What you need to know about pediatric anesthesia

Respiratory & anatomical features of neonates & infants

Neonates & infants have weaker intercoastal muscles & diaphragms with less efficient ventilation, more horizontal & pliable ribs, & protuberant abdomens. Their alveoli are completely mature by 8yrs & RR falls to adult values by adolescence.

The presence of increased airway resistance increases the work of breathing & predisposes the respiratory muscles to fatigue. Reduced lung compliance, & increased chest wall compliance both promote chest wall collapse during inspiration & a relatively low residual volume following expiration. Therefore, resulting FRC reduction limits O₂ reserves during periods of apnea & predisposes neonates & infants to atelectasis & hypoxemia.

Neonates & infants consume O₂ a rate of 6-8ml/kg/min, & have non-fully developed hypoxic & hypercapnic ventilatory drives. Hence, periods of hypoxia & hypercapnia may swiftly result in respiratory depression.

Neonates & infants have proportionately larger head & tongue, narrower nasal passages, longer epiglottis & a shorter trachea & neck. Below is the RR of neonates & young children.

Neonate: RR- 40breaths/min
12 months: RR- 30breaths/min
3 years: RR- 25breaths/min
12 years: RR- 20breaths/min

Cardiovascular features, Metabolism & Temperature regulation

Neonates & infants have a noncompliant left ventricle, & their cardiac output is highly dependent on HR. Their sympathetic nervous system & baroreceptor reflexes aren’t fully mature.

Their immature heart is more sensitive to depression by volatile anesthetics & to opioid-induced bradycardia. Below is the HR & BP of neonates & young children.

Neonate: HR- 140beats/min; BP- 65/40mmHg
12 months: HR- 120beats/min; BP- 95/65mmHg
3 years: HR- 100beats/min; BP- 100/70mmHg
12 years: HR- 80beats/min; BP- 110/60mmHg

Pediatric patients have a larger body surface area than weight, & a high metabolic rate. The metabolic parameters including O₂ consumption, CO₂ production, cardiac output, & alveolar ventilation are proportionate to surface area.

Heat loss in neonates is greater due to their greater surface area, thin skin, & low body fat. Neonates produce heat by brown fat metabolism & by shifting hepatic oxidative phosphorylation to a more thermogenic pathway.

Renal & Gastrointestinal function, Glucose homeostasis

Kidney function usually comes close to normal values by 6 months of age; however, it may be delayed until age 2.

Neonates have high risk of gastroesophageal reflux. Their immature liver metabolizes drugs less efficiently.

The relatively reduced glycogen stores in neonates predispose them to hypoglycemia.

Pharmacological differences

Neonates & infants have proportionately more total body water content of about 75%. Therefore, volume of distribution for many IV drugs like neuromuscular blockers is disproportionately greater in neonates, infants & young children, & the optimal dose is commonly greater than in older children & adults.

A disproportionately smaller fat & muscle mass in neonates prolongs the clinical duration of action of lipid-soluble drugs such as propofol & fentanyl. Neonates have a relatively decreased GFR, decreased hepatic blood flow, impaired renal tubular function, & immature hepatic enzyme systems.

Neonates also have a decreased drug binding to proteins, particularly for many antibiotics & local anesthetics.

This formula is used to estimate a patient’s weight based on age in early childhood: 50th percentile weight (kg)= (Age x 2) + 9

Below is an extensive list of pediatric drug dosages

First part

Acetaminophen: 40mg/kg rectal; 10-20mg/kg PO; 15mg/kg IV (age> 2y). The maximum dose per day should be 60mg/kg.

Adenosine: 0.1mg/kg rapid IV bolus; 0.2mg/kg repeat dose; 12mg is maximum dose.

Albuterol: 1.25-2.5mg in 2mL normal saline nebulized.

Alfentanil: 20-25mcg/kg IV anesthetic supplement; 1-3mcg/kg/min for maintenance infusion.

Aminophylline: 5-6mg/kg IV loading dose administered over 20min; 0.5-0.9mg/kg/h maintenance dose (therapeutic level is 10-20mg/mL).

Amiodarone: 5mg/kg IV loading dose; 5mg/kg repeat dose (slowly); 5-10mcg/kg/min infusion dose. Maximum dose should be 20mg/kg/day.

Amoxicillin: 50mg/kg PO

Ampicillin: 50mg/kg IV

Ampicillin/sulbactam: 25-50mg/kg IV

Atracurium: 0.5mg/kg IV

Atropine: 0.01-0.02mg/kg IV; 0.02mg/kg IM; 0.03-0.05mg/kg PO premedication dose; 0.1mg is minimum dose.

Bretylium: 5mg/kg IV loading dose

Caffeine: 10mg/kg IV

Calcium chloride: 5-20mg/kg IV (slowly)

Calcium gluconate: 15-100mg/kg IV (slowly)

Cefazolin: 25mg/kg IV

Cefotaxime: 25-50mg/kg IV

Cefotetan: 20-40mg/kg IV

Cefoxitin: 30-40mg/kg IV

Second part

Ceftazidime: 30-50mg/kg IV

Ceftriaxone: 25-50mg/kg IV

Cefuroxime: 25mg/kg IV

Chloral hydrate: 25-100mg/kg PO; 50mg/kg rectal

Cimetidine: 5-10mg/kg IV or PO

Cisatracurium: 0.15mg/kg IV

Clindamycin: 20mg/kg IV

Dantrolene: 2.5mg/kg IV initial dose; 10mg/kg is maximum dose.

Desmopressin: 0.2-0.4mcg/kg IV

Dexamethasone: 0.1-0.5mg/kg IV

Dextrose: 0.5-1g/kg IV D25W or D50W

Digoxin: 15-30mcg/kg IV in three divided doses over 24h.

Diltiazem: 0.25mg/kg IV over 2min

Diphenhydramine: 1mg/kg IV, IM, or PO

Dobutamine: 2-20mcg/kg/min IV infusion

Dolasetron: 0.35mg/kg IV

Dopamine: 2-20mcg/kg/min IV infusion

Third part

Droperidol: 50-75mcg/kg IV

Edrophonium: 0.5-1mg/kg IV depending on the degree of paralysis.

Ephedrine: 0.1-0.3mg/kg IV

Epinephrine: 10mcg/kg IV bolus; 100mcg/kg endotracheal dose; 0.05-1mcg/kg/min IV infusion.

Epinephrine, 2.25% racemic: 0.05mL/kg in 3mL saline nebulized.

Esmolol: 100-500mcg/kg IV bolus; 25-200mcg/kg/min IV infusion

Famotidine: 0.15mg/kg IV

Fentanyl: 1-2mcg/kg IV pain relief; 2mcg/kg intranasal pain relief; 10-15mcg/kg premedication (Actiq PO); 1-5mcg/kg IV anesthetic adjunct; 2-4mcg/kg/h maintenance infusion; 50-100mcg/kg IV main anesthetic.

Flumazenil: 0.01mg/kg IV

Fosphenytoin: 15-20mg/kg IV

Furosemide: 0.2-1mg/kg IV

Gentamicin: 2mg/kg IV

Glucagon: 0.5-1mg IV

Glucose: 0.5-1g/kg IV

Glycopyrrolate: 0.01mg/kg IV

Granisetron: 0.04mg/kg IV

Heparin: 100U/kg IV (not for cardiac surgery); 300-400U/kg IV (cardiac surgery dose).

Hydrocortisone: 1mg/kg IV

Fourth part

Hydromorphone: 15-20mcg/kg IV

Ibuprofen: 4-10mg/kg PO

Imipenem: 15-25mg/kg IV

Inamrinone: 1.5mg/kg IV loading dose; 5-10mcg/kg/min maintenance dose.

Insulin: 0.02-0.1U/kg/h IV infusion

Isoproterenol: 0.1-1mcg/kg/min IV infusion

Ketamine: 1-2mg/kg IV induction dose; 6-10mg/kg IM induction dose; 10mg/kg per rectum induction dose; 25-75mcg/kg/min maintenance infusion; 6-10mg/kg PO premedication dose; 0.5-1mg/kg IV sedation dose.

Ketorolac: 0.5-0.75mg/kg IV

Labetalol: 0.25mg/kg IV

Lidocaine: 1mg/kg loading; 20-50mcg/kg/min maintenance.

Magnesium sulphate: 20-50mg/kg IV (slowly); 2g is maximum single dose.

Mannitol: 0.25-1g/kg IV

Meperidine: 0.2-0.5mg/kg IV pain relief

Methohexital: 1-2mg/kg IV induction; 25-30mg/kg per rectum induction; 10mg/kg IM induction.

Methylprednisolone: 2-4mg/kg IV

Fifth part

Metoclopramide: 0.15mg/kg IV

Metronidazole: 7.5mg/kg IV

Midazolam; 0.5mg/kg PO premedication; 20mg is maximum dose; 0.1-0.15mg/kg IM sedation; 0.05mg/kg IV sedation.

Milrinone: 50-75mcg/kg IV loading; 0.375-0.75mcg/kg/min maintenance dose.

Morphine: 0.025-0.1mg/kg IV pain relief; 0.1mg/kg IM premedication.

Naloxone: 0.01mg/kg IV

Neostigmine: 0.04-0.07mg/kg IV depending on the degree of paralysis.

Nitroglycerin: 0.5-3mcg/kg/min IV

Nitroprusside: 0.5-4mcg/kg/min IV infusion

Norepinephrine: 0.05-2mcg/kg/min IV infusion

Ondansetron: 0.1mg/kg IV

Oxacillin: 50mg/kg IV

Pancuronium: 0.1mg/kg IV

Penicillin G: 50,000U/kg IV

pentobarbital: 1-2mg/kg IM premedication

Phenobarbital: 5-20mg/kg IV anticonvulsant dose

Phentolamine: 30mcg/kg IV

Phenylephrine: 1-10mcg/kg IV

Phenytoin: 5-20mg/kg IV (slowly)

Physostigmine: 0.01-0.03mg/kg IV

Prednisone: 1mg/kg PO

Sixth part

Procainamide: 15mg/kg IV loading dose

Propofol: 2-3mg/kg IV induction; 60-250mcg/kg/min maintenance infusion.

Propranolol: 10-25mcg/kg IV

Prostaglandin E1: 0.05-0.1mcg/kg/min IV infusion

Protamine: 1mg/100U heparin IV

Ranitidine: 0.25-1mg/kg IV

Remifentanil: 0.25-1mcg/kg IV bolus; 0.05-2mcg/kg/min IV infusion.

Rocuronium: 0.6-1.2mg/kg IV intubation

Sodium bicarbonate: 1mEq/kg IV

Succinylcholine: 1-2mg/kg IV intubation; 4mg/kg IM intubation.

Sufentanil: 2mcg/kg intranasal premedication; 0.5-1mcg/kg IV anesthetic adjunct; 0.5-2mcg/kg/h maintenance infusion; 10-15mcg/kg IV main anesthetic.

Thiopental: 5-6mg/kg IV induction; 3-4mg/kg IV induction (for neonates)

Trimethoprim/sulfamethoxazole: 4-5mg/kg IV

Vancomycin: 20mg/kg IV

Vecuronium: 0.1mg/kg IV

Verapamil: 0.1-0.3mg/kg IV

Inhalational anesthetics

Neonates, infants & young children have greater minute-ventilation to FRC ratio which increases alveolar anesthetic concentration, & speeds inhalation induction.

Sevoflurane produces the least cardiovascular & respiratory depression; hence it is the agent of choice for inhaled induction in pediatric patients.

Isoflurane is the preferred agent for the maintenance of anesthesia in pediatric patients following sevoflurane induction.

The respective MACs of sevoflurane in neonates, infants, & small children are 3.2, 3.2, & 2.5.

The respective MACs of isoflurane in neonates, infants, & small children are 1.6, 1.8-1.9, & 1.3-1.6.

Muscle relaxants

Due to the high risks of cardiac arrest & hyperkalemia, succinylcholine has been avoided for routine, elective paralysis for intubation in children & adolescents.

Indications for succinylcholine include rapid sequence induction with a full stomach & laryngospasm which doesn’t respond to PPV. Furthermore, 0.1mg minimum atropine IV should be injected before succinylcholine administration in children.

When rapid muscle relaxation is needed before IV cannulation (e.g. inhaled induction in children with full stomach), 4-6mg/kg succinylcholine IM with 0.02mg/kg atropine IM may be used.

0.6mg/kg IV rocuronium is the preferred relaxant for routine intubation in pediatric patients. This is because it has the fastest onset of nondepolarizing neuromuscular blocking agents. Larger doses (0.9-1.2mg/kg IV) may be used for rapid sequence induction; however, it has a prolonged duration of up to 90 min. 1.0-1.5mg/kg rocuronium IM may also be administered, but it has an action onset of 3-4min.

Young infants undergoing short procedures may receive atracurium or cisatracurium, because of their short-to-intermediate action duration.

Reversal of nondepolarizing blockade is possible with 0.03-0.07mg/kg neostigmine IV or 0.5-1mg/kg edrophonium IV. Either of these agents should be given alongside with 0.01mg/kg glycopyrrolate, or 0.01-0.02mg/kg atropine IV.

Preoperative considerations for pediatric anesthesia

Prepare both the child and parents using age-appropriate brochures, videos, terms & other activities to explain the process of surgery & anesthesia. This helps relief worry about pain & separation from parents;
Premedicate children having upper respiratory tract infection symptoms with anticholinergics or albuterol. In addition, avoid intubation (if possible), & provide humidified volatile gases. These are necessary to avoid perioperative complications including hypoxemia, atelectasis, wheezing & laryngospasm;
Consult with a pediatric cardiologist or echocardiography if a child has a symptomatic murmur;
Infants may be fed breast milk up to 4h before surgery, formula or liquids & a light meal may be given 6h before induction. Offer clear fluids 2h before induction;
Give 0.3-0.5mg/kg midazolam PO, 15mg maximum to children with uncontrollable separation anxiety. Alternatively, smaller doses of midazolam with 4-6mg/kg ketamine PO may be used on inpatients;
Uncooperative patients may also benefit from 0.1-0.15mg/kg midazolam IM, 10mg max, or 2-3mg/kg ketamine IM + 0.02mg/kg atropine IM; Alternatively, 0.5-1mg/kg midazolam rectal, 20mg max, or 25-30mg/kg of 10% methohexital rectal may also be given;
Administration of 1-2mcg/kg dexmedetomidine or midazolam intranasally may also be used on uncooperative children;
Administering atropine reduces the incidence of hypotension & prevents secretions during induction, especially in neonates & infants. Oral dose of atropine is 0.05mg/kg;
Ensure the following for monitoring: smaller electrocardiographic electrode pads; precordial or esophageal stethoscope; pulse oximeter and capnograph; temperature measurement; invasive monitors; urinary output & blood glucose measurement; ABG & electrolytes, hemoglobin as necessary. Blood glucose levels <30mg/dl, <40mg/dl, & <60mg/dl in neonates, infants, & children respectively, indicate hypoglycemia.

Induction of anesthesia for pediatric patients

Induction of general anesthesia is either by inhalational or IV agents. 5-10mg/kg ketamine IM is useful in uncooperative patients. EMLA cream may render IV cannulation less painful for patients undergoing induction; however, it must remain in contact with the skin for at least 30-60min to be effective.

In emergency situations, perform awake or sedated-awake intubation (with topical anesthetics) on neonates & infants when they’re severely ill, or presence of possible difficult airway.

IV agent for anesthesia induction

Intravenous agents used are 2-3mg/kg propofol, non-depolarizing muscle relaxants (rocuronium, cisatracurium, or atracurium) or succinylcholine. In addition, ensure to administer atropine before succinylcholine. Alternatively, ET intubation without muscle relaxants requires a combination of propofol, lidocaine, & opiate with or without inhalational agents.

Inhalational agent for anesthesia induction

Sevoflurane is the inhalational agent of choice in children. The child first breaths in an odorless mixture of 70% N₂0 & 30% O₂ using a PPV mask. Sevoflurane is then added to the gas mixture in 0.5% increments every few breaths. To speed up induction in cooperative patients, use a single breath induction technique with sevoflurane (7-8% in 60% N₂0).

Following induction with sevoflurane, IV line can be placed (if absent) & then propofol & opioids (or muscle relaxant) given. Using an oral airway also helps to displace oversized tongue in neonates & infants, & steady application of 10cm PEEP prevents laryngospasm.

Alternatively, placing an LMA or intubation can be done under deep sevoflurane anesthesia alone. However, because of the higher level of anesthesia needed, risk of cardiac depression or laryngospasm occurring without IV cannulation limits use oof this technique. Moreover, 4mg/kg succinylcholine IM, 150mg max and 0.02mg/kg atropine IM, 0.4mg max should be available if laryngospasm or bradycardia occurs before IV cannulation.

Intravenous cannulation

For IV access, a 24G needle-catheter is sufficient for IV fluids in neonates & infants. The saphenous vein at the ankle is a common location for cannulation. In emergency situations where IV cannulation isn’t possible, an 18G needle is inserted into the medullary sinusoids within the tibial bone. This is useful for intraosseous infusion of fluids & medications.

Guidance for tracheal intubation

Administer 100% O₂ prior to intubation;
Slightly elevate the shoulders of the infant on a towel and place the head on a doughnut-shaped pillow;
Use the Miller laryngoscope blade to aid intubation of the anterior larynx in neonates, infants, & young children;
Ensure passing the ET tube gently through the glottis in children younger than 5 to avoid impingement on the cricoid cartilage, & postoperative edema. The cricoid cartilage is the narrowest point of the airway in this group of children;
Use an actual size internal diameter-mm ET tube according to age: 4+Age/4= an estimate of ETT ID (premature & full-term neonates are exceptions to this formula);
Make sure an ET tube 0.5mm larger or smaller than predicted is readily available;
Following passage into the larynx, confirm correct tube size & appropriate cuff inflation with a gas leak test at 15-25cmH20 of pressure; small leak indicates appropriate tube size & cuff inflation; no leak indicates oversized tube & overinflated cuff; excessive leak indicates very small ET tube & prevents adequate ventilation;
Advance the tip of ET tube 1-2cm infant’s glottis to avoid endobronchial intubation. A formula to estimate ET tube length (in cm) is 12+age/2.

Airway equipment sizes in children

0-1mo premature infants: ET tube mm i.d (2.5-3); ET tube cm depth (6-9); laryngoscope blade (00); mask size (00); oral airway (000-00)

0-1mo neonate: ET tube mm i.d (3-3.5); ET tube cm depth (9-10); laryngoscope blade (0); mask size (0); oral airway (00); LMA (1)

1-12mo infant: ET tube mm i.d (3.5-4); ET tube cm depth (10-12); laryngoscope blade (1); mask size (0); oral airway (0 [40mm]); LMA (1)

1-3y toddler: ET tube mm i.d (4-4.5); ET tube cm depth (12-14); laryngoscope blade (1.5); mask size (1); oral airway (1 [50mm]); LMA (2)

3-8y small child: ET tube mm i.d (4.5-5.5); ET tube cm depth (14-16); laryngoscope blade (2); mask size (2); oral airway (2 [70mm]); LMA (2.5)

8-12y large child: ET tube mm i.d (5.5-6); ET tube cm depth (16-18); laryngoscope blade (3); mask size (3); oral airway (3 [80mm]); LMA (3)

Ventilation parameters & anesthesia maintenance for pediatric patients

For controlled ventilation in patients of all ages, PPV helps overcome breathing circuit resistance in a semiclosed circle system. Furthermore, the Mapleson D circuit or Bain system may be used on patients <10kg because of their low resistance & light weight.

Pressure controlled ventilation should be used on neonates, infants, & toddlers. For children <10kg, sufficient tidal volumes are reached with PIP of 15-18cmH20. Small tidal volumes can also be manually delivered with much ease with a 1-L breathing bag.

For larger children ≥10kg, volume-controlled ventilation with tidal volumes set at 6-8mL/kg may be used. To minimize dead space, pediatric breathing circuits are usually shorter, lighter, & stiffer. Use appropriately sized heat & moisture exchangers to minimize dead space.

Anesthesia may be maintained intraoperatively in pediatric patients using same agents as in adults. Isoflurane may also be used. One may administer 1-1.5mcg/kg fentanyl IV, or 0.5mcg/kg dexmedetomidine IV (given slowly with HR monitoring) 15-20 min before end of surgery. Their administration reduces the incidence of emergence delirium & agitation following surgery.

Perioperative maintenance fluid requirement

Maintenance fluid infusion is dependent on this formula: 4mL/kg/h for the first 10kg; 2mL/kg/h for the second 10kg &; 1mL/kg/h for each remaining kg.

A solution of D₅^1/2NS with 20mEq/L KCL provides sufficient dextrose & electrolytes at these maintenance infusion rates. However, D₅^1/4NS is preferable in neonates to avoid risk of Na overload.

Glucose infusion rates for children up to 8yrs of age & premature neonates are 6mg/kg/min & 6-8mg/kg/min. These rates are necessary to maintain normal blood glucose levels (40-125mg/dL), & should be adjusted based on blood glucose measurements particularly during longer surgeries.

Perioperative fluid deficit requirement

This accounts for any preoperative fluid deficits which must be replaced. They are administered in hourly maintenance requirements as in 50% in the first hour, & 25% in the 2^nd & 3^rd hours.

Example: Assuming a 3kg neonate hasn’t received an oral/IV fluid 4hrs before surgery, we have a fluid deficit of 48mL/h (3 x 4mL/kg/h x 4h). Hence, 36mL would be administered in the first hour (48/2+12) & 24mL in the 2^nd & 3^rd hours (48/4+12).

Replace preoperative fluid deficits with lactated ringers’ injection or 0.45% NaCl solution.

Perioperative replacement requirement

In pediatric patients, blood loss is replaced by either 1mL of 5% albumin/mL of blood loss, or packed RBCs. In premature & sick neonates, target hematocrit for transfusion is about 40%. 20-26% is generally well tolerated in healthy older children. Appropriate dosing of packed RBC is necessary to avoid hyperglycemia, hyperkalemia, & hypocalcemia.

Transfuse 10-15mL/kg of platelets & fresh frozen plasma when blood loss is more than 1-2 blood volumes. However, early transfusion should be initiated following traumatic blood loss as part of a massive transfusion protocol. The pediatric dose of cryoprecipitate is 1U/10kg.

The third-space loss is the loss of fluid into the interstitial space. An estimation of this loss is dependent on the extent of surgery. Therefore, a common guideline for fluid administration is 0-2mL/kg/h for atraumatic surgeries, & 6-10mL/kg/h for traumatic surgeries. Third-space loss is usually replaced by lactated Ringer’s injection.

Regional anesthesia & analgesia in Pediatric patients

Caudal block is useful in inguinal hernia, clubfoot, & hypospadias repair, circumcision, anal surgery, & other subumbilical procedures.

A pediatric caudal anesthesia requires a short-bevel 22G needle, & a glass syringe filled with saline. Following placement of the patient in a lateral position & skin preparation, advance the needle through the sacral hiatus. A pop sound is felt following penetration of the sacrococcygeal ligament. Reduce the needle angle of approach & then advance a few more mm cephalad to avoid piercing the dura sac or the anterior body of the sacrum. Aspirate needle to check for blood or CSF. Following a negative aspiration, slowly inject a test dose containing 2mL of local anesthetics with epinephrine (1:200,000).

Anesthetic agents for pediatric caudal anesthesia: 0.125%-0.25% bupivacaine (up to 2.5mg/kg); 0.2% ropivacaine (most common); local anesthetics + epinephrine; clonidine with or without local anesthetics; local anesthetics + 25mcg/kg morphine sulfate or 6mcg/kg hydromorphone (this combo would increase the risk of delayed postoperative respiratory depression). The dose of local anesthetic may range from 0.5mL/kg for a sacral block, to 1.25mL/kg for a midthoracic block depending on the level of blockade desired.

Inserting a 20G caudal catheter with continuous infusion of local anesthetic (e.g. 0.125% bupivacaine or 0.1% ropivacaine at 0.2-0.4mg/kg/h) or an opioid (e.g. 2mcg/mL fentanyl at 0.6mcg/kg/h) facilitates prolonged anesthesia & postoperative analgesia.

Spinal anesthesia is useful for infraumbilical procedures in neonates & infants. Axillary, supraclavicular, & infraclavicular blocks are useful in procedures related with upper extremity under ultrasound guidance. Interscalene block is recommended for upper shoulder procedures under ultrasound guidance.

A unilateral transabdominal plane (TAP) block provides analgesia after hernia repair. A bilateral TAP block offers postoperative analgesia following an abdominal surgery with a lower midline incision. A rectus sheath block provides analgesia following an abdominal surgery with midline incision in the upper abdomen.