UBP 3.3 (Long Form): Pediatrics – Ligation of Patent Ductus Arteriosus

Question 1

Intra-Operative Management:

What monitoring would you utilize for this case?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO₂ retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO₂ 51 mmHg; PaO₂ 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 1

In addition to standard monitoring, such as an ECG, end-tidal CO2, inspiratory oxygen, inspiratory pressure, and oxygen saturation,

I would utilize a precordial and/or esophageal stethoscope to aid in monitoring of cardiopulmonary status and

an esophageal or axillary probe to monitor temperature.

Blood pressure should be monitored in the right arm (preductal) since clamping of the left subclavian artery may become necessary should the ductus be torn causing massive bleeding.

Oxygen saturation should be monitored on the right hand and a lower limb to provide pre-ductal and post-ductal readings respectively.

While invasive blood pressure monitoring and a CVP line would be helpful if already present, I would NOT routinely require them for this procedure.

Question 2

Intra-Operative Management:

Your resident asks where you would like to monitor blood pressure and oxygen saturation.

Does it matter?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 2

Narrow River 06:07

As I mentioned in my previous answer, blood pressure should be monitored in the right arm since clamping of the left subclavian artery may become necessary should the ductus be torn causing massive bleeding.

Oxygen saturation should be monitored on the right hand and a lower limb to provide pre-ductal and post-ductal readings, respectively.

Pre-ductal and post-ductal saturation monitoring can provide information about shunting (right-to-left shunting through a PDA results in a relatively lower post-ductal oxygen saturation) and

help the surgeon to avoid accidental ligation of the aorta (would result in post-ductal loss of waveform), or pulmonary artery (would result in both decreased pre-ductal and post-ductal oxygen saturation along with decreased end-tidal CO2).

(Great explanation at 10:00)

(12:35 – how confirm appropriate PDA ligation?)

(14:30 – more specific alternative questions)

Test-Taking Tips:

• Starting your answer to this question with, “As I mentioned…” serves to point out that you already anticipated this issue with the previous question, in case the examiner missed it.
• Be VERY careful not to sound impatient or arrogant in making this statement since this will only harm your relationship with the examiner, which is not helpful.

Question 3

Intra-Operative Management:

An ABG shows a pH of 7.30, PaCO2 of 51, Bicarbonate of 25, and PaO2 of 110 with a Fio2 of 40%.

What do you think about this information?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 3

Narrow River – Good discussion online 15:05 –

This ABG indicates a respiratory acidosis and a PaO2 that is higher than optimal given the risk of retinopathy of prematurity (ROP) in a premature infant such as this one (very premature infants weighing < 1000 g are at the highest risk of developing ROP).

Consideration should be given to increasing ventilation to correct the acidosis, and reducing the FiO2 to maintain a PaO2 of 50-80 mmHg or an oxygen saturation of 87-94% to minimize the risk of ROP.

• (Note: Recommendation of PaO2 varies from author to author. Just know a range that is reasonable.*
• Note: ROP can occur even in the absence of supplemental O2.)*

Xtra Q 18:20 – What is ROP?

Question 4

Intra-Operative Management:

Are you concerned about retinopathy of prematurity (ROP) in this patient?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 4

• Narrow River 23:06*
• (Could demonstrate more knowledge by going into what you would do…)*

I am concerned given this neonate’s high number of risk factors for developing ROP, such as –

• prematurity (especially < 32 weeks gestation),
• low birth weight (under 1500 grams),
• cyanotic congenital heart disease,
• mechanical ventilation,
• respiratory distress,
• hypoxia, and
• acidosis.

Therefore, I would be careful to maintain an oxygen saturation of 87-94% (or a PaO2 of about 50-80 mmHg) and avoid anemia, acidosis, hypotension, and major fluctuations in oxygen or carbon dioxide levels.

Question 5

Intra-Operative Management:

What are the risk factors for ROP?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 5

• Wide River – discussed in 21:08. (26:09)*
• Not expected to verbalize Entire list.*

The etiology of ROP is multifactorial with risk factors including:

1. hyperoxia,
2. prematurity (probably the most important risk factor; especially < 32 weeks and a birth weight of < 1000 g),
3. carbon dioxide fluctuations,
4. hypotension,
5. sepsis,
6. red blood cell transfusions,
7. cyanotic congenital heart disease,
8. respiratory distress syndrome,
9. intraventricular hemorrhage,
10. corticosteroid therapy,
11. mechanical ventilation,
12. hyperglycemia,
13. maternal diabetes,
14. hypoxemia,
15. fluctuations in oxygen levels,
16. exposure to bright light, and
17. maternal antihistamine use within 2 weeks of delivery.

While hyperoxia has long been considered a major component of this neonatal disorder, ROP has been documented to occur in the absence of oxygen supplementation.

Moreover, major fluctuations in oxygen saturation may be a greater risk factor for ROP than hyperoxia.

Question 6

Intra-Operative Management:

Are you concerned about minimizing FiO2 in this sick infant with a heart that is volume overloaded?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 6

• Narrow River - 28:24*
• (31:17 – Additional info that might prove useful to know – Xtra Q: What about ventilation strategy? – see online UBP for info.)*
• (33:00 – Xtra Q/Alternative Q – “Would you reduce the Fio2?” - use 4 critical components. – the way they ask the question can alter your approach in answering….)*
• —*

I am concerned about compromising oxygen delivery to the heart of this infant, and the benefits and risks of reducing his oxygen saturation would have to be considered before taking any action.

However, reducing the PaO2 to 50-80 mmHg is unlikely to compromise oxygen delivery to the heart if anemia is avoided and oxygen consumption is minimized.

Moreover, lowering oxygen saturation may serve to reduce the work of the heart by increasing hypoxic pulmonary vasoconstriction in the lungs and subsequently leading to a reduction of the left to right shunt that is causing pulmonary vascular congestion and volume overload of the heart.

However, I would not allow concerns about causing retinopathy of prematurity to prevent me from increasing the inspired oxygen concentration if I believed it necessary due to the neonate’s cardiopulmonary status.

Question 7

Intra-Operative Management:

How would you maintain anesthesia for this case?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 7

• Narrow River – 34:35*
• Don’t get hung up on type of question… just helps you gauge how much time to answer.*
• 37:30 – Xtra Info – Induction strategy for ligation of PDA. – Great Discussion.*

I would prefer to maintain anesthesia with fentanyl, supplementing with nitrous oxide or ketamine, as necessary.

Since the infant is not likely to be extubated at the end of the case, I would select pancuronium for muscle relaxation as the mild tachycardia it induces may be beneficial in maintaining the infant’s blood pressure.

The decrease in systemic vascular resistance that accompanies the use of volatile agents may prove beneficial by reducing left-to-right shunting through the PDA.

However, these often sick and hypovolemic infants may not tolerate their use since they are particularly sensitive to the cardiovascular depression associated with volatile agents.

Question 8

Intra-Operative Management:

How would you monitor blood loss?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 8

• Narrow River – 40:34*
• Size of Baby is important.*

–

Blood loss must be monitored very carefully because this neonate’s entire blood volume is only about 98 mL (100 mL/kg).

Therefore, I would weigh all sponges, laps, etc. to estimate blood loss as precisely as possible and replace with crystalloid (3:1 ratio), colloid, or packed red blood cells as indicated.

Due to the risks associated with transfusion, I would normally avoid the administration of blood products in a healthy full term infant until the hematocrit was below 20-25%.

However, for this sick premature neonate, with decreased cardiac reserve (i.e. PDA, left atrial enlargement, and abnormal blood flow in the pulmonary artery) and leftward shifting of the oxyhemoglobin dissociation curve (high concentration of fetal hemoglobin), I would prefer to maintain a hematocrit between 30-40%.

Clinical Note:

• Some authors recommend replacing blood loss at 125-150% (over-transfusion) of measured loss due to the difficulty of accurately measuring blood loss in a situation where the margin of error is so small.
• (43:37) – additional useful info – see online too. Great discussion.

Question 9

Intra-Operative Management:

How would you establish your maximal allowable blood loss?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 9

Fairly Narrow River – 46:40

While the optimal transfusion point for extremely low birth weight infants ( < 1000 grams) remains controversial,

I would take into consideration –

• the presence of residual fetal hemoglobin
  
  • (increased affinity for oxygen – shifting the oxyhemoglobin dissociation curve to the left),
• increased oxygen consumption in the neonate,
• the presence of decreased cardiopulmonary reserve
  
  • (i.e. severe pulmonary disease, cyanotic congenital heart disease, and heart failure), and
• the acuity and persistence of blood loss.

Therefore, I would consider transfusion of this sick, extremely low birth weight, premature infant, if his hematocrit dropped below 39%, or even earlier if the neonate became unstable and I felt that an increased hematocrit would be beneficial.

With a starting hematocrit of 49%, this would place my transfusion point at about 20 mL of blood loss.

(calculate this with equations below)

Clinical Notes:

• Estimated Allowable Blood Loss = EBV x (Hi - Hf) / Hi
  
  • Hf = Final Lowest Acceptable Hematocrit
  • Hi = Initial Hematocrit
• EBV = Estimated Blood Volume = Weight (kg) x Average Blood Volume
• Average Blood Volume:
  
  • Premature Neonates = 90-100 mL/kg
  • Pregnant Women = 90 mL/kg
  • Full Term Neonates = 80-90 mL/kg
  • Child 3-12 months of age = 70-80 mL/kg
  • Child > 1 year = 70-75 mL/kg
  • Obese Child = 60-65 mL/kg
  • Adult Men = 75 mL/kg
  • Adult Women = 65 mL/kg

Xtra / Alternative Q:

• “What is the average blood volume in a premature neonate?”
• “How does the percent of fetal hemoglobin affect oxygenation?”

Question 10

Intra-Operative Management:

During dissection of the ductus arteriosus, the oxygen saturation drops from 90% to 78% and the heart rate drops from 150 to 86 beats/minute.

What are you going to do?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 10

Wide River – 51:32

I would –

• manually ventilate the patient with 100% oxygen,
• verify the accuracy of the monitors, and
• evaluate the neonate’s ECG, airway pressures, and tidal volumes.

Since surgical retraction of the lung during dissection of the ductus arteriosus can lead to increased right-to-left intra-pulmonary shunting (compression-induced increases in pulmonary vascular resistance could also potentially lead to right-to-left extra-pulmonary shunting through the PDA), hypoxia (secondary to right-to-left shunting), and bradycardia (probably due to hypoxemia), I would – ask the surgeon to relax any traction on the lung until the patient is stabilized.

At the same time, I would be assessing the patient’s blood loss and volume status to determine if any correction was required.

If the bradycardia persisted, I would consider administering atropine (0.01-0.02 mg/kg).

Finally, I would adjust the inspiratory pressures and inspired oxygen concentration to ensure optimal ventilation and oxygenation.

• 53:12 = Teaching Point = see online.*
• Xtra Q (53:52) – “Why would retraction on the lung lead to these findings?” - Great discussion.*

Question 11

Post-Operative Management:

The child’s blood pressure is elevated post-operatively.

What do you think may be going on?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 11

Wide River

While ligation of the ductus arteriosus is often associated with post-operative systemic hypertension

(the mean arterial pressure and diastolic pressure increase due to the elimination of pulmonary runoff during diastole),

I would also consider other potential causes, such as –

• inaccurate measurement (i.e. an undersized blood pressure cuff),
• inadequate pain control,
• agitation,
• hypervolemia,
• hypercarbia,
• hypoxemia,
• bladder distention, and
• the administration of exogenous medications.

Other less likely causes would include –

• undiagnosed coarctation of the aorta and increased intracranial pressure (there is a higher risk of intracranial bleed in this extremely low birth weight, premature neonate).

• Anticipate likely follow-up question of a differential question or “what do you think is going on?” –>*
• Xtra Q: “What are you going to do?” (3:30 – Commentary on post-op)*

If his hypertension did not resolve after providing sufficient pain control, draining the bladder, and ensuring adequate oxygenation and ventilation, I would – consider administrating an antihypertensive medication, such as – nitroprusside (other choices may include – hydralazine, B-blockers, calcium channel blockers, and alpha-adrenergic blockers).

Question 12

Post-Operative Management:

What does “neutral temperature” mean as it relates to the neonate?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 12

Narrow River – 3:56

The neutral temperature is the ambient temperature at which oxygen consumption is minimized.

Avoiding the compensatory responses to hypothermia, such as –

increased oxygen utilization, increased glucose consumption, and the resultant acidosis, is extremely important in sick (premature) infants.

The neutral temperature is about

• 34 °C for a preterm neonate,
• 32 °C for a term neonate, and
• 28 °C for adults.

Question 13

Post-Operative Management:

How do infants maintain heat?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 13

Narrow River – 6:42

The primary mechanism of heat generation in the infant is nonshivering thermogenesis.

Hypothermia-induced release of norepinephrine initiates the metabolism of brown adipose tissue, which results in increased oxygen consumption and heat production.

Unfortunately, this already inefficient process is severely limited in premature and sick infants who are deficient in brown fat stores.

Therefore, it is especially important to take the necessary steps to maintain normothermia in premature infants during the perioperative period.

Question 14

Post-Operative Management:

How will you maintain normothermia in this infant?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 14

Wide River – 8:41

Assuming the case was going to be performed in the OR,

I would maintain normothermia by –

• ensuring the ambient temperature in the OR was 26-30 °C and by
• utilizing infrared heating lamps,
• forced air warmers,
• warmed intravenous solutions, and
• heated and humidified anesthetic gases.

I would also use a heated transport incubator for transport to and from the OR.

Question 15

Post-Operative Management:

The post-op nurse grabs you as you are leaving the NICU and says she thinks the infant is having a seizure.

What is your differential for neonatal seizure?

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 15

Wide River – 9:40

The differential for neonatal seizure is extensive and includes –

1. intracranial hemorrhage (a relatively higher risk in this extremely premature neonate),
2. hypoxic-ischemic encephalopathy,
3. cerebral edema,
4. hypoglycemia,
5. hypocalcemia,
6. hypomagnesemia,
7. benign seizures,
8. obstetric history of TORCH (toxoplasmosis, rubella, cytomegalovirus, herpes), and
9. sepsis.

Question 16

Post-Operative Management:

What will you do?

(post-op nurse thinks the infant is having a seizure)

• (A 5-day-old infant weighing 980 grams and born at 28 weeks gestation is scheduled for ligation of a patent ductus arteriosus (PDA).*
• HPI: After delivery, the infant was intubated while still in the operating room secondary to respiratory distress. On day four his respiratory condition deteriorated further with worsening hypoxia and increased CO2 retention. Auscultation of the chest revealed a systolic murmur, and a PDA was confirmed with echocardiography. Medical management failed to resolve the condition and the decision was made to surgically ligate the PDA.*
• Meds: indomethacin*
• PE: VS: HR = 158; BP = 60/38 mmHg*
• CV: Tachycardia with a crescendo/decrescendo systolic murmur that extends into diastole. Widened pulse pressure.*
• Lungs: Bilateral rales; ETT in place with pressure controlled ventilation*
• Lab: ABG: pH 7.31; PaCO2 51 mmHg; PaO2 58 mmHg on Fio2 of 50%; H/H 16.1/49; urine specific gravity of 1.010; 1+ glucosuria*
• Echo: Left atrial enlargement; abnormal flow in pulmonary artery)*

Answer 16

Wide River – 11:02

I would immediately:

1. check endotracheal tube placement,
2. auscultate the chest, and
3. review the monitors and ventilator settings to verify adequate ventilation and oxygenation.
4. I would then – check the ECG and blood pressure to assess cardiovascular stability;
5. administer a small amount of barbiturate or benzodiazepine to stop the seizure;
6. order electrolytes;
7. notify the neonatologist; and
8. consider consulting a neurologist.