Labs

Let’s begin with the patient’s CBC at the time of admission:

What’s what: WBC, white blood cell count; Hb, hemoglobin; MCV, mean cell volume; MCHC, mean cellular hemoglobin concentration; RDW-SD, red cell distribution width-standard deviation; platelets, PLT; Normal values: WBC 5-10 x 10⁹/L, RBC 4-6 x 10¹²/L, Hb 12-16 g/dL, Hct 35-47%, MCV 80-100 fL, MCHC 32-36 g/dL, RDW-SD < 45 fL, platelets (PLT) 150-450 x 10⁹/L

How would you describe the CBC?

Click for Answer

Normocytic anemia

Now let’s jump to day 13 postop when you first see her:

What’s what: WBC, white blood cell count; Hb, hemoglobin; MCV, mean cell volume; MCHC, mean cellular hemoglobin concentration; RDW-SD, red cell distribution width-standard deviation; platelets, PLT; Normal values: WBC 5-10 x 10⁹/L, RBC 4-6 x 10¹²/L, Hb 12-16 g/dL, Hct 35-47%, MCV 80-100 fL, MCHC 32-36 g/dL, RDW-SD < 45%, platelets (PLT) 150-450 x 10⁹/L

How would you describe this latest CBC?

Click for Answer

Normocytic anemia and extreme thrombocytosis

So, the patient has new-onset thrombocytosis occurring in the postop setting.

Trends (time series) in lab values often tell important stories!

… so let’s look at the platelet count trend from day of admission to postop day 13, when you first see her.

The platelet count trend is as follows:

*No CBC was obtained between postop days 4 and 7

We see an initial drop in the platelet count, which is typical for patients undergoing cardiothoracic surgery, followed by a progressive increase towards 1000 x 10⁹/L.

What would you look for in the white cell count and Hb?

We have already established that the thrombocytosis is new, occurring in the post op setting. The platelet count trend is as follows:

*No CBC was obtained between days 4 and 7

We see an initial drop in the platelet count, which is typical for patients undergoing cardiothoracic surgery, followed by a progressive increase towards 1000 x 10⁹/L.

What would you look for in the white cell count and Hb?

1. An increasing white cell count might suggest postoperative infection, which may, in turn, be associated with secondary (reactive) thrombocytosis.
2. A significant drop in Hb might suggest blood loss, which may, in turn, be associated with secondary (reactive) thrombocytosis.

The corresponding white cell count and Hb values are as follows:

What’s what: WBC, white blood cell count; Hb, hemoglobin; MCV, mean cell volume; MCHC, mean cellular hemoglobin concentration; RDW-SD, red cell distribution width-standard deviation; platelets, PLT; Normal values: WBC 5-10 x 10⁹/L, RBC 4-6 x 10¹²/L, Hb 12-16 g/dL, Hct 35-47%, MCV 80-100 fL, MCHC 32-36 g/dL, RDW-SD < 45 fL, platelets (PLT) 150-450 x 10⁹/L

The corresponding white cell count and Hb values are as follows:

What’s what: WBC, white blood cell count; Hb, hemoglobin; MCV, mean cell volume; MCHC, mean cellular hemoglobin concentration; RDW-SD, red cell distribution width-standard deviation; platelets, PLT; Normal values: WBC 5-10 x 10⁹/L, RBC 4-6 x 10¹²/L, Hb 12-16 g/dL, Hct 35-47%, MCV 80-100 fL, MCHC 32-36 g/dL, RDW-SD < 45 fL, platelets (PLT) 150-450 x 10⁹/L

The patient has leukocytosis and anemia, though neither is progressive, and both are consistent with a postoperative effect. The WBC differential would be helpful, since a left shift might point towards an infectious process.

For fun, let’s determine the patient’s “platelet-crit” (the fractional volume of blood that is composed of platelets). We know the platelet count is 1006 x 10⁹/L. What additional value do we need to calculate the platelet-crit?

Mean platelet volume is about 9 fL.

The normal range for the platelet-crit (PCT) is 0.22–0.24%.

When you see the patient, she is 13 days post op. The following history provides more information about her course in hospital before you see her:

What is/are the most likely cause(s) of the patient’s thrombocytosis?