premedication.ppt for medical students and anesthesia

premedication ppt of medical students and anesthesia orders

1. PREMEDICATION, FASTING GUIDELINES, FLUID AND ELECTROLYTE BALANCE IN PAEDIATRIC PATIENTS INCLUDING MASSIVE TRANSFUSION Moderator: Prof Shende Dr Manpreet Kaur Presentors : Dr Athipro Kayina Dr Suryatheja

2. Preoperative Fasting . First published guideline : Joseph Lister(1882) ; British surgeon “while it is desirable that there should be no solid matter in the stomach when chloroform is administered, it will be found very salutary to give a cup of tea or a beef-tea about two hours previously.”

3. The modern practice of fasting prior to an operation began with Dr. Curtis Mendelson’s observations in 1946 He reported that surgical patients who ingested food shortly before their surgical procedure were more likely to regurgitate their stomach contents with severe consequences ( aspiration pneumonitis )

4. Fasting from midnight reduces pulmonary aspiration risk Lliungvist O. Review: Preoperative fasting. Br J Surg 2003 . Prolonged fasting - Peri -operative complications Dry mouth Hunger Confusion Headache Nausea and vomiting Hypovolaemia Hypoglycaemia Ketoacidosis in diabetics Brady M et al. Preoperative fasting for adults to prevent perioperative complications. Cochrane Database of Systematic Reviews 2003

5. FASTING GUIDELINES Solids- Light meal : 6h Heavy meal : 8h (fatty meal) Infant Formula- 6h Non human Milk- 6h Breast Milk- 4h Clear Fluids- 2h (water, fruit juice without pulp, black coffee without milk)

6. Solids It requires more time than liquids to be emptied from the stomach Why??

7. Gastric emptying Solids – Zero order kinetics of elimination (grams emptied per minute was constant and unaffected by meal volume) Larger particles require a longer period of digestion to break them down into a size suitable to exit through the pylorus Liquids – First order of kinetics of elimination (mL/min gastric emptying increase with increasing meal volume) 8

8. Gastric emptying For liquids, the principal determinant of rate of gastric emptying is volume and, secondarily, composition. Gastric emptying Rate - Volume+Composition If the liquid is low in nutrients (e.g. water), there is an exponential relationship between volume and rate of emptying - large volumes empty at an faster rate than small volumes 9

9. The rate of gastric emptying of any meal also depends on nutrient density. Nutrient density is sensed by osmoreceptors and chemoreceptors in small intestine Relayed to the stomach as inhibitory neural and hormonal messages Delay emptying by altering the patterns of gastric motility. So the presence of fat in the small intestine is the most potent inhibitor of gastric emptying

10. Gastric emptying: liquid vs. solid 11 Which one is faster?

11. Milk Human Milk Liquid Early elimination Formula Feed Solid or liquid Slow Elimination Cow milk Solid and liquid More time

12. PREMEDICATION “The medication which used in preparation of a patient before surgery” GOALS : a)Primary b)Secondary

13. PREMEDICATION The 6 As of Premedication Anxiolysis – the best anxiolytic is the anesthetist who visits the patient and listens to the patient Amnesia Anti-emetic Antacid Anti-autonomic Analgesic

14. Pharmacological Premedication 1. Benzodiazapines 2. Alpha 2 Agonists 3. Opioids 4. Ketamine 5. Anticholinergics

15. 1.Benzodiazapines Midazolam is the premedication of choice in morethan 90% of all routine cases ( Brosius et al. Oral Midazolam premedication in preadoloscents and adoloscents . Anesth Analg . 2002) ( Kain et al.Premedication in the US: A status report. Anesth Analg . 1997) Midazolam – It is a watersoluble BZD with rapid onset time and shorter duration of action than Diazepam

16. Routes of administration: Oral – onset is 15-20 min, peak plasma conc with in 30min , 0.25-1mg/kg Nasal - onset is 10-12min, peak conc with in 10min( irritates nasal mucosa) 0.2-0.3mg/kg Rectal – 1mg/kg Intra muscular - Peak conc with in 45min, but anxiolytic effect within 5min 0.1-0.15mg/kg Intravenous – onset is 3-5min, 0.05-0.1mg/kg

17. Effect lasts for 20-30min Significant Side effects- Paradoxical reactions Postoperative night mares Fearfulness

18. 2. Alpha2 Agonists (Clonidine and Dexmedetomidine ) Reasonable alternatives Advantages- Periop.sedation , Postop.analgesia , Improved periop.hemodynamic stability Anaesthetic requirements

19. Adrenoceptors Alpha-1a, Alpha-1b and Alpha-1d Beta-1, Beta-2, Beta-3 Alpha-2a, Alpha-2b and Alpha-2c Central – Peripheral Presynaptic – Postsynaptic Extrasynaptic (vascular)

20. Alpha- Adrenoceptor Agonists Norepinephrine Epinephrine Dopamine Tizanidine Clonidine(1:220) MPV-2426 Mivazerol Guanfacine Guanabenz Medetomidine Dexmedetomidine (1:1620) Alpha 2 Alpha 1

21. Selected clinical effects Sedation Hemodynamics Ventilation

22. Sedation Dose dependent Minimal respiratory depression Arousable Known action Hyperpolarization of LC neurons - a 2 A -receptor subtype Resembles natural sleep (ICU?) Reversible ( atipamezole ) Amnesia?

23. Anesthesia/Analgesia Sparing Intraop , postop Induction agents, inhalation anesthetics, opioids , midazolam 40% with dexmedetomidine (0.6-0.8 ng / mL ), up to 90% 40% with clonidine (5 mc g/kg po or IV)

24. Hemodynamic effects Combination of effects mediated by: Reduction of central SNS activity (alpha-2a) Reduction of presynaptic NE release (alpha-2a and c) Some vagomimetic activity

25. Effect on Ventilation (Alpha-2) Clonidine , dexmedetomidine Minimal effect on RR, V E , Pa CO 2, Small decrease in V E /ET CO 2 No potentiation of opioid -induced respiratory depression Sedation, upper airway obstruction Irregular RR with large boluses

26. Effects of Alpha-2 Agonists Endocrine  NE release  insulin release  cortisol release  GH release Baroreflexes stay intact (reset) Normal response to vasoactive drugs Attenuates stress response

27. Side Effects Bradycardia , Sinus pause/arrest Orthostatic hypotension Dry mouth Vasoconstriction

28. Dosage- Clonidine (mcg/kg) oral:2.5-5 i.v :1-2 Dexmedetomidine (mcg/kg) i.v : 0.25-1 nasal: 1-2 i.m : 1-2

29. 3. Opioids Opiods became obsolete as a premedication these days because of their side effect profile( unpleasant dysphoria , pre and postop.vomiting ) Oral Transmucosal Fentanyl(OTFC) have been tried previously(10 micro.g /kg) Use- Breakthrough pain in cancer and trauma

30. Sedation/ analgesia before painful procedures Dosage: Fentanyl (mcg/kg) i.v - 0.5-1 Transmucosal-10

31. 4.Ketamine - NMDA Antagonist Different routes for premedication : Intramuscular Ketamine (3-7mg/kg) facilitates inhalational induction with improved mask acceptance Oral(6-10mg/kg): The oral route has several advantages as it is painless, quick and reliable.

32. The Combination of Oral Ketamine and Midazolam given satisfactory anxiolysis compared to either drug alone (Funk et al.Oral preanaesthetic medication for children:double blinded randomized study of a combination of midazolam and ketamine vs midazolam or ketamine alone.Br J Anaesth.2000) Intravenous(1-2mg/kg) Rectal(4-5mg/kg) Nasal transmucosal (5-10mg/kg)

33. 5.Anticholinergics Previously these drugs were used inorder to prevent unwanted a) Autonomic reflexes or bradycardia (Airway instrumentation, nasopharyngeal stimulation , anaesthetic drugs b) Secretions (induction)

34. Atropine Glycopyrrolate Scopalamine

35. Dosage: Atropine – 20mcg/kg Glycopyrrolate - 10mcg/kg ( vagolytic ) - 3mcg/kg ( anti sialogauge ) Scopalamine - 0.3 to 0.6mg iv or im 0.5 mg transdermal patch behind ear

36. Side effects- Temperature elevation, Dry mouth, Flushing, Tachycardia and CNS irritability Atropine fever Central Anticholinergic Syndrome

37. Central Anticholinergic Syndrome: Due to a decrease in the inhibitory acetylcholine activity in the brain. Incidence : 8- 12 % following general anaesthesia and lesser with regional anaesthesia. ( Central Anticholinergic Syndrome — a forgotten entity, BJA Volume 101 December 2008 )

38. Other drugs causing CAS : Benzodiazepines, Opioids, Phenothiazines , Butyrophenones , Ketamine, Etomidate , Propofol , Nitrous oxide, and Volatile inhaled anaesthetics

39. Features Antagonism at muscarinic receptors Central inhibition - Agitated (hyperactive) delirium - typically including confusion, restlessness Peripheral inhibition - hot, dry skin, flushed appearance, mydriasis , tachycardia, decreased bowel sounds and urinary retention.  Seizures, coma and cardiovascular toxicity

40. Smith’s 9 th edition

41. Non Pharmacological Methods 1. Parental Presence at Induction of Anaesthesia (PPIA) 2. Behavioural Intervention

42. 1.Parental Presence at Induction of Anaesthesia (PPIA) : - Controversial strategy in reducing Preop.anxiety and increasing child’s co operation - Though initial studies are in favour of this , recent prospective studies refusing Kain et al .The Yale preoperative anxiety scale: how does it compare to a gold standard? Anesth Analg

43. Assessment of Pre-op Anxiety Modified Yale Preoperative Anxiety Scale ( mYPAS ) categories Activity Emotional expressivity State of arousal Vocalization Use of parents Score: 5-22 (Higher score indicate more distress)

44. Induction compliance checklist Crying, tears in eyes Turns head away from mask Verbal refusal, says ‘no’ Verbalization indicates fear or worry Pushes mask away with hand Covers mouth/nose with hands/arms Hysterical crying Kicks, flails legs/arms, arches back Requires physical restraint Complete passivity (Higher score indicate poor behaviour compliance)

45. 2. Behavioural Intervention: Video games, Interactive computer packages, Clowns , Hypnosis, Parental acupuncture. ( Mcgraw et al, 2001 proposed that child’s anxiety reflects those of parents)

46. Thank you ..