Platelet Function During Extracorporeal Membrane Oxygenation in Adult Patients

Abstract

Objective: Hemorrhagic and thromboembolic complications are common during support with extracorporeal membrane oxygenation (ECMO). As platelets play a pivotal role in hemostasis, we aimed to clarify how ECMO support affects platelet function. Methods: We included 33 adult patients undergoing ECMO support at a tertiary ECMO referral center at Aarhus University Hospital, Denmark. Blood samples were collected on the first morning following ECMO initiation, and subsequently every morning until the 7th (±1) day. Platelet aggregation was evaluated by whole blood impedance aggregometry (Multiplate® Analyzer) using adenosine diphosphate (ADPtest), arachidonic acid (ASPItest), and thrombin-receptor-agonist-peptide-6 (TRAPtest) as agonists. A new model was applied, taking platelet count into consideration in interpretation of impedance aggregometry analyses. On the 1st and 3rd day, platelet activation was assessed by flow cytometry (Navios) using collagen-related peptide, ADP, TRAP, and arachidonic acid as agonists. Results: Blood samples from all 33 patients were analyzed on day 1 of ECMO support; 24 patients were still receiving ECMO and analyzed on day 3; 12 patients were analyzed on day 7 (±1). After ECMO initiation, platelet counts decreased significantly (p < 0.002) and remained low during ECMO support. ECMO patients demonstrated significantly reduced platelet aggregation on day 1 compared with healthy controls (all p < 0.001). However, when taking platelet count into consideration, platelet aggregation relative to platelet count did not differ from healthy controls. Flow cytometry analyses demonstrated impaired platelet activation in ECMO patients on day 1 compared with healthy controls (all p < 0.03). No substantial difference was found in platelet activation from day 1 to day 3 on ECMO support. Conclusions: Employing impedance aggregometry and flow cytometry, we found both impaired platelet aggregation and decreased platelet activation on day 1 of ECMO support compared with healthy controls. However, platelet aggregation was not impaired, when interpreted relative to the low platelet counts. Furthermore, levels of bound fibrinogen, on the surface of activated platelets in ECMO patients, were higher than in healthy controls. Together, these findings suggestively oppose that platelets are universally impaired during ECMO support. No marked difference in activation from day 1 to day 3 was seen during ECMO support.

Keywords: blood platelets; extracorporeal life support; extracorporeal membrane oxygenation; platelet activation; platelet aggregation; platelet function tests.

Figures

Figure 1

Platelet counts obtained prior to and during support with extracorporeal membrane oxygenation (ECMO). The bars indicate median and interquartile range. The gray area represents a combined reference interval on platelet count for men and women. An X-mark in the circle indicates that the patient has received platelet concentrate within 24 h prior to blood sampling.

Figure 2

Illustrates the platelets ability to aggregate in response to stimulation by three different agonists. Platelet aggregation was measured during support with extracorporeal membrane oxygenation (ECMO) and compared with healthy controls. Agonists used to stimulate platelet aggregation: (A) ADP, Adenosine diphosphate; (C) AA, arachidonic acid; and (B) TRAP, thrombin receptor activating peptide-6. The bars indicate mean with standard deviation. An X-mark in the circle indicates that the patient has received platelet concentrate within 24 h prior to blood sampling. To illustrate the association between platelet aggregation and platelet count, patients with platelet counts below 50 × 109 /L are marked red. Due to practical reasons, platelet aggregation on day 2 was not measured in 2 patients.

Figure 3

Illustrates the degree of platelet activation in response to stimulation by four different agonists. The degree of activation can be measured as a change in the expression of the activation-dependent platelet surface markers bound-fibrinogen, CD63 and P-selectin on day 1 of support with extracorporeal membrane oxygenation (ECMO). The results are compared with healthy controls, n = 33. (A–C) The percentage of activated platelets in response to stimulation by an agonist; (D–F) The median fluorescence intensity (MFI) of the activated platelets following stimulation by an agonist. Agonists used to activate the platelets: COL, Collagen-related peptide; ADP, adenosine diphosphate; TRAP, thrombin receptor activating peptide-6; and AA, arachidonic acid. The bars indicate median and interquartile range.

Figure 4

Illustrates the degree of platelet activation in response to stimulation by four different agonists. The activation can be measured as a change in the expression of the activation-dependent platelet surface markers: Bound-fibrinogen, CD63 and P-selectin. (A–C) The percentage of activated platelets in response to stimulation by an agonist; (D–F) The median fluorescence intensity (MFI) of the activated platelets following stimulation by an agonist. Platelet activation on day 1 of support with extracorporeal membrane oxygenation (ECMO) is compared with platelet activation measured on day 3 of ECMO support, n = 24. Patients weaned from ECMO support prior to day 3 were excluded from this analysis on the difference between day 1 and 3. Agonists used to stimulate platelet activation: COL, Collagen-related peptide; ADP, adenosine diphosphate; TRAP, thrombin receptor activating peptide-6; and AA, arachidonic acid. The bars indicate median and interquartile range.