Anaesthetics Flashcards
State the fasting durations prior to surgery
- No food for 6 hours prior to surgery
- No clear fluids 2 hours prior to surgery
Outline 3 pre-medications that may be used by anaesthetics just before surgery and their role
Benzodiazepines - reduce anxiety and relax muscles (especially in cardiac surgery where sympathetic drive can influence surgery itself)
Opiates - reduce pain and reduce hypertensive response to laryngoscope
A2 receptor agonists - reduce pain and sedation
Outline 3 components to anaesthesia and examples of drugs used in each component
HAM
- Hypnosis - make patient unconscious
e.g. Propofol (IV), Ketamine (IV), nitrous oxide (inhaled) flurane gases (inhaled) - Analgesia - reduce pain
e.g. Fentanyl and Morphine
Also requires antiemetics e.g. Ondansetron, Dexamethasone - Muscle relaxants - reduce muscle tone
e.g. Sugammadex
Outline some risks of general anaesthesia
Common:
- Sore throat
- Nausea and vomitting
Significant risks:
- Aspiration
- Dental injury
- Accidental awakeness
- Cardiovascular events e.g. MI, stroke
- Anaphylaxis
- Malignant hyperthermia
- Death
Give 3 examples of when a spinal block may be used
- Cesarean section
- TURP procedure (transurethral resection of the prostate)
- Hip fracture repairs
Explain the difference between spinal and epidural block and when each would be used
Spinal block goes into the subarachnoid space, directly into the CSF
- Acts on both muscle and nerve fibres
- Used for cesarean section, TURP procedure and hip surgery
Whereas the epidural goes into the epidural space
- Acts on nerve fibres alone and local anaesthetic diffuses to local tissues and through to the spinal cord
- Used for labour and post-operative open surgery (laparotomy)
Outline some risks of an epidural during labour
- Maternal hypotension leading to foetal and maternal distress
- Dural puncture leading to a severe postural headache
- Epidural haematoma and potentially cauda equina syndrome
For the following lines, explain how they work and what they are used for
- Arterial line
- Central line / central venous catheter
- Vas cath
- PICC line
- Tunnelled central venous catheter (e.g. Hickmann line)
- Pulmonary artery catheter
- Portacath
Arterial line:
- Inserted into an artery e.g. radial artery
- Can be used to monitor blood pressure and take regular ABGs
Central line / central venous catheter:
- Inserted into a large vein with the tip leading into the vena cava (can use internal jugular, subclavian or femoral veins)
- Used for giving medications or blood samples
- Last longer and are more reliable than peripheral cannulas and are better for irritating medications such as inotropes
Vas cath:
- Type of central venous catheter
- Specifically used short term for haemodialysis
PICC line:
- Type of central venous catheter
- Peripherally inserted venous catheter which then leads to the central point (vena cava)
Tunnelled central venous catheter (e.g. Hickmann line):
- Enters through subcutaneous tissue then into the veins (subclavian or jugular) and tip sits in vena cava
- Cuff surrounds the catheter and promotes surrounding healing leading to reduced bacterial infection
- Can be used long term so are good for regular IV treatment
Pulmonary artery catheter:
- Inserted into central venous system and balloon wedges it into branch of pulmonary artery
- Helps to detect pressures in the left atrium for close cardiac monitoring in cardiac centres
Portacath:
- Type of central venous catheter
- Small port under the skin at the top of the chest, used for access (skin remains intact when not needed)
- Tip sits in vena cava or right atrium
- Can be used long term so are good for regular IV treatment
Explain the difference between C-fibres and A-delta fibres
C-fibres:
- Small diameter and unmyelinated
- Transmit signals slowly
- Produces dull and diffuse pain sensations
A-delta fibres
- Large diameter and myelinated
- Transmit signals quickly
- Produces sharp and well-localised pain sensations
Describe our best methods used to measure pain
Although there is no reliable way to reliably measure pain, 2 ways we can try to quantify pain:
- Numerical analogue scale
- Ask patient to grade pain out of 10 - Visual rating scale
- Ask patient to rate their pain along a horizontal line
Can also use graphical representation of pain in faces for:
- Children
- Learning difficulties
State the WHO analgesic ladder and give examples of drugs in each category
Step 1:
- Non opioid medications (e.g. Paracetamol and NSAIDs)
Step 2:
- Weak opiates (e.g. Tramadol, Codeine)
Step 3:
- Strong opiates (e.g. Morphine, Fentanyl)
List some adjuvant medications that can be used alongside WHO analgesic ladder (good for neuropathic pain)
- Amitriptyline
- Gabapentin
- Pregabalin
- Duloxetine
- Capsaicin cream (topical)
List some side effects of NSAIDs
- Gastric ulcers, gastritis and dyspepsia
- Renal impairment
- Exacerbation of asthma
- Hypertension
List some contraindications for NSAIDs
- Asthma
- Stomach ulcers
- Uncontrolled hypertension
- Heart failure
- Renal impairment
- Heart disease
List some side effects of opiates
- Constipation
- Respiratory depression
- Nausea and vomitting
- Altered mental state (e.g. confusion, sedation)
- Pruritus
State medication used to reverse effects of opiates in life threatening overdose
Naloxone
State how you would calculate a rescue dose of opiates
Rescue dose is 1/6 of their 24 hour background dose
State what system is used for the assessment of patients for anaesthetic prior to surgery
ASA grade (goes from ASA1-ASA6)
Outline the ASA grades for pre-op assessment for anaesthetic
ASA grade 1:
- Normal healthy patients
- Non-smokers
- No/minimal alcohol intake
- Good BMI (normal or overweight)
ASA grade 2:
- Mild systemic disease e.g. well controlled diabetes or hypertension, mild lung disease
- Current smoker
- Social alcohol drinker
- Obesity (BMI 30-40)
ASA grade 3:
- Severe systemic disease e.g. poorly controlled diabetes or hypertension, COPD, history of ACS/stroke/TIA >3 months ago
- Morbid obesity (BMI >40)
ASA grade 4:
- Severe systemic disease that is a constant threat to life e.g. MI/stroke/TIA within 3 months, severe valve dysfunction, severe reduction in ejection fraction, sepsis
ASA grade 5:
- Patients not expected to survive the operation e.g. ruptured abdominal aortic aneurysm, massive bleed, intracranial haemorrhage with mass effect
ASA grade 6:
- Brain-dead organ donor
List some investigations that you may do prior to surgery
- ECG / echogardiogram
- Lung function tests
- Imaging e.g. CT / MRI / X-ray
- Bloods (U&Es, FBC, HbA1C)
- Clotting testing
- Group and Save
List some types of medications that may need to be stopped prior to surgery
List 2 medications that may be altered with upcoming surgery
- Hormonal contraception either COCP or HRT (4 weeks before)
- Clopidogrel (7 days before)
- Warfarin (5 days before)
- DOAC (2 days before)
- Hypoglycaemic diabetic medications
- Subcutaneous insulin – may be switched to IV variable rate insulin infusion
- Long-term steroids – must be continued, due to the risk of Addisonion crisis
State how T1DM is managed alongside surgery
Night before surgery:
- Reduce subcutaneous basal insulin dose by 1/3rd
Morning of surgery:
- Miss morning insulin
- Commence an IV variable rate insulin infusion pump (sliding scale with rapid insulin)
- Also dextrose infusion of 5% (whilst the patient is nil by mouth)
Around time of surgery:
- Check the CBG every 2 hours and to alter infusion rate accordingly
- Continue above routine until the patient is able to eat and drink
- At this point, overlap their IV insulin infusion stopping and their normal SC insulin regimens starting (give their SC rapid acting insulin before a meal and stop their IV infusion after they’ve eaten)
State how T2DM is managed alongside surgery
Depends on how their T2DM is controlled
Diet controlled
- NO action required
Oral hypoglycaemics:
- Metformin: stopped on the morning of surgery
- All other oral hypoglycaemics: stopped ~24 hours before operation
= Instead, patients put on IV variable rate insulin infusion along with dextrose 5% infusion (as with T1DM)
Check UHL guidelines - advice regarding specific medications
State some factors that make a patient high-risk for anaesthetics (may need a pre-op review)
- High BMI
- Respiratory issues
- Cardiac issues
- GORD or other reflux diseases
- Endocrine issues
- Previous reaction to anaesthetics
- Frailty
- Increased age (general)
- Sickle cell disease
- Pregnancy
- Significant social history e.g. alcoholic
State indications where the following blood products would be given:
- Packed red cells
- Platelets
- Fresh frozen plasma
- Cryoprecipitate
Packed red cells:
- Acute blood loss
- Chronic anaemia
- Symptomatic anaemia
Platelets:
- Haemorrhagic shock in a trauma patient
- Profound thrombocytopenia
- Bleeding with thrombocytopenia
- Low pre-operative platelet level
Fresh frozen plasma (clotting factors):
- DIC
- Any haemorrhage secondary to liver disease
- All massive haemorrhages
Cryoprecipitate (fibrinogen, vWF, factor 8 and fibronectin):
- DIC with low fibrinogen
- Von Willebrands disease
- Massive haemorrhage
List some contraindications for non-invasive ventilation
- Facial trauma (fractures or burns)
- Reduced conscious level
- Aspiration risk e.g. vomiting
- Inability to protect airway e.g. impaired swallow
- Haemodynamically unstable
- Patient preference (refusal of treatment)
Outline the layers through which the epidural injection and spinal block go through
Epidural:
- Injects into the epidural space
- Goes through: dermis, subcutaneous fat, supraspinous ligament, interspinous ligament, and ligamentum flavum (pop) to enter the epidural space (don’t go any further, next layer is the dura mater)
- Epidural space is between the ligamentum flavum and dura mater
Spinal block:
- Injects into the subarachnoid space
- Goes through: dermis, subcutaneous fat, supraspinous ligament, interspinous ligament, and ligamentum flavum (pop), dura mater and subarachnoid mater
- Subarachnoid space is between the subarachnoid mater and pia mater
Outline why there is a risk of aspiration at the induction of anaesthesia
- Patient falling into the subconscious
- Loss of lower oesophageal tone
- Loss of protective reflexes e.g. cough reflex / gag reflex
- Horizontal lie, lack of gravity, therefore increased risk of aspiration
