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Chapter 9 ■ Blood Pressure Monitoring 61

compliance to reduce damping of pressure wave). A

three-way tap is incorporated in the tubing to allow the

system to be zeroed and blood samples taken.

3. Pressure transducer with cable to signal processor

4. Neonatal physiologic monitor (multiparameter monitoring system)

a. Minimum configuration should have the capability

of displaying systolic, diastolic, and mean pressures

and heart rate.

b. It should have provision for high and low alarm settings.

5. Mechanical infusion device (infusion pump) with

syringe and tubing to deliver heparinized saline (0.5 to

1 U heparin/mL of fluid) at 0.5 to 1 mL/h. Pressurized

IV bag should not be used.

6. Some disposable pressure-monitoring kits offer closedloop systems for sampling (Fig. 9.5)

a. The system employs a mechanism for aspirating and

holding a fixed amount of blood in the pressure tubing rather than in a syringe.

b. The distal end is equipped with a small chamber

with a rubber septum that allows a self-guiding short

blunt syringe adapter to penetrate and aspirate blood

for the sample.

c. The initial volume pulled back is sufficient to

ensure that the blood drawn into the sample chamber is greater than the catheter/distal tubing volume

and is not diluted by the fluid being infused. The

absence of stopcocks at the distal end eliminates a

possible site for contamination. In addition, the

blood pulled back is conserved, and the amount of

fluid used to flush the sample line is reduced.

G. Technique

For catheter placement, see Part 5 of the book, “Vascular

Access”

1. Familiarize yourself with the bedside monitor and the

pressure zero/calibration procedure. To maintain

accuracy the pressure transducer is exposed to atmospheric pressure to calibrate the reading to zero. This

is done in several ways depending on the particular

transducer.

2. If using discrete components, assemble the pressuremonitoring circuit, maintaining the sterile integrity.

a. A basic circuit configuration will consist of a transducer dome, flush device, stopcock, pressure tubing, and an optional arterial extension set (short

length of pressure tubing, <12 inches in length,

inserted between the catheter and the pressure

tubing).

b. Ensure that all the Luer-lock connections are tight

and free of any defects.

c. If possible, avoid the use of IV tubing components

in the pressure-monitoring circuit.

3. Set up the infusion pump that will be used for the continuous infusion through the flush device. Continuous

flush devices limit flow rates to 3 or 30 mL/h, depending on the model (19–21). For neonatal arterial lines,

the infusion pump supplying the flush device should

be set to 0.5 to 3 mL/h and should never exceed the

flow rating of the flush device. When pump flow

exceeds the flush device rating, it will cause an occlusion alarm in most IV pumps. A pump flow rate of

1 mL/h is recommended for most arterial lines.

4. For circuit priming, use the solution that will be used

for the continuous infusion. Prime the circuit slowly to

avoid trapping air bubbles in the flush device inlet.

1

4

3

2

Fig. 9.4. Representative disposable BP transducer setup. (1)

Pressure transducer; (2) integral continuous flush device; (3) infusion port (connects to infusion pump); (4) high-pressure tubing.

Fig. 9.5. Disposable blood pressure transducer setup with

closed loop system for sampling. A: Umbilical arterial catheter.

B: Stopcock with special valve to draw blood samples. C: High

pressure tubing. D: Stopcock attached to heparinized saline flush

syringe. E: Stopcock for zeroing transducer. F: Pressure transducer. G: Transducer cable. H: Tubing with continuous heparinized saline infusion from infusion pump.