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Time course in thoracic epidural pressure measurement
T Okutomi1, S Watanabe, F Goto
1Department of Anaesthesiology, School of Medicine, Kitasato University, Kanagawa, Japan.
Canadian Journal of Anaesthesia = Journal Canadien D'Anesthesie
|November 1, 1993
Summary
Transient negative thoracic epidural pressure during needle insertion is an artifact caused by dural tenting. Normal positive epidural pressure is restored within 90 seconds.
Area of Science:
- Anesthesiology
- Neurosurgery
- Pain Management
Background:
- Accurate measurement of thoracic epidural pressure is crucial for safe and effective epidural anesthesia.
- Previous studies have reported high negative pressures during epidural needle insertion, but the underlying mechanism remains unclear.
Purpose of the Study:
- To accurately measure thoracic epidural pressure at the time of epidural needle insertion.
- To investigate the transient pressure changes observed during the procedure.
Main Methods:
- A unique closed pressure measurement system with a flow-regulating transducer was used.
- The system prevented saline evacuation into the epidural space, ensuring accurate pressure readings.
- Measurements were taken after inserting a Tuohy needle at the T7-8 intervertebral level in 13 patients.
Main Results:
- High negative epidural pressures (up to -60 mmHg) were observed at the moment of dural puncture.
- Within 30 seconds, pressure became positive in 12 of 13 patients.
- Pressure stabilized at +3.7 +/- 3.2 mmHg within 90 seconds, consistent with repeated measurements.
Conclusions:
- The observed negative epidural pressures are likely artifacts caused by the tenting of the dura mater by the needle.
- The surrounding tissues adapt, restoring normal positive epidural pressure shortly after needle insertion.
- These findings have implications for understanding epidural space dynamics and improving procedural techniques.