Homocysteine and hypertension in persons with spinal cord injury

Prevalence of hypertension and associated risk factors in people with long-term spinal cord injury living in the Netherlands

PURPOSE

To describe the prevalence of hypertension and associated risk factors in people with long-term spinal cord injury (SCI) and to compare the prevalence of high blood pressure and/or the use of antihypertensive drugs with the prevalence in the Dutch general population.

METHOD

Multicentre cross-sectional study (N = 282). Hypertension was defined as a systolic blood pressure (SBP) of ≥140 mmHg and/or a diastolic blood pressure (DBP) of ≥90 mmHg after ≥2 blood pressure measurements during ≥2 doctor visits. High blood pressure was defined as a single measurement of a SBP of ≥140 mmHg and/or a DBP of ≥90 mmHg.

RESULTS

The prevalence of hypertension was 21.5%. Significant predictors were: lesion level below C8 (T1-T6: OR =6.4, T7-L5: OR =10.1), history of hypercholesterolemia (OR =4.8), longer time since injury (OR =1.1), higher age (OR =1.1). The prevalence of high blood pressure and/or the use of antihypertensive drugs was higher in men (T1-T6 lesion: 48%; T7-L5 lesion: 57%) and women (T1-T6 lesion: 48%; T7-L5 lesion: 25%) with a SCI below C8 compared to Dutch able-bodied men (31%) and women (18%).

CONCLUSION

High blood pressure is common in people with SCI. Screening for hypertension during annual checkups is recommended, especially in those with a SCI below C8. Implications for Rehabilitation High blood pressure is common in people with long-term SCI living in the Netherlands and its prevalence is higher in both men and women with a spinal cord lesion level below C8 compared with the age-matched Dutch general population. It is recommended to screen for hypertension during annual checkups in people with SCI, especially in those with a higher risk of developing hypertension, e.g. those with a spinal cord lesion level below C8 and an age of ≥45 years or a time since injury of ≥20 years. When a high blood pressure is measured in people with SCI, they should receive a further assessment of the blood pressure according to the available guidelines for the general population, including ambulatory 24 h-blood pressure monitoring.

Inflammogenesis of Secondary Spinal Cord Injury

Spinal cord injury (SCI) and spinal infarction lead to neurological complications and eventually to paraplegia or quadriplegia. These extremely debilitating conditions are major contributors to morbidity. Our understanding of SCI has certainly increased during the last decade, but remains far from clear. SCI consists of two defined phases: the initial impact causes primary injury, which is followed by a prolonged secondary injury consisting of evolving sub-phases that may last for years. The underlying pathophysiological mechanisms driving this condition are complex. Derangement of the vasculature is a notable feature of the pathology of SCI. In particular, an important component of SCI is the ischemia-reperfusion injury (IRI) that leads to endothelial dysfunction and changes in vascular permeability. Indeed, together with endothelial cell damage and failure in homeostasis, ischemia reperfusion injury triggers full-blown inflammatory cascades arising from activation of residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (neutrophils and macrophages). These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit. Therefore, our review considers the recent advances in SCI mechanisms, whereby it becomes clear that SCI is a heterogeneous condition. Hence, this leads towards evidence of a restorative approach based on monotherapy with multiple targets or combinatorial treatment. Moreover, from evaluation of the existing literature, it appears that there is an urgent requirement for multi-centered, randomized trials for a large patient population. These clinical studies would offer an opportunity in stratifying SCI patients at high risk and selecting appropriate, optimal therapeutic regimens for personalized medicine.

Prevalence of abnormal systemic hemodynamics in veterans with and without spinal cord injury

OBJECTIVE

Increased prevalence of heart rate and blood pressure abnormalities are evident in persons with spinal cord injury (SCI), but age, comorbid medical conditions, and prescription medication use may contribute. To determine differences in the prevalence of cardiac acceleration (heart rate ≥80 beats per minute), hypotension (blood pressure ≤110/70mmHg), orthostatic hypotension (OH) (-20/-10mmHg with upright positioning), and hypertension (HTN) (blood pressure ≥140/90mmHg) in veterans with and without SCI.

DESIGN

Observational trial.

SETTING

Medical center.

PARTICIPANTS

Subjects included veterans with SCI (n=62; cervical: tetraplegia, C3-8; high thoracic, T1-5; low thoracic, T7-L2) and veterans without SCI (n=160).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

We assessed medical history, prescription medication use, and heart rate and blood pressure during a routine clinical visit. Prevalence rates of cardiac acceleration, hypotension, OH, and HTN were calculated using binary logistic regression analysis with 95% confidence intervals. The influence of SCI status, age, smoking status, cardiovascular diagnoses, and use of prescribed antihypertensive medications on the prevalence of abnormal heart rate and blood pressure recordings was determined.

RESULTS

The diagnosis of HTN was reduced in the high thoracic and tetraplegia groups compared with the non-SCI and low thoracic groups. Use of antihypertensive medications was increased in the low thoracic group compared with the other 3 groups and was increased in the non-SCI group compared with the tetraplegia group. The prevalence of cardiac acceleration was reduced, and the prevalence of systolic hypotension was increased in the tetraplegia group. The prevalence of diastolic hypotension was increased in all SCI groups compared with the non-SCI group. For all analyses, increased prevalence of abnormal heart rate and blood pressure recordings was not further explained by the covariates, with the exception of age, cardiovascular diagnoses, and antihypertensive medications in the cardiac acceleration model; however, SCI status remained significant and was the dominant predictor variable.

CONCLUSIONS

Our data suggest that SCI status contributes to the prevalence of cardiac acceleration and systolic and diastolic hypotension regardless of cardiovascular medical conditions or prescription antihypertensive medication use.

Neuronal regulation of expression of hydrogen sulfide-producing enzyme cystathionine β-synthase in rat spinal cord astrocytes

Cystathionine β-synthase (CBS), expressed in astrocytes, generates a gaseous neuromodulator, hydrogen sulfide (H2S) in the central nervous system (CNS). However, little is known about the regulatory mechanisms of astrocytic CBS expression and activity. This study evaluated the influence of neurons on astrocytic CBS expression by employing multiple culture systems. Substantial CBS expression was observed in the intact neonatal rat spinal cord, while CBS content was markedly reduced in an astrocyte-enriched culture prepared from the neonatal spinal cord. Immunofluorescence analysis confirmed the localization of spinal cord CBS in astrocytes, but not in neurons. Although CBS expression was weak in the embryonic rat spinal cord, enzyme levels were time-dependently increased in a neuron/astrocyte mixed culture originating from embryonic spinal cord. The reduced CBS expression in isolated neonatal astrocytes was restored by co-culture with embryonic neurons. Together with the observed CBS expression levels, H2S production was relatively low in astrocytes cultured alone, but was considerably higher in astrocytes cultured with neurons. These results indicate that neurons are essential for maintaining the expression and H2S-producing activity of astrocytic CBS in the rat spinal cord.

Allostatic load and spinal cord injury: review of existing research and preliminary data

OBJECTIVE

To introduce allostatic load (AL) as a framework for measuring stress-related outcomes after spinal cord injury (SCI) by identifying the number and nature of biomarkers investigated in existing studies and by generating preliminary data on AL in 30 persons with traumatic SCI.

METHODS

This systematic review and pilot study were conducted at a medical university in the southeastern United States. A review of literature published between 1993 and 2012 identified studies using 2 or more of 5 classes of AL biomarkers. We then collected data on 11 biomarkers (n = 30) from self-selected participants using physical exams and blood and urine specimen collection. These included waist to hip ratio, systolic and diastolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, dihydroepiandrosterone, glycosylated hemoglobin, C-reactive protein, interleukin-6, and cortisol, norepinephrine, and epinephrine normalized by 12-hour creatinine.

RESULTS

We were unable to identify any studies investigating AL biomarkers from each of the 5 areas or any studies specifically proposing to investigate AL. AL scores were relatively low, with metabolic indicators being the most elevated and neuroendocrine the least elevated.

CONCLUSIONS

AL is a promising, yet underutilized, construct that may be feasibly assessed after SCI.

A prospective report on the prevalence of heart rate and blood pressure abnormalities in veterans with spinal cord injuries

OBJECTIVE

Decentralized autonomic cardiovascular regulation may lead to increased prevalence of heart rate (HR) and blood pressure (BP) abnormalities in veterans with SCI. In addition, comorbid medical conditions and prescription medication use may increase HR and BP abnormalities. These abnormalities include bradycardia, and tachycardia, hypotension, hypertension as well as autonomic dysreflexia and orthostatic hypotension; the prevalence of which is unknown.

DESIGN

HR and BP data were measured during a routine annual physical examination in 64 veterans with SCI. Measurements of HR and BP were recorded in the seated and supine positions to document the influence of body position and to document intra-subject variability in these assessments.

RESULTS

All subjects were chronically injured (20 ± 14 years), 33 subjects were tetraplegic (T: C3-C8), nine had high paraplegia (HP: T1-T6), and 22 had low paraplegia (LP: T7-L2). Regardless of position, the prevalence of bradycardia was increased in the T group, whereas prevalence of tachycardia was increased in the HP and LP groups. Systolic hypotension was more common in the T and HP groups than the LP group and positional effects were most evident in the T group. Systolic hypertension was comparable in the T and HP groups but was twice as prevalent in the LP group. Increased prevalence of individuals with three or more medical conditions and prescribed three or more medications which might influence HR and BP was observed.

CONCLUSION

Decentralized autonomic regulation, comorbid medical conditions, and prescription medication use in veterans with SCI result in HR and BP abnormalities; our data suggest that these abnormalities vary depending on the level of injury and orthostatic positioning.

Pulse wave velocity for assessment of arterial stiffness among people with spinal cord injury: a pilot study

BACKGROUND/OBJECTIVE

The most significant complication and leading cause of death for people with spinal cord injury (SCI) is coronary artery disease (CAD). It has been confirmed that aortic pulse wave velocity (PWV) is an emerging CAD predictor among able-bodied individuals. No prior study has described PWV values among people with SCI. The objective of this study was to compare aortic (the common carotid to femoral artery) PWV, arm (the brachial to radial artery) PWV, and leg (the femoral to posterior tibial artery) PWV in people with SCI (SCI group) to able-bodied controls (non-SCI group).

METHODS

Participants included 12 men with SCI and 9 non-SCI controls matched for age, sex, height, and weight. Participants with a history of CAD or current metabolic syndrome were excluded. Aortic, arm, and leg PWV was measured using the echo Doppler method.

RESULTS

Aortic PWV (mean +/- SD) in the SCI group (1,274 +/- 369 cm/s) was significantly higher (P < 0.05) than in the non-SCI group (948 +/- 110 cm/s). There were no significant between-group differences in mean arm PWV (SCI: 1,152 +/- 193 cm/s, non-SCI: 1,237 +/- 193 cm/s) or mean leg PWV (SCI: 1,096 +/- 173 cm/s, non-SCI: 994 +/- 178 cm/s) values.

CONCLUSIONS

Aortic PWV was higher among the SCI group compared with the non-SCI group. The higher mean aortic PWV values among the SCI group compared with the non-SCI group indicated a higher risk of CAD among people with SCI in the absence of metabolic syndrome.

Nutrient intake and body habitus after spinal cord injury: an analysis by sex and level of injury

BACKGROUND/OBJECTIVES

To examine nutrient intake and body mass index (BMI) in the spinal cord injury (SCI) population according to level of injury and sex.

DESIGN

Cross-sectional study conducted at 2 SCI treatment centers.

PARTICIPANTS/METHODS

Seventy-three community-dwelling individuals with C5-T12 ASIA Impairment Scale (AIS) A or B SCI. Subjects were divided into 4 groups: male tetraplegia (N = 24), male paraplegia (N = 37), female tetraplegia (N =1), and female paraplegia (N = 11). Mean age was 38 years; 84% were male; 34% were white, 41% were African American, and 25% were Hispanic. Participants completed a 4-day food log examining habitual diet. Dietary composition was analyzed using Food Processor II v 7.6 software.

RESULTS

Excluding the 1 woman with tetraplegia, total calorie intake for the other 3 groups was below observed values for the general population. The female paraplegia group tended to have a lower total calorie intake than the other groups, although macronutrient intake was within the recommended range. The male tetraplegia group, male paraplegia group, and the 1 woman with tetraplegia all had higher than recommended fat intake. Intake of several vitamins, minerals, and macronutrients did not meet recommended levels or were excessively low, whereas sodium and alcohol intake were elevated. Using adjusted BMI tables, 74.0% of individuals with SCI were overweight or obese.

CONCLUSIONS

Women with paraplegia tended to maintain healthier diets, reflected by lower caloric and fat intakes, fewer key nutrients falling outside recommended guidelines, and less overweight or obesity. Individuals with tetraplegia tended to take in more calories and had higher BMIs, and using adjusted BMI, the majority of the population was overweight or obese. The majority of people with SCI would benefit from nutritional counseling to prevent emerging secondary conditions as the population with SCI ages.