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Cardiovascular response to blood loss during high intracranial pressure
O J Kirkeby1, I R Rise, L Nordsletten
1Institute for Surgical Research, National Hospital, University of Oslo, Norway.
Insights
Increased intracranial pressure (ICP) combined with hemorrhage significantly impairs cardiovascular function. This study in pigs shows high ICP exacerbates blood loss effects, potentially leading to shock.
Area of Science:
- Physiology
- Cardiovascular Research
- Neurosurgery
Background:
- Hemorrhage and increased intracranial pressure (ICP) are critical conditions.
- The combined effects on cardiovascular function require further investigation.
Purpose of the Study:
- To investigate the deleterious effects of combined hemorrhage and increased ICP on cardiovascular function.
- To assess the impact of high ICP on the body's response to blood loss.
Main Methods:
- Eight pigs were subjected to controlled hemorrhage (25% blood volume loss).
- High ICP was induced by infusing artificial cerebrospinal fluid (CSF).
- Hemodynamic parameters and regional tissue blood flow (using radioactive microspheres) were measured.
Main Results:
- Blood loss during high ICP significantly reduced blood flow to the intestines, skeletal muscle, and kidneys.
- Cardiac output and stroke volume decreased more profoundly with high ICP during hemorrhage.
- Systemic vascular resistance increased significantly more under high ICP conditions.
Conclusions:
- High ICP impairs protective cardiovascular mechanisms during hemorrhage.
- A 25% blood volume loss, usually compensated, can induce shock when ICP is elevated.
- These findings highlight the critical interplay between ICP and circulatory stability.
Abstract:
The authors hypothesized that the combination of hemorrhage and increased intracranial pressure (ICP) has deleterious effects on cardiovascular function. The effect of blood loss during normal and increased ICP was studied in eight pigs. The mean arterial pressure (MAP), pulmonary arterial pressure, pulmonary capillary wedge pressure, cardiac output, and cerebrospinal fluid (CSF) pressure were measured. The regional tissue blood flow was determined with radioactive microspheres labeled with four different nuclides. High ICP (80% of MAP) was induced by infusion of artificial CSF into the cisterna magna. The response to rapid arterial bleeding of 25% of blood volume was measured. The decrease in blood flow to the intestine, skeletal muscle, and the kidneys after blood loss was significantly greater during high ICP. The decrease in blood flow to the spleen and pancreas tended to be greater during high ICP, whereas the changes in blood flow to the liver, adrenal glands, and heart muscle showed no such tendency. The fall in cardiac output and heart stroke volume after blood loss were more pronounced when the ICP was high, and the increase in systemic vascular resistance was considerably greater. These observations suggest that during high ICP the physiological protective mechanisms against blood loss are impaired in the systemic circulation, and a loss of 25% of the blood volume, normally well compensated for, may induce a state of shock.