Anesthesia For Inguinal Hernia Surgery in Ex-Premature Babies

1. Anesthesia For Inguinal Hernia Surgery in Ex-Premature Babies Balvindar Kaur, MB BS, FANZCA Royal Childrens Hospital Melbourne Robin G. Cox, MB BS, FRCA, FRCPC

2. Introduction • Premature babies- who are we dealing with? • Techniques of anesthesia • Regional vs GA? • The evidence • Discussion

3. LEARNING OBJECTIVES • Understanding the physiology of a premature neonate • General vs regional anaesthesia for inguinal hernia surgery • Interpretation of current evidence of `best anaesthetic technique’

4. Disclosure • No conflicts of interest to declare

5. Definitions • Premature baby: Less than 37 weeks gestation • Late preterm : 34-37 wks gestation • Very preterm: < 32 weeks gestation • Extremely preterm: < 25 weeks gestation • Viability for 50% survival is 24 weeks in the developed world

6. Inguinal Hernia • Common surgical problem • Incidence is 1: 3000 births, BW < 1000g • Early surgery prevents incarceration, bowel ischemia and gonadal infarction • Optimal timing of surgery varies on perinatal history, other illnesses, and maturity

7. Premature babies-no small matter • Higher risk of post op complications • Respiratory – incidence of apneas 18-37% • Apnea incidence depends on method used to identify apnea, surgery and general health of infant

8. The problems- respiratory • Risk of apnea inversely proportional to gestational age, is more common in post conceptual ages < 44-46 but has been reported in older infants. • It CANNOT be reliably predicted by post-op pneumography or previous history of apneas • All ex-premature infants should have post-op apnea monitoring

9. Pathogenesis of apneas • Multifactorial • Abnormality of central respiratory control and airway obstruction • Majority of apneas occur in the post op period (related to respiratory depressant effects of GA on respiratory drive) • Late (2-12 hour) apneas maybe related to respiratory depressant effect of high levels of endorphins

10. Caffiene • In infants with apnea, caffeine is believed to work by stimulating the central respiratory center, decreasing the carbon dioxide threshold and increasing the response to hypercapnea. • Caffeine may also increase skeletal muscle tone and decrease diaphragmatic fatigue, aiding respiratory effort • Wellborn and colleagues showed that 10mg/kg of caffeine reduced the incidence of apneas, BUT these infants are still at risk from effects of intubation and ventilation

11. Anesthesia goals • Satisfactory surgical conditions • Adequate anesthesia with minimal physiological disturbance • Rapid recovery to pre-anesthetic status

12. Spinal anesthesia • First described in the 80’s by Abajian and colleagues for former preterm infants undergoing inguinal herniotomy • ADVANTAGES: CV stability maintained, no supplemental anesthesia needed, safe and reliable technique, minimal physiological disturbance, avoids GA, quick return to feeding. • DISADVANTAGES: no reliable way of estimating sensory loss, short duration of action, still has a risk of causing apneas therefore monitoring required

13. Caudal anesthesia • Initially described in the turn of the last century by Fernand Cathelin and Jean-Anthanase Sicard • A popular block in pediatrics for infraumbilical surgery • Initial description of its use as a sole anesthetic for inguinal hernia surgery in infants in the 1980’s

14. Caudal anesthesia - risks? • Inadvertent dural puncture • Intravenous injection • Failure - conversion to GA

15. Caudal Anaesthesia • Simple to perform • Easy to identify landmarks • Low complication rate • Dose: 1 ml/kg of 0.25% solution or 0.5 ml/kg of 0.5% solution for 6-12 hours of post op analgesia

16. Caudal Block Landmarks

17. SUMMARY OF LANDMARK STUDIES

18. GAS STUDY (Lancet 2015) • Multi-center RCT comparing regional vs. GA for effects on neurodevelopmental outcome and apnea • To determine whether Spinal vs. GA results in equivalent neurodevelopmental outcomes • To describe the incidence of apnea in the post op period (12 hours) after spinal and GA for inguinal hernia repair in infants • Inclusion criteria: Any infant for unilateral/bilateral inguinal hernia repair +/- circumcision; Gestational age > 26 weeks, post conceptual age up to 60 weeks • Groups: GA (sevo) +/- caudal or ilioinguinal block vs. Spinal/Caudal/Spinal+ilioinguinal block/ Spinal+caudal • [ Spinal: 0.2ml/kg 0.5% bupivacaine, Caudal: 2.5mg/kg bupivacaine]

19. GAS STUDY FINDINGS • 363 awake regional anaesthesia • 359 general anaesthesia • 238 awake regional group; 298 general group analysed • No evidence that just less than 1 h of sevoflurane anaesthesia increases the risk of adverse neurodevelopmental outcome at 2 years of age compared with awake-regional anaesthesia. • Early apneas are slightly more common in GA group

20. Cochrane review- Jones et al • To determine if… regional anaesthesia reduces postoperative apnea, bradycardia, the use of assisted ventilation, and neurological impairment, in comparison to general anaesthesia, in preterm infants undergoing inguinal herniorrhaphy at a postmature age.

21. Cochrane review • No statistically significant difference in risk of respiratory events*, use of analgesics, or post op respiratory support in infants receiving spinal or GA • Spinal without sedation – reduces post op apnea by up to 47% (compared with GA) • In infants without preoperative apnea, there is low quality evidence that spinal rather than GA may reduce preoperative apnea by up to 66% * Apnea, bradycardia or desaturations

22. Cote CJ et al - Post op Apnea in former preterm infants after inguinal herniorrhaphy. A combined analysis. Anesthesiology 1995, 82 (809) • 255 patients, 8 studies (384 patients, 4 institutions) • Patients having regional anesthesia, caffeine or other procedures excluded • PCA and gestational age are independent risk factors for apnea • Anemia, and apnea at home are risk factors whilst SGA appears protective • Incidence of apnea did not fall under 1% until PCA 56 weeks for Gestational Age 32 weeks, or 35 weeks Gestational Age, PCA 54 weeks

23. Kramer et al - GA vs. spinal • 18 infants less than 51 weeks age randomized to GA (atropine, halothane,N2O) or spinal (hyperbaric tetracaine) • 12 hour monitoring of respiratory rate, chest wall impedance and oxygen saturations and analysis of short and long apneas • Although there were no differences in central apneas, the GA group demonstrated lower post op minimum sats and heart rates compared to their preop values and the spinal group.

24. Caudal anesthesia in 25 ex prem* infants undergoing inguinal herniotomies • N20/Air and EMLA used • 2/25 patients had post operative apnea episodes • 1/25 had a total spinal • 1/25 required a GA for a prolonged procedure

25. Results

26. Results

27. Analysis

28. The authors here hypothesized that the enhanced recovery characteristics of sevo would result in similar recovery profiles to spinal anesthesia • Instead sevoflurane unmasked abnormalities in respiration • Spinal anesthesia had a lower incidence of apnea however there was a higher failure rate • The authors concluded that post op monitoring is so sophisticated that it was not worth subjecting all patients to a stressful awake spinal • Therefore spinals are worthwhile but only in the hands of experienced operators, if we provide a less stressful experience with GA and have good post op monitoring, its a safe alternative

29. Data analyzed from 1984 • Weighs actual significance of post op apnea in the setting of newer anesthetic agents, developments in neonatal and peri-op care and monitoring • Awake regional anesthesia is superior - but requires expertise from anesthetist and surgeon • Post op apnea is rare with light GA using des or sevo combined with caudal

30. PANDA STUDY (Pediatric Anesthesia Neurodevelopmental Assessment) • A large scale multi-site ambi-directional trial • Sibling matched cohort study • Outcome- neurodevelopmental effects of GA during inguinal hernia surgery in children < 36 months age

31. Postoperative monitoring • All ex premature infants less than 44-46 weeks post conceptual ages must have overnight admissions and apnea monitoring • PCA 60 weeks or less require 12 hours of apnea monitoring post op • Guidelines vary based on center, and must be discussed by team on the day.

32. Take home messages... • There is no conclusive evidencethat regional (spinal or caudal) is superior to GA in ex prem infants undergoing inguinal herniorraphy. • Regional techniques have been shown to have a lower incidence of apnea (not zero), but any combination of sedatives with the technique puts them at an equivalent or higher risk of apneas compared to GAs • Success on a regional technique is operator dependent and caudal anesthesia offers the advantage of a higher success rate however larger studies are needed to prove this • Risk factors for apnea include a low gestational age, prior history of apnea, PCA less than 44 weeks, anemia, concurrent cardiorespiratory disease, NEC, sedatives and PAIN • High risk patients and PCA less than 50 to 60 weeks need monitoring • Caffeine has been shown to be beneficial, but evidence is inconclusive for its routine use

33. References 1. Steward DJ. Preterm infants are more prone to complications following minor surgery than are term infants. Anesthesiology 1982; 56:304–306. ***2. Cote ́ CJ, Zaslavsky A, Downees JJ, et al. Postoperative apnea in former preterm infants after inguinal herniorraphy. A combined analysis. Anesthesiology 1995; 82:809–822. 3. Liu LMP, Cote ́ CJ, Goudsouzian NG, et al. Life-threatening apnea in infants recovering from anesthesia. Anesthesiology 1983; 59:506–510. ***4. Welborn LG, Greenspun JC. Anesthesia and apnea. Perioperative considerations in the former preterm infant. Pediatr Clin North Am 1994; 41:181–198. 5. Malviya S. Swartz J, Lerman J. Are all preterm infants younger than 60 weeks postconceptual age at risk for postanesthetic apnea? Anesthesiology 1993; 82:809–822. ***6. Williams JM, Stoddart PA, Williams SAR, Wolf AR. Postoperative recovery after inguinal herniotomy in ex-premature infants: comparison between sevoflurane and spinal anaesthesia. Br J Anaesth 2001; 86:366–371.

34. References 7. Abajian JC, Mellish RWP, Browne AF, et al. Spinal anesthesia for surgery in the high-risk infant. Anesthesiology 1984; 63:359–362. 8. Tobias JD, Burd RS, Helikson MA. Apnea following spinal anaesthesia in two former pre-term infants. Can J Anaesth 1998; 45:985–989. 9. Cox RG, Goresky GV. Life-threatening apnoea following spinal anesthesia in former premature infants. Anesthesiology 1990; 73:345–347. ***10. Bouchut JC, Dubois R, Foussat C, et. al. Evaluation of caudal anaesthesia performed in conscious ex-premature infants for inguinal herniotomies. Paediatric Anaesthesia 2001; 11: 55-58 ***11. Gerber AC, Weiss M. Awake spinal or caudal anesthesia in preterms for herniotomies: what is the evidence based benefit compared with general anesthesia? Current Opinion in Anesthesiology 2003; 16: 315-320

35. References 12. Spear RM, Deshpande JK, Maxwell LG. Caudal anaesthesia in the awake high-risk infant. Anesthesiology 1988;69:407-9. 13. Gunter JB, Watcha MF, Forestner JE, et al. Caudal epidural anesthesia in conscious premature and high-risk infants. JPediatrSurg 1991; 26: 9-14. 14. Peutrell JM, Hughes DG. Epidural anaesthesia through caudal catheters for inguinal herniotomies in awake ex-premature babies. Anaesthesia 1993; 48: 124-31