Module 3 · Operating Room Environment and Preparation
Lesson 3.1 — Operating Room Setup
OR set up accounts for all 19 Preoperative Preparation items on the CST exam. Master this lesson, and you will be answering those questions with confidence — not guessing.
📋 NBSTSA Blueprint Coverage: Perioperative Care — Preoperative Preparation (19 items)
🎯 High-Yield Exam Topics in This Lesson
Surgeon’s preference card · OR traffic zones (restricted / semi-restricted / unrestricted) · Environmental controls (temperature 68–75°F, humidity 20–60%) · Sterile package integrity checks · Order of OR setup steps · Surgical scrub sequence · Mayo stand vs. back table · ESU grounding pad placement · Initial instrument/sponge/needle counts
1. The Surgeon’s Preference Card
The surgeon’s preference card is the starting point for every OR setup. It is a document — maintained in the hospital’s computer system or as a hard copy — that lists one surgeon’s specific preferences for a given procedure: instruments, sutures, glove size, special equipment, medications on the sterile field, positioning devices, and skin prep solutions.
What the Preference Card Contains
| Category | Examples |
|---|---|
| Instruments & Sets | Laparotomy set, vascular set, specialty retractors |
| Sutures & Needles | Type, size, and quantity (e.g., 0-Vicryl on CT-1, 4-0 Prolene on RB-1) |
| Medications & Solutions | Heparin, epinephrine, irrigation solutions, thrombin |
| Patient Positioning | Supine, lateral, prone; specific positioning devices |
| Skin Prep Solution | Betadine, ChloraPrep (chlorhexidine), DuraPrep |
| Glove Size & Draping | Surgeon and assistant glove sizes; specific drape configuration |
⚠️ CST Exam Alert: The CST tests your understanding that the preference card drives setup — but it must be verified against current case needs, not followed blindly. The card should be updated whenever preferences change. This is also an ancillary duty (Domain II).
2. OR Traffic Zones — Know All Three
The surgical suite is divided into three traffic zones that govern movement and attire to reduce the risk of contamination. This is a high-frequency CST exam topic — you must know exactly what belongs in each zone.
🟢 Unrestricted Zone
Location: Entrances, waiting areas, locker rooms, PACU, offices
Attire: Street clothes permitted. No restrictions on who may enter. Patients, family, and non-surgical staff may be present.
🟡 Semi-Restricted Zone
Location: Corridors to ORs, sterile supply storage, instrument processing/sub-sterile areas
Attire: Surgical attire required (scrubs, head covering). Traffic is controlled. Only authorized personnel permitted.
🔴 Restricted Zone
Location: The OR itself and adjacent scrub sink/sterilizer areas
Attire: Surgical attire plus masks are required at all times when sterile supplies are open. Traffic is strictly limited to essential personnel only.
📝 Knowledge Check 1: A nurse manager needs to speak briefly with a circulator during a setup in the OR corridor. Which traffic zone is she entering, and what attire is required?
A. Unrestricted zone — street clothes are acceptable
B. Semi-restricted zone — surgical attire is required
C. Restricted zone — surgical attire plus mask are required
D. Semi-restricted zone — street clothes are acceptable
Reveal Answer
✅ Correct Answer: B
OR corridors are semi-restricted areas. Surgical scrubs and a head covering are required. A mask is only mandatory in the restricted zone (inside the OR when sterile supplies are open). Street clothes are never appropriate in the semi-restricted or restricted zones.
3. OR Environmental Controls
The OR environment must be actively controlled before setup begins. These parameters appear directly in the NBSTSA content outline task: “Prepare the operating room environment (e.g., temperature, humidity, lights, suction, wiping down the room and furniture, managing OR traffic patterns).”
OR Environmental Parameters (ASHRAE Standard 170 / AORN)
| Parameter | Required Range | Why It Matters |
|---|---|---|
| Temperature | 68–75°F (20–24°C) |
Inhibits bacterial growth; prevents patient hypothermia; maintains staff efficiency |
| Relative Humidity | 20–60% | Above 60% → microbial growth, compromises sterile package integrity; below 20% → static electricity, airborne particles |
| Air Changes | ≥15/hour (≥3 fresh air) |
Dilutes airborne contaminants; HEPA filtration required |
| Air Flow Direction | Positive pressure | Air flows OUT of the OR when doors open, preventing contaminated corridor air from entering |
💡 Remember for the Exam: Humidity above 60% is the primary reason sterile packages lose their integrity in storage. The CST must verify environmental conditions are within range before beginning setup. Doors to the OR should remain closed at all times during a case to maintain positive pressure and temperature.
4. Inspecting Sterile Packages — The 5-Point Check
Every package opened onto the sterile field must be inspected before use. A compromised package must be considered contaminated and discarded — never used. The exam tests this as a judgment call, not just a recall fact.
Expiration Date
Check the expiration date on the package label. An expired package may not maintain sterility and must be reprocessed or discarded.
Seal Integrity
Inspect all seals — heat seals on peel pouches and tape on wrapped packs — for breaks, lifting, or separation. Any broken seal = contaminated.
Moisture / Wet Packs
Any evidence of moisture or wet spots on the wrapper indicates potential wicking contamination. A wet pack is a contaminated pack — do not use.
Tears, Holes, or Punctures
Physical damage to any part of the packaging material, including pinholes, abrasions, or instrument puncture, renders the package contaminated.
Chemical Indicator (External)
The external chemical indicator (e.g., sterilization tape or printed indicator on pouch) must show the appropriate color change, confirming the package was exposed to sterilization conditions. Note: this confirms exposure only — not guaranteed sterility (that is the role of the biological indicator).
⚠️ Critical Distinction — CST Exam Favorite: A chemical indicator (Class 1–6) confirms exposure to sterilization parameters. A biological indicator (BI) using live spores (Geobacillus stearothermophilus for steam; Bacillus atrophaeus for EtO) is the gold standard to confirm actual sterilization efficacy. The BI is the only definitive proof of sterilization.
5. The Sequential Order of OR Setup
The CST exam tests not just what you do, but in what order. Following the correct sequence maintains sterile technique throughout and is the difference between a safe setup and a contaminated field.
📝 Knowledge Check 2: Sterile supplies for a case have been opened and set up in OR 3. The case is then moved to OR 5. What is the correct action?
A. Cover the sterile field and transport everything to OR 5
B. Dispose of the OR 3 setup; obtain new sterile supplies for OR 5
C. Leave the OR 3 setup for the next case scheduled in that room
D. Move the Mayo stand only; leave the back table in OR 3
Reveal Answer
✅ Correct Answer: B
Once sterile supplies have been opened and set up in a room, they cannot be transported to another room without compromising sterility. The OR 3 setup must be disposed of and a fresh setup must be opened in OR 5. The next case in OR 3 also cannot use the abandoned setup — contamination is assumed when a sterile field is unattended. This is a classic CST exam scenario question.
6. Back Table vs. Mayo Stand — Know the Difference
The CST exam distinguishes clearly between these two sterile surfaces. Knowing which instrument goes where — and why — is tested directly.
🗂️ BACK TABLE
Location: Behind the patient; off to the side of the surgical field
Contents: All instruments, supplies, sutures, sponges, and medications for the entire procedure
Role: Reserve supply — the CST pulls from here to replenish the Mayo stand as needed
🩺 MAYO STAND
Location: Positioned directly over or near the patient at the sterile field
Contents: Only the instruments and supplies needed for the immediate next steps of the procedure
Role: Active working surface — passed directly to the surgeon and first assistant
💡 Secondary Mayo Stand: For complex cases or when heavy contamination is anticipated (e.g., bowel surgery), a secondary Mayo stand may be set up to avoid cross-contamination between clean and potentially contaminated instruments. This is explicitly listed in the NBSTSA content outline.
7. Key Equipment Setup — Tested Items
⚡ Electrosurgical Unit (ESU) / Bovie
The ESU dispersive pad (grounding pad / bovie pad) must be placed on the patient before use — over a well-vascularized, fleshy muscle mass, away from bony prominences, implants, ECG electrodes, and the operative site. Exam tip: The return electrode (dispersive pad) is placed by the circulator, not the scrub tech. Never place over scar tissue, tattoos, or metal implants.
🔦 Surgical Lighting
Shadowless surgical lights are positioned and focused before the patient is draped. Sterile light handles or covers are applied by the scrubbed CST so lights can be repositioned intraoperatively without breaking sterile technique.
🫧 Suction
Suction tubing is connected, tested, and secured. The suction tip (e.g., Yankauer, Frazier, Poole) is passed to the scrub tech and connected to the sterile field tubing. Test suction function before the patient is positioned.
🛏️ OR Table
Positioned, adjusted, and accessorized per surgeon specifications (arm boards, leg stirrups, kidney rests, bean bag). Safety strap (restraint strap) must be applied across the patient’s thighs — 2 inches above the knees — after transfer. The grounding pad is also coordinated with OR table setup.
🩺 Sequential Compression Devices (SCDs)
SCDs are applied to the patient’s lower extremities before or after positioning to prevent deep vein thrombosis (DVT). Must be connected and operational before the procedure begins. Also on the preference card.
8. Initial Counts — Before the First Incision
Counts are performed jointly by the scrub tech and the circulator — both must see and verbally confirm each item. Counts are documented in the OR record. This is one of the highest-tested intraoperative topics on the CST exam.
What Is Counted & When
| Counted Item | Details | When Counted |
|---|---|---|
| Sponges | Radiopaque thread embedded for X-ray detection; counted in groups of 5 or 10 | Initial, before closure, at skin closure, anytime a sponge is added |
| Sharps & Needles | Every needle, knife blade, hypodermic needle counted and tracked on needle board | Initial, before closure, at skin closure |
| Instruments | All instruments on the sterile field; must match the count sheet | Initial, before closure, at skin closure |
⚠️ Incorrect Count Protocol: If a count is incorrect at closure, the surgeon must be notified immediately. The wound must not be closed until the discrepancy is resolved. An X-ray is taken if the item cannot be located. Never close on an incorrect count — this is a patient safety absolute.
📝 Knowledge Check 3: At the closing count, the sponge count is incorrect. The surgeon says the wound looks clear and instructs the team to proceed with closure. What should the scrub tech do?
A. Defer to the surgeon’s clinical judgment and assist with closure
B. Document the discrepancy and proceed with closure
C. Report the incorrect count to the circulator; an intraoperative X-ray should be obtained before closure
D. Recount only the sponges and dismiss the discrepancy if it cannot be found
Reveal Answer
✅ Correct Answer: C
An incorrect count is a patient safety emergency — it cannot be dismissed at the surgeon’s request. The circulator must be notified, the entire team must search the field and room, and an intraoperative X-ray must be obtained before wound closure. The surgeon’s instruction to proceed does not override protocol. This principle protects both the patient and the surgical team from liability.
9. Medications and Solutions on the Sterile Field
All medications and solutions on the sterile field must be verified, received, mixed, and labeled correctly. This is explicitly named in the NBSTSA content outline and is one of the most error-prone areas in the real OR — making it a favorite exam topic.
Medication Handling Protocol — The Four Steps
The scrub tech and circulator verbally confirm the drug name, concentration, and expiration date — both before the circulator pours/passes and after the scrub tech receives it
The circulator pours medications into labeled containers on the sterile field — the vial label is always shown to and read by the scrub tech simultaneously
The scrub tech mixes solutions per the surgeon’s order using sterile technique (e.g., diluting epinephrine into saline, mixing thrombin with thrombin sponge)
Every container on the sterile field must be labeled immediately — even if only one solution is on the field. Labels must include drug name, strength/concentration, and diluent if applicable. An unlabeled container must be discarded.
⚠️ CST Exam Alert: An unlabeled container on the sterile field must be discarded — it can never be used, regardless of what is known or assumed about its contents. This is absolute. The exam will offer “use it if you know what it is” as a distractor — always choose discard.
📝 Knowledge Check 4: The OR temperature is recorded at 77°F (25°C) during setup. What is the correct action?
A. Proceed with setup — the temperature is within normal range
B. Notify the charge nurse; the temperature is above the acceptable range of 68–75°F
C. Proceed; temperature only matters during the case, not during setup
D. Open the OR doors to reduce the temperature before beginning
Reveal Answer
✅ Correct Answer: B
77°F exceeds the ASHRAE/AORN acceptable OR temperature range of 68–75°F. The CST must report this to the charge nurse or facility engineering — do not proceed and do not self-correct by opening doors (opening OR doors disrupts positive pressure airflow and introduces contamination). Option D is tempting but wrong: opening OR doors violates the positive-pressure ventilation requirement. Always use the chain of command for environmental deviations.
⚡ Rapid Review — High-Yield Facts
You’ve Completed Lesson 3.1
OR setup is the foundation of every safe surgical procedure. Master these principles and you are ready to answer every Preoperative Preparation question the CST exam can throw at you.
Next: Lesson 3.2 — Preoperative Documentation