congenital diaphragmatic hernia

Question 1

what are some signs of congenital diaphragmatic hernia?

Answer 1

nasal flaring, sternal retractions, scaphoid abdomen, absent BS on the left

Question 2

what changes in the lung do you see in the presence of CDH?

Answer 2

• impaired maturation with decreased alveoli and surfactant - impaired gas exchange
• abnormal pulm vasc with increase in arteriolar ms mass and subsequent pulm htn resulting in extrapulm shunt through PFO and PDA (worsen hypoxia, hypercarbia, acidosis, which exacerbates pulm htn)
• intrapulmonary shunting

Question 3

what is A-a gradient?

Answer 3

alveolar-arterial gradient. it assesses the integrity of the alveolar unit.

Aa-gradient = PAO2 - PaO2

PAO2 = FiO2(Patm-Ph20) - PaCO2/0.8
PAO2 = FiO2(760-40) - PaCO2/0.8

normal Aa gradient is 5-10 mmHg
it increases by 1 mmHg for every decade

Question 4

if a patient is hypoxic but the Aa gradient is normal, what does that indicate?

Answer 4

hypoventilation (neuromuscular or CNS dz)
low FiO2 (high altitude)

Question 5

if patient is hypoxic with high Aa gradient what does that indicate?

Answer 5

• R to L intrapulmonary shunt (fluid in alveoli - ARDS, CHF, pneumonia)
• V/Q mismatch (increased dead space - PE, atelectasis, COPD, PTX)
• alveolar hypoventilation from interstitial lung disease

Question 6

what Aa gradient indicates a poor prognosis for CDH?

Answer 6

> 500 mmHg is poor prognosis of survival

400-500 mmHg is uncertain

Question 7

what is the initial treatment of CDH?

Answer 7

medical stabilization with a goal to reduce pulm htn (and thereby reduce the right to left shunt through the PDA and PFO).

• avoid mask vent (may distend stomach and thereby decrease the amount of space for the lungs in the thorax)
• avoid excessive endotracheal suctioning (may decrease FiO2)
• provide supp oxygen
• IV access
• intubate (awake or RSI), vent settings aim to decrease hypoxia, hypercarbia, acidosis and no high airway pressures
• insert NGT/OGT and decompress stomach
• sedation to reduce catecholamine release (fentanyl 3 mcg/kg/hr)
• ms relaxant to reduce o2 consumption
• normothermia (hypothermia can worsen pulm htn)

can take 24-48 hours if mild pulm htn
7-15 days if severe

Question 8

what testing would you want?

Answer 8

ABG, chest xray (hypoplastic lung, bowel in ipsilateral hemithorax, heart/mediastinal deviation, contralateral lung compression), echo (to ID congenital defects, right heart dysfunction, pulm htn)

Question 9

if PVR remains elevated after initial interventions, what is your next line of therapy?

Answer 9

• pulm vasodilators (PGE1 or NO)
• exogenous surfactant (enhance NO and help prevent ventilator-induced injury)
• high-freq oscillatory ventilation
• PDA ligation to reduce shunting (can result in right heart failure)
• ECMO

Question 10

what is the goal of management?

Answer 10

preductal O2 sat of >85% with peak inspiratory pressure

Question 11

what concerns do you have with PGE1?

Answer 11

nonspecific vasodilation, can cause hypotension

will keep ductus arteriosus patent (can reduce right ventricular afterload

Question 12

what make NO a good choice if the patient becomes hypotensive with PGE1?

Answer 12

it is a specific pulmonary vasodilator and is inactivated with exposure to Hgb so doesn’t affect SVR.

Question 13

when would milrinone be a good choice for pulmonary vasodilation?

Answer 13

in setting of right-heart failure

Question 14

what are some risks of ECMO?

Answer 14

• need anticoagulation and inactivation of platelets so risk of ICH and pulm hemorrhage
• emobolism
• infection
• vascular trauma
• circuit failure

Question 15

when is ECMO contraindicated?

Answer 15

• gestation

Question 16

you need IV access. what considerations are there?

Answer 16

i would probably want central access and would preferentially select the umbilical vein or femoral vein. the neck veins may be needed later for ECMO and also carry a risk of pneumothorax which i would like to avoid in this patient that already has respiratory compromise.

i would also consider an upper extremity peripheral line. once the abdominal contents are returned to the abdomen, intraabdominal pressure will increase and possibly compress the IVC.

Question 17

how do you place an umbilical vein catheter?

Answer 17

• sterile prep and drape
• CAUDAL traction on the umbilical stump (cephalad traction facilitates insertion into the umbilical artery)
• insert a soft catheter filled with heparinized solution (length should approximate distance between insertion site and right atrium
• check placement with xray
• secure catheter with suture, occlusive dressing

Question 18

the catheter will not advance into the IVC, can you use it?

Answer 18

temporarily if ensured it was not more than 2 cm beyond the abdominal surface or to the point where blood is freely aspirated. you could not monitor CVP.

the catheter can become wedged in the liver after failing to traverse the ductus venosus and if so, using the catheter can lead to hepatic injury

Question 19

what complications are associated with UVC

Answer 19

• infection
• portal/mesenteric thrombosis
• cirrhosis
• endocarditis
• cardiac tamponade
• liver abscess
• hemorrhage
• subcapsular hematoma

complications increase as duration of catheterization increases

Question 20

where is the ideal position for umbilical artery catheterization?

Answer 20

advanced into the descending aorta to T7-9 (may increase risk of embolization into renal or mesenteric vessels).

can advance to L3-5, just above the bifurcation. however this placement is difficult to maintain and can lead to tissue necrosis if the catheter migrates into either iliac artery

Question 21

can UAC be used for drug administration?

Answer 21

it can until alternative access can be established. however, there are many complications associated with its use.

• air embolism
• exsanguination
• vasospasm
• refractory hypoglycemia (infusing glucose inot the vessels of the pancreas with subsequent hyperinsulinemia

Question 22

what monitors would you place to anesthetize this patient?

Answer 22

1. standard ASA monitors
2. 5-lead EKG (potential cardiac defects, pulm htn, R to L shunt)
3. right radial art line (preductal PaO2, more accurate reflection of O2 to brain) for BP monitoring (pulm htn, acid-base disturbances, potential abd compartment syndrome) and frequent ABG monitoring (vent management, esp during diaphragm closure)
4. esoph/rectal temp
5. CVP for eval of volume status and RV fxn
6. pre & post-ductal SpO2 to eval sat and identify and increase in R to L shunt through PDA

Question 23

describe fetal circulation.

Answer 23

placenta - umbilical vein:
1/3 - ductus venosus to IVC to right atrium
2/3 - portal vein to right atrium:

from right atrium:
most blood - foramen ovale - left atrium
small amount - PA

from pulm artery:
most blood - ductus arteriosis - aorta
small amount - PV - LA

from left atrium - left ventricle - aorta:

from aorta:
internal iliac arteries - umbilical arteries - placenta - maternal circulation

Question 24

would you use 100% FiO2 for this case?

Answer 24

no. it can lead to pulmonary oxygen toxicity (usually with prolonged exposure). it has also been associated with increase in retinopathy of prematurity in neonates under 44 weeks gestation (at which time vascularization of the retina is complete).

hypoxemia is also not acceptable (increased metabolic acidosis and increased PVR with further R to L shunting). i would ideally maintain an O2 sat of 87-94% and PaO2 of 50-80 mmHg, with plans to increase FiO2 if pt became hypoxic or acidotic.

Question 25

what is the pathophysiology of ROP?

Answer 25

it is a vasoproliferative retinopathy occuring in neonates less than 44 weeks of postconceptual age. retina begins vascularization around week 16 and finishes in week 44 postconception.

high O2 leads to vasoconstriction and obliteration of retinal vessles resulting in the inability to meet the metabolic demands of the growing retina. the relative hypoxia leads to neovascularization into the vitreous humor.

Question 26

what are some risk factors of ROP?

Answer 26

1. hyperoxia

2. prematurity (especially

Question 27

pt becomes cyanotic after induction. right hand SpO2 = 87%, foot reads 64%. what is going on?

Answer 27

> 5% difference in the reading from the preductal (right hand) saturation to the postductal (foot) saturation indicates coarctation of the aorta (narrowing at insertion of ductus arteriosus) or significant R to L shunt through the PDA.

Question 28

how do you keep PDA open? closed?

Answer 28

keep open - PDE1 analogs (misoprostol)

close - PDE1 inhibitors (indomethacin)

Question 29

assume it is a R to L shunt, what would you do?

Answer 29

end goal is to reduce pulm htn, so:

1. decrease hypoxemia by increasing FiO2
2. decrease CO2 by hyperventilating (need to use low TV and high RR)
3. increase SVR if induction resulted in hypotension and vasodilation
4. reduce PVR by tx any acidosis with HCO3-, ensuring normothermia, adequate depth of anesthesia to reduce catecholamines

Question 30

the surgeon returns the abdominal contents to the abdomen and reveals a hypoplastic left lung. will you attempt to expand the collapsed lung with PPV?

Answer 30

no, because the pressure required to expand the collapsed left lung could put the right lung at risk of PTX, which could be disastrous.

Question 31

after returning the organs to the abdominal cavity, the pt becomes profoundly hypotensive and the O2 sat drops to 68%. what do you do?

Answer 31

1. alert the surgeon that the return of the abdominal contents to the abdomen has possibly increased intraabdominal pressure and subsequent IVC compression (leading to reduced preload and CO)
2. increase to 100% FiO2
3. check ECG for arrhythmia
4. check for PTX by checking lung compliance with hand ventilation and auscultating bilateral lung fields
5. ensure proper endotracheal tube placement (no mainstem intubation)
6. assess surgical field for large hemorrhage
7. if no other obvious cause, i would ask the surgeon to relieve the abdominal pressure (may have to do staged closures)
8. reduce volatile agent
9. administer fluids as hypovolemia can make the CV effects of ACS

Question 32

the surgeon places a silo and plans to close the defect at a later time. will you extubate?

Answer 32

i would not. controlled vent reduces O2 requirements, helps prevent/treat hypoxemia, hypercarbia, and acidosis.

Question 33

postop the pt is hypotensive, bradycardic and hypoxic.

Answer 33

1. increase FiO2 to 100%
2. hand ventilate if possible
3. check ECG for arrhythmia
4. auscultate the chest to ensure appropriate ETT placement and patency.
5. assuming no other obvious cause, i would have high suspicion for heart failure secondary to hypoxia, PTX, or worsening pulm htn

Question 34

BS diminished bilaterally. what do you do?

Answer 34

as left lung was hypoplastic, i would assume this is a right sided pneumothorax until proven otherwise. call for surgeon to emergently place a chest tube. if no surgeon available, i could place a 22 gauge angiocatheter into the second intercostal space at the midclavicular line.

Question 35

the neonate is hypothermic. is this concerning?

Answer 35

yes, this can worsen pulm htn. it increases O2 requirement and can result in acidosis, and increased PVR.
i would increase ambient temperature, utilizing heat lamps and forced air warmers, ensure warming of IVF and humidifying resp gases.