NON-OPIOID ANALGESIA & THE IMPLICATIONS OF ANESTHETIC DRUGS IN THE PERI-ANESTHETIC ARENA AMANDA AFFLECK CRNA

Transcription

1 NON-OPIOID ANALGESIA & THE IMPLICATIONS OF ANESTHETIC DRUGS IN THE PERI-ANESTHETIC ARENA AMANDA AFFLECK CRNA

2 OR, ANESTHESIA, WHY DO THEY DO THAT?

3 OUTLINE Neurotransmission of pain Arachidonic Acid pathway Dexamethasone, toradol, celecoxib Gabapentin Subarachnoid anesthesia Mechanisms of action Hemodynamic changes Assessment of the level Neuraxial opioids Respiratory depression Pruritus NMDA receptor Magnesium Neuromuscular blockade & reversal Ketamine Clinical equations

4 NEUROTRANSMISSION OF PAIN

5 Afferent: toward the target organ Efferent: away from the target organ

6 ARACHIDONIC ACID PATHWAY

7 DEXAMETHASONE Inhibits arachidonic acid metabolism Anti-emetic properties Ideal opioid-sparing effect is when given pre-operatively however.. Anesthesiology , Vol.115,

8 NSAIDS: TORADOL Main anti-inflammatory action is inhibition of biosynthesis of prostaglandin Very effective Inconclusive evidence whether it contributes to anastomotic leakage in bowel surgery

9 TORADOL & RENAL FUNCTION Toradol blocks dilatory effect of PGE 2 ACE-I s block AT-II s constriction of efferent arteriole

10 TORADOL & PREGNANCY Do not give in 3 rd trimester due to risk of premature closure of the ductus arteriosus.

11 NAIADS: CELECOXIB

12 NSAIDS: CELECOXIB If patient received Celecoxib pre-operatively, hold ketorolac for 12hours, as platelet inhibition may prolong bleeding time Increased cardiovascular risk with prolonged use

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15 GABAPENTIN

16 GABAPENTIN

17 SUBARACHNOID ANESTHESIA & ANALGESIA the ca ˈTHēkə/ noun 1. the loose sheath enclosing the spinal cord.

18 NEURAXIAL ANESTHESIA Spinal, Epidural, and Caudal Anesthesia Alan J.R. Macfarlane Richard Brull and Vincent W.S. Chan Basics of Anesthesia, Chapter 17,

19 SUBARACHNOID ANESTHESIA Local anesthetic is deposited into the CSF, working directly on the nerves and spinal cord to stop impulse transmission. Opioids placed in the CSF block pain signals at the spinal cord for up to 18 hours. Subarachnoid space

20 ANATOMY

21 SPINALS Specific gravity of CSF = g/dl

22 EPIDURALS

23 ORDER OF NERVE FIBER BLOCKADE B fibers: sympathetic efferent A-delta: pinprick, temperature C fibers: sympathetic, cold A-gamma: muscle tone A-beta: proprioception, touch A-alpha: motor

24 Sympathetic blockade (temperature) may vary from 0 to 4 segments higher than the sensory block level (pain/light touch), which is 2 segments higher than motor blockade. T6/xiphoid T10/umbilicus T12/symphysis pubis

25 IMPORTANT DERMATOMES C3-5 phrenic nerve, diaphragm Clavicle = C4 Thumb = C6 T1-4 cardioaccelerator Nipple = T4 Xiphoid = T6 T5-L1 sympathetic outflow Umbilicus = T10

26 SYMPATHETIC BLOCKADE T5-L2 peripheral sympathetic innervation

27 TYPICAL SPINAL ANESTHETIC Sympathectomy is 1-2 dermatomes above the sensory loss.

28 C-SECTION

29 NEURAXIAL OPIOIDS The opioid s penetration of spinal tissue is proportional to it s lipid solubility. Fentanyl (lipophilic) vs Morphine (hydrophilic) Intrathecal Morphine: onset of analgesia minutes duration of action hours window for respiratory depression 6-18 hours after dose Intrathecal Fentanyl: onset of analgesia 5-10 minutes duration of action 2 hours window for respiratory depression within 30 minutes

30 RESPIRATORY DEPRESSION WITH NEURAXIAL OPIOIDS Mechanism Lipophilic Opioids (e.g., fentanyl) Hydrophilic Opioids (e.g., morphine) Vascular uptake (by the epidural or subarachnoid venous plexuses and circulation) to the respiratory center in the brainstem Rostral spread via direct perimedullary vascular channels ++ + Dural penetration of opioids + ++ Rostral spread via the aqueous cerebrospinal fluid to the brainstem + +++

31 PRURITUS

32 PRURITUS The spinal trigeminal nucleus is rich in opioid receptors

33 CAUSATIVE THEORIES OF PRURITUS Itch center the spinal trigeminal nucleus, located in the medulla An integrative center for sensory input from the face Known as the itch center Activated by cephalic migration of neuraxial opioids & activation of 5-HT3 receptors by opioids Itch neurons in the spinothalamic tract of the dorsal horn of the spinal cord Normal inhibition of these is inhibited by opioids

34 CAUSATIVE THEORIES OF PRURITUS 5-HT3 modulation 5-HT3 receptors are abundant in the dorsal horn of the spinal cord & the spinal tract of the trigeminal nerve in the medulla Activation of spinal serotonin receptors by opioids Pain & Pruritus Both are transmitted by the same sensory neurons (unmyelinated C-fibers) Activation of Mu-opioid receptors Opioids act on Mu, Delta, & Kappa opioid receptors Mu: analgesia, sedation, euphoria, itching, nausea, respiratory depression, constipation

35 TREATMENT 5-HT3 antagonists (ondansetron) More effective on morphine-induced pruritus Morphine is less lipid-soluble therefore higher residual opioid concentration in the CSF and greater cephalic migration Peak effect of Zofran is about 15 minutes, blocking the 5-HT3 receptors before morphine can activate them Onset of spinal fentanyl is quicker, therefore not as effective

36 TREATMENT Agonist-antagonist: Nalbuphine (Nubain) Blocks Mu receptor not Kappa Relieves Mu symptoms without blocking analgesic effects of opioid Equipotent to morphine

37 TREATMENT H 1 antagonist Diphenhydramine, Hydroxyzine The cause is not histamine release but the sedation provided may be helpful Propofol Anti-pruritic via inhibition of signal transmission in the spinal cord Sub-hypnotic dose Narcan Will reverse the analgesic effects

38 C4 clavicle T4 nipple line T6 xiphoid process T10 umbilicus

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40 NMDA RECEPTOR

41 NMDA RECEPTOR

42 NMDA ANTAGONISTS: MAGNESIUM

43 MAGNESIUM & NEUROMUSCULAR BLOCKADE

44 MAGNESIUM & NEUROMUSCULAR BLOCKADE

45 SUGAMMADEX REVERSAL

46 NMDA ANTAGONISTS: KETAMINE

47 KETAMINE

48 KETAMINE Dissociative anesthesia: catatonia, amnesia, analgesia Cardiovascular stimulation: excitation of the central sympathetic nervous system & inhibition of re-uptake of NE Return to baseline within 15 minutes Respiratory: bronchodilator, drive minimally affected, upper airway reflexes remain intact, increased salivation Neuro: hallucinogenic, increased CMR O2, CBF & ICP Dosing: 1-2mg/kg vs 1mg/kg divided over 3 hours vs 10mg intermittently

49 NMDA RECEPTOR

50 HELPFUL EQUATIONS Ideal Body Weight Female: 5 feet= 45.5kg kg per inch Male: 5 feet= 47kg kg per inch Adjusted Body Weight [ (Actual-Ideal)/3] + Ideal *** Use Adjusted Body Weight for weight-base hematologic calculations

51 HELPFUL EQUATIONS Estimated Blood Volume: Hct? Female 65 x Adjusted Body Weight = mls Male 70 Child 75 Infant 80 Newborn Start [start x (EBL/EBV)] Start = starting Hct

52 HELPFUL EQUATIONS Volume of PRBCs to administer to achieve desired Hct PRBCs ml = EBV [(desired-current)/70]

53 HELPFUL EQUATIONS Transfusion: 1 unit PRBCs raises Hgb 1 g/dl FFP 10-15mlkg decreases INR 10% 1 pack of platelets increases count by 50,000 Albumin 30ml/kg increases INR 15-25% Chloride content 145meq/L, almost as high as normal saline

54 HELPFUL EQUATIONS Respiratory Normal PaO2 on room air (age adjusted) 102-(age/3) SpO2 90, 80, 70 = PaO2 60, 50, 40 CO2 & potassium: for each 10 mmhg drop in CO2, K + drops 0.5 meq/l Time left on an E tank: 0.3 x psi = liters in tank, divide by lpm flow = time left in minutes

55 HELPFUL EQUATIONS 1:1000 = 1 mg/ml 1:10,000 = 100 mcg/ml 1:100,000 = 10 mcg/ml 1:200,000 = 5 mcg/ml 1:400,000 = 2.5 mcg/ml

56 THANK YOU