Teach me about advanced monitoring in onco anaesthesia

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anesthesia monitoring AND cancer surgery

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advanced hemodynamic monitoring oncology surgery anaesthesia guideline

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https://pubmed.ncbi.nlm.nih.gov/30074124/

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PMID: 30074124

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intraoperative hemodynamic monitoring AND cancer surgery

Advanced monitoring in onco-anaesthesia

Advanced monitoring is selective, not routine. Its purpose is to detect a problem early enough to change management: occult bleeding, inadequate oxygen delivery, fluid intolerance, myocardial dysfunction, coagulopathy, hypothermia, or ventilation failure.

Cancer patients often have added risk from anemia, malnutrition, chemotherapy-related cardiotoxicity, pulmonary toxicity, renal or hepatic impairment, thrombosis, and the physiology of large resections. The operation matters as much as the diagnosis: thoracic surgery, cytoreductive surgery with HIPEC, hepatic resection, major pelvic surgery, free-flap head-and-neck surgery, and tumor surgery involving major vessels may all justify escalation.

All patients still receive standard monitoring: ECG, non-invasive BP, SpO2, capnography, inspired oxygen, airway-pressure monitoring, temperature when indicated, and neuromuscular monitoring when relaxants are used. The ASA lists its current basic monitoring standards.

1. Invasive arterial pressure monitoring

An arterial catheter is usually the first advanced monitor to consider.

Useful when

Major expected blood loss or major fluid shifts
Need for frequent ABGs, lactate, hemoglobin, electrolytes, ionized calcium, or coagulation tests
Vasopressor or inotrope infusion
Significant cardiac disease or poorly controlled hypertension
One-lung ventilation, HIPEC, hepatic resection, or prolonged major surgery
Rapidly changing physiology, for example vascular clamping or tumor resection near great vessels

What it provides

Beat-to-beat blood pressure
Arterial waveform quality and response to interventions
Arterial blood sampling

Pitfalls

A normal MAP does not prove adequate cardiac output or tissue perfusion.
Incorrect transducer leveling can produce misleading pressure readings.
Radial pressure can differ from central pressure in severe vasoconstriction or after cardiopulmonary bypass.

In cancer surgery, do not treat every low pressure with fluid. First ask: Is this vasodilation, low preload, impaired contractility, obstruction, hemorrhage, or an artifact?

2. Advanced hemodynamic monitoring and goal-directed therapy

This is particularly relevant for high-risk open abdominal, thoracic, liver, pelvic, and cytoreductive procedures.

What to monitor

Depending on the device and patient:

Cardiac output/cardiac index
Stroke volume and stroke-volume response to a maneuver
Stroke-volume variation (SVV) or pulse-pressure variation (PPV)
Systemic vascular resistance
Central venous oxygen saturation (ScvO2), in selected patients
Lactate trend and serial ABGs

The clinical aim

Optimize oxygen delivery, not just pressure or urine output.

A useful bedside sequence is:

Confirm that the low BP is real.
Assess surgical blood loss and hemoglobin.
Ask whether the patient is likely fluid responsive.
If fluid responsive and fluid tolerant, give a small, reassessed bolus.
If not fluid responsive but vasodilated, use vasopressor.
If cardiac output is inadequate with poor contractility, consider inotropy after echocardiographic assessment if possible.
Recheck the response, not merely the intervention.

Dynamic indices: useful but conditional

SVV and PPV may help predict fluid responsiveness only when their assumptions are reasonably met:

Controlled mechanical ventilation
Regular rhythm
Adequate tidal volume
No major spontaneous effort
No major right-ventricular failure
Ideally closed chest and stable intra-abdominal pressure

They are less dependable in atrial fibrillation, low tidal volume ventilation, open chest surgery, one-lung ventilation, marked pulmonary hypertension, prone positioning with altered compliance, and major changes in intra-abdominal pressure. In those situations, a passive-leg raise is often impractical intraoperatively; a mini-fluid challenge or echo-derived stroke-volume assessment may be more useful.

A before-after study in major open abdominal cancer surgery used predefined targets including MAP above 65 mmHg, SVV below 12%, cardiac index above 2.5 L/min/m², ScvO2 above 70%, and BIS 40-60. It found association with less fluid administration and fewer complications, but it was not a randomized trial, so these numbers should not be used as universal targets. See the study abstract.

Key lesson: advanced monitoring is valuable only if there is a pre-agreed response to each abnormality. A monitor without a treatment algorithm adds numbers, not safety.

3. Central venous catheter and ScvO2

A central venous line is primarily an access device, not a reliable volume-status monitor.

Indications

Vasoactive, inotropic, irritant, or multiple infusions
Poor peripheral access
Anticipated massive transfusion
Need for central venous sampling or selected ScvO2 monitoring
Major operations in which access may become difficult after positioning

What CVP can and cannot do

It may help follow trends and identify grossly elevated right-sided filling pressures.
A single CVP value poorly predicts fluid responsiveness.
“Low CVP anesthesia” may be used in hepatic resection to reduce venous bleeding, but it demands careful coordination between surgeon and anesthetist and rapid readiness to restore circulating volume after parenchymal transection.

ScvO2 A low ScvO2 may signal inadequate oxygen delivery, anemia, hypoxemia, low cardiac output, or high oxygen consumption. A normal or high value does not guarantee adequate microcirculatory perfusion, especially in sepsis or impaired extraction.

4. Perioperative echocardiography: TTE, focused cardiac ultrasound, and TEE

For onco-anaesthesia, focused cardiac ultrasound or TEE often answers the question that arterial pressure cannot:

Is the left ventricle empty, failing, or hyperdynamic?
Is there right-ventricular strain from pulmonary embolism, pulmonary hypertension, hypoxia, or high airway pressures?
Is there pericardial effusion/tamponade?
Is hypotension due to vasodilation, hypovolemia, myocardial ischemia, dynamic LV outflow obstruction, or obstruction to venous return?
Is there a new regional wall-motion abnormality?

TEE is especially helpful during major vascular involvement, severe cardiopulmonary disease, unexplained refractory shock, and surgery with massive fluid/blood shifts.

It should not be routine simply because a case is long. Risks include esophageal injury and bleeding. Extra caution or avoidance is required with known esophageal pathology, prior esophageal surgery or radiation, esophageal tumor, active upper GI bleeding, and significant dysphagia.

The evidence does not establish that routine PAC or TEE improves outcome in every high-risk non-cardiac surgical patient. Selection, interpretation, and a usable treatment response are what determine value. Miller's Anesthesia, 10th ed., p. 7964.

5. Pulmonary artery catheter: a narrow role

A pulmonary artery catheter can provide:

Pulmonary artery pressures
Pulmonary artery occlusion pressure, with important limitations
Continuous/intermittent cardiac output
Mixed venous oxygen saturation
Right-sided hemodynamic data

Consider it when the information is uniquely needed, such as:

Severe pulmonary hypertension
Severe right-ventricular dysfunction
Complex biventricular failure
Selected major vascular or thoracic procedures with anticipated major instability

It is not a default monitor for cancer surgery. It has procedural risks, demands expertise, and should be used only where its results will guide decisions. Miller's Anesthesia, 10th ed., p. 7964.

6. Oxygenation and ventilation monitoring in thoracic oncology

Thoracic cancer operations commonly require one-lung ventilation (OLV).

Beyond SpO2 and capnography, consider:

Arterial line and serial ABGs
Peak, plateau, and driving pressures
Recruitment response and compliance trend
PaCO2 rather than relying only on end-tidal CO2
Careful verification of double-lumen tube or bronchial blocker position, often with bronchoscopy

During OLV, the PaCO2-ETCO2 gradient may widen, so ETCO2 can underestimate arterial CO2. A patient may have SpO2 99-100% before OLV yet have limited oxygen reserve; PaO2 and the P/F ratio give better context. Miller's Anesthesia, 10th ed., p. 7124.

For sudden hypoxemia during OLV, think systematically:

Confirm tube position.
Check FiO2, circuit, and ventilator.
Suction both lumens.
Assess dependent-lung ventilation and recruitment.
Check hemodynamics and cardiac output.
Consider CPAP to the non-dependent lung or intermittent two-lung ventilation if surgical conditions permit.

7. Coagulation and blood-component monitoring

Major cancer surgery can cause bleeding, dilutional coagulopathy, hypofibrinogenemia, thrombocytopenia, hyperfibrinolysis, and electrolyte abnormalities from transfusion.

Useful tests

Serial hemoglobin/hematocrit
Platelet count
PT/INR, aPTT, fibrinogen
Ionized calcium
ABG, pH, base deficit, and lactate
Viscoelastic testing: TEG or ROTEM, when major bleeding is occurring or anticipated

Viscoelastic tests assess whole-blood clot initiation, clot strength, and fibrinolysis. They can support targeted treatment, for example fibrinogen replacement for low clot amplitude consistent with fibrinogen deficit, rather than reflexively giving plasma. They complement rather than fully replace laboratory assays. Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th ed., p. 4797.

Oncology-specific point: cancer patients are also prothrombotic. A bleeding-focused transfusion strategy should not overlook postoperative VTE prevention once hemostasis is secure.

8. Temperature, metabolic, and renal monitoring

Core temperature

Essential for long, open, high-volume, HIPEC, and major thoracoabdominal procedures.

Hypothermia worsens coagulopathy, delays drug metabolism, and increases transfusion risk.
HIPEC can cause rapid hyperthermia, vasodilation, increased metabolic demand, acidosis, and hemodynamic instability. Continuous core temperature plus frequent ABG/electrolyte checks are appropriate.

Metabolic surveillance

For large resections or instability, follow:

Lactate trend
pH and base excess
Potassium
Ionized calcium
Glucose
Hemoglobin

Lactate is a trend marker of impaired oxygen delivery or clearance. It is not synonymous with hypovolemia.

Urine output

Useful as one component of assessment, especially during long abdominal, urologic, or HIPEC surgery, but it is a delayed and non-specific indicator. Do not administer fluid solely to chase urine output when cardiac output, perfusion, and volume status suggest otherwise.

9. Neurologic and anesthetic-depth monitoring

Processed EEG

Processed EEG, such as BIS, can be considered in:

Total intravenous anesthesia
High awareness-risk situations
Frail patients where anesthetic dose reduction is important
Long operations with substantial physiologic disturbance

It estimates hypnotic effect, not analgesia or immobility. A low index can reflect hypothermia, cerebral hypoperfusion, EEG suppression, or artifact, not necessarily excessive anesthetic concentration.

Quantitative neuromuscular monitoring

Use quantitative train-of-four monitoring whenever non-depolarizing neuromuscular blockers are given, particularly in thoracic, abdominal, and head-and-neck surgery. It helps avoid residual paralysis and postoperative pulmonary complications. Miller's Anesthesia, 10th ed., p. 16, section “Use of Nerve Stimulators in Daily Clinical Practice.”

Cerebral oximetry

NIRS cerebral oximetry is most relevant in:

Carotid or great-vessel involvement
Steep Trendelenburg
Major blood loss
Severe anemia or hypoxemia
High risk of cerebral hypoperfusion

It is a trend monitor. A fall should trigger a search for causes: hypotension, hypoxemia, hypocapnia, anemia, malposition, venous obstruction, or low cardiac output.

Practical escalation by operation

Clinical setting	Monitoring commonly considered
Major open abdominal cancer surgery	Arterial line, large-bore access, serial ABG/lactate/Hb/calcium, selected cardiac-output monitoring, temperature, quantitative TOF
Cytoreduction plus HIPEC	Arterial line, central access, continuous core temperature, serial ABG/electrolytes/lactate, urine output, coagulation or TEG/ROTEM if bleeding
Hepatic resection	Arterial line, large-bore access, serial Hb/ABG/calcium, low-CVP strategy only with clear plan, TEG/ROTEM in significant bleeding, selected echo/CO monitoring
Thoracic resection with OLV	Arterial line for major cases, ABGs, airway pressure/compliance trends, bronchoscopy for tube position, temperature, quantitative TOF
Head-and-neck free flap	Arterial line for lengthy/high-risk cases, temperature, Hb and perfusion optimization, careful vasopressor use when indicated, quantitative TOF
Surgery near heart/great vessels	Arterial line before induction when appropriate, central access, TEE or focused echo availability, massive-transfusion readiness, possibly PAC for severe pulmonary hypertension/RV failure

A high-yield framework

Before choosing any advanced monitor, answer three questions:

What complication is likely?
Hemorrhage, RV failure, hypoxemia, low cardiac output, coagulopathy, hyperthermia?
Will the monitor detect it earlier or distinguish its cause?
What will I do differently if the result changes?

That is the core of advanced monitoring in onco-anaesthesia: risk-based selection, physiology-based interpretation, and intervention guided by trends rather than isolated numbers.

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