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CHAPTER 7 Physiologic Monitoring
Catheter length (cm)
12
Total body length (cm)
58
Catheter length (cm)
22
Total body length (cm)
T8
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169
L5
L3
10
8
6
4
28
30 32 34 36 3840 42 44
FIGURE 7.3 Graph for distance of catheter insertion from umbilical ring for
low placement. (From Rosenfeld W, Biagtan J, Schaeffer H, et al. A new graph
for insertion of umbilical artery catheters. J Pediatr. 1980;96(4):735.)
Dunn
(bifurcation)
46 48 50 52 54 56
of extremely low-birth-weight (ELBW) infants.
Catheters used to cannulate the umbilical vein are
available as both single-lumen and double-lumen
items. Double-lumen catheters permit the simultaneous administration of infusates and medications.
Use of a UVC reduces the need for peripheral
devices when multilumen UVCs are used.
INTERVENTIONS
Invasive Monitoring
Placement of UACs or UVCs and placement of a
peripherally inserted central catheter (PICC) are
invasive monitoring techniques.
Umbilical Artery Catheter Placement
PROCEDURE
Determine the size and length of the catheter to be
inserted. For infants weighing more than 1250 g,
use a 5-Fr catheter, and for infants weighing less
than 1250 g, use a 3.5-Fr catheter. Figs. 7.3 and
7.4 correlate total body length with the length of
the catheter to be inserted. Whereas these charts have
worked reasonably well in larger preterm and term
infants, the Wright formula (4 × birth weight in kilograms + 7) resulted in significantly better placement
in VLBW infants.
22,29
A comparison of formulas for
the length of UAC placement found superior correct
placement of the tip of the catheter with use of the
Wright formula.
29
20
18
16
14
12
10
8
6
4
2
0
30 34 38 42
FIGURE 7.4 Graph for distance of catheter insertion from umbilical ring for
high placement (T8). (From Rosenfeld W, Estrada R, Jhaveri R, et al. Evaluation of graphs for insertion of umbilical artery catheters below the diaphragm.
J Pediatr. 1981;98(4):627.)
46 50 54 58
Place the infant in a supine position on a radiant
warmer bed or in an incubator. Ensure continuous temperature monitoring. Skin temperature
should remain between 36°C and 37°C (96.8°F
and 98.6°F). Provide appropriate oxygenation and
ventilation. Ensure cardiorespiratory and oxygen
saturation monitoring. Restrain the infant’s hands
and feet to prevent him or her from contaminating
the sterile field and interfering with the placement
procedure. Don cap and mask. Open the catheterization tray; most units now use commercially available disposable trays. Catheterization tray contents
are shown in Fig. 7.5. Wash hands and dry with
sterile towel before the procedure. Put on sterile
gown and gloves.
Connect the catheter to the stopcock, and
flush and fill the entire system, including the
catheter, with flush solution. Turn off the stopcock to the catheter to prevent fluid from
draining out of the catheter during insertion
and securing of the catheter. Cleanse the cord
and base of the umbilicus with either povidone-iodine or chlorhexidine with alcohol three
times and allow the site to air-dry.33 Remove
the povidone-iodine with alcohol. For infants
weighing less than 1000 g, utilize sterile water.
Avoid using an excess of skin disinfectant so
the infant is not lying in the solution during
the procedure. Any residual skin disinfectant
should be washed off the infant carefully after
the procedure is completed.
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FIGURE 7.5 Argyle umbilical vessel catheter insertion tray. (Courtesy Tyco/Healthcare Kendall-LTP.)
Drape the infant by placing an eye sheet over the
umbilicus. An alternative method is to use sterile
drapes, as follows:
1. Hold the diagonal corners of one drape, and
allow the top half to fold over the bottom half.
The result is a V shape.
2. Place the tips of the V on either side of the
umbilicus.
3. Repeat with another drape, and place on the
other side of the umbilicus. The umbilical stump
is now visible yet surrounded by drapes.
After the UAC is inserted, the drapes can be
removed easily without the need to pass the stopcock and catheter through an eyehole of a drape
or cut or tear the eyehole drape. Ensure that the
infant’s head and feet remain visible during
the procedure to assess color. A small eye drape
with adhesive backing (such as a Steri-Drape)
has the advantage of being transparent, so that
the infant’s color can be seen, and temperature
can be maintained. Towel drapes may interfere
with a radiant heat source used for temperature
regulation.
Place an umbilical cord tie (e.g., umbilical cord
tape) around the base of the cord to control bleeding.
A single overhand knot is preferred because it allows
tightening as needed. Using tissue forceps, pick up
the cord and cut it with a scalpel about 1 to 1.5 cm
above the base. Arterial spasm allows only minimal
bleeding. Identify the vessels. There are usually two
arteries and one vein. The arteries are small, thick
walled, and constricted. The vein is larger, thin
walled, and usually gaping open. If the vein is at
the 12-o’clock position, the arteries are usually at the
4- and 8-o’clock positions (Fig. 7.6).
Stabilize the umbilical stump by grasping the
cord between the thumb and index finger or
grasping the edge of the stump with a mosquito
hemostat. Ensure that the hemostat does not crush
the umbilical vessels. With iris forceps, dilate one
of the arteries by placing the tips of the forceps
in the artery and gently allowing them to spring
open. This procedure may need to be repeated
several times. In ELBW infants, the artery may be
so small that it may be necessary to initially insert
one forcep tip and then both to dilate the artery.
While grasping one side of the wall of the dilated
artery with small forceps, gently insert the catheter. An alternative method is to insert the catheter
between the open prongs of the forceps used to
dilate the artery. Instructional aids such as Baby
Umb (Medical Plastics Laboratory, Inc., Gatesville,
Umbilical tape
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Umbilical
vein
Umbilical
arteries
FIGURE 7.6 Umbilical tape and position of umbilical vessels.
CHAPTER 7 Physiologic Monitoring
171
TX) and the Umbilical Artery Catheterization
Slide-Tape Neonatal Educational Program (Charles
R. Drew Postgraduate Medical School, Los Angeles,
CA) are helpful. As the catheter passes into the
artery, resistance may be encountered at several
points, as follows:
• At the umbilical cord tie (tape): The tie (tape)
may be tied too tightly. Loosen slightly.
• At the point at which the umbilical artery turns
downward (caudal) into the abdomen: Steady,
gentle pressure is important because forceful
pressure may cause the catheter to perforate the
artery wall and create a false channel.
• At the point at which the umbilical artery joins
the external iliac artery: Once again, steady, gentle pressure is important.
Insert the catheter to the predetermined length.
Aspiration on the syringe should provide immediate
blood return. Lack of blood return may indicate the
following:
• The catheter is not inserted far enough. Insert
farther.
• The vessel wall has been perforated, or a false
channel has been created. If the catheter has
pierced the vessel wall, repeat the procedure
using the other artery.
• The catheter is kinked. Pull back slightly and
then advance.
• The stopcock is turned off. Correct the stopcock
position. Return aspirated blood to the infant;
then clear the catheter with flush solution.
There are several methods to secure the catheter,
including suturing to the umbilical stump, use of an
FIGURE 7.7 Umbilical artery catheter secured in “goalpost” design.
adhesive-type tape after using skin prep to protect
the skin, use of a “goalpost” (Fig. 7.7), and use of
sterile transparent dressing. The literature denotes
these methods, but there is no evidence to delineate
the most beneficial method. Advantages and disadvantages of each method including skin issues, cost,
and ease of use need to be researched.
14
Connect the stopcock to the intravenous (IV)
solution, and set the prescribed infusion rate on
the infusion pump. Ensure that no air is in the tubing, stopcock, or catheter. All connections must be
secure. Automatic infusion pumps must be used for
UACs because arterial pressure must be overcome
to permit IV fluid infusion. Determine catheter
placement by a radiologic examination (abdominal,
chest, “babygram,” or ultrasound depending on
placement of the catheter). Fig. 7.8 shows how the
UAC appears on a lateral x-ray film.
Note that the catheter enters the umbilicus
and travels inferiorly before turning superiorly.
This “leg loop” is characteristic of an arterial
catheter. A UAC follows the aorta and is positioned
slightly to the left of the patient’s vertebral column.
Optimal placement is below the renal arteries
and above the aortic bifurcation (L3 to L4) for
a low catheter and below the left subclavian artery
and above the diaphragm (T7 to T9) for a high
catheter.24 High catheter placement has fewer
complications.3 Fig. 7.9 shows high catheter place-
ment, and Fig. 7.10 shows low catheter placement.
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FIGURE 7.8 High catheter demonstrating “leg loop.”
FIGURE 7.9 Umbilical artery catheter in high position (T8).
FIGURE 7.10 Umbilical artery catheter in low position (L3).
If the catheter is too high, measure on the x-ray
film the distance from the tip of the catheter to
the desired level, and pull the catheter back the
appropriate distance. Some clinicians multiply this
length by 0.8 to account for the magnifying effect
of the x-ray film. If the catheter is placed too low,
the catheter cannot be advanced but must be
removed and replaced because the external portion of the original catheter is no longer sterile.
Remove the umbilical cord tie (tape), or maintain
the tie very loosely so as not to obstruct blood flow
to the umbilical area.
As a teaching model, the umbilical cord can be
used for teaching the procedure of both arterial and
venous catheterization. Many of the steps can be
effectively carried out using a fresh placenta. Special
UACs and monitors are available for continuous
PaO2 or oxygen saturation monitoring.
NURSING CARE AND USE OF UMBILICAL
ARTERY CATHETERS
Infants can be positioned on their sides or their
backs. The abdominal position may be avoided
because accidental slipping, kinking, and removal
of the catheter may occur without being imme-
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diately apparent. If the abdominal position is used,
the catheter should be monitored continuously;
ensure that pressure alarms are on with parameter
settings that would rapidly detect pressure changes.
Care needs to be taken so that the infant is positioned to prevent dislodgement of the catheter.
Diapers are effective for preventing the feet and toes
from becoming entangled in the catheter. The dia-
per is folded below the umbilicus. If the infant
is receiving phototherapy and thus is not diapered,
leg restraints or positioning aids may be indicated.
A mitten or positioning aids are useful to prevent
hands and fingers from contacting the catheter.
Positioning the catheter away from the extremities
lessens the chance of accidental dislodgement. Unless
using a transparent dressing to secure the UAC,
a dressing over the umbilicus is unnecessary.
Nontransparent dressings inhibit inspection of
the umbilicus and evaluation of the catheter. The
IV tubing, connecting tubing, and stopcock should
be changed daily. Clots form in the stopcock, so
changing it daily prevents the likelihood of thrombus
formation. Blood backing into the catheter can be
caused by the following:
• Increased intraabdominal pressure, commonly
caused by vigorous infant crying
• Disconnection of tubing or a loose connection
• Stopcock turned in wrong direction
• Infusion pump malfunction
• A leak in the filter or tubing or a crack in the
stopcock
CHAPTER 7 Physiologic Monitoring
FIGURE 7.11 Stopcock off to IV solution; 1 to 2 mL aspirated into syringe.
173
PROCEDURE FOR OBTAINING AN
ARTERIAL BLOOD GAS SAMPLE
Drawing blood samples from an umbilical
catheter is a sterile procedure. Samples may be
obtained for blood gas analysis and to obtain laboratory specimens. Necessary items include a syringe
for initially aspirating IV fluid and blood from the
catheter, a heparinized blood gas syringe (if a blood
gas sample is to be obtained), a syringe for aspirating
laboratory samples (if laboratory samples are to be
obtained), and a syringe containing flush solution.
The reinfusion method of obtaining blood sam-
ples is described. This practice involves returning
the “discard” blood and, in theory, minimizes
patient blood loss.6 Remove the stopcock cap and
place it down so that sterility will be maintained.
Attach the empty aspiration syringe to the stopcock.
Turn off the stopcock to the IV solution so that the
IV solution stops flowing. Aspirate 1 to 2 mL from
FIGURE 7.12 Stopcock in neutral position.
the catheter into the dry aspiration syringe (Fig. 7.11).
The IV fluid is prevented from infusing, and aspiration
clears the catheter of IV fluid. Turn the stopcock to
the neutral position (Fig. 7.12), remove the syringe
while keeping the tip sterile, and replace it with the
heparinized blood gas syringe or laboratory sample
syringe. The neutral position of the stopcock prevents
contaminating the sample with IV fluid and prevents
blood loss from the infant.
CAUTION: Never allow blood to drip from
an open stopcock. Attach the sample syringe.
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FIGURE 7.13 After blood is aspirated into heparinized 1-mL syringe, stopcock
is placed in neutral position before syringe is removed.
Turn the stopcock off to the IV fluid. Using steady,
even pressure, aspirate blood into the laboratory
or heparinized blood gas sample syringe. Turn the
stopcock to the neutral position, and remove the
syringe (Fig. 7.13).
For blood gas samples, remove any air from
the syringe (because air bubbles in the sample will cause an artificial rise in PaO2 and a
slight fall in PaCO2), cap the end, and chill it
to preserve values. Attach the aspiration syringe
containing the aspirated blood and IV fluid.
Slightly aspirate to remove any air in the stopcock,
and then slowly infuse the aspirated blood and IV
fluid. Turn the stopcock to the neutral position,
and remove the aspiration syringe. Replace the
now-empty aspiration syringe that had aspirated
blood and IV fluid in it with the syringe filled
with flush solution. Turn the stopcock off to the
IV fluid. Slightly aspirate to remove any air in the
stopcock, and then slowly infuse the flush solution
until the catheter is clear. Return the stopcock
to the off position, allowing the IV fluid to now
infuse. Replace the stopcock cap. Record the
amount of blood removed from the infant and the
amount of flush solution used to clear the catheter.
Newer methods of gradual, automatic aspiration
should be considered if available to prevent abrupt
changes in arterial or cerebral pressure.
To ensure the integrity of all connections, the
stopcock and other connections must be visible
at all times. Do not place the stopcock and other
connections under linen, because this would
hamper the immediate detection of an accidental
disconnection that would cause severe blood loss
in the infant. Immediately remove any air in the
tubing or catheter because air is a potential embolus.
It is best removed through the stopcock. If the air has
passed the stopcock, it can be aspirated back into a
syringe easily.
Obtaining an arterial blood gas specimen from
a high UAC is better tolerated in premature
infants when the entire procedure is done slowly.
Premature and ill term infants have limited cerebral
blood flow (CBF) autoregulation. Rapid drops and
rises in CBF, especially in the first few days of life, can
contribute to neuronal injury and intracranial bleeding.
Rapidly obtaining blood samples from a UAC has
detrimental hemodynamic effects on CBF thus,
sampling from the UAC should be done slowly.
6
Umbilical Vein Catheter Placement
PROCEDURE
Determine the size and length of the catheter to
be inserted. A 5-Fr catheter is normally used in
the UVC placement procedure. The ELBW infant
may require a 3.5-Fr catheter. To determine the
length of the catheter to be inserted, the distance
from the umbilicus to the sternal notch should
be measured and multiplied by 0.6. Complete
steps for the placement procedure are found in the
Umbilical Artery Catheter Placement section earlier
in this chapter. The only difference is that the vein
is used instead of the artery. The catheter can be
advanced to the desired position easily. The vein is
usually gaping open and does not require dilation. The catheter should lie in the inferior vena cava
with the UVC above the diaphragm but below the
right atrium of the heart. Catheter position must be
ensured. Historically, position confirmation was by
radiologic examination, using the anteroposterior
(AP) and lateral views. Ultrasonography is rapid
and determines correct catheter tip placement
and prevention of complications such as pericardial
effusion and tamponade.18 UVCs do not have the
“leg loop” found on the lateral x-ray film of
UACs. A UVC follows the inferior vena cava and
is positioned slightly to the right of the patient’s
vertebral column. The catheter should be secured in
CHAPTER 7 Physiologic Monitoring
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FIGURE 7.14 Peripherally inserted central catheters and introducers. (Courtesy Becton, Dickinson and Company, Franklin Lakes, NJ.)
175
the same manner as for a UAC. The nursing care
and procedure for drawing blood samples from a
UVC are the same as those for a UAC.
Peripherally Inserted Central
Catheter Placement
PICCs are silicone or polyurethane products available in a variety of styles including single catheter
and needle introducer to a complete insertion kit
with instruments, skin disinfectant, and cap, mask,
gown, and gloves. Some products provide a stylet
and several feature breakaway (splittable) needle
introducers. PICCs are available in a variety of sizes
for the neonatal population from 20 gauge (3 Fr) to
28 gauge (1.2 Fr).
PICCs typically are inserted for the following
reasons:
• Infants who require IV access that is expect-
ed to be necessary for an extended period
• Infants with limited access
• As a transition from umbilical catheters for
infants weighing less than 1000 g
• As a first-line catheter for infants weighing
1000 to 1500 g
• Infants with gastrointestinal anomalies, necro-
tizing enterocolitis, or gastrointestinal diseases
that will require surgical correction
PICCs have long been used to provide highly
concentrated parenteral nutrition and hyperosmolar
medications.
1,43,52
These catheters are relatively
easy to insert, affordable, and low maintenance and
preclude surgical placement of central venous catheters. Due to the extensive dwell time, PICCs
significantly reduce or eliminate the need for
repeated painful procedures such as peripheral
venipunctures, thus improving patient and parent satisfaction.
PROCEDURE
The insertion sites for PICC lines include the bra-
chial cephalic veins, the axilla, the scalp vessels, and
the saphenous veins. This sterile procedure can be
performed when the infant is on a radiant warmer
or in an incubator. A video demonstrating this procedure is available.
28
For an arm or hand insertion, measure the distance from the insertion site to the axilla and then
to 1 cm above the nipple line. If the catheter is to
be inserted in the scalp, measure from the insertion
site to 1 cm above the nipple line, and for a leg
insertion, measure from the insertion site to 1 cm
above the umbilicus or to the level of the inferior
vena cava.
Determine the size and length of the catheter to
be inserted—PICC and introducer: 20 to 28 gauge,
varying lengths 20- to 65-cm catheter (Fig. 7.14) .
Recommendations to trim lengthy catheters vary
with manufacturer. A national survey found that
75% of respondents trim catheters. Devices supplied
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by the catheter manufacturer for catheter trimming
resulted in a precise cut, whereas scissors produced
a ragged cut.
43
A eutectic mixture of lidocaine and prilocaine (various manufacturers) anesthetic cream
or a local anesthetic can be considered before
the procedure begins, but these should be used
cautiously because of variable absorption rates and
the potential for cardiovascular collapse in neonates
(see Chapter 12). Place the infant in the supine
position on a radiant warmer bed or in an incubator. Ensure continuous temperature monitoring.
Skin temperature should remain between 36°C and
37°C (96.8°F and 98.6°F). Provide appropriate oxygenation and ventilation. Ensure cardiorespiratory
and oxygen saturation monitoring.
Restrain the infant’s hands and feet to prevent
him or her from contaminating the sterile field and
interfering with the placement procedure, or swaddle the infant, with the site to be used exposed. For
hand or arm insertion sites, turning the infant’s head
toward the insertion site will cause a slight occlusion
of the jugular vein so that, as the catheter is passed
into the subclavian vein, the risk for the catheter
advancing upward into the jugular is diminished.
52
Don cap and mask. Open the PICC insertion
tray; most units now use commercially available
disposable trays. PICC insertion tray contents are
shown in Fig. 7.15. Open the PICC and introducer
(if packaged separately from the PICC insertion tray).
Wash hands and dry with sterile towel before the
procedure. Put on a sterile gown and gloves. Connect
a lipid-compatible T-connector extension tubing to a
syringe of flush solution, and fill the entire apparatus.
Grasp the extremity to be used with sterile gauze
so that an occlusive dressing can be applied to the
distal part of the extremity, thus allowing manipulation of the extremity and precluding contamination
of the insertion site by bacteria from distal sites.
Cleanse the site with either povidone-iodine or
chlorhexidine three times, and allow the site to airdry. Remove the povidone-iodine with alcohol. For
infants weighing less than 1000 g, use sterile water.
Avoid using an excess of skin disinfectant so
the infant is not lying in the solution during the
procedure. Any residual skin disinfectant should
be washed off the infant carefully after the procedure is completed. Place sterile drapes under
the exposed insertion site. Reglove with new sterile
gloves. Place the introducer, catheter either with
or without stylet (clinician’s choice), syringe, and
sterile forceps on the sterile field near the planned
insertion site. Insert the catheter into the introducer,
being cautious if a stylet is used not to let the stylet
extend beyond the tip of the introducer.
Insert the introducer tip at a flat angle to access
the vein. The introducer is not advanced into the
vein; it is used only as an introducer. At this point,
there will probably be no blood return. Once the
introducer is in the vein, pick up the catheter with
FIGURE 7.15 Disposable tray used for PICC insertion. (Courtesy Becton, Dickinson and Company, Franklin Lakes, NJ.)
CHAPTER 7 Physiologic Monitoring
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177
the sterile forceps and gently advance the catheter
to the premeasured length. Blood should fill the
catheter. If the catheter is not advancing, pull the
catheter back beyond the point of the introducer
and reattempt to cannulate the vein. Once the
catheter is advanced to the premeasured length,
remove the stylet if used, and attach an empty
sterile syringe. If a breakaway cannula is used, gently retract the cannula and slowly peel it apart to
prevent premature breakage. Blood should be aspirated easily with a syringe. Flush the catheter with
0.5 to 1 mL of flush solution. Secure the catheter
using sterile tape or nonfiber adhesive strips at the
insertion site. Wrap extra catheter material into a
coil above or below the joint to prevent occlusion.
Attach the lipid-compatible T-connector extension
set, and secure it to the extremity. Dress the insertion site, extra catheter loops, and PICC catheter
to the T-connector area with a sterile, transparent
occlusive dressing. Ensure that the dressing does not
completely encircle the extremity causing a tourniquet effect. Label the dressing with the gauge and
length of the catheter, the line type (PICC), and the
initials of the insertion person.
Catheter position must be ensured by anteroposterior and lateral x-ray films, ultrasonography, or
echocardiography.16 For PICC lines inserted in
the upper extremities, axillae, or scalp vessels,
the catheter should lie in the superior vena cava
above the right atrium of the heart. Catheters
placed in other vessels have a significantly higher rate of thrombus formation and infection. An
increase in PICC line infections is directly related
to increased frequency of venipunctures, especially
when no concurrent antibiotics are being used.12
For PICC lines inserted in the lower extrem-
ities, the catheter should lie in the inferior
vena cava below the right atrium of the heart.
Catheter placement in the right atrium can lead to
complications of dysrhythmias, pleural effusion, and
perforation with cardiac tamponade.
NURSING CARE OF PICCS
Infants should be positioned to prevent dislodgement or kinking of the catheter. Diapers
are effective for preventing the feet and toes from
becoming entangled in the IV tubing. If the infant
is receiving phototherapy and thus is not diapered,
leg restraints or positioning aids may be indicated.
A mitten or positioning aids are useful to prevent
hands and fingers from contacting the catheter
52
dressing and IV tubing. Positioning the catheter
away from the extremities lessens the chance of
accidental dislodgement. The IV tubing should be
changed according to the standard of care. Observe
for disconnection of tubing or a loose connection, and ensure an intact and occlusive insertion site dressing.
The occlusive dressing should be changed
only when the integrity of the dressing has
been lost. A small amount of blood at the inser-
tion site is not a reason to change the occlusive
dressing. Maintaining integrity of the occlusive
dressing is instrumental in decreasing the risk
for infection.
Changing the current dressing is indicated
when it is no longer occlusive. The occlusive
dressing is changed under sterile conditions. The
person performing the dressing change dons a cap,
mask, and sterile gloves. Changing the dressing entails
removing the transparent film covering the area, cleaning the insertion site with either povidone-iodine
solution or chlorhexidine, allowing this to dry, and
then cleaning the site with sterile water to remove
the preparation agent from the skin. If the nonfiber
adhesive tape or strips are no longer adhesive, they are
replaced. Dress the insertion site, extra catheter loops,
and PICC catheter to the T-connector area with a
sterile, transparent occlusive dressing. Ensure that the
dressing does not completely encircle the extremity
causing a tourniquet effect. Label the dressing with the
gauge and length of the catheter, the line type (PICC),
and the initials of the insertion person.
Because of the small gauge, PICCs are not
routinely used for blood sampling. Clotting of
the catheter may rapidly occur. Because the IV tubing does not contain a stopcock, significant blood
loss and introduction of air into the venous circulation can occur.
Peripherally Inserted Midline
Catheter
In infants not requiring or unable to receive a central catheter (vena cava placement) yet still needing
IV access for a few days such as for antibiotic therapy, a peripherally inserted midline catheter (PIMC)
can be used. PIMCs are inserted to the midclavicular line. These products are similar to PICCs and are
available as a single needle introducer and catheter
or as a complete kit.
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Removing Umbilical Artery, Vein,
and Peripherally Inserted Central
Catheters
When the UAC, UVC, or PICC is no longer
needed, it is removed. For UAC catheter removal,
make certain the cord tie is snug. Sterile gauze is
needed, and a suture removal kit should be available
if the catheter was sutured in place. Turn off the
stopcock to the patient and the IV fluid. Withdraw
the catheter to 3 cm, and leave it in place for 30
minutes before withdrawing it completely. This
procedure works well for infants with respiratory or
abdominal issues because it avoids the application
of external pressure to the abdomen. Alternatively,
withdraw the catheter slowly over several minutes,
allowing for the artery to spasm. Pinch the umbilical stump with the sterile gauze for 5 minutes
until hemostasis is achieved. Observe the umbilicus
for active bleeding or oozing. Observe the lower
extremities and buttocks for diminished perfusion
secondary to a thrombus or embolus.
The procedure is similar for UVCs, with the
exception that the catheter can be slowly withdrawn in one step. Pinch the umbilical stump with
the sterile gauze for 5 minutes until hemostasis is
achieved. Observe the umbilicus for active bleeding
or oozing. Observe the patient for respiratory distress secondary to a pulmonary embolus.
For PICC removal, clamp the catheter, turn
off the IV fluid infusion, and withdraw the catheter slowly and steadily. Apply pressure over the
insertion site with the sterile gauze for 5 minutes
until hemostasis is achieved. Observe the insertion
site for active bleeding or oozing. Ensure that the
entire catheter was removed.
Oxygen Saturation Monitoring by
Pulse Oximetry
Oxygen saturation monitoring by pulse oximetry
involves placing a small sensor on the infant in
such a manner that his or her finger, toe, foot,
or wrist comes between the light source and
the photoreceptor. The light source emits wave-
lengths of light in the red and infrared spectrums.
The difference between the absorption of the light
is picked up by the receptor that is placed directly
opposite the light source. The calculation of the
ratio of oxyhemoglobin and deoxyhemoglobin
is displayed as the percent of oxygen saturation.
Key to accuracy of the monitor is that the light
source and the receptor must be directly opposite
each other over an area in which a pulse can be
detected.
Oxygen saturation monitoring provides con-
tinuous and instantaneous readout of the oxygen saturation in the infant. In comparison with
a blood gas analyzer, which calculates the relative
oxygen saturation based on established nomograms,
the oxygen saturation monitor measures the
actual saturation of the hemoglobin. Calculated
values using standard nomograms do not reflect
shifts in the affinity of oxygen for hemoglobin based
on changes in the patient’s temperature, pH, PCO2,
or 2,3-DPG.
An inorganic phosphate produced in red cells;
2,3-DPG binds to the beta chain of reduced hemoglobin (Hb), lowering Hb’s affinity for O2 and by
extension, facilitating O2 release to tissues, causing a
“right shift” of the O2 dissociation curve. 2,3-DPG
further shifts the curve to the right by lowering
the red cells’ pH. When transfused, red cells regain
50% of the 2,3-DPG within 3 to 8 hours and 100%
within 24 hours.
The oxygen saturation monitor relies on
adequate perfusion to the site and the ability
to detect arterial pulsations; thus, if it is placed
distal to a blood pressure cuff, the reading will be
inaccurate while the cuff is inflated. Newer models
of pulse oximetry reduce the artifact that results
from motion and low perfusion. These newer models also are indifferent to ambient light, whereas
older models were affected by light sources such as
phototherapy. Newer neonatal probes have built-in
external light source protectors. Pigmentation of
the patient’s skin may produce artificially high
readings, especially at lower oxygen levels.37
However, a recent comparison of two commonly used pulse oximeters found no significant difference in systematic bias based on skin pigment
(comparing darker to lighter pigmentation in
infants with hypoxemia) with either oximeter.
Oxygen saturation is more indicative of the total
oxygen content of the blood than is PaO2 and is
the most sensitive to hypoxemia when it is on the
steep part of the oxygen dissociation curve (see Fig.
7.1). Keeping the SaO2 at 90% to 92% keeps
the infant in a normoxemic state under most
conditions. Oxygen saturation monitoring by pulse
oximetry generally is considered reliable and practical for use in infants over a wide range of birth
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