pediatric anesthesia
DESCRIPTION
Presented May 2003. Pediatric Anesthesia. Abdulaziz Hisham Al Gain. Development: Organogenesis - 1 st 8 weeks Organ function - 2 nd trimester Body mass - 3 rd trimester. Changes in cardiovascular system: Removal of placenta from circulation - PowerPoint PPT PresentationTRANSCRIPT
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.
Pharmacological premedication options (4)
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.
Pharmacological premedication options (5)
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.
Pharmacological premedication options (6)
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
Pharmacological premedication options (7)
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.
Pharmacological premedication options (8)
Fentanyl "lollipops" (oral transmucosal Fentanyl)
• 15 to 20 mcg/kg
• Increased volume of gastric contents
• Nausea and vomiting
• Pruritus
• Hypoventilation (SpO2 <90)
Pharmacological premedication options (9)
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
http://metrohealthanesthesia.com/edu/ped/pedspreop4.htm
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
Induction of Anesthesia:
Rectal induction:
Methohexital Thiopental Ketamine Midazolam Technique no more intimidating than rectal temperature measurement Usual time of onset ~ 10-15 min
Induction of Anesthesia:
Intramuscular induction:
Most common used Ketamine
Disadvantage painful needle insertion
Advantage: reliability
Induction of Anesthesia:
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
Special Problems in Neonatal Anesthesia (3):
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
Special Problems in Neonatal Anesthesia (3):
Omphalocele
Special Problems in Neonatal Anesthesia (3):
Gastroschisis
Special Problems in Neonatal Anesthesia (3):
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
Special Problems in Neonatal Anesthesia (3):
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
Special Problems in Neonatal Anesthesia(3):
Omphalocele and Gastroschisis ddx. (5):
1. Much greater associated defects with Omphalocele
2. More fluid loss associated with Gastroschisis
Special Problems in Neonatal Anesthesia(4):
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
Special Problems in Neonatal Anesthesia(4):
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
Special Problems in Neonatal Anesthesia(4):
Tracheoesophageal fistula anomaly(2):
Major issues are:
Aspiration pneumonia
Overdistention of the stomach
Inability to ventilate
Postoperative intensive care
T-type
Trachea
Special Problems in Neonatal Anesthesia (4):
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
Special Problems in Neonatal Anesthesia (5):
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
Special Problems in Neonatal Anesthesia (5):
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
Special Problems in Neonatal Anesthesia (6):
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