Clinical trial NCT04330742: The Effect of Fluids on Aortic VTI During C-section
Official title: The Influence of Intravascular Fluid Administration on Aortic Velocity Time Integral in Obstetric Patients Undergoing Cesarean Section
Study type: OBSERVATIONAL
Overall status: RECRUITING
Conditions: Pregnancy Related
Hemorrhage
Fluid Overload
Labor Complication
Keywords: obstetrics
fluid responsiveness
fluid resuscitation
Lead sponsor: Baylor College of Medicine
Sponsor class: OTHER
First posted: 2020-04-01
Enrollment: 50
Sex: FEMALE
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Observational model: COHORT
Time perspective: PROSPECTIVE
Sampling method: PROBABILITY_SAMPLE
Study population: All patients ages 18-35 undergoing elective cesarean section with planned spinal anesthetic at Ben Taub General Hospital (BTGH) will be screened. Consenting patients will undergo spinal anesthetic prior to planned procedure. All subjects will receive the same 1L fluid bolus intraoperatively.

Brief summary: Pregnancy is associated with a myriad of physiologic changes, including expansion of blood volume, decrease in oncotic pressure, and increased cardiac output. The obstetric population is associated with intrapartum hemorrhage. Accordingly, it is important to have an accurate method to assess fluid status in intrapartum patients. The use of standard volume assessment tools including arterial lines and central venous catheters is limited given the brevity of obstetric procedures and the morbidity of these techniques on the awake patients, and the costs. Non-invasive methods to assess volume status (carotid dopplers, direct measurement of blood loss, bio-impedance devices) are imperfect. Echocardiography is an attractive tool to measure fluid status in experienced operators such as anesthesiologists. IVC diameter and variation of aortic velocity time integral are two measures that can be obtained via echocardiography and been studied in spontaneously breathing patients. The purpose of this study is to determine whether these measurements can be used in the assessment of volume status in the laboring patient.

Detailed description: Pregnancy is associated with a myriad of physiologic changes, including expansion of blood volume, decrease in oncotic pressure, and increased cardiac output. Comorbidities including maternal hypertension, renal or cardiac disease may further complicate the assessment of volume status and are associated with increased risks related to fluid administration (c). In addition, the majority of obstetric patients receive neuraxial analgesia or anesthesia to facilitate both vaginal and operative delivery. These techniques are associated with hemodynamic changes including maternal hypotension secondary to a decrease in SVR and CO. These changes may in turn be associated with a reduction in placental blood flow affecting fetal outcome, and may also cause maternal nausea, vomiting and dizziness. Further, the obstetric population is high risk for intrapartum hemorrhage. As such, it is critical to have an accurate method to assess fluid status in intrapartum patients.

The use of invasive volume assessment tools including arterial lines and central venous catheters is limited given the brevity of obstetric procedures, the morbidity of these invasive techniques for the awake patient, and the associated time and costs (b). Non-invasive methods that assess volume status in the obstetric population include techniques such as direct measurement of blood loss (g), carotid dopplers (c), bio-impedence devices (f); However these methods have been shown to be imperfect and are not widely used.

Echocardiography is a non-invasive, widely-available tool that can provide rapid information for experienced operators such as anesthesiologists. Respiratory variations in inferior vena cava diameter (IVCd) and variation in aortic velocity time integral (∆VTI) following passive leg raise have been extensively studied in spontaneously breathing patients. IVCd has been shown to predict fluid responsiveness, however requires a high threshold (\>40-50% collapsibility) to detect a difference. IVCd may also change with diaphragmatic motion, thus results may be confounded if the patient becomes tachypneic (d) or is spontaneously breathing (g). In contrast, aortic velocity time integral (∆VTI) may be a more sensitive indicator of volume status. Lamia et al showed a 12% change in VTI as 77% sensitive and 100% specific for a 15% change in cardiac output following 500 mL volume expansion in ICU patients with shock (both spontaneously breathing and mechanically ventilated, e). While there are some studies of IVC collapsibility in the obstetric population, there are limited data on VTI as a measure of volume status in laboring patients.

The purpose of this study is to determine whether the aortic velocity time integral (VTI) is influenced by intravascular fluid administration during cesarean section. Secondary aims include determining whether inferior vena cava diameter (IVCd), blood pressure, and heart rate are influenced by intravascular fluid administration during cesarean section. Additionally, total amount of vasopressor agents administered during the procedure will be recorded.

Eligibility criteria: Inclusion Criteria:

* healthy nulliparous or multiparous pregnant women with a term (\>37 weeks gestation)
* age 18-35
* singleton pregnancy
* scheduled for Cesarean delivery with planned neuraxial spinal or combined spinal epidural anesthesia
* American Society for Anesthesiologists physical status 2

Exclusion Criteria:

* Patients without ability to provide informed consent
* American Society for Anesthesiologists physical status 3 or 4
* Emergency cesarean section
* BMI\>40
* Known cardiac and pulmonary comorbidities including chronic hypertension, preeclampsia, gestational hypertension, diabetes, asthma, renal disease
* Age \> 35

Primary outcomes:
measure: aortic velocity time integral
timeFrame: at baseline measure, right after spinal placement (250mL LR), at 500mL LR infusion, and at 1 L LR infusion (approximately 20mins)
Secondary outcomes:
measure: inferior vena cava collapsibility
timeFrame: at baseline measure, right after spinal placement (250mL LR), at 500mL LR infusion, and at 1 L LR infusion (approximately 20mins)
measure: change in systolic blood pressure
timeFrame: every 2.5 mins for 20 mins (when 1L LR is administered) once the pt has a spinal placement
measure: change in heart rate
timeFrame: every 2.5 mins for 20 mins (when 1L LR is administered) once the pt has a spinal placement
Other outcomes:
Locations:
city: Houston
country: United States
facility: Ben Taub General Hospital
state: Texas
Study officials:
affiliation: Baylor College of Medicine
name: Amy Lee, MD
role: PRINCIPAL_INVESTIGATOR
affiliation: Baylor College of Medicine
name: Yi Deng, MD
role: STUDY_DIRECTOR
affiliation: Baylor College of Medicine
name: Claudia Wei, MD
role: PRINCIPAL_INVESTIGATOR
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