Situation: The nurse is assigned as the circulating nurse in an operating room for a day of elective surgical cases. During the third case, sterile saline spills onto the drape covering the instrument table and soaks through to the table surface. A nursing student asks why the soaked area must now be treated as contaminated. Which explanation is correct?

When a sterile drape or wrapper becomes wet, moisture carries microorganisms through the material from the unsterile surface underneath (strike-through contamination). The wet area is therefore considered contaminated and is covered or replaced.

Strike-through contamination: why a soaked sterile drape is no longer sterile

A sterile drape is only a microbial barrier as long as it stays dry. Once it becomes wet, the fluid itself becomes a vehicle that carries microorganisms from the unsterile surface underneath through the material to the sterile field above. This phenomenon is called strike-through contamination.

The correct explanation is that moisture wicks microbes up from the surface below through the drape. Sterile saline is sterile when it comes out of the bottle, but when it soaks through the drape and reaches the nonsterile table surface beneath, it picks up whatever organisms are present there. Capillary action and the movement of the fluid then carry those organisms back up through the moistened fabric to the top of the drape. The soaked area is therefore no longer a reliable sterile barrier and must be treated as contaminated.

Watch out! The issue is not that the saline itself is contaminated. Even sterile fluid creates strike-through when it bridges the sterile and nonsterile sides of a drape.

Key point! A wet sterile drape is considered contaminated at the point of moisture penetration, regardless of what the fluid is. The standard intervention is to cover the wet area with another sterile drape or replace the entire drape.

The study by Laufman and colleagues supports this principle. They tested woven and nonwoven surgical gown and drape materials under conditions of stretching and moist contamination, and found that not all surgical materials are impermeable to moist bacterial strike-through for equal periods of time. Some nonwoven disposable materials remained impermeable throughout testing, while others became permeable to bacteria almost immediately once moisture was present. This means that the nurse cannot assume a drape will protect the sterile field simply because it is labeled as a barrier material. The moment visible moisture soaks through, the barrier function at that site is compromised.

For the circulating nurse, this has direct clinical implications. The circulating nurse is responsible for monitoring the sterile field and responding to breaks in technique. When saline soaks through a drape, the appropriate action is to cover the wet area with a sterile impermeable drape or, if the table surface is involved, to replace the entire setup. The instrument table is a critical sterile area, so any strike-through there requires prompt intervention.

The other options are incorrect because they misidentify the mechanism. Wet areas do not primarily become contaminated by attracting airborne microbes, and the drape's protective function is not based on an antimicrobial coating that saline would dissolve. Saline poured from a bottle remains sterile at the moment of pouring; the contamination occurs only after the fluid contacts the nonsterile surface below and is drawn back upward through the fabric.