From the Guidelines
The patient is likely not achieving local anesthesia after lidocaine infiltration due to inadequate dosage or volume of the medication, incorrect injection technique, or insufficient time allowed for the medication to take effect.
Possible Causes
- Inadequate dosage: the maximum safe dose of local infiltrated anesthesia is unknown, but for adults, no more than 4.5 mg/kg of lidocaine and 7.0 mg/kg of lidocaine with epinephrine should be administered in a single treatment 1.
- Incorrect injection technique: it is essential to inject the lidocaine slowly and carefully, aspirating prior to injection to avoid intravascular administration.
- Insufficient time: the onset of action is expected within 2-5 minutes, with a duration of action lasting approximately 30-60 minutes.
Recommendations
- Use of 1-2% lidocaine solution for infiltration anesthesia 1.
- Consider alternative forms of local infiltration anesthesia, such as ester-type local anesthetics, bacteriostatic normal saline, or 1% diphenhydramine, for patients with true allergy to lidocaine 1.
- Be aware of patient factors that may influence lidocaine toxicity, such as acid-base status, hypoxaemia, hypoalbuminaemia, and drug interactions 1.
From the FDA Drug Label
The lowest dosage that results in effective anesthesia should be used to avoid high plasma levels and serious adverse effects. Repeated doses of lidocaine HCl may cause significant increases in blood levels with each repeated dose because of slow accumulation of the drug or its metabolites. Dosage recommendations should not be exceeded (see DOSAGE & ADMINISTRATION).
The patient may not be achieving local anesthesia after lidocaine infiltration due to inadequate dosage or excessive dosage leading to toxicity. It is essential to follow the recommended dosage guidelines and monitor the patient's vital signs to avoid adverse reactions 2. Intravascular injection is also a possible cause, and aspiration for blood should be performed before and during each supplemental injection to minimize this risk 2.
From the Research
Possible Reasons for Ineffective Local Anesthesia
- The patient may not be achieving local anesthesia after lidocaine infiltration due to the time interval between the end of infiltration and the start of the procedure. According to 3, the median time to achieve effective anesthesia in 95% of patients is between 33 to 85 seconds after infiltration of 3 mL of 1% plain lidocaine.
- The dose or concentration of lidocaine used may be insufficient to produce effective anesthesia. Studies such as 4 and 5 have demonstrated the effectiveness of lidocaine in reducing pain, but the optimal dose and concentration may vary depending on the specific procedure and patient population.
- The technique of infiltration may be a factor, as the study by 3 used a specific method of infiltration and a particular type of needle.
Factors Affecting Lidocaine Efficacy
- The type of procedure being performed may influence the effectiveness of lidocaine. For example, 4 found that perineural lidocaine infiltration was effective in reducing postoperative pain after laminectomy surgery, while 6 and 7 demonstrated the benefits of intravenous lidocaine infusion in reducing pain and improving recovery after surgery.
- Patient characteristics, such as gender and previous experience with pain, may also affect the efficacy of lidocaine. As shown in 5, females reported higher pain scores than males when receiving buffered 1% lidocaine for IV catheter insertion.
Considerations for Optimal Lidocaine Use
- The use of adjuvants, such as buffering agents, may enhance the effectiveness of lidocaine. The study by 5 found that buffered 1% lidocaine was more effective than bacteriostatic normal saline in reducing pain during IV catheter insertion.
- The timing of lidocaine administration may be critical, as demonstrated by 4, which found that perineural lidocaine infiltration before the onset of noxious stimuli was effective in reducing postoperative pain.