Session IV - PolyTrauma

Friday, October 9, 1998 Session IV, 8:20 a.m.

Evaluation of Standard Surgical Preparation Performed on Superficial Dermal Abrasions

Kyle J. Jeray, MD; David M. Banks, MD; Laura Senunas Phieffer, MD; Michael D. Hudson, PhD; Michael J. Bosse, MD, Carolinas Medical Center, Charlotte, NC

Introduction: The timing of surgery on closed fractures with traumatic abrasions at the planned surgical site is controversial. Surgery delayed past the early injury phase potentially provides a surgical site heavily colonized with hospital and host bacteria. Delay until the abrasions epithelialize can increase the difficulty of the reduction and the necessity for additional soft tissue dissection, particularly in peri-articular injuries. The ability of the standard surgical preparation to decontaminate a dirty or colonized abrasion is not described. The purpose of this study is to determine the difference, if any, between the reduction of bacteria on contaminated normal dermis and contaminated superficially abraded dermis following standard surgical preparations at clinically relevant points from the injury.

Materials and Methods: Thirty-two New Zealand white (18 male and 18 female) rabbits were shaved on the dorsum, midline from caudal to cranial. Two 2x2 cm sites were marked, one caudal and one cranial. A standard degreasing agent was used to clean the skin. An abrasion was created at one site using an electric dermatome standardized to a thickness of 0.0015 inches. Fifty microliters (concentration 1.4x108 to 1.2x1010) of encapsulated S. aureus strain Wood 46 (one of the most common organisms associated with diseases of the skin), was used to inoculate each site. An initial 6-mm circular dermal punch biopsy was then taken from each site to quantify initial colonization. The rabbits were divided into 4 cohort groups: surgical preparations done at 6 hours, 12 hours, 24 hours, and 48 hours after abrasion and inoculation. A second biopsy was obtained prior to surgical scrub, a third 5 minutes after surgical preparation, and a fourth 2 hours after surgical preparation (during this 2-hour wait the animals remained anesthetized on a sterile field in the operating room). The surgical scrub was performed using a standard surgical scrub sponge and 10% povidone-iodine solution for 2 minutes followed by blotting and application of 10% povidone-iodine paint. All biopsies were placed in soy broth containing 1% sodium thiosulfate (used to neutralize the povidine-iodine) and held on ice until quantitative bacterial testing. The biopsies were sterilely homogenized and serially diluted to determine bacterial counts.

Standard statistical methods were completed using, SAS, System for Windows, Version 6.12. ANOVA and paired t-tests were used. For data not normally distributed the Wilcoxon signed rank test was used. A P -value less than 0.05 was considered significant.

Results: The amount of bacteria on the normal skin (control sites) dropped significantly (P < 0.02) prior to surgical preparation except at 6 hours (P < 0.20). At the abraded sites, the bacteria flourished (see table). Surgical scrub dropped bacterial counts significantly (P < 0.05) at all sites except for the 24- hour abraded site (P <0.08). Following the standard surgical prep on the 12-, 24-, and 48- hour sites, significantly different (P < 0.008) bacterial counts were found comparing the control to the abraded sites. 


			

				
			
				
				
				Control Site (mean bacterial counts)
				
				Abrasion Site(mean bacterial counts)
			

			

				
			
			
				Time (hrs.)
				
				

				
				

				
Time Zero
Biopsy

				
				

				
				

				
Pre-scrub
Biopsy

				
				

				
				

				
Post-scrub
Biopsy

				
				

				
				

				
Time Zero
Biopsy

				
				

				
				

				
Pre-scrub
Biopsy

				
				

				
				

				
Post-scrub
Biopsy

			

			

				
			
			
				6
				
				4.3E7
				
				5.8E6
				
				 545*
				
				1.4E7
				
				1.5E7
				
				543*
			

			

				
			
			
				12
				
				8.1E7
				
				9.4E3
				
				59* **
				
				4.9E7
				
				 4.1E7
				
				6.4E6* 
			

			

				
			
			
				24
				
				7.2E6
				
				4.6E3
				
				90* **
				
				1.4E7
				
				4.3E6
				
				1.1E6
			

			

				
			
			
				48
				
				7.3E6
				
				4.3E2
				
				10* **
				
				4.6E6
				
				2.2E6
				
				 1.7E5*
			

		

		
			
		
		*pre to post scrub decrease (P < 0.05)                         Note: En = x10n 
**post-scrub bacteria - control vs. abrasion (P <0 .008)
Discussion: The epidermis provides a barrier and skin lipids provide an additional resistance to bacteria. This explains why there was a decrease in the bacterial counts prior to surgical preparation on the normal skin (control site). The abraded site however, appears to provide an excellent culture environment for the inoculated bacteria. Alarmingly, despite a standard surgical preparation, the bacterial counts at the abraded sites remained at greater than 1x105 at 12 hours and beyond. Correspondingly, the control sites had on average less than 100 colonies. This study suggested that surgeons should approach surgery through abraded skin with caution, particularly, if done beyond the 6-hour point. Studies on human abrasion and on the effect of bacterial counts with environment modulation with topical antibiotics are required.

Conclusion: In a rabbit model using S. aureus to contaminate abraded skin, the standard surgical preparation using povidine-iodine is effective at reducing bacterial counts to that of surgically prepared normal skin up to 6 hours. At 12-48 hours, the surgical preparation is ineffective.