ANAESTHETIC IMPLICATIONS IN PEDIATRIC PATIENTS

1. ANAESTHETIC IMPLICATIONS IN PEDIATRIC PATIENTS Dr Vishawjeet Singh Moderator Dr Jyoti Pathania

2. PREOPERATIVE PREPARATION • A– In addition to routine pre- anaesthetic evaluation, the following points should be stressed: • 1- gestational age at birth- extent of prematurity. • 2- congenital anomalies • 3- assessment of airway (cleft lip, micrognathia ) • 4- severity of coexistent disease-eg sepsis , resp. failure. • 5- degree of birth asphyxia, apneic spells.

3. B- CHILD--- • Psychological preparation is very important. • 1- Children over 2-6 years are over 5 times more likely to have significant preoperative anxiety. • 2- parental anxieties concerning the surgical procedures may be profound and can be transmitted to the child. • 3- anaesthesiologist should formulate the plan for smooth induction, explain the possibilities regarding induction and help soothe the family members. • 4- chidren are principally worried about pain and separation from parents.

4. Presurgical prep. programmes such as brochures, videos or tour can be helpful. Reassurances to parent and children is helpful. • In hospitals with appropriate facilities, separation anxiety can be avoided by inviting a parent to accompany the child at induction of anaesthesia.

5. ANAESTHETIC ASSESSMENT • Previous illness and operation • H/o allergy • h/o apnoeic spells- more likely to develop apnoea following anaesthesia and should not be accepted for day care procedres until they are atleast 50 wks gestation. • WEIGHT- influence the selection of anaesthetic eqipments. • Upto 12 yrs wt= (age + 3) 5/2 or age x 2 +9 • h/o respiratory tract infections • URTI– H/O RTI within 4 wks of operation , or who have symtoms of URTI preoperatively are at increased risk of respiratory complications such as --- laryngospasm • bronchospasm • atelectasis • hypoxemia • it is usual to postpone elective srgery for 4-6 wks, which may not be always practical.

6. URTI- If decision is taken to proceed with the surgery endotracheal tube should be used to control the airways. • Postoperatively the pt needs supplemental oxygen and careful monitoring.

7. Examination • Head and neck– for • loose deciduous teeth • signs of potentially difficult • intubation • limited mouth opening • micrognathia • large tongue • noisey breathing • A precordial murmur , circulatory instability or cyanosis point to a CHD in neonate. • Preoperative cough, fever, malaise and audible chest signs suggests lower respiratory tract infections. Elective anaesthesia should be postponed for 4-6 wks.

8. INVESTIGATIONS • Neonates scheduled for elective minor surgery--- CBC • S. Glucose • Neonates with chronic illness and congenital defects– CBC, glucose, albumin, clotting profile, platelet count. • In a healthy child scheduled for minor surgery – no investigations needed. • Hb estimation– in pts of chronic diseases , hemoglobinopathies, anaemia. • Hb and cross matching- if significant blood loss anticipated. • Other investigations should be indicated only when clinically indicated.

9. PREOPERATIVE FASTING • milk clear fluids • <6mths 4 2 • 6-36mths 6 3 • >36 mths 8 3 • Preoperative fasting times for different types of liquid and solids clear breast cow/formula solid milk milk < 3 mths 2 4 4 6 > 3 mths 2 4 6 6

10. Infants and young children become dehydrated easily than adults. • Preoperative fasting is required to minimize residual gastric volume at induction of anaesthesia and reduce the risk of pulmonary aspiration of gastric contents. • Gastric emptying time with breast milk and cow milk is more and thus more chances of aspiration.

11. PREMEDICATION • No premedication is required for < 6 mths • The need for premedication should be individualized according to- • underlying medical condition • length of surgery • desired induction of anaesthesia • psychological make up of child and family.

12. Drugs for premedication • MIDAZOLAM- • Oral 0.5 - 0.75 mg/kg • Nasal 0.2 - 0.3 mg/kg • Rectal 0.4 – 0.5 mg/kg • Im 0.1 – 0.15 mg/kg • It takes 20 minutes for oral midazolam to be effectve. • KETAMINE— • IM 2 mg/kg- in highly uncooperative pts • Oral- 6 mg/kg • Nasal 3 mg/kg • ORAL TRANSMUCOSAL FENTANYL CITRATE • (OTFC) • 15 -20 mg/kg onset 20 – 30 min • duration 30 min • disadvantages nausea, vomiting, pruritis, occasional desaturation. • advantages decreases intra and post operatine analgesic requirements.

13. SUFENTANIL • Nasal 1.5 – 3 microgm/kg • Onset 10 min • Adv dec analgesic requireements • early discharge from hospital • Disadv burning sensation in the nose • dec in chest wall compliance • and oxygen saturation.

14. H2 BLOCKERS • To decrease the potential for aspiration of gastric contents. • ANTICHOLINERGICS glycopyrrolate 5mic/kg atropine 20 mic/ kg -- lessen incidence of bradycardia -- reduces incidence of hypotension during induction in neonates and infants -- prevent accumulation of secretions for pts wiyh URTI, and those given ketamine.

15. INDUCTION OF ANAESTHESIA • Choice of agent and technique must be based on the needs of the individual patient. • Method/ technique of induction is determined by • -- medical condition of the patient • -- surgical procedure • -- level of anxiety of the child • -- whether able to cooperate, communicate. • -- presence or absence of full stomach.

16. A- INHALATION INDUCTION • -Reduced requirement • -incd incidence of bradycardia, hypotension and cardiac arrest To attenuate this, HR maintained and preload optimized. • Iv atropine 0.02 mg/kg. • BSS or albumin 10-20ml/kg before induction • **Most dangerous time during inhalation induction as the child loses consciousness- depress the heart • So once anesthesia is induced, dec halothane or sevoflurane conc. till iv line is secured • Don’t proceed to deeper planes of anesthesia without iv line in place. • 2nd most dangerous point- immediately after tracheal intubation If vaporizer • not closed before laryngoscopy-overdose of inhaled anesthetics • DISCONTINUE ALL ANESTHETICS UNTIL LARYNGOSCOPY AND ET INTUBATION ACCOMPLISHED

17. TECHNIQUES • NEONATES AND INFANTS • holding the end of anaesthesia circuit in a cupped hand over the infants face, the other hand can adjust the conc of anaesthetic . • Allowing the neonate or infant to suck on a rubber nipple or on a finger generally prevents crying during induction. • As the infant loses consciousness, the anaesthesia mask is added to improve delivery and to decrease operating room pollution.

18. PEDIATRIC PATIENTS • 1- BLOW UP THE BALLON • 2- HYPNOTIC SUGGESTIONS • anesthesia mask- aeroplane pilots mask • smell of halothane- aviation fuel • The use of constant conversation and 0.25 – 0.5% increase in inspired concentration for 3 – 4 breaths. • If child holds breath, avoid assisted respiration as it can cause laryngospasm, coughing. • 3- FLAVOURED MASK • 4- SINGLE BREATH TECHNIQUES • Child is asked to take a full inspiration followed by a full expiration. Placement of mask at the end of expiration, another full inspiration held as long as possible and then normal breathing. • Prior to inductioin– circuit is filled with 55 halothane in 60% n2o. • Takes < 1 min for induction

19. HALOTHANE • Standard agent • Sweat, non pungent, allows smooth induction and maintenance. • early onset and recovery. • Lower MAC in neonates d/t • A- immaturity of CNS. • B- attenuation of pain response d/t high levels of plasma peptides. • Higher MAC in infants d/t increase in brain water content. • In view of profound cvs effects of halothane in infants an incremental technique of induction is employed.

20. Incremental technique- • Following the administration of 70% N2O in oxygen, halothane concentration is increased in 0.5% increments every 3-5 breaths. • Consciousness is usually lost after 1-2 min. this incremental technique may occasionally be associated with An exaggerated excitement phase.

21. ISOFLURANE • Less myocardial depressant • Preservation of heart rate • Greater reduction of CMRO2 • Noxious smell and thus greater incidence of airway related problems. • DESFLURANE • Unsuitable for inhalational induction as it has a pungent etheral odour.

22. SEVOFLURANE • DOC for inhalational induction in many centres becoz of its- - --minimal pungency • ---Relatively low BG solubility- rapid induction and recovery. • A combinatioin of N20 70% in oxygen is given initially to obtund the child. At this stage, 8% sevoflurane can be introduced without any reaction from the patient and unconsciousness will be produced after 4-6 breaths. In addition to increasing the speed of induction, the use of 8% sevoflurane results in less excitation than an incremental technique.

23. Disadvantages sevoflurane • relatively higher rate of metabolism • fluoride ion • compound A .

24. NITROUS OXIDE • Sweet smelling, non irritant, non inflammable. • Occasionally premature and sick neonates may not tolerate cvs effects of nitrous in which case air may be substituted as a carrier gas for oxygen. • Main contraindication is h/o air pockets within the body and the need for high inspired oxygen concentration.

25. INTRAVENOUS INDUCTION • Important when induction with mask is contraindicated- full stomach, reflux esophagitis • i/v access. • Cannulation of tiny pediatric patient can be difficult. • Use of EMLA crème. • All air bubbles should be removed from the i/v line since high incidence of patent foramen ovale increases the risk of paradoxical air embolism. • In emergency situations where iv access is impossible fluids can be effectively infused through an18 G needle inserted into the medullary sinusoids within the tibial bone. This intraosseous infusion can be used for all medications normally given iv with rapid result.

26. 1- THIOPENTONE SODIUM • Lower dose in neonates than in infants • Neonates- 4-5 mg/kg • Infants - 7-8 mg/kg • decreased dosage in neonates is due to • -- immature brain • -- decreased plasma protein binding • -- more permeable BBB. • INCREASED REQUIREMENT in infants d/t • increased cardiac output as this would be expected to reduce the first pass concentration of thiopentone arriving at the brain.

27. Propofol • Dose required is higher in children • < 2 yrs – 2.9 mg/kg • 6-12 yrs – 2.2 mg/kg • KETAMINE • AS an induction agent in neonates especially those with cyanotic heart disease.

28. RECTAL INDUCTION • Child falls asleep in parents arms • Methohexital- 10% 25- 30 mg / kg • Induction within 8-10 minutes. • THIOPENTONE • 30mg/kg • Ketamine 10 mg/kg • Midfazolam 1mg/kg max 20 mg

29. INTRAMUSCULAR INDUCTION • Adv- reliability • Disadv- painful • Methohexital – 10 mg/kg • Ketamine -- 1 – 10 mg/kg • Midazolam -- 0.1 mg/ kg

30. RAPID SEQUENCE INDUCTION WITH CRICOID PRESURE • In full stomach patients • Rapid desaturationmay occur in child because- oxygen consumption high • child may refuse preoxygenation • Atropine 0.02 mg/kg is given iv to prevent reflux induced/ sch induced bradycardia.

31. Prep. of intubating equipment and suction • Preoxygenation of lungs • Rapid induction using STP, propofol or ketamine • Application of cricoid pressure • Rapid onset of paralysis with sch, roc

32. MUSCLE RELAXANTS SUCCINYL CHOLINE • 1-- Highly water soluble, therefore increased dose requirement in paediatric patients. • 2 – effective when given intramuscular. • Infants – 5 mg/kg • children 4 mg/kg • onset 3-4 min • duration of relaxation 20 min • In an emergency situation scholine can be given intralingually. 2 mg/ kg in midline to avoid hematoma formation.

33. 3– Children are more susceptible than adults to cardiac arrhythmias, hyperkalemia, and malignant hyperthermia after Sch administration due to underlying unrecognized muscle dystrophy. So it should be best avoided for routine elective surgery in children. • 4– atropine should be given just prior to the first dose of scholine in all children including teenagers.

34. NON DEPOLARIZING MUSCLE RELAXANTS • Immaturity of neuromuscular junctiontends to increase senstivity. • Disproportionately large extracellular compartment results in dilution of drug. • Greater volume of distribution in neonates result inslower rate of excretion and prolongation of effect. • Drugs such as vecuronium which has hepatic metabolism has increased duration of effect. • Hoffman degradation of atracurium makes it useful but histamine release can be a problem.

35. MIVACURIUM • 0.2 – 0.3 mg/kg dose causes adequate relaxation within 2 minutes and thus is ideal for constant infusion. • ROCURONIUM • 0.6 mg/kg for routine induction • 0.9 – 1.2 mg/kg- rapid sequence induction but prolonged duration 60-90 min should be expected. • It offers the advantage that it could be given intramuscularly in deltoid. It produces intubating conditions in 3 – 4 minutes. • im- 1mg/kg infants • 1.8 mg/kg children > 1 yr

36. Because of the extreme variability in response, the doses of long acting muscle relaxants should be titrated carefully starting from half to third of the usual dose. • The effect of the incremental doses of ms relaxants should be monitored with a peripheral nerve stimulator.

37. ANTAGONISM OF MS RELAXANTS • IT is recommended in all neonates and infants even if they have recovered clinically becoz any increase in the work of breathing may cause fatigue and respiratory failure. Useful signs of reversal are the ability of infant to lift the legs and arms.

38. PEDIATRIC AIRWAY MANAGEMENT • INTUBATION • Following inhalational induction, N20 and vaporizers should be discontinued prior to intubation so that that the lungs contain high inspiratory concentration of oxygen to combat apnoea. • Correct head position • Application of the external pressure at the level of cricoid cartilage to push the larynx into view.

39. LARYNGOSCOPE BLADE • INFANTS- flat blades are more suitable as it flattens out the curvature of the epiglottis and can be used to lift it forward to expose the larynx. • > 1 yr– medium sized curved badeswith the tip placed in the vallecula. • Gentle insertion, avoid trapping the lips between teeth and blade . Not to lever on upper tooth.

40. Tube size • Uncuffed tubes < 8 yrs of age. • Decreased incidence of post intubation croup • Provide a leak tominimize the risk of accidental barotauma. Allow a leak when 20- 30 cm of water pressure is applied. • Size- < 6yrs – age/3 +3.5 • >6 yrs – age/4 + 4.5 • neonate 3 kg – 3 mmid • < 3kg – 2.5 mmid

41. Tube length • Length of the tube should be such that the tip of the tube lies in midtrachea while 2-3 cm protrudes from the mouth. • Length in cm = ID X 3 • > 2 yr = age/2 + 13 • Neonate = 10 cm • 1 yr = 12 cm

42. ANESTHESIA CIRCUITS FOR PEDIATRICS • A- dead space should be minimal • B- weight and size be suitable • C- no valves to cause undue obstruction • D- humidified gases be used • E- reservoir bag should be smaller to monitor respiratory movements. • F- facemask must fit well to contour of face. • G- work of breathing should be less while preventing rebreathing.

43. NON REBREATHING CIRCUITS • 1- provide minimal WOB becoz they have no valves to be opened up by patients respiratory efforts. • 2- rate of induction is rapid becoz • - volume of non rebreathing circuit is less • - no equilibrium with CO2 absorber is required • - anaesthetic gases are delivered immediately in the airway. • 3- as the volume of nonrebreathing circuit is small as compared to that of circle system,the compression and compliance volumes are significantly less. This improves the ability to observe respiratory efforts as reflected by movement of anaesthesia bag as well as the ability to estimate pulmonary compliance.

44. T – piece system • Original T- piece ( Ayres) system consists of light metal T tube with a main lumen of 1cm diameter and of smaller side tube at right angle to the main lumen through which anaesthetic gas mixture was introduced. A length of rubber tubing attached to open end of T piece act as reservoir for anaesthetic gases.

45. Jackson Rees modification • Attached open tailed bag to the reservoir tube in order to facilitate controlled ventilation. • ADV- simplicity • convenience • compact size • T Piece system rely on adequate FGF to eliminate CO2 • During spontaneous vent- FGF > 2 MV • Controlled vent FGF = MV

46. CIRCLE SYSTEM • Consists of – • afferent and efferent breathing tubes • Reservoir bag • Chemical absorber • One way flow d/t unidirectional valves • ADV- • Economical use of anaesthetic gases • Conservation of heat and humidity

47. Provided ventilation is controlled in neonates and either controlled or assisted in infants , a standard adult circle system fitted with low dead space connectors , a small bore tubing and a reduced capacity reservoir bag is suitable for maintenance of anaesthesia for pts of all ages.

48. MAINTENANCE OF ANAESTHESIA • The goals- • Provision for adequate anesthesia and operating conditions • Maintaining physiological hemostasis • Adequate fluid replacement • Infants are poor candidates for anaesthesia with spontaneous ventilation becoz of poor pulmonary mechanics and increased susceptibility to cardiovascular depressant effects of volatile anaesthetic agents. • Combination of tracheal intubation and balanced anaesthesia with full dose of muscle relaxants , controlled ventilation, minimum concentration of volatile anaesthetics and reduced dose of opioids is optimum.

49. MONITORING • Pulse – temporal/ radial artery easily accessible. • Precordial/ esophageal stethoscope auscu;ltation • ECG monitoring • Respiratory monitoring by visual movements of chest wall • Pulse oximetry • ETCo2 for assessment of ventilation and confirmation of ETT placement and early warning of MH. • Temperature monitoring • Urine output • Fluids • Glucose monitoring • NIBP monitoring • Invasive monitoring

50. POST OPERATIVE CARE • Attention to the airways • Provision of oxygen therapy • Monitoring of pulse, respiration and blood pressure • Completion of post anaesthetic recovery charts • Recovery nurses should be trained to detect early changes in respiration and circulation and should be able to initiate treatment while the anaesthesiologist is summoned. • Once the child is awake , one of the patients parent can come in the recovery.