Continuous hemofiltration and platelet function in critically ill patients

To evaluate platelet function in patients undergoing continuous pump-driven veno-venous hemofiltration.

Prospective study.

Surgical intensive care unit of a university hospital.

Twenty consecutive, critically ill patients with acute renal failure (serum creatinine concentration > 3.0 mg/dL (> 265 mumol/L), serum urea > 200 mg/dL (> 33 mmol/L), urine output < 20 mL/hr) secondary to sepsis or trauma. A comparable group (n = 20) without renal failure and not undergoing hemofiltration served as a control group.

Continuous pump-driven veno-venous hemofiltration was used in patients with renal insufficiency. Pump flow ranged from 60 to 100 mL/hr.

Platelet function was assessed by a turbidimetric technique using a double-channel aggregometer. Aggregation was induced by adenosine diphosphate (ADP) (2.0 mumol/L), collagen (4 micrograms/mL), epinephrine (25 mumol/L), and saline solution (control). Maximum aggregation was considered to be the maximum increase in light transmission after the addition of the aggregating agents. The maximum gradient of aggregation was considered to be the maximum increase per minute. Measurements were carried out before hemofiltration (baseline values) and during the following 5 days. In the control group, blood samples were taken at corresponding data points. Eight patients undergoing continuous hemofiltration survived during the investigation period; 16 patients in the control group survived. There were no significant differences among the two groups with respect to standard coagulation variables. Maximum platelet aggregation was lower than in normal patients after the addition of all three inductors (ADP, collagen, and epinephrine). In control patients, all aggregation variables remained almost stable during the entire investigation period. In the hemofiltered patients, maximum platelet aggregation was significantly reduced (ADP, decrease of 62 relative % from baseline values; collagen, decrease of 86 relative % from baseline values; epinephrine, decrease of 77 relative % from baseline values). Maximum platelet aggregation was also depressed in these patients (ADP, decrease of 40 relative % from baseline values; collagen, decrease of 88 relative % from baseline values; epinephrine, decrease of 85 relative % from baseline values). When platelet aggregation variables were reduced greater than a decrease of 60 relative % from baseline values (in all induction groups), the mortality rate was 100%.

Continuous pump-driven veno-venous hemofiltration significantly changed platelet aggregability, which became obvious 2 to 3 days after the start of hemofiltration.