Anaesthetics Flashcards
What are the advantages of regional anaesthesia ?
Avoidance of adverse effects of general anaesthesia ( nausea, resp depression and risk of aspiration )
Improved postoperative pain relief
Decreased or no opioid relief
Faster recovery
Reduced stress repsonse
Reduced blood loss
What are the types of regional anaesthesia ?
Central neuraxial blocks
Peripheral nerve blocks
IV regional anaesthesia
Topical and infiltration anaesthesia
How is spinal anaesthesia given ?
A thin 9cm needle is placed through the skin, soft tissue, spinal ligaments and dura until it reaches the subarachnoid space and a small amount of local anaesthetic is given - performed in the lumbar region.
How long does spinal anaesthesia last ?
2-3 hours
Intrathecal injection of local anaesthesia produces an extensive sympathetic block. What does this cause ?
A drop in systemic vascular resistance and BP
HR may increase, decrease or may remain the same depending on the level of the block.
What is the difference when performing epidural rather than a spinal anaesthesia ?
A longer and larger needle is used to reach the epidural space and a catheter is placed through the needle into the epidural space.
A larger volume is required and takes longer to establish an effect.
What are the most common vasopressors used to manage hypotension associated with neuraxial anaesthesia ?
Metraminol
Ephedrine
Phenylephrine
What are some complications of central neuraxial blocks ?
Failure of technique
Direct trauma to nerves and adjacent structures
Haemodynamic instability
Meningitis
Epidural haematoma / abscess
Back pain
Urinary retention
What are some complications of a peripheral nerve block ?
Failure of technique
Direct trauma to adjacent structures
Allergic reaction
Infection
Pneumothorax, recurrent laryngeal nerve palsy - supraclavicular block
What is the pharmacology of local anaesthetic drugs ?
It reversibly blocks sodium channels on the neuronal membrane and block the conduction of impulses. Thus it produces reversible loss of motor power and sensory sensation.
What are some local anaesthetic drugs ?
Lidocaine
Bupivacaine
Ropivacaine
Levobupivacaine
What are some absolute contra-indications of regional anaesthesia ?
Patient refusal
Localised infection
Allergy to medications used
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.
What are some risk factors for a laryngospasm ?
Insufficient depth of anaesthesia
Mucous or blood in the peri-glottis area
Airway manipulation
Age
Airway hyperactivity
Recent URTI
GORD
Upper airway surgery
Thyroid surgery
What are some clinical features of laryngospasm ?
Stridor
Abnormal see-saw movements of the abdomen and chest wall in a spontaneously breathing patient
What is the management of laryngospasm ?
Removal of stimulus
Call for senior anaesthetic help
100 FiO2 high flow oxygen using a face mask
Application of positive end expiratory pressure
Deepening of anaesthesia with propofol
What are the complications of laryngospasm ?
Desaturation and hypoxia
Negative pressure pulmonary oedema
Bradycardia
What is malignant hyperthermia ?
An autosomal dominant disorder affecting the skeletal muscles. A genetic mutation affecting the ryanodine receptor of the sarcoplasmic reticulum in skeletal muscles. This causes raised intracellular calcium ions leading to prolonged muscle contraction. Volatile anaesthetic agents and suxamethonium can trigger malignant hyperthermia.
what are some clinical features of malignant hyperthermia ?
Masseter spasm
Generalised prolonged muscle rigidity
Increased end tidal CO2
Rapid increase in core body temperature
Rhabdomyolysis
Hyperkalaemia
What is the management of malignant hyperthermia ?
Call for senior anaesthetic help
Disconnecting the patient from the anaesthetic machine to stop the delivery of the volatile agent
Supply 100% FiO2 from an alternative oxygen source with hyperventilation to reduce CO2
Maintain anaesthesia
Dantrolene - antagonist
Active cooling of body
Monitor urine ouput
What are some complications of malignant hyperthermia ?
Hyperkalaemia
Acute renal failure
Life threatening arrhythmias
What is anaphylaxis ?
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.
What are some common triggers in the field of anaesthesia ?
Antibiotics
Muscle relaxants
Latex
What are some clinical features of anaphylaxis ?
Mucocutaneous manifestations - urticaria, generalised rash, lip and tongue swelling, flushing
Hypotension
Tachycardia
Bronchospasm
Wheezing
What is the management of anaphylaxis ?
Stop the administration of the suspected causative drug
Call for help
Apply 100% FiO2 oxygen - consider intubation if necessary
Administer 0.5ml of adrenaline IV - repeat dose every 3-5 minutes
IV fluid resus with crystalloids to maintain arterial BP
What is the aim of pre-oxygenation ?
Denitrogenation - replace the nitrogen in the resp system
Why isnt a Guedel airway ( oropharyngeal ) used in conscious patients ?
Gag reflex
What is a nasopharyngeal airway contraindicated in ?
A base of skull fracture
What is a laryngeal mask airway ?
An inflatable elliptical mask that sits around the laryngeal inlet
What is post operative nausea and vomiting ?
Any nausea or vomiting during the first 24-48 hours after surgery in patients
What are some risk factors for post operative nausea and vomiting ?
History of motion sickness
Previous episodes
Female
Non smoker
Opioid administration
What are the advantages of crystalloids ?
Cheap
Non allergic
No transmission of infection
No interference with coagulation
What are the disadvantages of colloids ?
Expensive
Risk of allergy
Coagulopathy
Itch
May exacerbate tissue oedema
what are the disadvantages of crystalloids ?
Higher volume needed
Relatively short amount of time remaining IV
What are some advantages of colloids ?
Expansion of plasma volume far superior
May be salt sparring
What do hypotonic solutions cause ?
Water is transported into the cells causing them to burst
What do hypertonic solutions cause ?
Water is transported out of cells and they shrink
What is is important to ask for in the past medical history for pre-operative history ?
Cardiovascular disease ( including HTN ) - screening questions ( exertional chest pain, syncopal episodes or orthopnoea )
Respiratory disease - chronic cough, any signs and symptoms of obstructive sleep apnoea
Renal disease
Endocrine - DM or thyroid disease
GORD - aspiration of gastric contents can be fatal
Pregnancy
What questions should be asked about in the past surgical and anaesthetic history ?
Any previous operations ? If so when and what ?
Has the patient had anaesthesia before ? If so what operation and what type of anaesthesia? Were there any problems ? Any post operative nausea and vomiting ?
What is important to ask about in the family history ?
Hereditary conditions such as malignant hyperthermia
What should be asked about in the social history ?
Smoking
Alcohol intake
Recreational drug use
Language spoken
Living situation
What are some pre-operative blood tests and why perform them ?
FBC to assess for anaemia or thrombocytopenia
U&E’s to help inform fluid management and drug decisions
LFT’s
HbA1c
Thyroid tests
Clotting screen - any blood disorders
Group and save
What is the difference between group and save versus cross-match ?
G&S determines patients blood group and screens for any atypical antibodies ( takes about 40 minutes ) and is used when blood loss is not anticipated
Cross-match involves mixing the patient’s blood with he donors to see if there is an immune reaction ( takes 40 minutes in addition to G&S )
What are some pre-operative cardiac investigations and why perform them ?
ECG - can be used to compare pre to post op
ECHO - helps tailor intra-operative care
What are some pre-operative respiratory tests and why perform them ?
Spirometry if COPD
Plain film radiograph - only used if necessary
What are some pre-operative OTHER tests and why perform them ?
Urinalysis - if there is suspicion of UTI
MRSA swab - from nostril and perineum
Cardiopulmonary exercise testing - assesses VO2 max and anaerobic threshold
What drugs should be stopped prior to surgery ?
Clopidogrel
Hypoglycaemic
Oral contraceptive pills
Warfarin and DOACs
What drugs should be altered prior to surgery ?
Subcutaneous insulin
Long term steroids - must be continued due to risk of addisonian crisis may need to be switched to IV
What advice should be given pre-op to a patient ?
Fasting - no food up to 6 hours before surgery, clear fluids only up to 2 hours before
What drugs should be started pre-op ?
Low molecular weight heparin
Anti-embolic stockings
Antibiotic prophylaxis
Why in septic patients is it often necessary to give large volumes of IV fluids ?
The tight junctions between the capillary endothelial cells break down and vascular permeability increases. As a result increasing hydrostatic pressures and reducing oncotic pressure lead to fluid leaving the vasculature and entering the tissue.
If a patient is fluid depleted what signs would be present ?
Dry mucous membranes and reduced skin turgor
Decreasing urine output
Orthostatic hypotension
Increased CRT
Tachycardia
Low BP
If a patient is fluid overloaded what signs would be present ?
Raised JVP
Peripheral and sacral oedema
Pulmonary oedema
How can pain be assessed ?
Subjective - rate 1 to 10
Objective - clinical signs of pain ( tachycardia, tachypnoea, HTN, sweating or flushing
What are the consequences of poor pain control ?
Inadequate control of post-operative pain results in slower recovery - reluctance to mobilise
What is the WHO analgesic ladder ?
It provides a strategy for titrating analgesia starting with simple analgesics and working upwards towards stronger opioids.
What are some simple analgesics ?
Paracetamol
NSAIDs - ibuprofen and Diclofenac
What are some side effects of NSAIDs ?
Interaction with other medications
Gastric ulceration
Renal impairment
Asthma sensitivity
Bleeding risk
What is a weak opioid ?
Codeine
what are some strong opioids ?
Morphine
Oxycodone
Fentanyl
What are some side effects of opioids ?
Constipation and nausea
Sedation or confusion
Respiratory depression
Pruritis
Tolerance and dependence
What can be used as an adjunct following surgery for pain management ?
Local anaesthesia
What is patient controlled analgesia ?
The use of an IV pump that provides a bolus dose of an analgesic when the patient presses a button.
What are some advantages of patient controlled analgesia ?
Provides analgesia that is tailored to the patients requirements
Safe as the risk of overdose is negligible
Can accurately record how much opioid is used
What are some disadvantages of patient controlled analgesia ?
Can be cumbersome and prevent the patient mobilising
Not appropriate for those with poor manual dexterity or severe learning difficulties
What is neuropathic pain ?
It results from irritation or injury directly to the nerves either peripherally or centrally.
Often presents with shooting or stabbing pains
What is the management of neuropathic pain ?
Non-pharmacological - CBT, capsaicin cream
Pharmacological - Gabapentin, amitriptyline or pregabalin
If a DVT is suspected what should be performed ?
DVT wells score :
-score less than 1 DVT is unlikely and requires D-dimer test to exclude
-score greater than 1 DVT should be diagnosed with a USS
What is the management of a DVT ?
DOAC are first line and should be continued for 3 months
How is blood grouped ?
ABO blood system
Rhesus D groups
When is there a problem in transplanting blood in relation to the rhesus D group ?
In pregnancy as anti-D antibodies can cross the placenta.
Example :
A woman is brown with rhesus D negative blood. Her partner is rhesus D positive and become pregnant with a baby who is rhesus D positive. During childbirth she comes into contact with foetal rhesus positive blood and develops antibodies. If she becomes pregnant again with a child with rhesus D positive the antibodies can cross the placenta and bind to the foetus RhD antigens on the RBC surface. This causes haemolytic disease of the newborn.
What blood type is a universal donor ?
O negative
What blood type is a universal acceptor ?
AB positive
What are the 2 blood tests that are performed prior to blood transfusion ?
Group and save
Cross-match
Which groups of people should receive irradiated blood products ?
Those receiving blood from first or second degree family members
Patients with Hodgkin’s lymphoma
Recent haematpoietic stem cell transplants
After ATG or alemtuzumab therapy
Receiving chemotherapy
Intra-uterine transfusions
What are some types of blood products ?
Packed red cells
Platelets
French frozen plasma
Cryoprecipitate