General Anaesthesia Flashcards
Define Surgery
The treatment or investigation of injuries or disorders of the body by incision or manipulation, often involving the use of instruments, with the aim of improving function or appearance
Performed under either General/local anaesthesia
Theatre or bedside
Types of surgery
Open surgery is full incisions (suffix atomy)
Minimal invasive surgery or key hole surgery (suffix oscopy)
Define local anaesthetic
Used to treat or prevent pain during or after a procedure or surgery
How does local anaesthetics work
Simple & quick application with fast recovery
They work by entering the cell, binding to the Na+ channel, preventing Na+ transport and thus stopping the conductance through the nerve & preventing the transmission of the pain signal to the brain
Pressure & movement still felt
How can LA be given
Injections, creams, gels, sprays or ointments
Epidural & spinal - into epidural or subarachnoid space
Peripheral nerve block - will use US to locate correct nerve
Common LA
amino amides such as lidocaine & bupivacaine
What is GA
Purpose is to create a loss of awareness & a temporary block in gross responses to stimuli
How does GA work
Skeletal muscle contraction (so patient is less likely to move) Autonomic responses (lowers HR, BB, sweating)
State components of GA
Coma
Muscular relaxation
Analgesia
State stages of GA
Premedication
Induction
Maintenance
Reversal
Explain premedication stage of GA
Provides ↓ anxiety
Helps with pain relief, sedation and encourages amnesia
Less common - increase day case surgery and overall pressure on NHS
Explain induction stage of GA
Rapid process whereby a short-acting coma-inducing drug is given, i.e. IV propofol
+/- Sevoflurane (inhaled anaesthetic gas)
+/- intubation - may be given a paralysing drug, i.e. Atracurium to relax skeletal muscles and facilitate endotracheal intubation and mechanical ventilation.
Anaphylaxis (severe allergic reaction) can happen although rare - patients closely monitored
Explain maintenance stage of GA
When surgery starts
State of coma in maintained through continuation of anaesthetic, IV analgesics & muscle relaxants + narcotic drugs (pain relief)
Explain reversal stage of GA
Begins before the surgery has finished with the reduction in the anaesthetic drugs
Drug given (Neostigmine) to reverse effects of paralysis so patient can start trying to self-ventilate
Occasionally after this if patient are not spontaneously breathing after Neostigmine then another drug to reverse effect of narcotics is given, i.e. Narcan. However analgesic effect will subside so patients will need another form of pain relief
State effects of GA on the respiratory system
- G.A. has a detrimental effect on respiratory function
- Under GA FRC may be lowered which encroaches on CV, reduces lung compliance, increases airway resistance and leads to atelectasis
- Atelectasis occurs rapidly and dependent lung collapse occurs within 15 minutes of induction
- Risk of absorption atelectasis - associated with high levels of O2
- Inhalation of dry, cold gas increases mucus viscosity and affects surfactant production
- MCC stops after 90 minutes of GA
- Impairs CNS regulation of breathing leading to hypoventilation + supine position exacerbates atelectasis
- Handling of viscera (during surgery) –ve neural effect on diaphragmatic function
All complications tend to produce a restrictive pattern of deficit in surgical patients
General effects of surgery on C/R systemq
Often compound on to -ve effects of GA
- Atelectasis:
a. Pain - causes patients to guard and take smaller breaths
b. Prolonged recumbent position - complex long duration surgery, reduces FRC
c. Drowsiness for several hours post-op, causing immobility further reducing FRC and TV
d. Disruption of diaphragm - specifically upper abdominal surgery, further compounded with abdominal distension following surgery
e. Pleural effusion - fairly minor but commonly seen; can be due to the fluid given during surgery and will further exacerbate atelectasis
f. Atelectasis → Atelectasis of other areas more likely due to restrictive pattern and thus leads to higher WOB - Hypoxaemia:
a. ↓ Hypoxic vasoconstriction because of anaesthetic gases - normal response to shunt is to constrict perfusion in areas of wasted perfusion
b. Atelectasis
c. Oxygen-hungry - Post-op patients high risk of hypoxaemia, especially at night as normal sleep pattern (REM cycle) is obliterated due to GA. O2 sats should be monitored for first 2-4 nights post-surgery - Chest Infection >48 hours post-op elevated temp = infection
a. High risk due to effects of GA but also effects of surgery
Post-op complications of surgery and GA
- Chest – Atelectasis & infection
- Wound infection
- Pulmonary Oedema
- Cardiovascular problems & MI
- Shock incl. anaphylaxis
- DVT/PE - dehydration and immobility
- Acute renal failure
- Reduced gut motility
- Nausea and vomiting - (drugs can control)
- Psychosis & delirium
- Nerve damage - incisions
- Pressure sores
- Tooth loss or chipping
- Myalgia (muscle aches)
- Pain - inadequate pain relief has a direct effect on other post-op complications, i.e hypoventilation atelectasis, increases O2 consumption and risk of infection
- Haemorrhage - at risk perioperatively and post-op
- HTN - anxiety or not taking BP med due to NBM
State factors of respiratory muscle dysfunction post-op
- Surgical trauma stimulates central nervous system (CNS) reflexes mediated by both visceral and somatic nerves that produce reflex inhibition of the phrenic and other nerves innervating respiratory muscle
- Mechanical disruption of respiratory muscles impairs efficiency
- Pain produces voluntary limitation of respiratory motion. These factors all tend to reduce lung volumes and can produce hypoventilation and atelectasis.
Aims of PT in surgical patients
Increase lung volumes
Clear secretions
To rehabilitate and promote independence
Physio management to increase lung volume and clear secretions
Mobilise/exercise - most effective and efficient but also prevents DVTs and PE's; motivational to patient especially if functional Positioning Breathing exercises (ACBT, TEE’s) Adjuncts (PEP, Incentive Spirometry, IPPB, Clearways, MHI)
PT management to rehabilitate and improve independence
Mobilise/exercise
ADL
Home visits
Post-op cardiac rehab classes
Give brief overview of pre-rehabilitation (prehab)
A proactive approach designed to enhance functional capacity of an individual to enable them to with stand the stresses of surgery
It is associated with lower post-operative complications and earlier restoration of functional state
Multidisciplinary approach whereby patients considered holistically including nutrition, psychological and behavioural interventions as well as exercise
Opportunity for long term lifestyle changes
Timing is vital - need to have sufficient time pre-surgery to make physiological changes but also to be able to adopt a different lifestyle prior to surgery
May just be pre-warning patient what to expect post-surgery - you will be seeing them after surgery, asking them to get out of bed, that there are breathing techniques they could start before you arrive
