pediatric anesthesia

Abdulaziz Hisham Al Abdulaziz Hisham Al GainGain

Presented May 2003

Development:

Organogenesis - 1st 8 weeks

Organ function - 2nd trimester

Body mass - 3rd trimester

Changes in cardiovascular system:

Removal of placenta from circulation

Increasing of systemic vascular resistance Decreasing of pulmonary vascular resistance

True closure of PDA ~ 2-3 weeks critical transitional circulation Myocardial cell mass less developed prone to biventricular failure, volume loading, poor tolerance to afterload, heart rate-dependent CO** True for young infants

Changes in pulmonary system:

Small airway diameter - increased resistance

Little support from the ribs

VO2 2x > adults

Diaphragm and intercostal muscles do not achieve type-1 adult muscle fibers until age 2

Obligate nasal breathers

Airway difference:

Large tongue

Higher located larynx

Epiglottis short and stubby, angled over the inlet

Angled vocal cords we must rotate ETT to correct lodging at anterior comissure

Narrowest portion is cricoid cartilage

Chest wall/Respiratory difference:

Ribs are horizontal in neonates (vertical in adults) Ribs and cartilages are more pliable Chest wall collapse more with increased negative intrathoracic pressure Atelectasis is more common

FRC number of alveoli

Alveolar ventilation/FRC: Adults = 1.5:1 Infants = 5:1 ( respiratory rate)

Kidney and liver difference:

Low renal perfusion pressure, immature GF, TF, obligate Na loser in the 1st month of life

Complete maturation @ 2 years of age

Impaired liver enzymes, including conjugation react.

Lower levels of albumen and proteins - prone to neonatal coagulopathy, and less drug bound higher drug levels

GI system and thermoregulation:

Full coordination of swallowing ~ 4-5 months increased risk for GE reflux

Large body surface area/weight

Limited ability to cope stress

Minimal ability to shiver in 1st 3 months

Heat whole body including the head

Pharmacology/dynamics:

Increased total body water:

Large initial dose required

Less fat longer clinical drugs effect

Redistribution of the drug into muscle will increase duration of clinical effect (fentanyl)

Consider liver and kidney immaturity

Volatile anestheticsIsoflurane:

Less myocardial depression than Halothane Preservation of heart rate CMRO2 reduction rate

Desflurane: Increased incidence of coughing, laryngospasm, secretions Concern of hypertension and tachycardia from sympathetic activation

Volatile anesthetics (2)

Sevoflurane Less pungent than Isoflurane

Concern of compound A (nephrotoxicity)

Most suitable for induction

Remember: MAC for potent volatile anesthetics is increased in

neonates, but may be lower for sicker neonates and premies

Induction drugs:Methohexital: 1-2 mg/kg i.v. or 25-30 mg/kg per rectum Side effects:

burninghiccupapneaextrapyramidal syndrome

Contraindication: temporal lobe epilepsy

Thiopental: 5-6 mg/kg i.v. Caution in low fat children and malnourished

Induction drugs:Propofol: 3 mg/kg i.v. (until 6 years of age) Pain on injection - 0.2 mg/kg Lidocaine i.v.

Ketamine: 10 mg/kg IM, PR, orally Increased salivation Contraindications: Increased ICP

Open globe injury

Induction drugs:Benzodiazepines: Diazepam: 0.1-0.3 mg/kg orally T1/2 80 hours contraindicated < 6 months Midazolam: Only FDA benzodiazepine approved in neonates 0.1-0.15 mg/kg IM 0.5-0.75 mg/kg orally 0.75-1.0 mg/kg rectally Reduce dose in drugs cause Cytochrome P- 450 inhibition

Induction drugs:Narcotics:

Morphine: Increased permeability of blood/brain barrier 50 mcg/kg IV

Meperidine: Less respiratory depression than morphine Be cautious in long term administration because of its metabolite normeperidine

Induction drugs:Narcotics(2):

Fentanyl: 12.5 mcg/kg IV during induction provides stable cardiovascular response 1-2 mcg/kg adjuvant to anesthesia Stable cardiovascular response Alfentanyl and Sufentanyl: More rapid clearance than adults Can cause parasympatholysis bradycardia, hypotension

Induction drugs:

Muscle relaxants:

Succinylcholine: 2.0 mg/kg IV; 4.0 mg/kg IM Consider Atropine 10-15 mcg/kg given prior SUX Potential side effects:

RhabdomyolysisHyperkalemiaMasseter spasmMH

Induction drugs:

Muscle relaxants(2):

If tachycardia desired - Pancuronium

Mivacurium - brief surgeries, beware of histamine release, bronchospasm

Rocuronium - useful for modified RSI, and can be administered IM (1 mg/kg)

MAINTENANCE DOSE (ED95)(mg/ kg) DURING ANESTHESIA

WITHN2O/O2 HALOTHANE

SUGGESTED DOSE (mg/ kg) FORTRACHEAL INTUBATION

(2 × ED95)

Muscle relaxanta

d-Tubocurarine 0.60 0.30 0.80Pancuronium 0.08 0.06 0.10–0.15Metocurine 0.34 0.15 0.50–0.60Atracurium 0.30 0.20 0.50–0.60Cisatracurium 0.10 0.080 0.10Vecuronium 0.08 0.06 0.10–0.15Mivacurium 0.10 0.10 0.20–0.25Doxacurium 0.030 0.030 0.050–0.060Pipecuronium 0.080 0.080 0.080–0.120Reversal agentsb

Edrophonium(0.3–1.0 mg/ kg) +atropine (0.01–0.02mg/ kg)

Neostigmine(0.02–0.06 mg/ kg)+ atropine (0.01–0.02 mg/kg)

Muscle relaxants - Summary:

Premedication:

Almost all sedatives are effective Usually not necessary < 6 months Most common route used is oral Side effects:

Oral - slow onsetIM - pain, sterile abscessRectal - uncomfortable, defecation, burnNasal -irritatingSublingual -bad taste

Pharmacological premedication options

1.Role when awake separation of child from parent before induction is planned.

2.Its success may be judged by the peacefulness of the separation.

3.Large volume of literature indicates lack of clearly ideal technique

http://metrohealthanesthesia.com/edu/ped/pedspreop6.htm

Pharmacological premedication options

Midazolam (Versed)

• PO: 0.5 to 1.0 mg/kg up to 10 mg max.

• Bioavailability = 30% • Peak serum levels after about 45

minutes • Peak sedation by about 30

minutes • 85% peaceful separation• Mix with grape concentrate or

acetaminophen (Tylenol) syrup or elixir or Motrin Suspension (10 mg/kg of the 2% suspension)

Pharmacological premedication options (3)

Midazolam (Versed)(2)

• Nasal: 0.2 to 0.6 mg/kg• Peak serum level in 10 minutes • 0.2 mg/kg same as 0.6 mg/kg

except • 0.2 mg/kg did not delay

recovery • 0.6 mg/kg may delay extubation

• Possible concern: animal studies reveal neurotoxicity after topical applicaton.


Midazolam (Versed)(3)

• Sublingual: 0.2-0.3 mg/kg as effective as 0.2 mg/kg intranasal

• Rectal: 0.35 to 1.0 mg/kg • Some effect by 10 minutes, peak

effect 20-30 minutes. • 1.0 mg/kg did not delay PACU

discharge.


Methohexital (Brevital)

• Rectal 25 to 30 mg/kg as 10% solution in warm tap water

• 85% sleeping within 10 minutes = rectal induction of GA (very peaceful separation)

• Sleep duration: about 45 to 90 minutes

• 25 mg/kg did not delay recovery in one study, but some delay may be expected after a short (less than 30-minute) case.


Ketamine

• PO: 6 to 10 mg/kg • May slightly prolong time to

discharge after a short case• IM: 3 to 4 mg/kg sedation; • 2 mg/kg did not delay recovery • 6 to 10 mg/kg = IM induction of

general anesthesia • 10 mg/kg: as effective as

Midazolam 1 mg/kg but some delay in recovery may be expected


Midazolam + Ketamine:

• PO 0.4 mg/kg + 4 mg/kg respectively

• 100% successful separation

• 85% easy mask induction

• Doubling dose leads to "oral induction of general anesthesia" in most cases. Lasts 30 to 60 minutes.


Fentanyl "lollipops" (oral transmucosal Fentanyl)

• 15 to 20 mcg/kg

• Increased volume of gastric contents

• Nausea and vomiting

• Pruritus

• Hypoventilation (SpO2 <90)


1. Metoclopramide (Reglan) PO or IV: 0.2 mg/kg

2. Ranitidine (Zantac) PO 2.5 mg/kg

3. EMLA cream: Eutectic mixture of Lidocaine and Prilocaine. For cutaneous application by occlusive

dressing one hour preoperative

4. Glycopyrrolate: consider for selected patients for planned airway instrumentation; e.g.: fiberoptic endoscopy, oral or upper airway surgery, cleft palate)5-10 mcg/kg IV or 10 mcg/kg IM

Preoperative interview:SAY GOOD, YES sleepy breeze anesthetic vapors pinch hug your arm stickers will be neat! fun! might get the giggles make you laugh feels funny take a little nap good job, good boy/ girl proud of you cool, refreshing nice little back rub

NOT BAD, NO gas bad smell, stink, stench, bee sting take blood pressure ekg pads won't hurt don't cry make you cry feels bad put you to sleep don't be bad cold solution press on your back

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Fasting:

Clear liquids - 2-3 h before the procedure

If infants are breast fed - 4 h before the procedure

For older patients = the adults rule

Be aware of dehydration

Induction of Anesthesia:

Inhalational induction:

Younger than 12 months

After the induction, place the intravenous catheter

Use suggestions in older child (pilot’s mask)

In a case of difficult airway - Fiberoptic intubation


Rectal induction:

Methohexital Thiopental Ketamine Midazolam Technique no more intimidating than rectal temperature measurement Usual time of onset ~ 10-15 min


Intramuscular induction:

Most common used Ketamine

Disadvantage painful needle insertion

Advantage: reliability


Intravenous induction:

The most reliable and rapid technique Disadvantage - starting intravenous line If patient is older ask the patient If you insert IV line:

I. Do not allow the patient to see it

II. Use EMLA cream III.If use local - ask the

patient if there is any sensation on puncture

Patient with full stomach:

Treat the same as adult with full stomach:

RSI with ODL using cricoid pressure Tell the patient that will feel “touching on the neck” Be aware of VO2 (desaturation) 0.02 mg/kg of Atropine administer before SUX to avoid bradycardia (usually after 2nd dose) Use Rocuronium 1.2 mg/kg Use Succinylcholine 1-2 mg/kg if really need short duration (difficult airway)

Endotracheal tubes:Recommended Sizes and Distance of Insertion of EndotrachealTubes and Laryngoscope Blades for Use in Pediatric Patients

RECOMMENDEDAge Of The

Patient Diameter(internal)

Size of theBlade Distance

Premature(<1,250 g) 2.5 0 6–7

Full term 3.0 0–1 8–101 y 4.0 1 112 y 5.0 1–1.5 126 y 5.5 1.5–2 1510 y 6.5 2–3 1718 y 7–8 3 19

4 + (1/4) (age) = size; 12 + (1/2) (age) = depth

Intravenous fluids:

Calculation of Maintenance Fluid Requirements for PediatricPatients

Weight(kg) Fluids (mL/hour) 24-H Fluids (mL)

<10 4 mL/ kg 100 mL/ kg11–20 40 mL + 2 mL/ kg > 10 1,000 mL + 50 mL/ kg > 10>20 60 mL + 1 mL/ kg > 20 1,500 mL + 20 mL/ kg > 20

Include if present: Fluid deficitsThird spaces lossesHypo/hyperthermiaUnusual metabolic fluids demands

Fluid requirements in neonates:

During the 1st week reduced fluid requirements:

Day 1 - 70 ml/kgDay 3 - 80 ml/kgDay 5 - 90 ml/kgDay 7 - 120 ml/kg

Concern is immaturity of the neonatal kidney The volume of extracellular fluids in neonates is large Consider use of radiant warmers, and heated humidifiers - decrease insensible water loss Use LR for replacement, D5% with 0.45 NS by piggyback

Packed Red Blood Cells:The use has diminished because of disease transmission (HIV, Hep C,B. etc)Blood volume:

Premature infant - 100 -120 ml/kg

Full-term infant - 90 ml/kg3-12 month old child - 80 ml/kg1 year and older child - 70

ml/kg

EBV (starting Hct - target Hct)MABL =

Starting Hct

Packed Red Blood Cells (2):

Child usually tolerates Hct ~ 20 in mature children If:

Premature, Cyanotic congenital disease

Hct ~ 30 O2 carrying capacity

No one formula permits a definitive decision Replace 1ml blood with 3 ml of LR Lactic acidosis is a late sing of decreased O2 carrying capacity Be aware of blood disorders (sickle cell disease)

Fresh Frozen Plasma:

Use to replenish clotting factors during massive transfusion, DIC, congenital clotting factor deficits Usually replenished if EBL = 1-1.5 TBV A patient should be never given FFP to replace bleeding that is surgical in nature If transfused faster than 1.0 ml/kg/min severe ionized hypocalcemia may occur If occurs - Rx. with 7.5-15 mg/kg Ca++ gluconate Ionized hypocalcemia can occur in neonates frequently because of decreased ability to mobilize Ca++ and metabolize citrate

Ionized Hypocalcemia:

Platelets:

Find etiology - TTP, ITP, HIT, DIC, hemodilution after massive blood transfusion

Consider transfusion if Platelets < 50.000

In certain hospitals platelet function test is available

If Platelets < 100.000 and EBL = 1-2 TBV - transfusion more likely If Platelets > 150.000 and EBL > 2 TBV transfusion more likely

Monitoring the Pediatric Patients:

Must be consistent with the severity of the underlying medical condition Minimal monitoring:

I. 5 ASA monitorsII. Precordial stethoscopeIII. Anesthetic agent

analyzer Use of capnograph and O2 analyzers is associated with high incidence of false alarms from:

movement artifact light interferenceelectrocautery

Intraarterial catheter - most common radial Pulmonary artery catheters are rarely indicated because equalization of the pressure right/left heart In a case of severe multisystem organ failure insertion of PAC might be particularly useful Multilumen catheters are valuable in ICU patients In a case of rapid fluid replacement peripheral venous catheter might be very useful Short-term cannulation of femoral/brachiocephalic or umbilical vein may be life-saving

Special Monitoring the Pediatric Patients:

Anesthesia Circuits:

Nonrebreathing circuits:1. Minimal work of breathing2. Speeds-up rate of

inhalational induction3. Compression and compliance

volumes are less (small circuit volume) Use of Mapleson D system is recommended in children < 10 kg

More sensitive to changes in gas flow

More sensitive to humidification

Actual delivered volume is greater than

other systems

Mapleson D Circuit:

Gas disposition at end-expiration during spontaneous ventilation

Gas disposition at controlled ventilation

Neonatal Anesthesia:

Understand differences in PhysiologyPharmacologyPharmacodynamic

response Most of the complications that arise are attributable to a lack of understanding of these special considerations prior to induction of anesthesia Be aware of:

Sudden changes in hemodynamics

Unexpected responsesUnknown congenital problem

Neonatal Anesthesia (2):

Children < 1 year old have more complications:

I. OxygenationII. VentilationIII. Airway managementIV. Response to volatile

agents and medications Stress response is poorly tolerated Consider:

1. Organ system immaturity2. High metabolic rate3. Large ratio body

surface/weight4. Ease of miscalculating a

drug dose

Neonatal Anesthesia (3):

Prevention of paradoxical air emboli

Fluids instituted with volume-limiting devices

Minimize thermal stress

Use flow-through capnograph if possible

Prevent retinopathy of prematurity by:

Lower FiO2

Keep CO2 within normal range

Neonatal Anesthesia (4):Stress Response:

Poorly tolerated

Use opioid technique (blunt pain response)

Ketamine is excellent choice –stable intraoperative hemodynamics

Potent volatile anesthetics are poorly tolerated

No one should be denied anesthesia because of the age or weight

Special Problems in Neonatal Anesthesia:

Meningomyelocele:

Underestimating fluid or blood loss from the defect High association with hydrocephalus Possibility of cranial nerve palsy Potential for brain-stem herniation

Special Problems in Neonatal Anesthesia (2):

Pyloric stenosis: First 3-6 weeks in life Anesthesiologist concern:

I. Full stomach with bariumII. Metabolic alkalosis with Hypochloremia and HypokalemiaIII. Severe dehydration

Surgery is never emergency Metabolic correction mandatory before the surgery Suction the stomach before induction Consider awake intubation or RSI


Omphalocele and Gastroschisis:

Omphalocele occurs because of failure of the gut to return to the abdominal cavity at 10th week of life Fine membrane covers intestines and abdominal contents

Gastroschisis develops later in life after gut has returned into abdominal cavity Abdominal contents and organs are not covered with any membrane – risk of infection


Omphalocele


Gastroschisis


Omphalocele and Gastroschisis(2): Anesthesiology concern:

1. Dehydration2. Massive fluid loss (exposed

viscera and 3rd space loss)3. Heat loss4. Difficulty of surgical closure5. High association with prematurity, congenital defects, including cardiac anomalies

Minimize infection, Replenish fluids, be liberal in muscle relaxants, consider hypotension and

difficulty ventilation


Omphalocele and Gastroschisis(3):

During closure consider* difficulty ventilation* hypotension* abdominal pressure may

compromise liver function and alter drug metabolism

During closure of big defects monitoring of the bladder pressures is important: if the pressure is

< 20 cm H2O attempt is to close, > 20 cm H2O closing in stages.

Special Problems in Neonatal Anesthesia(3):

Omphalocele and Gastroschisis (4):

Be aware of Beckwith-Wiedemann syndrome:

Profound hypoglycemia

Hyperviscosity syndrome

Associated visceromegaly


Omphalocele and Gastroschisis ddx. (5):

1. Much greater associated defects with Omphalocele

2. More fluid loss associated with Gastroschisis


Tracheoesophageal fistula anomaly(1):

90 % proximal atresia of esophaguswith distal fistula

Consider aspiration pneumonitis. VATER syndrome:

I. VertebralII. AnalIII. TracheoesophagealIV. Renal

MCC of death – cardiac anomalies

T-type

Trachea


Tracheoesophageal fistula anomaly(2):

Major issues are:

Aspiration pneumonia

Overdistention of the stomach

Inability to ventilate

Postoperative intensive care

T-type

Trachea


Tracheoesophageal fistula anomaly(3):Induction: Awake intubation Deliberate right main stem intubation Catheter in esophagus Prone position with head-up Avoid massive distention of the stomach

by gentle ventilation Careful confirmation of tube position

by moving tube mm by mm (position must be between fistula and tracheal bifurcation) Tape precordial stethoscope over the left chest

T-type

Trachea


Diaphragmatic hernia: Usually presentation on

1st day of life Almost all viscera can be in the

chest cavity Anesthesia concerns:

I. HypoxemiaII. HypotensionIII. Stomach herniationIV. Pulmonary hypertensionV. Systemic hypotension

Shifted mediastinum

Diaphragmatic hernia


Diaphragmatic hernia (2):1. Awake intubation2. Intraarterial catheter3. Use opioids (stress response)4. Use Pancuronium5. Avoid hypothermia6. Avoid any myocardial depressant7. Avoid N2O (abdominal distention)8. Aware of barotrauma-induced pneumothorax9. Adequate intravenous access10. Plan postoperative care

Shifted mediastinum

Diaphragmatic hernia


Former preterm infant (<37 weeks):

High incidence of apnea risk factors: Respiratory distress syndrome

Bronchopulmonary dysplasiaNeonatal dyspneaNecrotizing enterocolitisOngoing apnea at the time of surgeryUse of narcoticsLong acting muscle relaxantsAnemia (Hct < 30)

Regional Anesthesia and Anesthesia:(brief overview)

Most regional anesthetics are safe to use

Strict attention to:DoseRoute of administrationProper equipment used

Common:Caudal blocks

pediatric anesthesia

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