✓ Two distinct and sequential patterns of hemodynamic alteration were observed after acute cervical spinal cord transection in anesthetized dogs. Interruption of the cord initially caused a 45% increase in mean arterial pressure (p < 0.01), a 34% increase in systemic vascular resistance (p < 0.05), and a 92% increase in left ventricular dp/dt (p < 0.01), reflecting a generalized sympathetic response to trauma. Concomitant bradycardia and escape arrhythmias suggested relative parasympathetic hyperactivity. Resolution of the brief pressor response was followed by a second, more prolonged, period characterized by a fall in arterial pressure to 71% of control levels (p < 0.05), a 16% decrease in systemic vascular resistance, and a 58.5% decrease in left ventricular dp/dt (p < 0.01). These latter hemodynamic changes are consistent with sympathetic denervation and failure of regulatory mechanisms mediated by both alpha- and beta-adrenergic peripheral vascular and myocardial receptors.
Part I: Hemodynamic changes after acute cervical spinal cord transection
Phillip A. Tibbs, Byron Young, R. G. McAllister Jr., William H. Brooks, and Laddie Tackett
Roman O. Kowalchuk, Michael R. Waters, K. Martin Richardson, Kelly Spencer, James M. Larner, William H. McAllister, Jason P. Sheehan, and Charles R. Kersh
This study evaluated a large cohort of patients treated with stereotactic body radiation therapy for spinal metastases and investigated predictive factors for local control, local progression-free survival (LPFS), overall survival, and pain response between the different spinal regions.
The study was undertaken via retrospective review at a single institution. Patients with a tumor metastatic to the spine were included, while patients with benign tumors or primary spinal cord cancers were excluded. Statistical analysis involved univariate analysis, Cox proportional hazards analysis, the Kaplan-Meier method, and machine learning techniques (decision-tree analysis).
A total of 165 patients with 190 distinct lesions met all inclusion criteria for the study. Lesions were distributed throughout the cervical (19%), thoracic (43%), lumbar (19%), and sacral (18%) spines. The most common treatment regimen was 24 Gy in 3 fractions (44%). Via the Kaplan-Meier method, the 24-month local control was 80%. Sacral spine lesions demonstrated decreased local control (p = 0.01) and LPFS (p < 0.005) compared with those of the thoracolumbar spine. The cervical spine cases had improved local control (p < 0.005) and LPFS (p < 0.005) compared with the sacral spine and trended toward improvement relative to the thoracolumbar spine. The 36-month local control rates for cervical, thoracolumbar, and sacral tumors were 86%, 73%, and 44%, respectively. Comparably, the 36-month LPFS rates for cervical, thoracolumbar, and sacral tumors were 85%, 67%, and 35%, respectively. A planning target volume (PTV) > 50 cm3 was also predictive of local failure (p = 0.04). Fewer cervical spine cases had disease with PTV > 50 cm3 than the thoracolumbar (p = 5.87 × 10−8) and sacral (p = 3.9 × 10−3) cases. Using decision-tree analysis, the highest-fidelity models for predicting pain-free status and local failure demonstrated the first splits as being cervical and sacral location, respectively.
This study presents a novel risk stratification for local failure and LPFS by spinal region. Patients with metastases to the sacral spine may have decreased local control due to increased PTV, especially with a PTV of > 50 cm3. Multidisciplinary care should be emphasized in these patients, and both surgical intervention and radiotherapy should be strongly considered.