Local Anaesthetic for Wound Management

This post is part of the Basic Guide to Suturing series. Here we take a look at using local anaesthetic, to help us manage a simple wound/laceration. 

Firstly a recap of the wound management process.

1. Assess
2. Gather required equipment
3. Prep & Drape
4. Anaesthetise
5. Clean/Irrigate
6. Suture (see Overview of Suturing Techniques for more details)
7. Bandaging/Dressing and ongoing wound-care

Remember if cleaning the wound is painful or difficulty to examine, anaesthetising earlier may be beneficial and kinder to your patient.

Indications

• For pain control and analgesia during a procedure or assessment

Contraindications

• Known allergic reaction or anaphylaxis
• Large or multiple lacerations requiring significant doses
• Local tissue infection (relative)
• Patient refusal

Precautions

• Intravascular injection of local anaesthetic (injection should follow Aspiration to ensure extravascular administration)
• Use of adrenaline (see below for areas and particular patients where caution should be used)
• Prior adverse reaction (including vasovagal reaction)
• Pre-existing neurological and cardiac disorders
• Hepatic or renal impairment

A bit about Local Anaesthetics

“A local anaesthetic can be defined as a drug which reversibly prevents transmission of the nerve impulse in the region to which it is applied, without affecting consciousness.” FRCA

It is important as a Medical Student or Junior Doctor to have a basic understanding of the side-effects, doses and key properties of common local anaesthetics. In general, local anaesthetics work by stabilising the neuronal membrane and preventing the transmission of nerve impulses.

An overview of Lignocaine is provided here. For other agents, see the comparison table below.
For more details see Local Anaesthetics by the Royal Adelaide ICU, useful resource for those studying for the various critical care primary examinations.

Lignocaine/Lidocaine/Xylocaine

Lignocaine is one of the most commonly used local anaesthetic agents. It is suitable for surface, infiltration, nerve block, caudal, epidural, and spinal anaesthesia.

MOA

• Binds selectively to refractory Na+ channels -> preferentially when cells are depolarised

Dosing

• Maximum dose of lignocaine without adrenaline is ~3 mg/kg.
• Maximum dose of lignocaine with adrenaline is ~7 mg/kg. 

Adverse effects

• lightheadedness
• hypotension
• cardiovascular collapse
• heart block
• confusions
• seizures

Adrenaline/Epinephrine

Adrenaline is a common additive in your local anaesthetic. Acting as a vasoconstrictor, it helps prolong the action of your local anaesthetic, decrease systemic absorption and risk of toxicity, and reduce traumatic blood loss. Consequently, it also allows you to deliver a higher dose of your local anaesthetic.

Contraindications

• Conditions where tachycardia is detrimental (thyrotoxicosis, CCF, IHD)
• Periorbital infiltration in patients with narrow angle glaucoma
• Digital anaesthesia in patients with peripheral artery disease 

Precautions

• Patients with catecholamine sensitivity
• Patients taking monoamine oxidase inhibitors, beta blockers, anti-arrhythmics, phenothiazines, or tricyclic antidepressants
• Pregnant patients

Equipment

• Local Anaesthetic Agent
• Syringe (e.g. 5ml, 10ml)
• Needles (large sharp or blunt drawing up needle; 25-30G needle for infiltration)
• Personal protective equipment
• Skin cleansing agent (e.g. alcohol swabs/wipes, chlorhexidine or povidone-iodine solution)
• Sterile Gauze

Dosing

Be aware of the parameters of the Local Anaesthetic you are using and it's safety profile.

See the table below for common local anaesthetic agents. More details on how to accurately dose local anaesthetics in Optimising Local Anaesthetic Administration.

Procedure (local infiltration)

1. Discuss with and gain patient consent for the procedure.
2. Consider use of topical analgesics, as they will take some time to work.
3. Gather required equipment and don PPE.
4. Draw up your local anaesthetic by either sharp or blunt needle, or directly via syringe from the ampule.
5. Prepare skin with cleansing agent (chlorhexidine or povidone-iodine) if infiltrating through intact skin. Allow skin to air-dry or dry with your sterile gauze.
6. Remove any gross contamination inside the wound with normal saline.
7. Then insert the needle directly though the wound edge (rather than intact skin where possible) into the subcutaneous layer.
8. Aspirate to rule out intravascular placement.
9. Advance needle forward and slowly inject small volumes of LA. Alternatively advance needle the full distance and inject slowly on withdrawal.
10. Remove needle.
11. Repeat until the area is fully anaesthetised or maximum dose is reached. Re-insert the needle if required through previously anaesthetised areas.
12. Wait for the anaesthetic to take effect, and then test for adequate coverage. Use either your injection needle or other sharp object (e.g. suture needle) to test anaesthetic coverage.
13. You are now free to further examine, clean/irrigate the wound or begin your primary procedure (e.g. suturing).

Post-Procedure Care 

Patients should be advised of likely timeframes for recovery of full sensation after Local Anaesthetic administration. Consequently, it is also important to assess neurovascular status prior to injecting local anaesthetic.

They should also lookout for/represent if;

• infection or neurovascular compromise
• systemic toxicity
• allergic reaction

Optimising local administration

See Optimising Local Anaesthetic Administration for handy tip/tricks.

Local Anaesthetic Table

	Onset (min)	Duration (min)	Max dose (mg/kg)	Max mg (70kg person)
Lignocaine (1% or 2%) (Xylocaine)	2	15-60	3mg/kg	220mg (11mL 2%) (22mL 1%)
Lignocaine with adrenaline (1% or 2%)	2	120-360	7mg/kg	500mg (25mL 2%) (50mL 1%)
Bupivicaine (0.25%) (Marcain)	5	120-240	2.5mg/kg	175mg(50mL)
Bupivicaine with adrenaline	5	180-420	3mg/kg	225mg
Prilocaine (0.5% or 1%) (Citanest)	2	30-90	7mg/kg	500mg<70kg 1="" ml="" td="">
Ropivocaine (0.25%) (Naropin)	5	120-360	3mg/kg	225mg

Alternatives

Nitrous oxide (Entonox®), topical analgesia, sedation, general anaesthesia

Local Anaesthetic Toxicity

• LITFL: Guide to Local Anaesthetic Toxicity
• LITFL: CCC Local Anaesthetic Toxicity

References:

• LITFL: Lignocaine
• Essentials of Local Anesthetic Pharmacology (2006)