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Venoarterial bypass: a technique for spinal cord protection
The Journal of Thoracic and Cardiovascular Surgery
|February 1, 1985
Summary
During hypoxia, spinal cord blood flow significantly increases, and somatosensory evoked potentials show changes. However, spinal cord sensory function can be maintained with adequate perfusion pressures and flow rates.
Area of Science:
- Cardiovascular Physiology
- Neurophysiology
Background:
- Hypoxia poses a risk to spinal cord function during surgical procedures.
- Monitoring spinal cord function is crucial during interventions involving reduced oxygen supply.
Purpose of the Study:
- To investigate the impact of varying oxygen tensions on spinal cord blood flow.
- To assess the utility of somatosensory evoked potentials (SEPs) in monitoring spinal cord sensory function during induced hypoxia.
Main Methods:
- Utilized a canine model with cardiopulmonary bypass to control oxygen delivery.
- Manipulated oxygen levels to induce graded hypoxia.
- Measured spinal cord blood flow using radioactive microspheres.
- Continuously monitored SEPs (latency and amplitude) and distal aortic perfusion pressure.
Main Results:
- Spinal cord blood flow increased significantly (13.6 to 119.7 ml/100 gm/min) as oxygen tension decreased.
- SEPs demonstrated increased latency (19.3%) and decreased amplitude (43.3%) with falling oxygen levels.
- SEPs remained present as long as distal aortic pressure exceeded 80 mm Hg, with transient losses during hypotensive episodes.
Conclusions:
- Spinal cord blood flow dramatically increases in response to hypoxia, but SEPs deteriorate.
- Sufficiently high perfusion pressures and flow rates can maintain spinal cord sensory function during prolonged hypoxia.
- SEPs serve as a reliable tool for continuous monitoring of spinal cord sensory function under hypoxic conditions.