Unstable baseline blood pressure in chronic tetraplegia

Epidural stimulation with locomotor training ameliorates unstable blood pressure after tetraplegia. A case report

A male with C7 complete tetraplegia participated in 14 weeks of body weight supported treadmill training (BWSTT) combined with spinal cord epidural stimulation (SCES), 4 weeks of no intervention, and two more weeks of BWSTT + SCES. The participant presented with unstable resting seated blood pressure (BP; 131/66 mmHg). After retrospective analysis, resting systolic BP decreased and diastolic BP increased, yielding a safe mean arterial BP. There was a fivefold increase in BWSTT bouts per session, and percentage of body weight support decreased to 69%. BWSTT + SCES safely and effectively regulated resting BP and mitigated symptoms of orthostatic intolerance. These effects were not maintained after 4 weeks without training.

Postprandial Hypotension and Spinal Cord Injury

Postprandial hypotension (PPH) is defined as a fall of ≥20 mmHg in systolic blood pressure (SBP) or a SBP of <90 mmHg after having been >100 mmHg before the meal within two hours after a meal. The prevalence of PPH among persons with spinal cord injury (SCI) is unknown. Ambulatory blood pressure measurement was performed in 158 persons with SCI, 109 men, median age was 59.1 years (min.:13.2; max.: 86.2). In total, 78 persons (49.4%) had PPH after 114 out of 449 meals (25.4%). The median change in SBP during PPH was −28 mmHg (min.: −87; max.: −15 mmHg) and 96% of the PPH episodes were asymptomatic. The occurrence of PPH was correlated to older age (p = 0.001), level of injury (p = 0.023), and complete SCI (p = 0.000), but not, gender or time since injury. Further studies are needed to elucidate if PPH contributes to the increased cardiovascular mortality in the SCI population.

Poor specificity of National Early Warning Score (NEWS) in spinal cord injuries (SCI) population: a retrospective cohort study

STUDY DESIGN

Retrospective chart audit.

OBJECTIVES

The National Early Warning Score (NEWS) is based on seven physiological parameters which can be altered in some individuals with spinal cord injuries (SCI). The aim was to start the development of adapted NEWS suitable for SCI population. The objective was to determine the SBP NEWS specificity based on neurological level of injury (NLI) and completeness of injury.

SETTING

Tertiary centre in the UK.

METHODS

Adult patients admitted for the first time to the National Spinal Injuries Centre between 1 January 2015 and 31 December 2016 were included if they were >6 months post injury. Data were extracted retrospectively including the last ten consecutive BP and heart rate readings before discharge. Data were analysed based on different AIS grades, completeness of injury and NLI.

RESULTS

One hundred and ninety one patients were admitted in 2015 and 2016 and 142 patients were included in the primary analysis. The mean SBP ranged between 92 and 151 mmHg. Patients with the NLI of T6 and above (≥T6) motor complete lesions had a significantly lower SBP than motor incomplete lesions. The specificity of the SBP NEWS was 35.3% in ≥T6 motor complete individuals versus 80.3% in ≥T6 motor incomplete individuals.

CONCLUSION

The baseline BP is significantly lower in the ≥T6 motor complete SCI individuals (>6 months post injury) resulting in a very low specificity of 35.3% to SBP NEWS, which could lead to mismatch between clinical deterioration and NEWS resulting in lack of timely clinical response.

Paced breathing and phrenic nerve responses evoked by epidural stimulation following complete high cervical spinal cord injury in rats

Spinal cord injury (SCI) at the level of cervical segments often results in life-threatening respiratory complications and requires long-term mechanical ventilator assistance. Thus restoring diaphragm activity and regaining voluntary control of breathing are the primary clinical goals for patients with respiratory dysfunction following cervical SCI. Epidural stimulation (EDS) is a promising strategy that has been explored extensively for nonrespiratory functions and to a limited extent within the respiratory system. The goal of the present study is to assess the potential for EDS at the location of the phrenic nucleus (C₃-C₅) innervating the diaphragm: the main inspiratory muscle following complete C₁ cervical transection. To avoid the suppressive effect of anesthesia, all experiments were performed in decerebrate, C₁ cervical transection, unanesthetized, nonparalyzed ( n = 13) and paralyzed ( n = 7) animals. Our results show that C₄ segment was the most responsive to EDS and required the lowest threshold of current intensity, affecting tracheal pressure and phrenic nerve responses. High-frequency (200-300 Hz) EDS applied over C₄ segment (C₄-EDS) was able to maintain breathing with normal end-tidal CO₂ level and raise blood pressure. In addition, 100-300 Hz of C₄-EDS showed time- and frequency-dependent changes (short-term facilitation) of evoked phrenic nerve responses that may serve as a target mechanism for pacing of phrenic motor circuits. The present work provides the first report of successful EDS at the level of phrenic nucleus in a complete SCI animal model and offers insight into the potential therapeutic application in patients with high cervical SCI. NEW & NOTEWORTHY The present work offers the first demonstration of successful life-supporting breathing paced by epidural stimulation (EDS) at the level of the phrenic nucleus, following a complete spinal cord injury in unanesthetized, decerebrate rats. Moreover, our experiments showed time- and frequency-dependent changes of evoked phrenic nerve activity during EDS that may serve as a target mechanism for pacing spinal phrenic motor networks.

Relationship between autonomic cardiovascular control and obstructive sleep apnoea in persons with spinal cord injury: a retrospective study

Study design

Retrospective study.

Objective

To determine if there is an association between obstructive sleep apnoea (OSA) and blood pressure (BP) pattern or heart rate variability (HRV) in people with spinal cord injury (SCI).

Setting

A state-based spinal cord service in Victoria, Australia.

Methods

We identified 42 subjects who had ambulatory BP monitoring (ABPM) within 6 months of a diagnostic sleep study at Austin Hospital between 2009 and 2014. Markers for autonomic function, including circadian BP pattern and HRV were extracted from the ABPM study database. Apnoea/hypopnoea index (AHI), arousals/hour and oxygen desaturation index were extracted from the sleep study database. Subjects with a nocturnal systolic BP dipping more than 10% of daytime value were defined as dippers, between 10 and 0% were non-dippers and those with a higher night than day systolic BP were reverse dippers. Severity of OSA is classified as non-OSA (AHI < 5), mild (AHI 5-15), moderate (AHI 15-30) and severe (AHI > 30).

Results

Subjects (n = 42) were predominantly male (85.7%), aged 44 ± 15.4 (mean ± SD), with a BMI of 24.4 ± 5.7 (mean ± SD) and mainly tetraplegic (92.9%). There was no difference in AHI, oxygen desaturation index or arousals/hour between dippers, non-dippers and reverse dippers. None of the HRV parameters differed between dippers, non-dippers and reverse dippers. No differences were found in 24 h, night-time, daytime or nocturnal dip in BP between subjects with non-OSA, mild, moderate and severe OSA.

Conclusion

We found no relationship between BP pattern or HRV and the severity of OSA in persons with SCI.

Use of ambulatory blood pressure monitoring in adolescents with SCI: a case series

Introduction

Due the impact of maturation on cardiovascular hemodynamics the degree of cardiovascular dysfunction, attributable to spinal cord injury (SCI), in the pediatric and adolescent population remains unclear. While few studies have begun to assess this, there is still a void in the literature regarding the prevalence of cardiovascular dysfunction and how best to identify and treat it in this population.

Case presentation

The purpose of this case series is to present the cardiovascular profile of three adolescent patients with chronic SCI, ages 14-16, following 2 or 3 days of 24-h Ambulatory Blood Pressure Monitoring (ABPM).

Discussion

We found that there are variations across the different cases in most cardiovascular hemodynamic categories and a clarification of the International Standards to document remaining Autonomic Function after Spinal Cord Injury (ISAFSCI) may be needed to accurately identify the remaining autonomic cardiovascular function in the adolescent SCI population.

Inter-day reliability of blood pressure and cerebral blood flow velocities in persons with spinal cord injury and intact controls

BACKGROUND

Due to interruption of cardiovascular autonomic control unstable blood pressure (BP) is common in individuals with spinal cord injury (SCI) above the sixth thoracic vertebral level. The impact of unstable BP on cerebral blood flow (CBF) is not well appreciated, but symptoms associated with altered cerebral perfusion are reported, which can negatively impact daily life activities.

METHODS

We measured seated BP and CBF in participants with SCI and able-bodied (AB) controls on three laboratory visits to determine the inter-day reliability (intraclass correlation coefficient: ICC). BP was assessed at the finger using photoplethysmography and at the brachial artery with manual sphygmomanometry. CBF velocities (CBFv) were assessed at the middle cerebral artery using transcranial Doppler (TCD) ultrasound.

RESULTS

Data were collected in 15 participants with chronic SCI (C3-T4) and 10 AB controls, the groups did not differ for age, height, weight or BMI; however, brachial BP (P < 0.001), finger BP (P < 0.01) and CBFv (P < 0.05) were significantly lower in the SCI group compared to the controls. The inter-day ICC for brachial BP ranged from 0.51 to 0.79, whereas the ICC for finger BP was not as high (0.17 to 0.47). The inter-day ICC for CBFv ranged from 0.45 to 0.96, indicating fair to substantial reliability.

CONCLUSIONS

These data indicate good inter-day reliability of brachial BP and TCD recording of CBFv; however, the assessment of finger BP appears to be somewhat less reliable. In addition, these data confirm reduced resting CBFv in association with hypotension in individuals with SCI compared to matched controls with low BP.

Ambulatory blood pressure monitoring in spinal cord injury: clinical practicability

Trauma to the spinal cord often results not only in sensorimotor but also autonomic impairments. The loss of autonomic control over the cardiovascular system can cause profound blood pressure (BP) derangements in subjects with spinal cord injury (SCI) and may therefore lead to increased cardiovascular disease (CVD) risk in this population. The use of ambulatory blood pressure monitoring (ABPM) allows insights into circadian BP profiles, which have been shown to be of good prognostic value for cardiovascular morbidity and mortality in able-bodied subjects. Past studies in SCI subjects using ABPM have shown that alterations in circadian BP patterns are dependent on the spinal lesion level. Tetraplegic subjects with sensorimotor complete lesions have a decreased daytime arterial BP, loss of the physiological nocturnal BP dip, and higher circadian BP variability, including potentially life-threatening hypertensive episodes known as autonomic dysreflexia (AD), compared with paraplegic and able-bodied subjects. The proposed underlying mechanisms of these adverse BP alterations mainly are attributed to a lost or decreased central drive to sympathetic spinal preganglionic neurons controlling the heart and blood vessels. In addition, several maladaptive anatomical changes within the spinal cord and the periphery, as well as the general decrease of physical daily activity in SCI subjects, account for adverse BP changes. ABPM enables the identification of adverse BP profiles and the associated increased risk for CVD in SCI subjects. Concurrently, it also might provide a useful clinical tool to monitor improvements of AD and lost nocturnal dip after appropriate treatments in the SCI population.

The prevalence of pulmonary embolism in chronically paralyzed subjects: a review of available evidence

STUDY DESIGN

Qualitative systematic review.

OBJECTIVES

To examine the validity of the prevailing notion that pulmonary embolism (PE) is rare in the chronic spinal cord injury (SCI) population.

SETTING

USA.

METHODS

Review surveys of adult SCI subjects >2 months after injury in which PE has been looked for and its prevalence estimated.

RESULTS

A total of 16 surveys of chronic SCI subjects published between 1956 and 2009 offered data on PE prevalence. Two autopsy surveys, 178 subjects paralyzed >2 months, revealed no PE. Eleven surveys of the cause of death, 3193 subjects paralyzed 1-25 years, revealed PE in 2.1%. Two surveys of survivors of SCI, 5761 subjects paralyzed 1-25 years, revealed PE in 0.4%. Our survey of 112 subjects paralyzed 1-50 years before death, revealed PE in 21 (18.7%), based on autopsy, imaging, clinical and electrocardiographic evidence. In 7 (33%) of the 21 subjects with PE, pulmonary hypertension by transthoracic echocardiography was detected, indicating recurrent and/or unresolved PE.

CONCLUSION

PE is not infrequent in the chronic SCI subject; but its presentation may be subclinical; and its apparent recurrence may lead to pulmonary hypertension.