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A bacterial barrier dressing for skin donor sites
52
Burns, 7. 52-56
Printedin Great Britain
A bacterial sites
barrier dressing for skin donor
Paul Nathan, Edward C. Robb and Bruce G. MacMillan The Shriners Burns Institute, Cincinnati Unit, and Departments Surgery, University of Cincinnati College of Medicine
Summary
Although most skin donor sites heal uneventfully, some surgically prepared open areas become contaminated and are converted to full-thickness wounds. Accordingly, a synthetic bacterial barrier dressing (Hydron Bum Bandage) applied as a spray or a preformed sheet was compared with fme mesh gauze application on skin donor sites in a series of 50 burned
children. Six of I9 control wounds demonstrated some bacterial contaminants. Only 2 out of 22 donor sites covered within 5 h after preparation contained any detectable bacterial contaminants. The Hydron bandage applied to skin donor sites adhered well, was easily removed at about I2 days and produced a barrier to bacterial contamination during the healing period. INTRODUCTION MOST skin donor sites heal primarily,
but some of these surgically prepared wounds become contaminated and are converted to fullthickness injuries. We therefore undertook an evaluation of a synthetic bacterial barrier dressing (Hydron@ Burn Bandage) applied to the donor site to protect the open area from microbial contamination. Previous laboratory studies (Nathan et al., 1974, 1975) have shown that the Hydron dressing excludes bacteria from an experimental burn. Extension of this work to a study in burned children also indicated that the barrier effect of Hydron was effective in a clinical situation (Nathan et al., 1976). The dressing was useful even on wounds containing bacteria at the time of its application. The present study offered an opportunity for further evaluation of the bacterial barrier effect of Hydron since the donor sites prepared by aseptic
of Physiology and
surgical techniques bial contaminants applied. MATERIALS
AND
were usually free of microwhen the dressing was
METHODS
The patients in this study were 50 children whose average age (+ the standard error of the mean) was 8.7 k 0.5 years. Both reconstructive and acutely burned patients were studied. The mean body surface area burned was 26.9 * 2.7 per cent. Donor sites were usually prepared by aseptic removal of skin from the anterior thighs or the backs of the patients. The donor tissue, obtained with a Brown dermatome, varied in thickness from 0.0 10 to 0.0 I8 in. Following removal of the skin, the donor sites were treated by one ofthe following procedures. 1. Fine mesh gauze was applied to the wounds and warm saline-soaked sponges were laid on the gauze. The sponges were held in position by a loose gauze bandage until bleeding from the area was controlled. 2. Coarse mesh gauze sponges were soaked in epinephrine (I : 100 000) diluted with saline and applied directly to the wounds. The epinephrine produced haemostasis of the donor site. The relatively dry donor sites were then covered with a two-component barrier dressing (Hydron) by spraying directly on the wound or on to the adherent fine mesh gauze. First, polyethylene glycol (PEG) was applied as a fine mist forced from its reservoir through a nozzle by compressed air or nitrogen gas (Fig. I). The gas flow was controlled by a reducing valve.
53
Nathan et al.: Dressing for Skin Donor Sites
Table 1. Average number of days (& s.e. mean) dressings remained on skin donor sites (Hydron preparations V. controls)
Gauze control Hydron dressing + gauze Hydron dressing Hydron sheet
No. of patients
Days on donor sites
18
11.8 t 3.4 12.1 & 4.6 8.8 f 4.3 107 c 5.3
19 22 9
Fig. I. Application of PEG and PHEMA by spraying directly on the skin donor site. The polymers are
applied alternately to build up several layers of each agent. Once the wound was judged to have a film of the PEG, a powder composed of poly (2-hydroxethyl methacrylate) (PHEMA) was sprayed on to the glycol layer. The powder was applied from a separate reservoir under pressure controlled by a special reducing valve since it requires less force to develop a spray than the viscous glycol. Application of the PHEMA powder was continued until the wound surface appeared slightly white and dry. Using these alternating spray procedures, two or three additional layers of PEG and PHEMA were applied. The composite film required 90 min to set up and form an intact sheet. The barrier dressing also was applied to the donor sites as a pre-formed preparation (Hydron Burn Bandage). The sheets were prepared in a germ-free incubator using sterile material. Sheets of Hydron were formed on a plastic surface by the alternate spray procedure. Once the film sets up to produce its fmal form, it is peeled from the plastic surface and sealed in several layers of wrapping paper. The packaged dressing is then removed from the germ-free incubator. Bacteriological monitoring of small pieces of the Hydron film was performed on representative samples obtained before application of the dressing to the wound surface. These proved to be uniformly free of contaminants. The pre-formed Hydron sheets were prepared prior to their application to the donor sites by spraying PEG on one side of the dressing to make the surface sticky. The sprayed side, applied to the wound, enhanced the dressing adherence. The dressed area extended 2-4 cm beyond the edges of the donor site on to normal skin to improve closure of the wound. In some cases the edges of the sheet were overlaid with
Tab/e //. Number of repairs required for Hydron dressings applied in three different ways Method of application Hydron on gauze Pre-formed Hydron sheet Hydron alone
No. of cases
No. of repairs
20
0
9
0
23
16
PEG and PHEMA spray to produce a smooth seal on the normal skin. Separation of the Hydron dressing generally occurred spontaneously as healing progressed. When it was necessary to remove the dressing mechanically, it was soaked with saline sponges for l-2 h and then carefully peeled from the wound. Bacteriological monitoring of the donor site was performed prior to application of the dressing and 4-6 days later. An area under the dressing was carefully exposed and a wet swab was firmly rolled over the test site. Each swab was extracted with IO ml of saline. Serial dilutions were individually plated on agar, cultured overnight and the number of colonies counted. Results were expressed as microbial count per swab in the original 10 ml of saline. RESULTS
Eighteen control patients were treated with fine mesh gauze alone on skin donor sites (Table I). These dressings remained in place for I I.8 k 3.4 days before the healing process combined with mechanical trimming of the
Fig. 2. The dressing is formed in Fig. 1 at 8 days afier application. It was removed 9 days after operation.
loose gauze uncovered the donor site. When Hydron was sprayed on the gauze, the combined preparation was retained on the wound for an average of 12.1 days in 19 patients. Spray application of Hydron on the donor site resulted in an earlier removal of the dressing, 8-8 + 4.3 days in 22 patients, compared with the subjects treated with gauze alone. The period of dressing application when pre-formed sheets of Hydron were used was 10.7 ~fr5.3 days in 9 patients. The study included both direct application of Hydron sheets and, in some subjects, application of the sheets over previously applied fine mesh gauze (see Table I). Table II lists the number of repairs required for Hydron to maintain an intact barrier subsequent to dressing application on skin donor sites. When the Hydron was sprayed on gauze, no repairs were needed in 20 cases. Pre-formed sheets applied directly to donor sites or over gauze required no repairs in 9 cases. However, 23 dressings applied directly to the wounds needed repairs in 16 cases. Two patients required 3 repairs each, 2 others 2 repairs each and 6 patients each needed 1 repair. Fig. 1 shows the Hydron dressing being applied directly on the skin donor site of a 13-year-old patient. The intact dressing is shown on the eighth day after application (Fig. 2). It was removed on the ninth day. Fig. 3 illustrates the application of the Hydron dressing to fme mesh gauze covering the skin donor site on a 14-year-old patient. The intact appearance of the covered area on the fourth day after application is illustrated in Fig. 4; and the healed donor site 340 days following the procedure is shown in Fig. 5. Application of a pre-formed Hydron sheet directly to a donor site in a 9-year-old patient is shown in Fig. 6. The side of the dressing to be
Fig. 3. Spray application of PHEMA gauze covering a skin donor site.
on fme mesh
Fig. 4. The dressing formed in Fig. 3 at 4 days after operation. The intact barrier dressing completely covers the wound. placed in contact with the wound had been sprayed with PEG to make that surface adherent. Figs. 7 and 8 show the dressing in place on the eighth day after application and the healed area (lower back) 202 days after operation. The data presented in Fig. 9 compare the distribution of the bacterial counts per swab test in unprotected control skin donor sites with the bacterial levels in the Hydron-covered areas when the wound sites were sampled 4-6 days after application. A small area under the dressing was exposed in each case to permit microbial sampling by the swab test. The control group treated with fine mesh gauze, demonstrated detectable contamination in 6 of 19 tests (open squares above the dotted line). When the interval of wound coverage with Hydron by spray application or pre-formed sheet was delayed 6-28 h after operation, bacteria were present on the skin donor sites in 10 of 15 cases. Ea,rly application of the barrier dressing O-5 h following preparation of the donor site resulted in only 2 of22 wounds with detectable contamination.
Nathan et al.: Dressing for Skin Donor Sites
Fig. 5. The donor site shown in Fig. 3 at 340 days after operation. Healing proceeds normally under the Hydron dressing.
Fig. 7. The pre-formed Hydron dressing 8 days after operation. This dressing remained in place for 16 days.
Fig. 6. Application to a skin donor site of a preformed sheet of the PHEMA-PEG dressing. Glycol was sprayed on the contact side of the dressing to improve adherence to the wound.
Fig. 8. The healed donor site 158 days after operation.
??
IO’ I
DISCUSSION
In this study, the synthetic barrier (Hydron) was applied in three ways over prepared skin donorsites after bleeding was controlled: by spraying the two components, liquid PEG and PHEMA powder, directly on to the wound; by spraying over a sheet of fme mesh gauze which was in direct contact with the wound; or by placing a preformed sheet of the synthetic dressing directly onto the donor site or over fme mesh gauze. When the dressing was sprayed on to fine mesh gauze or applied as a pre-formed sheet, no repairs were needed in 29 cases. However, the synthetic barrier required a total of 16 repairs in 23 tests when applied directly to the wound surface. Multiple repairs were required in 4 patients. In part, these may have resulted from a few uncooperative children. Most of the repairs were required because the dressings cracked
Hews Port-Operation
to Hydron Apphcpt~on
Fig. 9. Bacterial counts from swabs of control and Hydron-covered skin donor sites 4-6 days after application. All the symbols below the dotted line indicate tests with no detectable bacterial growth; those above the line show bacteria present on the test sites. 0, Hydron spray; A, Pre-formed Hydron sheet; X, Hydron spray on gauze; ?? , Hydron sheets on gauze; 0, control-fine mesh gauze.
56
during the first ‘I-14 h following Hydron application. It is not necessary to maintain the patient immobile following Hydron application, but the dressing cannot be flexed or stretched during this interval. The use of a gauze base may offer an internal support reducing the strain on the dressing so that it does not crack. Similarly, the pre-formed sheet having attained a solid form before it was used, withstood stresses better than the spray-formed dressing which required a setup period. The effectiveness of the microbial barrier function of the Hydron dressing is reported in Fig. 9: only 2 of 22 wounds contained detectable bacteria when the Hydron was applied O-5 h after operation compared with 6 of 19 contaminated wounds in the untreated controls. Although the results did not attain statistical significance, the trend in data supports the thesis that the Hydron dressing is an effective bacterial barrier. Moreover, a delay of 6-28 h in dressing application from the time of the donor site preparation resulted in demonstrated contamination in 10 of 15 cases. The trend of the data shows three times more infections in the controls than in the group with Hydron applied O-5 h following preparation of the donor site. It is worth noting that cracking of the dressing was not associated with wound contamination. The series in which the Hydron was applied 6-24 h after removal of donor skin contained only one example of a cracked dressing in the 10 cases with demonstrable bacteria in the wounds. The Hydron barrier dressing remained closely adherent to the donor sites throughout the period of observation. Small amounts of water on the wound surface could pass through the dressing as part of an exchange process for glycol. This water apparently evaporated from the dressing surface. The moderate restriction of water loss from the wounds probably accounted for the increased comfort and reduced pain reported from the donor sites covered with the synthetic dressing compared to the open wound sites treated with fme mesh gauze. Our experience indicates the dressing should be sprayed on while the patients are still anaesthetized. When application is delayed until
Burns Vol. ~/NO. 1
the end of the operative procedure, it is advantageous to keep the patient anaesthetized for an additional 30 min to allow partial formation of the solid state of the dressing. Other possible approaches are to apply the dressing as soon as haemostasis is achieved prior to the completion of the grafting procedures or, if available, apply the pre-formed sheet of Hydron. If it is necessary to delay the dressing preparation until after the patient is awake, it is best to use the pre-formed sheet since spraying the glycol is painful. The cooling and drying effect of the air or nitrogen gas flowing over the wound surface apparently results in a painful reaction. Observations in the present study demonstrate the effectiveness of the Hydron Burn Bandage as a synthetic microbial barrier for skin donor sites. Minimal repairs of the dressing were needed when the spray was applied over a fine mesh gauze dressing on the donor site. Pre-formed sheets of the synthetic dressing also form an effective microbial barrier. These sheets offer the advantage of rapid application. Healing proceeds normally under the synthetic barrier and both the standard gauze and the synthetic can be removed between 9 and 12 days after application. Patients consistently report reduced pain in the donor sites covered with the Hydron bandage for 1-2 days following the operation. Staff and subjects readily accept the dressing primarily because patient comfort is improved.
REFERENCES
Nathan P., MacMillan B. G. and Holder I. A. (1974) Effect of a synthetic dressing formed on a bum wound in rats: a comparison of allografts, collagen sheets and polyhydroxyethylmethacrylate in the control of wound infection. Appl. Microbial. 28, 465.
Nathan P., MacMillan B. G. and Holder I. A. (1975) In-situ production of a synthetic barrier dressing for bum wounds in rats. Infect. Immun. 12,257. _ Nathan P.. Law E. J.. MacMillan B. G. et al. (1976) A new bio’material for the control of infection in the bum wound. Trans. Am. Sot. Artif: Intern. Organs 22,30.
Paper accepted 1June 1979
Requestsfor reprints should be addressed to: Dr Paul Nathan, Shriners Bums Institute, 202 Goodman Street, Cincinnati, Ohio 45219. USA.
Burns, 7. 52-56
Printedin Great Britain
A bacterial sites
barrier dressing for skin donor
Paul Nathan, Edward C. Robb and Bruce G. MacMillan The Shriners Burns Institute, Cincinnati Unit, and Departments Surgery, University of Cincinnati College of Medicine
Summary
Although most skin donor sites heal uneventfully, some surgically prepared open areas become contaminated and are converted to full-thickness wounds. Accordingly, a synthetic bacterial barrier dressing (Hydron Bum Bandage) applied as a spray or a preformed sheet was compared with fme mesh gauze application on skin donor sites in a series of 50 burned
children. Six of I9 control wounds demonstrated some bacterial contaminants. Only 2 out of 22 donor sites covered within 5 h after preparation contained any detectable bacterial contaminants. The Hydron bandage applied to skin donor sites adhered well, was easily removed at about I2 days and produced a barrier to bacterial contamination during the healing period. INTRODUCTION MOST skin donor sites heal primarily,
but some of these surgically prepared wounds become contaminated and are converted to fullthickness injuries. We therefore undertook an evaluation of a synthetic bacterial barrier dressing (Hydron@ Burn Bandage) applied to the donor site to protect the open area from microbial contamination. Previous laboratory studies (Nathan et al., 1974, 1975) have shown that the Hydron dressing excludes bacteria from an experimental burn. Extension of this work to a study in burned children also indicated that the barrier effect of Hydron was effective in a clinical situation (Nathan et al., 1976). The dressing was useful even on wounds containing bacteria at the time of its application. The present study offered an opportunity for further evaluation of the bacterial barrier effect of Hydron since the donor sites prepared by aseptic
of Physiology and
surgical techniques bial contaminants applied. MATERIALS
AND
were usually free of microwhen the dressing was
METHODS
The patients in this study were 50 children whose average age (+ the standard error of the mean) was 8.7 k 0.5 years. Both reconstructive and acutely burned patients were studied. The mean body surface area burned was 26.9 * 2.7 per cent. Donor sites were usually prepared by aseptic removal of skin from the anterior thighs or the backs of the patients. The donor tissue, obtained with a Brown dermatome, varied in thickness from 0.0 10 to 0.0 I8 in. Following removal of the skin, the donor sites were treated by one ofthe following procedures. 1. Fine mesh gauze was applied to the wounds and warm saline-soaked sponges were laid on the gauze. The sponges were held in position by a loose gauze bandage until bleeding from the area was controlled. 2. Coarse mesh gauze sponges were soaked in epinephrine (I : 100 000) diluted with saline and applied directly to the wounds. The epinephrine produced haemostasis of the donor site. The relatively dry donor sites were then covered with a two-component barrier dressing (Hydron) by spraying directly on the wound or on to the adherent fine mesh gauze. First, polyethylene glycol (PEG) was applied as a fine mist forced from its reservoir through a nozzle by compressed air or nitrogen gas (Fig. I). The gas flow was controlled by a reducing valve.
53
Nathan et al.: Dressing for Skin Donor Sites
Table 1. Average number of days (& s.e. mean) dressings remained on skin donor sites (Hydron preparations V. controls)
Gauze control Hydron dressing + gauze Hydron dressing Hydron sheet
No. of patients
Days on donor sites
18
11.8 t 3.4 12.1 & 4.6 8.8 f 4.3 107 c 5.3
19 22 9
Fig. I. Application of PEG and PHEMA by spraying directly on the skin donor site. The polymers are
applied alternately to build up several layers of each agent. Once the wound was judged to have a film of the PEG, a powder composed of poly (2-hydroxethyl methacrylate) (PHEMA) was sprayed on to the glycol layer. The powder was applied from a separate reservoir under pressure controlled by a special reducing valve since it requires less force to develop a spray than the viscous glycol. Application of the PHEMA powder was continued until the wound surface appeared slightly white and dry. Using these alternating spray procedures, two or three additional layers of PEG and PHEMA were applied. The composite film required 90 min to set up and form an intact sheet. The barrier dressing also was applied to the donor sites as a pre-formed preparation (Hydron Burn Bandage). The sheets were prepared in a germ-free incubator using sterile material. Sheets of Hydron were formed on a plastic surface by the alternate spray procedure. Once the film sets up to produce its fmal form, it is peeled from the plastic surface and sealed in several layers of wrapping paper. The packaged dressing is then removed from the germ-free incubator. Bacteriological monitoring of small pieces of the Hydron film was performed on representative samples obtained before application of the dressing to the wound surface. These proved to be uniformly free of contaminants. The pre-formed Hydron sheets were prepared prior to their application to the donor sites by spraying PEG on one side of the dressing to make the surface sticky. The sprayed side, applied to the wound, enhanced the dressing adherence. The dressed area extended 2-4 cm beyond the edges of the donor site on to normal skin to improve closure of the wound. In some cases the edges of the sheet were overlaid with
Tab/e //. Number of repairs required for Hydron dressings applied in three different ways Method of application Hydron on gauze Pre-formed Hydron sheet Hydron alone
No. of cases
No. of repairs
20
0
9
0
23
16
PEG and PHEMA spray to produce a smooth seal on the normal skin. Separation of the Hydron dressing generally occurred spontaneously as healing progressed. When it was necessary to remove the dressing mechanically, it was soaked with saline sponges for l-2 h and then carefully peeled from the wound. Bacteriological monitoring of the donor site was performed prior to application of the dressing and 4-6 days later. An area under the dressing was carefully exposed and a wet swab was firmly rolled over the test site. Each swab was extracted with IO ml of saline. Serial dilutions were individually plated on agar, cultured overnight and the number of colonies counted. Results were expressed as microbial count per swab in the original 10 ml of saline. RESULTS
Eighteen control patients were treated with fine mesh gauze alone on skin donor sites (Table I). These dressings remained in place for I I.8 k 3.4 days before the healing process combined with mechanical trimming of the
Fig. 2. The dressing is formed in Fig. 1 at 8 days afier application. It was removed 9 days after operation.
loose gauze uncovered the donor site. When Hydron was sprayed on the gauze, the combined preparation was retained on the wound for an average of 12.1 days in 19 patients. Spray application of Hydron on the donor site resulted in an earlier removal of the dressing, 8-8 + 4.3 days in 22 patients, compared with the subjects treated with gauze alone. The period of dressing application when pre-formed sheets of Hydron were used was 10.7 ~fr5.3 days in 9 patients. The study included both direct application of Hydron sheets and, in some subjects, application of the sheets over previously applied fine mesh gauze (see Table I). Table II lists the number of repairs required for Hydron to maintain an intact barrier subsequent to dressing application on skin donor sites. When the Hydron was sprayed on gauze, no repairs were needed in 20 cases. Pre-formed sheets applied directly to donor sites or over gauze required no repairs in 9 cases. However, 23 dressings applied directly to the wounds needed repairs in 16 cases. Two patients required 3 repairs each, 2 others 2 repairs each and 6 patients each needed 1 repair. Fig. 1 shows the Hydron dressing being applied directly on the skin donor site of a 13-year-old patient. The intact dressing is shown on the eighth day after application (Fig. 2). It was removed on the ninth day. Fig. 3 illustrates the application of the Hydron dressing to fme mesh gauze covering the skin donor site on a 14-year-old patient. The intact appearance of the covered area on the fourth day after application is illustrated in Fig. 4; and the healed donor site 340 days following the procedure is shown in Fig. 5. Application of a pre-formed Hydron sheet directly to a donor site in a 9-year-old patient is shown in Fig. 6. The side of the dressing to be
Fig. 3. Spray application of PHEMA gauze covering a skin donor site.
on fme mesh
Fig. 4. The dressing formed in Fig. 3 at 4 days after operation. The intact barrier dressing completely covers the wound. placed in contact with the wound had been sprayed with PEG to make that surface adherent. Figs. 7 and 8 show the dressing in place on the eighth day after application and the healed area (lower back) 202 days after operation. The data presented in Fig. 9 compare the distribution of the bacterial counts per swab test in unprotected control skin donor sites with the bacterial levels in the Hydron-covered areas when the wound sites were sampled 4-6 days after application. A small area under the dressing was exposed in each case to permit microbial sampling by the swab test. The control group treated with fine mesh gauze, demonstrated detectable contamination in 6 of 19 tests (open squares above the dotted line). When the interval of wound coverage with Hydron by spray application or pre-formed sheet was delayed 6-28 h after operation, bacteria were present on the skin donor sites in 10 of 15 cases. Ea,rly application of the barrier dressing O-5 h following preparation of the donor site resulted in only 2 of22 wounds with detectable contamination.
Nathan et al.: Dressing for Skin Donor Sites
Fig. 5. The donor site shown in Fig. 3 at 340 days after operation. Healing proceeds normally under the Hydron dressing.
Fig. 7. The pre-formed Hydron dressing 8 days after operation. This dressing remained in place for 16 days.
Fig. 6. Application to a skin donor site of a preformed sheet of the PHEMA-PEG dressing. Glycol was sprayed on the contact side of the dressing to improve adherence to the wound.
Fig. 8. The healed donor site 158 days after operation.
??
IO’ I
DISCUSSION
In this study, the synthetic barrier (Hydron) was applied in three ways over prepared skin donorsites after bleeding was controlled: by spraying the two components, liquid PEG and PHEMA powder, directly on to the wound; by spraying over a sheet of fme mesh gauze which was in direct contact with the wound; or by placing a preformed sheet of the synthetic dressing directly onto the donor site or over fme mesh gauze. When the dressing was sprayed on to fine mesh gauze or applied as a pre-formed sheet, no repairs were needed in 29 cases. However, the synthetic barrier required a total of 16 repairs in 23 tests when applied directly to the wound surface. Multiple repairs were required in 4 patients. In part, these may have resulted from a few uncooperative children. Most of the repairs were required because the dressings cracked
Hews Port-Operation
to Hydron Apphcpt~on
Fig. 9. Bacterial counts from swabs of control and Hydron-covered skin donor sites 4-6 days after application. All the symbols below the dotted line indicate tests with no detectable bacterial growth; those above the line show bacteria present on the test sites. 0, Hydron spray; A, Pre-formed Hydron sheet; X, Hydron spray on gauze; ?? , Hydron sheets on gauze; 0, control-fine mesh gauze.
56
during the first ‘I-14 h following Hydron application. It is not necessary to maintain the patient immobile following Hydron application, but the dressing cannot be flexed or stretched during this interval. The use of a gauze base may offer an internal support reducing the strain on the dressing so that it does not crack. Similarly, the pre-formed sheet having attained a solid form before it was used, withstood stresses better than the spray-formed dressing which required a setup period. The effectiveness of the microbial barrier function of the Hydron dressing is reported in Fig. 9: only 2 of 22 wounds contained detectable bacteria when the Hydron was applied O-5 h after operation compared with 6 of 19 contaminated wounds in the untreated controls. Although the results did not attain statistical significance, the trend in data supports the thesis that the Hydron dressing is an effective bacterial barrier. Moreover, a delay of 6-28 h in dressing application from the time of the donor site preparation resulted in demonstrated contamination in 10 of 15 cases. The trend of the data shows three times more infections in the controls than in the group with Hydron applied O-5 h following preparation of the donor site. It is worth noting that cracking of the dressing was not associated with wound contamination. The series in which the Hydron was applied 6-24 h after removal of donor skin contained only one example of a cracked dressing in the 10 cases with demonstrable bacteria in the wounds. The Hydron barrier dressing remained closely adherent to the donor sites throughout the period of observation. Small amounts of water on the wound surface could pass through the dressing as part of an exchange process for glycol. This water apparently evaporated from the dressing surface. The moderate restriction of water loss from the wounds probably accounted for the increased comfort and reduced pain reported from the donor sites covered with the synthetic dressing compared to the open wound sites treated with fme mesh gauze. Our experience indicates the dressing should be sprayed on while the patients are still anaesthetized. When application is delayed until
Burns Vol. ~/NO. 1
the end of the operative procedure, it is advantageous to keep the patient anaesthetized for an additional 30 min to allow partial formation of the solid state of the dressing. Other possible approaches are to apply the dressing as soon as haemostasis is achieved prior to the completion of the grafting procedures or, if available, apply the pre-formed sheet of Hydron. If it is necessary to delay the dressing preparation until after the patient is awake, it is best to use the pre-formed sheet since spraying the glycol is painful. The cooling and drying effect of the air or nitrogen gas flowing over the wound surface apparently results in a painful reaction. Observations in the present study demonstrate the effectiveness of the Hydron Burn Bandage as a synthetic microbial barrier for skin donor sites. Minimal repairs of the dressing were needed when the spray was applied over a fine mesh gauze dressing on the donor site. Pre-formed sheets of the synthetic dressing also form an effective microbial barrier. These sheets offer the advantage of rapid application. Healing proceeds normally under the synthetic barrier and both the standard gauze and the synthetic can be removed between 9 and 12 days after application. Patients consistently report reduced pain in the donor sites covered with the Hydron bandage for 1-2 days following the operation. Staff and subjects readily accept the dressing primarily because patient comfort is improved.
REFERENCES
Nathan P., MacMillan B. G. and Holder I. A. (1974) Effect of a synthetic dressing formed on a bum wound in rats: a comparison of allografts, collagen sheets and polyhydroxyethylmethacrylate in the control of wound infection. Appl. Microbial. 28, 465.
Nathan P., MacMillan B. G. and Holder I. A. (1975) In-situ production of a synthetic barrier dressing for bum wounds in rats. Infect. Immun. 12,257. _ Nathan P.. Law E. J.. MacMillan B. G. et al. (1976) A new bio’material for the control of infection in the bum wound. Trans. Am. Sot. Artif: Intern. Organs 22,30.
Paper accepted 1June 1979
Requestsfor reprints should be addressed to: Dr Paul Nathan, Shriners Bums Institute, 202 Goodman Street, Cincinnati, Ohio 45219. USA.