📚 Guideline basis
Sarfati et al. on continuous miniaturised TEE in the ICU (Anaesth Crit Care Pain Med 2021, PMID 33887587); Mayo PH, et al. on ICU TEE (Chest 2017, PMID 26252890); ESICM 2025 recommendations on haemodynamic monitoring in shock; Vieillard-Baron A, et al. on SVC collapsibility (Intensive Care Med 2004).
> ⚠️ Evidence quality
> Feasibility, safety and physiological validity of miniaturised continuous TEE are established in observational cohorts. No randomised trial has demonstrated an outcome benefit from its use. This chapter describes a technique with a defensible physiological rationale and an unproven effect on mortality, and should be read as such.
The rationale
Conventional echocardiography samples a physiology that changes continuously. A patient in septic shock is scanned at 08:00, receives fluid, vasopressor titration and a ventilator change, and is scanned again at 16:00 — during which time the loading conditions have moved through a range wider than the difference the study was intended to detect. The mismatch between the sampling rate of the instrument and the time constant of the process is the fundamental limitation of intermittent echocardiography as a monitor.
Two responses exist. The first is disciplined serial TTE, repeating a focused haemodynamic set before and after every major intervention (Chapters 11, 12, 28). The second is an indwelling miniaturised transoesophageal probe that can be reconnected and imaged in seconds, without re-instrumentation.
Device characteristics
Feature | Typical specification |
Probe diameter | Substantially smaller than a conventional TEE probe (of the order of 5–6 mm shaft), designed for prolonged indwelling use |
Dwell time | Licensed for continuous placement, typically up to 72 hours, device-dependent |
Imaging planes | A restricted view set — commonly mid-oesophageal four-chamber, mid-oesophageal long axis, and transgastric short axis |
Doppler | Device-dependent; some platforms provide colour and spectral Doppler, others 2D only |
Insertion | As for conventional TEE, in the intubated, sedated patient |
Manipulation | Limited flexion controls; the trade-off for the reduced diameter |
The imaging capability is deliberately narrower than a full TEE. It is a monitor, not a diagnostic study, and it does not replace a comprehensive examination.
Clinical applications
Application | What continuous imaging adds |
Titration of fluid and vasoactives in shock | Immediate re-assessment of LV filling, septal position and (where Doppler is available) LVOT VTI after each intervention |
Serial RV assessment in ARDS | Acute cor pulmonale is dynamic and responds within minutes to changes in driving pressure, PEEP and PaCO₂; the transgastric short-axis view shows septal shape continuously (Chapter 32) |
During prone positioning | Transthoracic imaging is generally unobtainable in the proned patient; an indwelling probe permits RV monitoring through the turn and the proning period |
Post-cardiotomy monitoring | Poor transthoracic windows are the norm; early detection of tamponade, RV failure or graft-related regional dysfunction (Chapter 36) |
Weaning assessment | Continuous imaging through a spontaneous breathing trial captures the transition physiology that a before-and-after study misses (Chapter 34) |
Mechanical circulatory support | Cannula position, LV distension, aortic valve opening frequency during flow changes (Chapter 35) |
The haemodynamic view set
Even with a restricted probe, a coherent haemodynamic assessment is available:
Question | View | Finding |
Is the LV underfilled? | TG mid short axis | End-systolic cavity obliteration, small end-diastolic area |
Is the LV contracting? | TG mid short axis, ME four-chamber | Fractional area change, visual estimate |
Is the RV overloaded? | TG mid short axis, ME four-chamber | Septal flattening with systolic dyskinesia; RV:LV area ratio |
Is the patient fluid responsive? | ME bicaval (where available) | SVC collapsibility ≥ 36% |
What is the forward flow? | Deep TG long axis (where the device permits) | LVOT VTI |
Is there an effusion? | ME four-chamber, TG | Pericardial collection, chamber compression |
Is filling pressure high? | Pulmonary venous flow, interatrial septal position | S/D ratio; septum bulging right implies LAP > RAP |
SVC collapsibility deserves emphasis. Because the superior vena cava is intrathoracic, it collapses during positive-pressure inspiration in a preload-responsive patient and is unaffected by intra-abdominal pressure — the dominant confounder of the IVC. A collapsibility index ≥ 36% predicts fluid responsiveness with better specificity than IVC distensibility, and it is only obtainable transoesophageally.
Safety of prolonged placement
The risks of an indwelling probe differ from those of a single diagnostic study:
Risk | Mechanism | Mitigation |
Oesophageal pressure injury | Sustained contact between a fixed probe and the mucosa, aggravated by hypotension and vasopressor use | Periodic repositioning; avoid sustained flexion; limit total dwell time to the licensed maximum; maintain perfusion pressure |
Bleeding | Mucosal trauma with coagulopathy | Assess coagulation before insertion; low threshold for removal |
Displacement of the endotracheal tube | During insertion or repositioning | Verify tube position after every manipulation |
Infection / cross-contamination | Reprocessing failure | High-level disinfection; leak testing; probe tracking |
Sedation burden | The probe requires the patient to remain intubated and adequately sedated | Do not extend sedation solely to retain the probe |
Published cohorts report low complication rates, but the studies are observational, single-centre, and enrol selected patients. The absence of a signal in small cohorts is not the same as demonstrated safety over long dwell times in coagulopathic patients.
When continuous TEE is not the answer
- When the question is structural rather than haemodynamic. A restricted view set will not exclude endocarditis, dissection, or prosthetic regurgitation; a full TEE is required.
- When transthoracic windows are adequate. Disciplined serial TTE is non-invasive, costs nothing, and answers most haemodynamic questions.
- When the patient is being weaned toward extubation. The probe mandates continued intubation and sedation, and the monitoring benefit rarely justifies extending either.
- When no protocol exists for acting on the findings. A monitor that does not change a decision imposes only risk.
Integration with other monitoring
Continuous TEE and continuous cardiac output monitoring answer different questions and are complementary rather than competing:
Modality | Strength | Blind to |
Continuous TEE | Mechanism — why the output is low; RV, tamponade, valve, filling, septal interaction | Absolute flow trending between assessments |
Pulse contour / thermodilution | Continuous flow trend; response to intervention in real time | Mechanism; RV; structural cause |
Venous congestion ultrasound | Downstream consequence of the haemodynamics | Cardiac cause |
The ESICM 2025 recommendations position echocardiography as a first-line haemodynamic assessment tool in shock while retaining continuous monitoring for trending — an explicitly multimodal framework rather than a choice between instruments.
🛑 Critical pitfall: Treating a miniaturised probe study as a diagnostic echocardiogram. The restricted view set and limited Doppler mean structural pathology is neither excluded nor graded. Report it as a monitoring study.
🛑 Critical pitfall: Leaving a probe in place beyond the licensed dwell time or in a persistently hypotensive, high-dose-vasopressor patient. Mucosal perfusion is already compromised, and sustained probe contact is the mechanism of pressure necrosis.
🛑 Critical pitfall: Maintaining sedation and intubation in order to keep the monitor. The monitor exists to serve the patient's trajectory, not the reverse.
- 💡 Clinical pearl: The transgastric mid short-axis view is the highest-yield continuous image in the ICU: LV filling, LV contraction and RV loading in one plane, interpretable in seconds by any member of the team.
- 💡 Clinical pearl: SVC collapsibility from the bicaval view is the reason to reach for TEE in a ventilated patient with equivocal fluid-responsiveness data — it is unaffected by intra-abdominal pressure.
- 💡 Clinical pearl: Record the loading conditions with each continuous assessment as rigorously as with a formal study. Continuous monitoring generates many data points, and undated, uncontextualised images are worse than none.
References
- Sarfati et al. Continuous miniaturised transoesophageal echocardiography in critically ill patients. Anaesth Crit Care Pain Med 2021. PMID 33887587.
- Mayo PH, Narasimhan M, Koenig S. Transesophageal echocardiography in the intensive care unit. Chest 2017. PMID 26252890.
- Vieillard-Baron A, Chergui K, Rabiller A, et al. Superior vena caval collapsibility as a gauge of volume status in ventilated septic patients. Intensive Care Med 2004;30:1734–9.
- ESICM. 2025 recommendations on haemodynamic monitoring in shock. Intensive Care Med 2025.
- Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination. J Am Soc Echocardiogr 2013;26:921–64.