Every Surgery Is a Conversation with Physiology
There is a point in surgical training when you realize that monitoring is not really about watching numbers.
It is about listening.
Heart rate, blood pressure, capnography, temperature, oxygen saturation, perfusion, ventilation, and even the way a patient responds to surgical stimulation are all pieces of an ongoing physiologic conversation.
The patient is constantly giving us information.
The challenge is learning how to interpret it.
What should the heart rate be?
When we first learn physiologic monitoring, it is natural to focus on ranges.
What should the blood pressure be?
What should the end-tidal CO₂ be?
What temperature should we maintain?
Those values are important. They give us useful boundaries and help us recognize when something may require attention.
But a number by itself rarely tells the entire story.
A mean arterial pressure of 65 mmHg means something very different in a patient whose MAP has been stable at 65 throughout the procedure than it does in a patient whose MAP was 85 ten minutes earlier.
An ETCO₂ of 42 mmHg may be perfectly reasonable.
But if that same patient had been holding steadily at 34 mmHg and the value begins climbing, the important question is not simply:
“Is 42 acceptable?”
The more useful question is:
“Why did it change?”
That shift in thinking—from reacting to a number to interpreting a change—is where physiologic monitoring becomes truly valuable.
Know Your Patient Before You Need to Troubleshoot
One of the most important things we can do at the beginning of a procedure is establish a baseline.
What is the heart rate?
Once the patient is anesthetized and physiologically stable, take a moment to recognize what normal looks like for that patient.
What is the blood pressure?
What does the capnogram look like?
What is the ETCO₂?
What is the temperature?
How is peripheral perfusion?
What ventilator settings are producing those values?
What does the ECG look like?
That baseline becomes your roadmap.
If something changes later in the procedure, you now have a meaningful point of comparison.
Without a baseline, we are often left comparing a patient to a textbook range.
With a baseline, we can compare the patient to themselves.
That is often far more useful.
Watch the Relationships Between the Numbers
Physiology does not exist in separate boxes.
Blood pressure affects perfusion.
Ventilation affects CO₂.
Temperature affects metabolism.
Blood loss may affect pressure, perfusion, heart rate, and temperature.
Changes in cardiac output can alter ETCO₂.
Anesthetic depth can affect ventilation and cardiovascular function.
Surgical manipulation can change several parameters almost simultaneously.
This is why I teach surgical teams not to focus too narrowly on a single monitor.
If blood pressure changes, look at the rest of the patient.
If ETCO₂ falls, look at the blood pressure.
Look at ventilation.
Look at the airway.
Look at the surgical field.
Look at what happened immediately before the change.
If temperature is falling, think beyond the temperature probe.
How long has the patient been exposed?
Are fluids warm?
Is the patient wet?
What is happening with perfusion?
How long has anesthesia been maintained?
Every parameter is part of a larger physiologic story.
The Patient Usually Whispers Before They Scream
Major physiologic problems rarely appear completely out of nowhere.
Often, there are small changes first.
A gradual decline in blood pressure.
A slowly rising ETCO₂.
A temperature that continues to drift downward.
A limb that feels cooler than it did earlier.
A waveform that begins to look different.
A recovery that is taking slightly longer than expected.
Individually, these changes may seem minor.
Together—or when viewed as a trend—they may be the first indication that something is changing.
Experienced monitoring is not simply recognizing the emergency.
It is recognizing the whisper before it becomes one.
Trends Matter More Than Snapshots
One of the most valuable habits I encourage is watching direction.
Is the value:
- Stable?
- Slowly increasing?
- Slowly decreasing?
- Changing suddenly?
- Responding to an intervention?
- Continuing to change despite that intervention?
A single number tells you where the patient is at one moment.
A trend tells you where the patient is going.
That distinction can completely change how early we recognize a developing problem.
Surgery Teaches Us When We Stay Curious
Some of the most valuable lessons in my career have come from sequential surgical cases.
When you perform several similar procedures, you begin to see patterns.
You notice which interventions consistently improve stability.
You recognize which small changes tend to precede larger ones.
You begin to understand how warming, ventilation, positioning, fluid administration, surgical manipulation, anesthetic depth, and recovery all interact.
During consulting work in France in both 2024 and 2026, those lessons were reinforced repeatedly.
Each case provided another opportunity to observe, adjust, evaluate, and refine.
Not because every patient behaved exactly the same.
Quite the opposite.
The value was in recognizing what was different—and asking why.
That process is at the heart of good surgical practice.
Monitoring Is Not the Same as Observing
Technology gives us extraordinary amounts of information.
But monitors should never replace observation.
Look at the patient.
Touch the extremities.
Watch the chest.
Assess the surgical field.
Look at mucous membranes when appropriate.
Watch the ventilator.
Pay attention to blood loss.
Notice changes in tissue color and temperature.
Observe how the patient responds to stimulation.
Then combine those observations with the data on the screen.
A monitor is a tool.
Physiologic interpretation is the skill.
Our Goal Is Not to Memorize More Numbers
There will always be reference ranges, guidelines, and target values.
We need them.
But the goal of surgical training should go beyond memorization.
I want people to understand enough physiology that when something changes, they become curious.
Instead of immediately asking:
“What number should I fix?”
Ask:
“What is the patient trying to tell me?”
That question leads to better observation.
Better troubleshooting.
Better communication.
And ultimately, better surgical outcomes.
The patient is always talking.
Our job is to learn the language.
— Rindfield Consulting