Anaesthetics - Conduct of Anaesthesia Flashcards
What are the four ways in which anaesthetists prepare for surgery?
Pre-Operative Assessment
Monitoring Machine Preparation
Intravenous Access
Pre-Oxygenation
What is the purpose of the pre-operative assessment?
It is an opportunity to identify co-morbidities that may lead to complications during the anaesthetic, surgical or post-operative period
What are the five pieces of monitoring equipment that should be prepared by anaesthetists prior to surgery?
ECG
Oxygen saturations
Non-invasive blood pressure
End-tidal CO2
Airway pressure
Why do we observe ECG’s when anaesthesia is administered?
Arrhythmias are common
Why do we observe blood pressure when anaesthesia is administered?
Hypotension is common
Where is the cannula usually inserted to allow intravenous anaesthesia administration?
Back of the hand
Why is pre-oxygenation required prior to anaesthesia?
Due to the fact that anaesthesia reduces functional residual capacity, oxygen is administered for a few minutes to oxygen content from 21% to nearer 100%
This increases the time to desaturation, providing the anaesthetist more time to supply the patient with oxygen before apnoea occurs
What are the four phases of anaesthesia?
Induction
Maintenance
Emergences
Recovery
What is the induction?
It is the period between the administration of induction agents and loss of consciousness
What are the two administration methods of induction agents?
Intravenous
Inhalation
What combination of induction agents are usually administered?
A short acting analgesic with a hypnotic
In some cases, a muscle relaxant may also be prescribed
List two short-analgesic agents
Fentanyl
Alfentanil
List three hypnotic agents
Propofol
Thiopentone
Ketamine
What is the most commonly administered hypnotic agent?
Propofol
In which patients do we administer inhalation induction agents? Why?
Children
They won’t tolerate the placement of a canula
What results in a quicker state of unconsciousness - intravenous or inhalation induction?
Intravenous
What is induction stage one?
It defines the period between the administration of induction agents and loss of consciousness
During this stage, the patient progresses from analgesia without amnesia to analgesia with amnesia
What sensation do patients report during induction stage one?
A relaxed and floaty sensation
What is another term for induction stage two?
Excitement stage
What is induction stage two?
It defines the period following loss of consciousness and marked by excited and delirious activity
What are the signs of induction stage two?
During this stage, the patient’s respiration and heart rate may become irregular
In addition, there may be uncontrolled movements, vomiting, suspension of breathing and pupillary dilation
What is another term for induction stage three?
Surgical anaesthesia
What is induction stage three?
It defines the period in which the skeletal muscles relax, vomiting stops, respiratory depression occurs and eye movements slow and then stop
The patient is unconscious and ready for surgery
What is another term for induction stage four?
Overdose
When does induction stage four occur?
This occurs when too much anaesthetic medication is given relative to the amount of surgical stimulation
What are the consequences of induction stage four?
Brainstem or medullary depression
This stage is lethal without sufficient support
Why are the stages of induction rarely visualised in adult patients?
This is due to the rapid state of unconsciousness produced by intravenous induction agents
What three main things do we monitor once induction has been achieved?
Airway
Breathing
Circulation
Why is it essential that we monitor the patient’s airways after induction?
This is due to the obstructive effects caused by relaxation of upper airway tissues and loss of airway reflexes
How do we generally open a patient’s airways?
We perform a triple airway manoeuvre
This is accompanied with an anaesthetic mask
What are the three components of the triple airway manoeuvre?
Head tilt
Jaw thrust
Open the patient’s mouth
What are three forms of additional airway management?
Oropharyngeal Airway
Laryngeal Mask Airway (LMA)
Endotracheal Tube (ETT)
What is another name for the oropharyngeal airway?
Guedel airway
How does the oropharyngeal airway device maintain airway patency?
It stops the tongue from covering the epiglottis
What are the two complications when an oropharyngeal airway is inserted into patients who are not anaesthetised?
Vomiting
Laryngospasm
How does the laryngeal mask maintain airway patency?
It provides a tight seal over the larynx and thus directs gas flow towards the patient’s airway
What is a ETT?
It is a flexible tube that is placed through the mouth, past the vocal cords, and into the trachea
This tube is then connected to a ventilator, which delivers oxygen to the lungs
This process is called endotracheal intubation
What device is used to insert an ETT?
Laryngoscope
What is intubation?
It is the process of inserting a tube into the airway via the mouth/nose to help move air in and out of the lungs
In which five circumstances is intubation required?
Unfasted Aspiration Protection
Muscle Relaxant Administration
Shared Airway Case
Strict CO2 Control
Minimal Patient Access
What is a shared airway case?
This is when the surgeon and anaethestitst are working on the mouth/face
How do we confirm a successful intubation?
It is indicated by an end tidal CO2 trace for more than 5 breaths
During anaesthesia, what are the three breathing mechanisms?
Spontaneous
Controlled
Supported
What is spontaneous ventilation?
It involves the movement of gas in and out of the lungs in response to an individual’s respiratory muscles
This means that breathing occurs without ventilatory support
What is controlled ventilation?
It involves the anaesthetist delivering a pre-set gas volume or pressure, regardless of the patient’s own inspiratory efforts
This means that breathing occurs with complete ventilatory support
What is supported ventilation?
It involves partial support of spontaneous ventilation by a ventilator
This decreases the imposed work of breathing for the patient
In what two ways do we monitor breathing after administration of anaesthesia?
Oxygen saturations
End-tidal CO2 volume
Why is it essential that circulation is monitored after induction?
This is due to the haemodynamic effects associated with anaesthesia
In what two ways do we monitor circulation after induction?
ECG heart rhythm
Blood pressure
How often do we measure blood pressure after induction?
Every five minutes
What are six complications associated with anaesthesia?
Awareness
Eye Injury
Hypothermia
Pressure Injury
Venous Thromboembolism
Nerve Injury
What is awareness?
This occurs when patients can recall their surroundings or events related to their surgery
In what two ways do we prevent awareness during surgery?
The anaesthetist monitors for signs of light anaesthesia
We can use anaesthesia depth monitors to calculate the levels of anaesthesia during surgery
What are the three signs of light anaesthesia?
Tachycardia
Hypertension
Sweatiness
List two anaesthesia depth monitors
BIS monitors
EEG scans
Why are eye injuries associated with anaesthesia?
Due to dysfunction of the blinking reflex
This can allow foreign objects to penetrate the eyes and drying of the cornea
In what two ways do we prevent eye injuries during surgery?
We tape the patient’s eyes shut
We apply a lubricating ointment to the eye
Why is hypothermia associated with anaesthesia?
Due to the vasodilatory effects of anaesthetic
What are the three complications of hypothermia during surgery?
Surgical site infection
Post-operative pain
Haemorrhage
In what two ways do we prevent hypothermia during surgery?
We cover the patient with warm air blankets
We monitor the patient’s temperature every 30 minutes. In some cases, temperature is constantly monitored through the use of an oesophageal temperature probe
Why are pressure injuries common during anaesthesia?
Due to the loss of pain reflex from anaesthesia
In what two ways do we prevent pressure injuries during surgery?
We carefully pad the patient’s pressure areas
We increase our awareness of the tubes surrounding the patient
In what three ways do we prevent venous thromboembolism during surgery?
We encourage patient movement prior to surgery
We apply TED stockings
We apply flowtron pumps
How do we prevent venous thromboembolism in high risk patients?
We administer dalteparin the night before surgery
Why are nerve injuries common during surgery?
Due to the loss of pain reflex from anaesthesia
What three nerves are commonly injured during surgery?
Ulnar nerve
Common fibular nerve
Brachial plexus
How do we prevent nerve injuries during surgery?
We appropriately position the patient
What is the maintenance phase of anaesthesia?
In order to prolong unconsciousness for the duration of the surgery, anaesthesia must be maintained
How do we maintain anaesthesia?
Continuous adjustments to the administration of inhaled/intravenous anaesthetic agents
What is the most common intravenous maintenance agent?
Propofol
What equipment can be used to help maintain intravenous anaesthesia?
A target controlled infusion (TCI) machine
How do we awaken the patient after surgery?
The administration of anaesthetic agents is discontinued
When is a conscious state achieved after discontinuation of anaesthesia?
When the concentration of anaesthetic in the brain drops below a certain level
This usually takes between 1 to 30 minutes
What two drugs are given before we discontinue anaesthesia?
Analgesic
Anti-emetic agents
What must occur before we discontinue anaesthesia - if a muscle relaxant was administered?
The neuromuscular blockade must be reversed
What is the emergence phase of anaesthesia?
It is the return to baseline physiologic function of all organ systems after the cessation of general anaesthetics
What may occur to the patient during the emergence stage?
This stage may be accompanied by temporary neurologic phenoma, such as confusion, aphasia or focal impairment in sensory or motor function
