Characteristics of the Tsui Test and Pressure Waveform to Confirm Epidural Catheter Placement in Parturients With BMI ≥50 kg/m2

The prevalence of obesity has increased worldwide, and the anesthetic care of patients with obesity remains a challenge for providers despite advances. Obesity during pregnancy is a risk factor for hypertensive disorders, gestational diabetes, emergency cesarean section and higher prevalence of difficult airway. Neuraxial techniques should always be preferred in women with obesity, particularly in those with body mass index (BMI) ≥50 kg/m2, where complications can be magnified. It is estimated an overall epidural failure rate of 4.3% in patients with obesity and an epidural failure rate of 13.7% in those with BMI ≥50 kg/m2. Hence, a confirmatory test of epidural catheter placement should prove useful in this patient population. The epidural electrical stimulation test (EEST) and the epidural waveform analysis are tests described in the literature as confirmatory methods for accuracy of placement of the epidural catheter.

The Tsui test has been well studied in obstetric patients, including required threshold electric currents and muscle contraction patterns. However, these studies have been conducted in patients receiving lumbar epidural catheters. Furthermore, they have not specifically included women with obesity class 3, particularly those with BMI≥50 kg/m2. In a recent study conducted in our department, the investigators have observed that patients with BMI≥50 kg/m2 require placement of an epidural catheter at a low-thoracic or high lumbar interspace, to allow the provision of effective surgical anesthesia for cesarean delivery, which often requires a modified incision, either transverse supra-umbilical or infra-umbilical. There are only few studies with waveform confirmation in obstetric patients showing conflicting results and certainly no studies under the circumstances described above. Finally, the Tsui test and the epidural waveform analysis have never been compared in the obstetric population.

The investigators aim to describe the characteristics of the Tsui test and of the epidural waveform analysis in parturients with BMI≥50 kg/m2 receiving epidural catheter placement at T12-L1 for both labor analgesia or anesthesia for cesarean delivery

Study Overview

• Status: Completed
• Conditions: Labor Pain
• Intervention / Treatment: Device: Tsui test; Device: epidural waveform analysis

Detailed Description

The Tsui test has been well studied in obstetric patients, including required threshold electric currents and muscle contraction patterns. However, these studies have been conducted in patients receiving lumbar epidural catheters. Furthermore, they have not specifically included women with obesity class 3, particularly those with BMI≥50 kg/m2. In a recent study conducted in our department, the investigators have observed that patients with BMI≥50 kg/m2 require placement of an epidural catheter at a low-thoracic or high lumbar interspace, to allow the provision of effective surgical anesthesia for cesarean delivery, which often requires a modified incision, either transverse supra-umbilical or infra-umbilical. There are only few studies with waveform confirmation in obstetric patients showing conflicting results and certainly no studies under the circumstances described above. Finally, the Tsui test and the epidural waveform analysis have never been compared in the obstetric population.

• Study Type: Observational
• Enrollment (Actual): 20

Contacts and Locations

• Study Contact: Name: Jose Carvalho, MD; Phone Number: 26814 416-586-4800; Email: jose.carvalho@sinaihealth.ca

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5G1X5
      • Mount Sinai Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 55 years (Adult)
• Accepts Healthy Volunteers: N/A
• Genders Eligible for Study: Female

• Sampling Method: Non-Probability Sample

Study Population

Parturients with BMI≥50 kg/m2 requesting epidural labor analgesia or undergoing elective cesarean delivery.

Description

Inclusion Criteria:

- Parturients with BMI≥50 kg/m2 requesting epidural labor analgesia or undergoing elective cesarean delivery

Exclusion Criteria:

• contraindication to epidural anesthesia
• allergy or hypersensitivity to lidocaine, bupivacaine or fentanyl
• those with implanted electronic devices.

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Patients having an epidural placed for labour analgesia or anesthesia for cesarean delivery; Patients with BMI>=50 who are having an epidural placed may take part in this study.

Device: Tsui test; The stimulator is set at frequency of 1Hz with 0.2 msec pulse width and the current output ranging from 0 to 20 mA. The current output will be carefully increased from zero until motor activity is detected up to a maximum of 20 mA.; Other Names: epidural electrical stimulation test (EEST); Device: epidural waveform analysis; A pressurized 500ml normal saline bag will be connected to a pressure transducer kit and the transducer will be connected to a portable monitor with the scale set at 0-40 mmHg or to optimum scale. The transducer will be levelled with the heart approximated at the patient's manubrio-sternal angle, with the patient in the sitting position. Sterile tubing will be connected to the epidural needle and attached to transducer. The tubing connection will be filled with saline to ensure proper reflection of the pressure transducer tracing. Test will be considered positive in case of pulsatile waveform is observed in synchrony with heart rate.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Tsui test motor response: questionnaire	Tsui test motor response will be recorded as either: left, right or bilateral. Any increase in current requirement after the test dose will be recorded.	15 minutes
epidural waveform test (catheter) - questionnaire	A positive epidural waveform test through the catheter, defined as the presence of a pulsatile waveform observed in synchrony with heart rate: yes or no.	15 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
epidural waveform test (needle) - questionnaire	A positive epidural waveform test though the needle, defined as the presence of a pulsatile waveform observed in synchrony with heart rate: yes or no	15 minutes
Tsui test motor response (before test dose): questionnaire	Tsui test motor response will be recorded as either: left, right or bilateral.	15 minutes
Tsui test current threshold (baseline)	Minimal electrical current required to produce a muscular contraction (mA) at baseline.	15 minutes
Tsui test current threshold (after test dose)	Minimal electrical current required to produce a muscular contraction (mA) 5 minutes after the test dose.	15 minutes
Laterality of the Tsui test: questionnaire	Laterality of the Tsui test, recorded as: unilateral right or left, or bilateral	15 minutes
Location of muscle group response to Tsui test: questionnaire	Muscle group responding to the electrical stimulation: abdominal wall, thigh, lower leg, foot (left or right)	15 minutes
Need for catheter mobilization: questionnaire	The need for catheter mobilization, including replacement (at any time after it is placed) will be documented as yes or no. The reason will also be recorded.	15 minutes

Collaborators and Investigators

• Sponsor: Samuel Lunenfeld Research Institute, Mount Sinai Hospital

Study record dates

Study Major Dates

• Study Start (Actual): June 21, 2022
• Primary Completion (Actual): February 14, 2023
• Study Completion (Actual): February 14, 2023

Study Registration Dates

• First Submitted: April 29, 2022
• First Submitted That Met QC Criteria: April 29, 2022
• First Posted (Actual): May 4, 2022

Study Record Updates

• Last Update Posted (Estimate): February 23, 2023
• Last Update Submitted That Met QC Criteria: February 22, 2023
• Last Verified: February 1, 2023

More Information

Terms related to this study

• Keywords: cesarean section; epidural analgesia; epidural catheter; Tsui test; epidural waveform
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Labor Pain
• Other Study ID Numbers: 22-03

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No