In the proposed study, the investigators examine in older adults with Type 2 diabetes the impact of beginning insulin therapy on the orthostatic drop in blood pressure as well as the response of arterial blood pressure and Doppler measures of cerebral blood flow during upright tilt. The investigators hypothesize that in older adults with Type 2 diabetes, the cardiovascular effects of insulin would precipitate or worsen orthostatic intolerance not present at baseline.
Before and 2 weeks after the start of standard insulin therapy several tests will be done: * orthostatic hypotension will be tested for with 3 orthostatic maneuvers * vasovagal syncope will be tested with 2 tilt table tests, one augmented with 400ug of nitroglycerin * MCA velocity will be measured with a transcranial doppler * Heart Rate and Blood Pressure will be measured throughout the test with a Finometer and Power Lab on a beat to beat basis
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
DIAGNOSTIC
Masking
NONE
Initiation of insulin administration will be determined as part of standard of care by the subjects diabetologist in the VGH Diabetes Centre and not as part of participation in this study.
Study session will occur prior to initiation of insulin therapy.
Gerontology Research Lab, Dept. of Medicine, Vancouver Coastal Health Research Institute, VGH Research Pavilion, Room 186-828 West 10th Avenue
Vancouver, British Columbia, Canada
1. Presence or absence of orthostatic hypotension
defined as a drop in systolic blood pressure greater than 20 mmHg after 3 minutes upright standing
Time frame: 1 day
1. The nadir of middle cerebral artery (MCA) velocity
lowest middle cerebral artery flow velocity determined by transcranial Doppler
Time frame: 1 day
2. The presence or absence of a positive augmented tilt table test
The augmented tilt table test will occur after receiving 300 μg nitroglycerin (GTN), and is a recognized method of testing for risk of vasovagal syncope. The tilt table will be considered positive and aborted prior to the 20 minutes if the subjects have a syncopal spell or demonstrate presyncopal (lightheadedness) symptoms in association with a 30 mm Hg drop in systolic blood pressure.
Time frame: 1 day
3. The nadir of systolic blood pressure (SBP) and diastolic blood pressure (DBP) during tilt table test.
lowest systolic blood pressure and diastolic blood pressure during tilt table tests and when they occur.
Time frame: 1 day
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