Clinical trial
Sex Differences in Sympathetic Vascular Reactivity at High Altitude
Name
Pro00096808
Description
This study aims to investigate sex differences in blood pressure control associated with exposure to acute hypoxia (low oxygen), and short term acclimatization to hypoxia at high altitude.
Trial arms
Trial start
2022-07-28
Estimated PCD
2023-02-05
Trial end
2023-02-05
Status
Completed
Treatment
Sodium Nitroprusside
A bolus injection of sodium nitroprusside will be given to lower blood pressure and evaluate baroreflex function.
Arms:
High Altitude, Low Altitude
Phenylephrine Hydrochloride
A bolus injection of phenylephrine will be given to raise blood pressure and evaluate baroreflex function immediately following the sodium nitroprusside infusion.
Arms:
High Altitude, Low Altitude
Other names:
Neo-Synephrine
Phenylephrine Hydrochloride
Investigators will give three incremental doses via brachial artery catheter to observe α1-adrenoreceptor mediated vasoconstriction. This will occur three times throughout the protocol.
Arms:
High Altitude, Low Altitude
Norepinephrine
Investigators will give three incremental doses via brachial artery catheter to observe adrenoreceptor activation. This will occur three times throughout the protocol.
Arms:
High Altitude, Low Altitude
Isometric Handgrip and Post-Exercise Circulatory Occlusion
Participants will perform 2 minutes of isometric handgrip at 30% maximal voluntary contraction followed by 2 minutes of post-exercise circulatory occlusion to assess the reactivity of the blood vessels to exercise and the metaboreflex.
Arms:
High Altitude, Low Altitude
Rhythmic Handgrip
Participants will perform 3 minutes of rhythmic handgrip at 25% maximal voluntary contraction to assess the reactivity of blood vessels to dynamic exercise.
Arms:
High Altitude, Low Altitude
Cold Pressor Test
Standardized sympathetic stressor involving submersion of the hand in ice-cold water for 3-minutes, aiming to elicit endogenous neurotransmitter release and blood pressure increases.
Arms:
High Altitude, Low Altitude
Propranolol Hydrochloride
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Propranolol is a beta-adrenergic antagonist and will allow investigation of the role of beta receptors in responses to various stressors. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Arms:
High Altitude, Low Altitude
Phentolamine Mesylate
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Phentolamine is an alpha-adrenergic antagonist and will allow investigation the role of alpha receptors in responses to various stressors. It will be continuously infused with propranolol. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Arms:
High Altitude, Low Altitude
Size
17
Primary endpoint
Change in systolic, diastolic, and mean arterial blood pressure
3 minutes
Change in arterial blood flow
1 hour 30 minutes
Change in vascular conductance
20 minutes
Cold pressor test
3 minutes
Propranolol
2 hours
Phentolamine
1 hour
Eligibility criteria
Inclusion Criteria:
* Between ages of 18-50
* No medical history of cardiovascular, respiratory, nervous system, or metabolic disease
* Females must be pre-menopausal
Exclusion Criteria:
* Any known cardiovascular, respiratory, nervous system, or metabolic disease (however, participants with controlled arterial hypertension will not be excluded)
* Having travelled above 2,000m within 1 month of testing at low and high altitude
* Females who are pregnant, confirmed by a pregnancy test
* Females who are post-menopausal
* Participants that are classified as obese (body mass index \> 30kg⋅m²)
* Participants who are current daily smokers
* Those with a known allergy to sulfites
* Participants taking monoamine oxidase (MAO) inhibitors or tricyclic antidepressants or other medications that have contraindications with the study drugs
* Participants who are still within the washout period from participating in other studies involving drugs.
Protocol
{'studyType': 'INTERVENTIONAL', 'phases': ['NA'], 'designInfo': {'allocation': 'NON_RANDOMIZED', 'interventionModel': 'CROSSOVER', 'interventionModelDescription': 'Participants will partake in both arms of the study, which include: 1) low altitude and 2) high altitude assessments.', 'primaryPurpose': 'BASIC_SCIENCE', 'maskingInfo': {'masking': 'NONE', 'maskingDescription': 'Due to the study design, masking is not possible. The time points and dosages of the study drug will be known to the participant.'}}, 'enrollmentInfo': {'count': 17, 'type': 'ACTUAL'}}
Updated at
2023-03-23
1 organization
5 products
2 indications
Organization
University of AlbertaProduct
Sodium NitroprussideIndication
VasodilationIndication
VasoconstrictionProduct
PhenylephrineProduct
NorepinephrineProduct
PropranololProduct
Phentolamine