6. Infantile hypertrophy pyloric stenosis.pptx

Anesthesia for pediatric patients

1. Infantile hypertrophy pyloric stenosis Girmay T.Fitiwi April, 2018 1

2. THE STOMACH 1 . Functional components Three functional parts of the stomach Cardia Fundus and body Antrum 2

3. Pyloric stenosis O ccurs due to the hypertrophy of the gastric outlet musculature. The most common surgical disorder producing emesis in infancy/in the first three months of life. An acute medical emergency not a surgical emergency. Preoperative correction of the severe fluid and electrolyte deficits may require several days. 3

4. Incidence It occurs in approximately 2-4/1000 live births with an increased incidence in first born males. Males to females(4:1). 4

5. Etiology : The definitive Etiology remains unknown. Various theories proposed are: Polygenic mode inheritance Hypoganglionosis H.pylori infection Hypergastrinaemia with pylorospasm 5

6. Pathophysiology : Hypertrophy of the two muscle layers of the pylorus. The pyloric canal lengthens, the whole pylorus thickens, and The mucosa becomes oedematous causing functional obstruction of the gastric outlet. 6

7. Obstruction usually develops by 2-4 weeks of age. Emesis is usually projectile because of the high pressure generated by hypertrophied gastric muscles.  Wide range of metabolic disturbance Hypochloremic, Hypokalemic, Hypovolemic and Hyponatraemic Metabolic alkalosis. Hypocalcaemia may be associated 7

8. Why Hypochloremic metabolic alkalosis Normally each mEq of gastric acid secreted causes a mEq of HCO3- to be generated. HCl - lost via vomitus . HCO3 - continues to rise in the plasma. kidney ride out HCO3 - ( The load is high in the proximal convoluted tubule …..NaHco3- lost with urine ). Urine PH >7.0 / A lkaline urine. 8

9. Hypovolemia D ue to ECF depletion …..kidney attempts to conserve Na + by stimulating aldostrone. ECF depletion followed by Na+ …. Hyponatraemia . Hypokalemia K + is lost in the vomitus. H + -K + exchange ( excretion of K + )in the urine Hypokalemia . Intracellular shift 9

10. Pathophysiology Vomiting → loss of H ⁺ and Cl⁻ → Hypochloremic hypokalemic metabolic alkalosis. Protracted vomiting → ECF volume deficit → urinary excretion of K⁺ and H⁺ to preserve Na⁺ and water. Initial alkalotic urine becomes acidotic- Paradoxical aciduria. Hypochloremic hypokalemic metabolic alkalosis with paradoxical aciduria with secondary respiratory acidosis. Hyponatremia may not be evident because of hypovolemia

11. Clinical Presentation 3-5 week old infant with non-bilious projectile vomiting immediately after feeding . An olive-like mass can be felt at the lateral edge of the rectus abdominis muscle in the right upper quadrant of the abdomen. Signs of dehydration Signs of malnutrition and poor weight gain may also be apparent. Pre-renal failure can occur. Jaundice occurs = glucuronyl transferase deficiency 2 to starvation (17%). 11

12. Ultrasound The size of the pylorus is measured and compared to standard values. Pyloric muscle thickness > 4mm. pyloric muscle length > 14 – 20mm. pyloric diameter >10-14mm is diagnostic in term infants, with both a high sensitivity (90-99%) and high specificity (97-100%). 12

13. Upper GI Imaging Barium studies show classical signs of an elongated pyloric canal (‘string sign’) or thickened pyloric mucosa (‘double-track sign’). 13

14. Barium swallow Duodenal bulb Air filled fundus Barium filled antrum Narrowed pyloric channel String sign Normal stomach

15. MANAGEMENT Resuscitation Initial management should follow an ‘ABC’ approach, and fluid management should focus on correction of underlying dehydration, as well as electrolyte and acid-base abnormalities. An initial bolus of 20ml / kg 0.9% saline should be used if the infant is dehydrated. Maintenance fluid : maintain adequate hydration whilst protecting against hypernatraemia and hypoglycaemia. 15

16. Maintenance fluid 5 % glucose / 0.9 % saline or 0.45% saline should be used in this situation. Serial electrolyte, acid-base and blood glucose measurements must be performed. KCL should be added to the fluid as required once urine output has been established. 10-40 meq /L KCL added once urine output established. An accurate fluid balance chart should be kept and urinary catheterization . 16

17. Aims Check for signs of good hydration (alertness, skin turgor, fontanelles, vital signs).  Aim for /Targets for resuscitation pH = 7.3-7.5 Na > 132 mmol/L Cl > 106 mmol/L K >3.2 mmol/L and HCO3 < 28- 30 mmol/L.  17

18. Anaesthesia The nasogastric tube should be aspirated before induction of anaesthesia to minimise the risk of pulmonary aspiration of gastric contents. A “4 quadrant aspiration” (turning the infant through a full rotation and aspirating the stomach at each quarter turn) has been suggested as being effective. 18

19. Management Anaesthesia may be induced by inhalation with sevoflurane (or halothane), or rapid sequence induction with either thiopentone or propofol. 1-2mg/kg of Suxamethonium. A modified RSI with gentle positive pressure ventilation is commonly used. Anaesthesia should be maintained with volatile agents 19

20. Intra op fluid management Boluses of an isotonic fluid (saline 0.9% or hartmann’s solution) 10ml/kg may be given intraoperatively to correct circulating volume if required. Glucose containing maintenance solutions may be continued in theatre, but must NOT be used for bolus fluid replacement. If glucose containing maintenance fluids are discontinued intra-operatively, the blood glucose should be checked regularly to ensure normoglycaemia throughout the perioperative period. 20

21. Post op Postoperative pain is not usually severe. intra-operatively with an IV opioid such as fentanyl 1 mcg/kg and paracetamol ( 30-40mg/kg PR). The wound should be infiltrated with bupivacaine 0.25% 2 mg/kg (0.8 ml/kg) where possible. Caudal Analgesia????Dose ???? Haemodynamic status. 21

22. Postoperative Care  Respiratory depression post op period and up to 7 hours after anaesthesia in full term infants. This may be related to a delayed correction of CNS alkalosis affecting the pH of the CSF. Oral feeds are usually initiated 6-8 hours after surgery. The typical time in hospital to return to full feeds is usually 2-3 days. Thus maintain iv infusion of fluids until oral intake is adequate. 22

23. SUMMARY A common condition, occurring in 2 – 4 / 1000 live births Presentation is usually early, between 3 – 5 weeks of age. Initial management is aimed at resuscitation, correcting of dehydration, alkalosis and electrolyte disturbances before corrective surgery can occur . A variety of anaesthetic techniques have been used successfully, although rapid sequence intravenous induction, endotracheal intubation and maintenance with an inhalational agent is common and safe. 23

24. Anaesthetic management Technique : GA with controlled ventilation with endotracheal intubation Goals : normoxia, Normocapnia, Normothermia Normovolemia and Electrolyte balance Avoid bradycardia, aspiration of gastric contents