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[Effects of total spinal block on the circulatory system and myocardial oxygen demand and supply balance]
M Kobori1, H Negishi, A Hosoyamada
1Department of Anesthesiology, School of Medicine, Showa University, Tokyo.
Insights
Total spinal block with lidocaine depresses circulation, decreasing heart rate and blood pressure. However, myocardial oxygen supply and demand remain balanced, indicating adequate blood flow despite reduced oxygen levels.
Area of Science:
- Anesthesiology
- Cardiovascular Physiology
- Surgical Research
Context:
- Total spinal block is a potent anesthetic technique.
- Understanding its cardiovascular effects is crucial for patient safety.
- Myocardial oxygen balance is a key indicator of cardiac health during anesthesia.
Purpose:
- To investigate the effects of total spinal block on the circulatory system.
- To assess the balance between myocardial oxygen supply and demand under total spinal block.
- To determine the impact of lidocaine-induced total spinal block on cardiac function in dogs.
Summary:
- Total spinal block in dogs significantly decreased heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), and left ventricular pressure change over time (LV dp/dt max).
- A decrease in mixed venous oxygen saturation (SvO2) indicated reduced oxygen supply, while coronary arterial blood flow was also diminished.
- Despite reduced myocardial oxygen consumption, coronary venous oxygen saturation (ScvO2) and extraction rates remained stable, suggesting maintained oxygen supply-demand balance.
Impact:
- The findings suggest that adequate coronary blood flow is preserved during total spinal block.
- This research indicates a potential for well-balanced myocardial oxygen supply and demand under total spinal block conditions.
- Provides insights into the cardiovascular safety profile of total spinal anesthesia.
Abstract:
Total spinal block with 1.5% lidocaine was performed in adult mongrel dogs, and its effects on circulatory system and myocardial oxygen demand and supply balance were investigated. The study demonstrates that the circulatory system is depressed under induced total spinal block, as manifested by a marked decrease in HR, MAP, CI, and LV dp/dt max. A decrease in SvO2 suggests that total spinal block places the animals in lack of oxygen supply. On the other hand, coronary arterial blood flow was significantly reduced by total spinal block. With reduction in myocardial oxygen consumption, however, coronary venous oxygen saturation (ScvO2) and myocardial oxygen extraction rate remained unaffected, and myocardial lactate uptake was also affected little. The results suggest that sufficient coronary arterial blood flow is maintained during total spinal block to respond to the myocardial oxygen demand. There is a possibility that myocardial oxygen demand and supply are well balanced under total spinal block.