General Anaesthesia Flashcards
What is anaesthesia?
The absence of sensation
What is analgesia?
The absence of pain
What is the intention of regional anaesthetics?
Ensure the patient remains conscious and ventilating with haemodynamic stability yet cannot feel pain in a certain part of the body
What is an antipyretic?
Anti-temperature agent
Give an example of an antipyretic agent
Intravenous paracetamol
What is amnesia?
Inability to recall information
What is anxiolysis?
Elimination of anxiety
What is an antiemetic?
An agent used to reduce nausea and vomiting
What are 2 clinical scoring systems used to grade level of consciousness?
- AVPU
2. Glasgow Coma Score (GCS)
What are the 4 components of the AVPU consciousness grading system?
- Alert
- Verbal
- Pain
- Unresponsive
What are the 3 components of the GCS consciousness grading system?
- Best verbal response
- Best motor response
- Best eye contact
What is “A Conscious Decision”?
A review of the use of general anaesthesia and conscious sedation in primary dental care
What were the 2 main points taken from “A Conscious Decision”?
- Confinement of general anaesthesia for dentistry within a hospital setting where there was immediate availability of a critical care facility
- General anaesthesia should be undertaken only when absolutely necessary
Name 3 alternatives to general anaesthesia
- Behaviour management with or without conscious sedation
- Inhalation sedation
- Intravenous sedation
What is conscious sedation?
A technique where drugs produce state of depression of CNS, but during which verbal contact with the patient is maintained
What is the major aim of conscious sedation?
Reduce anxiety of patient and enable procedures to be longer without the need for general anaesthetics
Name 3 safety measures which must be taken if a dental professional is providing conscious sedation
- Operating chairs must be capable of being placed in head down tilt position
- Equipment for resuscitation from respiratory and cardiac arrest must be available
- Patients must be escorted home
Name 4 types of anaesthesia
- General anaesthetics
- Sedation
- Regional anaesthesia
- Local anaesthetics
What is the major complication with sedation?
Patient can lose consciousness and become apnoeic or go into a state of cardiac arrest
What is regional anaesthesia?
Use of local anaesthetics to block specific regions of the peripheral nervous system
What is local anaesthesia?
Infiltration of local anaesthetics into the subcutaneous tissues to block innervation of the skin
How is epidural anaesthesia delivered?
Via a catheter to allow anaesthetic to be topped up
What are 2 ways a nerve can be identified before being anaesthetised?
- Landmark techniques
2. Ultrasound guidance
What are 3 major components of pre-assessment for anaesthesia?
- History
- Examination
- Investigations
Name 4 parts of a patient’s history to be checked during pre-assessment for anaesthesia?
- Co-morbidities
- Previous anaesthesia
- Allergies
- Chronic pain medication
What are co-morbidities?
Diseases co-occurring with primary problem
Why is it important to establish if a patient has previously been anaesthetised?
Their previous reaction can indicate suitability for anaesthesia
Name 4 examinations which should be undertaken during the pre-assessment for anaesthesia?
- BMI
- Syndromic features
- Urea biomarkers
- Creatinine biomarkers
Why is BMI important to examine before anaesthesia?
It can have dramatic effect of respiratory system, where a patient can quickly become apnoeic, develop an airway obstruction or go into respiratory arrest
Name a possible syndromic feature which could prevent anaesthesia
Treacher Collins syndrome
How can urea and creatinine biomarkers be tested?
Renal function tetss
Why must kidney function be tested before anaesthesia?
Under preforming kidneys may be unable to deal with massive clearance of the anaesthetic
Name 2 investigations which should be taken before anaesthesia
- ECG
2. Blood glasses rumere
Why is it important to take an ECG before a patient undergoes general anaesthesia?
It tests a patient’s anaerobic threshold and can help predict who may need critical care post operation
Describe the 7 degrees of anaesthesia
- Loss of sensation
- Loss of consciousness
3, Loss of spinal reflex function - Loss of ANS function
- Loss of central homeostatic control
- Brain stem dysfunction
- Death
What are the 4 stages of anaesthesia (Guedel)?
- Analgesia and disorientation
- Excitement and delirium
- Start of surgical anaesthesia
- From stoppage of respiration until death
Between what 2 events does stage 1 of anaesthesia occur?
Beginning of induction to loss of consciousness
Between what 2 events does stage 2 of anaesthesia occur?
Loss of consciousness to onset of automatic breathing
Between what 2 events does stage 3 of anaesthesia occur?
Onset of automatic breathing to respiratory paralysis
Between what 2 events does stage 4 of anaesthesia occur?
Respiratory paralysis to death
What are the 2 methods of inducing anaesthesia?
- Used at low dose continuously via syringe driver
2. Anaesthetic machine can deliver specific concentration agent
When is pre-medication usually used during the induction of anaesthesia?
Paediatrics
Name 3 drugs which can be used as pre-medication during the induction of anaesthesia
- Oral form of midazolam
- Nasal spray of fentanyl
- Oral clonidine
What are 3 advantages of pre-medication?
- Improved induction of anaesthesia
- Reduced parasympathetic system activity
- Lower maintenance dose of anaesthesia
Name 3 types of inhaled anaesthetic agents
- Halogenated hydrocarbons
- Nitrous oxide
- Xenon
What are 3 types of halogenated hydrocarbons?
- Sevoflurane
- Isoflurane
- Desflurane
How is nitrous oxide commonly used?
In combination with intravenous midazolam
What 4 factors can affect the onset of action of inhaled anaesthetic agents?
- Solubility of agent in the blood (poor solubility - faster onset)
- Inhaled concentration of agent (high concentration - faster onset)
- Lipid solubility of agent
- Cardiac output of patient (low output - faster onset)
Name 5 side effects of inhaled anaesthetic agents
- Slow onset of action when used as induction agent
- Effects on respiratory system
- Halogenated agents reduce mean arterial pressure and cardiac output
- Reduce hepatic blood flow
- Can induce nausea and vomiting
What is malignant hyperpyrexia?
A condition triggered by drugs used for general anaesthesia which causes drastic increase in oxidative metabolism in skeletal muscle which leads to circulatory collapse and death if untreated
Name 2 advantages of intravenous anaesthetics
- Rapid onset and offset of agent
2. More predictable response if titrated
Name 5 intravenous anaesthetics
- Thiopentone
- Propofol
- Midazolam
- Etomidate
- Ketamine
Describe midazolam as an intravenous anaesthetic agent
- Used for minor procedures
- It is a benzodiazepine so modulates effects of GABA at GABA-A receptors
- Flumazenil is a competitive antagonist so can reverse its effects
Describe fentanyl as an intravenous anaesthetic agent
- Synthetic phenylpiperidine derivative
- μ receptor agonist
Describe propofol as an intravenous anaesthetic agent
- Phenolic derivative which is highly lipid soluble
- Dose dependent reduction in cardiac output and systemic vascular resistance which can cause profound drop in blood pressure
- Involuntary muscle action common
- Pain at site of injection
Describe ketamine as an intravenous anaesthetic agent
- Antagonises the excitatory neurotransmitter glutamate at the NMDA receptors within CNS
- Increases blood pressure so stable induction of anaesthesia during emergencies
- Cause post operative psychotic symptoms
What are 2 main types of neuromuscular blocking agents?
- Non-depolarising neuromuscular blockers
2. Depolarising neuromuscular blockers
Name 2 examples of non-depolarising neuromuscular blockers
- Aminosteroids and bisbenzylisoquinoliniums
2. Rocuronium and Atracurium
Name an example of a depolarising neuromuscular blocker
Suxamethonium
What is the function of neuromuscular blocking agents?
Used to allow the incubation of the trachea
