Establishing a Subarachnoid Hemorrhage Rat Model Induced by Autologous Blood Injection

Take an anesthetized rat with its skull exposed and a probe implanted to measure intracranial pressure.

Using a reference point on the skull, mark the target site and drill a hole.

Remove the bone fragments and fill the hole with bone wax.

Drill another hole. Locate a blood vessel and secure a probe to measure cerebral blood flow.

Take a needle and insert it into the brain until the skull is felt.

Retract slightly to ensure its placement in front of the optic chiasm, where major blood vessels are located.

Fill the needle chamber with fresh blood drawn from the rat's tail and connect the syringe containing blood.

Inject the blood into the fluid-filled subarachnoid space between the outer and inner brain membranes, which increases intracranial pressure, causing blood vessel constriction.

This leads to a decreased cerebral blood flow, establishing a subarachnoid hemorrhage model.

To place the laser Doppler probe, make a 15-millimeter incision caudally in the midline, starting just anterior to the eyes. After removing the connective tissue and the muscles with forceps, use the end of a sterile cotton swab as a regime to identify the bregma and the coronal sutures.

After placing the armed retractor, place a 25-gauge spinal needle in the stereotaxic frame exactly on the bregma and note the position. Next, remove the needle from the bregma. Move the frame anteriorly by 6.5 millimeters, then replace the needle in the midline to mark the side of drilling.

Drill until the dura mater is identified below the bone. Using straight forceps, gently remove the bone fragments, then fill the cavity with bone wax. Next, 3 to 4 millimeters lateral to the right of the bregma and just anterior to the coronal suture for the laser Doppler, drill another hole taking care not to penetrate the dura mater.

Look for the vessels where the laser Doppler can measure the blood flow. Place the laser Doppler and check the values. A minimum value of 100 flux units is required. If the values remain acceptable after removing the microscope, add 1 drop of glue to fix the probe. Recheck to confirm whether the value is above 80 flux units.

To induce subarachnoid hemorrhage, insert the needle gently through the skull in the midline between the hemispheres until resistance is felt due to the base of the skull. Retract the needle by 1 millimeter to ensure correct placement just anteriorly to the optic chiasm. To ensure the most homogeneous result when injecting the blood, turn the needle clockwise by 90 degrees such that the needle tip points to the right. Then, remove the stiletto.

After a 15-minute equilibration, adjust the level of anesthesia to obtain a mean arterial blood pressure in the range 80 to 100 millimeters of mercury. Then, perform a blood gas analysis to confirm that the pH, partial pressure of carbon dioxide and partial pressure of oxygen are within physiological parameters.

Next, using a 1-milliliter syringe with a blunt 23-gauge needle, withdraw 500 microliters of blood from the tail catheter. To avoid injection of air, fill the dead space of the spinal needle chamber with blood. After adjusting the volume of the blood in the syringe to 300 microliters, connect the syringe to the spinal needle. Then, grasping firmly around the syringe, inject the blood manually to surpass mean arterial pressure. Observe a steep rise in the intracerebral pressure and a concurrent steep fall in the cerebral blood flow.