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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
An observational study comparing protocol estimated values to the measured values of mean arterial basal blood pressure
Scientific title
An observational study to assess the agreement between protocol estimated values and directly measured values for the basal blood pressure in a cohort of patients who recently underwent direct measurements of their resting arterial blood pressure.
Secondary ID [1] 283720 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Patients who recently underwent ambulatory nighttime blood pressure monitoring 290685 0
Condition category
Condition code
Cardiovascular 291051 291051 0 0

Study type
Patient registry
Target follow-up duration
Target follow-up type
Description of intervention(s) / exposure
This is a retrospective observational cohort study among patients who attended our hospital cardiology department. We will enrol only those patients who recently underwent nighttime ambulatory blood pressure (BP) monitoring (within the last 2 years). These BP measurements will be considered as direct measurements of basal arterial BP.

For all enrolled patients, a blinded study investigator who is not aware of the direct measurements, will then estimate the basal mean arterial BP according to a preset protocol, which is displayed in public notes section.

Both values, directly measured and protocol-estimated, will be then correlated for each participant.
Intervention code [1] 288413 0
Not applicable
Comparator / control treatment
We will enrol only those patients who recently underwent nighttime ambulatory blood pressure monitoring (within the last 2 years). These BP readings will be considered as direct measurements of basal arterial BP. Patient list will be extracted from the cardiology database, and the hospital electronic health information system will be accessed to obtain the required data. Where the patients do not have any digital medical records, we will contact patient’s local doctors to request previous BP measurements and anti-hypertensive treatment.
Control group

Primary outcome [1] 291041 0
Agreement between the summary measures of protocol-estimated basal arterial BP and directly-measured basal arterial BP
Timepoint [1] 291041 0
Direct measurement of nighttime or basal arterial BP during ambulatory BP monitoring within last two years
Secondary outcome [1] 305884 0
Correlation between protocol estimated basal arterial BP and directly measured basal arterial BP
Timepoint [1] 305884 0
Basal arterial BP would have been measured during nighttime ambulatory BP monitoring within the last two years

Key inclusion criteria
Patients with recent outpatient ambulatory BP monitoring within last 2 years AND 2 to 5 recorded BP measurements in a routine/follow up clinic BP within last three years

Minimum age
40 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Patients with end stage renal disease and/or receiving dialysis

Study design
Defined population
Statistical methods / analysis
R-square statistics will be used to quantify agreement between the summary measures of directly measured and protocol-estimated BP. The strength of the relationship will be reported using linear regression (assuming normality). The Bland-Altman plot will then be used to demonstrate that there was no bias in the relationship. Finally, we will incorporate covariates such as alteration in antihypertensive prescription and lability of BP.

As there is no prior data on this subject, the sample size calculation is convenience-based. We intend to enrol 100-200 patients with ambulatory BP monitoring. We believe the agreement data on this range of sample size will be a reasonable representation of the broader population. We will endeavour to collect maximum number of patients within this range if possible, as a larger sample size will provide a more precise estimate.

Recruitment status
Not yet recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 1806 0
John Hunter Hospital Royal Newcastle Centre - New Lambton
Recruitment postcode(s) [1] 7624 0
2305 - New Lambton

Funding & Sponsors
Funding source category [1] 288395 0
Name [1] 288395 0
John Hunter Hospital
Address [1] 288395 0
ICU, 64 Lookout Road, John Hunter Hospital,
New Lambton, NSW 2305
Country [1] 288395 0
Primary sponsor type
John Hunter Hospital
ICU, 64 Lookout Road, John Hunter Hospital,
New Lambton, NSW 2305
Secondary sponsor category [1] 287098 0
Name [1] 287098 0
Address [1] 287098 0
Country [1] 287098 0

Ethics approval
Ethics application status
Ethics committee name [1] 290281 0
Hunter New England Human Research Ethics Committee
Ethics committee address [1] 290281 0
Locked Bag 1
New Lambton, NSW 2305
Ethics committee country [1] 290281 0
Date submitted for ethics approval [1] 290281 0
Approval date [1] 290281 0
Ethics approval number [1] 290281 0

Brief summary
Few patients admitted to the intensive care unit (ICU) have a previous record of directly measured BP during nighttime or resting (hereto referred as basal) state. Therefore, the usual hemodynamic targets in ICU are broadly based on values relevant to the general population. Individualising these targets could vastly improve management of critically ill patients. A validated protocol to estimate a patient’s baseline BP would enable this tailored therapy for the patients.

The main purpose of this study is to assess the agreement (or the difference) between a protocol-estimated value and a directly measured value for the resting BP in a cohort of patients who recently underwent direct measurements of their resting arterial BP.

In this study, we hypothesise that the directly measured and protocol-estimated BP values will correlate well with minimal bias.
Trial website
Trial related presentations / publications
Public notes
Data will be collected on age, gender, previous clinic arterial BP, measured arterial BP and any major co-morbidities. All information collected for the study will be rendered unidentifiable before data is exported for further analysis. Participants’ data will be recorded directly in an Excel spread sheet and identified only by patient initials and the assigned study number.

The final study report will not contain any identifiable data of the participants. Where there is no record of previous BP measurements in the digital medical records, then a written/verbal request will be made to the patient’s local doctor. In case no previous BP measurements of a patient can be traced, then, since we cannot estimate basal BP for such a patient, he/she will be excluded from the study.

Participants: We anticipate enrolling approximately 100-200 patients for arterial BP assessment. This is a convenience-based sample size as there is no previous data in literature to determine appropriate sample size for such a study.

The preset protocol to estimate basal MAP is as follows:

Step 1: Find preferably up to five or at least two pre-morbid MAP (or BP) measurements, recorded at least 12 hours apart, starting with the most recent reading available within the last 3 years. The selected MAP (or BP) readings should be from a period when the patient met following criteria: was not admitted to ICU, was at least two weeks following any surgery, was not in renal failure, was not pregnant, was not receiving intravenous anti-hypertensive drugs, diuretics, or analgesics on that day, and was not transferred to another health care facility within the next two days.

1.1 Find pre-morbid MAP (or BP) measurements recorded during outpatient visits, pre-admission assessment or during a non-invasive cardiac investigation. If unavailable, then

1.2 Find pre-morbid MAP (or BP) recorded on the observation charts from the last 48 hrs of a previous hospitalization. If multiple BP readings are available during the night, record the median BP during the last night of previous hospital stay. Then, record BP measurements that were done closest to the 12-hour interval from the selected median BP reading.

Step 2: Derive pre-morbid basal MAP as follows:

2.1 Convert BP readings that are recorded in SBP/DBP format to MAP as per the equation: MAP = DBP + 1/3(SBP-DBP)

2.2 Subtract 15% from the daytime MAP values to estimate nighttime (basal) MAP to account for the nighttime fall in BP in accordance with published data on 24h ambulatory BP in previous studies.

2.3 Consider the mean of these estimated pre-morbid nighttime MAP values as basal-MAP.

Principal investigator
Name 39614 0
Dr Rakshit Panwar
Address 39614 0
ICU, 64 Lookout Road, John Hunter Hospital,
New Lambton, NSW 2305
Country 39614 0
Phone 39614 0
Fax 39614 0
Email 39614 0
Contact person for public queries
Name 39615 0
Dr Rakshit Panwar
Address 39615 0
ICU, 64 Lookout Road, John Hunter Hospital,
New Lambton, NSW 2305
Country 39615 0
Phone 39615 0
Fax 39615 0
Email 39615 0
Contact person for scientific queries
Name 39616 0
Dr Rakshit Panwar
Address 39616 0
ICU, 64 Lookout Road, John Hunter Hospital,
New Lambton, NSW 2305
Country 39616 0
Phone 39616 0
Fax 39616 0
Email 39616 0

No information has been provided regarding IPD availability
Summary results
No Results