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Glossar

Side effects of local anaesthesia: definition and significance

Side effects of local anaesthesia range from swelling and redness at the injection site to dizziness, cardiac arrhythmia or, very rarely, anaphylactic shock.

Side effects of local anaesthesia:

Adverse reactions following local anaesthesia, which may range from mild local symptoms such as swelling or redness at the injection site to systemic effects such as dizziness, cardiac arrhythmia or, very rarely, anaphylactic shock.

Important note

This article is for information purposes only and is not a substitute for a medical diagnosis or advice. If you are unsure, or if you require a personalised treatment plan, it is essential that you consult a qualified specialist.

Side effects of local anaesthesia are undesirable physical reactions that occur during or after the administration of a local anaesthetic. They occur either locally at the injection site or systemically, when the active ingredient enters the bloodstream. The aim of this information is to provide patients with factual information prior to cosmetic or dental procedures.

Infographic on the side effects of local anaesthesia: an overview of local and systemic reactions

Anyone planning cosmetic surgery – be it liposuction, a nose job or eyelid surgery – is often treated under local anaesthesia. Local anaesthesia is considered safe and well-established, but like any medical procedure, it carries a residual risk. This glossary explains what side effects may occur, who is particularly at risk and what financial consequences complications may have.

Background information and details on the side effects of local anaesthesia

Key points at a glance:

  • Side effects of local anaesthesia occur locally (at the injection site) or systemically (in the bloodstream)
  • Most common mild reactions: swelling, redness, temporary numbness
  • More serious reactions: dizziness, syncope, cardiac arrhythmia
  • True allergies are rare and mainly affect older ester anaesthetics
  • Groups at particular risk: heart patients, pregnant women, patients with known allergies

Side effects of local anaesthesia can be divided into two main categories: local and systemic reactions. Local reactions occur directly at the injection site. Systemic reactions affect the whole body and occur when a large amount of the active substance enters the bloodstream.

The class of substance used is a key factor in determining the risk profile. Local anaesthetics are categorised into Ester type (e.g. procaine, tetracaine) and Amid type (e.g. lidocaine, articaine, bupivacaine, mepivacaine). Ester anaesthetics are rarely used nowadays because they cause allergic reactions significantly more often. Amide anaesthetics are considered to be better tolerated and are the current standard.

According to a systematic analysis by the University of Mainz, which evaluated Periodic Safety Update Reports (PSURs) for articaine and lidocaine from 2000 to 2010 — data set: over 1.75 billion ampoules administered — dizziness, vasovagal syncope and palpitations were among the most frequently reported systemic events. Life-threatening reactions occurred extremely rarely.

Mechanism of action of local anaesthetics and the development of side effects

Key points at a glance:

  • Local anaesthetics block voltage-gated sodium channels in nerve fibres
  • As a result, pain signals can no longer be transmitted to the brain
  • Adrenaline is often added as a vasoconstrictor to prolong the duration of action
  • Side effects occur when the active substance acts beyond the intended target area

Local anaesthetics block the voltage-gated sodium channels in the cell membrane of nerve fibres. As a result, the electrical signal that transmits a pain stimulus to the brain can no longer be conducted — the area remains temporarily numb. This mechanism of action is reversible: as soon as the active substance has been broken down, normal sensation returns.

Many local anaesthetic solutions also contain Adrenaline as a vasoconstrictor. Adrenaline constricts the local blood vessels, thereby slowing down the clearance of the anaesthetic. This prolongs the duration of anaesthesia. At the same time, adrenaline reduces the tendency to bleed in the surgical area. In patients with heart conditions, the adrenaline content must be carefully measured, as it can itself trigger cardiovascular effects.

Side effects occur in three ways:

  1. Local tissue irritation: The injection itself, the pH of the solution or the preservatives irritate the surrounding tissue.
  2. Intravascular injection: If the anaesthetic accidentally enters a blood vessel, it is distributed systemically — affecting the central nervous system and the heart.
  3. Immunological response: In the case of rare allergies, the immune system reacts to the active ingredient or excipients such as preservatives (e.g. methylparaben in ester-type formulations).

The type of anaesthesia affects the risk profile. In the case of Infiltration anaesthesia — direct injection into the tissue — systemic absorption remains low. In the case of Conductive anaesthesia (injection near a major nerve) and the Tumescent local anaesthesia (TLA), which is used in liposuction, involves the use of larger quantities of the active substance. This slightly increases the systemic risk.

Real-life examples of side effects from cosmetic procedures

Practical experience shows that certain patterns of side effects recur in cosmetic procedures. Three scenarios are particularly relevant:

Common local reactions at the injection site

Mild local side effects occur in a significant proportion of patients and subside within 24 to 48 hours:

This medical illustration shows local skin reactions such as redness and swelling at an injection site.
  • Redness and swelling due to the mechanical irritation caused by the injection
  • Haematoma (bruising) caused by accidental damage to small blood vessels
  • Burning or stinging when the solution is injected, due to its pH value
  • Temporary numbness in neighbouring areas, for example when adjacent areas are also anaesthetised during a nose job

Systemic reactions: LAST syndrome

The most feared systemic complication is the LAST, Systemic Toxicity Induced by Local Anaesthetics. Typical signs, listed in order of increasing severity:

Typical LAST symptoms (in order of appearance):

Tingling around the mouth, a metallic taste, dizziness, ringing in the ears (tinnitus); in severe cases: seizures, loss of consciousness, cardiac arrhythmia. If any of these symptoms are suspected, the procedure must be stopped immediately and emergency treatment initiated. The standard treatment is the intravenous administration of a lipid emulsion.

Comparison table: Ester versus amide anaesthetics

CharacteristicEster type (e.g. procaine, tetracaine)Amide-type (e.g. lidocaine, articaine)
Risk of allergiesElevated (para-aminobenzoic acid metabolite)Low
Duration of actionShort (30–60 minutes)Medium to long (1–8 hours, depending on the substance)
Use todayRare, historicalThe standard in dentistry and surgery
MiningIn blood plasma (pseudocholinesterase)In the liver
Suitability during pregnancyNot recommendedPossible (subject to a doctor’s assessment)

Common mistakes and best practices when dealing with side effects

Errors in the management of local anaesthesia side effects can be specifically avoided:

Avoidable mistakes:

  • No full medical history taken: The doctor must be fully informed of any pre-existing conditions, known allergies and current medication before the procedure.
  • Ignoring sobriety: Anyone who has not eaten anything shortly before the injection is more prone to vasovagal syncope — a light meal can reduce the risk.
  • Allergy symptoms not taken seriously: Tingling, redness of the skin or shortness of breath immediately after the injection are not minor issues — inform your doctor straight away.
  • Misjudgement: Allergy versus overdose: Many patients mistake the symptoms of an overdose (dizziness, tinnitus) for an allergy. The distinction is clinically relevant because the treatment differs.
  • There is a lack of self-monitoring following the procedure: Systemic reactions may occur as late as a few minutes after the injection — patients should remain at the surgery for the first 30 minutes.

What should you do if you suspect an allergic reaction or an overdose?

  1. Inform the doctor or medical staff immediately
  2. Have the procedure stopped
  3. Stay seated or lying down calmly; do not make any sudden movements
  4. In the event of breathing difficulties, loss of consciousness or a very rapid heartbeat: call the emergency number 112
  5. Record which anaesthetic was administered — this is important for follow-up treatment

Anyone who decides to undergo cosmetic surgery and has risk factors such as heart disease, known drug allergies or is pregnant should proactively raise the issue of side effects of local anaesthesia during the pre-operative consultation. The anaesthetic method and dose can then be adjusted.

Patient groups at increased risk of side effects

The following groups of patients require particularly careful counselling and dose adjustment:

Three people of different ages in a doctor’s surgery symbolise different patient groups, each with their own risk profile.
  • Heart patients: Pre-existing cardiac conditions increase the risk of cardiac arrhythmias when the anaesthetic is distributed systemically.
  • Pregnant women: Amide anaesthetics such as lidocaine may be used at the doctor’s discretion; ester anaesthetics are not recommended.
  • Older patients: The liver metabolises amide anaesthetics more slowly, which prolongs systemic exposure.
  • Patients with known allergies: Anyone who is sensitive to sulphonamides, paraben preservatives or para-aminobenzoic acid (PABA) is at a higher risk of an allergic reaction to ester anaesthetics.
  • Patients taking anticoagulants: Increased risk of bruising at the injection site.

As soon as complications arise following a cosmetic procedure and follow-up treatment becomes necessary, significant costs are incurred. Statutory and private health insurance schemes only cover follow-up treatment following cosmetic surgery under very strict conditions, or not at all. Follow-up costs insurance comes into play precisely in such cases: it covers medically necessary follow-up treatment, revision surgery and hospital stays — regardless of whether the complication was caused by the local anaesthetic, the procedure itself or the healing process.

Protect yourself against unexpected costs in the event of complications following cosmetic procedures.

Insure against consequential costs
A comparison of different methods of local anaesthesia: infiltration, block and tumescent anaesthesia

Frequently asked questions about the side effects of local anaesthesia

Mild local side effects such as swelling, redness or numbness subside completely within 24 to 48 hours. Systemic symptoms such as dizziness or palpitations are transient and disappear as soon as the active ingredient has been metabolised — usually within a few hours. Persistent or worsening symptoms require medical assessment.

Yes. True allergies to amide anaesthetics such as lidocaine or articaine are rare, but possible. They can develop upon first contact or following repeated exposure. Patients who are sensitive to preservatives such as methylparaben are at particular risk. An allergy test can be carried out before a planned cosmetic procedure if an allergy is suspected.

An allergic reaction is immunologically mediated: the immune system reacts to the active ingredient or excipients. Symptoms include skin redness, hives, shortness of breath or, in the worst-case scenario, anaphylactic shock. An overdose is dose-dependent and not immunological: too much active ingredient in the bloodstream causes dizziness, tinnitus, tingling or cardiac arrhythmia. Both reactions require immediate medical attention, but are treated differently.

For minor procedures, local anaesthesia is considered to carry fewer risks than general anaesthesia, as the patient remains conscious and there is less strain on the organs. Serious complications are very rare, but possible. The treating doctor decides on a case-by-case basis which anaesthetic method is appropriate.

Complications following cosmetic surgery — whether caused by the anaesthesia or the procedure itself — may require wound revision, inpatient treatment or corrective surgery. These costs are not covered by statutory health insurance. Insurance against follow-up costs protects you from unexpected financial burdens following cosmetic procedures.

Overview of systemic side effects of local anaesthesia, organised by organ system. All information is provided for general guidance only; clinical assessment is the responsibility of the treating doctor.

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