(BQ) Part 2 book “Principles and practice of pediatric anesthesia” has contents: Anesthesia for plastic and reconstructive surgery, anesthesia for pediatric dentistry, anesthesia for ophthalmic procedures, anesthesia for pediatric neurosurgical procedures, anesthesia and pediatric liver diseases, … and other contents.
17 Chapter Anesthesia for Plastic and Reconstructive Surgery Neerja Bhardwaj INTRODUCTION The commonly performed plastic surgical procedures in children include repair for cleft lip and palate and reconstruction procedures for craniofacial anomalies, temporomandibular joint ankylosis, anomalies of the foot and hands and burns (see Chapter 20) Anesthesia considerations for these procedures require a thorough assessment of the existing anomaly and prevention and management of airway difficulties, blood loss, aspiration of blood and secretions, adverse respiratory events like bronchospasm, laryngospasm and respiratory obstruction In addition, these children may have associated congenital anomalies and medical illnesses which have an adverse impact on anesthesia management It therefore becomes very important that these children are thoroughly evaluated and optimized before surgery for a good outcome CLEFT LIP AND PALATE The condition is present since birth with difficulty in feeding and swallowing, nasal regurgitation, history of (H/O) repeated upper respiratory infection (URI), pulmonary aspiration, chest infection and hearing problems, delayed dentition or maloccluded teeth and nasal speech.1 A child with a cleft lip is unable to suck as negative pressure cannot be established; he is unable to make consonants like B, D, K, P, and T and has typical cleft palate voice and audiometrically detected hearing loss of 10 decibels is present due to inflammation of the orifice of Eustachian tubes consequent on pharyngeal Chap-17.indd 240 inflammation from regurgitated food During the antenatal period, mother may have history exposure to X-ray, intake of drugs like cortisone, diazepam and phenytoin, vitamin deficiency and viral infection like rubella in 1st trimester In these children, milestones are delayed and in 10% of cases associated congenital anomalies are present (Table 1) Preoperative Assessment The child should be assessed for: • Presence of other congenital anomalies • Eustachian tube dysfunction and chronic serous otitis with clear rhinorrhea • Anemia • URI may be difficult to control in preoperative period in children with cleft palate In these children, an effective dose of antibiotics can be given before surgery • Undernourishment and dehydration because of poor intake Table 1: Congenital anomalies commonly associated with cleft lip and palate Hypertelorism Vander Woude syndrome Congenital heart disease Down syndrome Hand and foot anomalies Pierre – Robin syndrome Hydrocephalus Klippel Feil syndrome Congenital blindness Treacher Collins syndrome Mental deficiency 4/13/2016 2:09:55 PM Chapter 17: Anesthesia for Plastic and Reconstructive Surgery Investigations • • • Routine—complete blood count and urine examination Chest X-ray if there is fever, running nose, purulent secretions and noisy chest Investigations dictated by associated congenital anomalies ANESTHESIA MANAGEMENT All children should be fasted according to ASA guidelines.2 Oral midazolam 0.5 mg/kg, 20–30 before induction can be used for parental separation provided difficult airway does not contraindicate its use Children are monitored during surgery with precordial stethoscope, ECG, pulse oximetry, end-tidal CO2 and end-tidal anesthetic agents, noninvasive blood pressure (NIBP), temperature and fluid balance and blood loss Children may be anesthetized with inhalational or intravenous routes utilizing oxygen, sevoflurane or halothane followed by securing of IV access or with thiopentone or propofol if IV access is available.1,3 Before administering a muscle relaxant, confirm effective mask ventilation and use a tooth guard/rolled gauze piece over the defect while performing laryngoscopy and intubation to avoid trauma to the lips and gums It also prevents the laryngoscope blade from falling into the cleft (Fig 1) Any non-depolarizing muscle relaxant can be used for intubation but atracurium in a dose of 0.5 mg/ kg is preferred Intubation may be difficult in presence of syndromes and bilateral cleft where succinylcholine Fig 1: Use of roll gauze to support the laryngoscope and prevent it from falling into the cleft Chap-17.indd 241 (1–1.5 mg/kg) may be administered After intubation with an appropriate RAE endotracheal tube, check bilateral air entry, introduce pack and protect eyes The surgeon introduces a mouth gag before performing cleft palate surgery and care should be taken to see that the endotracheal tube is not compressed when it is opened We use hypodermic needle cover to prevent tube compression (Fig 2) One should auscultate for the breath sounds and chest compliance during placement and manipulation of the mouth gag during manual ventilation Tube compression can be detected if there is an increase in airway pressures if patient is on a ventilator and by decreased bag compliance if manually ventilating Anesthesia can be maintained with oxygen, nitrous oxide and inhalational agent (desflurane, sevoflurane, isoflurane or halothane) and intermittent doses of non-depolarizing muscle relaxants Analgesia can be provided with morphine 0.1 mg/kg or fentanyl 1–2 µg/ kg Intermittent positive pressure ventilation (IPPV) decreases bleeding and also maintains tidal volume which may be compromised because of head down tilt During spontaneous ventilation the abdominal viscera presses upon the diaphragm and so increases work of breathing which is prevented by IPPV At the end of surgery, muscle relaxation is reversed by atropine/glycopyrrolate (0.025 mg/kg/0.01 mg/kg) and neostigmine (0.05 mg/kg) After suction of the throat under vision, remove pack and then remove endotracheal tube (ETT) after child is fully awake, responding to commands and has full muscle tone Child should be nursed in lateral or semiprone position to keep the airway unobstructed and allow blood Fig 2: Use of hypodermic needle cover to prevent endotracheal tube (ETT) compression by the mouth gag The ETT lies behind the tongue of the mouth gag 241 4/13/2016 2:09:56 PM Principles and Practice of Pediatric Anesthesia to trickle out After palate repair blood tends to gravitate towards hypopharynx and larynx Auscultate the chest for any aspiration Elbow sleeve should be applied to avoid the child touching the repaired area Postoperative pain management can be achieved by paracetamol,4 nonsteroidal anti-inflammatory drugs (NSAIDs),5 infiltration of cleft repair site with local anesthetic and additives like ketamine and dexmedetomidine;6-8 infraorbital nerve block9 and maxillary nerve block.10,11 The adverse events for which an anesthetist should be alert are summarized in Table Table 2: Perioperative problems with cleft lip and palate surgery Preoperative Intraoperative Postoperative • • • • • Difficult veins Difficult mask ventilation • • • • • 242 Chap-17.indd 242 Difficult intubation Accidental extubation during positioning Malposition of mouth gag in relation to ETT leading to partial or complete airway obstruction Obstruction due to pharyngeal pack – tube compression Arrhythmias when using halothane and adrenaline infiltration Blood loss Problems of hypothermia and hypoglycemia • • Airway obstruction due to pack left inadvertently, tongue and pharyngeal edema, tongue fall and bleeding Postoperative nausea and bleeding Pain CRANIOFACIAL SURGERY Craniosynostosis is a condition where there is premature fusion of one or more cranial sutures (Fig 3) leading to a failure of normal bone growth perpendicular to the suture and a compensatory growth at other suture sites resulting in a characteristic abnormal head shape Most syndromic craniosynostoses show autosomal dominant inheritance, although the majority is attributed to new mutations from unaffected parents Mutations in genes coding for fibroblast growth factor receptors (FGFRs) are responsible for the most common syndromes.12 The condition may be isolated (80%) or occurring in association with many syndromic conditions (20%) Both of them can lead to raised intracranial pressure (ICP) due to hydrocephalus, airway obstruction or abnormalities in the venous drainage of the brain.12 Raised ICP presents with visual difficulties, nausea and vomiting, somnolence or headaches and “sun-downing” appearance In children with Apert’s and Crouzon’s syndromes, maxillary hypoplasia leads to narrowing of the nasal cavity and nasopharynx Glossoptosis may cause obstruction of the hypopharynx in children with mandibular hypoplasia.13 The common syndromes which can cause craniosynostosis are shown in Figure The various surgical procedures which can be performed for craniosynostosis are shown in Table Table 3: Types of surgical procedures for craniosynostosis Surgery for sagittal synostosis Frontal orbital advancement and remodeling a Extended strip craniectomies b Spring-assisted cranioplasty c Total calvarial remodeling Posterior expansion and remodeling Midface advancement (Le Fort III and monobloc procedures) Fig 3: Normal cranial bones and sutures in a neonate 4/13/2016 2:09:56 PM Chapter 17: Anesthesia for Plastic and Reconstructive Surgery Apert’s syndrome Pierre Robin syndrome Treacher Collins syndrome Goldenhar syndrome Crouzon’s syndrome Fig 4: Various craniofacial syndromes Chap-17.indd 243 243 4/13/2016 2:09:57 PM Principles and Practice of Pediatric Anesthesia PREOPERATIVE ASSESSMENT During the preoperative visit rapport and trust is established with the patient and family to reduce anxiety Parents should be told about the possibility of intraoperative blood loss and possible need for mechanical ventilation postoperatively The child should be evaluated for pre-existing medical conditions (congenital heart disease), medication history, allergies, family history of problems with anesthetics, problems with previous anesthetics and a physical examination Children with major congenital craniofacial abnormalities may present with upper airway obstruction because of involvement of the cranium, midface and mandible (Table 4) A history of abnormal sleep patterns like noisy snoring, restless sleep and frequent arousals during sleep, sleep apnea and daytime somnolence identifies patients who are likely to develop airway obstruction during sedation and induction of anesthesia Children should be assessed for signs of raised ICP Many syndromic craniosynostosis may produce difficulty in intubation and therefore should have a thorough airway assessment Oral and nasal cavities should be examined if fiberoptic intubation (FOB) is planned The mobility of the cervical spine should be evaluated if Goldenhar’s syndrome is suspected In Apert’s syndrome, there is midface hypoplasia and proptosis which can make face mask ventilation difficult Because of small nares and a degree of choanal stenosis there may be high resistance to airflow through the nasal route and so these patients are obligate mouth breathers Thus, face mask ventilation with a closed mouth can lead to obstruction which can be relieved by simple airway adjuncts such as an oropharyngeal airway (OPA) or nasopharyngeal airway (NPA) and continuous positive airway pressure (CPAP) Children with Apert’s syndrome also have fused cervical vertebrae Children who have undergone frontofacial advancement may have difficulty in intubation as a result of the altered relationship between the maxilla and mandible and reduced temporomandibular joint movement Children may show signs of upper respiratory infection presenting as wheeze Almost 50% of patients with Apert, Crouzon, or Pfeiffer syndromes develop obstructive sleep apnea (OSA).14 The obstruction may be due to midface Table 4: Common syndromes associated with craniosynostosis 244 Involving the cranium and midface Involving the mandible Involving the midface and mandible Crouzon syndrome Apert’s syndrome Pfeiffer syndrome Nager and Stickler syndrome Robin sequence Treacher Collins syndrome Hemifacial microsomia Chap-17.indd 244 hypoplasia, causing a distortion in the nasopharyngeal anatomy Chronic upper airway obstruction may lead to an increase in ICP and a subsequent decrease in cerebral perfusion pressure (CPP) A negative effect on neurological and cognitive development occurs because of recurrent episodes of intermittent reduction in CPP.15 Investigations These should include a preoperative hematocrit (Hct), platelet count, coagulation studies, serum electrolytes and urea and creatinine along with routine CBC and urine X-ray chest for assessment of lung fields and heart size and radiograph of the cervical spine to rule out fusion/ atlantoaxial dislocation of spine are essential Blood is grouped and cross-matched and appropriate volume of fresh packed blood and blood products like fresh frozen plasma, platelets, fibrinogen is kept ready.15 ANESTHESIA MANAGEMENT Young infants not require any premedication but older children may be administered oral midazolam 0.5 mg/kg half an hour before induction of anesthesia to alleviate separation or situational anxiety A child with history of OSA or difficult intubation should not be premedicated In this group of patients, an intravenous line may be secured after application of topical anesthetic cream hour before the expected time of induction If FOB is planned the child should be administered atropine or glycopyrrolate for drying of the oral secretions Inhalational (sevoflurane preferred because of its rapid uptake and removal) or intravenous induction can be used followed by endotracheal intubation with or without the use of nondepolarizing muscle relaxants Inhalational induction is preferred because of risk of difficult ventilation in syndromic children and difficulty in securing IV access Various techniques of intubation have been described in the literature depending on the difficulty in securing the airway.16-18 These may range from rigid laryngoscopy to FOB via oral or nasal route.19 Since awake intubation may not be feasible in children because of lack of cooperation LMA guided FOB may be an alternative technique.20,21 Other intubation techniques like retrograde intubation and use of bougies in children have also been described in literature.22,23 A preformed oral (RAE) tube or an armored tube is preferred for intubation which should be fixed securely (using a suture or wired to the tooth) to avoid the possibility of dislodgement during manipulation of head during craniotomy A balanced neurosurgical technique using opioids and inhalational agents and controlled ventilation is 4/13/2016 2:09:57 PM Chapter 17: Anesthesia for Plastic and Reconstructive Surgery the anesthetic technique of choice to avoid increase in ICP Isoflurane is the anesthetic of choice for maintenance of anesthesia since it causes the least rise in ICP Various authors have utilized remifentanil as well as a combination of sevoflurane and remifentanil for surgical repair of craniosynostosis with good results.12 Nitrous oxide should be avoided because of the risk of venous air embolism (VEA) Intraoperative Problems The intraoperative body temperature should be maintained at 35°–37°C by warming all IV fluids, wrapping the non-exposed body parts in plastic sheets, using forced air warming device or warm-water heating pad and using heated humidifiers or HME devices in airway circuit to minimize evaporative heat loss from respiratory tree Additional protective padding should be used at pressure points to avoid nerve injury The child has a larger body surface area-to-volume ratio compared with the adult (head comprises nearly 18% of the surface area vs 9% in adults) This results in proportionally greater fluid and heat losses in a child The fluid loss may vary from 6–8 mL/kg (extradural procedure) to 10–12 mL/ kg (intradural procedure) Fluid is administered to provide maintenance requirements, replace third space losses and to replace a portion of the blood loss The fluid requirement and therapy can be monitored by central venous pressure (CVP) and urine output The surgical procedure may carry a risk of air embolism when venous structures are exposed to the atmosphere, causing the subatmospheric intravascular pressure to entrain air Mass spectroscopy of end-tidal gases (elevation of end-tidal nitrogen concentration and a sudden decrease in PetCO2) is the most sensitive indicator of this entrainment Precordial Doppler is recommended for monitoring of air embolism However in small children, the technique is cumbersome and offers little benefit Pediatric craniofacial surgery commonly requires blood transfusion therapy because extensive scalp dissection and calvarial and facial osteotomies result in significant blood loss In infants and children, the estimated blood volume ranges between 75–80 mL/kg Therefore, intraoperative blood transfusion is inevitable in craniosynostosis repair and depends on type of suture repaired and the type of surgical procedure performed Measures to reduce blood loss and use of alternative techniques for blood conservation can be utilized.24 temperature and urine output Invasive arterial pressure monitoring is essential because of potential for massive blood loss Adequate venous access is essential and requires two large bore IV cannulae Central venous pressure monitoring is desirable in those cases where excessive blood loss is anticipated Intraoperative assessment of coagulation parameters may be sometimes required where massive blood transfusion has occurred Routine use of precordial Doppler for early diagnosis of venous air embolism is essential TEMPOROMANDIBULAR JOINT ANKYLOSIS The causes of temporomandibular joint (TMJ) ankylosis in children may be congenital or acquired due to trauma Anesthesia management is challenging in children because of their restricted mouth opening with near total trismus, and the need for general anesthesia before making any attempts to secure the airway (Fig 5) PRESENTATION The child usually presents with inability to open mouth and protrude his jaw with oral intake limited to only fluids with passage of time If the condition is congenital it may be associated with hypoplasia of the mandible.25 The main issues are related to the various methods to secure the airway for the surgical repair.26-28 FOB guided intubation is the best, but other methods like blind nasal intubation, use of track light, retrograde intubation and tracheostomy Monitoring Routine monitoring includes ECG, oxygen saturation (SpO2), end-tidal carbon dioxide (ETCO2), core Chap-17.indd 245 Fig 5: Temporomandibular joint ankylosis 245 4/13/2016 2:09:57 PM Principles and Practice of Pediatric Anesthesia can also be utilized Rest of the anesthesia management is based on the basic principles of pediatric anesthesia OTHER PLASTIC SURGICAL PROCEDURES Surgical procedures on the hand and foot are required for syndactyly, burn contracture and club foot Children may also present with ear deformities, arteriovenous malformation and hemangioma which require surgery The anesthetic management of these surgical procedures may include general anesthesia which is administered via supraglottic airway devices (LMA, PLMA, I-gel and Air Q) or endotracheal tube General anesthesia can be combined with ultrasound guided upper limb nerve blocks or caudal block depending upon surgical procedure for perioperative pain relief CONCLUSION Anesthesia for children undergoing plastic surgery procedures can be challenging for an anesthesiologist It involves focus on airway assessment and management of difficult airway; assessment of blood loss and replacement and intensive perioperative and postoperative monitoring for a favorable outcome REFERENCES 246 Chap-17.indd 246 Deshpande J, Kelly K, Baker MB Anesthesia for pediatric plastic surgery In: Motoyama EK, Davis PJ (Eds) Smith’s Anesthesia for Infants and Children 7th edn Philadelphia: Mosby Elsevier; 2006.p.723-36 Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures Anesthesiology 2011;114:495-511 Schindler E, Martini M, Messing-Junger M Anesthesia for plastic and craniofacial surgery In: Gregory GA, Andropoulos DB (Eds) Gregory’s Pediatric Anesthesia 5th edn Singapore: Wiley-Blackwell; 2012 p.810-44 Bremerich DH, Neidhart G, Heimann K, et al Prophylactically administered rectal acetaminophen does not reduce postoperative opioids in infants and small children undergoing elective cleft palate repair Anesth Analg 2001;92:907-12 Sylaidis P, O’ Neill TJ Diclofenac analgesia following cleft palate surgery Cleft Palate Craniofac J 1998;35:544-5 Coban YK, Sinoglu N, Oksuz H Effects of preoperative local ropivacaine infiltration on postoperative pain scores in infants and small children undergoing elective cleft palate repair J Craniofac Surg 2008;19: 1221-24 Jha AK, Bhardwaj N, Yaddanapudi S, Sharma RK, Mahajan JK A randomized study of surgical site infiltration with bupivacaine or ketamine for pain relief in children following cleft palate repair PediatrAnesth 2013;23:401-6 Obayah GM, Refaie A, Aboushanab O, et al Addition of dexmedetomidine to bupivacaine for greater palatine nerve block prolongs postoperative analgesia after cleft palate repair Eur J Anaesthesiol 2010;27:280-4 Bosenberg AT, Kimble FW Infraorbital nerve block in neonates for cleft lip repair: anatomical study and clinical application Brit J Anaesth 1995;74:506-8 10 Mesnil M, Dadure C, Captier G A new approach for peri-operative analgesia of cleft palate repair in infants: the bilateral suprazygomatic maxillary nerve block Pediatr Anesth 2010; 20:343-9 11 Jonnavithula N, Durga P, Madduri V Efficacy of palatal block for analgesia following palatoplasty in children with cleft palate Pediatr Anesth 2010;20:727-33 12 Thomas K, Hughes C, Johnson D, Das S Anesthesia for surgery related to craniosynostosis: a review Part Pediatr Anesth 2012;22: 1033-41 13 Boston M, Rutter MJ Current airway management in craniofacial anomalies Curr Opin Otolaryngol Head Neck Surg 2003;11:428-32 14 Nargozian C The airway in patients with craniofacial abnormalities PediatrAnesth 2004;14:53-9 15 Koh JL, Gries H Perioperative management of pediatric patients with craniosynostosis Anesthesiology Clin 2007;25:465-81 16 Sims C, von Ungern-Sternberg BS The normal and the challenging pediatric airway Pediatric Anesthesia 2012;22:521-26 17 Frawley G, Fuenzalida D, Donath S, Yaplito-Lee J, Peters H A retrospective audit of anesthetic techniques and complications in children with mucopolysaccharidoses Pediatric Anesthesia 2012;22:737-44 18 Hosking J, Zoanetti D, Carlyle A, Anderson P, Costi D Anesthesia for Treacher Collins syndrome: a review of airway management in 240 pediatric cases Pediatric Anesthesia 2012;22:752-8 19 Holm-Knudsen R The difficult pediatric airway—a review of new devices for indirect laryngoscopy in children younger than two years of age Pediatric Anesthesia 2011;21:98-103 20 Selim M, Mowafi H, Al-Ghamdi A, et al Intubation via LMA in pediatric patients with difficult airways Can J Anaesth 1999;46:891-3 21 Monclus E, Garce´s A, Arte´s D, et al Oral to nasal tube exchange under fibroscopic view: a new technique for nasal intubation in a predicted difficult airway Pediatr Anesth 2008;18:663-6 22 Przybylo HJ, Stevenson GW, Vicari FA, Horn B, Hall SC Retrograde fibreoptic intubation in a child with Nager’s syndrome Can J Anaesth. 1996;43:697-9 23 Hasani R, Shetty A, Shinde S Retrograde intubation: a rare case of goldenhar syndrome posted for posterior fossa surgery in the sitting position J Neurosurg Anesthesiol 2013;25:428 24 Hughes C, Thomas K, Johnson D, Das S Anesthesia for surgery related to craniosynostosis: a review Part Pediatric Anesthesia 2013;23: 22-7 25 Aiello G, Metcalf I Anaesthetic implications of temporomandibular joint disease Can J Anaesth 1992;39:610-16 26 Arora S, Rattan V, Bala I Adult fiberoptic bronchoscope-assisted intubation in children with temporomandibular joint ankylosis Paediatr Anaesth 2009;19:914-5 27 Arora MK, Karamchandani K, Trikha A Use of a gum elastic bougie to facilitate blind nasotracheal intubation in children: a series of three cases Anaesthesia 2006;61:291-4 28 Vas L, Sawant P A review of anaesthetic technique in 15 paediatric patients with temporomandibular joint ankylosis Paediatr Anaesth 2001;11:237-44 4/13/2016 2:09:57 PM 18 Chapter Anesthesia for Pediatric Dentistry Sarita Fernandes, Deepa Suvarna INTRODUCTION PEDIATRIC DENTAL PROCEDURES American Academy of Pediatric Dentistry (AAPD) defines pediatric dentistry as an age defined specialty that provides both primary and comprehensive preventive and therapeutic oral health care for infants, and children through their adolescence, including those with special medical needs.1 The anesthesia requirements in pediatric dental patients may lie anywhere along the spectrum of monitored anesthesia care (MAC) to sedation or general anesthesia Complications like obstructive airway, hypoventilation, apnea, laryngospasm, and cardiopulmonary changes are known to occur and hence it should be standard practice to have a separate sedation provider.2 The challenges faced by the anesthesiologist are rare syndromes, a shared airway with the dental surgeon, and working outside the comfort zone of the operation theater with untrained assistants who may not be competent enough to help in the event of some catastrophe It is likely to be the first anesthesia experience for the child and his parents, hence we should put in our best efforts to make it pleasant and safe • • • • • Operative restorations, including amalgam and composite resin Stainless steel crowns Pulpal treatments Extractions Orthognathic plates for cleft palate patients THE DENTAL CHAIR Pediatric dental chairs are usually smaller than convent ional dental chairs, hence may be incapable of accommodating larger children (Fig 1) Many CLINICAL PRESENTATION Pedodontists treat a large base of healthy children They may also deal with other patients such as :3 • Disabled children and adolescents • Psychologically challenged children • Medically compromised children • Children with orofacial trauma • Children requiring orthodontic care Chap-18.indd 247 Fig 1: Pedodontia suite 4/13/2016 2:09:22 PM Principles and Practice of Pediatric Anesthesia pedodontists thus use conventional dental chairs along with wooden or papoose board Dental chair must be capable of head-down tilt even in the event of power failure When the patient is placed supine pooled saliva or blood can trickle behind and induce coughing Upright position in the dental chair predisposes to postural hypotension, there is a risk of cerebral hypoxia consequent to unrecognized fainting The most common position used is semisupine, where the airway is maintained along with distinct cardiovascular and respiratory advantage.4 LOCAL ANESTHETICS Regional and local blocks are usually stand-alone techniques or combined with procedural sedation or general anesthesia (GA) in children Most procedures are done under infiltrative anesthesia Maxillary and mandibular nerve blocks are given for extensive work Reduced bone density of the maxilla and mandible in children may lead to rapid diffusion and absorption of local anesthetic hence toxicity occurs at doses well below the toxic level in adults To minimize sensation of needle prick, topical lignocaine gel/spray can be applied on the dried mucosa and left in place for at least one minute to achieve effect In patients allergic to bisulfates local anesthetic without a vasoconstrictor agent is preferred (Table 1) Table 1: Doses of local anesthetics5 Maximum dose (mg/ kg) with epinephrine Approximate duration (minutes) Lidocaine 5.0 7.0 Bupivacaine 2.0 3.0 Levobupivacaine 2.0 3.0 180–600 Ropivacaine 2.0 3.0 180–600 7.0 60–230 Articaine With local anesthetics, genuine anaphylactic reactions are rare Allergic reactions have been caused by coincidental exposure to antigens such as preservatives (e.g methyl-phydroxybenzoate), antioxidants (e.g bisulfate), antiseptics (e.g chlorhexidine), and other antigens such as latex, as well as local anesthetic drugs.6 Allergy tests used are skin tests (patch test and/or prick test and/or intradermal reaction) and/or challenge tests In event of drug allergy in a patient, skin tests should be carried out to weeks after the reaction Skin prick-tests and intradermal tests are done with dilutions of commercially available drugs Control tests using saline (negative control) and codeine (positive control) must accompany skin tests Skin tests are read in 15–20 minutes.6 Prick test is viewed positive, if diameter of the wheal is at least equal to half of the positive control test and at least mm greater than the negative control Intradermal tests are considered positive, when the diameter of the wheal is twice or more the diameter of the injection wheal (Table 2) PROCEDURAL SEDATION Children are fearful and uncooperative during dental procedure The pedodontist however is able to negotiate with behavior management techniques in most of them Those children where this is not possible, sedation may help avoid the need for general anesthesia (Table 3) Table 2: Concentrations of local anesthetic agents for skin tests Maximum dose (mg/ kg) without epinephrine Local Anesthetic LOCAL ANESTHETIC ALLERGY Available agents Prick-tests Intradermal tests mg.mL-1 Dilution mg.mL-1 Dilution µg.mL-1 90–200 Max conc and/or dilution 180–600 Bupivacaine 2.5 Undiluted 2.5 1/10 250 Lidocaine 10 Undiluted 10 1/10 1000 Ropivacaine Undiluted 1/10 200 Table 3: Sedation continuum 248 Minimal sedation anxiolysis Moderate sedation/Analgesia (“Conscious sedation”) Deep sedation/ Analgesia General anesthesia Responsiveness Normal response to verbal stimulation Purposeful response to verbal or tactile stimulation Purposeful response following repeated or painful stimulation Unarousable even with painful stimulus Airway Unaffected No intervention required Intervention may be required Intervention often required Spontaneous ventilation Unaffected Adequate May be inadequate Frequently inadequate Cardiovascular function Unaffected Usually maintained Usually maintained May be impaired Chap-18.indd 248 4/13/2016 2:09:22 PM Chapter 18: Anesthesia for Pediatric Dentistry Only patients categorized into ASA class and II are acceptable as candidates for conscious sedation Even children below 2–3 years can be treated on day care basis Generally patients of ASA III and IV are better managed in a hospital setting The equipment and monitoring is similar to the operating room Standard ASA monitors are mandatory Appropriate sizes of oral and nasal airways, laryngoscope with blades, endotracheal tubes, laryngeal mask airways (LMAs), difficult airway cart and suction should be available Sedation Techniques7 Sedative drugs may be administered by oral, submucosal, intramuscular, rectal, inhalational or intravenous routes Inhalational sedation is preferred by pedodontists because of reliability in terms of onset and recovery Fasting guidelines need to be followed for sedation procedures Nitrous Oxide Sedation Nitrous oxide/oxygen sedation is useful in children who are years and older for mild-to-moderate anxiety It is used in children with a strong gag reflex, as well as with muscle tone disorders, such as cerebral palsy, in order to avoid unintentional movements.8 Contraindications include uncooperativeness, claustrophobia, maxillofacial deformities that prevent nasal hood placement (Fig 2), nasal obstruction, deviated nasal septum, etc.8 oxygen analyzer With this type of minimal sedation, the child is able to maintain communication throughout the procedure.8 The delivery tubes are usually secured behind the chair, nasal hood is fixed and the child is asked to breathe through the nose with his mouth closed At induction the breathing bag is filled with 100% oxygen and delivered to the patient at 4–6 liters per minute for 2–3 minutes Once the appropriate flow rate is reached, nitrous oxide is introduced slowly at increments of 10 to 20% to achieve the desired level Local anesthetic is injected when the eyes take on a distant gaze with sagging eyelids Then the concentration can be reduced to 30% N2O and 70% O2 or lower Recovery is achieved quickly by reverse titration and the patient is allowed to breathe 100% oxygen for 3–5 minutes Child is instructed to remain in the sitting position for a brief period to ensure against dizziness on standing The incidence of diffusion hypoxia is minimal after the use of nitrous oxide and oxygen alone as opposed to nitrous oxide supplementation to parenteral or oral sedatives.9 Significant upper airway obstruction has been reported in children with enlarged tonsils given oral midazolam 0.5 mg/kg and 50% nitrous oxide.10 There is an increase in incidence of nausea and vomiting with concentrations in excess of 50%, during lengthy procedures, with rapid fluctuations in concentrations and rapid induction and reversal Nitrous oxide may depress laryngeal reflex significantly.11 SEDATIVE DRUGS COMMONLY USED Technique Midazolam According to the American Academy of Pediatrics Guidelines, nitrous oxide delivery equipment should have the capacity of delivering 100% oxygen concentration It is to be used in conjunction with a calibrated and functional Oral midazolam helps in calming children and does not increase gastric pH or residual volume (Table 4).12 Disadvantages of this route are delayed onset of action, variable absorption in the gastrointestinal tract and bitter Fig 2: Nasal hood for nitrous oxide sedation Chap-18.indd 249 249 4/13/2016 2:09:22 PM ... enters along 25 3 4/13 /20 16 2: 09 :23 PM Principles and Practice of Pediatric Anesthesia the mandibular periosteum at the operative site N20 should be discontinued on detection of emphysema and respiratory... possibility of need for postoperative ventilation .26 Fig 2: Difference between flexible LMA and classic LMA in ophthalmic surgery Chap-19.indd 26 1 26 1 4/13 /20 16 2: 08:54 PM Principles and Practice of Pediatric. .. 20 12; 28(3): 322 -5 22 Sinha R, Chandralekha null, Ray BR Evaluation of air-QTM intubating laryngeal airway as a conduit for tracheal intubation in infants—a pilot study Paediatr Anaesth 20 12; 22( 2):156-60