Instrument Processing
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Direct answer
Sterilisation succeeds or fails at the cleaning step before it: organic residue shields microbes from steam and chemicals, so processing begins at the operating table with point-of-use pre-cleaning and runs through soaking, washing — manual, enzymatic or ultrasonic — drying, inspection, lubrication and packing before any autoclave is loaded. The depth of processing an item needs is set by the Spaulding classification: critical items entering sterile tissue must be sterilised, semi-critical items touching mucous membranes need at least high-level disinfection, and non-critical items touching intact skin need low-level disinfection. Never let a visibly soiled instrument reach the steriliser.
What you must remember
- Spaulding classification: critical (surgical instruments, implants, needles — sterilisation); semi-critical (endoscopes, cystoscopes, laryngoscope blades — high-level disinfection); non-critical (blood pressure cuffs, stethoscopes — low-level disinfection).
- Point-of-use treatment: wipe gross soil at the table and keep instruments moist with a damp towel or enzymatic spray until washing — dried blood is far harder to remove.
- Cold or lukewarm water first: hot water coagulates protein and fixes blood to surfaces; saline soaking is banned because chloride pits and corrodes stainless steel — a standing viva question.
- Enzymatic cleaners (proteases, amylases, lipases) digest organic soil at low temperature and suit delicate and micro instruments.
- Ultrasonic cleaners work by cavitation — bubbles forming and collapsing at roughly 30–40 kHz — flushing box locks, serrations and lumens brushes cannot reach; they clean, they do not disinfect.
- Washer-disinfectors standardise cleaning and thermal disinfection with validated cycles and controlled drying; baskets must not be overloaded.
- Inspection follows washing: tip alignment, ratchet function, sharpness, cannula patency, insulation testing of laparoscopic and diathermy instruments.
- Water-soluble lubricant ("instrument milk") on hinges only; oil films block steam contact inside lumens.
- Immediate-use steam sterilisation (the old "flash") is for genuine emergencies only, never for implants and never as routine.
A typical processing run after laparoscopic surgery
Follow a laparoscopic set from the moment the port sites close. The scrub nurse flushes the cannulae and wipes the instruments at the table because bile and blood dry within minutes into a film no washer fully removes. In the CSSD dirty zone, disassembly begins — valves, seals and trocar inserts separated, since a clean exterior over a dirty lumen is the classic hidden failure. Cold enzymatic soak loosens remaining protein; ports and graspers pass through ultrasonic cavitation for hinges and jaw serrations, while the optics are cleaned by hand — telescopes never enter an ultrasonic bath, which can degrade lens cementing.
Drying comes next, with forced air through cannulae, because water left inside a lumen returns later as a wet pack. At the inspection bench each grasper is function-tested, and the insulation of every diathermy hook is checked with a tester: a micro-breach can arc into the next patient's bowel — exactly why this step exists. Lightly lubricated, assembled against the count sheet, double wrapped with internal indicators, the set is now genuinely ready for the autoclave. Skip one step and the autoclave faithfully sterilises the surface of whatever dirt remains.
Where students slip
Three errors repeat. Saline: asked how to soak bloody instruments overnight, many answer "normal saline" — the correct answer is cold water or enzymatic solution, because saline rusts instruments. Confusing high-level disinfection with sterilisation: a cystoscope touches mucous membrane, so high-level disinfection with 2 per cent glutaraldehyde or peracetic acid is acceptable — but the same answer applied to a sterile-entry instrument is wrong. Third, believing ultrasonic cleaners sterilise — cavitation only cleans. A subtler trap: immediate-use steam sterilisation is not a shortcut for poor inventory planning, and implants are expressly excluded because monitoring is abbreviated and the item goes straight from cycle to patient.
Frequently asked questions
What does the Spaulding classification dictate?
Critical items entering sterile tissue require sterilisation; semi-critical items contacting mucous membranes require high-level disinfection; non-critical items contacting intact skin require low-level disinfection.
Why should instruments never be soaked in saline?
Chloride ions pit and corrode stainless steel; cold water or enzymatic detergent solution is the correct soaking medium.
How does an ultrasonic cleaner work?
Sound waves around 30–40 kHz generate cavitation bubbles whose collapse dislodges soil from hinges, serrations and crevices — cleaning only, not disinfection.
Why is hot water avoided in initial cleaning?
Hot water coagulates and fixes proteinaceous soil like blood onto instrument surfaces, making complete removal far harder.
Which lubricant is used on surgical instruments?
Water-soluble "instrument milk" on hinges after drying; oil-based lubricants are avoided as they impede steam contact.
When may immediate-use steam sterilisation be used?
Only when an unwrapped, needed-now instrument has no sterile alternative, with full documentation — never for implants, never as inventory policy.