Module 5 · Intraoperative Procedures II: Clinical Management
Lesson 5.3 — Surgical Emergencies
The NBSTSA content outline explicitly tests the CST’s ability to recognize an intraoperative emergency and perform appropriate actions during one. These are low-frequency, high-consequence events — the exam relies heavily on scenario questions here because recognizing the pattern matters more than memorizing isolated facts.
📋 NBSTSA Blueprint: Domain I-B · Intraoperative Procedures · Tasks 22-23: Observe patient’s intraoperative status · Perform appropriate actions during an emergency
🎯 High-Yield Topics — What Gets Tested
Malignant hyperthermia — trigger agents, earliest sign, dantrolene mechanism and reconstitution · MH cart contents · Anaphylaxis — latex as the classic intraoperative trigger, timing and presentation · Venous air embolism — mill wheel murmur, sitting/beach chair position risk, Durant’s maneuver · Trendelenburg vs. left lateral decubitus for VAE · Flooding the field with saline · Cardiac arrest in the OR — CST’s specific role · The CST’s universal first action in any OR emergency
1. Malignant Hyperthermia — The Highest-Yield OR Emergency
Malignant hyperthermia (MH) is a rare, life-threatening, inherited hypermetabolic reaction triggered by specific anesthetic agents in genetically susceptible individuals. Because it is dramatic, mechanistically clear, and has one specific antidote, it is one of the most reliably tested surgical emergencies on the CST exam.
The Mechanism
In susceptible individuals (an inherited mutation in the ryanodine receptor (RYR1) on skeletal muscle), exposure to a triggering agent causes uncontrolled release of calcium from the sarcoplasmic reticulum inside muscle cells. This causes sustained, uncontrolled muscle contraction — generating massive heat, oxygen consumption, and carbon dioxide production faster than the body can compensate.
Triggering Agents
Volatile inhalation anesthetics: sevoflurane, desflurane, isoflurane
Depolarizing muscle relaxant: succinylcholine
Non-Triggering / Safe Agents
Propofol, nitrous oxide, non-depolarizing muscle relaxants, and regional/local anesthesia are considered MH-safe. Known or suspected MH-susceptible patients receive a “trigger-free” anesthetic plan.
💡 The Earliest and Most Reliable Sign: Unexplained rising end-tidal CO₂ (hypercarbia) despite increased minute ventilation is the earliest and most consistent indicator of MH — it typically appears before temperature rises significantly. Fever is a LATE sign, not the initial clue — this is a frequently tested distinction. Other early/associated signs: unexplained tachycardia, masseter muscle rigidity (especially after succinylcholine), generalized muscle rigidity, tachypnea.
MH Treatment — What the CST Must Know
Stop all triggering agents immediately. The anesthesia provider discontinues volatile gas and switches the breathing circuit.
Declare the emergency. The team calls for help; the surgeon is asked to complete or terminate the procedure as quickly as safely possible.
Administer dantrolene — the only specific treatment. Dantrolene inhibits calcium release from the sarcoplasmic reticulum, directly reversing the mechanism. Initial dose 2.5 mg/kg IV, repeated as needed.
Cool the patient. Cold IV fluids, ice packs to groin/axilla, cold body cavity lavage if open.
Support the patient. 100% oxygen at high flow, hyperventilation, treat hyperkalemia and arrhythmias as needed.
💡 The CST’s Role — Dantrolene Reconstitution: Dantrolene is supplied as a powder that must be reconstituted with sterile water — each 20mg vial is dissolved in 60mL of sterile water and shaken until clear. Because dantrolene is difficult and time-consuming to mix, an MH cart with a large stock of vials and personnel dedicated to mixing it is standard practice — every OR should have immediate access to at least 36 vials. The scrub tech or a designated team member may be tasked with mixing dantrolene rapidly while the anesthesia provider manages the airway and administers the drug. Every second counts — this is a genuine “all hands” emergency.
📝 Knowledge Check 1: During a case using sevoflurane, the anesthesia provider notes the patient’s end-tidal CO₂ has risen sharply despite increasing the ventilation rate, and the heart rate has climbed unexpectedly. The patient’s temperature is still normal. What should the team suspect?
A. Nothing concerning yet — malignant hyperthermia cannot be suspected until fever develops
B. Early malignant hyperthermia — rising ETCO2 and tachycardia are the earliest reliable signs; fever is a late finding
C. Anesthesia machine malfunction — this is a mechanical issue, not a patient emergency
D. Normal response to surgical stress — continue monitoring without intervention
Reveal Answer
✅ Correct Answer: B
Unexplained, rapidly rising ETCO2 despite increased ventilation combined with unexplained tachycardia are the earliest and most reliable indicators of malignant hyperthermia — occurring in a patient exposed to a known triggering agent (sevoflurane, a volatile anesthetic). Fever is a late sign; waiting for temperature elevation before suspecting MH (option A) delays life-saving treatment. This exact “normal temperature, abnormal ETCO2 and heart rate” presentation is the classic CST exam trap designed to test whether students understand the true early warning signs versus the popularly assumed hallmark (fever).
2. Anaphylaxis — The Latex Connection
Anaphylaxis is a severe, rapid-onset, systemic IgE-mediated allergic reaction. In the OR context, the CST exam most frequently tests this in connection with latex allergy — a topic already covered in Lesson 3.2 that reappears here from the intraoperative crisis-response angle.
Presentation
Sudden hypotension, tachycardia, bronchospasm (wheezing, rising airway pressures), skin flushing/urticaria, and facial or airway edema. Under general anesthesia, the classic visible skin signs may be masked or delayed — the anesthesia provider often recognizes it first through unexplained hypotension and rising airway pressure, then confirms it once a rash becomes visible.
Common Intraoperative Triggers
Latex (gloves, catheters, tourniquets) — the classic CST exam trigger, especially in high-risk patients (spina bifida, multiple prior surgeries, healthcare workers). Also: neuromuscular blocking agents, antibiotics (especially penicillins/cephalosporins), chlorhexidine, blood products, and IV contrast.
Treatment Priorities
Epinephrine is the first-line treatment — reverses vasodilation and bronchospasm. Also: stop the suspected trigger immediately (remove latex products from the field), 100% oxygen, IV fluids for hypotension, antihistamines and corticosteroids as secondary measures. Removing the causative agent is a critical, often-overlooked first action the CST is positioned to help with — if latex gloves are suspected, the entire team changes to non-latex gloves and all latex products are removed from the field immediately.
📝 Knowledge Check 2: Twenty minutes into a case, the anesthesia provider notes sudden, unexplained hypotension and rising peak airway pressures. No skin changes are yet visible because the patient is fully draped. The circulator recalls that the patient’s chart flagged a latex sensitivity that was not clearly confirmed preoperatively. What is the most appropriate immediate action?
A. Wait for visible skin changes to confirm anaphylaxis before taking action
B. Treat as suspected anaphylaxis now — administer epinephrine per anesthesia direction and remove all latex products from the field immediately
C. Continue the case as planned since the latex allergy was never formally confirmed
D. Ask the surgeon to pause and obtain verbal consent from the family before treating
Reveal Answer
✅ Correct Answer: B
Under general anesthesia and full drapes, classic skin signs of anaphylaxis (urticaria, flushing) are frequently masked or delayed. Waiting for visible confirmation (option A) wastes critical time in a rapidly progressing emergency. Given the hemodynamic presentation (hypotension, rising airway pressures) combined with a flagged — even if unconfirmed — latex sensitivity, the team should treat this as suspected anaphylaxis immediately: administer epinephrine per anesthesia’s direction and remove latex products from the field as a precautionary and potentially causative intervention. This is a genuine emergency — there is no role for obtaining additional consent (option D) mid-crisis.
3. Venous Air Embolism (VAE)
Venous air embolism occurs when air enters the venous circulation through an open vein during surgery — most classically during procedures where the operative site is positioned above the level of the heart, creating negative venous pressure that can draw air into open veins.
Highest-Risk Procedures and Positions
Craniotomy in the sitting or semi-sitting position (the classic exam scenario — connect this to Lesson 3.4’s Fowler’s/beach chair position and its risk of air embolism), posterior fossa neurosurgery, shoulder arthroscopy in beach chair position, laparoscopic procedures using CO₂ insufflation, and central venous catheter placement/removal.
⚠️ The Classic Sign — “Mill Wheel” Murmur
A distinctive churning, splashing heart sound (the “mill wheel murmur”) heard on auscultation when a significant volume of air becomes trapped in the right ventricle. This is a hallmark finding tested directly by name on the CST exam. Other signs: sudden unexplained hypotension, hypoxia, decreased end-tidal CO₂ (air displaces blood in the pulmonary circulation, reducing CO₂ return to the lungs), and cardiovascular collapse in severe cases.
VAE Management — Positioning Is Central
Alert the surgeon immediately and flood the operative field with saline or apply saline-soaked sponges over the source to prevent further air entrainment through open veins.
Position the patient using Durant’s maneuver: left lateral decubitus combined with Trendelenburg positioning. This traps air in the right atrium/ventricle away from the right ventricular outflow tract, preventing it from traveling into the pulmonary artery and causing an air lock.
100% oxygen is administered — this both maximizes patient oxygenation and helps reduce nitrogen content in the trapped air bubble, aiding reabsorption.
Aspirate air via an existing central venous catheter if one is already in place. Hemodynamic support with fluids and vasopressors as needed. CPR if cardiovascular collapse occurs.
💡 Why Left Side Down? Positioning the patient on their left side keeps the right ventricular outflow tract (which sits more superiorly and toward the patient’s left/anterior in this position) elevated above the pooled air, allowing air to remain trapped in the lower, dependent right atrium/ventricle rather than being ejected into the pulmonary circulation. This is the mechanical logic behind Durant’s maneuver — understanding “why” lets you answer any phrasing of this question.
📝 Knowledge Check 3: During a posterior fossa craniotomy performed with the patient in the sitting position, the anesthesia provider suddenly hears a churning “mill wheel” sound on precordial monitoring, and the patient’s blood pressure drops sharply. What is suspected, and what immediate positioning change should be anticipated?
A. Malignant hyperthermia — the patient should be actively cooled
B. Venous air embolism — the patient should be repositioned to left lateral decubitus with Trendelenburg (Durant’s maneuver)
C. Anaphylaxis — latex products should be removed from the field
D. Malignant hyperthermia — the patient should be placed in reverse Trendelenburg
Reveal Answer
✅ Correct Answer: B
This scenario contains three classic VAE identifiers: (1) the sitting position for a posterior fossa craniotomy — the highest-risk position and procedure combination, (2) the mill wheel murmur — the pathognomonic sign of significant air entrainment in the right heart, and (3) sudden hypotension. The correct positioning response is Durant’s maneuver — left lateral decubitus combined with Trendelenburg — to trap the air away from the right ventricular outflow tract. This question tests the connection between positioning (Lesson 3.4), procedure type, and this specific emergency, exactly as the exam layers content across lessons.
4. Cardiac Arrest in the OR — The CST’s Role
Cardiac arrest can be the endpoint of any of the emergencies above, or occur independently. The CST exam tests the scrub tech’s specific, defined role during a code — not the full ACLS algorithm, which belongs to anesthesia and the code team.
Maintain the sterile field if at all possible. If the surgical wound is open, the sterile field must be protected — the case may need to continue or be rapidly closed depending on the surgeon’s decision. The scrub tech does not abandon the field reflexively.
Anticipate the surgeon’s needs — internal cardiac massage instruments, emergency thoracotomy trays, or rapid closure supplies may be required depending on the situation and surgical approach.
Stay out of the way of the code team while remaining ready to hand off instruments or supplies as directed. Chest compressions and defibrillation are managed by anesthesia and the code team, not the scrub tech.
Maintain counts throughout, even during a code — items are still tracked; a code does not suspend the requirement to account for sponges, sharps, and instruments once stability returns and closure proceeds.
⚡ Rapid Review — Surgical Emergencies High-Yield Facts
Lesson 5.3 Complete
Surgical emergencies test pattern recognition under pressure — the same skill you will need in the real OR. Malignant hyperthermia is the single most-tested emergency on the exam; know its early signs cold. The mill wheel murmur for VAE and the latex-anaphylaxis connection round out the highest-yield content in this category.
Next: Lesson 5.4 — Specimen Management