# Capnogram plateau micro‑oscillations preceding end‑tidal CO2 decline as an early cue to venous air embolism during supratentorial craniotomy: a case report

## TL;DR

This case report shows how subtle changes in capnogram patterns can signal early signs of venous air embolism during brain surgery.

## Contribution

The paper highlights capnogram plateau micro-oscillations as an early indicator of venous air embolism in the absence of advanced monitoring.

## Key findings

- Micro-oscillations on the capnogram plateau preceded a drop in end-tidal CO2 during surgery.
- Timely intervention based on capnogram changes stabilized the patient and prevented complications.
- Arterial blood gas levels improved alongside recovery of end-tidal CO2.

## Abstract

Venous air embolism (VAE) is a potentially fatal complication of craniotomy. When a TEE is not used, attention to waveform-level changes during conventional monitoring is crucial.

A woman in her 70 s underwent supratentorial tumor resection in the supine position with a slight head-up tilt. Approximately 1 h after the craniotomy, gradual decreases in SpO2 (98% → 96%), systolic blood pressure (105 → 90 mmHg), and EtCO2 (37 → 30 mmHg) were observed. New micro-oscillations appeared on the capnogram plateau, followed by an EtCO2 decrease to 22 mm Hg. VAE was suspected. Treatment, including field flooding, head-down positioning, as well as FiO2, dobutamine, and rapid fluid supplementation, stabilized her and allowed the uneventful completion of surgery. Arterial blood gas levels improved concurrently with EtCO2 recovery.

Careful scrutiny of capnogram morphology, not only numeric EtCO2, can expedite the suspicion and timely management of VAE when advanced monitoring is unavailable.