Anaesthetics Flashcards
Why doe sthe patient need to be fasted before general anaesthetic
Reduces the reflux of stomach contents into oropharynx (throat) then aspiration into trachea
How does reflux then aspiration lead to pneumonia
gastric contents in lungs creates aggressive inflammatory response
leads to pneumonitis - inflammation of lung tissue
then aspiration pneumonia
When is there the highest risk of aspiration during general anaesthetic
before, during intubation
at extubation
what are the fasting rules for operations under general anaesthetic
6 hours no food or feeds
2 hours no clear fluids - fully nil by mouth
What is preoxygenation
100% oxygen for a few minutes before being put under so they have a reserve for the period when they lose consiousness and are successfully intubated and ventilated
in case they are difficult to intubate or anaesthetist has difficult
What are the three classic classes of medications that patients may be given before anaesthetics
Benzodiazepines - relax muscles and reduce anxiety - midazolam
Opiates - fentanyl / alfentanyl - reduce pain and hypertensive response to laryngoscope
Alpha-2-adrenergic agonists - clonidine - help sedation and pain
What is used in emergency scenarios to get control of the airway
rapid sequence induction/intubation
What maneouvres can be used to prevent aspiration in RSI?
press down on cricoid cartilage (cricoid pressure) to press the oesophagus down
Position the patient pore upright
What is the triad of general anaesthesia
Hypnosis
muscle relaxation
analgesia
How can hypnotic agents be delivered
intravenous
inhalation
What do hypnotic agents do
make the patient unconscious
What are the intravenous options for hypnotic agents
propofol (most common)
ketamine
thiopental sodium (less common)
etomidate (rare)
What are the inhaled option for general anaesthetic
Sevoflurane (most common)
Desflurane (less favourable - bad for environment)
Isoflurane (rare)
Nitrous oxide (kids)
What are volatile anaesthetic agents
liquids at room temperature and need to be vapourised into a gas to be inhaled
e.g. sevoflurane, desflurane and isoflurane
What acts quicker, inhaled or IV general anaesthetic agents?
IV agents
Commonly, an intravenous medication will be used as an induction agent (to induce unconsciousness), and inhaled medications will be used to maintain the general anaesthetic during the operation. Inhaled medications need to diffuse across the lung tissue and into the blood, where it takes a while for them to reach an effective concentration. IV agents have a head start, as they are infused directly into the blood and so can quickly reach an effective concentration.
What is TIVA?
Total intravenous anaesthetia used for induction and maintenance - most commonly propofol
nicer recovery compared with inhaled options
What are the two classes of muscle relaxants
Depolarising
Non-depolarising
What are some examples of muscle relaxants?
Suxamethonium (depolarising)
Rocuronium and Atracurium (Non-depolarising)
What is the purpose of muscle relaxants in general anaesthetic?
To relax and paralyse muscles
Makes surgery and intubation easier
How can you reverse muscle relaxants
Neostigmine - cholinesterase inhibitor for depolarising muscle relaxants - for suxamethonium
Sugammadex for non-depolarising ones - rocuronium and vecuronium
Where do muscle relaxants act?
At the neuromusclular junction - Acetylcholine is blocked from stimulating a response from the muscle
Which opiates are most frequently used
Fentanyl
Alfentanil
Remifentanil
Morphine
Which antiemetics are given post-procedure for prophylaxis
Ondansetron
Dexamethasone
Cyclizine
What class of drug is ondansetron
5HT3 receptor antagonist
When is ondansetron avoided
in patients with a risk of prolonged QT interval
When should dexamethasone be avoided
in diabetics or immunocompromised patients
What class of drug is cyclizine
Histamine (H1) receptor antagonist
When should cyclizine be avoided
Elderly patinets and heart failure
How can you test if the muscle relaxant has worn off
Nerve stimulator
Ulnar nerve - thumb movements / twitches
Facial nerve stimulation for orbiulares oculi muscle movement (stimulate four times - Train-of-four)
What is the Train-of-Four stimulation
nerve is stimulated four times
if it remains strong, muscle relaxant has worn off
If it weakens, it hasn’t worn off
Medication can be used to reverse the effects of the muscle relaxant
Whata re the risks of general anaesthesia
Accidental awareness (waking during the anaesthetic)
Aspiration
Dental injury, mainly when the laryngoscope is used for intubation
Anaphylaxis
Cardiovascular events (e.g., myocardial infarction, stroke and arrhythmias)
Malignant hyperthermia (rare)
Death
What is malignant hyperthermia
Fatal hypermetabolic response to anaesthesia
Which drugs have a higher risk of causing malignant hyperthermia
Volatile anaesthetics (isoflurane, sevoflurane and desflurane)
Suxamethonium
Antipsychotics - NMS
What are some signs of malignant hyperthermia
Increased body temperature (hyperthermia)
Increased carbon dioxide production
Tachycardia
Muscle rigidity
Acidosis
Hyperkalaemia
How cna you treat malignant hyperthermia
Dantrolene
How does dantrolene work
Interupts the msucle rigidity and hypermetabolism by interfering with movement of calcium ions in skeletal muscle
What is central neuraxial anaesthesia
it is a spinal anaesthetic / spinal block
What is central neuraxial anaesthesia used for
Hip fracture repairs
Transurethral resection of the prostate
C-sections
Into which area is the anaesthetic injected for central neuraxial anaesthesia?
Subarachnoid space into CSF
Usually into L3/4 or L4/5
How long will it take for central neuraxial anaesthesia to wear off
1-3 hours
What is epidural anaesthesia and when is it used?
in pregnant women in labour and post-operatively after a laparotomy
What medication is used in epidural anaesthesia?
Levobupivicaine with or without fentanyl
Where is the epidural anaesthetic injected
into the epidural space
outside the dura mater, separate from the spinal cord and CSF
What are some adverse effects of epidurals
Headache if the dura is punctured, creating a hole for CSF to leak from (“dural tap”)
Hypotension
Motor weakness in the legs
Nerve damage (rare)
Infection, including meningitis
Haematoma (may cause spinal cord compression)
What are some dangers of epidural in pregnancy
Prolonged second stage
Increased probability of instrumental delivery
What is allodynia
pain is experienced with sensory inputs that don’t cause pain
How do you treat local anaesthetic toxicity
IV 20% lipid emulsion
What does pain threshold mean
It’s the point at which a sensory input is reported as painful, e.g. temperature applied to akin to measure the pain at which the heat is interpretted as pain
What is a pain tolerance
a person’s response to pain
biological, psychological and social factors
What are the two groups of nerve fibres that transmit pain
C fibres - unmyelinated and small diameter
A-delta fibres - myelinated and larger diameter
How do C-fibres transmit pain
Slowly and they produce a dull and diffuse pain sensation
How do A-delta fibres transmit pain
Fast and they produce a sharp and localised pain sensation
Up which spinal tracts does pain get transmitted?
Spinothalamic and spinoreticular tract
Where in the brain is pain interpreted
Thalamus and cortex
What is neuropathic pain
Abnormal functioning or damage of the sensory nerves
What are some features of neuropathic pain
Burning
Tingling
Pins and needles
Electric shocks
Loss of sensation to touch of the affected area
What are the two common scales to measure pain
Numerical rating scale (NRS)
Visual analogue scale (VAS)
What are the three steps of the WHO analgesic ladder
Step 1: Non-opioid - paracetamol and NSAIDs
Step 2: Weak opioids - codeine and tramadol (tramadol has multiple mechanisms of action, including being an SNRI and agonist of opioid receptors)
Step 3: Strong opioids - morphine, oxycodone, fentanyl and buprenorphine
Which medications can be used for neuropathic pain, or as adjuvants with the analgesic ladder?
Amitriptyline - TCA
Duloxetine - SNRI
Gabapentin - anticonvulsant
Pregabalin - anticonvulsant
Capsaicin cream (topical) - from chilli peppers
What are the main side effects of NSAIDs
Gastritis with dyspepsia (indigestion)
Stomach ulcers
Exacerbation of asthma
Hypertension
Renal impairment
Coronary artery disease, heart failure and strokes (rarely)
Contraindications of NSAIDs
Renal failure
Asthma
Heart disease
Uncontrolled HTN
Stomach ulcer
Side effects of opioids
Constipation
Skin itching (pruritus)
Nausea
Altered mental state
Respiratory depression
What medication is used to reverse opioids
Naloxone
How do you calculate the rescue dose of an opioid for somone in chronic pain?
Rescue does is 1/6 of the background 24-hour dose
How is subcut opioid dose converted to IV?
IV is 1/10 the dose of subcut
Which opioids can be given as patches?
Buprenorphine (5mcg = 12mg oral morphine)
Fentanyl (12mcg = 20mg of oral morphine)
What needs to be on-hand when administering patient-controlled anaesthesia
Naloxone - resp dep
Antiemetics - nausea
Atropine - bradycardia
What options are there for managing chronic pain (NICE guidelines 2021)
Supervised group exercise programs
Acceptance and committment therapy (ACT)
CBT
Acupuncture
Anidepressants (amitriptyline, duloxetine or SSRI)
Which medications should patients not be started on for Chronic Primary Pain?
Paracetamol
NSAIDs
Opiates
Pregabalin
Gabapentin
What medications can be used in chronic secondary pain?
- Paracetamol and topical NSAIDs
- Oral NSAIDs +/- PPI
- Opiates - e.g. codeine
What questionnaire is used to assess neuropathic pain
DN4 questionnaire
What is the first-line medication for trigeminal neuralgia?
Carbamazepine - refer to specialist if this doesn’t work
What is the standard ET tube size for men and women
7 - 7.5 mm for women
8 - 8.5 mm for men
What can be used to check the pressure in the cuff of an ET tube?
Manometer
What part of the tube can provides security in the event that the main opening at the tip of the ETT becomes occluded?
Murphy’s eye - an extra hole in the side of the tip that gas can flow through
What is a laryngoscope with a camera called?
McGrath laryngoscope
What can be used to assist intubation if the vocal cords cannot be visualised?
Bougie
The bougie is inserted into the trachea. The endotracheal tube slides along the bougie into the correct position in the airway. The bougie is then removed, and the endotracheal tube remains in place.
What is the name given to pain and restriction in opening the jaw
Trismus
What types of supraglottic airway devices are there?
Inflatable cuff SADs = laryngeal mask airways
Non-inflatable SADs = I-gel (moulds to the larynx)
What is a guedel
an oropharyngeal airway
What is a contraindication for inserting a nasopharyngeal airway
Base of skull fracture
How do you measure the correct size for a OPA and NPA?
OPA = from centre of mouth to angle of jaw
NPA = edge of the nostril to the tragus of the ear
What are the stages to do in the cases of an unanticipated difficulty intubating a patient according to the Difficult Airway Society (DAS) guidelines 2015?
Plan A – laryngoscopy with tracheal intubation
Plan B – supraglottic airway device
Plan C – face mask ventilation and wake the patient up
Plan D – cricothyroidotomy
Why would you want an arterial catheter
Measuring blood pressure real-time
ABG samples
Where is a central venous catheter inserted?
Internal jugular vein
Subclavian vein
Femoral vein
Where does the tip of the CVC sit?
vena cava
Which medications would need to be given through a CVC?
inotropes
amiodarone
high-potassium fluids
What are Swan-Ganz catheters?
Pulmonary artery catheters
What is used to monitor pulmmonary artery wedge pressure?
Pulmonary artery catheter
What is a portacath?
central venous catheter
There is a small chamber (port) under the skin at the top of the chest that is used to access the device. This chamber is connected to a catheter that travels through the subcutaneous tissue and into the subclavian vein, with a tip that sits in the superior vena cava or right atrium.
The port can be seen as a bump on the chest wall and felt through the skin
a needle is inserted through the skin into the port, allowing injections to be given or infusions to be set up
Which type of CVC lasts the longest?
Portacath
low chance of infection, fully internalised under the skin
What scoring systems can predict mortality at time of admission to ICU
APACHE (Acute Physiology and Chronic Health Evaluation)
SAPS (Simplified Acute Physiology Score)
MPM (Mortality Prediction Model)
What are the types of respiratory failure?
- Low PaO2 indicates hypoxia and respiratory failure
- Normal pCO2 with low PaO2 indicates type 1 respiratory failure (only one is affected)
- Raised pCO2 with low PaO2 indicates type 2 respiratory failure (two are affected)
What does a raised bicarbonate indicate?
Chronic CO2 retention - COPD patients
Why do patients in acute exacerbation of COPD become acidotic?
Kidneys cannot keep up with rising level of CO2
The patient then becomes acidotic despite having higher bicarb than someone without COPD
In respiratory alkolosis, how can you differentiate between hyperventilation syndrome and PE?
PE = low PaO2
Hyperventilation syndrome = high PaO2
When will there be a reduced bicarbonate?
Renal failure
Type 2 renal tubular acidosis
Diarrhoea
Which patients will get metabolic alkalosis?
Loss of H+ ions
Increased activity of aldosterone in kidneys
Vomiting - stomach produces HCl
Which conditions cause an increased activity of aldosterone?
Conn’s syndrome
Liver cirrhosis
Heart failure
Loop diuretics
Thiazide diuretics
What electrolyte abnormality can suxamethonium cause
Hyperkalaemia
How does lidocaine work
Blocks sodium channels
When might suxamethonium be contraindicated
Hyperkalaemia
Penetrating eye injury
Acute narrow angle glaucoma
What intervention reduces incidence of intra-abdominal lesions
Laparoscopic approach over open surgery
What monitoring equipment measures the concentration of CO2 exhaled during intubation
Capnography
What is the likely organism in a wound infection post-surgery?
Staph aureus
Should COCP / HRT be stopped before surgery? If so, when?
Stopped 4 weeks before surgery
What might be the cause of isolated fever in a patient 24hrs post surgery
Physiological response to surgery
What two differentials would you want to exclude in a patient presenting with pyrexia 24hrs post surgery?
Thrombosis
Infection
At what time frame would a wound infection present post-operatively?
48 hrs
What is the medication of choice for rapid sequence induction?
Suxamethonium
At what BMI are patients classed ASA II?
30 - 40
When is the “time out” stage of the WHO checklist
Before the first skin incision is made
What is the imaging modality used in an anastomotic leak
Abdo CT
Which anaesthetic agent has inherent anti-emetic properties?
Propofol
How should total parenteral nutrition be administered?
Subclavian line
Because it is strongly phlebitic
If a patient has diabetes, what management protocol is normally used for surgery?
Put them first on the list
Prevents complications of poor BM control
What complication can occur in long-term mechanical ventilation in trauma patients?
Tracheo-oesophageal fistula
What is the inheritance pattern in malignant hyperthermia
50%
When should dalteparin sodium be started for VTE prophylaxis
at least 6 hours post surgery
Which induction agent should be used in trauma patients to avoid drops in BP?
Ketamine - doesn’t cause a drop in BP
What should be used to clean surgical wounds 0-48hrs post-surgery
Sterile saline
After how many hours post-surgery may a patient shower safely?
48 hours
