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Trial registered on ANZCTR


Registration number
ACTRN12614000103662
Ethics application status
Approved
Date submitted
26/11/2013
Date registered
28/01/2014
Date last updated
24/03/2017
Type of registration
Prospectively registered

Titles & IDs
Public title
Transthoracic echocardiographic assessment of cardiac output in healthy women at elective caesarean section under spinal anaesthesia with ephedrine hypotension prophylaxis: an observational cohort study
Scientific title
In healthy women having an elective caesarean what is the effect of the spinal anaesthetic on the mother's cardiac output when ephedrine is used to maintain blood pressure?
Secondary ID [1] 283572 0
Nil
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Cardiac output in healthy women having elective caesarean section under spinal anaesthesia 290474 0
Condition category
Condition code
Anaesthesiology 290866 290866 0 0
Anaesthetics
Reproductive Health and Childbirth 291183 291183 0 0
Childbirth and postnatal care

Intervention/exposure
Study type
Observational
Patient registry
False
Target follow-up duration
Target follow-up type
Description of intervention(s) / exposure
This is an observational study measuring the change in maternal cardiac output ten minutes after injection of spinal anaesthetic in the presence of intravenous ephedrine used to maintain systolic blood pressure within 90% of baseline.
The cardiac output will be measured by transthoracic echocardiography. The systolic blood pressure will be monitored until delivery of the baby.
Intervention code [1] 288263 0
Not applicable
Comparator / control treatment
Nil
Control group
Uncontrolled

Outcomes
Primary outcome [1] 290977 0
The range of values for cardiac output and stroke volume.

Heart rate (HR) will be measured from a standard 3-lead ECG continuous recording. Automated non-invasive blood pressure (NIBP) measurements will be taken at 1 minute intervals from the commencement of the ephedrine infusion with a cuff placed on the upper arm using the oscillometric method. One-minutely NIBP and HR readings will be retrieved post-operatively from the memory of the anaesthetic machine.

Transthoracic echocardiographic measurement of the cardiac output (CO) and stroke volume (SV) will be determined using the following method. In the parasternal long axis (PLAX) view, a good quality image of the left ventricular outflow tract (LVOT) will be obtained. This is defined as an image in which the aortic valve can be seen and the structure looks tubular. This image is zoomed and frozen during systole and then stored. The apical five chamber (A5C) view will then be used to ascertain the LVOT velocity time integral (VTI). A good quality image is one with maximal chamber size, a vertical long axis and maximal mitral valve opening size. Pulse wave Doppler will be used with a 3 mm sample volume placed within the LVOT approximately 0.5 cm proximal to the aortic valve. The angle of Doppler interrogation of flow will be less than 20 degrees. At least three consecutive beats will be recorded and the images stored. Following the completion of the scans the images will be used to calculate the cardiac output.
In regard to LVOT diameter the PLAX image will allow the measurement of the LVOT diameter (in cm) perpendicularly to the aortic root from the junction of the anterior coronary cusp and the interventricular septum to the junction of the posterior non-coronary aortic cusp and the anterior mitral valve leaflet.
The VTI shall be measured by tracing the leading edge of the velocity spectrum of three consecutive beats. The VTI used to calculate CO will be the average of these three beats. Heart rate will be measured from the Doppler spectral display from the time between two consecutive beats in the VTI tracing.
For calculation of SV and CO:
a) SV (ml) = [(LVOT diameter)^2 x 0.785](cm^2) x VTI(cm). (where [(LVOT)^2 x 0.785 = p x LVOT radius^2 = cross sectional area of the LVOT)
b) CO (ml/min) = heart rate(beats/min) x [(LVOT diameter)^2 x 0.785](cm^2) x VTI(cm).
Timepoint [1] 290977 0
Immediately pre-spinal and 10 minutes post spinal injection.
Primary outcome [2] 290978 0
The change in cardiac output and stroke volume.

A change is measured by using change score ANOVA.
Timepoint [2] 290978 0
Immediately pre-spinal and 10 minutes post-spinal injection.
Primary outcome [3] 291220 0
The relationship between cardiac output, stroke volume, heart rate and blood pressure.

This will be assessed graphically.
Timepoint [3] 291220 0
Immediately pre-spinal and 10 minutes post-spinal injection.
Secondary outcome [1] 305727 0
The amount of ephedrine required to maintain systolic blood pressure to 90% of the baseline reading for each patient.

This will be calculated as the sum of the total infusion dose delivered and the total number of boluses delivered; the values will be obtained directly from the infusion pump memory and documented directly on the participant study data sheet . Analysis will be descriptive; median [25th-75th percentile].
Timepoint [1] 305727 0
This will be for the period from commencement of the ephedrine infusion to time of birth of the baby.
Secondary outcome [2] 305728 0
The number of women requiring treatment for bradycardia of heart rate less than 50 beats per minute with associated hypotension of systolic blood pressure less than 90 mmHg.

This will be monitored and documented directly on the participant study data sheet and presented as number and percentage.
Timepoint [2] 305728 0
Monitored and documented for the interval from commencement of ephedrine infusion to birth of the baby.
Secondary outcome [3] 305729 0
Maternal side-effects – nausea and vomiting; shivering; dizziness; headache, any others as noted and will be documented directly on the participant study data sheet. All will be recorded by a study investigator as either absent or present.

This will be analysed as median [25th -75th percentile]
Timepoint [3] 305729 0
Monitored continously and documented for the interval from commencement of ephedrine infusion to birth of the baby.
Secondary outcome [4] 305730 0
Neonatal APGAR scores at 1 and 5 minutes.

This will be assessed as median[25th-75th percentile].
Timepoint [4] 305730 0
At 1 and 5 minutes after the birth of the baby.
Secondary outcome [5] 306181 0
Arterial and venous umbilical cord pH will be measured with automated blood gas analyser and documented directly on the participant study data sheet.

This will be assessed as median[25th-75th percentile].
Timepoint [5] 306181 0
Measured and documented at the birth of the baby.

Eligibility
Key inclusion criteria
Elective caesarean section
American Society of Anesthesiologists (ASA) physical status grade I or II,
Gestation greater than 37 weeks
Singleton pregnancy
Non-smoker
Minimum age
18 Years
Maximum age
40 Years
Sex
Females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Insulin dependent diabetes mellitus
Use of vasoactive medication including salbutamol, beta-blockers and thyroxine
In labour
BMI greater than 35.0

Study design
Purpose
Screening
Duration
Cross-sectional
Selection
Defined population
Timing
Prospective
Statistical methods / analysis
Demographic data will be presented as mean (SD), median [25th – 75th percentile] and number (%) according to type and distribution. Summary measures for primary (HR, LVOT, VTI) and derived (SV and CO) outcome measurements will be presented for both measurement times along with change scores for the two derived measures. These will include 95% confidence intervals for HR, CO, CI and SV.
Assessment of compliance with mean arterial pressure control (MAP) will be performed: (i) across all 10+ blood pressure measurements using proportion within target interval (90 – 110% of baseline) and (ii) for the T9-T11 (one minute each side of the T10 measurement) using a dichotomous marker equals to 1 if all three readings lie within the target interval.
Assessment of the relationship between HR, SV and CO will be explored graphically.
Assessment of change in CO will be made using change score ANOVA if change scores are approximately normally distributed or following transformation to normality if not. A Wilcoxon sign rank test on change scores may also be used.
Sample size calculation is based upon within patient change in cardiac output, at a detectable difference of 600 ml, mean baseline CO 4400 ml, two-sided significance level 0.05 and power 0.8. There is no data available to estimate SD for the within patient change score. We used the SD (1000 ml) found on the baseline CO data of 28 patients in previously published work.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
31/01/2014
Actual
31/01/2014
Date of last participant enrolment
Anticipated
Actual
30/01/2015
Date of last data collection
Anticipated
Actual
30/01/2015
Sample size
Target
30
Accrual to date
Final
28
Recruitment in Australia
Recruitment state(s)
VIC
Recruitment hospital [1] 1766 0
Mercy Hospital for Women - Heidelberg
Recruitment postcode(s) [1] 7583 0
3084 - Heidelberg

Funding & Sponsors
Funding source category [1] 288333 0
Hospital
Name [1] 288333 0
Mercy Hospital for Women
Country [1] 288333 0
Australia
Primary sponsor type
Individual
Name
Scott Simmons
Address
Mercy Hospital for Women
163 Studley Road
Heidelberg
VIC 3084
Country
Australia
Secondary sponsor category [1] 287049 0
None
Name [1] 287049 0
Address [1] 287049 0
Country [1] 287049 0
Other collaborator category [1] 277712 0
Individual
Name [1] 277712 0
Richard Hiscock
Address [1] 277712 0
Mercy Hospital for Women
163 Studley Road
Heidelberg
VIC 3084
Country [1] 277712 0
Australia
Other collaborator category [2] 277713 0
Individual
Name [2] 277713 0
Sajidah Ilyas
Address [2] 277713 0
Mercy Hospital for Women
163 Studley Road
Heidelberg
VIC 3084
Country [2] 277713 0
Australia
Other collaborator category [3] 277714 0
Individual
Name [3] 277714 0
Eoin Casey
Address [3] 277714 0
Mercy Hospital for Women
163 Studley Road
Heidelberg
VIC 3084
Country [3] 277714 0
Australia

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 290226 0
Mercy Health Human Research Ethics Committee
Ethics committee address [1] 290226 0
Mercy Hospital for Women
163 Studley Road
Heidelberg, VIC 3084
Ethics committee country [1] 290226 0
Australia
Date submitted for ethics approval [1] 290226 0
24/10/2013
Approval date [1] 290226 0
03/12/2013
Ethics approval number [1] 290226 0
R13-51

Summary
Brief summary
One of the most common types of anaesthetic used for caesarean section is a spinal anaesthetic. In order for women to be comfortable during the operation a large number of nerves are blocked. In addition to the pain nerves it is very common for other nerves to be affected, including those which are responsible for other types of sensation, movement in the legs and also those which normally help control blood pressure. Significantly low blood pressure in the mother may be associated with side-effects including nausea and vomiting, dizziness and possibly loss of consciousness and in extreme situations the baby may also receive a reduced blood supply from the placenta. For the anaesthetist to provide a safe anaesthetic it is very important to monitor these effects and especially any changes to blood pressure and how the woman’s body responds to it. This is particularly important during the first 5 to 10 minutes after the injection of the spinal anaesthetic. During this period it is usual to closely measure blood pressure, heart rate, the amount of oxygen in the blood and the electrical activity of the heart from an electrocardiogram.
Recently, it has also become possible to directly observe the function of the heart relatively quickly and easily via a hand-held ultrasound probe placed on the chest – a transthoracic echocardiogram or TTE. These devices are very similar to those used for obtaining images of the baby during pregnancy. It is known from the use of these devices in other situations, including in pregnant women, that valuable information may be obtained about how the heart is performing. Until now this has not been done in healthy women having a spinal anaesthetic for an elective caesarean section. Hence, the purpose of our study is to document the effects of a standard spinal anaesthetic on the output of the heart by comparing measurements at approximately 10 minutes after the spinal injection with measurements taken immediately before the spinal using TTE. In keeping with usual practice, drugs will be given to help maintain normal blood pressure throughout.
Information obtained from this study will be helpful in further understanding the impact of spinal anaesthetics on the cardiovascular system in pregnant women which is likely to help guide anaesthetists to reduce side effects and improve safety.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 44218 0
A/Prof Scott Simmons
Address 44218 0
Mercy Hospital for Women
163 Studley Road
Heidelberg
VIC 3084
Country 44218 0
Australia
Phone 44218 0
+61 3 8458 4113
Fax 44218 0
Email 44218 0
[email protected]
Contact person for public queries
Name 44219 0
Scott Simmons
Address 44219 0
Mercy Hospital for Women
163 Studley Road
Heidelberg
VIC 3084
Country 44219 0
Australia
Phone 44219 0
+61 3 8458 4113
Fax 44219 0
Email 44219 0
[email protected]
Contact person for scientific queries
Name 44220 0
Scott Simmons
Address 44220 0
Mercy Hospital for Women
Studley Road
Heidelberg
VIC 3084
Country 44220 0
Australia
Phone 44220 0
+61 3 8458 4113
Fax 44220 0
Email 44220 0
[email protected]

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