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Where should lidocaine not be injected?

5 min read

The incidence of severe systemic toxicity from local anesthetics is estimated to be as high as 1 in 2,000 for certain peripheral nerve blocks [1.4.1]. Understanding where should lidocaine not be injected is crucial for patient safety and preventing adverse outcomes.

Quick Summary

This article details specific anatomical locations and patient conditions where lidocaine injections are contraindicated, especially when combined with epinephrine, to prevent severe health risks.

Key Points

  • End Arteries: Do not inject lidocaine with epinephrine into areas with a terminal blood supply like fingers, toes, the nose, penis, or earlobes to avoid tissue necrosis [1.3.1, 1.3.3].

  • Intravascular Injection: Never inject lidocaine directly into a blood vessel; always aspirate first to prevent rapid systemic toxicity [1.2.6, 1.4.7].

  • Patient Allergies: Lidocaine is contraindicated in patients with a known hypersensitivity to amide-type local anesthetics [1.2.3].

  • Heart Conditions: Patients with severe heart block or specific arrhythmias should not receive lidocaine due to its cardiodepressant effects [1.2.2].

  • Joint Infusions: Avoid continuous intra-articular infusions of lidocaine, as this can cause chondrolysis, the destruction of joint cartilage [1.2.6].

  • Systemic Toxicity: Be aware of early signs of toxicity, such as circumoral numbness, metallic taste, and dizziness, which can progress to seizures and cardiac arrest [1.5.2, 1.5.3].

  • Preservatives: Do not use lidocaine solutions containing preservatives like methylparaben for spinal or epidural anesthesia [1.2.3].

In This Article

Understanding Lidocaine and Its Contraindications

Lidocaine is a widely used local anesthetic from the amino amide class, prized for its rapid onset of action (less than one minute) and intermediate duration (30-120 minutes) [1.6.1, 1.6.2]. It functions by reversibly blocking sodium channels in nerve membranes, preventing the propagation of pain signals [1.6.2]. While generally safe when administered correctly, there are specific situations and locations where lidocaine injections are hazardous and must be avoided to prevent serious complications like tissue damage, nerve injury, and systemic toxicity [1.4.1, 1.6.2]. A primary concern involves its use in areas with compromised blood supply or when administered improperly, leading to toxic plasma concentrations [1.2.6, 1.4.1].

Absolute and Relative Patient Contraindications

Certain patient-specific conditions make the use of lidocaine risky or entirely contraindicated. A healthcare provider must perform a thorough evaluation before administration.

Absolute Contraindications:

  • Known Hypersensitivity: Patients with a known history of allergy to lidocaine or other amide-type local anesthetics should not receive the drug [1.2.3]. True allergic reactions are rare but can be severe, leading to anaphylaxis [1.2.1, 1.6.2].
  • Severe Heart Block: Individuals with severe heart block, Stokes-Adams syndrome, or Wolff-Parkinson-White Syndrome should not receive lidocaine, as it can depress cardiac function and worsen these conditions [1.2.2].

Relative Contraindications & Precautions:

  • Hepatic Disease: Since the liver metabolizes amide-type anesthetics like lidocaine, patients with severe liver disease are at a higher risk of developing toxic plasma concentrations due to their inability to metabolize the drug normally [1.2.3, 1.2.6].
  • Cardiovascular Disease: Caution is required in patients with impaired cardiovascular function, as they may be less able to compensate for the drug's effects on atrioventricular (A-V) conduction [1.2.6].
  • Pregnancy: Lidocaine crosses the placenta and can cause maternal, fetal, and neonatal toxicity. Its use during labor and delivery requires careful monitoring of the fetal heart rate [1.2.3, 1.2.6].
  • Inflammation or Sepsis: Lidocaine should not be injected into areas with active inflammation or sepsis, as this can increase systemic absorption [1.2.3].
  • Neurological Disease: Patients with existing neurological diseases require extreme caution, particularly for epidural or spinal anesthesia [1.2.3, 1.2.6].

The Role of Epinephrine and Areas to Avoid

Lidocaine is often combined with epinephrine, a vasoconstrictor, to decrease blood flow at the injection site. This delays the systemic absorption of lidocaine, prolonging its anesthetic effect and reducing the risk of toxicity [1.6.2]. However, this combination is famously contraindicated in areas of the body supplied by end arteries or with a compromised blood supply [1.2.6]. Injecting a vasoconstrictor in these regions can lead to restricted blood flow, potentially causing ischemia (inadequate blood supply) and tissue necrosis (tissue death) [1.2.6].

The traditional mnemonic for areas to avoid with epinephrine is "Fingers, Toes, Penis, Nose, and Earlobes (Pinna)" [1.3.1, 1.3.3]. The rationale is that these extremities have a terminal blood supply, making them vulnerable to vasoconstriction-induced injury [1.3.1]. While some recent studies have suggested that using lidocaine with epinephrine in some of these areas (like the nose, pinna, and fingers) might be safe under controlled conditions by experienced specialists, the traditional teaching remains a critical safety guideline, especially in emergency and non-specialist settings [1.3.2, 1.3.4].

High-Risk Injection Techniques and Locations

Beyond specific anatomical regions, certain injection techniques carry a high risk of complications.

  • Intravascular Injection: Accidental injection directly into a blood vessel is one of the most common causes of systemic toxicity [1.4.1, 1.4.7]. This can cause a rapid spike in plasma lidocaine levels, leading to severe central nervous system (CNS) and cardiovascular effects [1.4.1, 1.5.2]. Healthcare providers must always aspirate (pull back on the syringe plunger) before injecting to check for blood return, though a negative aspiration does not completely guarantee safety [1.2.6, 1.4.7].
  • Intra-articular Infusion: Continuous infusion of lidocaine into a joint post-surgery is not recommended. This practice has been linked to chondrolysis, a condition where joint cartilage is destroyed, leading to chronic pain, stiffness, and sometimes requiring joint replacement surgery [1.2.3, 1.2.6].
  • Spinal and Epidural Anesthesia: While a standard procedure, incorrect administration can be dangerous. Solutions containing preservatives (like methylparaben) should never be used for epidural or spinal anesthesia [1.2.3]. High concentrations of lidocaine used in spinal anesthesia have been associated with transient neurologic symptoms (TNS), characterized by pain or dysesthesia [1.4.1, 1.4.8].
  • Head and Neck Area: Injections in the head and neck, such as for dental or retrobulbar blocks, require small doses. Accidental intra-arterial injection can cause the anesthetic to flow backward to the cerebral circulation, producing reactions similar to systemic toxicity even with small amounts [1.2.6].
Injection Site Category Risk Level with Lidocaine & Epinephrine Primary Concern Safe Alternative/Precaution
Digits (Fingers, Toes) High Ischemia, Necrosis [1.3.1] Use plain lidocaine; digital block
Penis High Ischemia, Necrosis [1.3.3] Use plain lidocaine
Nose, Ear Pinna High (Traditionally) Ischemia, Necrosis [1.3.1] Use plain lidocaine; specialist discretion [1.3.2]
Intra-articular (Joints) High (for infusion) Chondrolysis (cartilage damage) [1.2.6] Single injection only; avoid continuous infusion
Highly Vascular Areas Moderate to High Rapid absorption, Systemic Toxicity [1.4.1] Slow injection, aspirate frequently, use epinephrine
Areas with Inflammation/Infection Moderate Increased absorption, reduced efficacy [1.2.3] Drain abscess first; consider alternative anesthesia

Understanding and Recognizing Lidocaine Toxicity

Local Anesthetic Systemic Toxicity (LAST) is a life-threatening complication that occurs when lidocaine reaches high levels in the bloodstream [1.4.6, 1.5.5]. It primarily affects the central nervous system (CNS) and the cardiovascular system [1.5.5]. The onset can be rapid (within minutes) if due to intravascular injection, or delayed (up to 60 minutes) if due to absorption from tissues [1.4.3].

Early CNS Symptoms (often excitatory):

  • Circumoral numbness (around the mouth) and tongue paresthesia [1.4.1, 1.5.2]
  • Metallic taste in the mouth [1.5.3, 1.5.4]
  • Lightheadedness, dizziness, and tinnitus (ringing in the ears) [1.5.2, 1.5.3]
  • Visual and auditory disturbances [1.4.3]
  • Restlessness, agitation, and muscle twitching [1.5.2]

As toxicity progresses, it can lead to seizures, unconsciousness, respiratory depression, and coma [1.4.1, 1.5.2].

Cardiovascular Symptoms (usually occur at higher concentrations):

  • Bradycardia (slow heart rate) [1.2.2]
  • Hypotension (low blood pressure) [1.2.1]
  • Cardiac arrhythmias (irregular heartbeat) [1.4.1]
  • Cardiovascular collapse and cardiac arrest [1.4.1, 1.5.2]

Immediate medical intervention, including airway management, seizure suppression, and often administration of a lipid emulsion therapy, is required to treat LAST [1.5.4, 1.5.7].

Conclusion

While lidocaine is an invaluable tool in modern medicine for pain management, its use requires rigorous adherence to safety protocols. Knowing where should lidocaine not be injected—particularly formulations containing epinephrine—is paramount. Avoiding areas with end-arterial circulation, refraining from continuous intra-articular infusions, and using meticulous technique to prevent intravascular injection are critical steps. Equally important is recognizing patient-specific contraindications and the early signs of systemic toxicity to ensure that this effective anesthetic is used safely and appropriately.


For more information from an authoritative source, you can visit the FDA label for Lidocaine Hydrochloride Injection. [1.2.1]

Frequently Asked Questions

Injecting lidocaine with epinephrine into fingers and toes is not recommended because these areas are supplied by 'end arteries.' The epinephrine can constrict these blood vessels so much that it cuts off the blood supply, leading to tissue damage or necrosis (tissue death) [1.3.1, 1.3.3].

Accidental intravascular (into a vein) injection can cause Local Anesthetic Systemic Toxicity (LAST). This leads to a rapid increase in the drug's concentration in the blood, potentially causing severe central nervous system effects like seizures and cardiovascular problems like arrhythmias or cardiac arrest [1.4.1, 1.4.7].

Yes, although it is rare, a person can have a true allergic reaction to lidocaine or other amide-type anesthetics. It is contraindicated for anyone with a known history of hypersensitivity to these drugs [1.2.3, 1.6.2].

It depends on the condition. Lidocaine should not be used in patients with severe heart block or certain arrhythmias like Stokes-Adams syndrome. In patients with other heart conditions, it should be used with caution as it can affect heart rate and function [1.2.2, 1.2.6].

Early signs of lidocaine toxicity often affect the central nervous system and include numbness or tingling around the mouth, a metallic taste, ringing in the ears (tinnitus), dizziness, and visual disturbances [1.5.2, 1.5.3].

No, local anesthetic procedures should generally be avoided in areas where there is inflammation and/or sepsis. The acidic environment of an infection can reduce the effectiveness of the anesthetic, and the increased blood flow can lead to faster systemic absorption and higher risk of toxicity [1.2.3].

Continuous infusion of lidocaine into a joint after surgery has been linked to chondrolysis, a serious condition where the articular cartilage of the joint is destroyed. This can lead to chronic pain and loss of motion, sometimes requiring further surgery like a joint replacement [1.2.6].

References

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Medical Disclaimer

This content is for informational purposes only and should not replace professional medical advice.