Effect of hypotensive challenge on systemic hemodynamics and cerebral blood flow in persons with tetraplegia

Handrakis, John P.; DeMeersman, Ronald E.; Rosado-Rivera, Dwindally; LaFountaine, Michael F.; Spungen, Ann M.; Bauman, William A.; Wecht, Jill M.

doi:10.1007/s10286-008-0496-6

Cited by 21 publications

(14 citation statements)

References 29 publications

(47 reference statements)

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“…It can be argued that persistent hypotension may chronically reduce cerebral blood flow (CBF) resulting in cognitive impairments in individuals with SCI, particularly those with tetraplegia. In addition to persistent hypotension, individuals with tetraplegia often manifest orthostatic hypotension (OH) during upright positioning [12,13,34,42,59,60], which may worsen cerebral hypoperfusion during seated activities of daily living. Episodic OH during seated cognitive testing superimposed on chronic hypotension in individuals with tetraplegia may result in severely diminished CBF during testing and poor task performance.…”

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confidence: 99%

Systemic and cerebral hemodynamics during cognitive testing

et al. 2011

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Section: Introductionmentioning

confidence: 99%

Systemic and cerebral hemodynamics during cognitive testing

et al. 2011

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“…10 Resting cerebral blood flow (CBF), however, has been shown to be similar at rest in SCI as compared with able-bodied (AB) individuals. 11,12 Although resting CBF may be preserved after SCI, cerebrovascular reserve (i.e., the ability of the cerebrovascular system to respond to acute increases in metabolic demand, mechanical or neural stimuli) may be affected, resulting in an insufficient CBF response. 13 Supporting this contention, elegant work by Harper and Glass 14 showed that progressive hypotension abolishes the capacity of the cerebrovasculature to dilate or constrict.…”

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confidence: 99%

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

Phillips

Warburton

Ainslie

et al. 2014

J Cereb Blood Flow Metab

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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 4T6 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 (alpha 1 -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; Po0.05); however, PCAv conductance was higher (0.56 ± 0.13 versus 0.39 ± 0.15 cm/second/mm Hg; Po0.05). Controls exhibited a 20% increase in PCAv during cognition; however, the response in SCI was completely absent (Po0.01). When BP was increased with midodrine, NVC was improved 70% in SCI, which was reflected by a 13% improved cognitive function (Po0.05). Improvements in BP were related to improved cognitive function in those with SCI (r 2 ¼ 0.52; Po0.05). Impaired NVC, secondary to low BP, may partially mediate reduced cognitive function in individuals with high-level SCI. INTRODUCTIONSpinal cord injury (SCI) is a devastating condition often resulting in disturbed motor, sensory, and autonomic function. As a result of disrupted descending autonomic spinal pathways after SCI, sympathetic vasomotor tone is impaired, often resulting in arterial hypotension. 1 Those with injury at or above T 6 spinal segment, because of a myriad of potential mechanisms (including decentralization of sympathetically mediated vasomotor tone in the splanchnic region and legs) have more profound autonomic disturbances including resting hypotension and orthostatic hypotension as compared with those with lower level SCI. 2 An abundance of evidence, from both animal and human studies, demonstrated that there is an association between low blood pressure (BP) and a variety of cognitive impairments. 3,4 There is well-established evidence that individuals with SCI have a high rate of traumatic brain injury that can result in a significant number of cognitive dysfunctions. 5 However, the high prevalence of cognitive dysfunction (i.e., between 10% and 60%) in SCI 6,7 is likely to be at least partially due to widespread hypotension. 8 This notion is further highlighted by a significant positive relationship between systolic BP (SBP) and cognitive function in the SCI population. 9

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“…Dynamic CA may have different control mechanisms than static CA (12), including more effective neural control of CBF (46). Studies have indicated that static CA is maintained with SCI [Tetra chronic lesion C4 -C7 (20,34,35)]. On the basis of a maintained CBF velocity during profound orthostatic stress, Gonzalez et al (18) interpreted this finding to indicate that static CA was actually improved after acute Para and Tetra SCI (C5-T6); however, since no comparison was made with noninjured control subjects [preinjury or an able-bodied (AB) control group], this interpretation should be treated with caution.…”

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Cerebrovascular reactivity and dynamic autoregulation in tetraplegia

Wilson

Cotter

Fan

et al. 2010

American Journal of Physiology-Regulatory, Integrative and Comp

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Humans with spinal cord injury have impaired cardiovascular function proportional to the level and completeness of the lesion. The effect on cerebrovascular function is unclear, especially for high-level lesions. The purpose of this study was to evaluate the integrity of dynamic cerebral autoregulation (CA) and the cerebrovascular reactivity in chronic tetraplegia (Tetra). After baseline, steady-state hypercapnia (5% CO(2)) and hypocapnia (controlled hyperventilation) were used to assess cerebrovascular reactivity in 6 men with Tetra (C5-C7 lesion) and 14 men without [able-bodied (AB)]. Middle cerebral artery blood flow velocity (MCAv), cerebral oxygenation, arterial blood pressure (BP), heart rate (HR), cardiac output (Q; model flow), partial pressure of end-tidal CO(2) (Pet(CO(2))), and plasma catecholamines were measured. Dynamic CA was assessed by transfer function analysis of spontaneous fluctuations in BP and MCAv. MCAv pulsatility index (MCAv PI) was calculated as (MCAv(systolic) - MCAv(diastolic))/MCAv(mean) and standardized by dividing by mean arterial pressure (MAP). Resting BP, total peripheral resistance, and catecholamines were lower in Tetra (P < 0.05), and standardized MCAv PI was approximately 36% higher in Tetra (P = 0.003). Resting MCAv, cerebral oxygenation, HR, and Pet(CO(2)) were similar between groups (P > 0.05). Although phase and transfer function gain relationships in dynamic CA were maintained with Tetra (P > 0.05), coherence in the very low-frequency range (0.02-0.07 Hz) was approximately 21% lower in Tetra (P = 0.006). Full (hypo- and hypercapnic) cerebrovascular reactivity to CO(2) was unchanged with Tetra (P > 0.05). During hypercapnia, standardized MCAv PI reactivity was enhanced by approximately 78% in Tetra (P = 0.016). Despite impaired cardiovascular function, chronic Tetra involves subtle changes in dynamic CA and cerebrovascular reactivity to CO(2). Changes are evident in coherence at baseline and MCAv PI during baseline and hypercapnic states in chronic Tetra, which may be indicative of cerebrovascular adaptation.

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Effect of hypotensive challenge on systemic hemodynamics and cerebral blood flow in persons with tetraplegia

Abstract: Despite impaired sympathetic vasomotor and BP control, CBF in persons with tetraplegia was comparable to that of control subjects during a hypotensive challenge.

Cited by 21 publications

References 29 publications

Systemic and cerebral hemodynamics during cognitive testing

Systemic and cerebral hemodynamics during cognitive testing

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

Cerebrovascular reactivity and dynamic autoregulation in tetraplegia

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