Anesthesia for Pediatric Liver Resection

Notes From: http://www.sajaa.co.za/index.php/sajaa/article/download/1249/1341

1% of pediatric malignancies are in liver, third most common intrabdominal following adrenal neuroblastoma and wilms. Hepatoblastoma nad hepatocellular carcinoma most common.

Significant periop m&m, up to 19%, perhaps less now.

Surgical Technique

Surgical resection is aimed at cure, and preop workup should identify structures adjacent to/encased by tumor including portal vein (2/3 of blood supply), hepatic vein and hepatic artery(1/3 of blood supply).

Two phases: pre and post-resection

Transverse abdominal incision, rarely thoracic cavity. First liver is mobilized and displaced to access retrohepatic vena cava –> can cause fall in CO and CVP. Ask surgeon to reposition liver for that to improve 🙂
Next step is isolation of portal vein, bile duct and hepatic artery. Ligation of hepatic veins is most difficult and hazardous –> think massive hemorrhage potential!

Hemodynamic Consequences

Pringle maneuver controls both common hepatic artery and portal vein (via hepatoduodenal ligament) – liver can tolerate 60 mins of occlusion, or 120mins of intermittent occlusion.
-inflow occlusion –> increased SVR up to 40%, decreased CO 10%, decreased MAP 15% in adults. Once unclamped, tend to go to baseline.

Total vascular occlusion: combined portal vessl with supra and infrahepatic IVC clamping. –> 40-60% decrease in Venous return and CO, and up to 80% increase in SVR and 50% HR increase. Unclamping increases CI and reduces SVR.

Anaesthestic Considerations

Pre-op

-hepatic impairment –> higher blood transfusion reqs, longer stay and increased mortality

-neoadjuvant chemo has systemic effects (cisplatin, doxorubicin, vincristine 5FU), in these cases a thorough cardioresp assessment is necessary

Anesthesia Planning I/O

-GETA, RSI for patients with ascites

-Nimbex used as it is metabolized by hoffman degradation

-Iso maintains hepatic oxygen supply via vasodilation of hepatic artery and portal vein, though some studies suggest ischemic preconditioning with Sevo limits p/o liver injury

Monitoring

– A line, large bore IVs

– Central line with CVP monitoring, though diaphragm pressure from retraction, clamping of liver vessels decreases venous return and CVP, and PEEP also impact usefulness of CVP

– monitor for hypoglycemia, especially during occlusion, monitor coags

Hemodynamic management

-Minimize bleeding with low CVP (2-5), aim for euvolemia

-during total hepatic vascular exclusion, aim for higher CVP of 14, concern for reduced renal blood flow, so use of mannitol, lasix and low-dose dopamine have been used to prevent renal injury… ?benefit

-manual test clamp should be done as up to 15% of patients get extremely unstable after clamping, could require venovenous bypass

-Selective hepatic vascular occlusion preferred, but different implications: better for when you cannot lower CVP, such as right heart failure with high CVP, or when tumor encrouches on IVC

Blood: think of using TXA, cell saver, prepare to give PRBCs and products

 

Analgesia

-regional reduces post op pain, caudal or epidural

-caution of NSAIDs 2/2 renal damage from surgery, Tylenol is good in all but most extensive resection

 

Vascular Air Embolism

-right lobe large resections, close to IVC, or cavohepatic junction risks of air embolism

-remember TEE detects as little as 0.02ml/kg and doppler detects 0.05ml/kg

-trendelenberg, fluid resuc and vasopressors

 

PO to ICU, for management of hypoglycemia, respiratory insufficiency, pain, ascites, infection, bleeding, coagulopathy, portal/hepatic thrombosis, renal dx and liver dx

 

 

 

Vasopressors part 1

Part 1 of ___ … on some general notes on vasopressors.

Metabolism

Catecholamine class (epi, levo, dopa, dobutamine, isoproterenol) all metabolized by Catechol-O-methyltransferase (COMT) and MAO. Phenylephrine also metabolized by MAO.

*indirect acting sympathomimetics (phenylephrine) greater risk of hypertensive crisis due to reliance on MAO metabolism, direct acting also metabolized by COMT so less risk, also patients taking TCAs.

Milrinone and ephedrine both excreted unchanged in urine, while Vaso is metabolized by vasopressinases in liver and kidney.

Levosimendan metabolized into active compounds and effects linger for up to 1 week after discontinuing.

Alpha Beta – A Review

Courtesy of https://classconnection.s3.amazonaws.com/729/flashcards/1173729/png/adrenergic_receptors1360695924373.png
Courtesy of https://classconnection.s3.amazonaws.com/729/flashcards/1173729/png/adrenergic_receptors1360695924373.png

 

 

 

Cardiorespiratory Management in Ventilated Neonates

In any patient, there is an interaction between respiratory parameters set by the ventilator and the interaction with cardiovascular function. In neonates, this response is more dramatic due to their small size.

The following are several ways in which Respiratory parameters affect the cardiovascular system:

  1. Mean Airway Pressure: As MAP is increased, there is a decrease in preload (as blood is trapped in the pulmonary vasculature) and decrease in afterload too.
  2. Inspiratory time: In general, as you increase this you also decrease preload.
  3. Mode of ventilation
    1. Pressure mode will give you higher MAP (bp) for lower PIP
    2. Volume mode will lead to lower MAP (bp) for higher PIP
  4. Oxygenation – neonates have reduced free radical system, so key to reduce amount of iO2 if possible. O2>90% permissable. However, higher oxygenation will lead to increased… PAP?
  5. CO2: Permissive hypercapnia acceptable(paCO2<50), unless there is pulmonary HTN.

Inspiratory time compared to expiration:

  • 1st beat: augmented filling of LV
  • 2nd beat: decreased filling slightly below expiration level
  • 3rd beat: significantly decreased preload, resulting decreased CO

PVR also is altered by CO2 of course, but the response in neonates is more dependent on pH. As pH goes from 7.4 to 8.0, alkalinization, the PVR subsequently decreases, while the PVR only gradually increases from pCO2 increases.

PEEP titration is another consideration. PEEP improves oxygenation, but also alters CO. As you increase PEEP, you trap more blood in the pulmonary vasculature, therefore decreasing preload and CO.

Finally, Hemoglobin also

From The Neonatal Lung - Physiology and Ventilation; Neumann et al. Pediatric Anesthesia 2013.
From The Neonatal Lung – Physiology and Ventilation; Neumann et al. Pediatric Anesthesia 2013.