Alterations in spinal cord norepinephrine levels following experimentally produced trauma in normal and adrenalectomized cats

Role of glycemia in acute spinal cord injury. Data from a rat experimental model and clinical experience

While experimental and clinical evidence indicates that in brain injury blood glucose increases with injury severity and hyperglycemia worsens neurological outcome, the role of blood glucose in secondary mechanisms of neuronal damage after acute spinal cord injury has not yet been investigated. Data from spinal cord ischemia models suggests a deleterious effect of hyperglycemia, likely due to enhanced lactic acidosis, which is primarily dependent on the amount of glucose available to be metabolized. The purpose of this study is to summarize preliminary experimental and clinical observations on the role of blood glucose in acute spinal cord injury. Between 1995 and 1996 we used the New York University (NYU) rat spinal cord injury model to test the following hypotheses: 1) Blood glucose levels increase with injury severity. 2) Fasting protects from hyperglycemia and prevents secondary damage to the spinal cord. 3) Postinjury-induced hyperglycemia (dextrose 5% 2 gm/Kg) enhances spinal lesion volume. From a clinical perspective, we reviewed blood glucose records of 47 patients admitted to the Department of Neurosrgery in Verona, between 1991 and 1995, within 24 hours of acute spinal cord injury in order to determine: a) the incidence of hyperglycemia (> 140 mg/dl); b) the correlation between blood glucose and injury severity; and c) the role of methylprednisolone in affecting blood glucose. Results indicate that in a graded spinal cord injury model: 1) Early after injury, more severe contusions support significantly higher blood glucose levels. 2) Fasting overnight does not directly affect spinal cord lesion volume but influences blood gases, and we observed that a slightly systemic acidosis plays a minor neuroprotective role. Fasting also ensures more consistent normoglycemic baseline blood glucose values. 3) Postinjury-induced moderate hyperglycemia (160-190 mg/dl) does not significantly affect spinal cord injury. In the clinical study, we observed that during the first 24 hours after spinal cord injury: a) Glycemia ranges between 90 and 243 mg/dl (mean value 143 mg/dl), and close to 50% of the patients present blood glucose values higher than normal. b) Methylprednisolone administration is not associated to significantly higher blood glucose levels. c) There is a trend for larger glucose rises with more severe injury.

Catecholamine-induced hypertension in lumbosacral paraplegia: five case reports

Hypertension in the patient with SCI is relatively rare and generally restricted to patients with high-level injuries where autonomic dysreflexia can occur. Resting blood pressure in individuals with SCI has been described as lower than that in the normal population. This report describes five previously normotensive teenagers with subsequent paraplegia as a result of gunshot wounds who presented with hypertension secondary to idiopathic elevation of plasma or urinary catecholamine levels. A clonidine suppression test was used as a neuroprobe to inhibit centrally mediated sympathetic outflow, excluding the probability of an extra-axial autonomous catecholamine-secreting tumor as the possible source of hypertension. Positive suppression was achieved in four patients (41%, 37.2%, 4.8%, and 37.2% decreases). One patient had values corresponding to orthostatic changes (an increase of 63%) because of poor compliance with the test. This patient was lost to follow-up; in the remaining four, hypertension resolved at 12, 8, 9, and 6 weeks postinjury. The increased circulating catecholamine level appears to be promoted by a centrally mediated response to the SCI. Elevated blood pressure probably results from an upgraded receptor regulation or an increased receptor sensitivity on the affected cells in the absence of restraining spinal reflexes. The pathophysiology of such hypertension seems to be secondary to autonomic dysfunction and, although it may be transient, it should be treated promptly and reevaluated periodically until stabilization is achieved.

Changes in norepinephrine and histamine in monkey spinal cords traumatized by weight drop and compression

Changes in norepinephrine and histamine levels in the spinal cord of monkeys at 1/2, 2, and 4 hours after 200 g cm of contusion injury, 50 g of compression injury, and 2 hours of decompression following 4 hours of compression were studied in the traumatized and an adjacent nontraumatized segment. Norepinephrine levels were elevated in the traumatized segment at 1/2, 2, and 4 hours after contusion injury and in the adjacent nontraumatized segment at 1/2 hour. Compression of 1/2 and 2 hours caused elevation of norepinephrine in both the traumatized and nontraumatized segments. On decompressing the values of norepinephrine reverted to near normal levels. Histamine content increased in the traumatized segment at 2 and 4 hours after contusion injury and in the adjacent nontraumatized segment at 2 hours. Compression injury did not change histamine levels, but decompression caused an increase. The possible influence of simultaneous changes in norepinephrine and histamine levels on the vessels following injury is discussed.

Studies of experimental cervical spinal cord transection. Part II: Plasma norepinephrine levels after acute cervical spinal cord transection

Plasma concentrations of norepinephrine (NE) were measured by a radioenzymatic assay technique before and serially after laminectomy at the C-6 level in 14 anesthetized dogs. In half the animals, no further procedures were carried out (control group); in the other dogs, cervical cord transection was performed in addition to laminectomy (experimental group). Mean plasma NE levels were similar in both groups after laminectomy and before cord interruption. In the control group, NE levels increased gradually for 2 hours after the procedure. In the group with cord transection, however, NE rose immediately after transection to 267% of the baseline value, then fell to 25% of the plasma NE level in the control group at 30 minutes, 29% at 60 minutes, and 15% at 120 minutes. Cervical spinal cord transection, therefore, results in an abrupt but short-lived increase in plasma NE concentrations. These changes in plasma NE levels may explain, at least in part, the hemodynamic alterations and the acute central hemorrhagic necrosis that occur after high spinal cord trauma.

Microscopic analysis of early histopathological spinal cord alterations following trauma in normal and cathecholamine-depleted cats

The progressive histopathological sequence over the first 3 hr after a 400 g-cm blunt injury to the spinal cord of catecholamine (CA)-intact and CA-depleted cats is described. Norepinephrine levels were measured in all animals. The experiments were designed to determine the role of CA in progressive hemorrhagic necrosis of the spinal cord by removing CA from one group of animals prior to trauma. A second group of CA-intact animals was subjected to identical experimentally-induced trauma. Upon analysis of the histopathological changes, it appears that the sequential nature of the development of hemorrhagic necrosis is both qualitatively and quantitatively similar in both experimental groups. The general conclusion is drawn that catecholamines in greater than normal amounts are present at the lesion site after trauma, but these catecholamines are probably not involved in the process of central hemorrhagic necrosis.

Norepinephrine levels in traumatized spinal cord of catecholamine-depleted cats

This study was designed to elucidate the origin of norepinephrine (NE) measured in spinal cord following trauma. In normal cats the NE concentration at the lesion site increased 63% over control 1 h following experimentally produced blunt trauma (400 g-cm). Spinal cords of adrenalectomized cats were also traumatized, but there was no increase in NE levels 1 h post-trauma. Spinal cord NE levels in these animals were not significantly different from normal or adrenalectomized non-injured controls. In the absence of one of the major peripheral sources of catecholamine, the adrenal medulla, our decreased NE levels prompt us to disagree with the hypothesis that NE measured in injured spinal cord is liberated from intrinsic neuronal systems. It is likely that the mechanism of NE accumulation is directly related to increased circulating levels of NE. The authors speculate on a possible reason for the conflicting results obtained by different laboratories in this area of research.