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Pediatric Anesthesia

Presented May 2003. Pediatric Anesthesia. Abdulaziz Hisham Al Gain. Development: Organogenesis - 1 st 8 weeks Organ function - 2 nd trimester Body mass - 3 rd trimester. Changes in cardiovascular system: Removal of placenta from circulation

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Pediatric Anesthesia

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  1. Presented May 2003 Pediatric Anesthesia Abdulaziz Hisham Al Gain

  2. Development: • Organogenesis - 1st 8 weeks • Organ function - 2nd trimester • Body mass - 3rd trimester

  3. Changes in cardiovascular system: • Removal of placenta from circulation • Increasing of systemic vascular resistance • Decreasing of pulmonary vascular resistance • True closure of PDA ~ 2-3 weeks  critical transitional circulation • Myocardial cell mass less developed  prone to biventricular failure, volume loading, poor tolerance to afterload, heart rate-dependent CO* * True for young infants

  4. Changes in pulmonary system: • Small airway diameter - increased resistance • Little support from the ribs • VO2 2x > adults • Diaphragm and intercostal muscles do not achieve type-1 adult muscle fibers until age 2 • Obligate nasal breathers

  5. Airway difference: • Large tongue • Higher located larynx • Epiglottis short and stubby, angled over the inlet • Angled vocal cords  we must rotate ETT to correct lodging at anterior comissure • Narrowest portion is cricoid cartilage

  6. Chest wall/Respiratory difference: • Ribs are horizontal in neonates (vertical in adults) • Ribs and cartilages are more pliable • Chest wall collapse more with increased negative intrathoracic pressure • Atelectasis is more common •  FRC •  number of alveoli • Alveolar ventilation/FRC: Adults = 1.5:1 Infants = 5:1 ( respiratory rate)

  7. Kidney and liver difference: • Low renal perfusion pressure, immature GF, TF, obligate Na loser in the 1st month of life • Complete maturation @ 2 years of age • Impaired liver enzymes, including conjugation react. • Lower levels of albumen and proteins - prone to neonatal coagulopathy, and less drug bound  higher drug levels

  8. GI system and thermoregulation: • Full coordination of swallowing ~ 4-5 months  increased risk for GE reflux • Large body surface area/weight • Limited ability to cope stress • Minimal ability to shiver in 1st 3 months • Heat whole body including the head

  9. Pharmacology/dynamics: • Increased total body water: • Large initial dose required • Less fat  longer clinical drugs effect • Redistribution of the drug into muscle will increase duration of clinical effect (fentanyl) • Consider liver and kidney immaturity

  10. Volatile anesthetics • Isoflurane: • Less myocardial depression than Halothane • Preservation of heart rate • CMRO2 reduction rate Desflurane: • Increased incidence of coughing, laryngospasm, secretions • Concern of hypertension and tachycardia from sympathetic activation

  11. Volatile anesthetics (2) • Sevoflurane • Less pungent than Isoflurane • Concern of compound A (nephrotoxicity) • Most suitable for induction Remember: MAC for potent volatile anesthetics is increased in neonates, but may be lower for sicker neonates and premies

  12. Induction drugs: • Methohexital: • 1-2 mg/kg i.v. or 25-30 mg/kg per rectum • Side effects: burning hiccup apnea extrapyramidal syndrome • Contraindication: temporal lobe epilepsy • Thiopental: • 5-6 mg/kg i.v. • Caution in low fat children and malnourished

  13. Induction drugs: • Propofol: • 3 mg/kg i.v. (until 6 years of age) • Pain on injection - 0.2 mg/kg Lidocaine i.v. Ketamine: • 10 mg/kg IM, PR, orally • Increased salivation Contraindications: Increased ICP Open globe injury

  14. Induction drugs: • Benzodiazepines: Diazepam: • 0.1-0.3 mg/kg orally • T1/2 80 hours  contraindicated < 6 months Midazolam: • Only FDA benzodiazepine approved in neonates • 0.1-0.15 mg/kg IM • 0.5-0.75 mg/kg orally • 0.75-1.0 mg/kg rectally • Reduce dose in drugs  cause Cytochrome P- 450 inhibition

  15. Induction drugs: • Narcotics: Morphine: • Increased permeability of blood/brain barrier • 50 mcg/kg IV Meperidine: • Less respiratory depression than morphine • Be cautious in long term administration because of its metabolite normeperidine

  16. Induction drugs: • Narcotics(2): Fentanyl: • 12.5 mcg/kg IV during induction provides stable cardiovascular response • 1-2 mcg/kg adjuvant to anesthesia • Stable cardiovascular response Alfentanyl and Sufentanyl: • More rapid clearance than adults • Can cause parasympatholysis  bradycardia, hypotension

  17. Induction drugs: • Muscle relaxants: Succinylcholine: • 2.0 mg/kg IV; 4.0 mg/kg IM • Consider Atropine 10-15 mcg/kg given prior SUX • Potential side effects: Rhabdomyolysis Hyperkalemia Masseter spasm MH

  18. Induction drugs: • Muscle relaxants(2): • If tachycardia desired - Pancuronium • Mivacurium - brief surgeries, beware of histamine release, bronchospasm • Rocuronium - useful for modified RSI, and can be administered IM (1 mg/kg)

  19. Muscle relaxants - Summary:

  20. Premedication: • Almost all sedatives are effective • Usually not necessary < 6 months • Most common route used is oral • Side effects: Oral - slow onset IM - pain, sterile abscess Rectal - uncomfortable, defecation, burn Nasal -irritating Sublingual -bad taste

  21. Pharmacological premedication options • Role when awake separation of child from parent before induction is planned. • Its success may be judged by the peacefulness of the separation. • Large volume of literature indicates lack of clearly ideal technique http://metrohealthanesthesia.com/edu/ped/pedspreop6.htm

  22. Pharmacological premedication options • Midazolam (Versed) • PO: 0.5 to 1.0 mg/kg up to 10 mg max. • Bioavailability = 30% • Peak serum levels after about 45 minutes • Peak sedation by about 30 minutes • 85% peaceful separation • Mix with grape concentrate or acetaminophen (Tylenol) syrup or elixir or Motrin Suspension (10 mg/kg of the 2% suspension)

  23. Pharmacological premedication options (3) • Midazolam (Versed)(2) • Nasal: 0.2 to 0.6 mg/kg • Peak serum level in 10 minutes • 0.2 mg/kg same as 0.6 mg/kg except • 0.2 mg/kg did not delay recovery • 0.6 mg/kg may delay extubation • Possible concern: animal studies reveal neurotoxicity after topical applicaton.

  24. Pharmacological premedication options (4) • Midazolam (Versed)(3) • Sublingual: 0.2-0.3 mg/kg as effective as 0.2 mg/kg intranasal • Rectal: 0.35 to 1.0 mg/kg • Some effect by 10 minutes, peak effect 20-30 minutes. • 1.0 mg/kg did not delay PACU discharge.

  25. Pharmacological premedication options (5) • Methohexital (Brevital) • Rectal 25 to 30 mg/kg as 10% solution in warm tap water • 85% sleeping within 10 minutes = rectal induction of GA (very peaceful separation) • Sleep duration: about 45 to 90 minutes • 25 mg/kg did not delay recovery in one study, but some delay may be expected after a short (less than 30-minute) case.

  26. Pharmacological premedication options (6) • Ketamine • PO: 6 to 10 mg/kg • May slightly prolong time to discharge after a short case • IM: 3 to 4 mg/kg sedation; • 2 mg/kg did not delay recovery • 6 to 10 mg/kg = IM induction of general anesthesia • 10 mg/kg: as effective as Midazolam 1 mg/kg but some delay in recovery may be expected

  27. Pharmacological premedication options (7) • Midazolam + Ketamine: • PO 0.4 mg/kg + 4 mg/kg respectively • 100% successful separation • 85% easy mask induction • Doubling dose leads to "oral induction of general anesthesia" in most cases. Lasts 30 to 60 minutes.

  28. Pharmacological premedication options (8) • Fentanyl "lollipops" (oral transmucosal Fentanyl) • 15 to 20 mcg/kg • Increased volume of gastric contents • Nausea and vomiting • Pruritus • Hypoventilation (SpO2 <90)

  29. Pharmacological premedication options (9) • Metoclopramide (Reglan) PO or IV: 0.2 mg/kg • Ranitidine (Zantac) PO 2.5 mg/kg • EMLA cream: Eutectic mixture of Lidocaine and Prilocaine. For cutaneous application by occlusive dressing one hour preoperative • Glycopyrrolate: consider for selected patients for planned airway instrumentation; e.g.: fiberoptic endoscopy, oral or upper airway surgery, cleft palate)5-10 mcg/kg IV or 10 mcg/kg IM

  30. Preoperative interview: http://metrohealthanesthesia.com/edu/ped/pedspreop4.htm

  31. Fasting: • Clear liquids - 2-3 h before the procedure • If infants are breast fed - 4 h before the procedure • For older patients = the adults rule • Be aware of dehydration

  32. Induction of Anesthesia: • Inhalational induction: • Younger than 12 months • After the induction, place the intravenous catheter • Use suggestions in older child (pilot’s mask) • In a case of difficult airway - Fiberoptic intubation

  33. Induction of Anesthesia: • Rectal induction: • Methohexital • Thiopental • Ketamine • Midazolam • Technique no more intimidating than rectal temperature measurement • Usual time of onset ~ 10-15 min

  34. Induction of Anesthesia: • Intramuscular induction: • Most common used Ketamine • Disadvantage painful needle insertion • Advantage: reliability

  35. Induction of Anesthesia: • Intravenous induction: • The most reliable and rapid technique • Disadvantage - starting intravenous line • If patient is older ask the patient • If you insert IV line: I. Do not allow the patient to see it II. Use EMLA cream III. If use local - ask the patient if there is any sensation on puncture

  36. Patient with full stomach: • Treat the same as adult with full stomach: • RSI with ODL using cricoid pressure • Tell the patient that will feel “touching on the neck” • Be aware of  VO2 (desaturation) • 0.02 mg/kg of Atropine administer before SUX to avoid bradycardia (usually after 2nd dose) • Use Rocuronium 1.2 mg/kg • Use Succinylcholine 1-2 mg/kg  if really need short duration (difficult airway)

  37. Endotracheal tubes: 4 + (1/4) (age) = size; 12 + (1/2) (age) = depth

  38. Intravenous fluids: Include if present: Fluid deficits Third spaces losses Hypo/hyperthermia Unusual metabolic fluids demands

  39. Fluid requirements in neonates: • During the 1st week reduced fluid requirements: Day 1 - 70 ml/kg Day 3 - 80 ml/kg Day 5 - 90 ml/kg Day 7 - 120 ml/kg • Concern is immaturity of the neonatal kidney • The volume of extracellular fluids in neonates is large • Consider use of radiant warmers, and heated humidifiers - decrease insensible water loss • Use LR for replacement, D5% with 0.45 NS by piggyback

  40. Packed Red Blood Cells: The use has diminished because of disease transmission (HIV, Hep C,B. etc) Blood volume: Premature infant - 100 -120 ml/kg Full-term infant - 90 ml/kg 3-12 month old child - 80 ml/kg 1 year and older child - 70 ml/kg EBV (starting Hct - target Hct) MABL = Starting Hct

  41. Packed Red Blood Cells (2): • Child usually tolerates Hct ~ 20 in mature children • If: Premature, Cyanotic congenital disease Hct ~ 30  O2 carrying capacity • No one formula permits a definitive decision • Replace 1ml blood with 3 ml of LR • Lactic acidosis is a late sing of decreased O2 carrying capacity • Be aware of blood disorders (sickle cell disease)

  42. Fresh Frozen Plasma: • Use to replenish clotting factors during massive transfusion, DIC, congenital clotting factor deficits • Usually replenished if EBL = 1-1.5 TBV • A patient should be never given FFP to replace bleeding that is surgical in nature • If transfused faster than 1.0 ml/kg/min severe ionized hypocalcemia may occur • If occurs - Rx. with 7.5-15 mg/kg Ca++ gluconate • Ionized hypocalcemia can occur in neonates frequently because of decreased ability to mobilize Ca++ and metabolize citrate

  43. Ionized Hypocalcemia:

  44. Platelets: • Find etiology - TTP, ITP, HIT, DIC, hemodilution after massive blood transfusion • Consider transfusion if Platelets < 50.000 • In certain hospitals platelet function test is available • If Platelets < 100.000 and EBL = 1-2 TBV - transfusion more likely • If Platelets > 150.000 and EBL > 2 TBV transfusion more likely

  45. Monitoring the Pediatric Patients: • Must be consistent with the severity of the underlying medical condition • Minimal monitoring: I. 5 ASA monitors II. Precordial stethoscope III. Anesthetic agent analyzer • Use of capnograph and O2 analyzers is associated with high incidence of false alarms from: movement artifact light interference electrocautery

  46. Special Monitoring the Pediatric Patients: • Intraarterial catheter - most common radial • Pulmonary artery catheters are rarely indicated because equalization of the pressure right/left heart • In a case of severe multisystem organ failure insertion of PAC might be particularly useful • Multilumen catheters are valuable in ICU patients • In a case of rapid fluid replacement peripheral venous catheter might be very useful • Short-term cannulation of femoral/brachiocephalic or umbilical vein may be life-saving

  47. Anesthesia Circuits: • Nonrebreathing circuits: 1. Minimal work of breathing 2. Speeds-up rate of inhalational induction 3. Compression and compliance volumes are less (small circuit volume) • Use of Mapleson D system is recommended in children < 10 kg More sensitive to changes in gas flow More sensitive to humidification Actual delivered volume is greater than other systems

  48. Mapleson D Circuit: Gas disposition at end-expiration during spontaneous ventilation Gas disposition at controlled ventilation

  49. Neonatal Anesthesia: • Understand differences in Physiology Pharmacology Pharmacodynamic response • Most of the complications that arise are attributable to a lack of understanding of these special considerations prior to induction of anesthesia • Be aware of: Sudden changes in hemodynamics Unexpected responses Unknown congenital problem

  50. Neonatal Anesthesia (2): • Children < 1 year old have more complications: I. Oxygenation II. Ventilation III. Airway management IV. Response to volatile agents and medications • Stress response is poorly tolerated • Consider: 1. Organ system immaturity 2. High metabolic rate 3. Large ratio body surface/weight 4. Ease of miscalculating a drug dose

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