CAROTID-ARTERY AND JUGULAR-VEIN LIGATION WITH AND WITHOUT HYPOXIA IN THE RAT

A continuing concern about the use of extracorporeal membrane oxygenat ion (ECMO) is the cannulation of the common carotid artery or the inte rnal jugular vein. The authors investigated the changes that might occ ur in the brain with neck vessel ligation in the normal and the hypoxi c rat. Two groups of 60 rats each were studied. The first group was di vided into three subgroups of 20 animals each. Subgroup 1 (HH) was hyp oxic both 24 hours before and 24 hours after operation. Subgroup 2 (HN ) (the ECMO model) was hypoxic before operation and recovered for 24 h ours in room air. Subgroup 3 (NN) underwent the entire procedure in ro om air. For each oxygen environment, four different operations were pe rformed: carotid artery ligation, jugular vein ligation, carotid arter y and jugular vein ligation, and dissection of the vessels without lig ation (sham). Thus each subgroup was further divided into four sub-sub groups based on the operation performed. Rats were again anesthetized after a 24-hour recovery period and killed using low, blunt cervical d islocation. In the first group of 60 rats, the skull was opened and th e brain was carefully removed from the cranial vault and placed in a f ixative. The brains were placed in a small magnetic resonance imaging (MRI) head coil in groups of five and scans were obtained to provide T -1 and T-2 images that correlated with histological sections. MRI scan s were reviewed in random, blinded fashion by an imager unaware of how these animals had been treated. The brains were then sectioned corona lly at six corresponding levels: frontal, mid and posterior cerebrum, midbrain, pens, and medulla. Histological examination was performed in blinded fashion. The number of lesions (usually ischemic as noted by a decrease in the number of neurons) was totaled for each area of the brain. There were no differences that were consistent or statistically significant in the MR images of brains removed from the head, althoug h it would appear that rats with jugular vein and carotid artery ligat ion were relatively protected. In the HN group jugular vein ligation w as worst, and adding carotid artery ligation was best. In the histolog ical studies the NN group had significantly more lesions than the HH g roup (P < .01). The second group of 60 rats was divided and treated as the first group in all respects except that MRI was conducted immedia tely after death on intact heads, and no histological studies were per formed. This was done to control for lesions that might have been prod uced by removal of the brains from the skulls. In this group all findi ngs were right sided. One animal in the HN group showed midcerebral wh ite matter edema after jugular and carotid ligation. Focal anterior ce rebral edema was seen in another animal (HH) after isolated carotid li gation. An occipital infarct was found in one animal (HH) after both c arotid and jugular ligation. The authors conclude that neck vessel lig ation in the hypoxic or normoxic rat causes only occasional and sporad ic brain injury much as is seen clinically in newborn ECMO patients. C opyright (C) 1997 by W.B. Saunders Company.