Intraoperative care Flashcards
Why is it important to address and manage pain in the ED?
- Many patients presenting to ED are in pain it is important to ascertain the site and characteristic of the pain in order to diagnose underlying problem
- Relief of pain is essential as pain and distress may prevent patients from giving important details of history and may prevent cooperation with investigations or treatment
Options for managing pain
- Analgesics: before giving any drug check what was taken at home or given free hospital, consider allergies
- Splinting of fractures can help relieve pain also use of Entonox whilst splint or cast is being applied
- Cool down burns by running them under cold water
- Heat may be useful following sprains and strains of the neck, back and limbs
- Elevation especially following limb injuries as they cause considerable swelling causing pain and stiffness
- Local Anastasia provides excellent time relief for a fractured shaft of femur in the form of a femoral nerve or fascia iliaca compartment block
- Always check for nerve injury before injecting LA, consider using a small amount of LA subcutaneously before taking an ABG
What is entonox?
Mixture of nitrous oxide and oxygen
Inhaled via a mask or mouthpiece
Gives rapid and effective analgesia
Used in the ED whilst splinting limb injuries e.g. relocation of patella
Patient will feel drowsy or drunk, wears off within a few mins
What is the standard analgesic for severe pain?
Morphine
Consider giving an anti-emetic at the same time
How does ketamine work?
NMDA receptor antagonist - interferes with the pain transmission in the spinal cord
One of the dissociative anaesthetics
What are dissociative anaesthetics?
Form of anaesthetic agents that cause catalepsy, catatonia, analgesia and amnesia
They cause dissociation from the environment and/or self
Do not necessarily cause a loss of consciousness therefore do not fit under the category of general anaesthesia
Ketamine is the commonly used type of dissociative anaesthetic
How can ketamine-induced hallucinations be reduced?
Midazolam
The occurrence of hallucinations is a reason for which there is a reluctance to use ketamine in adult hospital practice - hallucinations are less of a problem in children therefore ketamine is useful for sedating children e.g. during wound suturing
Why is ketamine useful in asthmatic patients?
It is a bronchodilator
Examples of opioids
Codeine:
Weak opioid, used orally for moderate pain. Pro-drug so efficacy varies
Dihydrocodeine:
Very similar to codeine but stronger euphoric effect and has a greater dependence potential
Tramadol:
Stronger than codeine, inhibits 5-HT and NA reuptake in addition to opiate effects
Useful for the management of chronic pain in patients who cannot take NSAIDs
Diamorphine:
AKA heroin, used to treat severe pain associated with surgery, MI and terminal illness
Fentanyl:
Short acting opioid, useful for patients undergoing brief procedures in the ED e.g. relocation, reduction of fractures etc
Rapid onset and offset
Risk of inducing apnoea
Examples of local anaesthetics
Lidocaine (aka lignocaine
Bupivacaine
Tetracaine
Proxymetacaine
Lidocaine
LA most often used for local infiltration and nerve blocks
Available as a plain solution or mixed with adrenaline
Plain lidocaine lasts for 30-60 mins, when mixed with adrenaline lasts for 90 mins (duration depends on dose given and local circulation)
Mechanism of local anaesthetics
LAs bind to the intracellular portion of Na+ channels and prevent the entry of Na+ ions into the neuron
This prevents to propogation of an action potential along pain neurons in particular, meaning pain is not perceived
The LAs do not only work on pain fibres BUT small fibres (e.g. pain fibres) are more susceptible than large fibres
Nociceptors are most susceptible, followed by sympathetic fibres, temperature fibres and then motor fibres are least susceptible
Bupivacaine
One of the LAs
Useful for nerve blocks as it has a long duration of action (3-8hrs)
Used for local infiltration
Available with or without adrenaline - most commonly used without
Tetracaine
One of the LAs
Used as a topical anaesthetic on the cornea, aids examination
Also used before cannulation/ venepuncture in children
Proxymetacaine
One of the local anaesthetics
Used as a topical anaesthetic on the cornea - preferred to tetracaine for this purpose because it causes less stinging
Ester vs amide local anaesthetics
All LAs have a lipophilic and a hydrophilic portion - linked by a ‘linking group’ which is either an amide or an ester
Esters = less lipophilic due to higher pKa value
Esters = cross cell membrane less easily therefore slower onset of action
Esters: hydrolysed in the blood by plasma esterases (less stable)
Amides: hydrolysed in the liver (more stable)
Esterases act as immunogenics
Ester LAs do not contain an “i” in their name preceding “-caine.” Amide LAs contain an “i” in their name preceding “-caine.”
Factors that affect the efficacy of local anaesthetic
- Use of vasopressors e.g. adrenaline: reduces bleeding and systemic absorption of LA thus prolonging the effect of LA
- Inflamed/ infected tissue: more acidic environment meaning there is a reduced ability for the LA to penetrate the nerve cell membrane >> causes a reduced efficacy
Adverse effects of local anaesthetics
Allergy
Vasovagal syncope
Systemic toxicity
Discuss systemic LA toxicity
Toxicity occurs either due to overdose or inadvertent injection of LA directly into a blood vessel
First signs and symptomsare usually neurological e.g. numbness of mouth and tongue, slurred speech, tinnitus, confusion and drowsiness
Cardiovascular toxicity causes an initial tachycardia and HTN followed by hypotension and bradycardia and heart block
Tips for detecting LA toxicity
Keep talking to patient as you inject LA
Do not leave patient alone whilst anaesthesia develops
Management of LA toxicity
Stop procedure
- Call for help
- Clear and maintain airway and give 100% oxygen
- IV access
- Monitor ECG, BP, RR, HR, consciousness
- Seizures: lorazepam/ diazepam
- If patient does not respond to supportive measures, intralipid is given IV
- Maintain CPR during intralipid treatment (if appropriate)
Discuss the use of adrenaline with local anaesthetic
- Adrenaline is added to LA as a vasopressor (LA usually causes vasodilation) in order to reduce blood loss and increase duration of action of LA
- Adrenaline can also reduce risk of LA toxicity by delaying absorption e.g. bupivacaine + adrenaline is used for intercostal nerve blocks to decrease risk of toxicity in a relatively vascular area
Contraindications for use of adrenaline with LA
- Never used adrenaline for injections in the nose, ears, penis or in a Bier’s block
- Avoid use in or near flap lacerations as it can cause vasoconstriction and necrosis of the flap
- Do not use in digital nerve blocks because it can cause ischaemia and loss of digit
- Avoid in HTN, peripheral vascular disease, thyrotoxicosis, phaechromocytoma and those on beta blockers
Why don’t we use adrenaline in patients with phaeochromocytoma?
Phaeochromocytomas are catecholamine producing tumours
Adding more adrenaline into the mix isn’t a good idea
Why should we avoid adrenaline in patients with thyrotoxicosis?
Patients with hyperthyroidism already have overstimulation of systems that adrenaline works on e.g. HR, anxiety, palpitations
Can cause a hypertensive crisus, tachycardia anr/or arrhythmia
Tips for giving LA
- Lie patient down in a comfortable position with the site of injection accessible and supported – some patients faint if LA is given whilst they are sitting up
- Warm the local anaesthetic to body temperature before use
- Inject slowly to decrease pain, do not use force if there is any resistance to the injection, maintain conversation with the patient to help relieve anxiety and to detect signs of early toxicity
- Record in the notes the time and site of injection and the type and quantity of local anaesthetic given
Discuss use of topical anaesthesia
- Local anaesthetic apply directly to mucus membranes of the mouth, throat, urethra will diffuse through and block sensory nerve endings
- May take several minutes to work and the duration is relatively short because of the good blood supply
- Lidocaine gel is available for cleaning gravel burns but this is not advised as toxicity can occur and therefore general anaesthetic is recommended for cleaning large multiple gravel burns
- If gravel burns are not cleaned, tattooing can occur. Meaning the remains under the skin and re-epithelialisation occurs trapping the dirt
- EMLA cream is a mixture of lidocaine with prilocaine – is used to decrease the pain of an injection or cannulation. Must only be applied to intact skin, and that of Anastasia is slow usually taking around one hour I thick layer of cream is applied and covered with an occlusive dressing which is then left for one hour. A.k.a. magic cream in children
- Tetracaine gel is similar to EMLA cream but it acts within 30 to 45 minutes and causes vasodilation which aids venous cannulation
What is Bier’s block?
AKA intravenous regional anaesthesia
Local anaesthetic is injected intravenously and isolated from circulation in a target area
Torniquets are used to stop LA entering systemic circulation
Often used for minor surgery below the elbow and for reduction of Colle’s fractures
Uses a large dose of LA therefore toxic reaction would occur if the torniquets failed - hence the use of two
Most commonly used agent is prilocaine
What is sedation?
This is a continum ranging from being fully conscious through to unresponsive for most purposes the aim of sedation in A&E is to achieve minimal or moderate sedation
Outline the ASA classification of sedation depth
Minimal sedation/ anxiolysis: normal response to voice, airway, breathing and circulation unaffected
Moderate sedation/ analgesia: purposeful response to voice, airway maintained, breathing and circulation adequate
Deep sedation/ analgesia: purposeful response to painful or repeated stimuli, airway may need protecting and ventilation may need support
General anaesthesia: unrousable, airway requires intervention, ventilation inadequate and CV function may be impaired
What is rapid sequence induction?
Method of achieving rapid control of the airway
Involves inducing immediate unresponsiveness with an induction agent and muscular relaxation using a neuromuscular blocking agent
Allows for rapid tracheal intubation
Induction agents used for rapid sequence induction
Ketamine: useful in trauma RSI because it helps to maintain haemodynamic stability
Propofol
Etomidate
Fentanyl
Neuromuscular blocking agents used in rapid sequence induction
Rocuronium is the standard drug used - used to be suxamethonium but rocuronium has fewer contraindications
Propofol
Short acting, used for induction of GA
Rapid recovery so useful in day case surgery and manipulation of fractures or dislocations
Hypotension is common and bradycardia can occur
Also used for GA maintenance but less common
Etomidate
Agent used to induce GA
Less likely to cause hypotension than propofol so useful in those who are already hypotensive
Recovery is rapid
Injection is painful and can cause uncontrolled muscle movement
Discuss types of inhalational anaesthetics
- Can be used for analgesia, induction of anaesthesia and maintenance
- Entonox is used for analgesia
- Methoxyflurance is used in trauma
- Halothane, enflurane, isoflurane and sevoflurane are given using vaporisers
>> Halothane rarely used because risk of hepatotoxicity, also sensitises the heart to catecholamines so must not be used with adrenaline
>Inhaled anaesthetic drugs can cause malignant hyperthermia
Which specialty uses cocaine as a local anaesthetic?
ENT
Used in sinus surgery because it is a potent anaesthetic and vasoconstrictor
Which is the LA agent of choice used in regional anaesthesia?
Prilocaine
What is thiopental?
Barbiturate drug used for GA
Also functions as an anti-epeleptic
Types of inhalational anaesthetic
Gases
Volatile liquids
What is the most commonly used inhalational anaesthetic?
Sevoflurane - rapid onset of action and rapid recovery
Most common side effect of inhalational anaesthesia
Nausea
Treatment for malignant hyperthermia?
Dantrolene
Which inhaled anaesthetics are not used for induction?
Isoflurane
Desflurane
Strong odour - causes patients to hold their breath thus not inhale the anaesthetic
Discuss effects of general anaesthesia on the CV system
Decreases BP and CO
Most are negative inotropes and vasodilators
Most adults can tolerate a fall of 20% BP but if it remains low: elevate legs to increase preload, vasopressors, inotrope e.g. dobutamine
Discuss effects of spinal/ epidural anaesthetic on the CV system
Reduction in BP and CO, give IV fluid bolus to maintain preload and CO or give alpha agonist, atropine and fluids for moderate - severe hoTN
HoTN + bradycardia that remains > adrenaline
Surgical safety checklist WHO
Before anaesthesia:
Patient confirmed: identity, site, procedure, consent
Site marked
Anaesthesia safety checklist completed
Pulse oximeter on and functioning
Allergies/ difficult airway/ risk of >500ml blood loss
Before incision:
Introductions from team
Surgeon, anaesthetist, nurse confirm patient, site and procedure
Concerns: from surgeon? From anaesthetist? From nursing team?
Have antibiotics been given in last 60mins if appropriate?
Before patient leaves:
Nurse confirms: name of procedure performed, needle counts etc., labelling of any specimens, any equipment concerns
Surgeon, anaesthetist, nurse: review key concerns for the recovery of the patient
