Effect of Mannitol 20% Versus Hypertonic Saline 7.5% in Brain Metabolism and Oxygenation
Status:
Completed
Trial end date:
2019-12-20
Target enrollment:
Participant gender:
Summary
Usage of osmotic agents is a standard practice in neuroanesthesia since cerebral edema is a
very common situation for patients with pathology in the brain. Cerebral edema is defined as
the accumulation of fluid in the intracellular or extracellular compartments of the brain.
Among other situations that have nothing to do with the brain, a supratentorial pathology
such as a tumor, traumatic injury or an aneurysm, will lead to disruption of blood-brain
barrier, and energy crisis of the cells that will cause mainly vasogenic and cytotoxic
cerebral edema. The most common monitoring method for "measuring" cerebral edema is ICP
(intracranial pressure) in which normal values are (with differences in the bibliography)
10-15 mmHg.
The osmotic agents used most in neuroanesthesia are mannitol 20% and hypertonic NaCl 7.5% or
3%. Their brain relaxation effectiveness is supposed to be quite the same between the two
different agents. Their main difference is that mannitol induces diuresis. Also, electrolyte
disorders are another possibility after mannitol infusion. On the other hand, NaCl 7.5%
causes vasodilation, does not induce diuresis and hemodynamically, even though it reduces
SBP, it raises CO because of its excessive vasodilation. But both reduce cerebral edema due
to the change of osmotic pressure in the vessels, that leads to extracting water from brain
cells.
A supratentorial craniotomy is de facto worsening the oxygenation and metabolism condition of
the surgical site, adding to the problem the intracranial pathology causes in the first
place. So if oxygen provided is low and the metabolic rate is high, the rate of anaerobic
metabolism will raise. Measuring the oxygen in the jugular bulb is the most reliable
monitoring method of cerebral oxygenation and metabolism.
It becomes evident that optimization of cerebral oxygenation during a craniotomy will
possibly affect the outcome of a patient, by improving it. So, if any superiority of one
osmotic agent over the other could be demonstrated this will be very helpful in the decision
making in routine clinical practice.