Monitor atlas: perioperative cardiac events
Stem
Monitors station, scenario 1 of 3. The card reads: a 68-year-old man, 92 kg, with three-vessel coronary disease, under general anesthesia for open abdominal aortic aneurysm repair. The clip shows lead V5 and an arterial trace. The monitor shows:
Question
What is the most likely diagnosis, and what is your management?
Ideal answer
What the monitor showed: lead V5, sinus rate rising from 72 to 118, new 2 mm horizontal ST depression, pressure steady at 150/85.
HeadlineSubendocardial ischemia driven by tachycardia: demand has outrun supply across fixed coronary lesions. I slow the rate, hold the pressure and give 100% oxygen.
- Same order every clip: rhythm, rate, pressure, waveform shape, then the trend; here a narrow QRS.
- Arterial line: number, upstroke slope, dicrotic notch, and swing with ventilation, showing damping, contractility and volume responsiveness.
- Then a 12-lead, and nitroglycerin if the pressure allows.
- Central or PA trace: pressures and components, then the abnormal wave, naming the lesion.
Watch for: ST returning to baseline as the rate falls.
Breaking down the answer
| Pattern | Identifying features | What it changes |
|---|---|---|
| ST depression, lead V5 | Horizontal or downsloping ST ≥1 mm, rate often high | Subendocardial ischemia; rate down, pressure up, 100% oxygen, 12-lead, nitroglycerin |
| ST elevation, lead II | Convex elevation ≥1 mm, reciprocal depression | Transmural ischemia, coronary air or spasm; cardiology, aspirin, heparin discussed with surgeon |
| Ventricular fibrillation | Chaotic, no QRS, pulse oximeter pleth lost | Defibrillate at the manufacturer's energy (typically 120–200 J biphasic), CPR, epinephrine 1 mg every 3–5 min1 |
| Monomorphic ventricular tachycardia | Wide regular QRS >120 ms, rate >100 | Pulse present: amiodarone 150 mg over 10 min or synchronized cardioversion; pulseless: shock |
| Torsades de pointes | Twisting polymorphic QRS, long QT on prior strip | Magnesium 2 g IV, stop QT-prolonging drugs, overdrive pacing |
| Atrial fibrillation with rapid response | Irregularly irregular, no P waves, rate >100 | Unstable: cardiovert; stable: beta-blocker or diltiazem, rate control to <110 |
| Complete heart block | P waves and QRS independent, slow ventricular escape | Atropine rarely works; pacing, epinephrine or dopamine infusion |
| Hyperkalemia | Peaked T, wide QRS, loss of P, sine wave | Calcium chloride 1 g, insulin 10 units with dextrose, bicarbonate, hyperventilation |
| Tamponade on CVP | CVP rises, arterial pulse pressure narrows, pulsus paradoxus >10 mmHg | Fluid, rate up, no positive-pressure surge, drain |
| Right ventricular failure | CVP climbs, PA pressure climbs then falls as output fails, arterial pressure falls | Inotrope, pulmonary vasodilator, avoid further fluid |
| PA catheter wedge | PA trace changes to an a-c-v venous pattern on balloon inflation | Large v wave means mitral regurgitation or ischemic papillary muscle |
| Overwedging | Trace climbs steadily without a venous pattern | Deflate the balloon immediately; risk of PA rupture |
| Arterial line dampening | Slurred upstroke, lost notch, narrow pulse pressure | Flush, check bubbles or kinks; not hypotension |
| Pulse pressure variation | Arterial trace swings >13% with the ventilator | Fluid responsive, if sinus rhythm and tidal volume 8 mL/kg |
- Highest stakes — a rhythm strip, arterial trace, PA or CVP waveform, or a wedge, cardiac output or mixed venous saturation value,2 one minute to name, explain and act.
- The lead matters — the ECG runs continuously from the start of every anesthetic;3 V5 catches most intraoperative ischemia, lead II inferior ischemia and rhythm.
- The PA waveform locates the catheter — right atrium 0–8 mmHg, right ventricle 25/0–5, pulmonary artery 25/10 with a dicrotic notch, wedge 6–12 with a venous pattern; a persisting RV trace means it coiled back.
- A pressure I do not believe gets a pulse check — VF with a normal arterial trace is artifact; patient check before any shock. In an arrest, an arterial waveform or an abrupt ETCO2 rise after a shock shows return of circulation.1
Follow-up question
The second clip continues, now with a CVP trace. The monitor now shows:
What is happening now, and what do you do?
Follow-up answer
What the monitor showed: rate 118 with persisting ST depression; pressure falling to 70/42, CVP rising 8 to 18, pleth weakening.
HeadlineIschemia has progressed to acute pump failure: rising filling pressure with falling output is cardiogenic shock, and I tell the surgeon to stop.
100% oxygen, epinephrine or norepinephrine for coronary perfusion pressure, cardiology, an intra-aortic balloon pump considered; no fluid to a full heart. The alternative inject, a balloon left inflated on the PA trace, is overwedging: deflate.
Pitfalls that cost points
- Shocking a strip without confirming there is no pulse.
- Reading the number on an obviously dampened arterial trace.
Rapid-fire
Q: Why does ST depression appear in V5 first? A: V5 overlies the most left ventricular subendocardium, which has the lowest perfusion reserve when demand rises.
Q: What is the first drug for torsades? A: Magnesium 2 g IV whatever the serum level; it suppresses the early afterdepolarizations driving it.
Q: How do I tell a wedge trace from an overwedged one? A: A true wedge shows a venous a-c-v pattern below PA diastolic; overwedging climbs without one.
Q: Why does pulsus paradoxus appear in tamponade? A: Inspiration fills the RV, shifting the septum into an LV that cannot expand against the fluid, so systolic pressure falls more than 10 mmHg.
Numbers to know
| Item | Value |
|---|---|
| Ischemic ST change | ≥1 mm, 60–80 ms after the J point |
| Defibrillation | Manufacturer's dose, typically 120–200 J biphasic1,4 |
| Magnesium, torsades | 2 g IV over 2–15 min |
| Normal PA pressure | ~25/10 mmHg, mean 15 |
| Normal wedge | 6–12 mmHg |
Links
- The monitors and echo station: format and timing, Perioperative myocardial ischemia and infarction, Cardiac tamponade, including post-cardiac surgery, Pulmonary artery catheter: indications, waveforms, complications, ACLS adapted to the operating room, Intraoperative cardiac arrest: care after return of circulation
- Atlas: Monitor atlas: perioperative respiratory events; Monitor atlas: other perioperative and peripartum events
- AHA CPR and ECC guidelines (2025), adult ALS
Sources
- 1.Part 9: Adult Advanced Life Support (2025 AHA Guidelines for CPR and ECC) · AHA (Circulation 2025, PMID 41122884), 2025 · cpr.heart.orgReplaces the 2020 Part 3 citation (2026-11-02). Same source and claims as acls-in-the-or (ETCO2 at least 10, ideally 20 mmHg or more; abrupt rise suggests ROSC; epinephrine 1 mg every 3-5 min; manufacturer's biphasic energy). cpr.heart.org returned 403 to this session's fetcher; existence of the 2025 Part 9 confirmed in Europe PMC.
- 2.OSCE Content Outline · ABA · theaba.org
- 3.Standards for Basic Anesthetic Monitoring · ASA, 2025 · asahq.orgLast amended October 15, 2025; Standard II, circulation.
- 4.2025 Korean Guidelines for Cardiopulmonary Resuscitation: Part 4. Adult advanced life support · Korean Association of Cardiopulmonary Resuscitation (Clin Exp Emerg Med 2026), 2026 · europepmc.orgFull text read; corroborates: biphasic 120-200 J (200 J if the manufacturer dose is unknown); ETCO2 below 10 mmHg means improve compressions, target 20 mmHg or more; abrupt rise to 30-40 mmHg prompts a check for ROSC.
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.