Epidural cooling minimizes spinal cord injury after aortic cross-clamping through induction of nitric oxide synthase.

BACKGROUND: By using a U-shaped lumen catheter, the authors examined the effects of epidural cooling on spinal cord injury after aortic cross-clamping (ACC), with a focus on changes of spinal cord blood flow and expression of inducible nitric oxide synthase. METHODS: Sixteen pigs were randomized into two groups: Control group (n = 8) or Cooling group (n = 8). In the latter, epidural cooling started at 30 min (baseline) before 45 min of ACC and persisted for the next 30 min of reperfusion period. Spinal cord blood flow and somatosensory-evoked potentials were assessed during peri-ACC period. At 48 h, we evaluated hind limb function by using Tarlov score and expression of inducible nitric oxide synthase on spinal cord using immunohistochemistry. RESULTS: After ACC, spinal cord blood flow dropped to a similar extent in both groups. During the reperfusion period, spinal cord blood flow increased up to 113% (103-124%), median (interquartile range), level transiently and decreased to 32% (22-47%) level versus baseline in the Control group, whereas it increased and remained at 92% (86-97%) level in the Cooling group. Simultaneously, somatosensory-evoked potentials showed that onset of loss time was delayed and recovery time was shortened in the Cooling group. Tarlov scores in the Cooling group were significantly higher and accompanied by normal-appearing motor neurons and significantly greater expression of inducible nitric oxide synthase on spinal cord versus the Control group. CONCLUSIONS: This study shows that epidural cooling during ACC minimized the risk of spinal cord injury, possibly by preventing delayed hypoperfusion and upregulating inducible nitric oxide synthase expression.

Cardioscopic guidance of linear lesion creation for radiofrequency ablation.

BACKGROUND: The broad use of catheter ablation of atrial fibrillation is limited by the difficulty inherent in creating transmural linear lesions under fluoroscopy. Therefore, we evaluated cardioscopy as a more accurate method of guiding the catheter for the placement of linear lesions. METHODS: Nineteen swine underwent endocardial ablation to create linear conduction block lesions in the right atrium under cardioscopy (group I, n = 13) or fluoroscopy (group II, n = 6). In both groups, the linear lesion was created between the superior and inferior vena cava, perpendicular to hexapolar electrodes placed on the epicardial surface. Each swine received two pairs of epicardial hexapolar electrodes: one pair to measure the conduction delay time across the ablated line and another pair for pacing. The time spent to complete the ablation, number of trials and effective ablations, ratio of effective ablations to trials, length of the lesion, conduction delay under pacing, and postmortem pathology were compared between the two groups. RESULTS: Statistically significant differences were found for the time required for ablation, ratio of effective ablation to total number of trials, and conduction delay. Histologic analysis revealed more homogenous, continuous lesions in group I. CONCLUSIONS: Cardioscopy facilitated the placement of a conduction block line more efficiently than ablation performed under fluoroscopy. Landmarks of tissue relevant to ablation are readily visualized by cardioscopy. Moreover, cardioscopy can be useful for the development of a guiding catheter for the ablation of atrial fibrillation.

Combined use of an epidural cooling catheter and systemic moderate hypothermia enhances spinal cord protection against ischemic injury in rabbits.

BACKGROUND: Epidural placement of a cooling catheter can protect against ischemic spinal cord injury. With the use of rabbits, we investigated whether this epidural cooling technique, when combined with systemic moderate hypothermia, can protect the spinal cord against ischemic metabolic stress. METHODS: New Zealand white rabbits (n = 28) were assigned to 1 of 4 different groups. Animals underwent abdominal aortic occlusion for 30 minutes using a 3F balloon catheter. Group 1 (n = 7) underwent epidural cooling by the catheter and systemic moderate hypothermia (35 °C) induced with a cooling blanket. Group 2 (n = 7) underwent epidural cooling under systemic normothermia (38.5 °C). Group 3 (n = 7) underwent systemic moderate hypothermia (35 °C) without epidural cooling. Group 4 (n = 7) underwent neither epidural nor blanket cooling as a negative control. Neurologic status of their hind limbs was graded according to the modified Tarlov scale at 1, 2, and 7 days after surgery. RESULTS: During infrarenal aortic ischemia, epidural temperature was significantly lower in group 1 (18.5 °C ± 0.8 °C) than in group 2 (28.6 °C ± 1.0 °C; P = .0001), group 3 (34.2 °C ± 0.06 °C; P = .0001), or group 4 (38.5 °C ± 0.2 °C; P = .0001). Hind limb function recovery was greater in group 1 (mean Tarlov score, 4.9 ± 0.057) than in group 2 (2.6 ± 0.3; P = .0028), group 3 (2.1 ± 0.34; P = .0088), or group 4 (0.0 ± 0.0; P = .0003). CONCLUSIONS: Epidural cooling catheter combined with systemic moderate hypothermia produced additive cooling ability and protected the spinal cord against ischemia in rabbits more effectively than either intervention alone.

Use of an epidural cooling catheter with a closed countercurrent lumen to protect against ischemic spinal cord injury in pigs.

OBJECTIVE: We developed an epidural cooling catheter containing cold saline solution circulating in an isolated lumen. After placement by a minimally invasive approach, we evaluated protection effect against ischemic spinal cord injury in pigs. METHODS: Fourteen pigs underwent thoracic aortic double clamping for 45 minutes under systemic mild hypothermia (36 degrees C). Group A (n = 7) underwent local hypothermia with the cooling catheter. Group B (n = 7) underwent catheter placement only, without cooling. Spinal cord somatosensory evoked potentials were recorded to assess electrophysiologic status. Neurologic function was evaluated with a modified Tarlov score. RESULTS: At aortic crossclamping, spinal temperature in group A (26.5 degrees C +/- 2.4 degrees C) was significantly lower than that in group B (35.3 degrees C +/- 0.6 degrees C, P = .0001). Mean time from aortic crossclamping to onset of potential loss was significantly longer in group A (28.4 +/- 6.6 minutes) than in group B (18.3 +/- 5.0 minutes, P = .007). Mean duration of total loss of potentials was significantly shorter in group A (19.0 +/- 6.7 minutes) than that in group B (31.3 +/- 5.9 minutes, P = .003). Group A showed significantly better neurologic function (mean Tarlov score 4.4 +/- 0.8) than that of group B (0.1 +/- 0.4, P = .0001). Mean total number of intact motor neurons was significantly greater in group A (24.5 +/- 6.8) than that of group B (9.9 +/- 6.8, P = .0001). CONCLUSION: By cooling the spinal cord selectively and continuously, the newly designed epidural cooling catheter prevented ischemic injury in a pig model of aortic crossclamping.

An epidural cooling catheter protects the spinal cord against ischemic injury in pigs.

BACKGROUND: Using swine, we investigated whether epidural placement of a cooling catheter rather than infusing iced saline solution could protect the spinal cord from ischemia during aortic surgery. METHODS: We divided 14 domestic pigs into two groups of 7 each. Each underwent epidural catheter placement preceding 30 minutes of aortic cross-clamping distal to the origin of the left subclavian artery. In group 1, cold water was circulated continuously through the lumen of the catheter connected to an external unit. In group 2, animals received catheter placement without cooling. Spinal cord somatosensory evoked potentials were recorded. Neurologic status involving hind limbs was graded sequentially after surgery. RESULTS: At aortic cross-clamping, spinal temperature in group 1 (31.7 degrees +/- 0.6 degrees C) was significantly lower than in group 2 (37.8 degrees +/- 0.4 degrees C; p < 0.0001). No significant elevation of intrathecal pressure accompanied cooling with the catheter (group 1, 8.1 +/- 1.7 mm Hg; group 2, 8.0 +/- 1.5 mm Hg). Mean duration of total loss of potentials was significantly shorter in group 1 (7.4 +/- 3.8 minutes) than group 2 (19.7 +/- 7.3 minutes; p = 0.0002). Pigs in group 1 exhibited better hind limb function recovery (mean Tarlov score, 4.7 +/- 0.5) than group 2 (0.6 +/- 0.8; p = 0.0017). Group 1 showed normal histologic characteristics, whereas group 2 showed loss of motor neurons in the ventral horns. CONCLUSIONS: Epidural cooling catheter without iced saline infusion can cool the spinal cord without elevating intrathecal pressure, protecting the cord against ischemia.