Haemodynamic, hormonal and urinary responses to postural change in tetraplegic and paraplegic man

Takotsubo cardiomyopathy in a chronic spinal cord injury patient with autonomic dysreflexia: A case report

Context: Takotsubo cardiomyopathy (TC) is a transient stress-induced cardiomyopathy with left ventricular dysfunction of unknown etiology. A well accepted theory for the pathophysiology of TC is attributed to a massive catecholamine release [1]. This case report will review a chronic tetraplegia patient who was diagnosed with TC after a severe episode of autonomic dysreflexia (AD). He experiences mild episodes of AD several times a day; however, he had never experienced the severity of symptoms that was associated with this episode which led to his hospitalization. Autonomic dysreflexia is a syndrome of imbalanced sympathetic input secondary to loss of descending central sympathetic control in spinal cord injury due to noxious stimuli below the level of the injury, which occurs when the injury level is at thoracic level 6 (T6) or above [2].Findings: In this specific case, it is presumed that the massive catecholamine release associated with this severe AD episode resulted in TC. Although TC has been diagnosed after other instances of acute stress, it is unknown for it to be diagnosed after AD in a chronic setting.Clinical Relevance: The long-term effects of AD have not been well studied, and this case illustrates the importance of education to recognize and manage AD in the spinal cord patient who frequently has episodes of AD.

Increased pulse wave velocity in persons with spinal cord injury: the effect of the renin-angiotensin-aldosterone system

Increased pulse wave velocity (PWV), a marker of cardiovascular disease (CVD), has been reported in otherwise healthy individuals with spinal cord injury (SCI) compared with age-matched uninjured controls. Due to decentralized descending sympathetic vascular control, individuals with injuries above T6 are prone to orthostatic hypotension and, as a result, depend on the renin-angiotensin-aldosterone system (RAAS) to maintain orthostatic blood pressure (BP). The purpose of this study was to determine resting PWV, a noninvasive surrogate of central arterial stiffness, in individuals with cervical (C4-T1; n = 11) and thoracic (T6-T12; n = 11) SCI, compared with age-matched controls (controls; n = 11). Next, our aim was to describe group differences in BP, plasma norepinephrine (NE), and renin response to head-up tilt (HUT). Finally, we sought to determine the relationship between PWV and the orthostatic change in BP, NE, and the plasma renin during HUT among the groups. PWV was significantly increased in both cervical (8.81 ± 1.91 m/s) and thoracic (7.36 ± 1.58 m/s) SCI compared with the controls (5.53 ± 0.95 m/s; P < 0.05). The change from supine to 60° HUT in BP and NE was significantly reduced and change in plasma renin was significantly increased in the cervical group compared with the thoracic and control groups. Group affiliation and change in plasma renin were significant predictors of PWV (R² = 0.63, P = 0.001). These data suggest that dependency on the RAAS for orthostatic BP maintenance may be associated with increased PWV and risk of CVD in the SCI population.NEW & NOTEWORTHY Our novel findings suggest that increased arterial stiffness in individuals with SCI may be due to greater dependency on the RAAS to maintain hemodynamic stability during an orthostatic challenge. Asymptomatic orthostatic hypotension can occur in persons with SCI during transition from the supine to the seated position and during other upright activities of daily living; however, it is seldom addressed by clinicians.

Improvements in bladder, bowel and sexual outcomes following task-specific locomotor training in human spinal cord injury

OBJECTIVE

Locomotor training (LT) as a therapeutic intervention following spinal cord injury (SCI) is an effective rehabilitation strategy for improving motor outcomes, but its impact on non-locomotor functions is unknown. Given recent results of our labs' pre-clinical animal SCI LT studies and existing overlap of lumbosacral spinal circuitries controlling pelvic-visceral and locomotor functions, we addressed whether LT can improve bladder, bowel and sexual function in humans at chronic SCI time-points (> two years post-injury).

STUDY DESIGN

Prospective cohort study; pilot trial with small sample size.

METHODS

Eight SCI research participants who were undergoing 80 daily one-hour sessions of LT on a treadmill using body-weight support, or one-hour of LT and stand training on alternate days, as part of another research study conducted at the Kentucky Spinal Cord Injury Research Center, University of Louisville, were enrolled in this pilot trial. Urodynamic assessments were performed and International Data Set questionnaire forms completed for bladder, bowel and sexual functions at pre-and post-training time points. Four usual care (non-trained; regular at-home routine) research participants were also enrolled in this study and had the same assessments collected twice, at least 3 months apart.

RESULTS

Filling cystometry documented significant increases in bladder capacity, voiding efficiency and detrusor contraction time as well as significant decreases in voiding pressure post-training relative to baseline. Questionnaires revealed a decrease in the frequency of nocturia and urinary incontinence for several research participants as well as a significant decrease in time required for defecation and a significant increase in sexual desire post-training. No significant differences were found for usual care research participants.

CONCLUSIONS

These results suggest that an appropriate level of sensory information provided to the spinal cord, generated through task-specific stepping and/or loading, can positively benefit the neural circuitries controlling urogenital and bowel functions.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03036527.

Cerebral salt wasting after traumatic brain injury: a review of the literature

Electrolyte imbalances are common among patients with traumatic brain injury (TBI). Cerebral salt wasting (CSW) is an electrolyte imbalance characterized by hyponatremia and hypovolemia. Differentiating the syndrome of inappropriate antidiuretic hormone and CSW remains difficult and the pathophysiological mechanisms underlying CSW are unclear. Our intent was to review the literature on CSW within the TBI population, in order to report the incidence and timing of CSW after TBI, examine outcomes, and summarize the biochemical changes in patients who developed CSW. We searched MEDLINE through 2014, hand-reviewed citations, and searched abstracts from the American Association for the Surgery of Trauma (2003-2014). Publications were included if they were conducted within a TBI population, presented original data, and diagnosed CSW. Publications were excluded if they were review articles, discussed hyponatremia but did not differentiate the etiology causing hyponatremia, or presented cases with chronic disease. Fifteen of the 47 publications reviewed met the selection criteria; nine (60%) were case reports, five (33%) were prospective and 1 (7%) was a retrospective study. Incidence of CSW varied between 0.8 - 34.6%. The populations studied were heterogeneous and the criteria used to define hyponatremia and CSW varied. Though believed to play a role in the development of CSW, increased levels of natriuretic peptides in patients diagnosed with CSW were not consistently reported. These findings reinforce the elusiveness of the CSW diagnosis and the need for strict and consistent diagnostic criteria.

Spinal cord injury increases the reactivity of rat tail artery to angiotensin II

Studies in individuals with spinal cord injury (SCI) suggest the vasculature is hyperreactive to angiotensin II (Ang II). In the present study, the effects of SCI on the reactivity of the rat tail and mesenteric arteries to Ang II have been investigated. In addition, the effects of SCI on the facilitatory action of Ang II on nerve-evoked contractions of these vessels were determined. Isometric contractions of artery segments from T11 (tail artery) or T4 (mesenteric arteries) spinal cord-transected rats and sham-operated rats were compared 6–7 weeks postoperatively. In both tail and mesenteric arteries, SCI increased nerve-evoked contractions. In tail arteries, SCI also greatly increased Ang II-evoked contractions and the facilitatory effect of Ang II on nerve-evoked contractions. By contrast, SCI did not detectably change the responses of mesenteric arteries to Ang II. These findings provide the first direct evidence that SCI increases the reactivity of arterial vessels to Ang II. In addition, in tail artery, the findings indicate that Ang II may contribute to modifying their responses following SCI.

Effects of acute nitric oxide synthase inhibition on lower leg vascular function in chronic tetraplegia

BACKGROUND/OBJECTIVE

To improve our understanding of the lower-leg vascular responses of nitric oxide synthase inhibition in persons with tetraplegia.

PARTICIPANTS

Six people with chronic tetraplegia and 6 age-matched controls.

METHODS

Lower-leg relative vascular resistance and venous volume variation were obtained by venous occlusion plethysmography and blood pressure by auscultation at baseline. Postintravenous infusion of the nitric oxide synthase inhibitor NG-nitro-L-arginine-methyl-ester (1 mg x kg(-1) or placebo on separate days.

RESULTS

At baseline in the group with tetraplegia compared with controls, mean arterial pressure and relative vascular resistance of the leg were significantly lower. After nitric oxide synthase inhibition, mean arterial pressure and lower leg vascular resistance were significantly elevated in both groups. There were no group or intervention differences in venous volume variation.

CONCLUSION

These preliminary results suggest that nitric oxide synthase inhibition with 1 mg x kg(-1) N(G)-nitro-L-arginine-methyl-ester normalizes seated blood pressure and lower leg vascular resistance to control group baseline levels.

Adrenal gland volume after spinal cord injury

OBJECTIVE

Spinal cord injury in adult men may result in hypothalamic-pituitary-adrenal axis dysfunction. Atrophy of adrenal glands was speculated in these patients. This study was undertaken to clarify the functional-anatomic correlation between adrenal volume and body surface area in subjects with spinal cord injury with impaired adrenal reserve.

DESIGN

Twenty male subjects with chronic spinal cord injury with impaired adrenal reserve were identified by adrenocorticotropic hormone stimulation test from a group of 42 subjects. All subjects with spinal cord injury and healthy volunteers underwent computed tomographic imaging with contiguous 3-mm section over adrenal glands for volumetric measurements. Ten pairs of subjects with spinal cord injury and controls with matched height and weight were included in the statistical analysis.

RESULTS

Significantly increased relative adrenal volumes were noted among subjects with chronic spinal cord injury and impaired adrenal reserve as compared with the body weight-matched and height-matched control group.

CONCLUSIONS

Increased relative adrenal volumes were found after chronic spinal cord injury. Hyperplasia of the zona glomerulosa may be the cause of increased relative adrenal volume after chronic spinal cord injury.

Nocturnal polyuria and antidiuretic hormone levels in spinal cord injury

OBJECTIVE

To establish baseline ADH levels in spinal cord injury patients and to evaluate whether spinal cord patients have attenuation of diurnal variation of ADH similar to children with enuresis and elderly with nocturnal polyuria.

DESIGN

Twenty-seven healthy quadriplegic patients, ASIA impairment scale A, were evaluated for serum ADH levels at night and during the day.

MAIN OUTCOME MEASURES

Evaluation of whether bladder overdistention caused by attenuation of diurnal variation of ADH is responsible for the episodes of autonomic dysreflexia and recurrent urinary tract infections in spinal cord injury patients who are on intermittent catheterization for bladder management.

RESULTS

A lack of diurnal variation of ADH in the subject population.

CONCLUSIONS

A trial of desaminocystein-D-arginine vasopressin (DDAVP) should be considered for patients with established attenuation of the diurnal variation ADH.

Reversible changes in osmoregulation of vasopressin release due to impaired water excretion

Studies of renal water handling and the effects of altered hydration and posture on the osmoregulation of vasopressin release were performed on a chronically hyponatremic patient with complete cervical spinal cord transection at the C-5 level. Acute oral water loading studies showed marked reduction in free water clearance and urine diluting ability, despite appropriate suppression of plasma vasopressin concentrations. Orthostatic reductions in arterial blood pressure during head-up tilting and following the assumption of sitting posture were also demonstrable, and may have contributed to, but could not fully account for, the defect in renal water excretion, which persisted in supine posture. Hypertonic sodium chloride infusion studies performed before fluid restriction showed that low preinfusion plasma osmolality was associated with a reduced osmotic threshold for vasopressin release, which was subsequently corrected by a period of fluid restriction that restored the patient's plasma osmolality to a normal level. This shift in osmotic threshold can be inferred from both linear regression and log-linear regression analysis of the data. These studies show that marked impairment of renal water excretion coupled with unrestricted water intake can result in altered osmoregulation of vasopressin release in association with persistent plasma hypo-osmolality, which can be corrected by fluid restriction.