7. Use reliable infusion pumps that control rate and detect

obstruction.

8. Limit infusion of hypertonic solutions and do not

deliver bolus feedings beyond the pylorus.

9. Consider the effect of continuous feedings on medication absorption.

282 Section VII ■ Tube Replacement

E

D

C

A B

Fig. 40.3. Radiographic examples of misplaced feeding

tubes. A: Tube coiled in the oropharynx and upper esophagus,

simulating an esophageal atresia. B: Tube into the left mainstem bronchus. C: Tube coiled in the lower esophagus.

D: Tube doubled on itself in the stomach with its distal end in

the esophagus (arrow). E: Tube the esophagus. A rush may be

heard on auscultation over the stomach when air is injected

through a tube lying in this position, making an unreliable

verification of gastric location.

Chapter 40 ■ Gastric and Transpyloric Tubes 283

F. Special Circumstances

1. See Oral or Nasal Gastric Tubes (F).

G. Technique

1. Follow steps 1 through 4 above under Oral or Nasal

Gastric Tubes (G).

2. Measure distance from glabella to heels or from the tip

of the nose to the ear to the xiphoid to the right lateral

costal margin (19). Mark point with tape on transpyloric tube.

3. Turn patient onto right side and elevate the head of the

bed 30 to 45 degrees.

4. Pass transpyloric tube to predetermined depth.

5. After approximately 10 minutes with infant remaining

on right side, gently aspirate through transpyloric tube.

Tube may be in position within duodenum if aspirate is

a. Without air

b. Bilious (gold or yellow in color)

c. pH >6, although this method alone is not reliable

(4,19)

6. Verify placement with radiograph. The tip of the tube

should be just beyond the second portion of duodenum

(4,19) (Fig. 40.5).

7. Avoid pushing to advance tube after initial placement.

If tube is not in far enough, retape to give external slack

and to allow peristalsis to carry tip to new position.

8. After verifying correct positioning, close transpyloric

tube or start continuous infusion.

9. Document patient response, observing any physiologic

changes and verifying tube placement. Note the location of the tube at the nares and document it on the

chart. Check this location before each use.

10. Transpyloric tubes may also be placed with fluoroscopic guidance.

Fig. 40.4. Chest radiograph showing esophageal perforation by

an orogastric tube.

A

B

Fig. 40.5. A: Abdominal radiograph showing appropriate position

of transpyloric tube. B: Radiographic demonstration of a transpyloric

feeding tube that has passed the ligament of Treitz, well below the

appropriate level, increasing the risk of perforation or nutritional

dumping.

 

Chapter 40 ■ Gastric and Transpyloric Tubes 281

amount of air into the tube to reposition the nasogastric tube away from the stomach wall. Avoid pushing

against any resistance. If no aspirate is obtained, consider verifying placement by radiography (18).

c. Suspect perforation or misplacement if no air or

fluid is returned or if there is onset of respiratory distress, blood in the tube, or difficult insertion.

d. Verify tube placement on all subsequent radiographs.

13. Secure indwelling tube to face with 0.5-inch tape.

a. For feedings, attach to syringe.

b. For gravity drainage, attach specimen trap and position below level of stomach.

c. For decompression, a dual-lumen tube, connected

to low intermittent or continuous suction, is preferred.

14. Pinch or close gastric tube during removal to prevent

emptying contents into pharynx.

15. Document patient response, observing any physiologic

changes and verifying tube placement. Note the location of the tube at the nares, and document it on the

chart. Check this location before each use.

H. Complications

1. Apnea, bradycardia, or desaturation

2. Obstruction of obligatory nasal airway (15)

3. Irritation and necrosis of nasal mucosa (15)

a. Epistaxis

b. Ulceration

4. Misplacement on insertion (Fig. 40.3)

a. Coiled in oropharynx

b. Trachea leading to aspiration (5,15)

c. Esophagus

d. Duodenum

5. Displacement after insertion because of inappropriate

length or fixation

a. Pulling back or coiling into esophagus (24)

b. Prolapsing into duodenum (5)

6. Coiling and clogging of tube

7. Perforation (Fig. 40.4)

a. Posterior pharynx, particularly at level of cricopharynx

b. Esophagus

(1) Submucosal, remaining within mediastinum

(2) Complete into thorax

(3) Symptoms can mimic esophageal atresia or tracheoesophageal fistula (13)

(4) Chylothorax or pneumothorax (25)

c. Stomach

d. Duodenum (26)

8. Grooved palate with long-term use of indwelling

tube (8)

9. Increased gastroesophageal reflux

10. Infection (8)

11. Breakage of tube with retention of distal portion in

stomach (27).

Transpyloric Feeding Tube

A. Indications

1. Severe gastroesophageal reflux with risk of aspiration

2. Suspected gastroesophageal reflux-associated apnea

(28)

3. Gastric distention with continuous positive airway pressure

4. Delayed gastric emptying

5. Gastric motility disorders

6. Sampling of duodenojejunal contents

7. Intolerance to gastric feeds

B. Contraindications

Clinical condition that compromises duodenojejunal

integrity: Necrotizing enterocolitis, fulminant sepsis, shock,

patent ductus arteriosus, recent small-bowel surgery

C. Limitations

1. Long-term use may be associated with fat malabsorption, although recent studies suggest that there is no

significant impact on growth over time (29).

2. There are no data to support routine use in preterm

infants (2,29,30)

D. Equipment (see also Oral or Nasal Gastric

Tubes, D.)

1. Silastic tube of appropriate size. Silastic tubes are preferred over PVC tubing, as they can remain in place for

a longer duration; PVC tubes are not recommended for

long-term use (8).

2. Continuous-infusion pump and connecting tubing

E. Precautions

1. When determining oral or nasal placement, individual

assessment must be done to weigh the risks of compromising the nasal airway.

2. Avoid pushing against any obstruction or resistance.

3. Most often, if the tube does not cross the pylorus within

the first 30 minutes after passage, it is unlikely to pass in

the next few hours, and it may be better to restart the

procedure.

4. Replace tubes per manufacturer’s recommendations. If

the tube is stiff on removal, replace next tube sooner.

5. If a tube has become partially dislodged, replace it

rather than pushing it in farther.

6. When using feedings that tend to coagulate in tubing, it

may be necessary to flush the tube periodically with air

or water.

 

280 Section VII ■ Tube Replacement

8. Nasal insertion (avoid this route in very low-birthweight

infants in whom nasal tubes may be associated with

periodic breathing and apnea) (1,8).

a. Stabilize head. Elevate tip of nose to widen nostril.

b. Insert tip of tube, directing it toward occiput rather

than toward vertex (Fig. 40.2).

c. Advance tube gently to oropharynx.

d. Monitor for bradycardia.

9. If possible, use pacifier to encourage sucking and swallowing.

10. Tilt head forward slightly.

11. Advance tube to predetermined depth.

a. Do not push against any resistance.

b. Stop procedure if there is onset of any respiratory

distress, cough, struggling, apnea, bradycardia, or

cyanosis.

12. Determine location of tip using a combination of several

measures. Radiograph of the abdomen to verify placement is the gold standard but is expensive and subjects

neonates to additional radiation. Injecting air to verify

placement is not a reliable method, as the sound of air in

the respiratory tract can be transmitted to the GI tract

(5,8,18,19). Measuring the pH of the aspirate as the sole

method to verify tip position is not reliable, as stomach

acid in infants can be weakly acidic, and the degree of

acidity of the aspirate can be affected by the timing of

feeding, the exact location in the stomach of the tube

tip (distal versus proximal), and timing of medication

delivery (18–22).

a. Aspirate any contents; describe and measure.

(1) Gastric contents may be clear, milky, tan, pale

green, pale yellow, or blood stained.

(2) Determine acidity by measuring pH. If the pH

of the aspirate is <5, one can be reasonably certain the tube is in the stomach. If the pH is ≥5,

placement should be confirmed using an additional method, such as radiography or character

of secretions (4,18,20,23).

(3) Assess for any respiratory compromise or instability.

b. If there is difficulty obtaining aspirate, use a largersized syringe, reposition the infant, and instill a small

Table 40.1

Guidelines for Minimum

Orogastric Tube Insertion Length

to Provide Adequate Intragastric

Positioning in Very LowBirthweight Infants

Weight (g) Insertion Length (cm)

<750 13

750–999 15

1,000–1,249 16

1,250–1,500 17

Data from Gallaher KJ, Cashwell S, Hall V, et al. Orogastric tube insertion length

in very low birth weight infants. J Perinatol. 1993;13:128.

Fig. 40.2. Anatomic view of the neonatal nasopharynx. The natural direction in tube insertion is toward

the nasal turbinates, where it might stop and give an impression of obstruction. By pushing the nostril up,

one can direct a tube toward the occiput with less trauma.

 

Chapter 40 ■ Gastric and Transpyloric Tubes 279

Oral or Nasal Gastric Tubes

A. Indications (1)

1. Neurologic immaturity or impairment

2. Poor oral skills

3. Respiratory instability

4. Physiologic instability

B. Contraindications

Recent esophageal repair or perforation

C. Limitations

1. Size of nares

2. Type and amount of respiratory support

3. Congenital anomalies of the nasopharynx

D. Equipment

1. Suction equipment

2. Cardiac monitor

3. Infant tube of appropriate size

4. 0.5-inch hypoallergenic tape

5. Sterile water

6. 3- or 5-mL syringes

7. Stethoscope

8. Gloves

E. Precautions

1. When determining oral or nasal placement, individual

assessment must be done to weigh the risks of compromising the nasal airway.

2. Measure and note appropriate length for insertion.

3. Have suction apparatus readily available in case there is

regurgitation.

4. Do not push against any resistance. Perforation may

occur with very little force or sensation of resistance.

5. Do not instill any material before verifying tube placement.

6. Evaluate for possible esophageal perforation if any of

the following occur (8,13–15)

a. Bloody aspirate

b. Increased oral secretion

c. Respiratory distress

d. Pneumothorax

7. Stop the procedure immediately if there is any respiratory compromise.

F. Special Circumstances

1. Feeding with umbilical catheters in situ is controversial

and should be done with caution, as there are insufficient data to guide practice (8,16).

2. Tubing should be vented between feedings if continuous positive airway pressure is in place (3).

G. Technique

1. Wash hands and put on gloves, maintaining aseptic

technique.

2. Clear infant’s nose and oropharynx by gentle suctioning as necessary.

3. Monitor infant’s heart rate and observe for arrhythmia

or respiratory distress throughout procedure.

4. Position infant on back with head of bed elevated.

5. Measure length for insertion by measuring distance

from tip of the nose to ear to halfway between the

xiphoid and umbilicus (3,17) (Table 40.1). Mark length

on feeding tube with a loop of tape.

6. Moisten end of tube with sterile water or saline.

7. Oral insertion

a. Depress anterior portion of tongue with forefinger

and stabilize head with free fingers.

b. Insert tube along finger to oropharynx.

A B

Fig. 40.1. A: Silastic gastric feeding tube. B: Double-lumen replogle tube.

 

D. Types of Tubes (6,7)

1. Feeding tubes

a. Single-lumen tubes are used for gastric or transpyloric feeding via the oral or nasal route, or for temporary gastric decompression of air or gastric contents.

They are made of silastic, silicone, polyurethane, or

polyvinyl chloride (PVC) and are radio-opaque for

location on radiography. They are incrementally

marked in centimeters, and usually have two to four

side holes at the distal end (Fig. 40.1A).

(1) Silastic, silicone, and polyurethane tubes are

softer and can remain in situ for up to 30 days, or

per manufacturer’s recommendations, although

individual practice guidelines should be followed. Silastic tubes are preferred, especially in

preterm infants weighing <750 g (8).

(2) PVC tubes are stiffer and easier to insert.

However, they are not recommended for longterm use because the plasticizers are leached,

stiffening the tube and can lead to esophageal

perforation (8,9). Manufacturer recommendations for frequency of tube change can range

from every 6 hours to every 5 days, so individual

practice guidelines should be followed.

b. Available for neonates in sizes 3.5 to 8 Fr and in a

variety of lengths. The smaller diameter tubes will

have slower rates of flow. Tube length will vary

depending on the depth of placement and whether

the tube is to be gastric or transpyloric.

c. Weighted, stylet-containing tubes are not recommended in the neonatal population due to the risk

of perforation.

2. Suction/decompression tubes

a. Single-lumen feeding tubes maybe used for occasional or intermittent nasogastric aspiration of stomach contents.

b. Double-lumen (Replogle) tubes are preferable for

continuous gastric decompression or for continuous

suction to clear secretions from the upper esophageal pouch in infants with esophageal atresia prior

to surgery (10–12).

(1) The wider lumen is attached to the suction

device for gastric decompression or esophageal

clearing, and the second, smaller lumen is for

airflow to prevent adherence of the catheter to

the mucosal wall (Fig. 40.1B).

(2) These catheters are also radio-opaque, marked

incrementally and have multiple side holes at

the distal end.

(3) Available in 6, 8, and 10 Fr; vary in length.

Manufacturer’s recommendations should be followed for frequency of tube change.

 

12. Pezzati M, Filippi L, Chiti G, et al. Central venous catheters and

cardiac tamponade in preterm infants. Intensive Care Med. 2004;

30:2253.

13. Kurian MS, Reynolds ER, Humes RA, et al. Cardiac tamponade

caused by serous pericardial effusion in patients on extracorporeal

membrane oxygenation. J Pediatr Surg. 1999;34:1311.

14. Becker JA, Short BL, Martin GR. Cardiovascular complications

adversely affect survival during extracorporeal membrane oxygenation. Crit Care Med. 1998;26:1582.

15. Tsang TS, Freeman WK, Barnes ME, et al. Rescue echocardiographically guided pericardiocentesis for cardiac perforation complicating catheter-based procedures: The Mayo Clinic ­experience.

J Am Coll Cardiol. 1998;32:1345.

16. Tsang TS, Oh JK, Seward JB. Diagnosis and management of cardiac tamponade in the era of echocardiography. Clin Cardiol.

1999;22:446.

17. Tsang TS, El-Najdawi EK, Seward JB, et al. Percutaneous echocardiographically guided pericardiocentesis in pediatric patients:

evaluation of safety and efficacy. J Am Soc Echocardiogr. 1998;

11:1072.

18. Berg RA. Pulsus paradoxus in the diagnosis and management of

pneumopericardium in an infant. Crit Care Med. 1990;18:

340.

19. Traen M, Schepens E, Laroche S, et al. Cardiac tamponade and

pericardial effusion due to venous umbilical catheterization. Acta

Paediatr. 2005;94:626.

20. Muhler EG, Engelhardt W, von Bernuth G. Pericardial effusions

in infants and children: injection of echo contrast medium

enhances the safety of echocardiographically-guided pericardiocentesis. Cardiol Young. 1998;8:506.

21. Watzinger N, Brussee H, Fruhwald FM, et al. Pericardiocentesis

guided by contrast echocardiography. Echocardiography. 1998;

15:635.

278

Allison M. Greenleaf

40 Gastric and Transpyloric Tubes

A. Definitions

1. Enteral feeding is defined as providing nutrients distal

to the oral cavity.

2. A gastric tube is a tube inserted via the nose or mouth to

the stomach.

3. A transpyloric tube is a tube passed via the nose or

mouth, through the stomach and pylorus to the duodenum or jejunum.

B. Purpose

1. To provide a route for feeding (1)

2. To administer medications

3. To sample gastric or intestinal contents

4. To decompress and empty the stomach

C. Background

1. Oral feeding may be compromised in neonates due to

neurobehavioral immaturity, physiological instability,

or respiratory compromise.

2. In preterm infants, enteral feeds stimulate the secretion

of gastric hormones, influence development of the gastrointestinal (GI) tract, reduce the risk of sepsis, and

decrease length of hospitalization (2).

3. Incorrect placement of gastric and transpyloric tubes

is common, with incidence ranging from 21% to 59%,

and can lead to substantial morbidity and mortality

(3–5).

 

Chapter 39 ■ Pericardiocentesis 277

4. Draining a large volume from the pericardial space can

alter cardiac preloading conditions significantly, and

some infants may benefit from intravascular fluid

boluses after the pericardium is drained.

5. Pericardiocentesis is often an urgent or emergency procedure. The technique for pericardiocentesis described

above applies when there is time for each step. In an

infant with significant hemodynamic compromise, the

operator may be forced to omit certain steps in the interest of time. This requires a judgment as to the baby’s clinical status and the time delay involved for any given step,

such as waiting for the ultrasound machine, preparing a

larger sterile field, or assembling a three-way stopcock system. In extreme cases, this life-saving procedure might

consist of pouring or swabbing Betadine over the subxiphoid area, followed by “blind” aspiration using any available needle and syringe, without anesthetic, and before

any other equipment is available at the bedside (15).

K. Complications (15–17,20,21)

1. Pneumopericardium

2. Pneumomediastinum

3. Pneumothorax

4. Cardiac perforation

5. Arrhythmia

6. Hypotension (if a large effusion is drained)

References

1. Nowlen TT, Rosenthal GL, Johnson GL, et al. Pericardial effusion and tamponade in infants with central catheters. Pediatrics.

2002;110:137.

2. Tsang TS, Barnes ME, Hayes SN, et al. Clinical and echocardiographic characteristics of significant pericardial effusions following

cardiothoracic surgery and outcomes of echo-guided pericardiocentesis for management: Mayo clinic experience. 1979–1998. Chest.

1999;116:322.

3. Tamburro RF, Ring JC, Womback K. Detection of pulsus paradoxus

associated with large pericardial effusions in pediatric patients by

analysis of the pulse-oximetry waveform. Pediatrics. 2002;109:673.

4. Heckmann M, Lindner W, Pohlandt F. Tension pneumopericardium in a preterm infant without mechanical ventilation: a rare

cause of cardiac arrest. Acta Paediatr. 1998;87:346.

5. Hook B, Hack M, Morrison S, et al. Pneumopericardium in very

low birthweight infants. J Perinatol. 1995;15(1):27.

6. Cabatu EE, Brown EG. Thoracic transillumination: aid in the

diagnosis and treatment of pneumopericardium. Pediatrics. 1979;

64:958.

7. Bjorklund L, Lindroth M, Malmgren N, et al. Spontaneous pneumopericardium in an otherwise healthy full-term newborn. Acta

Pediatr Scand. 1990;79:234.

8. Ramasethu J. Complications of vascular catheters in the neonatal

intensive care unit. Clin Perinatol. 2008;35:199.

9. van Engelenburg KC, Festen C. Cardiac tamponade: a rare but

life-threatening complication of central venous catheters in children. J Pediatr Surg. 1998;33:1822.

10. Fioravanti J, Buzzard CJ, Harris JP. Pericardial effusion and tamponade as a result of percutaneous silastic catheter use. Neonatal

Netw. 1998;17:39.

11. van Ditzhuyzen O, Ronayette D. Tamponnade cardiaque après

catheterisme veineux central chez un nouveaune. Arch Pediatr.

1996;3:463.

 

c. A decision will need to be made whether to leave the

cannula in place for any length of time or to remove

it once the pericardium has been drained. This decision will vary in individual cases, but factors to consider include the likelihood of reaccumulation and

Fig. 39.4. Insertion of needle/cannula attached to three-way

stopcock, in the subxiphoid space, directed toward the left

shoulder.

276 Section VII ■ Tube Replacement

the need for repeat drainage versus the risk of infection or entry of free air with an indwelling cannula.

d. In certain cases, the operator may elect to evacuate

the pericardial space directly through the needle,

rather than placing a cannula.

J. Special Circumstances

1. If ultrasound imaging is available, it may be helpful in

planning the needle entry site and angle, as well as

anticipating the distance required to reach the pericardial space (2,15,17,20,21).

2. If transillumination is positive for free air before the

procedure, it can be used to assess the adequacy of air

evacuation after the procedure and to look for evidence

of reaccumulation. Because pneumothorax and pneumomediastinum are potential complications, the availability of transillumination may also be helpful after the

procedure. Transillumination is not a reliable method

to rule out free air or to distinguish between pericardial

air and mediastinal air (5,6).

3. On initial aspiration of the pericardium, air, serous

fluid, serosanguineous or grossly bloody fluid, or fluid

resembling infusate from a central line (including

parenteral feeding fluids) (8,11) may be encountered.

Bloody fluid raises the concern that the needle may

have entered the heart. The following may be helpful

in distinguishing between pericardial fluid and intracardiac blood.

a. In an infant with tamponade, aspirating 10 mL of

blood from the heart will have minimal effect on the

acute hemodynamics, whereas draining as little as

5 to 15 mL from the pericardial space can result

in significant hemodynamic improvement within

30 seconds.

b. If ultrasound is being used, the pericardial fluid volume will appear to be decreased if the needle is correctly positioned. In some cases, one can reliably

identify the needle in the pericardial space (Fig.

39.5) (15).

c. Placing a few drops on a gauze swab may help distinguish the two sources, because serosanguineous

fluid will separate into a central dark red zone and a

more serous peripheral zone, but this can take several minutes.

d. Alternatively, a spun hematocrit can be performed

rapidly if the unit has a readily available centrifuge;

this also takes a few minutes.

RA

RV

LV

LA

Tip of pericardiocentesis needle,

with effusion partially drained and

right ventricle better expanded.

C

Pericardiocentesis needle

entering pericardial space

B

RV

* - Pericardial effusion, RV - right ventricle,

LV - left ventricle

LV

A

Fig. 39.5. Echocardiogram images of pericardiocentesis.

A: Echocardiogram image of pericardial effusion. B: Tip of

needle in pericardial space. C: Pericardial effusion partially

drained.

 

Chapter 39 ■ Pericardiocentesis 275

3. Swabs or gauze pads

4. Gloves

5. Local anesthetic

6. 16- to 20-gauge IV cannula over 1- to 2-inch needle

7. Indwelling drainage catheter (optional)

8. Three-way stopcock

9. Short IV extension tubing (optional)

10. 10- to 20-mL syringes

11. Preassembled closed drainage system as for emergency

evacuation of air leaks, thoracostomy tubes described in

Chapter 38 (optional)

12. Connecting tubing and underwater seal for indwelling

drain (optional)

13. Specimen containers for laboratory studies, if procedure is diagnostic

Nonsterile (See also I)

1. Transillumination device (optional, for pneumopericardium)

2. Echocardiogram/sonography imaging device (optional

in urgent situations)

I. Procedure

1. If ultrasound/echocardiographic imaging is available,

and if time permits, imaging can be performed to determine an optimal needle entry site and angle. In addition, the approximate distance required to reach the

pericardial space can be estimated (15). Even after a

sterile field is created, ultrasound imaging can be performed from a nonsterile area of the chest to monitor

the effusion during the procedure. If imaging is done

from a part of the sterile field, the transducer can

be placed in a sterile sheath (or a sterile glove). Care

should be taken to avoid moving a probe with sterile cover back and forth between sterile and nonsterile

areas.

2. Similarly, evaluation with transillumination can be performed in cases of pneumopericardium, if time permits.

3. Cleanse skin over xiphoid, precordium, and epigastric

area with antiseptic. Allow to dry.

4. Arrange sterile drapes, leaving the subxiphoid area

exposed.

5. Administer local anesthesia if the patient is conscious.

For example, 0.25 to 1 mL of subcutaneous 1% lidocaine instilled within 1 to 2 cm of the xiphoid process.

(See also Chapter 6.)

6. Form a closed system by assembling a syringe, threeway stopcock, and extension tubing so that the stopcock

is open to both the syringe and the extension tubing,

but closed to the remaining side-port .

7. Using the IV needle/cannula, enter the skin 0.5 to 1 cm

below the tip of the xiphoid process, in the midline or

slightly (0.5 cm) to the left of the midline. The needle

should be at a 30- to 40-degree angle to the skin, and

the tip should be directed toward the left shoulder

(Fig. 39.4). A different approach may be used in certain

cases, for example, if an echocardiogram suggests that

most of the fluid is right-sided or apical.

8. Advance the needle until air or fluid is obtained.

a. A rhythmic tug, corresponding to the heart rate, may

be felt as the needle enters the pericardium.

b. If ultrasound imaging is available, needle position

can be determined either by visualizing the tip of

the needle within the pericardial space or by demonstrating that the amount of pericardial fluid is

diminishing as fluid is aspirated (Fig. 39.5). Some

authors have described reinfusing a small amount of

the aspirated fluid while imaging to observe the

location of microcavitation echoes (15,20,21).

9. Fix the needle in position and advance the cannula

over the needle into the pericardial space. Remove the

needle, and connect the cannula to the closed system

syringe for aspiration.

10. Aspirate as much fluid/air as possible. If the syringe fills,

use the third port of the stopcock to empty the syringe,

or to attach a second syringe, and then aspirate more,

repeating as needed. If diagnostic studies are desired,

the fluid should be transferred to appropriate specimen

containers.

a. If bloody fluid is aspirated, there could be a serosanguineous or hemorrhagic effusion, or the needle

might have entered the heart (usually the right ventricle). There are a few clues that can be helpful in

determining whether the needle has entered the

heart (see J).

b. Note that small single-lumen catheters may easily

become blocked.