Anaesthethics: Complications of Anaesthetics Flashcards
1
Q
Give some respiratory complications of general anaesthetics
A
1) Injury to lips, tongue, gum, dentition and other oral soft tissue structures
2) Injury to structures of glottis e.g. epiglottis, vocal cords and cartilage
3) Sore throat
4) Bronchospasm/laryngospasm
5) Aspiration of gastric contents
6) Injury to trachea, bronchial structures or alveoli
7) Pulmonary oedema
8) Pharyngeal obstruction
9) Hypoxia
10) PE (postoperative setting)
2
Q
What may injury to glottic structures result in?
A
Transient changes in voice, stridor, laryngospasm
3
Q
Who is bronchospasm and laryngospasm more common in in general anaesthetics?
A
1) Those with hyper-responsive airways e.g. asthma, recent respiratory tract infection.
2) Can also occur following aspiration of gastri contents during anaesthesia
4
Q
Presentation of bronchospasm and laryngospasm?
A
- hypoxia
- increased CO2
- reduced ventilation
- classical wheeze (bronchospasm)
- high pitched stridor (laryngospasm)
5
Q
Does a wheeze indicate bronchospasm or laryngospasm?
A
Bronchospasm
6
Q
Does a high pitched stridor indicate bronchospasm or laryngospasm?
A
Laryngospasm
7
Q
Who is at increased risk of aspiration of gastric contents in GA?
A
1) Non-fasted patients with increased intra-abdo pressure
2) Impaired lower oesophageal sphincter competence
3) Pregnant women
4) Obese individuals
5) Hiatus hernias
6) Impairment laryngeal reflexes
7) Reduced GCS
8
Q
Clinical features of aspiration of gastric contents in GA?
A
- bronchospasm
- laryngospasm
- hypoxia
- increased airway pressures: may collapse a lung lobe secondary to bronchial obstruction
- pneumonia
9
Q
How may injury to the trachea, bronchial structures or alveoli following an episode of anaesthesia present?
A
Subcutaneous emphysema or pneumothorax.
N.B. Pneumothorax may also result from the rupture of pre-existing bullae.
10
Q
When may pulmonary oedema occur in GA?
A
Pulmonary oedema may occur in patients following laryngospasm or airway obstruction, especially during the recovery phase from anaesthesia.
Inspiratory effort against the closed glottis leads to excessive negative pressure within the alveoli resulting in pulmonary oedema.
11
Q
When should you suspected pulmonary oedema after GA?
A
Pulmonary oedema should be suspected in hypoxic patients following laryngospasm.
12
Q
Presentatin of pulmonary oedema in GA?
A
- hypoxia following laryngospasm
- fine bi-basal crepitations
13
Q
Why is pharyngeal obstruction common in GA?
A
Due to sedation following anaesthesia, especially when using long-acting sedative agents.
14
Q
What condition may worsen pharyngeal obstruction in GA?
A
Obstructive sleep apnoea
15
Q
How can pharyngeal obstruction be identified?
A
Snoring
16
Q
Management of pharyngeal obstruction?
A
- basic airway manoeuvres
- place patient in lateral position
- overnight CPAP may be required following a general anaesthetic.
17
Q
What can cause hypoxia in GA?
A
Hypoxia is common among patients immediately following GA and is multifactorial:
- 2ary to anaesthetic agents and opioid analgesia
- atelectasis
18
Q
Who is more prone to hypoxia in GA?
A
- pre-existing respiratory disease
- obese patients
- patients following upper abdominal or thoracic surgeries
19
Q
What type of operations are more prone to hypoxia?
A
Abdo & thoracic surgeries
20
Q
Give some CVS complications of general anaesthetics
A
1) Hypotension
2) Arrhythmias
3) HTN
21
Q
Give some causes of hypotension following GA
A
1) Anaesthetic agents: can reduce the contractility of the heart and slow the heart rate –> However, the effects of most of these agents are short-lived, and other causes of hypotension should be considered.
2) Haemorrhage (resulting in hypovolaemia)
3) Reduced vascular tone
22
Q
If hypotension persists following GA despite initial management, what should be considered?
A
Other causes e.g. myocardial infarction, pulmonary embolism and pneumothorax
23
Q
Give some causes of arrhythmias following GA
A
Can be both bradycardia and tachycardia.
1) Post-op pain
2) Anxiety
3) Electrolyte imbalances
4) Cardiac surgery
5) Myocardial infarctions/ischaemia
6) Hypoxia/hypercarbia
7) Acid-base imbalances
8) Worsening of pre-existing arrhythmias
24
Q
Causes of HTN following GA?
A
1) Worsening of poorly controlled essential hypertension
2) Pain
3) Anxiety
4) Bladder distension
5) Fluid overload
6) Hypoxemia
7) Hypercarbia
8) Hypothermia
25
Give some genitourinary complications of general anaesthetics
1) AKI
2) Urinary retention
26
Acute kidney injury (AKI) is a common complication in the postoperative period.
How may it present?
1) Reduction in urine output
2) Worsening of metabolic parameters (e.g. acid-base balance and electrolyte imbalance)
27
Who is more at risk of developing urinary retention post GA?
- older patients
- BPH
- spinal anaesthesia
28
Give some GI complications of general anaesthetics
1) Post-op N&V
2) Ileus
29
What is post-operative nausea and vomiting (PONV) a direct complication of?
anaesthetic agents and opioid analgesics
30
Risk factors for PONV?
- female sex
- non-smokers
- post-op opioid use
- previous history of PONV
- type of surgery
- general anaesthesia
- volatile anaesthesia
31
What types of surgery are higher risk for PONV?
- laparoscopic surgery
- cholecystectomy
- gynaecological surgery
- middle ear surgeries
- squint corrections
32
What can be given to patients at high risk of PONV?
Prophylactic antiemetic drugs are usually given
33
Risk factors for post-op ileus?
- type of surgery: GI surgery, open repair of abdominal aortic aneurysms, and other surgical procedures where bowel handling may occur.
- use of opioids
- hyperkalaemia
34
Give some neuro complications of general anaesthetics
1) post-op cognitive dysfunction
2) peripheral nerve injuries (positioning-related)
35
What is postoperative cognitive dysfunction (POCD)?
A decline in cognition apparent after a patient recovers from the acute impact of surgery and hospital stay.
May present as acute delirium or be more subtle (e.g. memory impairment, difficulty comprehending etc.).
36
Risk factors for postoperative cognitive dysfunction?
- increasing age
- lower educational level
- cerebrovascular disease
37
What can cause peripheral nerve injuries?
prolonged durations in certain positions without appropriate preventive strategies.
38
Preventative measures to avoid injury to brachial plexus?
1) Avoid stretch or direct compression at the neck/axilla
2) Avoid using shoulder braces to support the Trendelenburg position.
3) Minimise shoulder abduction (aim <90 degrees) and avoid external rotation.
4) Avoid rotation and flexion of neck to the opposite side, try to keep head in neutral position throughout.
39
Preventative measures to avoid injury to radial nerve?
Avoid compression of the lateral humerus
40
Preventative measures to avoid injury to ulnar nerve?
Padding at the elbow, forearm supination, avoid elbow extension and extreme flexion.
41
Preventative measures to avoid injury to common peroneal nerve?
Pad lateral aspects of the upper fibula, avoid extreme lithotomy position and avoid lithotomy position for more than 2 hours
42
Inadvertent perioperative hypothermia (IPH) is a common consequence of general and regional anaesthesia.
What is IPH defined as?
Core body temp <36 degrees.
43
Who is at a higher risk of develoing hypothermia during anaesthesia?
- high ASA grade
- combined regional & general surgery
- emergency major surgery
- low BMI
44
Adverse effects of IPH?
- surgical site infection
- coagulopathy
- increased transfusion requirements
- pain
- altered drug metabolism
- adverse cardiac events.
45
Preventative measures to avoid IPH?
1) Keeping patients warm during the pre-operative phase
2) Active warming during the intraoperative phase with fluid warmers and forced air warming blankets
3) Keeping the patient covered during the recovery
46
Give 3 key complications of regional anaesthesia
1) Post-dural puncture headache (PDPH)
2) Peripheral nerve injuries
3) Neuro complications following central neuraxial blocks (CNB)
47
What is a post-dural puncture headache (PDPH)?
Occurs following an intentional dural puncture (with a spinal needle) or unintentional dural puncture (with an epidural needle).
The leak of CSF through the dural defect causes intracranial hypotension leading to traction on intracranial structures.
48
When does PDPH typically occur?
72 hours after dural puncture
49
Describe headache in PDPH
- usually frontal or occipital
- worsened by standing or sitting up
- relieved by lying down
50
Management of PDPH?
1) refer to anaesthetic team
2) exclude other causes of acute headache
3) bed rest
4) adequate hydration
5) avoiding situations which would give rise to an increase in intracranial pressure
6) simple analgesics
7) epidural blood patch: can be performed if headache persists
51
What are the major neurological complications following CNB?
1) cord damage: direct injury to the spinal cord or nerve roots caused by a needle or catheter, toxicity caused by local anaesthetic agents
2) cord ischaemia: anterior spinal artery syndrome
3) cord compression: haematoma due to needle trauma, vascular anomaly, spinal tumour, coagulation disorder/anticoagulants
4) abscess: exogenous infections via needle or haematogenous spread
5) meningitis
52
What is post-op ileus (sometimes referred to as paralytic ileus)?
After what operations does it typically occur?
A common complication after surgery involving the bowel, especially surgeries involving extensive handling of the bowel.
There is reduced bowel peristalsis resulting in pseudo-obstruction.
53
Features of post-op ileus?
- abdominal distention/bloating
- abdominal pain
- nausea/vomiting
- inability to pass flatus
- inability to tolerate an oral diet
54
What can contribute to the development of post-op ileus?
Deranged electrolytes: important to check potassium, magnesium and phosphate.
55
Management of post-op ileus?
1) nil-by-mouth initially, may progress to small sips of clear fluids
2) NG tube if vomiting
3) IV fludis to maintain normovolaemia: additives to correct any electrolyte disturbances
4) total parenteral nutrition: occasionally required for prolonged/severe cases
56
What is an anaesthetic machine?
This machine generates, mixes & delivers a flow of medical gases and inhalational anaesthetic agents to the patient to induce and maintain anaesthesia.
57
What are the medical gases used in anaesthetics?
oygen, medical air & nitrous oxide
58
What are vaporisers used for in anaesthetics?
‘Volatile’ anaesthetic agents (isoflurane, desflurane, and sevoflurane), used for the maintenance of general anaesthesia, are liquids at room temperature and thus require a vaporiser for inhalational administration.
59
What is an anaesthetic vaporiser?
A device generally attached to an anaesthetic machine that delivers a known concentration of a volatile anaesthetic agent to the patient.
Works by controlling the vaporisation of the liquid agent and then accurately calibrating the concentration of the agent, which is added to the fresh gas flow (oxygen and medical air) for delivery to the patient.
60
What is an anaesthetic 'breathing circuit'?
An arrangement of tubes and other components that transports gases between the anaesthetic machine and the patiet.
61
What is the most common breathing system used in modern anaesthesia?
The 'circle system'
62
Advantages of the 'circle system'?
1) Preserves anaesthetic gases, making volatile anaesthesia more cost-effective
2) Preserves heat and moisture
3) It is a closed-circuit system which reduces fire risk
63
An anaesthetic breathing circuit contains a reservoir bag.
What is this for (2 reasons)?
1) for monitoring the patient’s respiration and ventilating the patient if required
2) also acts as a gas reservoir, protecting the patient from excessively high pressures within the breathing system.
64
What is the adjustable pressure-limiting (APL) valve on an anaesthetic breathing circuit?
When is it used?
Generally only used during a) spontaneous, or b) manual ventilation.
65
How does the APL work in spontaneous breathing?
During spontaneous breathing, the valve is left fully open, and gas flows through the valve during exhalation.
66
How does the APL work in manually assisted ventilation?
When manually assisted ventilation is used, the APL valve should be closed enough to achieve the desired inspiratory pressure.
67
At the ‘patient end’ of the anaesthetic breathing system, what is there?
A heat and moisture exchange (HME) filter
68
Purpose of an HME filter in the breathing system?
Warms and humidifies inspired gases by conserving exhaled heat and moisture.
69
How is carbon dioxide removed from the breathing system?
As the ‘circle system’ requires re-breathing of expired gases, carbon dioxide is actively removed from the circuit via a soda lime canister.
70
Purpose of suction apparatus in anaesthetics?
clear mucus, saliva, blood & debris from the pharynx, trachea and main bronchi.
71
Role of anaesthetic ventilators?
Assist patients’ breathing during surgery or other procedures requiring anaesthesia.
72
When is a ventilator required in anaesthesia?
Patients with endotracheal tubes or supraglottic devices (laryngeal mask airway / i-gel®) in place.
73
What does the ventilator deliver to the patient?
The ventilator delivers a mixture of gases (oxygen and medical air) to the patient and a set concentration of volatile anaesthetic agent.
74
What basic monitoring equipment is used in anaesthesia?
1) cardiac monitor to track heart rhythm and rate
2) pulse oximetry
3) non-invasive BP monitoring
4) capnography: to monitor carbon dioxide levels in exhaled breath
5) gas analysers in the anaesthetic machine: to measure the concentration of inhaled and exhaled gases, as well as the RR
6) equipment to measure a patient’s temperature
75
What vital information can a capnograph provide?
By monitoring the end-tidal carbon dioxide levels: can detect changes in ventilation e.g. respiratory depression or obstruction.
76
What methods are used to monitor temp in anaesthetics?
1) tympanic thermometer
2) oesophageal probes
77
How can anaesthesia and surgery affect body temp?
Anaesthesia (and surgery) can increase a patient’s susceptibility to hypothermia
78
What complications can hypothermia during surgery cause?
1) longer recovery time
2) delayed wound healing
3) higher infection rates
79
What is used in anaesthesia to help prevent hypothermia?
Warming apparatus e.g. forced air warmers, IV fluid warmers (i.e. to heat cold IV fluids to body temp)
80
What are forced air warmers?
Forced air warmers deliver warm filtered air through a hose to a special blanket, creating a convective air current to warm the patient.
81
Role of infusion pumps in anaesthetics?
Various infusion pumps are used in anaesthesia to deliver controlled amounts of fluids, medications, and anaesthetic agents, and to ensure precise and timely administration of substances.
82
What is total intravenous anaesthesia (TIVA)?
An anaesthetic technique whereby all of the patient’s anaesthetic agents are delivered intravenously without the use of inhalational agents.
83
What are 'giving sets' in anaesthesia?
Giving sets are used in anaesthesia to deliver fluids (crystalloids and colloids), medications, and blood products to a patient.
84
What are the 4 main components of a giving set?
1) drip chamber
2) tubing
3) roller clamp
4) connectors
85
What is a drip chamber in a giving set?
a transparent chamber between the tubing and the spike, which allows visual monitoring of the flow rate
86
Purpose of a roller clamp in a giving set/drip line?
used to adjust the flow rate of fluid through the drip line
87
What does neuraxial anaesthesia involve?
Involves the injection of anaesthetic agents into the subarachnoid or epidural space to produce an anaesthetic block.
88
What does 'thermoregulation in the perioperative period' refer to?
The temperature management of patients from 1 hour prior to their surgery until 24 hours after the surgery has been completed.
89
Is perioperative hypo- or hyperthermia more common?
Hypothermia
90
Risk factors for perioperative hypothermia?
1) ASA grade of 2 or above
2) Major surgery
3) Low body weight
4) Large volumes of unwarmed IV infusions
5) Unwarmed blood transfusions
91
Define the pre-operative phase
Starting 1 hour before induction of anaesthesia
92
The patient's temperature should be measured in the pre-operative phase.
What should you do if:
a) patient's temp is <36 degrees
b) >/= 36 degrees
a) active warming should be commenced immediately
b) acceptable to start warming 30 minutes prior to anaesthetic induction.
93
Should patients be moved to the theatre suite if their temperature is less than 36.0ºC?
No - unless they have a time critical condition that requires urgent management.
94
When should forced air warming devices (e.g. 'Bair Hugger') be used during the intra-operative phase?
From the onset of anaesthesia for any patient with:
a) an anaesthetic duration of >30 minutes or
b) for patients at high risk of perioperative hypothermia regardless of anaesthetic duration.
95
At what volume should IV fluids be warmed prior to administration?
Fluid volumes of >500ml (as should all blood products).
N.B. whilst this prevents further heat loss, it will not correct existing hypothermia.3
96
What is intra-operative hyperthermia typically due to?
Over-warming
97
How often should patient's temp be measured in the post-op period?
Following transfer to the recovery room the patient's temperature should be documented initially and then repeated every 15 minutes until transfer to the ward.
98
How can perioperative hypothermia cause coagulopathy?
Hypothermia reduces blood's ability to clot, causing increased intra-operative blood loss.
99
How can perioperative hypothermia cause prolonged recovery from anaesthesia?
Small decreases in body temperature can cause drastic prolongation of anaesthetic drugs, both neuromuscular blocking agents (NMBAs), propofol and inhalational agents.
100
How can peri-operative hypothermia cause reduced wound healing?
Hypothermia leads to local vasoconstriction which reduces perfusion to the skin, this reduces the necessary immune moderators available at the site to promote healing.
101
How can peri-operative hypothermia predispose to infection?
A combination of poorer incisional site healing and also reduced number of immune cells able to access the skin leads to a significantly increased risk of infection.
102
What are the dangers of shivering (a complication of perioperative hypothermia)?
It can cause a significant increase in metabolic rate which can in certain patient groups even result in myocardial ischaemia.
103
What is laryngospasm?
The complete or partial reflex adduction of the vocal cords due to the involuntary contraction of the intrinsic muscle of the larynx.
This may cause a variable degree of upper airway obstruction.
Closure of the glottic opening is a primitive protective airway reflex to prevent aspiration.
104
What are some anaesthetic-related risk factors that can increase the risk of laryngospasm?
1) Insufficient depth of anaesthesia
2) Mucous or blood in the peri-glottic area
3) Airway manipulation (laryngoscopy, suction)
105
What are some patient-related risk factors that can increase the risk of laryngospasm?
1) Age (young children at greatest risk)
2) Airway hyperactivity (asthma, smokers)
3) Recent upper respiratory tract infection (up to 6 weeks prior)
4) GORD
106
What are some surgical-related risk factors that can increase the risk of laryngospasm?
1) Upper airway surgery (tonsillectomy)
2) Thyroid surgery (superior laryngeal nerve injury)
107
Typical signs of laryngospasm?
1) Stridor
2) Abnormal see-saw movements of the abdominal and chest wall in a spontaneously breathing patient
108
Management of laryngospasm?
1) Removal of the stimulus (e.g. removal of blood clots by suctioning, removal of supraglottic airway device)
2) Calling for senior anaesthetic help
3) 100% FiO2, high-flow oxygen using a face mask
4) Application of positive end-expiratory pressure (PEEP)
5) Deepening of anaesthesia with propofol
If the above measures do not work, patients will require suxamethonium (a depolarising muscle relaxant) to relax the vocal cords and endotracheal intubation. Caution should be taken on extubation as laryngospasm may recur.
109
Complications of laryngospasm?
1) Desaturations and hypoxia
2) Negative pressure pulmonary oedmea
3) Bradycardia (in children)
110
What mutation is seen in malignant hyperthermia?
A genetic mutation affects the ryanodine receptor of the sarcoplasmic reticulum in skeletal muscles.
This results in raised intracellular calcium ions leading to prolonged muscle contraction.
111
Signs of malignant hyperthermia?
1) Masseter spasm
2) Generalised prolonged muscle rigidity
3) Increasing end-tidal CO2 (EtCO2)
4) A rapid increase in core body temperature
5) Rhabdomyolysis leading to acute renal failure
6) Hyperkalaemia, which may lead to arrhythmias
112
How can malignant hyperthermia affect potassium?
Can cause hyperkalaemia
113
Complications of malignant hyperthermia?
1) Hyperkalaemia
2) Acute renal failure
3) Life-threatening arrhythmias
114
What is anaphylaxis?
Anaphylaxis is an acute, life-threatening type 1 hypersensitivity reaction involving the activation of IgE-bound mast cells and basophils on exposure to a previously sensitised antigen.
115
What are 3 common anaphylaxis triggers in the field of anaesthetics?
1) Abx
2) Muscle relaxants
3) Latex
116
Management of anaphylaxis?
1) Stop the administration of the suspected causative drug
2) Call for help
3) Apply 100% FiO2 oxygen (consider intubation if necessary)
4) Administer 0.5ml of 1: 10,000 adrenaline IV, or if there is no peripheral access 0.5 ml of 1:1,000 adrenaline IM. Repeat the dose every 5 minutes as necessary.
5) IV fluid resuscitation with crystalloids 10-20ml/kg boluses to maintain mean arterial pressure
117
Dose of adrenaline for anaphylaxis IV?
0.5ml of 1:10,000
118
Dose of adrenaline for anaphylaxis IM?
0.5ml of 1:1000
119
What is local anaesthetic toxicity?
Local anaesthetic toxicity is a life-threatening event that may occur after administering local anaesthetic (LA) agents leading to cardiorespiratory and central nervous system instability.
120
What is a common cause of local anaesthetic toxicity?
1) Accidental intravascular injection of local anaesthetics.
2) Comorbidities such as liver, cardiac and renal disease may reduce LA clearance, leading to accumulation in the body.
121
How can the site of LA affect the risk of LA toxicity?
Certain sites have an increased risk of rapid systemic absorption and toxicity due to the injection being in a highly vascularised area.
Most common --> intercostal block
122
Give the maximum doses of the following LA:
1) Lidocaine without adrenaline
2) Lidocaine with 1:100,000 adrenaline
3) Bupivacaine
4) Prilocaine
1) 3mg/kg
2) 7mg/kg
3) 2mg/kg
4) 6mg/kg
123
Clinical features of LA toxicity?
1) Sudden onset of altered mental status, tonic-clonic seizures, agitation or coma
2) Cardiac arrest
3) Tachyarrhythmias or bradyarrhythmias
4) Perioral tingling and numbness
124
Management of LA toxicity?
1) Stop injecting the local anaesthetic
2) Call for help
3) Maintain airway (consider intubation if necessary)
4) Supply 100% oxygen and ensure adequate lung ventilation (aim for hyperventilation to raise pH because of metabolic acidosis)
5) Seizures: can be treated with benzodiazepines (e.g. lorazepam) or small boluses of propofol or thiopentone appropriate to the patient’s weight
6) Start lipid emulsion therapy. A bolus dose of 1.5ml/kg of intralipid 20% should be given in 1 minute. After bolus injection, start intralipid 20% infusion at 15ml/kg/hr. The bolus can be repeated up to 3 times until cardiovascular stability is achieved.
7) Transfer to intensive care for ongoing cardiac monitoring
125
