General Surgery

Question 1

Liver Resection:

Considerations

Answer 1

1. Potential for major hemorrhage and hypotension
   
   • Hepatic venous back bleeding a major source of blood loss: keep patient dry until resection complete, then restore volume
2. ICV compression from surgeon’s hands or retractors possible.
3. Type of Vascular Occlusion (inflow +/- outflow):
   
   • Pringle manoeuvre [10% decrease in CI, 40% increase in SVR and BP)
   • Total Vascular Exclusion [Pringle + clamping the infrahepatic IVC above the renal veins and clamping the suprahepatic SVC. Venous return decreases by 50%, SVR increases by 80%, so volume load before to avoid cardiac arrest, and must have good cardiac and renal function to tolerate]
   • Inflow occlusion with with extraparenchymal control of hepatic veins [similar to TVE (Pringle is applied) except does not disrupt caval flow. Full mobilization of liver required to ligate hepatic veins.]
   • Selective Inflow Occlusion [Technically more challenging; done in higher risk pts, for eg. cirrotics. Selective occlusion of portal and hepatic inflow at level of liver hilum. Simultaneous occlusion of major ipsilateral hepatic vein may also be done]
4. Potential for reperfusion injury
5. Potential for pre-op and especially post-op liver dysfunction which can result in:
   
   1. Prolonged effect of medications
   2. Prolonged NMBD if hepatically metabolized or eliminated (eg. Roc, primarily hepatically eliminated)
   3. Coagulopathy
   4. Ascites
   5. Liver failure
   6. Kidney impairment
   • There is some evidence, mostly from liver transplant studies, that N-acetyl cysteine (NAC) may reduce hepatic damage during clamping. The most important thing one can do though is to limit clamp time.
6. During clamping or after major resections, hypoglycemia is a risk
7. High post-op pain:
   
   1. Epidurals have downside of increasing risk of transfusion, and post-op coagulopathy complicated their removal
   2. Consider PCA +/- regional nerve block (TAP)
8. Complications of chemotherapy if resection is for colorectal liver mets
9. Complications: Air Embolism with low CVP

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3397643/

Question 2

Liver Resection:

Anesthetic Goals:

Answer 2

• Blood conservation (tranfusions may be associated with worse post-op outcomes, increased risk of cancer recurrence, generalized immunosuppressive effects):
  
  • Monitor CVP and keep under 5 cmH2O
  • Consider using lasix or mannitor to achieve
• Restore euvolemia intraoperatively after liver resection complete
• Ensure to volume load to CVP of 12 if Total Vascular Exclusion used, immediately prior to cross-clamp

Question 3

Liver Resection:

Pre-Op Assessment/Optimization?

Answer 3

First: Determine/Discuss with the surgeon the extent of the resection; the larger it is, the more potential for blood loss, longer clamp times, and the higher risk of post-op liver dysfunction. Same with if the tumor is located near large vessels.

Hx:

• Exercise tolerance: If <1 flight of stairs b/c of SOB or angina, esp if also has A. Fib, has high risk of peri-op M&M
• Any conditions that increase R-sided pressures in the heart (eg. pulmonic stenosis)? If significant, may need repaired in advance to prevent major blood loss with high venous pressures (eg. PS). Need low venous pressures for this surgery.
• Lung disease? The large abdominal incision increases the risk of post-op ATELECTASIS so severe lung dz can have a major impact on recovery
• Presence of other liver diseases? Increases risk. Child-Pugh scores of B or C shouldn’t get liver rxns b/c the risk of post-op liver failure is so high. Severely fatty liver are also at high risk of liver failure.
• Pre-op chemo? Oxaliplatin-based regiments may have peripheral neuropathies: screen for.

Labs:

• INR/PTT/plts: should be close to normal or else severe coagulopathy post-op may occur
• Liver function tests: transaminases, albumin, bili, ammonia, urea (urea cycle occurs in the liver; ammonia gets transformed into urea)

Question 4

Liver Resection:

Anesthetic Mgmt:

Answer 4

• Options: GA
• Monitoring: Large bore periphera IV, art line, central line for CVP monitoring, foley catheter, temperature monitor
• Equipment:
  
  • Norepinephrine, dobutamine ready.
  • Rapid infuser, fluid warmer
  • At least 4 units of blood in the room (be ready to tranfuse; while running a low CVP, sudden blood loss will result in severe hypovolemia)
• Ventilation: Consider low PEEP, even ZEEP, to reduce intrathoracic pressure, assist venous return and decrease back pressure on the hepatic veins.
• Keep CVP under 5cmH2O
• If surgeon employing TVE, fluid load to a CVP of ~12cmH2O prior to cross-clamping
• Be aware of IVC compression by the surgeons’ hands, packs or retractors, which can drop venous return
• During clamping and after major resection, frequent checking of glucose is important (sometimes D5W background infusion is run) ; unexpected hypoglycemia might be a sign of major liver ischemia, potentially caused by portal venous thrombosis
• Once resection complete, restore euvolemia with IV fluid. Also enables detection of bleeding points.
• Insert and NG to enable early post-op feeding
• Disposition: Most patients can be awoken and extubated at the end of the case. Exceptions: heavy bleeding, too cold, acidotic