Dry Lungs?

Fluid in Thoracic Surgery: Time to move overthrow Immortan Joe?
Fluid in Thoracic Surgery: Time to overthrow Immortan Joe?

The Classic Teaching from Miller 8th Edition ch 66 Anesthesia for Thoracic Surgery

Total positive fluid balance in the first 24-hour perioperative period should not exceed 20 mL/kg.

For an average adult patient, crystalloid administration should be limited to less than 3 L in the first 24 hours.

No fluid administration for third-space fluid losses during pulmonary resection.

Urine output greater than 0.5 mL/kg/h is unnecessary.

If increased tissue perfusion is needed postoperatively, it is preferable to use invasive monitoring and inotropes rather than to cause fluid overload.

And so the above was also consistent with the clinical teaching at my institution. Keep them dry, regardless of whether it was a wedge resection, lobectomy or esophagectomy (I haven’t had the pleasure of a pneumonectomy yet).

But further reading in Barash (Clinical Anethesia Fundamentals), calls this into question in ch 34 Anesthesia for Thoracic Surgery, with the following one liner broadside:

“Fluid management for all thoracic procedures should follow either a restricted or a goal-directed protocol. However, recently, concerns about acute kidney injury have called into question the strategy of fluid restriction in thoracic surgery.”

And later in the same chapter, a “Did You Know?” sidebar reinforces the same point, specifically mentioning esophageal surgery and the controversy around restrictive fluid management.

When asked about this in the operating room, the Thoracic Surgery team even indicated that anesthesiologists in this practice are being too restrictive, especially with the esophagectomies (which are for the most part, abdominal surgery).

So what is one to make of this?

Digging into the literature, there was a nice summary of the controversy and recent data at Current Opinion in Anaesthesiology  (doi: 10.1097/ACO.0b013e32835c5cf5) from a team of anesthesiologists at Yale. The article provides a nice run down on the basis of the fluid restrictive strategies (mainly studies from the 198os) and how these studies were performed before the advent of lung protective ventilation strategies (6-8cc/kg and use of peep). They do agree that fluid restriction in Pneumonectomy is logical:

In pneumonectomy, the whole cardiac output will be directed to the remaining lung. This volume in the presence of a decreased vital capacity may overwhelm the remaining lung’s protective mechanisms resulting in a rise in the pulmonary capillary filtration pressure.

However, this may not be the case in lesser lung resections, with a restrictive therapy threatening to cause Acute Kidney Injury. In fact, the belief that renal injury is low in thoracic surgery appears misplaced, as old data only counted kidney injury if patients required renal replacement therapy. Newer evidence shows thoracic patients are at higher risk of AKI than previously thought and that this may cause increased M&M in the longer term.

The authors then go on to promote a Normovolemia and Goal-Directed fluid therapy regiment. One study showed a simple normovolemia method of replacing ongoing losses and use of maintenance fluids i/o and post-op until PO intake, reduced both AKI and extravascular lung water (EVLW). The goal-directed therapy targets Cardiac Index through either Thermodilution, PiCCO, Transesophageal Doppler, SVV or PPV.  The authors point out that while controversy remains, there is some evidence showing no increase in EVLW with goal-directed fluid therapy when lung protective ventilation strategies are used.

The remainder of the article goes into the colloid vs. crystalloid debate, which is beyond the scope of this post, and it appears there is no evidence of which is better to use in thoracic surgery (potential for future research questions!).

So in conclusion, it appears that Dry Lungs may not be the Best Lungs and Best Kidneys for Thoracic Surgery.