Anesthetic Considerations for Surgery for Premies, Neonates and Infants

Question 1

preop assessment of bebes

Answer 1

• PCA, postconceptual age = gestational age + postnatal age
• CURRENT weight, bebes change errday
• allergies
• comorbidities, general health, growth and devt
• physical exam (aw, heart, lungs, visible veins)
• special anesthetic considerations
  
  • infection risk
  • IVH
  • apnea risk
  • temp control
  • ventilation/oxygenation
  • sat goals 90-94%
  • glucose, electrolyte and fluid mgmt
• congenital anomalies might not be apparent yet*
• Presence of 1 anomaly usually means they have another.*

Question 2

NPO guidelines

Answer 2

• the MINIMUM acceptable time from ingestion
• 2 hrs - clears
• 4 hrs - breast milk
• 6 hrs - formula, non-human milk

Question 3

GA considerations for premies

Answer 3

• ICU transport considerations if intubated already
• [un]cuffed ETT options
• possibility of difficult aw and subglottic stenosis
• verify ETT prior to transport, and with all position changes
• NGT to decompress and facilitate ventilation
• ventilation may be difficult - poor compliance, avoid barotrauma and excessive O2
• NSAIDs contraindicated (immature kidneys, can cause premature closure of PDA - so think about ductal dependent bebes)
• IV caffeine if at risk for apnea? Consider it!

Question 4

brain growth and anesthesia, takeaways

Answer 4

• all anesthetics/sedatives used have shown loss of nerve cells
• formation of brain structures/growth begins early in pregnancy and up to 3 yrs old
• myelination complete around 6 yrs old?!

Question 5

summarize the GAS trial

Answer 5

• 28 hospitals
• infants < 60 wks postmenstrual age born at >26 wks gestation
• RCT to sevoflurane or regional anesthetic
• no differences if ~1 hr GA and regional

Question 6

inhalational agents in prematurity

define MAC

Answer 6

• MAC = inahaled anesthetic depth at which 50% of pts respond to painful stimulus with movement
• MAC varies with age, esp with premies and critically ill pts
• bc the neonatal heart is dependent on ECF Ca++, premies may be more susceptible ot cardiodepressant effects of inahalational anesthetics

Question 7

SEVO, ISO, DES MAC values for neonates, infants, small kids

Answer 7

• in general, 1.2-2 MAC, chart peaks at 1-6 months old, then goes down
• Sevoflurane
  
  • neonates: 3.2
  • infants: 3.2
  • small children: 2.5
• Isoflurane
  
  • neonates: 1.6
  • infants: 1.8
  • small children: 1.4
• Desflurane
  
  • neonates: 9.2
  • infants: 10
  • small children: 8.2

Question 8

fentanyl and ketamine

Answer 8

• Fentanyl
  
  • analgesia. doesn’t produce unconsciousness alone
  • Vd higher
  • reduced T1/2 (6-32 hrs in premies, 2-3 hrs in children and adults ****emailed Dr. Funk about this
• Ketamine
  
  • analgesia, amnesia and unconsciousness

Question 9

propofol in premies

Answer 9

• reported episodes of protracted hypotension and low CO
• use of lower doses in preterm and infants
• gtts are rarely used L-T bc of PRIS risks

Question 10

midazolam and dexmedetomidine in premies

Answer 10

• midazolam
  
  • combined with opioid for complete anesthetic
  • decreased clearance esp in the setting of decreased liver fn
• dexmedetomidine
  
  • may alleviate neuronal cytotoxicity when used as a pre-tx for propofol
  • (may be neuroprotective)
  • use less volatiles, more paralytics, which doesnt cross the BBB

Question 11

fetal hemoglobin (HbF)

Answer 11

• main O2 transport protein in the fetus, until 6 months
• binds O2 with greater affinity
  
  • HbF can carry 20-50% more O2 than maternal Hgb can
• results in leftward shift of oxyhemoglobin dissociation curve
• HbF in utero is 50% greater than that of mother

Question 12

physiologic anemia in healthy term infants

Answer 12

• expected anemia in bebes
• in 1st 6 months, adult Hb synth is activated and HbF is stopped
• normal: Hgb falls during 9th and 12th week
• nadir of anemia is 10-11 g/dL
  
  • shorter lifespan of RBCs, ↓ in erythropoeisis
    *

Question 13

physiologic anemia in premature infants

nadir and when it’s reached

what you see clinically

transfusion goal

when does the Hgb level stabilize out?

Answer 13

• already have lower HbF
• nadir is lower (7-9 g/dL, compared to normals 10-11 g/dL) and reached earlier (4-8 wks, compared to normals 9-12 wks)
• clinically, the younger the baby, the higher the fraction of HbF and thus (lower?) O2 carrying capacity and O2 delivery to tissues. This is offset by rightward shift in oxyhgb curve with increased 2,3-DPG and adult Hgb production
• transfusion goal Hct > 30%
• Hgb stabilizes out at 3 months of life, at about 11-12 g/dL, until 2 yrs old

Question 14

anesthesia for surgical procedures

Answer 14

• premies don’t require surgery unless their condition is life-threatening
• must optimize cardiac, resp, anemia, electrolytes, metabolic acidosis, and coagulopathy
• careful attn to med administration:
  
  • TB syringes
  • saline flush after every med (might only be giving 0.1 mL)
  • give in stopcock closest to pt
  • remove all air bubbles
• avoid fluid overload, no free-flowing IV sets

Question 15

common procedures requiring anesthesia in premies (9)

Answer 15

• PDA ligation (can be done bedside in NICU)
• laparotomy for NEC/bowel perf
• inguinal hernia repair
• vitrectomy or laser for ROP
• CT scan/MRI
• repair of congenital diaphragmati hernia
• laparotomy or silo for ophalocele & gastroschisis
• laparotomy for malrotation or volvulus
• tracheoesophageal fistula repair

Question 16

ligation of PDA

Answer 16

• PDA causes L-R shunting, causing excess pulmonary BF, CHF and respiratory failure
• fetus: PDA means blood goes from pulmonary circulation to aorta
• newborn: PDA means blood goes from aorta to pulmonary circulation
• remains open in 1/2,500 live births
• in premies with RDS or pHTN R-L shunting produces cyanosis
• medical therapy = COX inhibitor
  
  • indomethacin or ibuprofen
• surgical therapy = L thoracotomy, retraction of L lung

Question 17

preop preparation for PDA ligation

Answer 17

• assess ABP, HR, ABG, vent settings, inspired FiO2
• availability of pRBCs - aorta and PA are close to the PDA so they can be nicked
• abx

Question 18

intraop mgmt of PDA ligation

Answer 18

• BP monitoring - RUA reflect cerebral perfusion and pre-ductal blood
• pulse ox on RUA and LE.
  
  • Also helps surgeon to confirm which vessel to ligate (DA versus aorta)
• EtCO2
• ETT should have minimal leak - surgical retraction of the lung necessitate increasing ventilator inspiratory pressures and inspired O2
• opioids, amnesic, muscle relaxation
• intercostal nerve block by surgeon at the completion of surgery

Question 19

complications of PDA ligation

what will you see with successful PDA ligation

Answer 19

• inadvertent ligation/laceration of aorta or PA
  
  • aortic clamp will result in loss of signal to LE pulse ox
  • PA clamp will result in decreased SpO2 to both extremities and EtCO2
• successful PDA ligation will result in increased DBP and MAPs, and the PDA murmur will disappear

Question 20

NEC (necrotizing enterocolitis)

• what is it
• who gets it
• causes

Answer 20

• a gastrointestinal emergency that is associated with an intense systemic inflammatory response, secondary to sepsis from intestinal necrosis and increased mucosal permeability.
• This systemic response often leads to multiorgan dysfunction, long-term morbidity (e.g., malabsorption, short gut syndrome, neurodevelopmental deficits), and mortality (20% to 30%, as high as 50% in surgical NEC)
• who gets it: 85% LBW infants, <1500g
  
  • 50% mortality rate
  • morbidity = short bowel syndrome, sepsis and adhesions
• cause is uncertain and multifactorial. Results in intestinal mucosal injury 2/2 ischemia and ulceration of the bowel

Question 21

early sx’s of NEC

+ clinical presentation

Answer 21

• Early signs: think shocky bowel
  
  • abdominal distension
  • bloody diarrhea
  • temp instability
  • lethargy
• metabolic and hematologic abnormalities
  
  • hyperK+
  • hypoNa+
  • metabolic acidosis
  • hyper or hypo glycemia
  • coagulopathy/DIC
  • anemia
  • hallmark sign is intramural gas collection
• often we’ll find them already intubated d/t abdominal distension and NGT/OGT suctioning and HD instability
• bowel perforation and free air in abdomen is usually the cause of emergent surgery

Question 22

surgical mgmt of NEC

(rationale for performing surgery on them)

Answer 22

• this is a medical emergency!
• bc the intestine can no longer hold waste, bacteria can pass into the bloodstream and lead to sepsis
• will do either a primary peritoneal drainage, or laparotomy with resection of necrotic bowel
  
  • primary peritoneal drainage = smaller incision and fewer anesthetic requirements (performed at bedside)

Question 23

anesthetic mgmt during NEC surgery

• take care with _____ and avoid ______
• lines
• transfusions

Answer 23

• aspiration risk - possible RSI or awake intubation
• volatiles poorly tolerated - will use narcotic technique with muscle relaxation
  
  • titrate carefully, as they’re volume depleted and septic
• avoid N2O
• 2 IVs and A-line
• vasopressors (DA and EPI) for renal perfusion and CO
• large fluid loss or blood loss
  
  • resuscitate, pRBCs, FFP, plts
• neonatal transfusion is weight-based
  
  • hypovolemia compromises tissue oxygenation, EBV is generally ~90-100 mL/kg
  • pRBCs 10-15 mL/kg
  • FFP 10-15 mL/kg
• ​correct electrolytes and BG

Question 24

preop mgmt for NEC

(Box 24-8)

Answer 24

• optimize HD and coag status
• check blood product availability
• check placement of ETT, caths
• know acceptable HD parameters (BP, PSO₂, FiO₂)
• IV access

Question 25

intraop mgmt for NEC (Box 24-8) postop mgmt for NEC

Answer 25

* standard monitors, A-line * maintain HD stability * vasoactive suppoort (again, DA or EPI) * opioids, or low-dose volatiles, + NMBDs * check BG and electrolytes * fluid resuscitation: FFP, cryo, pooled RBCs * close attn to temp homeostasis - forced air warmer * postop = mechanical ventil, sedation and analgesia

Question 26

max ABL | (+ EBL calculation)

Answer 26

* EBL = kg x 100 mL/kg * ABL = EBV x (starting Hct - allowable Hct) / starting Hct * ex: 120 mL (29-25) / 29 = **16 mL allowable**

Question 27

inguinal hernia repair - incidence - complications - anesthetic plan

Answer 27

* common in premies (1/3 of premies, as opposed to 1% in F-T neonates) * complications * incarcerated bowel * instestinal obstruction * gonadal infarction * infxn * hematoma * recurrent hernias * GA or regional are appropriate * LMA ok for small defects * **inadequate depth of anesthesia can result in laryngospasm when the surgeon pulls on the hernia sac** * ETT required for large defects and for NMBD * blocks: ilioinguinal, iliohypogastric, caudal/epidural blocks

Question 28

eye surgery for ROP describe the 3 treatments

Answer 28

* **Diode laser photocoagulation** - for moderate ROP (bedside) * 10-30 min treatments in a series every few wks * topical anesthesia alone, IV sedation, or GA * **Cryotherapy** - freezing probe is placed on avascular retina (in OR) * GA always * between 32-42 PCA * **Scleral buckling and vitrectomy** - less common with better screening/earlier tx, more for severe ROP with retinal detachment (in OR) * GA always * kid is like 6 mo's - 1 yr old

Question 29

anesthesia for radiologic imaging

Answer 29

* \<30 wks get brain MRI, in some hospitals * class said a lot just did ultrasounds * MRI is replacing US and CT for ass't of IVH to prevent radiation exposure. AND it can identify congenital lesions, vasc malformations, and ischemic injury * requires immobility, hence us * anesthesia can range from PO meds, sedation, to GA * off-site anesthesia considerations, MRI-compatible monitoring equipment * monitoring for postop apnea considerations

Question 30

congenital diaphragmatic hernia

Answer 30

* diaphragm fully formed by 7-10th weeks (1st trimester) * anatomic defects permit intrusion of abdominal contents into thoracic cavity * early - abdominal mass inhibits cardiopulmonary growth * severity of lung hypoplasia is associated with morbidity and mortality. * neg correlates with gestational age at the time hernia occurred * late - occurs near/after delivery * associated with mature, well-developed lungs * minimal problems with ventilation

Question 31

CDH (congenital diaphragmatic hernia) - hallmark signs - incidence - 1 specific type of hernia - when is it lethal

Answer 31

* hallmark signs: hypoxia, scaphoid abdomen, evidence of bowel in the thorax * may be dx'd in utero * PDA prob didn't close * 1:25,000 live births * **Bochadalek-type hernia** (95% of CDH cases) are likely to have concurrent birth defects * CHD 20-40% * chromosomal abnormalities 5-15% * CDH is potentially lethal d/t pHTN, pulmonary hypoplasia (*lungs too squished to grow normally*), and associated cardiac or congenital defects * 40-50% mortality

Question 32

CDH (congenital diaphragmatic hernia) - mgmt - what's the main reason that it's dangerous - worst case scenario

Answer 32

* med mgmt affects timing of surgery * guts in the thorax isn't in and of itself life-threatening. Compression of developing pulmonary structures impedes transition to neonatal circulatory pattern * hypoplastic lungs * intrapulmonary shunting and inadequate gas exchange * decreased total cross-sectional area --\> pHTN * often requires secured aw, mech ventilation, and gastric decompression right after delivery * may require ECMO, HFOV (high-freq oscillatory ventilation), and inhaled NO

Question 33

CDH (congenital diaphragmatic hernia) surgical approach

Answer 33

* surgical closure standard of care * subcostal or thoracic lap * L\>R lesions * recurrent defects can be approached thru the abdomen (min invasive) * primary closure vs synthetic patch for large defects * might be delayed until medically optimized * may occur before, during, or after ECMO (duh) * surgery *transiently* worsens pHTN, may cause persistent fetal circulation (PDA opens for business) * *CDH outcomes are a fn of the underlying **pulmonary hypoplasia and pHTN***

Question 34

anesthesia mgmt of CDH (congenital diaphragmatic hernia) repair

Answer 34

* initial: definitive airway control, optimize oxygenation/ventilation * avoid mask ventilation - limit gastric insufflation * NGT/OGT * supine or lateral * pre- and postductal monitoring, gives early sx of R --\> L shunt or pHTN * reactive pulmonary vasculature * avoid things that ^ PVR: hypoxemia, acidosis, hypotension, hypercarbia * PIV x2, A-line, serial ABGs * EBL 5-10 mL/kg * NEED PARALYSIS, NARCS, (limited inhalational agents) * limit inspired O2 and NO N2O * supportive care during transport can be challenging

Question 35

improved survival rates in recent years bc of:

Answer 35

* delaying surgery to stabilize transitional circulation * LPV + PEEP * permissive hypercapnia

Question 36

NO and ECMO for CDH (congenital diaphragmatic hernia)

Answer 36

* inhaled NO * specific pulmonary vasodilator (avoids systemic hypotension) * used for refractory pHTN to reduce R-L shunting, and improve oxygenation * short-acting, must be delivered thru specially metered apparatus * ECMO, yay! * permits lungs to rest/mature while providing gas exchange thru membrane oxygenators * inclusion/exclusion criteria * contraindicated in IVH bc circuit needs heparin * VV - double lumen in IJ * VA - IJ and carotid

Question 37

CDH (congenital diaphragmatic hernia), in general

Answer 37

* variable presentations/severity * no single technique will address all requirements * if oxygenation is compromised, global tissue hypoxemia will result in significant metabolic acidosis * can be treated with bicarb is adequate ventilation is ensured * sedation is important to prevent catecholamine release (^s PVR) * severe CV compromise should be treated with volume and inotropes * in general, there's been a trend to stabilize cardiorespiratory status to the extrauterine env't before surgical repair (48 hrs --\> 4-6 days)