11/13/24, 7\:20 PM Guide | Infiltration of local anaesthetic

In

Table of contents

Introduction

Local anaesthesia is used to prevent the sensation of pain and allow procedures and surgeries without general anaesthetic. It
can be administered in various ways\:
In
Peripheral nerve block (usually for limb surgeries, e.g. using ultrasound imaging to inject around the brachial plexus)
Central anaesthesia such as spinal or epidural
This in
setting.

Background

Mechanism of action

Nerve conduction is blocked by inhibiting sodium ion in
to be in an unionised form to penetrate the neural membrane.
pKa determines the ratio of ionised to unionised local anaesthetic. The closer the pKa is to the body's pH, the faster the onset
of the anaesthetic. The stability of the agents is increased by making the pH slightly acidic. This is one of the reasons injections
are associated with a burning sensation.
Anaesthetic blockage a
nerves are also quicker to recover from anaesthetic blockage.
Local anaesthetics are ine
https\://app.geekymedics.com/osce-guides/clinical-procedures/infiltration-of-local-anaesthetic/ 1/511/13/24, 7\:20 PM Guide | Infiltration of local anaesthetic
Figure 1. Local anaesthetic action on nerve types

Types of local anaesthetic

These are broadly separated into two groups, ester-linked and amide-linked.
Esther-linked anaesthetics
Esther-linked anaesthetics are metabolised by pseudocholinesterase and produce para-aminobenzoic acid (PABA) as a by-
product. This is important because PABA is associated with allergic reactions. Therefore, these agents are not frequently used
in clinical practice.
Examples of esther-linked agents include\:
Cocaine (the only vasoconstrictor, still used in rhinoplasty)
Procaine
Tetracaine
Amide-linked anaesthetics
Amide-linked anaesthetics are metabolised in the liver, and allergic reactions are rare. Allergic reactions can occur if PABA is
used as a preservative. Amide-linked agents are frequently used in clinical practice. All amides have an ‘i’ in the pre
Examples of amide-linked agents include\:
Lidocaine\: most commonly used, short-acting, dosage is 3mg/kg plain or 7mg/kg with adrenaline (e.g. xylocaine 1% with
1\:200,000 adrenaline)
Bupivacaine\: slower onset but longer duration upward of 8 hours e
2mg/kg (not changed by the addition of adrenaline), can be cardiotoxic (ventricular arrhythmias), particularly in patients with
acidosis, hypercarbia or hyperaemia
Levobupivacaine\: similar to bupivacaine but reduced cardiotoxicity, dosage is 3mg/kg
Prilocaine\: rapid onset and metabolism, metabolite causes methaemoglobinaemia
Ropivacaine\: long-acting with reduced cardiac and central nervous system toxicity

Topical anaesthetics

Topic anaesthetics are frequently used in paediatrics before venepuncture or cannulation. Examples include\:
Ametop\: 4% tetracaine, requires an occlusive dressing, onset is 45 minutes
EMLA (eutectic mixture of local anaesthetic)\: 2.5% lidocaine and 2.5% prilocaine, onset is >1 hour

Local anaesthetic additives

https\://app.geekymedics.com/osce-guides/clinical-procedures/infiltration-of-local-anaesthetic/ 2/511/13/24, 7\:20 PM Guide | Infiltration of local anaesthetic
Adrenaline
intraoperative bleeding.
Adrenaline can be added to local anaesthetic in di
Care must be taken with adrenaline as larger doses increase myocardial activity (e.g. tachycardia, hypertension, potential
arrhythmias).
Examples of local anaesthetic with adrenaline preparations include\:
Xylocaine\: lidocaine with 1\:200,000 (1mg/200ml) adrenaline
Lignospan\: lidocaine with 1\:80,000 (1mg/80ml) adrenaline
Care should be taken when using local anaesthetics in the hand and digits (use a concentration of 1\:200,000). These
preparations should not be used in the penis.
Sodium bicarbonate
Sodium bicarbonate (alkaline solution) has also been shown to increase the speed of onset of anaesthetic, enhance its e
and reduce the pain of injection.

Dosage calculations

Dose calculations can be confusing as the concentrations are expressed as a percentage, whereas the maximum dosages
are expressed as milligrams per kilogram.
Multiply the percentage by 10 to work out the dosage of anaesthetic per millilitre\:
Lidocaine 1% contains 10mg/ml
Levobupivicaine 0.25% contains 2.5mg/ml
Local anaesthetic toxicity
Local anaesthetic toxicity is rare but must be recognised and managed promptly. Causes of toxicity include dosage error
or inadvertent intravascular injection. Toxicity predominantly a
system.
Clinical features related to the central nervous system include\:
Dizziness
Peri-oral paraesthesia
Disorientation
Tinnitus
Muscle twitching
Seizures (tonic-clonic)
Coma
Clinical features related to the cardiovascular system (requires higher doses) include\:
Sinus bradycardia due to blockade of the spontaneous pacemaker
Depression of cardiac contractility
Sinus arrest
Bupivacaine can cause refractory ventricular
Management of local anaesthetic toxicity\:
Stop any further local anaesthetic in
Call for help
Administer high-ABCDE algorithm
If circulatory arrest, commence basic life support
Administer 1.5ml/kg of 20% lipid emulsion (e.g. intralipid emulsion) as a bolus over 1 minute, followed by an infusion of
15ml/kg/hour. Further boluses and changes to the infusion rate may be required.
Recovery may take over an hour, so it is important to continue resuscitation.
https\://app.geekymedics.com/osce-guides/clinical-procedures/infiltration-of-local-anaesthetic/ 3/511/13/24, 7\:20 PM Guide | Infiltration of local anaesthetic

Gather equipment

Gather the appropriate equipment\:
Alcohol wipe
Gloves and necessary personal protective equipment
Syringe\: 5ml, 10ml, 20ml depending on volume required
Filter needle\: blunt needle for drawing up local anaesthetic
Needle\: ideally narrow bore such as a 27 gauge (white) to encourage slow injection, but can use a 22 gauge (blue)
Gauze to dab any bleeding spots

Select an appropriate local anaesthetic

Select an appropriate local anaesthetic for the procedure. Fast-acting anaesthetics allow speedy onset but wear o
using a combination is ideal. It is important to be meticulous with calculations to ensure you do not overdose the patient.

Fast acting

Fast-acting local anaesthetics include\:
Lidocaine 1%\: 3mg/kg
Xylocaine 1% (has 1\:200,000 adrenaline)\: 7mg/kg (ideal, as you can give higher volumes and adrenaline causes
vasoconstriction reducing bleeding)
These should be used with caution in end-arteries.

Slow acting

Slow-acting local anaesthetics include\:
Levobupivacaine 2mg/kg (better in patients with cardiac disease)
Bupivacaine 2.5mg/kg
Example dose\: 5ml 1% xylocaine mixed with 5mL 0.25% levobupivacaine to make up total 10mL

Introduction

Wash your hands and don PPE.
Introduce yourself to the patient including your name and role.
Con
Brie
" B e f o r e w e s t a r t t h e p r o c e d u r e , I' m g o i n g t o
u s e a l o c a l a n a e s t h e t i c t o n u m b t h e s k i n . T h i s w i l l i n v o l v e m e u s i n g a s m a l l n e e d l e t o i n j e c t a l o c a l a n a e s t h e t i c d r u g j u s t
u n d e r n e a t h t h e s k i n . I' m a f r a i d t h e i n j e c t i o n c a n g i v e y o u a b u r n i n g s e n s a t i o n . T h i s w i l l t a k e a r o u n d 5 - 1 0 m i n u t e s t o w o r k , a f t e r
t h i s , y o u s h o u l d n o t f e e l a n y p a i n , a l t h o u gh y o u m a y f e e l s o m e p u l l i n g a n d p u s h i n g"
Check if the patient has an allergy to local anaesthetic (e.g. lidocaine).
Gain consent to proceed with local anaesthesia.

In

1. Assess the site requiring local anaesthetic and clean the skin with an alcohol wipe away from the wound before injection.
Open wounds should be cleaned with saline or aqueous
2. Allow the alcohol to dry on the skin
3. Draw up the required local anaesthetic into a syringe using a red
https\://app.geekymedics.com/osce-guides/clinical-procedures/infiltration-of-local-anaesthetic/ 4/511/13/24, 7\:20 PM Guide | Infiltration of local anaesthetic
4. Mount your narrow gauge needle on the syringe
5. Put a little tension on the skin to make it taut, and introduce the needle below the dermis
6. Withdraw the plunger on the syringe gently to ensure there is no
is, withdraw the needle and compress the area for 30 seconds to prevent haematoma
7. Inject the local anaesthetic very slowly to start, looking at the patient’s reaction. Once you have injected approximately 1mL,
begin to advance the needle slowly, injecting as you move, watching the dermis plump up with
8. Repeat this process until you have administered local anaesthetic to the desired area
9. Wait for 5-10 minutes, as this will allow the local anaesthetic and adrenaline to work
10. Test the area with your needle (and the patient’s eyes closed) to see if they feel sharpness. They may feel pulling and
pushing but should not feel the pin prick.
11. Once the area is numb, you can start the procedure
12. Remember to place sharps in the sharps bin and any other material in the clinical waste bin
Tips for the in
Use a
Move the needle as you inject to prevent large dose intravascular injection
Inject slowly to reduce the pain of in
of pain and may a
You can combine anaesthetics in one injection (e.g. 5ml of 1% lidocaine and 5ml of 0.25% levobupivacaine). This
combines fast onset with a longer duration of anaesthesia. You can also add 1ml of 8.4% sodium bicarbonate to
reduce pain and decrease the onset of anaesthesia. Alternatively, some clinicians use a fast-acting local anaesthetic
before the procedure and give slow-acting anaesthetic at the end whilst the area is still numb.
Source\: geekymedics.com
https\://app.geekymedics.com/osce-guides/clinical-procedures/infiltration-of-local-anaesthetic/ 5/5