The effects of anesthesia on osmotic blood-brain barrier disruption

To evaluate the effect of various anesthetic agents on hyperosmolar blood-brain barrier disruption (BBBD), Sprague-Dawley rats were given pentobarbital (PB), ketamine-xylazine (KX), isoflurane (IF), methoxyflurane (MF), or fentanyl-droperidol (FD) before intracarotid infusion of mannitol or saline. Physiological monitoring showed that the effects of mannitol infusion differed significantly from those of saline infusion and were associated with transient bradycardia, hypotension, metabolic acidosis, and electroencephalographic depression. With PB, KX, or IF anesthesia, we obtained excellent BBBD as evidence by 3+ Evans blue staining of the mannitol-infused cerebral hemisphere. FD anesthesia was associated with tachycardia and MF anesthesia resulted in hypotension; both showed poor Evans blue staining. Radioisotope delivery to the disrupted hemisphere averaged 0.80% of the administered ¹²⁵I-albumin compared to 0.03% in the contralateral and 0.06% in control (saline-infused) hemispheres. ^99mTc-glucoheptonate delivery measured 0.49% of the administered dose after BBBD, 0.03% contralaterally, and 0.05% in control hemispheres. Pharmacological manipulation to normalize the cardiac index in the FD and MF groups resulted in 3+ Evans blue staining and significantly increased delivery of albumin and glucoheptonate. This study suggests that the cardiovascular changes of these specific anesthetic agents are important in obtaining optimal hyperosmolar BBBD.