Chapter outline

Infiltrated Lidocaine

Lidocaine 1% to 2% is the local anesthetic of choice when administered by infiltration at the site prior to painful procedures, ranging from IV starts to skin suturing, because it has a fast onset and can be administered in a wide range of doses with minimal risk of toxicity (Pasero, Wong, 1997). The onset of analgesia is rapid (i.e., within 2 minutes), and anesthesia lasts 1.5 to 2 hours (Achar, Kundu, 2002; Strichartz, Berde, 2005). The maximum recommended adult dose is 4 mg/kg, not to exceed 280 mg (Achar, Kundu, 2002).

Research shows that many patients fear dermal procedures, particularly venipuncture and IV catheter placement (Windle, Kwan, Warwick, et al., 2006). Lidocaine 1% given intradermally to anesthetize the site prior to venous or arterial puncture is an inexpensive, easy, and effective way of addressing this fear by minimizing the associated pain (see Figure 24-1 on p. 685 for intradermal site of action). All state boards of nursing in the United States approve this nursing function, and the Infusion Nurses Society Standards of Practice call for the nurse to consider providing local anesthesia prior to venipuncture (Infusion Nurses Society, 2006). Despite this, nurses, who perform a large number of venipunctures, rarely use local anesthetic even though they would prefer a local anesthetic if they were to undergo this type of procedure (Valero Marco, Martinez Castillo, Macia Solera, 2008). A lack of knowledge is the most common reason for failure to provide dermal local anesthetic, which underscores the need for nurse managers and educators to develop policies and procedures that support the nurse’s use of local anesthetics and to teach nurses who perform painful dermal procedures how to competently use them (Brown, 2002).

To administer intradermal local anesthesia, a wheal of approximately 1-cm diameter (approximately 0.05 to 0.1 mL) of lidocaine 1% is injected intradermally with a 29- or 30-gauge needle over or just distal to the vein or artery (Pasero, McCaffery, 1999). Patients often report burning and stinging with intradermal injection of lidocaine. This is caused by the acidic nature of the lidocaine solution and can be reduced by adding sodium bicarbonate to normalize the pH (buffering) (Strichartz, Berde, 2005; Wong, Pasero, 1997) (Box 28-1). Administration of buffered lidocaine 1% is recommended 2 minutes prior to venipuncture and has been shown to produce superior anesthesia compared with unbuffered lidocaine 1%, diphenhydramine 1%, and 0.9% saline placebo (Xia, Chen, Tibbits, et al., 2002). Warming the lidocaine by rolling the syringe between the hands several times and slowing the speed of injection can also reduce the pain associated with intradermal lidocaine. Lidocaine has been warmed to 40° to 42° C in a controlled warm-water bath but should never be warmed in a microwave (Achar, Kundu, 2002; Pasero, McCaffery, 1999).

Intradermal lidocaine was shown to produce superior anesthesia compared with another antihistamine (chlorpheniramine) and midazolam in healthy volunteers (Orhan, Yuksel, Bilgin, et al., 2007). However, bacteriostatic saline may be an even better choice than lidocaine to anesthetize the site prior to a venous or arterial puncture. A randomized controlled trial administered lidocaine 1%, bacteriostatic normal saline, or no intradermal anesthesia to 221 adults prior to outpatient or same-day surgery (Windle, Kwan, Warwick, et al., 2006). Venipuncture was significantly less painful with both lidocaine and bacteriostatic saline compared with placebo, and bacteriostatic saline produced better anesthesia than lidocaine. It is important to note that the saline must be bacteriostatic, because it is the 0.9% benzyl alcohol preservative that produces the local anesthetic effect (Pasero, McCaffery, 1999).

Infiltrated lidocaine, particularly when buffered, provides an excellent option for controlling pain during more extensive procedures as well. A randomized controlled trial administered buffered lidocaine or unbuffered lidocaine to patients prior to posterior iliac crest bone marrow biopsy (Ruegg, Curran, Lamb, 2009). Those who received buffered lidocaine reported significantly lower pain scores leading the researchers to conclude that the use of unbuffered lidocaine for such a procedure should be questioned. Others have found similar results with buffered lidocaine (Vossinakis, Stavroulaki, Paleochorlidis, et al., 2004; Younis, Bhutiani, 2004) and warmed lidocaine (Yiannakopoulos, 2004) for other procedures.

Femoral artery sheath removal is a painful procedure, but there is no consensus on how best to manage the pain. Infiltrated lidocaine may not be the best choice for this particular procedure. Patients in one study were randomized to receive IV fentanyl and midazolam, or lidocaine 1% infiltrated around the femoral sheath, or both treatments, or neither treatment (Kiat Ang, Leung, Lo, et al., 2006). The highest pain scores and the highest incidence of vasovagal reactions were in the group who received local anesthesia only. These findings led the researchers to caution against the use of lidocaine infiltration prior to femoral sheath removal and suggest IV fentanyl and midazolam instead.

Adverse effects are rare with infiltrated local anesthetics such as lidocaine because there is minimal systemic absorption when they are given in small amounts for minor procedures. However, at low doses, local anesthetics have been known to produce vasoconstriction and hypertension in some patients (Achar, Kundu, 2002). The addition of epinephrine can slow absorption but can also further increase vasoconstriction and should not be used on tissues with end arteriole blood supply, such as fingers, toes, the penis, nose, or ears (Pasero, McCaffery, 1999). Signs of systemic toxicity include metallic taste, tinnitus, perioral numbness, lightheadedness, and confusion. If not detected, this can proceed to tremors, shivering, and ultimately seizures and respiratory and cardiovascular collapse (Achar, Kundu, 2002). Allergy to amide local anesthetics is rare but is a contraindication to use.

EMLA

Eutectic mixture of local anesthetics (EMLA), available only by prescription in the United States (nonprescription in some other countries, e.g., Canada), combines lidocaine 2.5% and prilocaine 2.5% in a cream for topical application. Most anesthetic agents exist as solids preventing efficient skin penetration (Kundu, Achar, 2002). However, a eutectic mixture, which has a melting point lower than that of the two anesthetics alone, permits the drug to penetrate the skin (see Figure 24-1 on p. 685 for action site).

To create an area of dense sensory loss using EMLA, a relatively thick application must remain in contact with the skin for at least 1 hour (2.5 g [½ of a 5 g tube] per 20 to 25 cm² [2 inch by 2 inch] area to a maximum of 10 g). This is usually covered with an occlusive dressing, but occlusion is optional and intended to help keep the drug in place. The application site can be expanded as needed for major dermal procedures. Clinical experience suggests that a 90- to 120-minute application time produces the best results. This time should be reduced significantly and the drug removed promptly when EMLA is applied to male genital skin and female genital mucous membranes (see EMLA drug package insert). The depth of anesthesia is approximately 3 mm after a 60-minute application and 5 mm after 120 minutes (Kundu, Achar, 2002). The 60- to 120-minute application time is a noted drawback of the drug because it requires preplanning (Eidelman, Weiss, Lau, et al., 2005); however, most procedures are not emergencies and allow for this. A benefit of EMLA is a comparatively long duration of anesthesia, reaching maximal anesthesia at 2 to 3 hours and lasting up to 2 hours after the cream is removed (Wong, 2003). This is an advantage for longer procedures or when pain is expected after the procedure is completed. Another commonly used topical local anesthetic, L.M.X.4, has a shorter duration of up to 60 minutes (see later in the chapter).

The manufacturer (AstraZeneca) recommends that EMLA be applied to intact skin and genital mucous membranes only; however, it has also been applied to or around extremity lacerations and other types of open wounds (Briggs, Nelson, 2003; Kundu, Achar, 2002). Variable penetration is reported when EMLA is applied to hands and soles of the feet (Kundu, Achar, 2002), and it should not be applied to eyes as this can result in severe irritation and corneal abrasion.

An extensive systematic review of research on local anesthetics for painful dermal procedures reported inconsistent findings with regard to comparisons between EMLA and infiltrated local anesthetic; half of the research favored EMLA, and half favored infiltrated local anesthetic (Eidelman, Weiss, Lau, et al., 2005). EMLA and L.M.X.4 were equally efficacious in this review, but the latter was described as preferable because it is commercially available, has a more rapid onset of action (L.M.X.4 = 30-minute application time), and is less expensive (Eidelman, Weiss, Lau, et al., 2005).

EMLA has been shown to reduce pain of needle puncture when applied prior to local anesthetic blockade (Raber, Scattoni, Roscigno, et al., 2008; Samson, Minville, Chassery, et al., 2007), IV catheter placement, and lab blood tests (Eidelman, Weiss, Lau, et al., 2005). A Cochrane Collaboration Review concluded that EMLA produced effective pain relief for venous leg ulcer debridement, but suggested further research to determine its impact on ulcer healing (Briggs, Nelson, 2003). A case report described the development of hemorrhagic margins around leg ulcers that led to ischemia and necrosis following application of EMLA for debridement (Stahl, Meyer, Haas, et al., 2008). EMLA was ineffective for treatment of pain during vasectomy (Thomas, Nguyen, Dhar, et al., 2008) and amniocentesis (Pongrojpaw, Somprasit, Chanthasenanont, 2008).

The use of topical analgesics is strongly encouraged in pediatric patients undergoing painful procedures. As a result, the vast majority of research showing EMLA to be safe and effective for painful procedures has been conducted in that population and findings extrapolated to adults. The reader is referred to the pediatric literature for more research. Some of the studies showing efficacy in adults are listed as follows.