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Laser assisted fusion of the rat stomach: Preliminary studies
JOURNAL
OF SURGICAL
RESEARCH
Laser Assisted DANIEL
T. DEMPSEY,
Departments
48, 223-229 (1990)
Fusion of the Rat Stomach: Preliminary
Studies’
M.D.,* DONNA SHOWERS, M.D., * PHILLIP VALENTE, M.D.,t RICHARD STERLING, STEPHEN PHILLIPS, M.D.,* AND JOHN V. WHITE, M.D.*
of *Surgery,
tPathology,
and SAnatomy, Temple University Submitted
for publication
School of Medicine, Philadelphia,
Pennsylvania
M.D.,*
19140
March 23, 1989
used to create sutureless welds in rabbit carotid artery [3], rabbit aorta [4], dog artery [ 51 and vein [6], rat carotid artery and sciatic nerve [2], and mouse skin [7]. Some preliminary data on the use of the Nd:YAG laser to fuse small intestinal wounds in rabbits has been reported [8]. We first reported the feasibility of closing rat gastrotomies with COZ laser-induced tissue fusion without suture [9]. In this paper we report physical, biochemical, and histologic studies performed on rat gastrotomy wounds closed with COZ laser-induced tissue fusion and compare this to wounds closed with standard suture technique.
The purpose of this study was (1) to determine whether rat gastrotomies could be securely closed without sutures by COz laser-induced tissue fusion alone and (2) to compare some characteristics (physical, biochemical, histological) of laser-fused gastrotomies with sutured gastrotomies. Following pentobarbital anesthesia a 1.5-cm longitudinal anterior gastrotomy was made in the forestomach of male Sprague-Dawley rats. This wound was closed using either a sutureless tissue weld created by a microscope-mounted COz laser (153 W/cm2) (Group I, N = 61) or with a running 6-O polypropylene suture (Group II, N = 58). Animals were sacrificed on Postoperative Days 1, 2, 4, 7, and 11 and the wounds were studied. Survival to scheduled sacrifice was 95% in Group I and 93% in Group II. Although bursting pressure of laserfused gastrotomies was significantly lower than that of sutured controls on Postoperative Day 1, measurement on subsequent days showed comparable wound strength between the laser and suture groups. Wound hydroxyproline content was significantly higher on Postoperative Day 1 and lower on Postoperative Day 11 in the laser group. Histologic examination of the laser-fused wounds revealed less inflammation and earlier reepithelialization than the sutured wounds, giving the microscopic aphealing wound. These results pearance of a “neater” suggest that laser-induced fusion is a feasible method of gastrointestinal wound closure which may complement standard suture techniques. o 1990 Academic PEW. L.
METHODS
Male Sprague-Dawley rats (average weight = 303 f 25 g) were used for this study and cared for according to the National Research Council’s guide for the care and use of laboratory animals. Rats were anesthetized with pentobarbital (15 to 20 mg intraperitoneally) and subjected to coeliotomy. A 1.5-cm longitudinal gastrotomy was made on the anterior surface of the forestomach. Animals were then divided into two groups. In Group I (laser fusion, N = 61), edges of the gastrotomy wound were apposed and elevated by the placement of two 6-O prolene stay sutures beyond either end of the wound. These were removed after the closure of the gastrotomy with the COZ laser. Tissue apposition during laser fusion was further facilitated by a specially designed tenaculum [lo]. Tissue fusion was done with a microscope-mounted CO2 laser (Sharplan Corp.). A power of 300 mW with a spot diameter of 0.5 mm on a continuous mode was used. This produces a power density of 153 W/cm2. The laser spot targeted with a coaxial helium-neon beam was moved back and forth over the gastrotomy wound to create a serosal weld, but to avoid char. The gastrotomy was periodically dabbed dry with a cotton swab since visible fluid between the tissue and laser beam markedly reduces the transfer of energy to the tissue and decreases the effectiveness of the welding. The gastrotomy could generally be welded closed in less than a minute. In Group II (suture closure, N = 58), the gastrotomy was closed with a running suture of 6-O polypropylene. This was done in a standardized fashion,
INTRODUCTION Laser-induced tissue fusion is widely used clinically to repair retinal detachment [l]. Because of its apparent ability to fuse tissues by changing connective tissue structure without inducing an exuberant foreign body reaction, laser fusion is a particularly attractive method of tissue repair in settings where minimization of tissue destruction, wound inflammation, and/or scar is desirable [ 21. Therefore, it may be superior to suture anastomosis of small arteries and nerves [2, 31. Laser energy has been 1 Supported in part by NIH Grant BRSG SO7 RR05417. 223
oozz-4804/90 $1.50 Copyright 0 1990 by Academic Press, Inc. All
rights
of reproduction
in any
form
reserved.
224
JOURNAL
TABLE
OF SURGICAL
RESEARCH:
1
Bursting Pressure (mm Hg) and Volume Infused to Bursting (cc) in Freshly Harvested Rat Stomachs with Laser-Fused (LF) and Sutured (SUT) Gastrotomies’ Postop day 1
Group (N)
mm Hg (X + SD)
Vol (cc) (X f SD)
LF (5) SUT (5)
60+ 9 98 f 22 0.01 80 + 20 69 f 27 0.32 117 f 26 123 f 12 0.54 145 + 13 161 f 26 0.13 208 f 38 188 f 18 0.15
a+ 2 16-c 5 0.01 llf 5 12f 7 0.58 21 f 17 19+ 8 0.58 30f 7 34f 5 0.21 42f 9 37Ik 5 0.14
P= 2
LF (11) SUT (10)
4
LF (11) SUT (9)
P= P= 7
LF (9) SUT (8)
P= 11
LF (10) SUT (10)
P= DStatistical significance paired t test, LF vs SUT.
of difference
determined
by two-tailed
un-
using six loops of suture to close the wound. Sutures were placed approximately 1 to 2 mm from the wound edge and tissue “bites” were full thickness stomach. Animals were allowed to recover and were fed rat chow and water ad lib. until they were sacrificed by ether overdose on Postoperative Days 1,2,4,7, or 11. The bursting pressure of freshly excised, emptied stomachs was measured by saline infusion (Harvard pump, 35 ml/min) into the esophageal end of the stomach after pyloric ligation. Bursting pressure was determined by a mercury manometer placed in series with the infusion tubing and was defined as the pressure at which saline began to leak from the stomach wall at a rate which equaled or exceeded the rate of infusion. Therefore, this was the maximal pressure attained during saline infusion. Volume infused to this point was recorded to control for possible differences in stomach volume at the time of bursting which could influence wound tension according to Laplace’s Law. The gastrotomy wound was then excised with a 2 X 0.5-cm template, dried to a constant weight, and analyzed for total hydroxyproline content (mg/lOO mg dry wt) by the method of Woessner [ 111. Gastrotomy wounds from three animals in both the laser fusion and suture groups were excised immediately after sacrifice on Postoperative Days 1,3, 7, and 17, and processed for histologic study by light microscopy (hematoxylin-eosin stain) and scanning electron microscopy. The two tailed t test for independent samples was used to test for significant differences between experimental and control groups. RESULTS
Morbidity and mortality. In the laser fusion group, 3 of 61 (5%) rats died prior to sacrifice. In the suture control
VOL. 48, NO. 3, MARCH
1990
group the presacrifice mortality was 4 of 58 (7%). In all cases of death prior to sacrifice, postmortem examination revealed left upper quadrant abscess. In all of the laser fusion animals, this was associated with gross dehiscence of the gastrotomy wound. In the suture control animals, this was associated with a smaller discrete perforation of the suture line. The animals generally resumed normal food intake by Postoperative Day 3, and postoperative weight change was not different between the groups. Bursting pressure (Table 1). Laser-fused gastrotomies were significantly weaker than sutured controls on Postoperative Day 1 (POD 1). The volume infused to bursting in the laser fusion group was significantly less than that required to burst the sutured wounds on POD 1. On POD 2, the laser-fused wounds were stronger than on POD 1 (80 f 20 vs 60 -t 9, P < O.lO), while the sutured wounds were weaker (69 + 27 vs 98 -t 22, P < 0.10). After the first postoperative day, laser-fused and sutured gastrotomies were equally strong, bursting at similar pressures and requiring similar quantities of fluid distention prior to bursting. By POD 11, the bursting pressures in both the experimental and control groups was not different from those of unwounded stomachs (190 + 6 mm Hg, N = 5). Wound hydroxyproline content (Table 2). On POD 1, there was significantly more hydroxyproline in the laserfused gastrotomies compared to sutured controls. There was a steady trend toward increasing amounts of hydroxyproline in the sutured gastrotomies over time which was not observed in the laser-fused gastrotomies. In fact, the tendency in the laser-fused gastrotomies was toward a decrease in wound hydroxyproline content that by POD 11 reached a level significantly less than that found in the sutured controls. Histology. Light microscopic examination of the laserfused gastrotomy on POD 1 showed much less acute inflammation and better tissue approximation than the su-
TABLE
2
Hydroxyproline Content (mg/lOO mg dry wt) of Rat Gastrotomy Wounds Closed with Laser Fusion (LF) and Suture (SUT) Postop day 1 2 4 7 11
’ Two-tailed
unpaired
(X SD,
SUT (X f SD)
2.0 f N=5 2.0 + N= 1.3 Ii N= 1.9 f N=9 1.5 k N =
1.2 f N=5 1.5 + N = 1.5 k N=9 1.8 + N=8 2.0 f N =
0.4 0.6 11 0.5 11 0.5 0.5 10
t test.
P"
0.3
0.01
0.5 10 0.6
0.12
0.6
0.67
0.5 10
0.03
0.35
a al 225
226
JOURNAL
OF SURGICAL
RESEARCH:
VOL. 48, NO. 3, MARCH
FIG. 3. Low power (20X) scanning electron micrograph (EM) of laser-fused gastrotomy on Postoperative of stomach wall.
tured gastrotomy (Figs. 1 and 2). Low power scanning electron microscopic examination on POD 3 revealed a very smooth laser-fused gastrotomy wound with evidence of reepithelialization and normal orientation of seromuscular elements (Fig. 3). This was in marked contrast to the sutured wound which appeared irregular, heaped-up, and disorganized (Fig. 4). By POD 7, the laser-fused wound showed obvious inflammation (Fig. 5), but had near normal architecture when compared to the sutured closure. Foreign body giant cells were obvious in the sutured gastrotomies, but noticeably absent in the laser-fused wound. By POD 17, the
1990
Day 3 showing near normal architecture
laser-fused gastrotomy revealed a rather thin scar in the muscular stomach wall with some fibrosis. There was minimal epithelial trapping and foreign body reaction. By contrast, the sutured gastrotomy revealed prominent epithelial trapping, chronic inflammation, and focal ulceration (Fig. 6). DISCUSSION This study shows that the COP laser can be used to close rat gastrotomies by tissue fusion alone without suture. These wounds heal adequately and have a low rate
DEMPSEY
FIG. 4.
ET AL.: LASER
FUSION
Low power (20X) scanning EM of sutured gastrotomy
ofdehiscence. Although weaker on the first postoperative day, the laser-fused gastrotomy wounds steadily increase in strength and unlike the sutured gastrotomy wounds do not weaken in the early postoperative period. The collagen content in the laser-fused wounds is significantly higher early, but significantly lower late when compared to the sutured gastrotomy wounds. These findings suggest that laser-induced tissue fusion and suture repair of gastrointestinal tissue may be complimentary techniques, and we are currently performing studies of gastrotomy wounds closed in a double layer suture/laser fashion. Histologic examination clearly revealed a “neater wound” in the laser-fused stomachs. There was less in-
OF RAT
STOMACH
on Postoperative
227
Day 3. Compare with Fig. 3.
flammation in the laser-fused wounds at all days studied. Furthermore, the inflammatory response in the laserfused wounds was somewhat delayed. Whether this accounts for the high initial hydroxyproline content in the laser-fused wounds is unclear, but decreased wound inflammation with resultant decrease in collagen lysis is one possible explanation. Additional histologic studies at later postoperative time points might show other differences between lasered and sutured stomach wounds. Laser welding of small vessels and nerves is attractive because it appears to result in less scarring and less distortion of normal tissue architecture. This appears to result in a more satisfactory repair of small nerves and ar-
_ i FIG. 5.
FIG. 6.
Photomicrograph
Sutured gastrotomy
(20X) of laser-fused
on Postoperative
gastrotomy
on Postoperative
Day 17 showing inflammation, 228
epithelial
‘.
Day 7. See text.
trapping,
and ulceration
(20X).
DEMPSEY
ET AL.: LASER
teries [2, 31. The physiologic processes involved in the healing of a sutured wound which interfere with an optimal result in the repair of the small structures noted above rarely thwart the gastrointestinal surgeon. Most GI anastomoses heal satisfactorily and clinically significant anastomotic leak or stricture is infrequent. However, laser-assisted fusion of GI tissue may be useful, or even desirable, for other reasons. First, laser energy is transferred to the fusion site via a beam and could therefore be used to fuse tissue in places where suture anastomosis is technically difficult. Second, laser energy applied to the wound during tissue fusion destroys bacteria at the wound site and therefore theoretically might decrease the chance of microinfection and subsequent leak. Third, since there is less tissue destruction and wound inflammation in a laser-fused wound, epithelial integrity at the GI anastomosis may be more readily restored. There is some evidence that this is the case based upon the scanning electron microscopy at Postoperative Day 3. Fourth, there is suggestive evidence that low dose laser energy stimulates fibroblast activity and may speed wound healing [ 121. Finally, there is some scanty evidence which suggests that a laser-fused GI wound incites less adhesion formation than does a sutured wound [8]. If some of the above possibilities are proven in the experimental laboratory they might provide further impetus toward the complimentary use of tissue fusion and suture repair in the GI tract. At this point in time, such techniques are purely experimental and should not be used by surgeons in the operating room.
FUSION
OF RAT
STOMACH
229
REFERENCES 1.
L’Esperance,
F. A., Jr. Trans. Amer. Acad. Opthalmol. Otokzryngol.
74:609,1971. 2. Schober, R., Ulrich, F., Sander, T., Durselen, H., and Helssel, S.
3. 4. 5.
6.
7.
8.
9.
10. 11.
12.
Laser-induced alteration of collagen substructure allows microsurgical tissue welding. Science 36: 455, 1985. White, J. V., Dalsing, M. C., Yao, J. S. T., et al. Tissue fusion effects of the COP laser. Surg. Forum 36: 455, 1985. White, J. V. Unpublished data. White, R. A., Abergel, R. P., Klein, S. R., Kopchok, G., Dwyer, R. M., and Uitto, J. Biological effects of laser welding on vascular healing. Lasers Surg. Med. 6: 137, 1986. White, R. A., Abergel, R. P., Lyons, R., Kopchok, G., Kelin, S. R., Dwyer, R. M., and Uitto, J. Laser welding: An alternative method of venous repair. J. Surg. Res. 41: 260, 1986. Abergel, R. P., Lyons, R. F., White, R. A., Lask, G., Dwyer, R. M., and Uitto, J. Closure of skin wounds by Nd:YAG laser welding. J. Amer. Acad. Dermatol. 14: 810, 1986. Cespanyi, E., White, R. A., Lyons, R., et al. Preliminary report: A new technique of enterotomy closure using Nd:YAG laser welding compared to suture repair. J. Surg. Res. 42: 147, 1987. Dempsey, D. T., Showers, D., Valente, P., Sterling, R., and White, J. V. Tissue fusion of the rat stomach with the CO* laser. Surg. Forum 38: 118, 1987. White, J. V. Laser instrumentation-A microtenaculum for laser tissue fusion. Lasers Surg. Med. 8: 433, 1988. Woessner, J. F. The determination of hydroxyproline in tissue and protein samples containing small proportions of this amino acid. Arch. Biochem. Biophys. 93: 440, 1961. Abergel, R. P., Meeker, C. A., Lam, R. S., Dwyer, R. M., Lesavoy, M. A., and Uitto, J. Control of connective tissue metabolism by lasers: Recent developments and future prospects. J. Amer. Acad. Dermatol. 11:1142,1984.
OF SURGICAL
RESEARCH
Laser Assisted DANIEL
T. DEMPSEY,
Departments
48, 223-229 (1990)
Fusion of the Rat Stomach: Preliminary
Studies’
M.D.,* DONNA SHOWERS, M.D., * PHILLIP VALENTE, M.D.,t RICHARD STERLING, STEPHEN PHILLIPS, M.D.,* AND JOHN V. WHITE, M.D.*
of *Surgery,
tPathology,
and SAnatomy, Temple University Submitted
for publication
School of Medicine, Philadelphia,
Pennsylvania
M.D.,*
19140
March 23, 1989
used to create sutureless welds in rabbit carotid artery [3], rabbit aorta [4], dog artery [ 51 and vein [6], rat carotid artery and sciatic nerve [2], and mouse skin [7]. Some preliminary data on the use of the Nd:YAG laser to fuse small intestinal wounds in rabbits has been reported [8]. We first reported the feasibility of closing rat gastrotomies with COZ laser-induced tissue fusion without suture [9]. In this paper we report physical, biochemical, and histologic studies performed on rat gastrotomy wounds closed with COZ laser-induced tissue fusion and compare this to wounds closed with standard suture technique.
The purpose of this study was (1) to determine whether rat gastrotomies could be securely closed without sutures by COz laser-induced tissue fusion alone and (2) to compare some characteristics (physical, biochemical, histological) of laser-fused gastrotomies with sutured gastrotomies. Following pentobarbital anesthesia a 1.5-cm longitudinal anterior gastrotomy was made in the forestomach of male Sprague-Dawley rats. This wound was closed using either a sutureless tissue weld created by a microscope-mounted COz laser (153 W/cm2) (Group I, N = 61) or with a running 6-O polypropylene suture (Group II, N = 58). Animals were sacrificed on Postoperative Days 1, 2, 4, 7, and 11 and the wounds were studied. Survival to scheduled sacrifice was 95% in Group I and 93% in Group II. Although bursting pressure of laserfused gastrotomies was significantly lower than that of sutured controls on Postoperative Day 1, measurement on subsequent days showed comparable wound strength between the laser and suture groups. Wound hydroxyproline content was significantly higher on Postoperative Day 1 and lower on Postoperative Day 11 in the laser group. Histologic examination of the laser-fused wounds revealed less inflammation and earlier reepithelialization than the sutured wounds, giving the microscopic aphealing wound. These results pearance of a “neater” suggest that laser-induced fusion is a feasible method of gastrointestinal wound closure which may complement standard suture techniques. o 1990 Academic PEW. L.
METHODS
Male Sprague-Dawley rats (average weight = 303 f 25 g) were used for this study and cared for according to the National Research Council’s guide for the care and use of laboratory animals. Rats were anesthetized with pentobarbital (15 to 20 mg intraperitoneally) and subjected to coeliotomy. A 1.5-cm longitudinal gastrotomy was made on the anterior surface of the forestomach. Animals were then divided into two groups. In Group I (laser fusion, N = 61), edges of the gastrotomy wound were apposed and elevated by the placement of two 6-O prolene stay sutures beyond either end of the wound. These were removed after the closure of the gastrotomy with the COZ laser. Tissue apposition during laser fusion was further facilitated by a specially designed tenaculum [lo]. Tissue fusion was done with a microscope-mounted CO2 laser (Sharplan Corp.). A power of 300 mW with a spot diameter of 0.5 mm on a continuous mode was used. This produces a power density of 153 W/cm2. The laser spot targeted with a coaxial helium-neon beam was moved back and forth over the gastrotomy wound to create a serosal weld, but to avoid char. The gastrotomy was periodically dabbed dry with a cotton swab since visible fluid between the tissue and laser beam markedly reduces the transfer of energy to the tissue and decreases the effectiveness of the welding. The gastrotomy could generally be welded closed in less than a minute. In Group II (suture closure, N = 58), the gastrotomy was closed with a running suture of 6-O polypropylene. This was done in a standardized fashion,
INTRODUCTION Laser-induced tissue fusion is widely used clinically to repair retinal detachment [l]. Because of its apparent ability to fuse tissues by changing connective tissue structure without inducing an exuberant foreign body reaction, laser fusion is a particularly attractive method of tissue repair in settings where minimization of tissue destruction, wound inflammation, and/or scar is desirable [ 21. Therefore, it may be superior to suture anastomosis of small arteries and nerves [2, 31. Laser energy has been 1 Supported in part by NIH Grant BRSG SO7 RR05417. 223
oozz-4804/90 $1.50 Copyright 0 1990 by Academic Press, Inc. All
rights
of reproduction
in any
form
reserved.
224
JOURNAL
TABLE
OF SURGICAL
RESEARCH:
1
Bursting Pressure (mm Hg) and Volume Infused to Bursting (cc) in Freshly Harvested Rat Stomachs with Laser-Fused (LF) and Sutured (SUT) Gastrotomies’ Postop day 1
Group (N)
mm Hg (X + SD)
Vol (cc) (X f SD)
LF (5) SUT (5)
60+ 9 98 f 22 0.01 80 + 20 69 f 27 0.32 117 f 26 123 f 12 0.54 145 + 13 161 f 26 0.13 208 f 38 188 f 18 0.15
a+ 2 16-c 5 0.01 llf 5 12f 7 0.58 21 f 17 19+ 8 0.58 30f 7 34f 5 0.21 42f 9 37Ik 5 0.14
P= 2
LF (11) SUT (10)
4
LF (11) SUT (9)
P= P= 7
LF (9) SUT (8)
P= 11
LF (10) SUT (10)
P= DStatistical significance paired t test, LF vs SUT.
of difference
determined
by two-tailed
un-
using six loops of suture to close the wound. Sutures were placed approximately 1 to 2 mm from the wound edge and tissue “bites” were full thickness stomach. Animals were allowed to recover and were fed rat chow and water ad lib. until they were sacrificed by ether overdose on Postoperative Days 1,2,4,7, or 11. The bursting pressure of freshly excised, emptied stomachs was measured by saline infusion (Harvard pump, 35 ml/min) into the esophageal end of the stomach after pyloric ligation. Bursting pressure was determined by a mercury manometer placed in series with the infusion tubing and was defined as the pressure at which saline began to leak from the stomach wall at a rate which equaled or exceeded the rate of infusion. Therefore, this was the maximal pressure attained during saline infusion. Volume infused to this point was recorded to control for possible differences in stomach volume at the time of bursting which could influence wound tension according to Laplace’s Law. The gastrotomy wound was then excised with a 2 X 0.5-cm template, dried to a constant weight, and analyzed for total hydroxyproline content (mg/lOO mg dry wt) by the method of Woessner [ 111. Gastrotomy wounds from three animals in both the laser fusion and suture groups were excised immediately after sacrifice on Postoperative Days 1,3, 7, and 17, and processed for histologic study by light microscopy (hematoxylin-eosin stain) and scanning electron microscopy. The two tailed t test for independent samples was used to test for significant differences between experimental and control groups. RESULTS
Morbidity and mortality. In the laser fusion group, 3 of 61 (5%) rats died prior to sacrifice. In the suture control
VOL. 48, NO. 3, MARCH
1990
group the presacrifice mortality was 4 of 58 (7%). In all cases of death prior to sacrifice, postmortem examination revealed left upper quadrant abscess. In all of the laser fusion animals, this was associated with gross dehiscence of the gastrotomy wound. In the suture control animals, this was associated with a smaller discrete perforation of the suture line. The animals generally resumed normal food intake by Postoperative Day 3, and postoperative weight change was not different between the groups. Bursting pressure (Table 1). Laser-fused gastrotomies were significantly weaker than sutured controls on Postoperative Day 1 (POD 1). The volume infused to bursting in the laser fusion group was significantly less than that required to burst the sutured wounds on POD 1. On POD 2, the laser-fused wounds were stronger than on POD 1 (80 f 20 vs 60 -t 9, P < O.lO), while the sutured wounds were weaker (69 + 27 vs 98 -t 22, P < 0.10). After the first postoperative day, laser-fused and sutured gastrotomies were equally strong, bursting at similar pressures and requiring similar quantities of fluid distention prior to bursting. By POD 11, the bursting pressures in both the experimental and control groups was not different from those of unwounded stomachs (190 + 6 mm Hg, N = 5). Wound hydroxyproline content (Table 2). On POD 1, there was significantly more hydroxyproline in the laserfused gastrotomies compared to sutured controls. There was a steady trend toward increasing amounts of hydroxyproline in the sutured gastrotomies over time which was not observed in the laser-fused gastrotomies. In fact, the tendency in the laser-fused gastrotomies was toward a decrease in wound hydroxyproline content that by POD 11 reached a level significantly less than that found in the sutured controls. Histology. Light microscopic examination of the laserfused gastrotomy on POD 1 showed much less acute inflammation and better tissue approximation than the su-
TABLE
2
Hydroxyproline Content (mg/lOO mg dry wt) of Rat Gastrotomy Wounds Closed with Laser Fusion (LF) and Suture (SUT) Postop day 1 2 4 7 11
’ Two-tailed
unpaired
(X SD,
SUT (X f SD)
2.0 f N=5 2.0 + N= 1.3 Ii N= 1.9 f N=9 1.5 k N =
1.2 f N=5 1.5 + N = 1.5 k N=9 1.8 + N=8 2.0 f N =
0.4 0.6 11 0.5 11 0.5 0.5 10
t test.
P"
0.3
0.01
0.5 10 0.6
0.12
0.6
0.67
0.5 10
0.03
0.35
a al 225
226
JOURNAL
OF SURGICAL
RESEARCH:
VOL. 48, NO. 3, MARCH
FIG. 3. Low power (20X) scanning electron micrograph (EM) of laser-fused gastrotomy on Postoperative of stomach wall.
tured gastrotomy (Figs. 1 and 2). Low power scanning electron microscopic examination on POD 3 revealed a very smooth laser-fused gastrotomy wound with evidence of reepithelialization and normal orientation of seromuscular elements (Fig. 3). This was in marked contrast to the sutured wound which appeared irregular, heaped-up, and disorganized (Fig. 4). By POD 7, the laser-fused wound showed obvious inflammation (Fig. 5), but had near normal architecture when compared to the sutured closure. Foreign body giant cells were obvious in the sutured gastrotomies, but noticeably absent in the laser-fused wound. By POD 17, the
1990
Day 3 showing near normal architecture
laser-fused gastrotomy revealed a rather thin scar in the muscular stomach wall with some fibrosis. There was minimal epithelial trapping and foreign body reaction. By contrast, the sutured gastrotomy revealed prominent epithelial trapping, chronic inflammation, and focal ulceration (Fig. 6). DISCUSSION This study shows that the COP laser can be used to close rat gastrotomies by tissue fusion alone without suture. These wounds heal adequately and have a low rate
DEMPSEY
FIG. 4.
ET AL.: LASER
FUSION
Low power (20X) scanning EM of sutured gastrotomy
ofdehiscence. Although weaker on the first postoperative day, the laser-fused gastrotomy wounds steadily increase in strength and unlike the sutured gastrotomy wounds do not weaken in the early postoperative period. The collagen content in the laser-fused wounds is significantly higher early, but significantly lower late when compared to the sutured gastrotomy wounds. These findings suggest that laser-induced tissue fusion and suture repair of gastrointestinal tissue may be complimentary techniques, and we are currently performing studies of gastrotomy wounds closed in a double layer suture/laser fashion. Histologic examination clearly revealed a “neater wound” in the laser-fused stomachs. There was less in-
OF RAT
STOMACH
on Postoperative
227
Day 3. Compare with Fig. 3.
flammation in the laser-fused wounds at all days studied. Furthermore, the inflammatory response in the laserfused wounds was somewhat delayed. Whether this accounts for the high initial hydroxyproline content in the laser-fused wounds is unclear, but decreased wound inflammation with resultant decrease in collagen lysis is one possible explanation. Additional histologic studies at later postoperative time points might show other differences between lasered and sutured stomach wounds. Laser welding of small vessels and nerves is attractive because it appears to result in less scarring and less distortion of normal tissue architecture. This appears to result in a more satisfactory repair of small nerves and ar-
_ i FIG. 5.
FIG. 6.
Photomicrograph
Sutured gastrotomy
(20X) of laser-fused
on Postoperative
gastrotomy
on Postoperative
Day 17 showing inflammation, 228
epithelial
‘.
Day 7. See text.
trapping,
and ulceration
(20X).
DEMPSEY
ET AL.: LASER
teries [2, 31. The physiologic processes involved in the healing of a sutured wound which interfere with an optimal result in the repair of the small structures noted above rarely thwart the gastrointestinal surgeon. Most GI anastomoses heal satisfactorily and clinically significant anastomotic leak or stricture is infrequent. However, laser-assisted fusion of GI tissue may be useful, or even desirable, for other reasons. First, laser energy is transferred to the fusion site via a beam and could therefore be used to fuse tissue in places where suture anastomosis is technically difficult. Second, laser energy applied to the wound during tissue fusion destroys bacteria at the wound site and therefore theoretically might decrease the chance of microinfection and subsequent leak. Third, since there is less tissue destruction and wound inflammation in a laser-fused wound, epithelial integrity at the GI anastomosis may be more readily restored. There is some evidence that this is the case based upon the scanning electron microscopy at Postoperative Day 3. Fourth, there is suggestive evidence that low dose laser energy stimulates fibroblast activity and may speed wound healing [ 121. Finally, there is some scanty evidence which suggests that a laser-fused GI wound incites less adhesion formation than does a sutured wound [8]. If some of the above possibilities are proven in the experimental laboratory they might provide further impetus toward the complimentary use of tissue fusion and suture repair in the GI tract. At this point in time, such techniques are purely experimental and should not be used by surgeons in the operating room.
FUSION
OF RAT
STOMACH
229
REFERENCES 1.
L’Esperance,
F. A., Jr. Trans. Amer. Acad. Opthalmol. Otokzryngol.
74:609,1971. 2. Schober, R., Ulrich, F., Sander, T., Durselen, H., and Helssel, S.
3. 4. 5.
6.
7.
8.
9.
10. 11.
12.
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