False
Equivalents
Perioperative Opioid
Equivalency and Opioid
Dose Variation During
Cardiac Surgery
Clark Fisher, MD, PhD
Yale School of Medicine “IS THIS 100 MCG OF FENTANYL?”
I have no conflicts of interest
to declare.
•My planned MPOG study
•My actual MPOG study
•What the study showed
•What I learned
The Study Plan
2020s: Peri-Retirement of Opioid Anesthesia?
2020s: Peri-Retirement of Opioid Anesthesia?
0
20
40
60
80
Mean IV Morphine Equivalents (mg)
Opioid Use by Case Type
How much opioid are cardiac surgery
patients getting, and why?
•Examine adult cardiac surgeries
across MPOG (2014 -2022)
•Measure morphine equivalents given
during each surgery
•Calculate how much of a patient’s opioid dose was
attributable to:
1. The patient
2. The anesthesiologist
3. The hospital
The Study Reality
Opioid Mix
85%
11%
3%
0.4%
0.2%
Fentanyl
Sufentanil
Both
Long-Acting
Only
None
Wait, what is an equivalent opioid dose?
IV Fentanyl
Time (hours)
Effect
10
IV Morphine
Time (hours)
Effect
10
Effect
0 1
100 mcg =15 mg ?
0 1
100 mcg =10 mg ?
0 1
100 mcg =40 mg ?
Equivalent Opioid Concentration
EEG Spectral Edge (% Change)
Opioid Concentration (ng/ml)
Egan et al., “The electroencephalogram (EEG) and clinical measures of opioid potency.”
Measuring Opioid Exposure
PK Modeling
Conversion to
Common Opioid
Addition and Integration
What This Showed
Opioid Exposure in Cardiac Surgeries
Opioid Exposure in Cardiac Surgeries
Mean: 1,140 mcg
Median: 1,000 mcg
IV Fentanyl “Equivalents”
Adjusted Opioid Dose by Anesthesiologist
•500 -4,000 mcg Fentanyl
•60% of dose
explained by
anesthesiologist and
hospital
•<6% explained by sex,
age, weight, comorbidities,
surgery length, etc.
What I Learned
No Plan Survives First Contact With The Enemy
PCRC Proposal
^
Pharmacokinetic Models are Useful for
Studying Opioid Exposure
Models effects at specific time points
Gracefully handles
opioid combinations
Acknowledges differences in patient size
Possible MPOG Measures
•Total opioid exposure from perioperative opioids
•Effect site concentration at emergence
•Effect site concentration at PACU arrival
•?
Thank You
Yale Anesthesiology
Robert B. Schonberger
Hung-Mo Lin
Yale Center for Analytical Science
Julian Zhao
Yanhong Deng
Multicenter Perioperative
Outcomes Group (Michigan)
Allison Janda
Michael Mathis
Michael Burns
MPOG Research Team
Other Collaborators
Miriam Treggiari - Duke
David Yang - Duke
Michael Aziz - OHSU
Amit Bardia - MGH
Steven Shafer - Stanford
PCRC Members
Support
NIGMS 5T32GM086287-14
MPOG Outcomes Research Fellowship
Fisher et al. (2025)
StanpumpR
