September 2026 |Utilizing Arterial Blood Gases in Large‑Animal Anesthesia: Real‑Time Interpretation for Real‑Time Adjustments
VITALS Newsletter — by Niki DeValk, AAS, LVT, SRS
Interventional & Surgical Specialist | Owner, NiKara Preclinical
Let’s Dive In
Hi everyone —
One of the most powerful — and most underutilized — tools in large‑animal anesthesia is the arterial blood gas. ABGs give us a real‑time snapshot of ventilation, oxygenation, perfusion, and acid‑base balance, and they reveal physiologic drift long before monitors or behavior do. This month, I’ve been reviewing ABG trends across swine and ovine studies, and the same pattern keeps emerging: teams who use ABGs proactively make better intraoperative decisions, stabilize physiology earlier, and produce more consistent recoveries and study outcomes.
This issue of VITALS focuses on how to interpret ABGs in real time and how to translate those results into immediate, meaningful adjustments during anesthesia. When used intentionally, ABGs become one of the most reliable tools for preventing drift, improving stability, and reducing physiologic noise in research data.
Let’s get into the September issue of VITALS — and explore how ABGs can elevate your anesthesia practice.
Why This Topic Matters
ABGs are the gold standard for evaluating ventilation, oxygenation, and acid‑base status — yet many teams rely solely on ETCO₂ and SpO₂, which can mask early instability. ABGs reveal the physiologic truth behind the numbers.
Common early indicators include:
PaCO₂ rising despite stable ETCO₂
PaO₂ dropping while SpO₂ remains normal
pH shifting toward acidosis
lactate creeping upward during long procedures
HCO₃⁻ compensating for respiratory drift
These changes matter. They predict recovery quality, metabolic stability, and even study endpoints long before inhalants are discontinued.
ABGs give us the information we need to intervene early — and early intervention is what keeps physiology predictable.
Key Insights
PaCO₂
The most accurate indicator of ventilation
Rising PaCO₂ predicts prolonged apnea, dysphoria, and delayed recovery
Even mild elevations alter cardiovascular parameters and metabolic markers
PaO₂
The gold standard for oxygenation
Can be low even when SpO₂ looks perfect
Declines signal V/Q mismatch, lung collapse, or inadequate recruitment
pH & HCO₃⁻
Reveal respiratory vs metabolic imbalance
Guide decisions on ventilation, perfusion support, and fluid therapy
Lactate
Early indicator of perfusion deficits
Helps differentiate ventilation‑related drift from cardiovascular drift
ABGs turn guesswork into precision.
What’s Changing
More facilities are integrating ABGs into routine anesthetic monitoring — not just for long procedures, but for any case where stability matters.
Common updates include:
sampling ABGs at baseline, mid‑procedure, and pre‑recovery
adjusting ventilation based on PaCO₂ rather than ETCO₂ alone
performing recruitment maneuvers when PaO₂ declines
using pH and HCO₃⁻ to guide perfusion and fluid decisions
monitoring lactate to detect early metabolic strain
interpreting ABG trends rather than isolated values
These refinements reduce recovery delays, improve physiologic consistency, and strengthen study reproducibility.
Clinical Connections
ABG interpretation is especially critical in:
long‑duration procedures
dorsal recumbency
high‑acuity interventional models
species prone to lung collapse (swine) or diaphragmatic compression (sheep)
studies with metabolic or inflammatory endpoints
Key strategies include:
Ventilation Targets PaCO₂: 35–45 mmHg PaO₂: >90 mmHg pH: 7.35–7.45 Lactate: <2.0 mmol/L
Action Steps
increase rate or tidal volume when PaCO₂ rises
perform recruitment maneuvers when PaO₂ drops
add PEEP cautiously to improve oxygenation
adjust MAP support when lactate increases
use pH and HCO₃⁻ to differentiate respiratory vs metabolic drift
ABGs guide precise, targeted interventions.
Case Study: The Sheep With “Normal Vitals” and a PaO₂ of 62 mmHg
The scenario: A 50‑kg sheep undergoing a vascular access procedure showed stable SpO₂ and ETCO₂ — but ABG sampling revealed PaO₂ of 62 mmHg and rising PaCO₂. Despite normal monitors, the animal was developing significant V/Q mismatch and early respiratory acidosis.
The pivot: Interventions included:
increasing ventilation to target PaCO₂ 35–45 mmHg
performing a recruitment maneuver
adding 3–5 cmH₂O PEEP
adjusting positioning to reduce diaphragmatic compression
The outcome: PaO₂ increased to 110 mmHg, PaCO₂ normalized, and recovery was smooth, coordinated, and fast.
The takeaway: SpO₂ and ETCO₂ alone can miss early instability. ABGs reveal the real physiologic picture — and guide the interventions that prevent drift.
Practical Takeaways
ABGs provide the most accurate assessment of ventilation and oxygenation
PaCO₂ and PaO₂ trends predict recovery quality
pH and HCO₃⁻ guide perfusion and metabolic decisions
Lactate reveals early strain long before vitals change
ABGs reduce physiologic noise and improve reproducibility
Real‑time interpretation leads to real‑time stability
Wrapping Up
Thank you for spending time with this month’s issue of VITALS. Arterial blood gases are one of the most powerful tools we have in large‑animal anesthesia — and when used intentionally, they transform how we manage physiology, support recoveries, and protect study outcomes.
If your team is ready to strengthen ABG interpretation skills, improve intraoperative decision‑making, or build study‑specific anesthesia confidence, I’m booking fall sessions now — virtual or hands‑on, individual or group.
Stay sharp. Stay supported. Stay vital.
— Niki
Niki DeValk, AAS, LVT, SRS
Independent Surgical & Anesthetic Specialist | Owner, NiKara Preclinical
📧 niki@nikarapreclinical.com 🌐 www.nikarapreclinical.com
