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Effects of washing acid injuries to the skin with water: an experimental study using rats
030s4179(95)00027-5
K. Yano’, K. Hosokawal,
M. Kakibuchil,
H. H&sax
and Y. Hata’
‘Department of Dermatology, Division of Plastic Surgery, Osaka University Plastic Surgery, Kagawa Medical School, Japan
A skin acid injury model has been constructed using SD rats and 1 N HCl. The changes overtime,with particularattentionto subcutaneous tissue pH, were recorded and included a comparative study of the effect of washingwith wafer at I,3 and 1Omin after injury, on subcutaneous fissue PH. Affer inflictingan acidinjury, the subcutaneous tissuepH of control animals reached ifs minimum value at the seventh minute, and had not recouered fu the pre-experimenfat level by the 60th minute. In the group of rats which was washed ut I min, fhe pH did nof drop below 7.5, it remained virtually unchanged. In the group washed at 3 min, the pH declined slightly, but subsequent to washing, the pH increasedgradually. In thegroup washed at 10 min, the changes in pH were almost the same as those in fhe untreated group. These results indicated that if washing was carriedout before the subcutaneous tissue pH level reached a minimum value, any remaining acid on the skin surface could be washed away, effectively suppressing fhe subsequent fall in pH.
Burns, Vol. 21. No. 7, 500-502,
1995
Introduction Chemical injuries occur when chemicalscome into direct contact with the skin or mucous membranes. We have previously reported it is markedly effective for skin alkaline injuries to wash them with water as soon as possible before the pH value of the subcutaneoustissue reachesits peak’,‘. In fhis study, using a similar experimental model, acid injuries were investigated and the therapeutic effects of washing were assessed.
Materials
School of Medicine and ZDepartment of
IN-HCl to the skin over a circular area with a diameter of 2 cm, directly above the tip of the electrode. The subcutaneous pH was recorded at I-min intervals, up to 60 min following infliction of the injury. The rats used in the experiment were divided into four groups (n = 5). Group 1 remaineduntreated, while Groups 2, 3 and 4 received continuous washing with 500ml of distilled water (33 ml/min), starting at I, 3 and 10min postinjury respectively. The pH values were determined continuously. Student’s f-test was used to assessdifferencesbetween the groups. After IO days, the injured skin was biopsied for histological studies.
Results Periodic changes in the subcutaneous tissue pH Group 1 The pre-experimental subcutaneoustissuepH was 7.71 f 0.06. After injury, the pH gradually declined and at 7min reached a minimum at pH 7.22 f 0.08. Thereafter, it gradually increased, and at 60min the pH was 7.48 f 0.01 (Figure Il. Group 2 After initiating washing, the decline in the pH ceased,During the entire experiment, the pH did not fall below 7.5 and remainedvirtually unchanged. A significant difference (PC 0.01) in pH, when compared with the untreated group, was found after the second minute. PH
and methods
The experimental animalsusedwere 20 Sprague-Dawley rats, each weighing approximately 300g. After inducing general anaesthesiaby the intraperitoneal injection of nembutal, the rats were restrained in the dorsal position, and their abdomens were shaved. A small incision was made in the upper abdominal region, and a needle-shaped antimony pH microelectrode (diameter I mm, length 20 mm, responsetime 10-15 s, Chemical Kiki Co., Tokyo. Japan) was inserted immediately under the panniculus carnosus. A comparative electrode was affixed with double-coated tape to the opposite side of the abdomen. The acid injury was induced by applying 0.05 ml of
71 1
.70 1
0
2
4
6
8
10
20
30
40
50
60 Time :mwj
Figure 1. Periodic changesin the subcutaneous tissue pH. Results given are meani s.e., n= 5. O-0, Washing from I min; R-W, washing from 3 min; A-A, flushing from IOmin. ‘PCO.05; “P-CO.01.
501
Yano et al.: Washing acid injuries to the skin with water
Figure 2. Histological pictures on day 10. a, Group I: all layers of the epidermis, dermis and the panniculus camosus had become necrotic. b, Group 2: from the epidermis to the superficial muscle layer, the tissue was preserved to an almost normal extent. c, Group 3: although the epidermis and dermis, including the dermal adnexae, had become necrotic, the panniculus camosus was almost completely preserved. d, Group 4: necrosis had extended into the panniculus camosus.
Group 3 Until initiating washing, the pH declined slightly. Subsequent to washing, however, the pH increased gradually, until at 60min it had returned to 7.52 f 0.02. A significant difference (P-C 0.05) in pH when compared with the untreated group was detectable between the eighth min and the twenty-fifth minute. Group 4 The changesin pH were virtually the sameas those measuredin the untreated group. During the entire experiment, no significant differences in pH were detectable when compared with the untreated group. Histological assessment’of the skin A histological assessmentof the skin on day 10 after the acid injury, used the following tissue-damage scoring system to evaluate the extent of injury: 1. Almost normal. 2. Damage to the epidermis. 3. Damage to the dermis. 4. Damage
to the panniculus camosus. 5. Damage to the areolar tissue.
Group I The untreated group had a tissue-damage score in category (4), the damaged tissuebeing encrusted. Although the epidermis under the encrustation had regenerated, the dermal adnexae including hair follicles were not
visible. All layers of the epidermis, dermis and the panniculus camosushad become necrotic (Figure2a). Group 2 This group had a tissue-damage soore in category (I). From the epidermis to the panniculus carnosus,the tissuewas preserved to an almost normal extent (Figure2b). Group 3 This group had a tissue-damage score in category (3). Although the epidermisand dermis,including the dermal adnexae, had become necrotic, the panniculus camosuswas almost completely preserved (Figure2~). Group $4 This group had a tissue-damage score in category (4). Necrosis had extended into the panniculus camosus,and a similar histological picture to that seen in Group I was evident (Figure24.
Discussion Chemical injuries occur when certain chemical substances come into direct contact with the skin or mucous membranes, with the rapid onset of tissue damage. The recent increaseduse of chemical substances,both at home and at work, has multiplied the number of chemiciil injuries seen and treated daily in clinics and hospitals. Among chemical injuries, alkaline injuries occur relatively frequently and are
502
Burns: Vol. 21, No. 7, 1995
likely to cause severe symptoms. Acid injuries are similarly damaging but are somewhat less common. When acidic substances come into direct contact with the skin, hydrogen ions react with protein in the skin to form acid-proteinate, which in turn causes coagulation necrosis. Acid injuries, however, are no more progressive than alkaline injuries, and damage to adipose tissue is rare3. With chemical injuries, tissue damage continues to increase as long as the chemical is in contact with the tissue. For any treatment to be effective, it is necessary to remove the causative agent as quickly as possible, by washing the tissue with large volumes of water. Washing is presumed to cause dilution and elimination of the chemical substance, attenuation of the chemical reaction, and suppression of elevated tissue metabolism. Water is also thought to have an anti-inflammatory effect, to suppress hygroscopic activity, and to normalize skin pH levels4. Our study focused on subcutaneous tissue pH as an indicator of the effects of washing with water following acid injuries. The relationship between changes in subcutaneous pH and the severity of the injury was evaluated. Bromberg et a1.s produced acid injuries in mice using HCI, and initiated washing at 2 h, I h, 30 min and immediately after injury. They subsequently compared respective degrees of tissue damage. Macroscopic observation 1 h after injury in the group which was washed immediately revealed virtually no damaged tissue. In the group in which washing was initiated at 30 min, spots of necrotic tissue with encrustation were visible, and in the groups in which washing was initiated at z h or later, more severe damage was observed. Histologically, in the group in which washing was carried out immediately, only oedema and cellular infiltration were seen, and no destruction of the tissue structure was observed. In the untreated groups, there was necrosis extending through all layers of the tissue. Gruber et al6 used the same experimental system as Bromberg et al., but washing with water was initiated at I and 3 min after injury respectively. Skin injury was markedly reduced when the washing was initiated earlier. Therefore, our results, and those of the authors mentioned above, indicate that if washing is carried out before the subcutaneous tissue pH level reaches its minimum value, the remaining acid on the skin surface has been washed away. The washing effectively suppresses the subsequent fall in pH. Furthermore, when washing occurs before the subcutaneous pH reaches its minimum value, the degree of skin damage is less severe. It was thus surmised that the fall in subcutaneous pH is closely correlated with the degree of dermal damage. The relationship between the rise in pH and the time elapsed following the first 10 min after injury was derived from the correlation coefficient (Y) and the regression curve (y = LIX+ b; where y = subcutaneous tissue pH; x = time elapsed). Group 1 Group Group Group
2 3 4
y = 0.0043x-t 7.29 (v= 0.92) y = 0.0001~ + 7.58 (v= 0.64) y = 0.0017x+ 7.43 (r = 0.96) y=O.O053x+ 7.15 (rzO.95)
‘Theseresults indicate that the pH in Group 2 changed very little, and that the pH was close to normal at 10min postinjury. Additionally, there were significant differences (PC 0.05) between the a and b values of Group 2 and Group 1 and between Group 2 and Group 4, asdetermined using the t-test. There were no significant differences between the a and b values of Group 1 and Group 4, indicating that the rise in pH was very similar in the (IO min detayed) washed and the unwashed groups, once acid had penetrated into the subcutaneous tissue layers, Washing the tissue surface at this time had virtually no diluting effect, suggesting that elimination occurred by dispersion through the peripheral tissuesand the circula tory system. To summarize,washing should be continued until the subcutaneoustissuepH level reachesa minimum value, and should begin as soon as possible after injury. With severe acid injuries, after the subcutaneoustissue$3 has reached a minimum value, it is similarly necessaryto dilute and eliminate the acid that has already penetrated into the tissueasquickly aspossible.While the pH level of the skin may vary depending on the type and concentration of acid, and the experimental observations in this paper may not be applicable to all acid injuries, these suggestions should prove generally heipful in the treatment of acid injuries.
References Yano K, Hata Y, Matsuka K, Ito 0, Matsuda H. Experimentai study on alkaline skin injuries - periodic changes in subcutaneous tissue pH and the effects exerted by washing. Eum.~
1993;19:320-323. Yano K, Hata Y, Matsuka K, Ito 0, Matsuda H. Effects of washing with a neutralizing agent on alkaline skin injuries in an experimental model. Bums 1994; 20: 36-39. Mote@ M, Yamamoto S. Electricalinjuries,chemicalburn. in: Ohtsuka
7’
(cd)
Bwn
(Surgery
h4OOK
M7.34).
Tokyo-
Kanehara-Shuppan, 1983; p 166. Okada Y. Chemical burn. In: Sugimoto M, Ohura T (eds)Bum Tokyo: Nankodo. 1982; p 417. Bromberg BE, Song IC, Walden RH. Hydrotherapy of chemicd burns. Pht Reconstr Surg 1965;35: 85-95. Gruber RP, Laub DR, Vistnes LM. The effect of hydrotherapy on the clinical course and pH of experimental cutaneous chemical burns. Plasf Reconstr Surg 1975;55: 200-204.
Paper accepted 8 January .1995
Correspondence should be addressed fo: Dr Kenji Yano, Department of Dermatology, Division of Plastic Surgery, Osaka University School of Medicine, 2-2, Yamadaoka, Suita-shi, Osaka, 565, Japan.
K. Yano’, K. Hosokawal,
M. Kakibuchil,
H. H&sax
and Y. Hata’
‘Department of Dermatology, Division of Plastic Surgery, Osaka University Plastic Surgery, Kagawa Medical School, Japan
A skin acid injury model has been constructed using SD rats and 1 N HCl. The changes overtime,with particularattentionto subcutaneous tissue pH, were recorded and included a comparative study of the effect of washingwith wafer at I,3 and 1Omin after injury, on subcutaneous fissue PH. Affer inflictingan acidinjury, the subcutaneous tissuepH of control animals reached ifs minimum value at the seventh minute, and had not recouered fu the pre-experimenfat level by the 60th minute. In the group of rats which was washed ut I min, fhe pH did nof drop below 7.5, it remained virtually unchanged. In the group washed at 3 min, the pH declined slightly, but subsequent to washing, the pH increasedgradually. In thegroup washed at 10 min, the changes in pH were almost the same as those in fhe untreated group. These results indicated that if washing was carriedout before the subcutaneous tissue pH level reached a minimum value, any remaining acid on the skin surface could be washed away, effectively suppressing fhe subsequent fall in pH.
Burns, Vol. 21. No. 7, 500-502,
1995
Introduction Chemical injuries occur when chemicalscome into direct contact with the skin or mucous membranes. We have previously reported it is markedly effective for skin alkaline injuries to wash them with water as soon as possible before the pH value of the subcutaneoustissue reachesits peak’,‘. In fhis study, using a similar experimental model, acid injuries were investigated and the therapeutic effects of washing were assessed.
Materials
School of Medicine and ZDepartment of
IN-HCl to the skin over a circular area with a diameter of 2 cm, directly above the tip of the electrode. The subcutaneous pH was recorded at I-min intervals, up to 60 min following infliction of the injury. The rats used in the experiment were divided into four groups (n = 5). Group 1 remaineduntreated, while Groups 2, 3 and 4 received continuous washing with 500ml of distilled water (33 ml/min), starting at I, 3 and 10min postinjury respectively. The pH values were determined continuously. Student’s f-test was used to assessdifferencesbetween the groups. After IO days, the injured skin was biopsied for histological studies.
Results Periodic changes in the subcutaneous tissue pH Group 1 The pre-experimental subcutaneoustissuepH was 7.71 f 0.06. After injury, the pH gradually declined and at 7min reached a minimum at pH 7.22 f 0.08. Thereafter, it gradually increased, and at 60min the pH was 7.48 f 0.01 (Figure Il. Group 2 After initiating washing, the decline in the pH ceased,During the entire experiment, the pH did not fall below 7.5 and remainedvirtually unchanged. A significant difference (PC 0.01) in pH, when compared with the untreated group, was found after the second minute. PH
and methods
The experimental animalsusedwere 20 Sprague-Dawley rats, each weighing approximately 300g. After inducing general anaesthesiaby the intraperitoneal injection of nembutal, the rats were restrained in the dorsal position, and their abdomens were shaved. A small incision was made in the upper abdominal region, and a needle-shaped antimony pH microelectrode (diameter I mm, length 20 mm, responsetime 10-15 s, Chemical Kiki Co., Tokyo. Japan) was inserted immediately under the panniculus carnosus. A comparative electrode was affixed with double-coated tape to the opposite side of the abdomen. The acid injury was induced by applying 0.05 ml of
71 1
.70 1
0
2
4
6
8
10
20
30
40
50
60 Time :mwj
Figure 1. Periodic changesin the subcutaneous tissue pH. Results given are meani s.e., n= 5. O-0, Washing from I min; R-W, washing from 3 min; A-A, flushing from IOmin. ‘PCO.05; “P-CO.01.
501
Yano et al.: Washing acid injuries to the skin with water
Figure 2. Histological pictures on day 10. a, Group I: all layers of the epidermis, dermis and the panniculus camosus had become necrotic. b, Group 2: from the epidermis to the superficial muscle layer, the tissue was preserved to an almost normal extent. c, Group 3: although the epidermis and dermis, including the dermal adnexae, had become necrotic, the panniculus camosus was almost completely preserved. d, Group 4: necrosis had extended into the panniculus camosus.
Group 3 Until initiating washing, the pH declined slightly. Subsequent to washing, however, the pH increased gradually, until at 60min it had returned to 7.52 f 0.02. A significant difference (P-C 0.05) in pH when compared with the untreated group was detectable between the eighth min and the twenty-fifth minute. Group 4 The changesin pH were virtually the sameas those measuredin the untreated group. During the entire experiment, no significant differences in pH were detectable when compared with the untreated group. Histological assessment’of the skin A histological assessmentof the skin on day 10 after the acid injury, used the following tissue-damage scoring system to evaluate the extent of injury: 1. Almost normal. 2. Damage to the epidermis. 3. Damage to the dermis. 4. Damage
to the panniculus camosus. 5. Damage to the areolar tissue.
Group I The untreated group had a tissue-damage score in category (4), the damaged tissuebeing encrusted. Although the epidermis under the encrustation had regenerated, the dermal adnexae including hair follicles were not
visible. All layers of the epidermis, dermis and the panniculus camosushad become necrotic (Figure2a). Group 2 This group had a tissue-damage soore in category (I). From the epidermis to the panniculus carnosus,the tissuewas preserved to an almost normal extent (Figure2b). Group 3 This group had a tissue-damage score in category (3). Although the epidermisand dermis,including the dermal adnexae, had become necrotic, the panniculus camosuswas almost completely preserved (Figure2~). Group $4 This group had a tissue-damage score in category (4). Necrosis had extended into the panniculus camosus,and a similar histological picture to that seen in Group I was evident (Figure24.
Discussion Chemical injuries occur when certain chemical substances come into direct contact with the skin or mucous membranes, with the rapid onset of tissue damage. The recent increaseduse of chemical substances,both at home and at work, has multiplied the number of chemiciil injuries seen and treated daily in clinics and hospitals. Among chemical injuries, alkaline injuries occur relatively frequently and are
502
Burns: Vol. 21, No. 7, 1995
likely to cause severe symptoms. Acid injuries are similarly damaging but are somewhat less common. When acidic substances come into direct contact with the skin, hydrogen ions react with protein in the skin to form acid-proteinate, which in turn causes coagulation necrosis. Acid injuries, however, are no more progressive than alkaline injuries, and damage to adipose tissue is rare3. With chemical injuries, tissue damage continues to increase as long as the chemical is in contact with the tissue. For any treatment to be effective, it is necessary to remove the causative agent as quickly as possible, by washing the tissue with large volumes of water. Washing is presumed to cause dilution and elimination of the chemical substance, attenuation of the chemical reaction, and suppression of elevated tissue metabolism. Water is also thought to have an anti-inflammatory effect, to suppress hygroscopic activity, and to normalize skin pH levels4. Our study focused on subcutaneous tissue pH as an indicator of the effects of washing with water following acid injuries. The relationship between changes in subcutaneous pH and the severity of the injury was evaluated. Bromberg et a1.s produced acid injuries in mice using HCI, and initiated washing at 2 h, I h, 30 min and immediately after injury. They subsequently compared respective degrees of tissue damage. Macroscopic observation 1 h after injury in the group which was washed immediately revealed virtually no damaged tissue. In the group in which washing was initiated at 30 min, spots of necrotic tissue with encrustation were visible, and in the groups in which washing was initiated at z h or later, more severe damage was observed. Histologically, in the group in which washing was carried out immediately, only oedema and cellular infiltration were seen, and no destruction of the tissue structure was observed. In the untreated groups, there was necrosis extending through all layers of the tissue. Gruber et al6 used the same experimental system as Bromberg et al., but washing with water was initiated at I and 3 min after injury respectively. Skin injury was markedly reduced when the washing was initiated earlier. Therefore, our results, and those of the authors mentioned above, indicate that if washing is carried out before the subcutaneous tissue pH level reaches its minimum value, the remaining acid on the skin surface has been washed away. The washing effectively suppresses the subsequent fall in pH. Furthermore, when washing occurs before the subcutaneous pH reaches its minimum value, the degree of skin damage is less severe. It was thus surmised that the fall in subcutaneous pH is closely correlated with the degree of dermal damage. The relationship between the rise in pH and the time elapsed following the first 10 min after injury was derived from the correlation coefficient (Y) and the regression curve (y = LIX+ b; where y = subcutaneous tissue pH; x = time elapsed). Group 1 Group Group Group
2 3 4
y = 0.0043x-t 7.29 (v= 0.92) y = 0.0001~ + 7.58 (v= 0.64) y = 0.0017x+ 7.43 (r = 0.96) y=O.O053x+ 7.15 (rzO.95)
‘Theseresults indicate that the pH in Group 2 changed very little, and that the pH was close to normal at 10min postinjury. Additionally, there were significant differences (PC 0.05) between the a and b values of Group 2 and Group 1 and between Group 2 and Group 4, asdetermined using the t-test. There were no significant differences between the a and b values of Group 1 and Group 4, indicating that the rise in pH was very similar in the (IO min detayed) washed and the unwashed groups, once acid had penetrated into the subcutaneous tissue layers, Washing the tissue surface at this time had virtually no diluting effect, suggesting that elimination occurred by dispersion through the peripheral tissuesand the circula tory system. To summarize,washing should be continued until the subcutaneoustissuepH level reachesa minimum value, and should begin as soon as possible after injury. With severe acid injuries, after the subcutaneoustissue$3 has reached a minimum value, it is similarly necessaryto dilute and eliminate the acid that has already penetrated into the tissueasquickly aspossible.While the pH level of the skin may vary depending on the type and concentration of acid, and the experimental observations in this paper may not be applicable to all acid injuries, these suggestions should prove generally heipful in the treatment of acid injuries.
References Yano K, Hata Y, Matsuka K, Ito 0, Matsuda H. Experimentai study on alkaline skin injuries - periodic changes in subcutaneous tissue pH and the effects exerted by washing. Eum.~
1993;19:320-323. Yano K, Hata Y, Matsuka K, Ito 0, Matsuda H. Effects of washing with a neutralizing agent on alkaline skin injuries in an experimental model. Bums 1994; 20: 36-39. Mote@ M, Yamamoto S. Electricalinjuries,chemicalburn. in: Ohtsuka
7’
(cd)
Bwn
(Surgery
h4OOK
M7.34).
Tokyo-
Kanehara-Shuppan, 1983; p 166. Okada Y. Chemical burn. In: Sugimoto M, Ohura T (eds)Bum Tokyo: Nankodo. 1982; p 417. Bromberg BE, Song IC, Walden RH. Hydrotherapy of chemicd burns. Pht Reconstr Surg 1965;35: 85-95. Gruber RP, Laub DR, Vistnes LM. The effect of hydrotherapy on the clinical course and pH of experimental cutaneous chemical burns. Plasf Reconstr Surg 1975;55: 200-204.
Paper accepted 8 January .1995
Correspondence should be addressed fo: Dr Kenji Yano, Department of Dermatology, Division of Plastic Surgery, Osaka University School of Medicine, 2-2, Yamadaoka, Suita-shi, Osaka, 565, Japan.