Cardiovascular responses to vibrostimulation for sperm retrieval in men with spinal cord injury

Autonomic dysreflexia in urological practice: pathophysiology, prevention and treatment considerations

PURPOSE

Spinal cord injury (SCI) leads to sensorimotor impairments; however, it can also be complicated by significant autonomic dysfunction, including cardiovascular and lower urinary tract (LUT) dysfunctions. Autonomic dysreflexia (AD) is a dangerous cardiovascular complication of SCI often overlooked by healthcare professionals. AD is characterized by a sudden increase in blood pressure (BP) that can result in severe cardiovascular and cerebrovascular complications. In this review, we provide an overview on the clinical manifestations, risk factors, underlying mechanisms, and current approaches in prevention and management of AD.

METHODS

After conducting a literature research, we summarized relevant information regarding the clinical and pathophysiological aspects in the context of urological clinical practice CONCLUSIONS: The most common triggers of AD are those arising from LUT, such as bladder distention and urinary tract infections. Furthermore, AD is commonly observed in individuals with SCI during urological procedures, including catheterization, cystoscopy and urodynamics. Although significant progress in the clinical assessment of AD has been made in recent decades, effective approaches for its prevention and treatment are currently lacking.

Characterization of heart rate changes associated with autonomic dysreflexia during penile vibrostimulation and urodynamics

STUDY DESIGN

Secondary data analysis.

OBJECTIVES

To characterize autonomic dysreflexia (AD) associated heart rate (HR) changes during penile vibrostimulation (PVS) and urodynamic studies (UDS).

SETTING

University-based laboratory.

METHODS

We analyzed blood pressure (BP) and HR data, recorded continuously, from 21 individuals (4 females; median age 41 years [lower and upper quartile, 37; 47]; median time post-injury 18 years [7; 27]; all motor-complete spinal cord injury (SCI) except one; cervical SCI = 15, thoracic [T1-T6] SCI = 6), who underwent PVS (11/21) or UDS (10/21).

RESULTS

Overall, 47 AD episodes were recorded (i.e. PVS = 37, UDS = 10), with at least one AD episode in each participant. At AD threshold, bradycardia was observed during PVS and UDS in 43% and 30%, respectively. At AD peak (i.e., maximum increase in systolic BP from baseline), bradycardia was observed during PVS and UDS in 65% and 50%, respectively. Tachycardia was detected at AD peak only once during UDS. Our study was limited by a small cohort of participants and the distribution of sex and injury characteristics.

CONCLUSIONS

Our findings reveal that AD-associated HR changes during PVS and UDS appear to be related to the magnitude of systolic BP increases. Highly elevated systolic BP associated with bradycardia suggests the presence of severe AD. Therefore, we recommend cardiovascular monitoring (preferably with continuous beat-to-beat recordings) during PVS and UDS to detect AD early. Stopping assessments before systolic BP reaches dangerously elevated levels, could reduce the risk of life-threatening complications in this cohort.

The susceptibility of cardiac arrhythmias after spinal cord crush injury in rats

High-level spinal cord injury (SCI) often interrupts supraspinal regulation of sympathetic input to the heart. Although it is known that dysregulated autonomic control increases the risk for cardiac disorders, the mechanisms mediating SCI-induced arrhythmias are poorly understood. Here, we employed a rat model of complete spinal cord crush injury at the 2nd/3rd thoracic (T2/3) level to investigate cardiac rhythm disorders resulting from SCI. Rats with T9 injury and naïve animals served as two controls. Four weeks after SCI, rats were implanted with a radio-telemetric device for electrocardiogram and blood pressure monitoring. During 24-h recordings, heart rate variability in rats with T2/3 but not T9 injury exhibited a significant reduction in the time domain, and a decrease in power at low frequency but increased power at high frequency in the frequency domain which indicates reduced sympathetic and increased parasympathetic outflow to the heart. Pharmacological blockade of the sympathetic or parasympathetic branches confirmed the imbalance of cardiac autonomic control. Activation of sympatho-vagal input during the induction of autonomic dysreflexia by colorectal distention triggered various severe arrhythmic events in T2/3 injured rats. Meanwhile, intravenous infusion of the β1-adrenergic receptor agonist, dobutamine, caused greater incidence of arrhythmias in rats with T2/3 injury than naïve and T9 injured controls. Together, the results indicate that high-level SCI increases the susceptibility to developing cardiac arrhythmias likely owing to compromised autonomic homeostasis. The T2/3 crush model is appropriate for studying abnormal cardiac electrophysiology resulting from SCI.

Cardiovascular and cerebrovascular responses to urodynamics testing after spinal cord injury: The influence of autonomic injury

Autonomic dysfunction is a prominent concern following spinal cord injury (SCI). In particular, autonomic dysreflexia (AD; paroxysmal hypertension and concurrent bradycardia in response to sensory stimuli below the level of injury) is common in autonomically-complete injuries at or above T6. AD is currently defined as a >20 mmHg increase in systolic arterial pressure (SAP) from baseline, without heart rate (HR) criteria. Urodynamics testing (UDS) is performed routinely after SCI to monitor urological sequelae, often provoking AD. We, therefore, aimed to assess the cardiovascular and cerebrovascular responses to UDS and their association with autonomic injury in individuals with chronic (>1 year) SCI. Following blood draw (plasma norepinephrine [NE]), continuous SAP, HR, and middle cerebral artery blood flow velocity (MCAv) were recorded at baseline (10-minute supine), during standard clinical UDS, and recovery (10-minute supine) (n = 22, age 41.1 ± 2 years, 15 male). Low frequency variability in systolic arterial pressure (LF SAP; a marker of sympathetic modulation of blood pressure) and cerebral resistance were determined. High-level injury (≥T6) with blunted/absent LF SAP (<1.0 mmHg²) and/or low plasma NE (<0.56 nmol•L⁻¹) indicated autonomically-complete injury. Known electrocardiographic markers of atrial (p-wave duration variability) and ventricular arrhythmia (T-peak–T-end variability) were evaluated at baseline and during UDS. Nine participants were determined as autonomically-complete, yet 20 participants had increased SAP >20 mmHg during UDS. Qualitative autonomic assessment did not discriminate autonomic injury. Maximum SAP was higher in autonomically-complete injuries (207.1 ± 2.3 mmHg) than autonomically-incomplete injuries (165.9 ± 5.3 mmHg) during UDS (p < 0.001). HR during UDS was reduced compared to baseline (p = 0.056) and recovery (p = 0.048) only in autonomically-complete lesions. MCAv was not different between groups or phases (all p > 0.05). Cerebrovascular resistance index was increased during UDS in autonomically-complete injuries compared to baseline (p < 0.001) and recovery (p < 0.001) reflecting intact cerebral autoregulation. Risk for both atrial and ventricular arrhythmia increased during UDS compared to baseline (p < 0.05), particularly in autonomically-complete injuries (p < 0.05). UDS is recommended yearly in chronic SCI but is associated with profound AD and an increased risk of arrhythmia, highlighting the need for continued monitoring during UDS. Our data also highlight the need for HR criteria in the definition of AD and the need for quantitative consideration of autonomic function after SCI.

Penile Vibratory Stimulation for Semen Retrieval in Men with Spinal Cord Injury: Patient Perspectives

Spinal cord injury (SCI) is a catastrophic event with sequelae that are not often apparent. For the spinal cord injured man, the inability to become a biologic father because of reproductive dysfunction becomes a major negative factor in his self-esteem and a hindrance to his social rehabilitation. Approximately, 90% of men with SCI develop ejaculatory dysfunction and only 10% can ejaculate by masturbation or during sexual activity. It is only over the last 40 years that it has been possible to properly study and understand the various factors contributing to the problem. Advances have been made in governmental and societal attitudes that have led to improvements in the treatment and rehabilitation of persons with SCI and other disabilities. It is now possible to retrieve sperm reliably and safely from men with SCI. Although their semen quality is often impaired, there is a very reasonable chance for achieving biologic fatherhood using assisted reproductive techniques. Penile vibratory stimulation (PVS) is a safe, reliable, efficient, and cost-effective, method of sperm retrieval that will produce an ejaculate in up to 86% of the patients with a level of injury T10 or rostral, which accounts for approximately 80% of the SCI population. Some motile sperm will be present in 90% of these ejaculates. In approximately 75% of the ejaculates, there will be greater than 5 million motile sperm, allowing a couple to explore all the options available to a couple seeking help in conceiving a child. The Male Fertility Program of the Miami Project to Cure Paralysis is at the leading edge of basic and clinical research contributing to the management of infertility in men with SCI. This review will outline “how we got there” enabling us to recommend PVS as the first choice in assisting men with SCI to become biologic parents.

Spinal cord injury impairs cardiac function due to impaired bulbospinal sympathetic control

Spinal cord injury chronically alters cardiac structure and function and is associated with increased odds for cardiovascular disease. Here, we investigate the cardiac consequences of spinal cord injury on the acute-to-chronic continuum, and the contribution of altered bulbospinal sympathetic control to the decline in cardiac function following spinal cord injury. By combining experimental rat models of spinal cord injury with prospective clinical studies, we demonstrate that spinal cord injury causes a rapid and sustained reduction in left ventricular contractile function that precedes structural changes. In rodents, we experimentally demonstrate that this decline in left ventricular contractile function following spinal cord injury is underpinned by interrupted bulbospinal sympathetic control. In humans, we find that activation of the sympathetic circuitry below the level of spinal cord injury causes an immediate increase in systolic function. Our findings highlight the importance for early interventions to mitigate the cardiac functional decline following spinal cord injury.

By combining experimental models with prospective clinical studies, the authors show that spinal cord injury causes a rapid reduction in cardiac function that precedes structural changes, and that the loss of descending sympathetic control is the major cause of reduced cardiac function following spinal cord injury.

Markers of susceptibility to cardiac arrhythmia in experimental spinal cord injury and the impact of sympathetic stimulation and exercise training

Injury to descending autonomic (sympathetic) pathways is common after high-level spinal cord injury (SCI) and associated with abnormal blood pressure and heart rate regulation. In individuals with high-level SCI, abnormal sympathovagal balance (such as during autonomic dysreflexia; paroxysmal hypertension provoked by sensory stimuli below the injury) is proarrhythmogenic. Exercise training is a key component of SCI rehabilitation and management of cardiovascular disease risk, but it is unclear whether exercise training influences susceptibility to cardiac arrhythmia. We aimed to evaluate: (i) whether susceptibility to arrhythmia increases in a rodent-model of SCI; (ii) the impact of the sympathomimetic drug dobutamine (DOB) on arrhythmia risk; (iii) whether exercise training ameliorates arrhythmia risk. Twenty-one Wistar rats were divided into 3 subgroups: T2-contusive SCI (T2, n = 7), T2-contusive SCI completing passive hindlimb cycling training (PHLC, n = 7), and T10-contusive SCI (T10, n = 7). Known electrocardiographic arrhythmia markers and heart rate variability parameters were evaluated before (PRE), 1-week (POST) and 5-weeks post-SCI (TERM) at baseline and during DOB infusion (30 μg/kg/min). Baseline markers of arrhythmia risk were increased in both T2 and T10 animals. DOB decreased R-R interval (p < 0.001), and increased markers of risk for ventricular arrhythmia, particularly in high-level (T2) animals (p < 0.05). Exercise training blunted the exacerbation of markers of arrhythmia risk in the presence of DOB. Markers of risk for cardiac arrhythmia are increased in experimental SCI, and DOB further increases arrhythmia risk in high-level SCI. Exercise training did not improve markers of arrhythmia risk at rest, but did ameliorate markers of arrhythmia risk during sympathetic stimulation.

Neural Control and Physiology of Sexual Function: Effect of Spinal Cord Injury

Objective: To present the current understanding of normal anatomy, physiology, sexual physiology, pathophysiology and the consequential sexual changes and dysfunctions following a spinal cord injury (SCI). Methods: Narrative review of the latest literature. Results: Peripheral innervations of the pelvis involve 3 sets of efferent neurons coordinated though the pelvic plexus (somatic, thoracolumbar sympathetic, and sacral parasympathetic), and these are under cerebral descending excitatory and inhibitory control. SCI, depending on the level of lesion and completeness, can alter this cerebral control, affecting the psychological and reflexogenic potential for genital arousal and also ejaculation and orgasm. During arousal, nitric oxide is the main neurotransmitter for smooth muscle relaxation in both male and female erectile tissue. In men, erection, ejaculation, and orgasm are under separate neurological control and can be individually affected by SCI. Conclusions: Since sexual function is rated amongst the highest priorities by individuals living with SCI, methods employed to affect the neurological changes to maximize sexual neurophysiology prior to initiating medical therapies including paying attention to sexual sensate areas and visceral signals with mindfulness techniques, practicing body mapping, and sexual stimulation of sensate areas to encourage neuroplasticity. Attention should be paid to the biopsychosocial sexual contexts within which persons with SCI live to maximize their sexual and fertility rehabilitation.

A Community Perspective on Bowel Management and Quality of Life after Spinal Cord Injury: The Influence of Autonomic Dysreflexia

Autonomic dysfunction is common in individuals with spinal cord injury (SCI) and leads to numerous abnormalities, including profound cardiovascular and bowel dysfunction. In those with high-level lesions, bowel management is a common trigger for autonomic dysreflexia (AD; hypertension provoked by sensory stimuli below the injury level). Improving bowel care is integral for enhancing quality of life (QoL). We aimed to describe the relationships between bowel care, AD, and QoL in individuals with SCI. We performed an online community survey of individuals with SCI. Those with injury at or above T7 were considered at risk for AD. Responses were received from 287 individuals with SCI (injury levels C1-sacral and average duration of injury 17.1 ± 12.9 [standard deviation] years). Survey completion rate was 73% (n = 210). Bowel management was a problem for 78%: it interfered with personal relationships (60%) and prevented staying (62%) and working (41%) away from home. The normal bowel care duration was >60 min in 24% and most used digital rectal stimulation (59%); 33% reported bowel incontinence at least monthly. Of those at risk for AD (n = 163), 74% had AD symptoms during bowel care; 32% described palpitations. AD interfered with activities of daily living in 51%. Longer durations of bowel care (p < 0.001) and more severe AD (p = 0.04) were associated with lower QoL. Bowel management is a key concern for individuals with SCI and is commonly associated with symptoms of AD. Further studies should explore ways to manage bowel dysfunction, increase self-efficacy, and ameliorate the impact of AD to improve QoL.

Alarming blood pressure changes during routine bladder emptying in a woman with cervical spinal cord injury

INTRODUCTION

Many individuals with high-level spinal cord injury (SCI) experience secondary conditions such as autonomic dysreflexia (AD), which is a potentially life-threatening condition comprising transient episodes of hypertension up to 300 mmHg. AD may be accompanied by symptoms and signs such as headache, flushing, and sweating. Delay in AD recognition and management is associated with increased incidence of cardiovascular events and disease. As it is commonly triggered by bladder distension, AD continues to be a major concern for individuals living with SCI, both on a daily basis and in the long-term.

CASE PRESENTATION

A 58-year-old woman with C3 AIS B SCI presented with low resting blood pressure (BP) at 100/64 mmHg. She reported frequent episodes of AD that were most commonly attributed to urinary bladder filling. During our testing session, her systolic BP rose to 130 mmHg, at which point her care aide stepped in to utilize the Credé maneuver, which was part of her daily routine for bladder emptying. Application of suprapubic pressure further elevated her systolic BP to 230 mmHg. Throughout the episode of AD, the participant experienced a pounding headache and erythema above the LOI.

DISCUSSION

Clinical guidelines for bladder management after SCI recommend avoiding the Credé maneuver due to potential complications such as hernia or bruising. This current case report demonstrates the additional risk of inducing AD and dangerously high BP elevation.

Orgasm and SCI: what do we know?

STUDY DESIGN

narrative review OBJECTIVES: To determine the percentage of persons with SCI able to achieve orgasm and ejaculation, the associations between ejaculation and orgasm and the subjective and autonomic findings during these events, and the potential benefits with regards to spasticity.

SETTING

Two American medical centers METHODS: Data bases were searched for the terms orgasm and SCI and ejaculation and SCI. Search criteria were human studies published in English from 1990 to 12/2/2016.

RESULTS

Approximately 50% of sexually active men and women report orgasmic ability after SCI. There is a relative inability of persons with complete lower motor neuron injuries affecting the sacral segments to achieve orgasm. Time to orgasm is longer in persons with SCIs than able-bodied (AB) persons. With orgasm, elevated blood pressure (BP) occurs after SCI in a similar fashion to AB persons. With penile vibratory stimulation and electroejaculation, BP elevation is common and prophylaxis is recommended in persons with injuries at T6 and above. Dry orgasm occurs approximately 13% of times in males. Midodrine, vibratory stimulation, clitoral vacuum suction, and 4-aminopyridine may improve orgasmic potential.

CONCLUSIONS

Depending on level and severity of injury, persons with SCIs can achieve orgasm. Sympathetically mediated changes occur during sexual response with culmination at orgasm. Future research should address benefits of orgasm. Additionally, inherent biases associated with studying orgasm must be considered.

Prevalence of Autonomic Dysreflexia in Patients with Spinal Cord Injury above T6

Objective

To investigate the prevalence of autonomic dysreflexia (AD) using ambulatory blood pressure monitoring (ABPM) and the autonomic dysfunction following spinal cord injury (ADFSCI) questionnaire in patients with spinal cord injury (SCI) above T6.

Methods

Twenty-eight patients diagnosed with SCI above T6 were enrolled. ABPM and ADFSCI were utilized to assess AD. Using ABPM, systolic blood pressure (SBP), diastolic blood pressure, and heart rate (HR) were measured at 30-minute intervals. AD was defined as SBP 20 mmHg higher than basal SBP, and the number of AD events was counted. The ADFSCI questionnaire evaluates the severity and frequency of the AD symptoms.

Results

According to the ABPM, AD occurred in 26 patients and AD events occurred 5.8 ± 4.7 times. Average daytime and nighttime SBP were 119.9 ± 18.8 mmHg and 123.8 ± 21.2 mmHg, respectively, and the nighttime mean SBP appeared to be 4 mmHg higher than daytime mean SBP. These findings suggest the loss of nocturnal BP dipping in SCI patients. ADFSCI results revealed that 16 of the patients evaluated were symptomatic while 12 were asymptomatic.

Conclusion

AD following SCI above T6 was highly prevalent and several patients seemed asymptomatic. These results suggest the necessity of proper diagnostic and therapeutic interventions for managing AD.

Paralympic Medicine: The Road to Rio

Over the past 10 years, our team has attended numerous Paralympic games and International Paralympic Committee (IPC)-sanctioned events where we have accumulated the largest data set to date from elite athletes with spinal cord injury (SCI). This empirical evidence has allowed us to address critical questions related to health and athletic performance in these incredibly medically complex individuals. Namely, does autonomic function influence performance? Can we account for this with the present sport classification? How can we prevent the doping practice of self-inducing life-threatening episodes of hypertension to improve performance (termed "boosting")? How does extremely high participation in routine upper-body wheelchair exercise impact cardiovascular and cerebrovascular disease risk? Is it possible to improve the sport classification to level the playing field between athletes with and without autonomic dysfunction? Herein, we will narratively address these questions, and provide our perspective on future directions and recommendations moving forward. Our extensive clinical experience and comprehensive dataset suggest preserved autonomic function is critical for elite performance. We will explore how an easy-to-execute test may be able to predict which individuals are most likely to develop autonomic dysfunctions that may negatively affect their health and performance. We also will evaluate the possibility that a level playing field may be even more difficult to establish than once thought, considering the importance of not only voluntary movement to performance, but also autonomic function. Finally, we also will discuss new changes in screening guidelines at Rio to assess the occurrence of boosting, which is a banned practice by the IPC.

Hemodynamic Adaptations to Regular Exercise in People With Spinal Cord Injury

Objective

To investigate the real-time cardiovascular response to the progressive overload exercise in different levels of spinal cord injury (SCI), and to find out whether regular exercise has effect on these cardiovascular responses.

Methods

The study enrolled 8 able-bodied individuals in the control group plus 15 SCI subjects who were divided into two groups by their neurological level of injury: high-level SCI group (T6 or above) and low-level SCI group (T7 or below). Also, subjects were divided into exercise group and non-exercise group by usual exercise habits. We instructed the subjects to perform exercises using arm ergometer according to the protocol and checked plethysmograph for the real time assessment of blood pressure, heart rate, and cardiac output.

Results

Six subjects were included in high-level SCI group (3 cervical, 3 thoracic injuries), 9 subjects in low-level SCI group (9 thoracic injuries), and 8 able-bodied individuals in control group. During arm ergometer-graded exercise, mean arterial pressure (MAP) was significantly lower in high-level SCI subjects of non-exercise group, compared with high-level SCI subjects of exercise group. In addition, HR was significantly higher in low-level SCI group compared with control group.

Conclusion

There are significant differences in mean arterial pressure of high-level SCI group according to usual exercise habits. We discovered that even in non-athlete high-level SCI, regular exercise can bring cardiac modulation through blood pressure control.

Cardiovascular Physiology and Responses to Sexual Activity in Individuals Living with Spinal Cord Injury

Background: Spinal cord injury (SCI) may profoundly impact autonomic function producing a variable degree of dysfunction in cardiovascular, bronchopulmonary, sweating, bladder, bowel, and sexual function. The cardiovascular system is crucially important for sexual function, as it is responsible for blood flow shifts to cavernous and musculoskeletal tissue during sexual activity. This system is prone to 3 main abnormalities after SCI including low resting blood pressure (LRBP), orthostatic hypotension (OH), and autonomic dysreflexia (AD), all of which have important effects on sexual function. Methods: We review the current etiological mechanisms and manifestations of cardiovascular dysfunction after SCI and discuss how this is documented to impact sexual function in individuals living with SCI. Conclusions: All individuals with SCI at or above the T6 neurologic level have an increased risk of AD during sexual stimulation, with increasing risk associated with higher levels of injury and greater completeness of injury. AD can be silent, and individuals living with SCI should be aware of blood pressure values at baseline and during sexual activity. Clinicians performing vibrostimulation fertility procedures need to be aware of the risk of AD and consider pretreatment if needed. Researchers studying the cardiovascular response to sexual stimulation should consider continuous monitoring of blood pressure, as intermittent monitoring may underestimate true blood pressure values.

Cardiovascular Responses to Sexual Activity in Able-Bodied Individuals and Those Living with Spinal Cord Injury

Sexuality is an integral part of the human experience and persists in health and disability. The cardiovascular system is crucial to sexual function and can be affected profoundly by spinal cord injury (SCI). The effects of sexual activity on the cardiovascular system in SCI have not been summarized and compared with sexual activity in able-bodied individuals. A keyword search of Embase, PubMed, and Medline was conducted. From 471 retrieved studies for able-bodied individuals, 11 were included that met the strict criteria of medically uncomplicated participants. In the SCI literature, 117 studies were screened, with 18 meeting criteria. In able-bodied persons, sexual activity resulted in modest increases in systolic blood pressure peaking at orgasm (males of 163 mm Hg and females of 142 mm Hg) and returning to baseline shortly afterward. In persons with SCI, results varied from minimal changes to significant elevations in systolic blood pressure because of episodes of autonomic dysreflexia, especially in those with high thoracic and cervical lesions. Peak systolic blood pressure in these individuals was measured to be as high as 325 mm Hg. In the SCI population, more intense stimuli (including penile vibrostimulation and electroejaculation) tended to result in a greater increase in systolic blood pressure compared with self-stimulation. Studies that used continuous versus intermittent monitoring were more likely to report greater changes in systolic blood pressure. In able-bodied persons, sexual activity results in modest increases in blood pressure. In those with SCI, intense stimulation and higher injury levels result in a higher likelihood of autonomic dysreflexia and elevated blood pressure. Because of rapid changes in blood pressure, continuous monitoring is more advantageous than intermittent measurement, because the latter may miss peak values.

Contemporary Cardiovascular Concerns after Spinal Cord Injury: Mechanisms, Maladaptations, and Management

Cardiovascular (CV) issues after spinal cord injury (SCI) are of paramount importance considering they are the leading cause of death in this population. Disruption of autonomic pathways leads to a highly unstable CV system, with impaired blood pressure (BP) and heart rate regulation. In addition to low resting BP, on a daily basis the majority of those with SCI suffer from transient episodes of aberrantly low and high BP (termed orthostatic hypotension and autonomic dysreflexia, respectively). In fact, autonomic issues, including resolution of autonomic dysreflexia, are frequently ranked by individuals with high-level SCI to be of greater priority than walking again. Owing to a combination of these autonomic disturbances and a myriad of lifestyle factors, the pernicious process of CV disease is accelerated post-SCI. Unfortunately, these secondary consequences of SCI are only beginning to receive appropriate clinical attention. Immediately after high-level SCI, major CV abnormalities present in the form of neurogenic shock. After subsiding, new issues related to BP instability arise, including orthostatic hypotension and autonomic dysreflexia. This review describes autonomic control over the CV system before injury and the mechanisms underlying CV abnormalities post-SCI, while also detailing the end-organ consequences, including those of the heart, as well as the systemic and cerebral vasculature. The tertiary impact of CV dysfunction will also be discussed, such as the potential impediment of rehabilitation, and impaired cognitive function. In the recent past, our understanding of autonomic dysfunctions post-SCI has been greatly enhanced; however, it is vital to further develop our understanding of the long-term consequences of these conditions, which will equip us to better manage CV disease morbidity and mortality in this population.

Iatrogenic urological triggers of autonomic dysreflexia: a systematic review

STUDY DESIGN

This is a systematic review.

OBJECTIVE

The objective of this study was to review the literature on iatrogenic urological triggers of autonomic dysreflexia (AD).

SETTING

This study was conducted in an international setting.

METHODS

A systematic review was conducted from PubMed search using AD/ autonomic hyperreflexia and spinal cord injury (SCI). Studies selected for review involved iatrogenic urological triggers of AD in individuals with SCI, including original articles, previous practice guidelines, case reports and literature reviews. Studies that did not report AD or blood pressure (BP) assessments during urological procedures were excluded.

RESULTS

Forty studies were included for analysis and categorized into four groups: (1) urodynamics and cystometry; (2) cystoscopy and transurethral litholapaxy; (3) extracorporeal shock-wave lithotripsy (ESWL); and (4) other procedures. During urodynamics, the incidence of AD ranged from 36.7% to 77.8%. The symptomatic rate ranged from 50% to 65%, with AD symptoms seen predominantly in cervical SCI patients. The studies imply no consensus regarding the relationship between AD, neurogenic detrusor overactivity and detrusor sphincter dyssynergia. Without anesthesia, the majority of individuals develop AD during cystoscopy, transurethral litholapaxy and ESWL. The effectiveness of different anesthesia methods relies on blocking the nociceptive signals from the lower urinary tract (LUT) below the level of the neurological lesion. Other iatrogenic urological triggers were commonly associated with bladder filling.

CONCLUSION

The LUT triggers of episodes of AD are often associated with iatrogenic urological procedures. AD was more prevalent in cervical SCI than in thoracic SCI. To detect this potential life-threatening complication following cervical and high thoracic SCI, routine BP monitoring during urological procedures is highly recommended.

Selective alpha adrenergic antagonist reduces severity of transient hypertension during sexual stimulation after spinal cord injury

On a daily basis, the majority of those with high-level spinal cord injury have autonomic dysreflexia, which describes a life-threatening episode of transient extreme hypertension (i.e., as high as 300 mm Hg) as many as 90% of people living with this condition. Unfortunately, ejaculation is a major initiating factor for autonomic dysreflexia, which discourages sexual activity. In order to obtain a sperm specimen, or for initial assessment of fertility, penile vibrostimulation is clinically performed. Nifedipine, a selective calcium channel blocker, is the most commonly prescribed pharmaceutical for a priori management of autonomic dysreflexia secondary to ejaculation or other causes; however, it is limited because of its potential exacerbation of low resting pressure, which also affects this population. The present study examined the effect of a short-acting selective α1 antagonist (prazosin) on autonomic dysreflexia severity using a randomized placebo trial during medically supervised penile vibrostimulation in six males with cervical spinal cord injury. Beat-by-beat blood pressure and heart rate were recorded throughout penile vibrostimulation during placebo and prazosin-treated days. The increase in systolic blood pressure was mitigated during vibrostimulation in subjects administered prazosin as compared with those administered placebo (+140±19 mm Hg vs. +96±14 mmHg; p<0.05). On average, the peak in systolic blood pressure was 46 mm Hg lower during penile vibrostimulation when patients were administered prazosin (p<0.05), whereas resting blood pressure was not affected. Prazosin appears to be effective at reducing the severity of autonomic dysreflexia during sexual stimulation in patients with spinal cord injury, without exacerbating resting hypotension in high-level spinal cord injury.

Sympathetic skin responses and autonomic dysfunction in spinal cord injury

Sympathetic skin responses (SSRs), a measure of sympathetic cholinergic sudomotor function, have been used in the assessment of autonomic dysfunction in patients with spinal cord injury (SCI). This review highlights the basic mechanisms underlying SSRs as well as their application to the SCI population. We address the utility of SSRs in assessing autonomic function, the relationship between autonomic and sensorimotor impairment, and the association between SSRs and the sequelae of autonomic dysfunction in SCI, particularly autonomic dysreflexia and orthostatic hypotension. Overall, SSRs are a rapid, convenient and non-invasive method illustrating that the severity of autonomic impairment can be independent from sensorimotor impairment. We suggest that SSRs be used in conjunction with other validated autonomic tests in order to predict or document autonomic dysfunction in SCI.

Regional neurovascular coupling and cognitive performance in those with low blood pressure secondary to high-level spinal cord injury: improved by alpha-1 agonist midodrine hydrochloride

Individuals with high-level spinal cord injury (SCI) experience low blood pressure (BP) and cognitive impairments. Such dysfunction may be mediated in part by impaired neurovascular coupling (NVC) (i.e., cerebral blood flow responses to neurologic demand). Ten individuals with SCI >T6 spinal segment, and 10 age- and sex-matched controls were assessed for beat-by-beat BP, as well as middle and posterior cerebral artery blood flow velocity (MCAv, PCAv) in response to a NVC test. Tests were repeated in SCI after 10 mg midodrine (alpha1-agonist). Verbal fluency was measured before and after midodrine in SCI, and in the control group as an index of cognitive function. At rest, mean BP was lower in SCI (70 ± 10 versus 92 ± 14 mm Hg; P<0.05); however, PCAv conductance was higher (0.56 ± 0.13 versus 0.39 ± 0.15 cm/second/mm Hg; P<0.05). Controls exhibited a 20% increase in PCAv during cognition; however, the response in SCI was completely absent (P<0.01). When BP was increased with midodrine, NVC was improved 70% in SCI, which was reflected by a 13% improved cognitive function (P<0.05). Improvements in BP were related to improved cognitive function in those with SCI (r(2)=0.52; P<0.05). Impaired NVC, secondary to low BP, may partially mediate reduced cognitive function in individuals with high-level SCI.

Life-threatening outcomes associated with autonomic dysreflexia: a clinical review

Context Autonomic dysreflexia (AD) is a life-threatening complication of chronic traumatic spinal cord injury (SCI). Objective To document and provide insight into the life-threatening sequelae associated with AD. Methods A review was conducted to identify literature which documented cases of AD associated with life-threatening outcomes (and death). The search strategy comprised of a keyword search on the PubMed database as well as manual searches of retrieved articles. Outcomes were categorized into three main classes: central nervous system (CNS), cardiovascular (CV), and pulmonary. Results Thirty-two cases of death or life-threatening complications of AD were found. Twenty-three (72%) cases were CNS-related, seven (22%) cases were CV-related, and two (6%) cases were pulmonary-related. In total, seven (22%) deaths were noted as a direct result of complications following an AD attack. Conclusion AD is a well-known consequence of SCI among individuals with high thoracic and cervical injuries. Many of these individuals experience this condition on a daily basis. Medical personnel, care givers, and individuals with SCI should be aware of the importance of timely diagnosis and management of this life-threatening condition, which can result in a variety of significant complications including stroke, seizures, myocardial ischemia, and death.

Cardiovascular function after spinal cord injury: prevalence and progression of dysfunction during inpatient rehabilitation and 5 years following discharge

BACKGROUND

Autonomic dysfunction after spinal cord injury (SCI) is an under-researched area when compared with motor and sensory dysfunction. Cardiovascular autonomic dysfunction is a particular concern, leading to impaired control of blood pressure and heart rate.

OBJECTIVES

(1) To determine the prevalence of hypotension in individuals with SCI during and after rehabilitation; (2) To investigate changes in cardiovascular variables during and after rehabilitation; (3) To evaluate the influence of personal and lesion characteristics on cardiovascular variables.

METHODS

Cardiovascular variables (resting systolic [SAP] and diastolic [DAP] arterial pressures and resting [HRrest] and peak heart rates [HRpeak]) were measured on 5 test occasions: start of inpatient rehabilitation, 3 months later, at discharge, and at 1 and 5 years after discharge. The time course and effects of personal and lesion characteristics on cardiovascular variables were studied using multilevel regression analyses.

RESULTS

The prevalence of hypotension was unchanged during rehabilitation and for 5 years after discharge. Odds for hypotension were highest in those with cervical and high thoracic lesions, younger individuals, and men. DAP increased during the 5 years after discharge. HRrest decreased during and after rehabilitation. SAP, DAP, HRrest, and HRpeak were lowest in those with cervical and high thoracic lesions. SAP and DAP increased with age; HRpeak decreased with age.

CONCLUSIONS

These longitudinal data provide normative values for blood pressure and heart rate changes with time after injury according to lesion and personal characteristics. These results can be used to guide clinical practice and place changes in cardiovascular function caused by interventions in perspective.

Cardiac arrhythmias associated with spinal cord injury

CONTEXT/OBJECTIVES

To review the current literature to reveal the incidence of cardiac arrhythmias and its relation to spinal cord injury (SCI).

DATA SOURCE

MEDLINE database, 304 hits, and 32 articles were found to be relevant. The relevant articles all met the inclusion criteria: (1) contained original data (2) on cardiac arrhythmias (3) in humans with (4) traumatic SCI.

RESULTS

In the acute phase of SCI (1-14 days after injury) more cranial as well as more severe injuries seemed to increase the incidence of bradycardia. Articles not covering the first 14 days after injury, thus describing the chronic phase of SCI, showed that individuals with SCI did not have a higher incidence of cardiac arrhythmias compared with able-bodied controls. Furthermore, their heart rate did not differ significantly. Penile vibro-stimulation was the procedure investigated most likely to cause bradycardia, which in turn was associated with episodes of autonomic dysreflexia. The incidence of bradycardia was found to be 17-77% for individuals with cervical SCI. For individuals with thoracolumbar SCI, the incidence was 0-13%.

CONCLUSION

Bradycardia was commonly seen in the acute stage after SCI as well as during procedures such as penile vibro-stimulation and tracheal suction. These episodes of bradycardia were seen more often in individuals with cervical injuries. Longitudinal studies with continuous electrocardiogram recordings are needed to uncover the true relation between cardiac arrhythmias and SCI.

Disordered cardiovascular control after spinal cord injury

Damage to the spinal cord disrupts autonomic pathways, perturbing cardiovascular homeostasis. Cardiovascular dysfunction increases with higher levels of injury and greater severity. Disordered blood pressure control after spinal cord injury (SCI) has significant ramifications as cord-injured people have an increased risk of developing heart disease and stroke; cardiovascular dysfunction is currently a leading cause of death among those with SCI. Despite the clinical significance of abnormal cardiovascular control following SCI, this problem has been generally neglected by both the clinical and research community. Both autonomic dysreflexia and orthostatic hypotension are known to prevent and delay rehabilitation, and significantly impair the overall quality of life after SCI. Starting with neurogenic shock immediately after a higher SCI, ensuing cardiovascular dysfunctions include orthostatic hypotension, autonomic dysreflexia and cardiac arrhythmias. Disordered temperature regulation accompanies these autonomic dysfunctions. This chapter reviews the human and animal studies that have furthered our understanding of the pathophysiology and mechanisms of orthostatic hypotension, autonomic dysreflexia and cardiac arrhythmias. The cardiovascular dysfunction that occurs during sexual function and exercise is elaborated. New awareness of cardiovascular dysfunction after SCI has led to progress toward inclusion of this important autonomic problem in the overall assessment of the neurological condition of cord-injured people.

Transverse myelitis

Transverse myelitis (TM) includes a pathobiologically heterogeneous syndrome characterized by acute or subacute spinal cord dysfunction resulting in paresis, a sensory level, and autonomic (bladder, bowel, and sexual) impairment below the level of the lesion. Etiologies for TM can be broadly classified as parainfectious, paraneoplastic, drug/toxin-induced, systemic autoimmune disorders, and acquired demyelinating diseases. We discuss the clinical evaluation, workup, and acute and long-term management of patients with TM. Additionally, we briefly discuss various disease entities that may cause TM and their salient distinguishing features, as well as disorders that may mimic TM.

Electrocardiogram-based predictors for arrhythmia after spinal cord injury

PURPOSE

Individuals with spinal cord injury (SCI) have an increased risk of cardiac arrhythmias, particularly during autonomic dysreflexia (acute hypertensive episodes). This may be partly due to impaired autonomic control of the heart after SCI. The interval between the peak and end of the T-wave of the electrocardiograph (ECG) provides an index of transmural dispersion of repolarisation, a factor underlying the development of ventricular arrhythmias. Another ECG-based risk factor for ventricular arrhythmias is variability in the QT segment, the QT variability index (QTVI). Similarly, P-wave variability may be correlated with risk for atrial arrhythmias. We aimed to: (1) determine whether there are abnormalities in these parameters at rest in those with SCI; (2) determine correlations between these ECG parameters and severity of autonomic impairment after SCI.

METHODS

ECG intervals were determined using customised software from a 15 min ECG recording (lead II) in 28 SCI subjects and 27 controls. Autonomic severity of SCI was determined from sympathetic skin responses, low frequency systolic blood pressure variability, and plasma noradrenaline levels.

RESULTS

T(peak)-T(end) variability and QTVI were increased in those with autonomically complete SCI compared to controls. P-wave variability was increased in SCI individuals compared to controls, and was negatively correlated with plasma noradrenaline.

CONCLUSION

The higher T(peak)-T(end) variability, QTVI and P-wave variability in individuals with SCI could be markers of severity of injury to cardiac autonomic (sympathetic) pathways after SCI, and may represent new risk assessment parameters for predisposition to cardiac arrhythmias in this population.

Spectral analyses of cardiovascular control in rodents with spinal cord injury

The severity of injury to cardiovascular autonomic pathways following clinical spinal cord injury (SCI) can be evaluated with spectral analyses. Whether this technique provides a translatable assessment of cardiovascular autonomic function in rodent SCI is unknown. Beat-to-beat blood pressure and pulse interval were measured in male rats 1 month after complete T3 or T10 SCI, and in uninjured control animals. Univariate autoregressive spectral analyses were performed and the power of the low frequency (LF), high frequency (HF), and very low frequency (VLF) peaks identified. Frequency domain variables were correlated with the severity of orthostatic hypotension (OH) and the severity of hypertension during autonomic dysreflexia (AD). Total heart rate variability (HRV) and blood pressure variability (BPV) were reduced in animals with T3, but not T10, SCI. VLF and LF HRV were reduced and HF HRV was increased in animals with T3 SCI compared to controls; there were no changes in animals with T10 SCI. BPV in the VLF and LF range was reduced in animals with T3 SCI, but not T10 SCI. In all animals with SCI, severity of OH was positively correlated with LF BPV, and negatively correlated with HF BPV. Severity of AD was positively correlated with HF BPV and HF HRV, and negatively correlated with VLF HRV. Spectral analyses can detect alterations in cardiovascular autonomic function in animals with SCI at rest. These parameters underscore the distinct cardiovascular ramifications of high- versus low-thoracic SCI, and correlate with the severity of AD and OH, clinically-relevant measures of abnormal blood pressure control.

The isolated sympathetic spinal cord: Cardiovascular and sudomotor assessment in spinal cord injury patients: A literature survey

OBJECTIVES

To present a comprehensive approach to the assessment of the severity of the autonomic lesion in spinal cord injury (SCI) patients, with regard to the level of lesion. To discuss how to assess an isolated sympathetic spinal cord that has lost supraspinal control (sympathetically complete lesion).

METHOD

PubMed was searched for articles related to cardiovascular (mainly cold pressor test, respiratory and postural challenges) and sudomotor (sympathetic skin responses) tests that have been used. The results of these evaluations are analysed with regard to the site of stimulation (above or below the lesion) according to three types of SCI that offer typical autonomic reactions (tetraplegics, paraplegics at T6 and at T10).

RESULTS

Non-invasive cardiovascular and sudomotor testing allows the assessment of the isolated sympathetic spinal cord in SCI patients. Typical responses are found in relation with the level of the sympathetic lesion. Its definition would allow comparison with the somatic motor and sensory level of lesion of SCI patients and provide additional aid to the classification of those patients.

CONCLUSION

For research purposes on the integrity of the spinal sympathetic pathways, a battery of test approach is probably needed, using a combination of stimuli above and below the lesion, evaluating both cardiovascular and sudomotor pathways.

Challenges, concerns and common problems: physiological consequences of spinal cord injury and microgravity

INTRODUCTION

Similarities between the clinical presentation of individuals living with spinal cord injury (SCI) and astronauts are remarkable, and may be of great interest to clinicians and scientists alike.

OBJECTIVES

The primary purpose of this review is to outline the manner in which cardiovascular, musculoskeletal, renal, immune and sensory motor systems are affected by microgravity and SCI.

METHODS

A comprehensive review of the literature was conducted (using PubMed) to evaluate the hallmark symptoms seen after spaceflight and SCI. This literature was then examined critically to determine symptoms common to both populations.

RESULTS

Both SCI and prolonged microgravity exposure are associated with marked deteriorations in various physiological functions. Atrophy in muscle and bone, cardiovascular disturbances, and alterations in renal, immune and sensory motor systems are conditions commonly observed not only in individuals with SCI, but also in those who experience prolonged gravity unloading.

CONCLUSION

The preponderance of data indicates that similar physiological changes occur in both SCI and prolonged space flight. These findings have important implications for future research in SCI and prolonged space flight.

International spinal cord injury cardiovascular function basic data set

OBJECTIVE

To create an International Spinal Cord Injury (SCI) Cardiovascular Function Basic Data Set within the framework of the International SCI Data Sets.

SETTING

An international working group.

METHODS

The draft of the data set was developed by a working group comprising members appointed by the American Spinal Injury Association (ASIA), the International Spinal Cord Society (ISCoS) and a representative of the executive committee of the International SCI Standards and Data Sets. The final version of the data set was developed after review by members of the executive committee of the International SCI Standards and Data Sets, the ISCoS scientific committee, ASIA board, relevant and interested international organizations and societies, individual persons with specific interest and the ISCoS Council. To make the data set uniform, each variable and each response category within each variable have been specifically defined in a way that is designed to promote the collection and reporting of comparable minimal data.

RESULTS

The variables included in the International SCI Cardiovascular Function Basic Data Set include the following items: date of data collection, cardiovascular history before the spinal cord lesion, events related to cardiovascular function after the spinal cord lesion, cardiovascular function after the spinal cord lesion, medications affecting cardiovascular function on the day of examination; and objective measures of cardiovascular functions, including time of examination, position of examination, pulse and blood pressure. The complete instructions for data collection and the data sheet itself are freely available on the websites of both ISCoS (http://www.iscos.org.uk) and ASIA (http://www.asia-spinalinjury.org).

Autonomic function following cervical spinal cord injury

Spinal cord injury (SCI) is commonly associated with devastating paralysis. However, this condition also results in a variety of autonomic dysfunctions, primarily: cardiovascular, broncho-pulmonary, urinary, gastrointestinal, sexual, and thermoregulatory. SCI and the resultant unstable autonomic control are responsible for increased mortality from cardiovascular and respiratory disease among individuals with SCI. Injury level and severity directly correlate to the severity of autonomic dysfunctions following SCI. Following high cervical SCI, parasympathetic (vagal) control will remain intact, while the spinal sympathetic circuits will lose their tonic supraspinal autonomic control. On the other hand, in individuals with injury below the 5th thoracic segment, both the sympathetic and parasympathetic control of the heart and broncho-pulmonary tree are intact. As a result of injury level, individuals with quadriplegia versus those with paraplegia will have very different cardiovascular and respiratory responses. Furthermore, similar relationships can exist between the level of SCI and function of other organs that are under autonomic control (bladder, bowel, sweat glands, etc.). It is also important to appreciate that high cervical injuries result in significant respiratory dysfunctions due to the involvement of the diaphragm and a larger portion of the accessory respiratory muscles. Early recognition and timely management of autonomic dysfunctions in individuals with SCI are crucial for the long term health outcomes in this population.

A systematic review of the management of autonomic dysreflexia after spinal cord injury

OBJECTIVE

To review systematically the clinical evidence on strategies to prevent and manage autonomic dysreflexia (AD).

DATA SOURCES

A key word search of several databases (Medline, CINAHL, EMBASE, and PsycINFO), in addition to manual searches of retrieved articles, was undertaken to identify all English-language literature evaluating the efficacy of interventions for AD.

STUDY SELECTION

Studies selected for review included randomized controlled trials (RCTs), prospective cohort studies, and cross-sectional studies. Treatments reviewed included pharmacologic and nonpharmacologic interventions for the management of AD in subjects with spinal cord injury. Studies that failed to assess AD outcomes (eg, blood pressure) or symptoms (eg, headaches, sweating) were excluded.

DATA EXTRACTION

Studies were critically reviewed and assessed for their methodologic quality by 2 independent reviewers.

DATA SYNTHESIS

Thirty-one studies were assessed, including 6 RCTs. Preventative strategies to reduce the episodes of AD caused by common triggers (eg, urogenital system, surgery) primarily were supported by level 4 (pre-post studies) and level 5 (observational studies) evidence. The initial acute nonpharmacologic management of an episode of AD (ie, positioning the patient upright, loosening tight clothing, eliminating any precipitating stimulus) is supported by clinical consensus and physiologic data (level 5 evidence). The use of antihypertensive drugs in the presence of sustained elevated blood pressure is supported by level 1 (prazosin) and level 2 evidence (nifedipine and prostaglandin E(2)).

CONCLUSIONS

A variety of options are available to prevent AD (eg, surgical, pharmacologic) and manage the acute episode (elimination of triggers, pharmacologic); however, these options are predominantly supported by evidence from noncontrolled trials, and more rigorous trials are required.

Cutaneous vasoconstriction as a measure of incipient autonomic dysreflexia during penile vibratory stimulation in spinal cord injury

STUDY DESIGN

Measurement of haemodynamic responses, cutaneous blood flow and sweat release during penile vibratory stimulation (PVS) in spinal cord-injured men.

OBJECTIVE

To assess the validity of using markers of sympathetic activity (cutaneous blood flow and sweat release) as a measure of incipient autonomic dysreflexia during PVS in spinal cord-injured men.

SETTING

Prince of Wales Medical Research Institute, Australia.

SUBJECTS

Ten spinal cord-injured men with injuries ranging from C3 to T6.

METHODS

Continuous arterial pressure, intermittent auscultation, heart rate (HR), respiration, cutaneous blood flow and sweat release from both finger and toe were recorded during PVS.

RESULTS

Vibration of the penis caused immediate cutaneous vasoconstriction, but negligible sweat release, in the hands and feet of the quadriplegics and the feet of the paraplegics. Systolic blood pressure (BP) increased by up to 90 mm Hg, and a compensatory vagal bradycardia was observed in five of the six quadriplegics and two of the four paraplegic subjects.

CONCLUSION

Given that there was-in general-an inverse relationship between BP and skin blood flow, we conclude that continuous measurements of skin blood flow above and below the lesion can provide important information on the state of the sympathetic nervous system and early identification of reflexly evoked increases in sympathetic vasoconstrictor drive, below a spinal lesion. Coupled with a decrease in HR, this cutaneous vasoconstriction infers an increased BP.

Clinical correlates of frequency analyses of cardiovascular control after spinal cord injury

Spinal cord injury (SCI) has profound effects on cardiovascular autonomic function due to injury to descending autonomic pathways, and cardiovascular diseases are the leading causes of morbidity and mortality after SCI. Evaluation of cardiovascular autonomic dysfunction after SCI and appraisal of simple noninvasive autonomic assessments that are clinically meaningful would be useful to SCI clinicians and researchers. We aimed to assess supine and upright cardiovascular autonomic function from frequency analyses of heart rate and blood pressure variability (HRV and BPV) after SCI. We studied 26 subjects with chronic cervical or thoracic SCI and 17 able-bodied controls. We continuously recorded R-R interval (RRI, by ECG) and beat-to-beat blood pressure (by Finometer) in supine and seated positions. Cardiovascular control was assessed from spectral analysis of RRI and blood pressure time series. Cardiac baroreflex control was assessed from cross-spectral analyses of low-frequency spectra. Supine and upright low-frequency HRV and BPV were reduced in cervical SCI subjects, as were total BPV and HRV. Supine high-frequency HRV was reduced in thoracic SCI subjects. Cardiac baroreflex delay was increased in cervical SCI subjects. Supine frequency domain indexes were correlated with sympathetic skin responses, orthostatic cardiovascular responses, and plasma catecholamine levels. SCI results in reduced sympathetic drive to the heart and vasculature and increased baroreflex delay in cervical SCI subjects and reduced cardiac vagal tone in thoracic SCI subjects. Frequency analyses of autonomic function are related to clinical measures of autonomic control after SCI and provide useful noninvasive clinical tools with which to assess autonomic completeness of injury following SCI.

Orthostatic hypotension and autonomic pathways after spinal cord injury

Individuals with spinal cord injury (SCI) are prone to orthostatic hypotension (OH). We aimed to develop a simple bedside test to evaluate autonomic control following chronic SCI, and to identify those most at risk of OH and cardiovascular dysfunction. We studied 14 subjects with cervical SCI, 11 with thoracic SCI, and 17 able-bodied controls. We continuously recorded heart rate (HR; ECG) and beat-to-beat systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures (Finometer) while supine, and following the passive assumption of an upright seated position. Stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were calculated. Plasma catecholamines were determined. Motor and sensory loss was assessed using the American Spinal Injury Association (ASIA) impairment scale. Autonomic pathways were assessed from sympathetic skin responses (SSR). Cervical SCI subjects had lower supine HR, SAP, and noradrenaline levels than thoracic SCI and controls (p < 0.05), and lower DAP and MAP than controls (p < 0.05). When upright, HR increased in all groups (p < 0.05); SAP, DAP, and MAP increased (p < 0.01) in thoracic SCI and controls, but not in cervical SCI. Cervical SCI had larger postural falls in SV (p < 0.05) and CO, with smaller increases in TPR than the other two groups. Upright catecholamine levels were lower in cervical SCI (p < 0.05) than thoracic SCI and controls. Completeness of SCI assessed by ASIA scale did not necessarily correlate with autonomic completeness assessed by SSR. Cardiovascular control during orthostasis was impaired and OH was common in cervical SCI, but not thoracic SCI. SSR may identify those at greatest risk of orthostatic hypotension and impaired cardiovascular control. We advocate that assessments of autonomic function be included in the neurological evaluation of SCI, in addition to the ASIA assessment.