1. Dr. S. Parthasarathy MD. DA. DNB., Dip.diab. MD(acu), DCA, Dip. Software-statistics. PhD (physio) Mahatma Gandhi medical college and research institute, puducherry – India Practical paediatric anaesthesia

2. Children are not mini adults

3. Definitions Neonates – a baby within 44 weeks of age from the date of conception Infants – a child of up to 12 months of age Child – 1 to 12 years Adolescent – 13 to 16 years

4. Physiology, Pharmacology and practical considerations oxygen consumption in infants may exceed 6ml/kg/min, twice that of adults physiological adaptations in paediatric cardiac and respiratory systems to meet this increased demand.

5. physiology The cardiac index (defined as the cardiac output related to the body surface area) is increased by 30-60 percent in neonates and infants to help meet the increased oxygen consumption. Neonates have a higher haemoglobin concentration (17 g/dl) and blood volume

6. Cardiovascular system Neonatal myocardium is stiff and increase in cardiac output is rate dependent Stroke volume ?? So tachycardia is important BUT The sympathetic nervous system is not well developed predisposing the neonatal heart to bradycardia. Sinus arrhythmia is common in children and all other irregular rhythms are abnormal

7. Some differences neonateInfantAbove 1Around 5Adult O2 consumtion 65543 Systolic BP 659095 120 Heart rate 130120 9075 Blood volume 8580 7570 Hb gm% 1711121314

8. Respiratory- airway The head is relatively large with a prominent occiput The neck is short. The tongue is large. The airway is prone to obstruction because of these differences

9. Infant airway Large head Prom.occiput Small neck

10. Infant airway Infants and neonates breathe mainly through their nasal airway, although their nostrils are small and easily obstructed. The larynx is higher in the neck (more cephalad), being at the level of C3 in a premature infant and C4 in a child compared to C5-6 in the adult.

11. Infant airway The epiglottis is large, floppy and U shaped. The trachea is short (approximately 4-9cm) directed downward and posterior and the right main bronchus is less angled than the left. Right main stem intubations are therefore more likely.

12. Infant airway The glottic opening (laryngeal opening) is more anterior and the narrowest part of the airway is at the cricoid ring. (In the adult airway the narrowest point is the vocal cords). At cricoid level, epithelium is loosely bound to the underlying areolar tissue. Trauma to the airway easily results in oedema.

13. narrowest

14. Epiglottis large floppy ET tube

15. Airway model

16. Respiratory system Ribs and cartilages are more pliable Chest wall collapse more with increased negative intrathoracic pressure Control of respiration poor Prolonged apnoea common after anaesthesia (caffeine 10 mg/kg) Hypoxia inhibits rather than stimulates breathing

17. Resp. system Respiration is mainly diaphragmatic (type 1 fibres 20%) Minute ventilation is more rate dependent The closing volume is larger than the FRC until 6-8 years of age RR = 24 – age/2 Spontaneous ventilation TV = 6-8 ml/kg; IPPV TV = 7-10ml/kg

18. Length and type length (Age / 2) + 12 1-2-3-----7,8,9 formula Size of the ETT (Age /3) + 3.5 or (Age /4) + 4.5 Below 8 years – uncuffed – allow leak at 30 cm water pressure

19. LMA sizes 1 LMA up to 5 kg; 1.5 LMA 5-10 kg; 2 LMA 10-20 kg; LMA 2.5 20 – 30 kg; LMA 3 for over 30 kg

20. Renal System Renal blood flow and glomerular filtration are low in the first 2 years of life due to high renal vascular resistance.. GFR 45 ml/min to adult values of 125 ml/min Tubular function is immature until 8months, so infants are unable to excrete a large sodium load. Dehydration poorly tolerated Urine output 1-2 ml/kg/hr

21. Renal a faster turnover of extracellular fluid Renal function – almost normal in adult levels -- age of 2 years 4-2-1 formula of IV fluids acceptable Options RL 1/2 NS 1/5 th NS

22. Hepatic System Liver function is initially immature Cytochrome P450 enzymes (phase I reactions) are fully developed, whereas others are approximately 50% of adult values. Phase II reactions, usually impaired in neonates Barbiturates, opioids – prolonged action Age of 1 year - ok

23. Temperature regulation Neonates and infants have a large surface area to volume ratio and therefore a greater area for heat loss, especially from the head increased metabolic rate but insufficient body fat for insulation and heat is lost more rapidly They don’t shiver Take all precautions to maintain temperature

24. Central Nervous System Neonates can appreciate pain The blood brain barrier is poorly formed The cerebral vessels in the preterm infant are thin walled, fragile Cerebral autoregulation is present

25. Psychology Less than 6 months – separation ok Children up to 4 years of age are upset by the separation Parental anxiety fear narcosis and pain

26. Pharmacologic principles Excess body water Suxa. Antibiotics Fat and muscle content ↓ ↓ Fat soluble drugs – Vd less- thio more dose a drug that redistributes into muscle may have a longer clinical effect (e.g., fentanyl,)

27. Pharmacologic principles immature hepatic and renal function, altered drug excretion caused by lower protein binding.

28. Anaesthetic agents smaller lung functional residual capacity per unit body weight and a greater tissue blood flow, especially to the vessel rich group (brain, heart, liver and kidney) Induction and recovery faster MAC of inhalational agents are greatest in the young and decrease with age

29. Nitrous oxide Odourless Ideal to supplement with agents Rapid turnover No change in paediatrics

30. Halothane ok Halothane has undoubtedly been wrongly incriminated in many patients for hepatic injury when a more detailed investigation would have cleared the anaesthetic from any blame.

31. Other agents Enflurane – pungent smell not much use Epileptiform activity Isoflurane – pungent smell but maintenance ok Desflurane - pungent smell- excellent rapid recovery

32. Sevoflurane Smooth and Rapid induction and recovery Non pungent Turn the vaporizer to 8% No coughing, spasm No use of adding N2O Ideal in patients with airway obstruction

33. Intravenous agents – more doses Thio 5-6 mg/kg Propofol induction and maintanance – Ok Pain on injection Anticholinergic + benzodiazipines + ketamine acceptable but hallucinations may occur in the recovery period

34. Muscle relaxants Neonates and infants require more suxamethonium for skeletal muscle paralysis, 2 mg/kg for infants Neonates and infants are more sensitive than adults to non-depolarising muscle relaxants. Initial doses are similar in both age groups because the increased extracellular fluid volume and volume of distribution in younger patients

35. Opioids,Bz,neostigmine Opioids morphine – safety ?? Remifentanyl ideal Diazepam: 0.1-0.3 mg/kg orally T1/2 80 hours  contraindicated < 6 months

36. Clonidine, midazolam – ok 0.1-0.15 mg/kg IM 0.5-0.75 mg/kg orally Midazolam – effect ?? The dose of neostigmine per kg required for antagonism of non-depolarising muscle relaxants is similar in children to adults

37. Regional anaesthesia Spinal cord ends at L2 L3 Lower projection of dural sac Delayed myelinization of nerve fibers Cartilaginous structure of bones and vertebrae Delayed development of curvatures of the spine Tuffier's line, L 5 and lower Increased fluidity of epidural fat and Loose attachment of sheaths

38. Remember in paediatrics Oxygenation IV fluids Temperature

39. Thank you all