Spinal cord blood flow changes following systemic hypothermia and spinal cord compression injury: an experimental study in the rat using Laser-Doppler flowmetry

Study design: It is well known that changes of the body temperature as well as trauma influence the blood flow in the brain and spinal cord. However, there is still a lack of knowledge concerning the levels of blood flow chan ges, especially during hypothermia. Objectives: This investigation was carried out to examine the effects of sy stemic hypothermia and trauma on spinal cord blood flow (SCBF). Methods: Twenty-four rats were randomized either to thoracic laminectomy on ly (Th VII-IX) or to 35 g spinal cord compression trauma. The animals were further randomized to either constant normothermia (38 degreesC) or to a sy stemic cooling procedure, ie I eduction of the esophageal temperature from 38 to 30 degreesC. SCBF was recorded 5 tnm caudal to the injury zone using Laser-Doppler flowmetry which allows a non-invasive continuous recording of local changes in the blood flow. The autoregulation ability was tested at the end of the experiments by inducing a 30-50 mmHg blood-pressure fall, us ing blood-withdrawal from the carotid artery. Results: The mean SCBF decreased 2.8% and 3.5% per centigrade reduction of esophageal temperature in the animals sustained to hypothermia with and wit hout trauma, respectively. This could be compared to a decrease of 0.2%/min when only trauma was applied. No significant differences were seen between the groups concerning auto regulatory ability. Conclusions: Our results indicate that the core temperature has a high impa ct on the SCBF independent of previous trauma recorded by Laser-Doppler flo wmetry. This influence exceeds the response mediated by moderate compressio n trauma alone. Sponsorship: The study was supported by grants from the Laerdal foundation.