Phys pharm anatomy Flashcards
Pretreatment with which medications may attenuate LA-induced cardiotoxicity?
clonidine & dexmedetomidine
How long may the inflammation-induced expression of opioid receptors at peripheral injury sites & delivery of endogenous opioids to balance the nociceptive state of inflammation take to have effect?
Up to 96hours
What’s the receptor affinity of buprenorphine to mu receptors cf fentanyl or morphine?
24-fold & 50-fold (but it’s a partial agonist)
What’s a controversy with perineurial opioids?
Unclear if any benefits are due to local peripheral nerve effects or due to systemic effects
In which formulations of LA is the effect of adding sodium bicarbonate most apparent?
those with added epinephrine, given they are generally formulated with lower pH
What concentration of hyaluronidase is used for retrobulbar/peribulbar block?
150units/mLFE
How does hyalase come & how is it prepared for retrobulbar/peribulbar block?
Purified, sterile freeze-dried powder of the enzyme hyaluronidase
Mix the contents (1500IU/vial) into 1mL of sterile distilled water
this makes a 150IU/0.1mL solution
Add 0.1mL to 6mL of LA solution, making 25IU/mL concentration
Is there any evidence for benefit of regional NSAIDs?
Yes- level II evidence (150pts) showing parecoxib/ropivacaine improved quality & duration of brachial plexus block vs placebo/ropiv or IV parecoxib/ropiv
To which of the opioid adverse effects does tolerance typically not occur?
miosis, constipation
For which of the opioids has a local anaesthetic action been described?
pethidine
How is the analgesia of intrathecal opioids mediated?
opioid receptors in the substantia gelatinous of the dorsal horn; 70% of mu & delta receptors are presynaptic, kappa more commonly post-synaptic
spinal opioid receptors are 70% mu, 24% delta & 6% kappa
anti-nociception may be further augmented by descending inhibition from mu-opioid receptor activation in the periaqueductal grey matter of the brain
What are possible ceiling effect doses for the analgesia provided by neuraxial opioids?
morphine 50-150mg IT & 2.5-3.75mg epidural
Mechanism & evidence for usefulness of intrathecal morphine
relatively hydrophilic so slower onset but longer half-life (hence prolonged duration of action) in the CSF. Greater cephalad migration cf lipophilic opioids
Low-dose ITM prolongs LA block, reduces LA dose, reduces adverse effects & improves recovery for spinal anaesthesia
100microg ITM produces analgesia comparable to 400microg when combined with low-dose bupivacaine for LSCS
single 100microg dose of ITM prolongs time to first analgesic admin by 16-20hours (level 1 evidence 535 pts)
Pruritis more common with higher doses
ITM reduces IV PCA consumption following abdominal hysterectomy
Evidence regarding epidural opioids
When used mainly in combination with LA, level 1 evidence has not shown difference in VAS pain scores postop between epidural opioids but morphine vs fentanyl produced higher rates of nausea & vomiting
Does epidural fentanyl act via a spinal or systemic effect?
evidence conflicting (fentanyl lipid soluble, sequestered in the epidural fat & slowly released back into epidural space, smaller fraction reaches the CSF)
Level II evidence suggests less intraop fentanyl is required if it’s given via Tx epidural vs IV & also longer time to first postop analgesia request
Is there benefit to epidural vs systemic sufentanil or alfentanil?
No
How does the analgesic benefit of epidural hydromorphone compare to epidural morphine?
similar
Comparing IV to epidural hydromorphone, pts required twice as much IV to achieve same degree of analgesia cf epidural.
When may the IJV be pulsatile?
Severe TR
What dose of sugammadex for TOFC & PTC 0? and if TOFC 0 but PTC >=1? and if TOFC 1-4 but TOFR <0.9?
16mg/kg
4-8mg/kg
2mg/kg
what dose of neo if TOFC 1-3 but TOFR 0? How about TOFR 0.1-0.4? and 0.4-0.9?
50-70mg/kg (total body weight)
50mg/kg
20mg/kg
How long after sugammadex should roc (0.6mg/kg) be re-administered?
6hrs- 2x elimination half-life of sugammadex, but there will be interpatient variability
What are some benefits of TEA?
-superior analgesia cf systemic opioids for many indications including: rib fractures, open colonic resection
-reduced pulmonary morbidity & rates of pneumonia & duration of mechanical ventilation (probably due to early mobilisation, reduced opioid consumption, improved cough)
-decreases the duration of postoperative ileus; some studies suggest it promotes early return of gut function & reduces risk of anastomotic leak, provided systemic haemodynamic effects of TEA are adequately controlled (sympathetic supply of abdo viscera is T6-L1, PSNS supply (vagus) not blocked with TEA, so neuraxial provides sympatholysis with maintained parasympathetic innervation, so gut contracted, sphincters relaxed, peristalsis normal). Cochrane R/V 2016 1100pts abdo surg reduced time to first flatus/bowel movement w TEA vs opioid.
-reduced mortality with TEA after rib fracture, colectomy or lung resection (retrospective data) & after a range of intermediate-to-high risk non-cardiac surgery (retrospective cohort study)
-multiple retrospective studies show reduced rumour recurrence rate after TEA or PVB- through opioid sparing (morphine impairs NK cell activity & promotes tumor growth) & attenuation of the stress response which impairs host immune function
-attenuates postoperative neurohormonal stress response (catecholamine levels increase LV afterload & HR, decreasing time for coronary perfusion (stenotic coronaries don’t dilate w SNS stimulation); Raised CRH levels reduce cardiac NO release & increase endothelin production; stress induces a pro-coagulatory state in the absence of trauma; pro-inflammatory response after stressful event may activate MMPs leading to plaque instability)
-Some studies suggest it decreases postoperative cardiac morbidity & mortality eg. after cardiac surgery (better pain relief & reduction in post-op stress response & SNS activity reduce myocardial O2 demand)
What proportion of perioperative mortality is accounted for by cardiovascular causes in high-risk patients? low-risk?
63%
30%
What sensory dermatomal level is required for neuraxial for caesarean or postpartum tubal ligation?
T4
What sensory dermatomal level is required for neuraxial for THR, ORIF femur or hip, cervical cerclage, urological procedures?
T10
What sensory dermatomal level is required for neuraxial for peri-anal procedures?
S1
What sensory dermatomal level is required for neuraxial for TKR, knee arthroscopy?
L1
What sensory dermatomal level is required for neuraxial for foot surgery?
L2
Is chronic HIV infection a contraindication to spinal anaesthesia?
No, since CNS is infected early in the course of the disease
Is HSV or VZV a contraindication to neuraxial?
Yes during primary infection (viremia) but secondary infection (manifest with oral or genital lesions) is not provided needle not inserted through lesion.
Management of neuraxial in patients with preload-dependent cardiac lesions or hypovolemia?
Only initiate NA once volume status normalised.
Invasive BP monitoring.
Vasopressors.
Fluid administration.
Incremental initiation of neural blockade.
Is neuraxial anaesthesia contraindicated in pts with intracranial mass lesion or raised ICP?
yes, as risk cerebral herniation
