Most people recover from major surgical procedures in a predictable fashion. However, as anyone who manages these patients knows, there are always a few outliers. A negative laparotomy patient who has an ileus for over a week. Hip fracture patients who take forever to get out of bed.

We usually chalk this up to human variability or varying degrees of frailty. But could there be more to it? Could it even be predictable?

A group of anesthesiologists and immunologists at Stanford used a new cell-mapping technique to attempt to correlate immune system signatures in blood during the first hours after operation with recovery time. They used a technique called mass cytometry, which flushes different tagged antibodies through a blood sample. This allowed the investigators to determine which immune cells were present, as well as which signalling molecules were being produced.

Here are the factoids:

• 32 patients undergoing hip replacement surgery were studied at various times up to 6 weeks after the procedure
• Antibodies directed at 21 cell surface proteins and 10 intracellular proteins associated with the immune response
• Recovery from fatigue, pain, and recovery of hip motion were quantified using validated objective scoring tools
• As expected, there was a considerable amount of variability in recovery parameters among the patients
• Activation of CD14+ monocytes accounted for 40-60% of the variability in recovery times observed
• Patients with higher activations were more likely to take at least 3 weeks to recover. Those with low activation recovered more quickly.

Bottom line: This is heady stuff, and it is based on a very small group of patients. However, it does suggest that immune system overdrive may be responsible for more evil: slow recovery from surgery. At some point, it may be possible to predict recovery time from a preop blood test. This would be very helpful to know before surgery, and at some point may allow us to give drugs that blunt these processes and speed up surgical recovery.

Related post:

• Why do we always make our patients NPO?

Reference: Clinical recovery from surgery correlates with single-cell immune signatures. Science Translational Medicine 6(255):255ra131 1-12, 2014.

Seems like a simple, silly question, right? I dare you to figure it out without reading this post!

On occasion, our brain injured trauma patients have sodium issues. You know, cerebral salt wasting. Trying to maintain or regain the normal range, without making any sudden moves can be challenging. There are a lot of tools available to the trauma professional, including:

• Saline
• Hypertonic saline
• Salt tablets
• Fluid restriction
• Some combination thereof

Fun times are had trying to figure out how much extra sodium we are giving with any of the first three items. This is important as you begin to transition from the big guns (hypertonic), to regular saline, and then to oral salt tabs.

Below is a quick and dirty conversion list. I won’t make your heads explode by trying to explain the math involved changing between meq, mg, moles, sodium and sodium chloride.

• The “normal saline” bags we use are actually 0.9% saline (9 gm NaCl per liter)
• Hypertonic saline can be 3% or 5% (30 gm or 50 gm per liter)
• Salt tabs are usually 1 gm each (and yummy)

Therefore, a liter of 0.9% normal saline is the same as 9 salt tabs.

A liter of 3% hypertonic saline is the same as 30 salt tabs. The usual 500cc bag contains 15.

A liter of  5% hypertonic saline is the same as 50 salt tabs. The usual 500cc bag contains 30.

To figure out how many tablets you need to give to match their IV input, calculate the number of liters infused, then do the math! And have fun!