Aseptic Techniques

SECTION IV

Aseptic Technique Needles and Syringes

© 1999 Canadian Pharmacists Association and Canadian Society of Hospital Pharmacists

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Needles and Syringes Key Points shaft

When handling needles and syringes inside a laminar airflow hood, always follow the two basic principles: hub

Always use the “no touch” technique – never touch any critical site. Do not interrupt or obstruct the flow of air between the HEPA filter and exposed critical sites.

Work at least six inches inside the hood and above the work surface. In a vertical hood, work inside, not over, the air intake grill. Perform all critical site manipulations with your hands kept downstream from the critical site. Your hands should never obstruct airflow from the HEPA filter over the critical site.

Needles A disposable needle (Figure 4.1) is made of a metal shaft with a plastic hub and is used for the transfer of liquid from one drug package to another. It is also used to administer drugs to patients by various routes (e.g., intravenous, intramuscular, subcutaneous). The hub is the attachment point of the needle to the syringe; these are generally colour coded to reflect gauge sizes. The bevel is a slant at the tip of the needle shaft and the point is the bevel tip. The bevel heel is the opposite end of the slant. Only disposable needles are used when preparing admixtures. Needle size is designated by length and gauge (G). The length of a needle is measured from the juncture of the hub and shaft to the tip of the bevel. The gauge of the needle is a measure of the outside diameter of the shaft. Gauges generally range from 14 G to 28 G. The finer the needle, the higher the gauge number (e.g., 28 G). The choice of needle size is determined mainly by the viscosity of the liquid being transferred and the nature of the rubber closure being penetrated. Viscous

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bevel tip

bevel heel

Figure 4.1: Needle

liquids flow more easily through a coarse needle (e.g., 18 G). An 18, 20 or 21 G needle is used most commonly in the preparation of aseptic products. Needles designated as “thin-wall” are available and offer the advantage of a larger lumen for a given outside diameter. Needles may be coated with a silicone lubricant for ease of penetration and, therefore, should never be swapped with alcohol. A general rule of thumb used in many pharmacies is that a needle may be used for a maximum of five punctures before being discarded.

Syringes A syringe (Figure 4.2) is a plastic or glass device used to transfer solution from one container to another and to administer drugs to patients. A syringe has two components, a barrel and a plunger. The plunger fits inside the barrel and has a flat disk or lip at one end and a rubber piston at the other. The top collar of the syringe barrel pre vents the syringe from slipping during manipulation. The tip of the barrel is where the needle attaches. The design of the syringe tip is either a tapered (slip-fit) or luer-lock type (Figure 4.3). The needle is pushed onto a tapered tip and twisted onto the locking mechanism of a luer-lock tip. Syringes are available in numerous sizes, ranging from 0.5 to 60 mL. Graduated lines marked on the barrel indicate the specific volumes that the syringe can hold. Usually, the larger the syringe capacity, the longer the interval between


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ASEPTIC TECHNIQUE — NEEDLES AND SYRINGES

calibration lines. For maximum accuracy, use the smallest syringe that can hold the required volume.

the needle hub. For needles with a plastic covering, twist off the end covering the hub. While holding the needle (in its protective package) in one hand, attach the needle to the syringe held in the other hand, making sure to keep your fingers well back from where the needle attaches to the syringe (Figure 4.4). For luer-lock syringes, attach the needle to the syringe by gently twisting the syringe barrel clockwise until the needle is tightly attached. For a tapered or slip-fit syringe, push the needle onto the end of the syringe until it is tight.

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collar

luer-lock tip

barrel

plunger lip

plunger piston

Figure 4.2: Syringe

Figure 4.3: Syringe tips — luer-lock and slip-fit

Figure 4.4: Attaching a needle to a syringe

Plastic disposable syringes are used almost exclusively to prepare admixtures. Glass syringes may be used if the medication is known to react with plastic or if the drug is to be stored in the syringe for a period of time and information is available only for storage in glass. Do not let your hands obstruct the airflow passing over the needle and syringe at any time during assembly or use.

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Remove the needle packaging and discard.

Assemble the needle and syringe prior to opening ampoules or vials to lessen the exposure time of the drug. The syringe with needle attached may be placed on the work surface as long as the needle guard is in place.

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While attaching the needle, keep your fingers well back from the point of attachment of the needle and syringe.

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If at any time you touch the needle shaft or hub, it must be discarded, as it has become contaminated. The same applies if you touch the hub or plunger of the syringe.

Removing the Needle Guard

Always keep the needle guard in place until the needle is to be used.

Attaching a Needle to a Syringe To attach a needle to a syringe: s

Select the size of needle that is appropriate for the procedure.

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Unwrap paper-covered needles by peeling apart the sides of the package just enough to expose

To remove the needle guard, use your non-dominant hand to grip the guard between your thumb and index finger, or between your fourth and fifth fingers, and pull away from the syringe in a straight line (Figures 4.5 and 4.6). If the needle is to be reused, protect the guard from contamination by keeping it between your fourth and fifth fingers or setting it on an alcohol swab. Always position the guard so that the opening is facing the direct airflow. If the needle is not to be reused, the needle guard may be placed on the work tray during aseptic manipulations.


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Moving the Plunger of a Syringe When pulling back the plunger, the fingers should not come into contact with any part of the plunger except the flat lip at the end. The body of the plunger must not be touched. Contamination of the medication may occur if the plunger is allowed to come into contact with any surface.

Figure 4.5: Removal of needle guard (gripping guard with thumb and forefinger)

There are two methods to move the plunger of a syringe: the two-hand method of adjusting the plunger of a syringe and the one-hand method of adjusting the plunger of a syringe (Figures 4.7 and 4.8). Figure 4.7: Two-hand method of adjusting the plunger of a syringe

Figure 4.6: Removal of needle guard (gripping guard between fourth and fifth fingers)

Removing a Needle from a Syringe To remove the needle from a syringe, first recap the needle (see Recapping Needles). For luer-lock syringes, twist the needle counter-clockwise while pulling slightly until the needle releases from the syringe. For tapered or slip-fit syringes, simply pull the needle straight away from the syringe. Venting needles need not be recapped before discarding. If the needle will not be reused, discard it in the sharps container. Discard the needle and syringe separately in their respective disposal containers within the hood. It is critical that no part of the needle be touched and that the protective guard be left in place when the needle/syringe is not in use.

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Figure 4.8: One-hand method of adjusting the plunger of a syringe


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Recapping Needles Be careful not to puncture yourself when recapping the needle. The needle must be guided down the centre of the guard to avoid puncturing the guard.

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For ampoules, withdraw the needle and replace the needle guard. If withdrawing from a vial, leave the needle in the vial when removing bubbles.

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Hold the syringe vertically (needle pointing upwards) and tap it on the barrel with the fingers of the opposite hand until all the bubbles float to the top (Figures 4.10, a to d).

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If air bubbles adhering to the sides of the syringe cannot be tapped free, draw a large air bubble into the syringe, then hold the syringe in a horizontal position and rotate the syringe using the large air bubble to collect smaller ones. Return the syringe to the upright position and tap the barrel until all air bubbles float to the top.

To recap the needle: s

Hold the needle guard in your non-dominant hand and the syringe barrel in your dominant hand.

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Carefully slide the guard onto the needle, being careful not to puncture the guard or yourself.

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One specific method to recap the needle is to hold the needle guard between the fourth and fifth fingers of the non-dominant hand (Figure 4.9). Hold the guard vertically while approaching with the syringe at a 90-degree angle to the guard. Rotate the syringe to the upright position and carefully slide the needle down into the guard.

Figure 4.10: Removing air bubbles Figure 4.10a: Tapping the syringe with the fingers of an open hand

Figure 4.10b: Using knuckles Figure 4.9: Needle guard replacement

Removing Air Bubbles from a Syringe Air bubbles are a common problem when withdrawing medication from an ampoule or vial. Bubbles prevent accurate measurement of the volume of solution in the syringe. To remove air bubbles: s

Draw the plunger back slightly to prevent any fluid from escaping from the tip of the needle and to bring excess air into the syringe.


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1 ml

1

Plunger piston Final edge of plunger piston

1.5 ml

2 ml

Figure 4.10c: Using a flick of the finger

Figure 4.10d: Tapping with the side of the index finger

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Figure 4.11: Alignment of the syringe plunger to 1.5 mL

Adjusting the Volume in a Syringe To obtain an accurate measurement of solution: s

Expel the air from the syringe once all the bubbles have been removed. Slowly push in on the plunger until the fluid reaches the level of the needle tip. For vials, the needle should remain in the vial when adjusting the volume.

Adjust the plunger to obtain the correct volume of fluid by aligning the leading or final edge of the piston (i.e., closest to the tip of the syringe) with the appropriate graduation mark on the barrel (Figures 4.11, 4.12 and 4.13).

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If there is too little fluid, draw more into the syringe and repeat the process. If too much fluid is present, expel the excess into the original container.

Figure 4.12: Alignment of the syringe plunger to 1.5 mL

Figure 4.13: Alignment of the syringe plunger to 15 mL

Never squirt the excess fluid toward the HEPA filter.

Practice Exercise s

Collect supplies: 3-4 different sizes of syringes, both luer-lock and slip-fit, if available (e.g., 1 mL, 10 mL, 20 mL, 60 mL), different needle sizes, bag of IV solution.

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Practice: follow the steps outlined to aseptically assemble the needle and syringe, remove/replace the needle guard and remove the needle from the syringe. Practice drawing up solution from the IV bag, removing air bubbles and adjusting the volume. Note the graduated lines on the syringes and the hub colours and sizes of the various needles.

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Aseptic Techniques

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