Anaesthesia for CDH.

[KLPM]

Regarding the anaesthesia management of congenital diaphragmatic hernia. I am struggling to understand part of it that I have seen in a few textbooks. If possible rather than getting a straight answer I wouldn't mind someone giving me "hints" to walkthrough.

The main question is regarding the use of volatiles. The sources I have read all seem to say use little or avoid completely volatile agents. I don't really know why that is. The only place that seems to mention anything says "risk of cardiovascular depression" when using inhalation agents. But I thought gases like sevoflurane produced minimal cardiac depression.

Apparently these kids could have bilateral pulmonary hypoplasia and tend to revert to a foetal circulatory pattern with a right-to-left shunt. The physiological problems they may face seem to include inadequate gas exchange surface and high pulmonary vascular resistance with pulmonary hypertension.

Would gas exchange issues make volatiles less appealing? What about the possibility of exacerbating the right-to-left shunting by decreasing SVR using volatiles? What about keeping PVR low by keeping FiO2 high? Am I over-thinking and showing my obvious lack of understanding of physiology/pharmacology/anaesthetics?

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[periopdoc]

Are you certain they said avoid volatile anesthetic agents? Is it possible that there is a different kind of inhaled anesthetic the avoidance of which they were recommending?

- pod

 

[KLPM]

Is it possible that there is a different kind of inhaled anesthetic the avoidance of which they were recommending?

Nitrous oxide?

I know it was specifically stated to avoid nitrous oxide because 1) CDH patients need to be ventilated at high FiO2 and, 2) nitrous oxide could diffuse into visceras thus exacerbating lung compression.

Part of my confusion arises from that some sources say to maintain anaesthesia under low levels of volatiles or opioids and muscle relaxants while others say avoid volatiles all together.

 

[periopdoc]

Yes, I was thinking nitrous for the reasons that you mentioned.

There is a problem with right to left shunt that can be exacerbated by the use of volatile anesthetics. Fairly theoretical IMHO.

Think about a combination of factors that could worsen right to left shunt and how, anatomically, they would do so.

At your request I am trying to be a little vague.

- pod

 

[periopdoc]

Do you think that neuromuscular blockade should or should not be used for this surgery? Are there any areas of the surgery where it would be beneficial? Any areas where it might be a concern?

- pod

 

[HalO'Thane]

Do you think that neuromuscular blockade should or should not be used for this surgery? Are there any areas of the surgery where it would be beneficial? Any areas where it might be a concern?

- pod

NMB would probably be pretty beneficial. Many of these kids are pretty critically ill and being able to supplement your anesthetic with paralysis helps to make a "balanced" anesthetic. Lung compliance is also a problem and the last thing you need is a patient fighting against the vent. Many times I also prepare for a TIVA approach (fentanyl and midaz drips + paralytic bolus') in case I need to use the ICU ventilator or if the patient is sick enough to require an oscillator. Pulmonary Hypertension is also one of the biggest issues in these types of cases and being able to run a more stable "cardiac" type anesthetic helps blunt their sympathetic response.

 

[periopdoc]

I don't think that neuromuscular blockade is part of a "balanced" anesthetic. However, it can certainly be helpful for certain aspects of this case. You touched on the ventilatory aspect which is one key. Another is the ability to reduce your anesthetic requirement (TIVA or inhaled) and thereby minimize cardiac depression. It is also helpful when they reduce the hernia and while they are repairing the diaphragm.

Is there a part of the case where it might not be beneficial?

TIVA can be a good option for these cases, especially if you run into issues with the volatiles or if your anesthesia machine is not an option.

Of course, the whole point of the thread is what kind of issues can you run into with volatile inhaled anesthetics?


- pod

 

[KLPM]

There is a problem with right to left shunt that can be exacerbated by the use of volatile anesthetics. Fairly theoretical IMHO.

Think about a combination of factors that could worsen right to left shunt and how, anatomically, they would do so.

I guess the pulmonary hypertension is a large factor here. So anything that may further increase PVR will worsen the shunting:

- Acidosis
- Hypothermia
- Hypoxia
- High airway pressure

Will being fluid overloaded worsen the shunt? Like if there is too much venous return to the right ventricle?

I am venturing a guess that severe decreases in SVR can also affect increase the right-to-left shunting.

 

[michigangirl]

NMB would probably be pretty beneficial. Many of these kids are pretty critically ill and being able to supplement your anesthetic with paralysis helps to make a "balanced" anesthetic. Lung compliance is also a problem and the last thing you need is a patient fighting against the vent. Many times I also prepare for a TIVA approach (fentanyl and midaz drips + paralytic bolus') in case I need to use the ICU ventilator or if the patient is sick enough to require an oscillator. Pulmonary Hypertension is also one of the biggest issues in these types of cases and being able to run a more stable "cardiac" type anesthetic helps blunt their sympathetic response.

This. There is a large spectrum of CDH. There is the right-sided CDH with very little pulmonary hypoplasia that can be repaired laparascopically, there's the left sided CDH on ECMO due to severe pulmonary hypertension. There's the CDH that didn't end up on ECMO that requires the oscillator and NO for adequate oxygenation.

Other than the indication of not being able to use the anesthesia vent in the OR due to the need for oscillation, there is no reason to avoid volatile anesthetic-- volatiles can have their role as long as they are titrated in a sensible fashion and close attention is paid to the cardiopulmonary interactions that are so unique in this population. A reasonable cohort of these babies will be on Nitric Oxide or pulmonary vasodilation of some form, which must also be considered.

Volatile anesthetic is not a contraindication for a severe Tet, for example, where a drop in SVR could be catastrophic. It is simply a matter of being aware of the possible consequences and using just enough in combination with opioid and NMB to create an ideal physiologic and surgical situation.