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PEDIATRIC ANESTHETIC CONSIDERATIONS

PEDIATRIC ANESTHETIC CONSIDERATIONS. KIDS ARE NOT SMALL ADULTS. Respiratory System Anatomy…. Tongue relatively large Larynx more cephalic and anterior C 3-4 in child C 4-5 in adult Epiglottis long and stiff Protrudes posterior at 45 o. Respiratory System Anatomy….

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PEDIATRIC ANESTHETIC CONSIDERATIONS

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  1. PEDIATRIC ANESTHETIC CONSIDERATIONS

  2. KIDS ARE NOT SMALL ADULTS

  3. Respiratory System Anatomy… • Tongue relatively large • Larynx more cephalic and anterior • C 3-4 in child • C 4-5 in adult • Epiglottis long and stiff • Protrudes posterior at 45o

  4. Respiratory System Anatomy… • Narrowest diameter upper airway at cricoid ring (glottis in adult) • Susceptible to airway obstruction • Trachea short—4-5.7cm vs. 6-8cm • Equidistant bronchi from trachea—increased chance of endobronchial intubation • Lung alveoli—20 mil at birth, 300 mil age 8

  5. Respiratory Physiology… • Alveolar ventilation: O2 requirement • Infant: 100-150 cc/kg/min • Adult: 60cc/kg/min • Increase in Va 2o increased metabolic rate in infant • FRC (functional residual capacity) exp. reserve vol. + residual vol.

  6. Respiratory Physiology… • FRC— • acts as a buffer to maintain PaO2 during inspiration and expiration • smaller reserve • less O2 during apnea • Va/FRC (adult) = 1.5/1 • Va/FRC (infant) = 5/1

  7. Respiratory Physiology… • Lung mechanics • Increased resistance 2o narrow nasal passage • Resp. rate increased (24-30 vs. 20) • Oxygen transport (left shift) • Incr. affinity of hemoglobin for O2 • Favors uptake not unload • Less O2 available to tissues, therefore increased HR and CO necessary

  8. Cardiovascular Anatomy & Physiology… • Ventricle in infant • Right > Left (size and thickness) • Less compliant • Pulse rate is the major determinant of CO in infant • New born—130; adult—77 • Sinus dysrhythmia common • BP; infant—70/43, adult—122/80

  9. Cardiovascular Anatomy & Physiology… • Response to hypoxia • Metab. demand for O2 - 60% > adult • Va/FRC is high (5:1) • Hypoxemia can develop rapidly • Bradycardia is always initial response to hypoxia • Treat unexplained bradycardia immediately with O2

  10. Pediatric Pharmacology… • Brain, heart, liver, and kidneys = 18% of body weight in infant vs. 5% adult • Larger fraction of drug distributed to these organs vs. muscle and fat • Infants have less plasma protein conc. • More perm. BBB • Hepatic enzymes—inactive/immature • GF less in infant—slower elimination of drugs and metabolites

  11. Pediatric Sedation… • ASA status—I’s and II’s • Risk factors for pediatric sedation • Age—the younger the patient the greater the risk • Respiratory arrest is the greatest liability • Rule of thumb “adults will have a cardiac arrest, children will have a respiratory arrest”

  12. Evaluation of Physical Risks During Sedation… • History • Syndrome associated with difficult airway? • Does the child snore at night? • Most crucial question in history • Accurate predictor of obstruction • Most common etiology is hypertrophy of adenoids and tonsils • Problems with emergency airway

  13. Evaluation of Physical Risks During Sedation… • History • Previous surgeries and anesthetics • Very good indicator of success/failure • Physical exam • Differences in child’s airway • Kids are smaller • Smaller mouths • Mallampati evaluation

  14. Evaluation of Physical Risks During Sedation… • Physical exam • Disproportionate sized features • Relatively large epiglottis • Floppier epiglottis • Narrowest part of airway is subglottic • Glottis is prone to laryngospasm during sedation • Thyromental distance

  15. Evaluation of Physical Risks During Sedation… • Physical exam • URI • Most children have 2-10 viral respiratory tract infections per year • Is a snotty nose just a cold or day 1 of a viral infection? • More prone to laryngospasm, bronchospasm, coughing, mucus plugging

  16. Factors Influencing the Outcome of Sedation • The best success rate with children is 60-80 % (20-40% failure) • Age • Cognitive development • Degree of expression of fear • Flight response of crying/screaming • Child temperament

  17. SEDATION PHARMACOLOGY • Sedative Hypnotics • Phenothiazines/Antihistamines • Benzodiazepines • Narcotics • Barbiturates • Reversal Agents

  18. SEDATIVE HYPNOTICS CHLORAL HYDRATE

  19. CHLORAL HYDRATE • “Classic” pediatric sedative • Moderately effective sedative/hypnotic • Mild depressant of the central nervous system • Trichloroethanol is the active metabolite

  20. CHLORAL HYDRATE • Often combined with other agents • No analgesic properties • No reversal agent • May cause GI irritation, respiratory depression, hypotension and paradoxical excitement • Hepatic elimination

  21. CHLORAL HYDRATE • Side effects: • Nausea • Vomiting • Diarrhea • Flatulence • disorientation • excitement • rash

  22. CHLORAL HYDRATE • DOSE • 50-75 mg/kg PO • ONSET • 30 - 60 minutes PO • PEAK EFFECT • 1-2 hours PO

  23. CHLORAL HYDRATE • WORKING TIME • 45-60 minutes • DURATION • 7-10 hours

  24. ANTIHISTAMINES DIPHENHDRAMINE HYDROXYZINE

  25. DIPHENHYDRAMINE • Trade name: Benadryl • H1 receptor antagonist with anticholinergic and sedative effects • Partially inhibits vasodilator effect of histamine on peripheral vascular smooth muscle

  26. DIPHENHYDRAMINE • USES: • Antiemetic • Antivertigo • Treatment of allergic reactions • Treatment of extrapyramidal reactions

  27. DIPHENHYDRAMINE • DOSE: • 0.5 to 1 mg/kg q6h (25-50 mg) PO • maximum 300 mg/day • ONSET: • <15 minutes PO

  28. DIPHENHYDRAMINE • PEAK EFFECT: • 2 hours PO • DURATION: • < 7 hours PO

  29. DIPHENHYDRAMINE Children are at an increased risk of paradoxic CNS stimulant effects such as restlessness, insomnia, tremors, euphoria and seizures

  30. HYDROXYZINE • Vistaril/Atarax • Antihistamine • Anxiolytic • Sedative • Hepatic elimination

  31. HYDROXYZINE • DOSE: • .6 - 1 mg/kg PO • ONSET: • 15 -30 minutes PO • PEAK EFFECT: • 30 - 60 minutes PO • DURATION: • 2- 4 hours

  32. PHENOTHIAZINES PROMETHAZINE

  33. PROMETHAZINE • Phenothiazine derivative • H1 receptor antagonist with good sedative, antiemetic, anticholinergic and antimotion sickness effects • Hepatic elimination

  34. PROMETHAZINE • Uses: • Antiemetic • Adjunct to other sedatives (antiemetic and co-sedative) • Used alone for mild sedation or to control gagging

  35. PROMETHAZINE • DOSE: • 1 mg/kg PO • ONSET: • 15 - 30 minutes PO • PEAK EFFECT: • <2 hours PO • DURATION: • 2-8 hours PO

  36. PROMETHAZINE • Extrapyramidal reactions • Use with caution in children with severe cardiovascular or liver disease

  37. BENZODIAZEPINES DIAZEPAM MIDAZOLAM

  38. DIAZEPAM • DOSE: • 0.25 - 0.5 mg/kg PO • ONSET: • 30 minutes to 1 hour PO • PEAK EFFECT: • 1 hour PO • DURATION: • 2 - 6 hours PO

  39. MIDAZOLAM • Trade name: Versed • Short acting • Water soluble • Greater amnesia than with diazepam • Dose dependent respiratory and circulatory depression • Four times more potent than diazepam

  40. MIDAZOLAM • DOSE: • 0.5 mg/kg PO • ONSET: • 20-30 minutes PO • PEAK EFFECT: • 30 minutes PO • DURATION: • 2-6 hours PO

  41. MIDAZOLAM - INTRANASAL • Not permitted with Level 1 • Burning of the nasal mucosa is a major drawback • Need to make sure that the drug is absorbed through the nasal mucosa and not swallowed

  42. FLUMAZENIL • Trade Name: Romazicon • Competes with benzodiazepines for the GABA/benzodiazepine receptor • Has a much shorter duration of action than most of the benzodiazepines • Used as a reversal agent for benzodiazepine agonists

  43. FLUMAZENIL • DOSE: • IV/IM 0.1 mg or 3mcg/kg (max dose is 1 mg) • ONSET: • 1 - 2 minutes IV • PEAK EFFECT: • 2 - 10 minutes IV • DURATION: • 45 - 90 minutes IV

  44. FLUMAZENIL • Precautions • May be associated with seizures in high risk patients. • Patient may become re-sedated so need to monitor patient. • Can cause confusion and agitation

  45. NARCOTICS MEPERIDINE

  46. MEPERIDINE • DOSE: • 1-2 mg/kg PO • ONSET: • 10 - 30 minutes PO • PEAK EFFECT • <1 hour PO • DURATION • 2 - 4 hours PO

  47. MEPERIDINE • Do not use in patients taking MAO inhibitors • Can cause abnormal behavior or dysphoria • Use with caution in patients who are high risk or hypovolemic

  48. NALOXONE • Trade Name: Narcan • Pure opioid antagonist • Competitively inhibits opiates at the mu, delta, and kappa receptor sites • Reverses respiratory depression, sedation, hypotension and analgesia • No pharmacologic effects in absence of narcotics

  49. NALOXONE • DOSE: • 0.01 mg/kg IV/IM/SC (titrate to response) • ONSET: • 1 - 2 minutes IV, • 2 - 5 minutes IM/SC • PEAK EFFECT: • 5 - 10 minutes IV/IM/SC • DURATION: • 1 - 4 hours IV/IM/SC

  50. NALOXONE • Abrupt reversal may cause nausea, vomiting, diaphoresis, tachycardia, hypertension, pulmonary edema • Careful monitoring needed because duration of action of opiates may be longer than that of naloxone

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