Indications and Contraindications

Capillary blood sampling is frequently used to obtain blood samples from young infants. In infants, the heel is the most common location for capillary blood sampling, whereas in older children and adults, blood samples are more commonly obtained from the finger, toe, or earlobe. This technique is useful when repeated measurements such as blood glucose or serial hemoglobin are needed. It is also an option for obtaining “arterialized” blood for blood gas analysis when arterial access is unavailable, such as in chronically ill neonates and young infants or when the clinician is not comfortable obtaining a percutaneous arterial blood sample. If a sufficient volume is obtained, blood from a capillary sample can also be sent for other routine laboratory studies. Do not send this type of specimen for blood culture because of the risk for contamination. Heel sticks are more painful than venipuncture but are useful in the event of difficult access or when arterialized samples are needed.⁴

Avoid sampling from an area of local inflammation or hematoma. Avoid repetitive sampling from the same site because it may induce inflammation and subsequent scarring. In general, heel stick sampling is not ideal for blood gas analysis when the infant is hypotensive, the heel is markedly bruised, or there is evidence of peripheral vasoconstriction.

Equipment and Setup (Box 19-1)

Use a 3-mm lancet (Becton-Dickinson, Rutherford, NJ) or an automated disposable incision device (e.g., Tenderfoot, Surgicutt) to perform this procedure. Perform blood collection with either heparinized capillary tubes or 1-mL Microtainer tubes with a collector attachment (Becton-Dickinson, Rutherford, NJ).

Technique

The heel stick method of capillary blood sampling will be described, but capillary blood samples can also be obtained from a finger, toe, or earlobe (Fig. 19-1). To avoid penetration of the calcaneus and the risk for osteochondritis, puncture only the most medial and lateral portions of the plantar surface of the heel.⁵ Some research suggests that when using automated lancets, any site on the heel can be safely punctured in a term neonate.⁶ Prewarm the foot for 5 minutes to produce hyperemia and enhance blood flow. Immobilize the foot in a dependent position with one hand. First cleanse the heel with antiseptic solution and allow it to dry. Next, puncture the skin with the lancet. Allow the alcohol to dry to avoid false elevations in the glucose level. Avoid squeezing the foot because it may inhibit capillary filling and actually decrease the flow of blood. Furthermore, squeezing may lead to hemolysis and make analysis less accurate. If blood does not flow freely, another puncture may be required.

Wipe away the first small drop of blood with gauze and allow a second drop to form. Place a heparinized capillary tube in the drop of blood and invert the proximal end of the tube to allow it to fill by capillary action. Fill the capillary tube until blood reaches the demarcation line on the tube. Overfilling or underfilling may result in clotting or erroneous test results. If 1-mL Microtainer tubes are used, hold the tube at an angle of 30 to 45 degrees from the surface of the puncture site. Touch the collector end of the tube to the drop of blood and allow the blood to drain into the tube. Gently tap the tube to facilitate flow to the bottom. Once filled, seal the tube with the accompanying cap. After an adequate specimen is obtained, apply a dry dressing to the puncture site.

When a heel stick is performed for an arterialized blood sample, use a technique that is similar to that discussed previously for routine blood sampling, with the following differences. Wrap the infant’s foot in a warm towel for a few minutes and discard the first drop of blood while allowing the remaining blood to flow freely into a heparinized capillary tube. Place the tip of the tube as near the puncture site as possible to minimize exposure of the blood to environmental oxygen. Fill the tube as completely as possible. Avoid collecting air in the tube and excessive squeezing of the foot because this may artificially lower Po₂. When the tube is full, occlude the free end with the gloved finger to prevent the entry of air, and cap both ends.

Complications

When performed properly, heel sticks are associated with a low incidence of complications. Use a proper incision device to prevent lacerations. Rare complications include infection, scarring, and calcified nodules.⁷

Interpretation

Multiple studies have demonstrated a good correlation between arterial and capillary specimens for determining pH and Pco₂ in hemodynamically stable patients.8,9 However, determination of Po₂ is not reliable when performed on blood obtained by capillary sampling.

Indications and Contraindications

Although many laboratory tests for small infants may be performed on blood obtained by heel stick, larger volumes of blood may be required, which makes heel sticks impractical. Use venipuncture to obtain larger quantities of blood from infants and children and to obtain blood for culture. When collecting blood for culture, prepare the area of venipuncture with an appropriate antiseptic solution and allow the skin to dry. The blood culture collection bottle will probably indicate a desired volume of sample for optimal results, but 1 mL of blood is generally acceptable for a small infant. Wash off the cleanser promptly after blood has been collected because iodine solutions and other detergents can irritate infant skin.

Equipment and Setup (Box 19-2)

A small-gauge butterfly needle and syringe are usually preferred over a needle and syringe for obtaining blood from infants and young children. It is easier to control the position and to suction with a butterfly needle and syringe. If other access is not available, the butterfly needle may also serve as an infusion line after an adequate amount of blood is obtained. A 23-gauge butterfly needle will generally suffice for venipuncture, regardless of the age group. In older children and adolescents, a straight needle and syringe or the Vacutainer system (Becton-Dickinson, Rutherford, NJ) can be used more easily than in infants. However, the negative pressure within the evacuated blood tube may be sufficient to collapse the punctured vein. Use a 3- or 5-mL syringe because it is less likely than a 10-mL syringe to cause vein collapse in small children.

Technique

As in adults, the usual site for venipuncture in infants and children is the antecubital fossa. However, any reasonably accessible or easily visible peripheral vein may be used, such as those on the hands, feet, or scalp for very small infants (Fig. 19-2). Veins on the dorsum of the hand can be used, provided that they will not be needed for IV cannulation. The external jugular and femoral veins or arterial sites are rarely needed for routine samples in a stable patient. Imaging devices (e.g., ultrasound, transillumination, or infrared devices) may also be used to locate and identify veins for IV catheter placement. These devices are discussed later in this chapter (see “Vascular Line Placement: Venous and Arterial”).

Assemble all necessary equipment and make sure that everything is ready for immediate use. Ask an assistant to help immobilize the patient when drawing blood from infants and small children. Assemble the equipment, especially needles, out of sight of the child. If an extremity vein is to be used, apply a tourniquet proximal to the selected vein. In small infants, a rubber band can be used as a tourniquet. Be sure that the tourniquet is not so tight that it impedes arterial filling. It is absolutely essential that the tourniquet be removed after the procedure.

Cleanse the area surrounding the chosen site of skin penetration with antiseptic solution and allow it to dry. Apply slight distal traction to the skin to immobilize the vein. Insert the needle quickly through the skin and advance it slowly into the vein at an angle of approximately 30 degrees with the bevel facing up (Fig. 19-3, step 1). Successful vessel penetration is heralded by a flashback, or flow, of blood into the butterfly tubing. Apply gentle suction by slowly withdrawing the plunger of the syringe. If the required amount of blood is greater than the capacity of the attached syringe, pinch off the tubing, remove the filled syringe, attach a new syringe, and apply gentle suction again after releasing the pinched tubing. After the required amount of blood is withdrawn, remove the needle and apply a sterile dressing and direct pressure to the puncture site.

Apply suction with a Vacutainer system in which the needle punctures the sealed end of the butterfly device (see Fig. 19-3, step 2). There are also butterfly systems available with a second needle that is occluded by a rubber shield located at the opposite end of the butterfly tubing. Once the vein has been entered, the needle at the opposite end of the butterfly tubing is pushed through the top of the vacuum-sealed tube. In either case, if the suction is excessive, the vein will collapse and blood flow will stop.

Although peripheral sites for venous blood sampling are preferable in infants, the external jugular and femoral veins may also be used for venipuncture during resuscitation or when peripheral sites are inadequate. The external jugular vein lies in a line from the angle of the jaw to the middle of the clavicle and is usually visible on the surface of the skin (Fig. 19-4). When the infant is crying, this vein is more prominent. Ask an assistant to restrain the infant in a supine position with the head and neck extended over the edge of the bed. Alternatively, place a towel roll or pillow under the child’s shoulders. Turn the head approximately 40 to 70 degrees from the midline. Cleanse the skin surrounding the area to be punctured with alcohol or another antiseptic solution. Apply finger pressure just above the clavicle to help distend the jugular vein. Use a 21- to 25-gauge straight needle or a 21- to 25-gauge butterfly needle attached to a syringe. Puncture the skin and then advance the needle slowly until the jugular vein is entered and a flashback of blood is observed. Keep the syringe connected to the needle at all times to maintain constant negative pressure and avoid air embolism. After the appropriate amount of blood is obtained, withdraw the needle and apply slight pressure to the vessel. Place the infant in an upright position after the needle is removed, and hold pressure over the puncture site for 3 to 5 minutes. Observe the puncture site closely afterward to identify persistent bleeding.

In most patients, the femoral vein lies medial to the femoral artery and inferior to the inguinal ligament (Fig. 19-5A). Ask an assistant to position the patient’s hips in mild abduction and extension while you palpate the artery. Identify its location by placing a mark on the skin just superior to the femoral triangle. If available, use ultrasound to assess the position of the femoral vessels. Prepare the femoral triangle with alcohol or another antiseptic agent. Use a povidone-iodine or chlorhexidine scrub when obtaining blood for culture. Use a technique of needle insertion that is similar to that for external jugular venipuncture (see Fig. 19-4). Puncture the skin and then direct the needle or catheter toward the umbilicus at a 30- to 45-degree angle to the skin and just medial to the pulsation of the femoral artery (see Fig. 19-5B). Apply slight negative pressure constantly throughout insertion. After the needle enters the femoral vein, withdraw the desired blood samples. Afterward, remove the needle or catheter unless an IV catheter for venous access is desired in this location. Apply pressure over the puncture site in the femoral triangle for a minimum of 5 minutes. Observe closely for recurrent bleeding.

Scalp veins can be very useful for venous sampling in small infants when other options are not possible or readily available.¹⁰ The anatomic considerations and technique are discussed later (see “Peripheral Venous Catheterization: Percutaneous” and “Peripheral Venous Catheterization: Venous Cutdown”).

Complications

Complications of venipuncture include hematoma formation, local infection, injury to adjacent structures (e.g., vessels), and phlebitis. These complications are all uncommon. Use special care when attempting to puncture the external jugular or femoral vein. Inadvertent deep puncture in the neck can injure the carotid artery, the vagus nerve, the phrenic nerve, or the apex of the lung. The femoral artery or nerve can be injured during puncture of the area around the femoral triangle. Fortunately, these injuries are unlikely when proper technique is used.

Indications and Contraindications

Arterial blood gas analysis provides useful and important information for evaluating the respiratory status and acid-base equilibrium in infants or children with respiratory distress or metabolic derangements. Use arterial blood for routine laboratory analysis or blood culture if venous blood is difficult to obtain. Potential sites for arterial blood sampling include the radial, brachial, dorsalis pedis, posterior tibial, and, in newborn infants, the umbilical arteries.

The radial artery has several advantages that make it the most commonly used artery for blood sampling. First, its location makes it easy to palpate and puncture (Fig. 19-6A). The ulnar artery is more difficult to locate. Second, no vein or nerve is immediately adjacent to the radial artery, which minimizes the risk of obtaining venous blood or damaging a nerve. Another advantage of the radial artery is the presence of good collateral circulation from the ulnar artery. The brachial artery has little collateral circulation and should be avoided unless no other options are available.¹¹ Limit use of the ulnar artery to preserve collateral circulation to the hand. As a general rule, do not use the femoral artery for obtaining routine blood samples.

Avoid puncture of an artery if the overlying skin is infected, burned, or otherwise damaged. Also, consider the presence of adequate collateral circulation and any potential coagulation disorders.

Equipment and Setup (Box 19-3)

For arterial puncture in infants and children, a small-gauge butterfly needle is preferable to a needle and syringe. As for venipuncture, a 23-gauge butterfly needle is used most often, although a 25-gauge butterfly needle may be better in newborns. Some clinicians prefer to use a 25-gauge needle connected to a syringe, but a butterfly allows better control of the needle while an assistant aspirates the syringe. This technique may also permit a larger volume of blood to be withdrawn.

Technique

The radial artery is the one most frequently used vessels to obtain intermittent arterial samples, so the technique for arterial puncture at this site will be described. (See also Chapter 20 for a discussion of the Allen test and the effect of heparin on arterial blood sampling.)

Hold the infant’s wrist and hand in your nondominant hand (see Fig. 19-6B). Hold the hand fully supinated with the wrist slightly extended (i.e., dorsiflexed). Palpate the arterial pulsation just proximal to the transverse wrist creases. Do not overextend the wrist because this can cause loss of the arterial pulse during palpation. Make a small indentation in the skin with a fingernail to mark the insertion site. Cleanse the area with antiseptic and allow the skin to dry. The topical anesthetic options discussed previously may be used if the clinical situation permits. Penetrate the skin at a 30- to 45-degree angle. While the plunger of the syringe is gently withdrawn by an assistant, advance the needle slowly until the radial artery is punctured or resistance (bone) is met (Fig. 19-7). In contrast to performing the procedure in adults, provide continuous, but gentle suction with the plunger of the syringe in infants. Pulsating or rapidly flowing blood that appears in the hub of the needle is a good indication that the radial artery has been punctured. Some clinicians prefer to attach the syringe to the butterfly needle only after blood return is noted. Suction can be applied afterward.

If resistance is met while pushing the needle deeper, withdraw the needle slowly since both walls of the artery may have been punctured but the tip may reenter the lumen on withdrawal. If no blood returns, withdraw the needle slowly to the point at which only the distal tip of the needle remains beneath the skin. Repeat the procedure after checking the location of the pulse. Reorient the needle slightly more laterally or medially if necessary. After the desired amount of blood is obtained, remove the needle and apply pressure for 5 minutes or longer to control the bleeding.

Complications

Complications of radial artery puncture include infection, hematoma formation, arterial spasm, tendon injury, and nerve damage.12,13 With proper technique, however, the complication rate is extremely low. If the infant starts to cry before blood is obtained, the Po₂ and Pco₂ values may not reflect the infant’s true steady state.

Indications and Contraindications

In general, peripheral IV lines are indicated when the patient is unable to attain medical and nutritional goals with enteral therapy. These lines provide fluids for resuscitation and maintenance and access for the administration of medications.

Equipment and Setup (Box 19-4)

Over-the-needle catheters such as the Angiocath, Medicut, or Quikcath are the mainstay of peripheral venous catheterization. These thin-walled, flexible catheters range in size from 14 to 24 gauge. Select the appropriate gauge and length of the catheter based on the size of the child and the clinical situation. Larger-diameter catheters allow more rapid administration of fluids in emergency situations, but large catheters may decrease the success of cannulation in young children with small veins. In general, use the smallest-gauge catheter that is appropriate for the clinical situation. For infants, a 22- to 24-gauge catheter is generally appropriate.

Use a T-connector extension tubing connected to the catheter after insertion to facilitate withdrawal of blood for specimen collection. This device makes flushing the catheter and maintaining patency easier (especially while taping and securing the IV line). It also allows dressing changes without disturbing the IV insertion site. In recent years, traditional catheters have been replaced with similar over-the-needle catheters that have a protective cap into which the needle is retracted after cannulation to reduce needlestick injuries.

Use either a homemade or commercially available device to protect the IV site from a child’s attempts to remove the line. An arm or leg board appropriate for the size of the child should be handy to provide stabilization of the extremity after insertion. In newborns or small infants, fashion an arm board from two tongue depressors taped together and covered with a 4- × 4-inch piece of gauze to provide the length needed. Keep an IV fluid chamber with microdrip tubing and a continuous infusion pump nearby, primed, and ready to use. Monitor fluid administration in an infant very carefully. Do not use macrodrip tubing or liter bags because they can result in the inadvertent infusion of large amounts of fluid in an infant. An infusion pump is an ideal way of limiting fluid infusion while keeping the vein open.

Vein Imaging Devices

A variety of imaging modalities, including ultrasound, transillumination, and infrared technologies, have been used to help locate peripheral veins for cannulation. In adults there are data supporting the use of ultrasound to facilitate peripheral vein cannulation in those with difficult access.14,15 However, the use of ultrasound to aid in the placement of peripheral IV lines in pediatric patients is not common practice. One recently published study demonstrated that ultrasound could be used to detect peripheral veins in young children that were not “clinically apparent” (nonvisible and nonpalpable).¹⁶ The study also found that lack of ultrasound visualization increased the chance of unsuccessful placement.¹⁶ Other small studies have shown mixed results, and further research is needed.^17–19

Some emergency departments (EDs) use transillumination devices commonly found in neonatal intensive care units to assist in finding veins in infants.20,21 The Venoscope II (Venoscope LLC, Lafayatte, LA) and the Neonatal Transilluminator (Graykon Scientific, Victoria, Australia) are two such devices that work by projecting a high-intensity light into the patient’s subcutaneous tissue. The light causes the veins to contrast with the surrounding tissue, which makes them easier to locate.²²

A newer vein imaging technology, VeinViewer (Luminetx Corp., Memphis, TN) uses near-infrared technology to project an enhanced image of the subcutaneous veins onto the patient’s skin. Theoretically, knowledge of the location of the venous valves and the course of the vessel can assist the clinician in selecting the best area to be cannulated.²³ Early small studies have not demonstrated improved overall success rates in obtaining IV access, but the technology may be useful in patients with difficult IV access.^24–26

Technique

A number of IV sites are available for placement of a peripheral IV line in an infant (see Fig. 19-2). The most common sites chosen for IV insertion in infants and children are the superficial veins of the dorsum of the hand, the antecubital fossa, the dorsum of the foot, and the scalp (in newborns and small infants). The veins of the dorsum of the hand are the vessels most frequently used. Because these veins are relatively straight and lie flat on the metacarpals, they are easily stabilized. If the hand is chosen, take the child’s age and hand preference into consideration. Avoid placing an IV line in a hand used for thumb sucking whenever possible. Veins in the antecubital fossa (cephalic and basilic veins) are easily accessible; however, the angulation across the fossa makes advancement of the catheter difficult. These veins may not be easily visible and yet may be palpable. Select the most distal vein that is large enough to accommodate the catheter and leave the larger, more proximal veins in case the initial attempts are unsuccessful or if prolonged IV therapy is needed and percutaneous central venous catheter placement (e.g., a peripherally inserted central catheter line) is being contemplated. Tributaries of the dorsal venous arch on the dorsum of the foot, like those on the dorsum of the hand, are relatively straight, and the extremity is easily immobilized after insertion. Because indwelling catheters in this location prevent mobility, consider using this site only in preambulatory patients or after attempts at other sites have been unsuccessful. The scalp veins are easy to cannulate, but their use is primarily limited to very small infants. If a peripheral vein on the hands, feet, or antecubital fossa is being used, immobilize the extremity first by taping it to an arm board, a padded splint, or a commercially available immobilization device. The particular site is a matter of preference, so choose the vein that appears to be the easiest to cannulate.

With few exceptions, the same techniques used for IV insertion in adults may be used in infants and children, especially in the veins of the distal ends of the extremities. If the peripheral end of an extremity is used, place a tourniquet proximal to the planned site of entry. Warm the extremity to induce vasodilation in the surface veins, which makes them easier to cannulate. Flush the tubing of the T-extension set before venipuncture with a sterile IV solution, such as normal saline (NS), to prevent air embolism. Direct the IV catheter through the skin at a 10- to 20-degree angle and slowly advance it until blood return is noted (Fig. 19-8, step 1). Next, advance the catheter over the needle and into the vein. Retract the needle and connect the IV line to the hub of the catheter by means of a T-extension set (see Fig. 19-8, step 2). After 1 mL of saline has been flushed through the line, inspect the site for signs of infiltration, such as hematoma or local swelling.

Fix the catheter to the skin with a 0.5-inch piece of tape passed over the catheter hub and skin. Place a second piece of tape adhesive side up and slip it under the catheter hub. Cross it over the catheter hub in a V shape (Fig. 19-8, step 2). After securing the catheter with tape, cover the entire area with a transparent sterile dressing such as Tegaderm (3M, St. Paul, MN) or OP Site (Smith and Nephew Medical, Massillon, OH). Loop back the tubing of the T-extension set, place a piece of tape midway over the tubing, and secure it to the skin. This ensures that the IV tubing will not be accidentally dislodged if is suddenly pulled. Securely tape the hand and forearm to an arm board for immobilization (see Fig. 19-8, step 3). Occasionally, the flow rate of the infusion may depend on the position of the catheter, especially if the catheter spans a joint or the tip abuts a venous valve. Adjust the hand position or catheter with strategically placed sterile gauze or withdraw the catheter slightly to remedy the problem.

Obtain blood specimens just after IV insertion. If the IV line has been flushed, the initial blood draw will be diluted. To prevent dilution, withdraw 5 mL of blood from the catheter before collecting the samples. This 5 mL of “waste” can be either discarded or reinstilled into the patient. Next, remove the syringe. Connect the T-extension tubing to the IV infusion tubing, and set the infusion pump at the desired rate. Send blood for culture only if the skin was cleaned with an appropriate antiseptic before insertion of the IV catheter.

If the scalp veins are used, trim the hair in the surrounding area to expose the vessels. To differentiate between arteries and veins on the scalp, arteries are usually more tortuous than veins.¹⁰ If an artery is entered during placement of the needle and fluid is infused, blanching will occur in the area. If this happens, remove the IV catheter, maintain slight pressure for 5 minutes, and repeat the procedure at another site. A rubber band may be used as a tourniquet around the scalp to produce venous dilation, but it is rarely required. Place a piece of tape on the rubber band before placement on the scalp to facilitate lifting the rubber band away from the scalp.

If a scalp vein butterfly infusion set is used, grasp the wings of the butterfly between the thumb and forefinger and introduce the needle beneath the skin approximately 0.5 cm distal to the anticipated site of vein entrance (Fig. 19-9, step 1). Advance the needle slowly toward the vessel until blood appears in the tubing, which indicates that the vessel has been entered. Next, remove the tourniquet. Flush the needle with 0.5 to 2 mL of IV fluid, such as NS, to ensure that the needle is properly in place within the vein. If infiltration occurs, as noted by a subcutaneous bump, remove the IV line and repeat the process at another site.

After the wings are secured, tape the tubing of the butterfly set in a loop on the scalp so that it is not pulled inadvertently. Place a wisp of cotton under the wings of the butterfly if the flow rate of the infusion is affected by the position of the catheter. Tape a small medication cup over the wings and the needle to protect the IV line (see Fig. 19-9, step 2). Connect the tubing of the butterfly set to the tubing from the IV system. It is generally preferable to use standard over-the-needle IV catheters whenever possible, whether for extremity or scalp IV lines, because they are less likely to infiltrate and will last longer. However, a small butterfly needle that can be inserted temporarily until additional access is possible is sometimes the only option short of IO access.

Complications

Complications of peripheral IV lines and IV fluid therapy include infection, phlebitis, inadvertent arterial puncture, injection of sclerosing agents into the subcutaneous space with resultant necrosis and sloughing of the skin (especially in small infants), air embolism, and administration of inappropriate volumes of fluid. Because the life span of an IV needle or catheter is usually fairly short (<72 hours) in a small infant, the decision concerning elective removal and replacement of the IV system is not usually a problem. Of course, it is important to pay meticulous attention to antiseptic procedures during insertion and maintenance of the IV system to decrease the risk for infection.

Indications and Contraindications

With the development of small IV catheters and the rapidity and safety of IO needle placement for emergency access (Chapter 25), peripheral venous cutdown is rarely performed in the ED. Even in experienced hands a saphenous vein cutdown may take more than 10 minutes and is associated with a higher rate of infection than other routes of vascular access are.²⁸ Nevertheless, if peripheral venous, central venous, or IO access cannot be obtained, venous cutdown may provide an alternative means of emergency venous access. For the purpose of illustration, exposure and cannulation of the saphenous vein will be discussed (Fig. 19-10). The same principles apply when cutdown is performed on most peripheral veins.

Equipment and Setup (Box 19-5)