Anaesthetics and analgesia Flashcards
three major categories of anaesthetics
general anaesthetic
neuroaxial anaesthetic
peripheral nerve block
what is a general anaesthetic
involves administration of anaesthetic drugs that induces a total state of unconsciousness
A GA can be broken into three categories
induction
maintenance
emergence
sevofurane, desfurane
What is a neuroaxial anaesthetic
- includes both spinal and epidural anaesthetic
- involves administration of local anaesthetic into either the epidural space for epidural anaesthesia, or subarachnoid space for spinal anaesthesia
- usually the patient will have light sedation but will not require ventilation
- spinal or epidural anaesthetics are frequently combined with analgesics such as morphine or fentanyl
- advantage - reducing post op opioid use
Specific questioning required for anaesthetics
-Are you dizzy?
Spinal blocks can lead to a sympathetic block. This can then lead to bradycardia and hypotension.
-Are you SOB?
Spinal morphine can lead to delayed respiratory depression 18hrs post block, caused by rostral spread in the CSF (ie: towards the head) to the brain stem and respiratory centre.
-Have you got any pins and needles/numbness?
Motor block depending on dermatomal level of spinal anaesthetic may still be present the following day.
- Specific pain questioning
- Do you feel sick? Are you nauseous? Have you had an antiemetic?
spinal morphine consequence
Spinal morphine can cause urinary retention as well as puritis (itching), so be on the look out for signs and symptoms of these in your assessment, and refer to appropriate health professionals when necessary.
Respiratory Ax with orthopaedic pts follows tiered approach by looking for flags such as
- past medical history captured during the patient interview (eg: OSA, asthma, COPD)
- smoking history
- anaesthetic type: general anaesthetic due to intubation and regulated ventilation for prolonged period. Spinal anaesthetic due to potential respiratory depression
- observations, palpation, auscultation findings.
When mobilising a patient post anaesthetic
he may need a splint to mobilise if power in his legs is affected
he needs to be provided with good education in regards to what he may feel with decreased power in his legs
he needs to be questioned and assessed regularly for nausea. Be wary, as if a patient needs to be sick whilst mobilising, it becomes a significant falls risk.
Femoral Nerve Block
During the operation, surgeons and anaesthetists may employ strategies to reduce post-operative pain. These include regional nerve blocks and intra-articular infiltrates. When performed correctly, regional nerve blocks, such as femoral nerve blocks and sciatic nerve blocks, can be very effective in reducing patient’s post- operative pain.
For patients having total knee arthroplasties, the femoral nerve block alone will provide good analgesia to about half of patients, the rest will have light to fairly severe pain in the posterior leg in the sciatic distribution. Because of this the femoral nerve block is probably best performed with a proximal sciatic block for more complete coverage of operative procedures from about the mid-thigh to the bottom of the foot.
Regional nerve blocks can be single shot or continuous infusion via a catheter (similar to epidural catheter) - this catheter will be obvious on day 1 when you observe the patient.
If the patient had a single shot regional block – it will usually be documented on the anaesthetic record under “regional”.
Regardless of whether the patient has had a single shot or continuous infusion, similar questioning around sensory and motor changes is required in your post-operative assessment.
Fascia Iliaca Compartment Block (FICB)
is a block for post-operative pain relief for procedures and injuries involving the hip, anterior thigh, and knee - this block is useful, pre and post-operatively, for fractures of the hip and proximal femur, as well as total hip arthroplasties - the effect is the same as with a traditional 3 in 1 block.
Intra-articular infiltrations
Intra-articular infiltrations involve the surgeon inserting a large volume of local anaesthetic into the joint before closure of the wound. This is increasingly common in orthopaedic surgery. This may be a single shot injection or a catheter may be left insitu from the joint cavity to the skin, allowing a top up dose before it is withdrawn. Local anaesthetics have the advantage of blocking pain conduction at its origin and minimising the systemic side effects associated with post-operative opioid use. Ketoralac (injectable NSAID) and adrenaline may also be added to the local anaesthetic mix.
LIA with local adjuvants compared with epidural analgesia results in reduced opioid consumption, faster mobilisation, and earlier readiness for hospital discharge. Ketorolac and morphine are more efficient when given locally than systemically (Spreng et al 2010).
possible complications of opioid use
excessive sedation decreased respiratory drive/ low RR pruritus (itch) nausea and vomiting urinary retention confusion poor bowel motility/constipation pinpoint pupils poorly controlled pain.
possible complications of epidurals
epidural abcess epidural haematoma postdural puncture headache nerve or spinal cord injury total spinal blockade (when catheter migrates to subarachnoid or subdural space, resulting in large doses of anaesthetic and/or opioid into the cerebrospinal fluid).
When analysing PCA on the first day - always consider
spinal morphine given peri-operatively can have lasting effects (up to 24hrs), leading to low pain scores and minimal PCA demand/use
education is very important - as the spinal morphine wears off, pain levels usually increase rapidly
best advice with PCA is to press as soon as only ‘slight’ pain is present, when pain levels get to a high level, it is much harder to catch up
1mg bolus is only a small amount (particularly for a larger man)
if the patient is in considerable pain, more than one press of the button is often necessary to make a difference .
persistant pain
Persistent pain post-operatively in orthopaedics is a grave concern. In order to understand what “good analgesia” means, an understanding of the medications used and their qualities is paramount. Please refer to the table which is on the following page, it will be a good resource for you.
It is important to note that 80% of patients suffer moderate or intense pain after surgery even with routine and seemingly adequate use of analgesia (Ketovuori 1987
