Neonatal and paediatric anaesthesia

Neonatal and Paediatric Anaesthesia

1. PAEDIATRIC ANAESTHESIA AND MY EXPERIENCE AT DSH Capt Shoaib Bin kashem Trainee Anaesthesilogy

2. INTRODUCTION Dhaka Shishu (Children) Hospital is the largest children hospital in Bangladesh. It is a Government supported tertiary level public hospital for children with 640 beds . A ll indoor facilities including operation Two OT complex- General ot and Cardiac ot

3. SCOPES

4. Children are not little adults! Neonates: 0-30 days old Infants: 1 month to 1 year Children: older than 1 year  Full term neonate: born between 37-40 weeks and aged less than 1 month  Premature neonate: child born before 37 weeks gestation   Extreme preterm neonate: child born less than 28 weeks gestation A 10-12 yrs old child thought of anatomically and physiologically small adult

5. Different Anatomy Different Physiology Different Pharmacology Different psychology

6. Airways Head large 1/3 size of adult head 1/9 height of adult 1/27 weight of adult Tongue large Nasal passages narrow Obligate nose breathers until 5 month

7. Airway difference: Large tongue Epiglottis short and stubby Higher located larynx Angled vocal cords Narrowest portion is cricoid cartilage It’s Different

8. Larynx Anterior Cephalad C 4 level Epiglottis long & U shaped Trachea short Neonates → 2 cm cords to carina Cricoid → Narrowest point until 10 yrs

9. More rostral pediatric larynx Infant’s larynx is higher in neck (C2-3) compared to adult’s (C4-5) Larynx C4-5 Larynx C2-3 Image from: http://depts.washington.edu/pccm/Pediatric%20Airway%20management.ppt

10. Relatively larger tongue Obstructs airway Obligate nasal breathers Difficult to visualize larynx Straight laryngoscope blade completely elevates the epiglottis, preferred for pediatric laryngoscopy Angled vocal cords Infant’s vocal cords have more angled attachment to trachea, whereas adult vocal cords are more perpendicular Difficulty in nasal intubations where “blindly” placed ETT may easily lodge in anterior commissure rather than in trachea

11. Differently shaped epiglottis Adult epiglottis broader, axis parallel to trachea Infant epiglottis ohmega ( Ώ ) shaped and angled away from axis of trachea More difficult to lift an infant’s epiglottis with laryngoscope blade

12. Funneled shape larynx narrowest part of infant’s larynx is the undeveloped cricoid cartilage, whereas in the adult it is the glottis opening (vocal cord) Tight fitting ETT may cause edema and trouble upon extubation Uncuffed ETT preferred for patients < 8 years old Fully developed cricoid cartilage occurs at 10-12 years of age INFANT ADULT

13. Respiratory system Alveoli small & limited number Lung compliance decreased Cartilaginous rib cage Chest wall compliance increased Chest wall collapse during inspiration and relatively low residual volume Chest is circular shaped with horizontal ribs

14. Weaker intercostal muscle and the diaphragm Fewer type 1 muscle cells Abdominal muscle strength undeveloped Caliber of airways is relatively narrow Large rate of o2 consumption Ventilator drive are not well developed, so hypoxia and hypercapnia depress respiration

15. CVS In neonates Myocardium less contractile causing the ventricles to be less compliant & less able to generate tension during contraction – Limits the size of stroke volume – Cardiac output therefore rate dependant – Infant behaves as with fixed cardiac output state • Cardiac output – 300-400 ml/kg/min at birth – 200 ml/kg/min within few months

16. Vagal parasymphathetic tone is most dominant which makes neonates & infants more prone to bradycardias • Bradycardia : – Assc with reduced cardiac output – If assc with hypoxia, should be treated with O2 & Ventilation initially – Cardiac compression will be required in neonate with HR 60 or less OR 60-80bpm with adequate ventilatio

17. renal Decreased glomerular filtration rate Decreased creatinine clearance Decreased sodium excretion Decreased glucose excretion Decreased bicarbonate resorption Decreased diluting capability Decreased concentrating ability 600 mosm Meticulous attention to fluid administration

18. Dehydration: – Poorly tolerated – Premature infants have increased insensible losses as they have large surface area relative to weight – There is larger proportion of ECF in children (40% BW as compared to 20% in adult) • Conclusion: – Newborn kidneys has limited capacity to compensate for Volume EXCESS or Volume DEPLETION

19. Glucose management High glucose utilization Premies 5-6 mg/kg/minute Neonates 3-4 mg/kg/minute Low glycogen stores Predisposes to hypoglycemia Neonates < 30 mg/dl Infants < 40 mg/dl Increased risk with prematurity Options at maintenance rate D5LR, D5 ½ NS, D5 ¼ NS

20. Thermoregulation Greater heat loss Thin skin Low fat content High surface area/weight ratio No shivering until 1 yrs Thermogenesis by brown fat More prone to iatrogenic hypo/hyperthermia Optimal ambient temp to prevent heat loss: – Premature infant: 34⁰C – Neonates: 32⁰C – Adults: 28⁰C

21. Pharmacotherapy Weight “guesstimate” = 2 x (age) + 9 Total body water content increased (70-75%) Large volume of distribution for water soluble meds Increased dose/kg Hepatic biotransformation immature Protein binding decreased Neuromuscular junction immature Muscle mass in neonates smaller Termination of action by redistribution prolonged

22. Volatile anesthetics Minute ventilation to FRC ratio increased Blood flow to vessel rich groups increased. Rapid rise in alveolar anesthetic concentration Blood-gas coefficients lower in neonates Inhalation induction rapid BP of neonates and infants more sensitive to hemodynamic effects of volatile agents Caution against overdose

23. IV or IM anaesthetics 1- thiopentone sodium Lower dose in neonates than in infants Neonates- 3-4 mg/kg Infants - 5-6 mg/kg decreased dosage in neonates is due to -- immature brain -- decreased plasma protein binding -- more permeable BBB. increased requirement in infants due to increased cardiac output as this would be expected to reduce the first pass concentration of thiopentone arriving at the brain .

24. PROPOFOL Children required larger dose of propofol - Large vol of distribution Shorter elemination half life Higher plasma clearance 2- 3 mg / kg

25. Opioids More potent in neonates than children or adults Easier across blood:brain barrier Decreased metabolic capability Increased sensitivity of respiratory centers Caution in neonates Hepatic conjugation decreased Cytochrome P 450 pathways mature by 1 mo Renal clearance of morphine metabolites is decreased Children have high rates of hepatic blood flow Increased biotransformation and elimination

26. Neuromuscular blockers Shorter onset time (as much as 50%) Shorter circulation time Depolarizing agent Succinylcholine Nondepolarizing agents Rocuronium Cisatricurium Vecuronium

27. Fastest onset → 30-60 secs Children → 1-1.5 mg/kg IV, 4-6 mg/kg IM Infants → 2-3 mg/kg IV, 4-6 mg/kg IM Dysrhythmias Bradycardia and sinus arrest Atropine 10-20 mcg/kg Vecuronium - .1mg/kg

28. Rocuronium Drug of choice for intubation 0.6 mg/kg IV RSI 0.9-1.2 mg/kg IV May last 90 min May be given IM 1-1.5 mg /kg Onset 3-4 min Cisatricurium Consistently intermediate duration 0.05-0.06 mg/kg IV

29. Reversal Nondepolarizing blockade can be reversed with neostigmine (0.03–0.07 mg/kg) or edrophonium (0.5–1 mg/kg) along with an anticholinergic agent ( glycopyrrolate , 0.01 mg/kg, or atropine, 0.01– 0.02 mg/kg).

30. Preoperative considerations History and physical Comorbid illness Recent URI Murmur Innocent New Symptomatic Anesth problems Labs → none routine

31. URI Symptoms new or chronic? Infectious vs allergic or vasomotor Viral infection within 2 - 4 weeks of GA with intubation increases perioperative risk Wheezing risk increased 10x Laryngospasm risk increased 5x Hypoxemia, atelectisis , recovery room stay, admissions and ICU admissions all increased If possible, delay nonemergent surgeries

32. Premedication Sedative premedication is generally omitted for neonates and sick infants . NPO Clears → 2 h Breast milk → 4 h Formula → 6 h Solids → 8 h

33. Monitoring Age & size appropriate standard monitors Precordial stethoscope Heart rate, heart tones, respiratory quality Preductal pulse oximetry in neonates Right extremity or earlobe EtCO2 monitor Main-stream less accurate in < 10 kg Side-stream may falsely elevate iCO2 and falsely lower EtCO2. Temperature

34. M onitoring

35. Induction Inhalation Sevoflurane Halothane Intravenous Propofol Thiopental Ketamine Intramuscular Ketamine

36. Airway management Mask LMA Intubation Neonate – 1 y 3 – 4 ETT Uncuffed ETT 4 + age/4 Cuffed 3 ½ + age/4 Depth 3 x tube size Blades Straight most common Miller Phillips Wis-Hipple Curved available Fiberoptic Bullard Glide

37. Face masks

38. Selection of laryngoscope blade: Miller vs. Macintosh Miller blade is preferred for infants and younger children Facilitates lifting of the epiglottis and exposing the glottic opening Care must be taken to avoid using the blade as a fulcrum with pressure on the teeth and gums Macintosh blades are generally used in older children Blade size dependent on body mass of the patient and the preference of the anesthesiologist

39. Endotracheal Tube New AHA Formulas: Uncuffed ETT: (age in years/4) + 4 Cuffed ETT: (age in years/4) +3 ETT depth (lip): ETT size x 3 Age Wt ETT(mm ID ) Length(cm ) Preterm 1 kg 2.5 6 1-2.5 kg 3.0 7-9 Neonate-6mo 3.0-3.5 10 6 mo-1 3.5-4.0 11 1-2 yrs 4.0-5.0 12

40. Cuff vs Uncuffed Endotracheal Tube uncuffed ETT recommended in children < 8 yrs old to avoid post- extubation stridor and subglottic stenosis Arguments against cuffed ETT: smaller size increases airway resistance, increase work of breathing, poorly designed for pediatric pts , need to keep cuff pressure < 25 cm H2O Arguments against uncuffed ETT: more tube changes for long-term intubation, leak of anesthetic agent into environment, require more fresh gas flow > 2L/min, higher risk for aspiration For “short” cases when ETT size >4.0, choice of cuff vs uncuffed probably does not matter Cuffed ETT preferable in cases of: high risk of aspiration ( ie . Bowel obstruction), low lung compliance ( ie . ARDS, pneumoperitoneum ) etc.

41. T piece vs closed circuit Jackson-Rees modification to Ayres T piece or Mapleson F circuit Simple, lightweight, has an open ended bag which can be occluded to apply CPAP and PEEP Better for children <20kg (varies with anaesthetist) because easier to assess tidal volume and lung compliance, has low resistance and dead space Disadvantage is pollution and anaesthetic gas wastage Bag must be big enough not to restrict tidal volume but not so large that his visual and tactile monitor is lost Breathing

42. Paediatric breathing circuit Narrow tubing (15mm) which reduces compression volume and small distal connections to minimise dead space Better conservation of heat and vapour, easy scavenging and less gas wastage but loss of feel during hand ventilation due to large compression volume

43. Perioperative fluid replacement 1 st 0-10 kg → 4 cc/kg/ hr 2 nd 10-20 kg → 2 cc/kg/ hr > 20 kg → 1 cc/kg/ hr Calculate preoperative deficit Replace 50% first hour Replace 25% second hour Replace 25% third hour Minor surgery → additional 2 cc/kg/ hr Major surgery → up to additional 10 cc/kg/ hr

44. Estimated allowable blood loss Blood volume Premies → 95 ml/kg Term neonates → 90 ml/kg Up to 1 year → 80 ml/kg > 1 year old → 70 ml/kg EABL → wt kg x est blood vol x (starting Hct -allowable Hct ) / ave Hct

45. Blood product replacement Age appropriate Hct Premies and sick neonates Hct 40-50% Nadir at 3-6 months of 30% Comorbid conditions Replace initially with 3 x BSS or 1 x colloid Usual starting dose of PRBC is 10 cc/kg EBL ~ 1.5 blood volumes give FFP/platelets FFP 10 cc/kg Platelets 1 unit/10 kg raises platelets by 50K Cryo 1 U/10 kg

46. Regional Anaesthesia Most commonly done caudal, SAB and penile block caudal block- Penil and anal surgery Vaginal surgery Orchidoplexy Hernia repair

47. Bupivacain plain 1- 1.5 mg/kg Lidocain 2-2.5 mg /kg Doses: 0.5cc/kg for perineal surgery 0.75cc/kg for T-10 level 1cc/kg for lower thoracic level

48. Penile block- Done for any penile surgery

49. CONCLUSION Pediatric anesthesia involves more than simply adjusting drug doses and equipment for smaller patients. Neonates, infants, toddlers, and young children have differing anesthetic requirements. Safe anesthetic management depends on full appreciation of the physiological, anatomic, and pharmacological characteristics of each group. Indeed infants are at much greater risk of anesthetic morbidity and mortality than older children ; that require unique surgical and anesthetic strategies.

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