a week for 4 weeks. A heat lamp was used before and during ES to keep the wound and area surrounding the wound warm (37 degrees C). ES was applied for 30 min with biphasic sine wave stimulation at a frequency of 30 Hz, pulse width of 250 micros, and current of about 20 mA. Skin blood flow (BF) in and around the wound was measured with a laser Doppler imager. Wound size was measured prior to each treatment.

RESULTS

Over the 1-month period, the mean wound area significantly decreased by 43.4 +/- 44.5% (P < 0.05), and wound volume decreased by 57.0 +/- 27.9% (P < 0.05). Skin BF significantly increased after application of ES and local heat (P < 0.05). The skin BF response decreased as time progressed and the wound healed.

CONCLUSIONS

Thus, in this pilot study, application of a three-channel ES system in combination with local heat is effective in the healing of non-healing chronic wounds. Future studies should examine a larger population with variables such as treatment duration, number of days, or length of treatment to optimize the effect of ES on healing of non-healing chronic wounds.

A re-evaluation of modelling of the current flow between electrodes: consideration of blood flow and wounds

Electrical stimulation has been used for exercise, healing wounds, relieving pain, and strengthening muscle. The assumption is that current will flow predictably between electrodes and, therefore, there will be predictability in the clinical response to electrical stimulation. This may not be the case. The present investigation shows that considerable channelling of current occurs when the skin is heated or when there is a wound between the electrodes. By studying current movement in nutrient agar (a homogenous medium), blood agar and layered blood and nutrient agar to simulate areas of increased blood flow, it was found that areas of high or low resistance, especially in the surface layer, caused significant current movement toward (low resistance area) or away (high resistance area) from those areas. When a resister model was used to measure dispersion characteristics of current in a three-dimensional array, it was shown that if even a single resister value was lowered by 20% in the upper layer, current sinking occurred in all three layers of the array. The results seem to imply that where the tissue is non homogeneous due to injury or inflammation, electrode design or current delivery systems need to be modified appropriately to have the intended effect of the electrical stimulation.

Effects of a 2-, 3- and 4-electrode stimulator design on current dispersion on the surface and into the limb during electrical stimulation in controls and patients with wounds

Electrical stimulation is a widely used modality in the field of physical therapy and exercise physiology. The most common method for the application of electrical stimulation is a two-electrode system where one electrode is the source and the other is a reference. However, recent studies report that a more effective delivery system can be achieved if more than two electrodes are used. In the present investigation, the circuitry to deliver electrical stimulation through a 2-, 3- or 4-electrode delivery system was designed. The system was evaluated by its ability to deliver current on the surface of the skin as well as deep into the quadriceps muscle in six control subjects and in and around wounds in six other subjects. The results of the experiments showed that much better depth of penetration was achieved in a 4-electrode system (one electrode was on the opposite side of the limb and three electrodes were on top of the limb) than in either a 2- or a 3-electrode delivery system. In non-wounded skin, given the same current from the stimulator, the current in the quadriceps muscle was found to be double with a 4-electrode versus a 2-electrode system. In wounds, this same finding was seen. Here, blood flow, an indicator of the effectiveness of electrical stimulation in wounds, was three times higher if a multi-channel stimulator was used versus a 2-channel stimulator. Thus a multi-channel electrical stimulation system is more effective than a 2-electrode system.

The influence of local versus global heat on the healing of chronic wounds in patients with diabetes

BACKGROUND

In a previous study, it was shown that placing a subject with chronic diabetic ulcers in a warm room prior to the use of electrical stimulation dramatically increased the healing rate. However, global heating is impractical in many therapeutic environments, and therefore in the present investigation the effect of global heat versus using a local heat source to warm the wound was investigated.

METHODS

Twenty-nine male and female subjects participated in a series of experiments to determine the healing associated with electrical stimulation with the application of local heat through a heat lamp compared to global heating of the subject in a warm room. Treatment consisted of biphasic electrical stimulation at currents at 20 mA for 30 min three times per week for 4 weeks in either a 32 degrees C room or, with the application of local heat, to raise skin temperature to 37 degrees C. Skin blood flow was measured by a laser Doppler imager.

RESULTS

Blood flow increased with either local or global heating. During electrical stimulation, blood flow almost doubled on the outside and on the edge of the wound with a smaller increase in the center of the wound. However, the largest increase in blood flow was in the subjects exposed to global heating. Further, healing rates, while insignificant for subjects who did not receive electrical stimulation, showed 74.5 +/- 23.4% healing with global heat and 55.3 +/- 31.1% healing with local heat in 1 month; controls actually had a worsening of their wounds.

CONCLUSIONS

The best healing modality was global heat. However, there was still a significant advantage in healing with local heat.

Effects of adrenoceptor antagonists on the cutaneous blood flow increase response to sympathetic nerve stimulation in rats with persistent inflammation

There is some evidence that the sympathetic nervous system plays a role in the development and/or maintenance of painful states, and that sympathetic nervous function is altered in these conditions. Our previous experiments showed that electrical stimulation of the lumbar sympathetic trunk (sympathetic stimulation: SS), which normally induces a decrease in blood flow (BF) of plantar skin, induced its BF increase in about 50% of adjuvant-inflamed rats. To investigate the mechanism of this BF-increase response, we examined whether noradrenaline (NA) plays any role in this changed response to SS, and which receptor subtype is involved. We measured paw cutaneous BF response with a laser Doppler flowmeter in rats chronically inflamed with complete Freund's adjuvant. SS induced the BF-increase response in 50-67% of measured sites. Close-arterially injected NA induced the BF-increase response at dosages between 10-100 ng/kg only at the sites with the BF-increase response to SS. The BF-increase and -decrease responses to NA was significantly reduced after the close-arterial injection of either alpha1- or alpha2-adrenoceptor antagonists (p lt; 0.05, respectively). In contrast, although the BF-decrease responses to SS were significantly reduced by administration of alpha1- and alpha2-adrenoceptor antagonist, BF-increase response was reduced only by alpha1-adrenoceptor antagonist, and that only at a higher dose. In addition, the beta-adrenoceptor antagonist had no effects on both responses. These results suggest that the BF-increase response to SS involves, additionally to NA, a non-adrenergic mechanism.