Ninvasive Cardiac Output Measurements During Cesarean Delivery Under Spinal Anesthesia.

Most women who undergo elective cesarean delivery in our hospital have spinal anesthesia for
the surgery. You will receive standard spinal anesthesia techniques whether or not you take
part in this study. You will be asked to sign a separate clinical consent form for the spinal
anesthesia and for your cesarean delivery.

After the anesthesiologist places your spinal anesthesia, the investigator will record your
blood pressure every two minutes as is the standard practice in our institution. An
anesthesiologist is a doctor who specializes in giving drugs or other agents to prevent or
relieve pain during surgery or other procedures. The investigator will also continuously
record your heart rate and the amount of oxygen in your blood as is the standard practice. If
needed, the anesthesiologist will give you medications to maintain your blood pressure.

In addition to the standard procedures described above, additional monitoring (checking) of
your heart will be performed as part of this study. The investigator will use the ICON
monitor to measure the amount of blood pumped by each heart beat.

The anesthesiologist will put on the sensors (sticky pads). There are four sticky pads that
are similar to what is used during electrocardiograms (EKGs). Two sensors are placed on the
left side of your neck and two on the left side of your trunk. The sensors have wires
attached that will be plugged into a small heart monitor device that records the information.

The investigators will place the sensors on you before you receive the spinal anesthesia. The
sensors will record what your heart is doing before placement of spinal anesthesia until the
end of your surgery.

The investigators will assign you by chance (like a coin toss) to one of the following
groups:

- Group Study: Your anesthesiologist will have access to the amount of blood that is
pumped during each heart beat. The anesthesiologist will treat and maintain the amount
of blood pumped during each beat so that it is within the normal range.

- Group Control: Your anesthesiologist will NOT have access to the amount of blood that is
pumped during each heart beat. The anesthesiologist will treat and maintain your blood
pressure throughout your delivery. (This is the current routine care.)

The control group and the study group will receive spinal anesthesia as is adapted in our
institution. HR and BP will be measured every two minutes as is normal practice. Cardiac
output will be measured in all patients in both groups. The subjects will have four surface
ECG electrodes attached to the left side of the neck and the lower thorax (at the level of
the xiphoid). Baseline hemodynamic parameters (SV (stroke volume), HR (heart rate), CO
(cardiac output) , SVV (stroke volume variation), and SVR (systemic vascular resistance))
will be determined before placing spinal anesthesia. Continuous CO data will be recorded by
the unit.

In the study group, phenylephrine and ephedrine will be used depending on the blood pressure
and cardiac output data. If the CO is normal, and BP is below 20% of baseline, phenylephrine
boluses of 40 micrograms at two minute interval (BP recording time) will be used to maintain
BP within 20% of the baseline. If the BP is normal, but CO is lower than 20% baseline,
ephedrine boluses (10 mg) will be used. If BP and CO is lower, a combination of both
phenylephrine and ephedrine will be used.

In the control group, the phenylephrine and ephedrine will be used as considered appropriate
to maintain BP within 20% of baseline. The CO data will be blinded to the anesthesiologists
in the control group

Study group (algorithm in detail):

1. If SBP<20%, CO is within (<,± ) 20% of baseline: Phenylephrine 40 mic boluses to bring
BP within 20% of the baseline.

2. If CO < 20%, and BP is within (<,± ) 20% of baseline, ephedrine boluses to bring the CO.

3. If both are below 20% of baseline, phenylephrine 40 mic boluses and ephedrine 10 mg
together will be used at 2 min intervals until both reach to within 20% of baseline.

4. If SBP is normal, and CO is greater than 20% baseline, no treatment needed.

5. If CO is normal, and SBP is greater than 20%, no treatment needed.

Control group:

Although BP and CO are being measured in the control group, CO data is blinded to the
clinician. Therefore the clinician will use SPB data and current practice instincts to choose
either of vasopressors considered appropriate to treat hypotension.

The anesthesiologist has his or her discretion of treating BP, or CO if these parameters are
not corrected with above protocol.

Fluid inputs and outputs will be noted that includes blood loss. Apgar scores of newborns
will be obtained from neonatologists' assessment. Incidence of nausea and vomiting and
medications used will be also noted.

The regional techniques will follow the standards adopted by our institution. Most placements
are done in the sitting position. After disinfecting the skin with betadine in the usual
fashion, the patients back will be draped with a sterile clear plastic and local anesthetic
(1.5 % lidocaine, 2ml) injected at the site of placement. A 3 1/2 -inch 25-gauge Whittaker
needle will be inserted into the spinal space at either the L3-L4 or L4-L5. Once the clear
Cerebrospinal fluid (CSF) is obtained, spinal medication (1.6 - 1.8 ml of bupivacaine 0.75%
with hyperbaric dextrose, 10 µgm fentanyl, 200 µgm morphine). Most patients receive oxytocin
infusion titrated to uterine tone (3-5 units/hr) and ondansetron for prevention of
postoperative nausea and vomiting after delivery of the baby.

Inclusion Criteria:

- Healthy pregnant subjects

Exclusion Criteria:

- Other than healthy

- High blood pressure. Presumed excessive bleeding, medications for blood pressure