Can Augmentation Index (AIx) be Used to Predict Hypotension After Spinal Anesthesia?

This study has been completed.
Sponsor:
Collaborator:
Children's & Women's Health Centre of British Columbia
Information provided by (Responsible Party):
University of British Columbia
ClinicalTrials.gov Identifier:
NCT00884026
First received: April 3, 2009
Last updated: January 22, 2013
Last verified: January 2013
  Purpose

A fall in blood pressure (hypotension) occurs in one third of spinal anesthetics administered to pregnant patients undergoing cesarean delivery. However, predicting which patients will experience hypotension following spinal anesthesia has proven difficult. Pulse wave analysis is a repeatable and reproducible method for investigation of cardiovascular function. A device called a SphygmacorTM can be used to measure pulse. The pulse measurement is called the Augmentation Index (AIx). AIx has been useful in detecting risks associated with blood pressure changes after complex surgery in patients with heart and blood vessel disease. In this study the investigators wish to see if it is possible to predict if a subject will experience hypotension based on her AIx measurement preoperatively.


Condition Intervention
Hypotension
Cesarean Delivery
Device: AIx measurement with a Sphygmacor TM

Study Type: Interventional
Study Design: Allocation: Non-Randomized
Endpoint Classification: Safety Study
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, Investigator)
Primary Purpose: Prevention
Official Title: Pulse Wave Analysis and Augmentation Index Changes Associated With Neuraxial Anesthesia in the Parturient

Resource links provided by NLM:


Further study details as provided by University of British Columbia:

Primary Outcome Measures:
  • Occurrence of hypotension following spinal anesthesia. Defined as systolic BP > 20% from baseline. [ Time Frame: 1 week ] [ Designated as safety issue: Yes ]

Secondary Outcome Measures:
  • Augmentation Index as measured by the SphygmacorTM preoperatively; Bradycardia requiring pharmacological treatment; Ephedrine requirement; Phenylephrine requirement; Block Height; Nausea/vomiting [ Time Frame: 1 week ] [ Designated as safety issue: Yes ]

Enrollment: 56
Study Start Date: March 2009
Study Completion Date: March 2010
Primary Completion Date: March 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: 1
Subjects that experience hypotension after spinal anesthesia.
Device: AIx measurement with a Sphygmacor TM
All subjects will have their AIx measured prior to surgery. After 30 subjects are recruited, they will be split into 2 groups. Group 1 will be those subjects who developed hypotension, and Group 2 will be those subjects who did not develop hypotension. We will then look at the preoperative measured AIx to determine whether there is a baseline difference between the two groups. A threshold value of the AIx with the best sensitivity and specificity for prediction of hypotension will then be determined.
Active Comparator: 2
Subjects that do not experience hypotension after spinal anesthesia.
Device: AIx measurement with a Sphygmacor TM
The second part of the study will then use the threshold AIx value found from the subjects who developed hypotension from the first 30 subjects to prospectively predict hypotension after spinal anesthesia in another 60 subjects

Detailed Description:

At BC Women's Hospital (BCWH), anesthesiologists give spinal anesthesia for most elective cesarean deliveries. When the spinal medication is given, blood vessels expand in reaction to the spinal medication causing blood pressure to fall. If a patient experiences this common reaction, the anesthesiologist would administer some medications to restore blood pressure to normal. They do this to protect the blood supply to the placenta and to the baby.

It is not known why this happens in some people and not in others. The way blood circulates through the body can provide information about changes occurring in the body. Pulse measurements are a simple way of providing physicians with important clinical information about patient health.

A device called a SphygmacorTM can be used to measure a pulse. The pulse measurement is called the Augmentation Index (AIx). AIx has been useful in detecting risks associated with blood pressure changes after complex surgery in patients with heart and blood vessel disease. In our study we wish to see if AIx can predict a normal patient's risk of hypotension after spinal anesthesia. If a trend between AIx and the onset of hypotension after spinal anesthesia can be found, anesthesiologists can more effectively prevent and treat hypotension by being able to predict whether it will occur.

Consenting subjects will have their blood pressure and AIx measurement taken prior to surgery.

Surgery will commence as per usual practice at BCWH. If hypotension occurs after the spinal anesthesia, anesthesiologist will treat as per usual practice.

Following recruitment and data collection on the first 30 subjects we will review their anesthetic records to assess whether they became hypotensive or not (systolic BP > 20% from baseline). This will give us two groups. Group 1 will be those subjects who developed hypotension, and Group 2 will be those subjects who did not develop hypotension. We will then look at the preoperative measured AIx to determine whether there is a baseline difference between the two groups. A threshold value of the AIx with the best sensitivity and specificity for prediction of hypotension will then be determined.

The second part of the study will then use the threshold AIx value found from the subjects who developed hypotension from the first 30 subjects to prospectively predict hypotension after spinal anesthesia in another 60 subjects.

  Eligibility

Ages Eligible for Study:   19 Years to 45 Years
Genders Eligible for Study:   Female
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • All women undergoing elective or urgent cesarean delivery under spinal anesthesia
  • Singleton Pregnancy
  • Greater than 37 weeks gestation
  • Healthy subjects with ASA 1 & 2 classification of health
  • Potential subjects need to be able to read and understand English unless independent (non-partner) translator available

Exclusion Criteria:

  • ASA 3 or above
  • Emergency cesarean delivery for fetal heart rate abnormalities
  • Cesarean delivery under general, epidural, or combined spinal epidural anesthesia
  • Maternal age <19 years
  • Maternal infection
  • Mothers with vascular disease - including hypertension/pre-eclampsia
  • Mothers with Diabetes Mellitus
  • Polyhdramnios
  • Multiple Pregnancy
  • Height < 150cm or > 180cm
  • BMI > 40
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00884026

Locations
Canada, British Columbia
BC Women's Hospital Dept of Anesthesia
Vancouver, British Columbia, Canada
Sponsors and Collaborators
University of British Columbia
Children's & Women's Health Centre of British Columbia
Investigators
Principal Investigator: Vit Gunka, MD, FRCPC University of British Columbia
Study Director: James Shannon, FCARSCI MSc University of British Columbia
Study Director: Joanne Douglas, MD, FRCPC University of British Columbia
Study Director: Jessica Tyler, BSc University of British Columbia
  More Information

No publications provided

Responsible Party: University of British Columbia
ClinicalTrials.gov Identifier: NCT00884026     History of Changes
Other Study ID Numbers: H08-03019
Study First Received: April 3, 2009
Last Updated: January 22, 2013
Health Authority: Canada: Health Canada

Keywords provided by University of British Columbia:
Cesarean delivery
hypotension
Augmentation Index
Pulse Wave analysis
spinal anesthesia
Hypotension following spinal anesthesia for cesarean delivery

Additional relevant MeSH terms:
Hypotension
Vascular Diseases
Cardiovascular Diseases
Anesthetics
Central Nervous System Depressants
Physiological Effects of Drugs
Pharmacologic Actions
Central Nervous System Agents
Therapeutic Uses

ClinicalTrials.gov processed this record on August 28, 2014