Important Considera/ons for Coagula/on Tests on Children and Neonates

Transcription

1 Important Considera/ons for Coagula/on Tests on Children and Neonates Cindy Neunert, MD MSCS Associate Professor Pediatric Hematology/Oncology/Bone Marrow Transplant Columbia University Medical Center

2 ObjecEves Provide an overview of pediatric developmental hemostasis Understand the difficulees in teseng neonates and pediatric paeents Determine best praceces with regards to Eming of teseng and interpretaeon of results

3 Neonatal and Pediatric Hemostasis Rapidly evolving system: Developmental Hemostasis Generally 50% lower than adults at birth Blood sampling is technically difficult 6% of samples demonstrated cloqng Small volumes are drawn 1 ml for coagulaeon screen and 1 ml for each assay Poor normaeve data based on high degree of variability Mostly accounted for by differences in reagents used ISTH recommends that each laboratory set age norms SEll needed for very low birth weight infants, devices, and sick infants Affect by gestaeonal age of infant Pre- term infants will be lower than term infants Williams et al. 2002, Davies et al. 2002, Toulon 2016, Revel- Vilk 2012

4 Case 1: Hemorrhage A 2- day old male infant demonstrates oozing following circumcision and heel seck. Screening laboratory values: PTT of 58 seconds ( sec) PT of 15 seconds ( sec)

5 Neonatal Hemostasis TesEng TraumaEc venipuncture Prolonga(on due to acevaeon of coagulaeon and depleeon of cloqng factors Shortening due to generaeon of small amounts of thrombin Heparin contaminaeon Prolongs the PTT (PT also if concentraeon is high) Difficult to request a peripheral venous lab draw

6 Neonatal Hemostasis TesEng AlteraEon in the citrate- to- plasma raeo Polycythemia and under- filling will prolong extra citrate chelates added Ca 2+ Anemia and over- filling will shorten not enough citrate to prevent inieaeon of coagulaeon Adcock et al 1998, Spaet 1979, Hu eta.2012

7 Natural Hemostasis Natural coagulaeon system development Factors synthesized by the infant and do not cross the placenta Measurable by roughly 10 weeks of age Gradually approach adult levels by 6 months of life Day 1 Day 30 Day 180 Adult PT 13 ( ) 11.8 ( ) 12.3 ( ) 12.4 ( ) INR 1 ( ) 0.79 ( ) 0.88 ( ) 0.89 ( ) PTT 42.9 ( ) 40.4 ( ) 35.5 ( ) 33.5( ) Factors V, VIII, XIII, fibrinogen and VWF are not decreased at birth Can increase aier birth and normalize by approximately 3 months Andrew et al, 1987, 1988

8 Case 1: Hemorrhage Screening laboratory values: PTT of 58 seconds ( sec) PT of 15 seconds ( sec) Factor VIII level: 6% Follow- up teseng should be undertaken at 6 months of age

9 Case 1: Hemorrhage Screening laboratory values: PTT of 58 seconds ( sec) PT of 15 seconds ( sec) Factor IX level: 15% Follow- up teseng should be undertaken at 6 months of age

10 Case 2: Thrombosis A 1 month old infant who is criecally ill from sepsis develops a deep vein thrombosis in locaeon not associated with central line Primary team is requeseng a thrombophilia evaluaeon due to strong family history of thrombosis

11 Natural AnEcoagulaEon Inhibits ( ) XI VIII VIII Thrombin (IIa) Ca++ XIa Ca++ IX IXa Ca++ X Xa V Va Prothrombin (II) Protein S Protein S Protein Ca Thrombin (IIa) Thrombin (IIa) Protein C X Ca++ VII TF VIIa Ca++ Xa Fibrinogen (I) Tissue factor pathway inhibitor (TFPI) An/thrombin Thrombin (IIa) Fibrin Cross- linked fibrin XIII XIIIa Borrowed from Dr. Young

12 Neonatal AnEcoagulaEon System Infants also have impaired and delayed thrombin generaeon Similar to adults on warfarin Relies on different inhibitors Lower levels of AnE- thrombin III

13 Neonatal AnEcoagulaEon System Protein C levels are very low at birth Remain decreased during the first 6 months of life Mostly in the single chain form GlycosylaEon is different in animal models Unknown impact on funceon Protein S Decreased at birth Completely in the free state and funceonally normal Total TFPI is normal but the free level might be reduced

14 Neonatal AnEcoagulaEon System Day 1 Day 30 Day 180 Adult ATIII 0.63 ( ) 0.78 ( ) 1.04 ( ) 1.05 ( ) Protein C 0.35 ( ) 0.43 ( ) 0.59 ( ) 0.96 ( ) Protein S 0.36 ( ) 0.63 ( ) 0.87 ( ) 0.92 ( ) Andrew et al, 1987, 1988

15 Case 2 ConEnued: CriEcal Care Infant requires heparin anecoagulaeon Has evidence of liver and kidney impairment Also has significant hyperbilirubinemia and baseline elevaeon of the PTT

16 AnEcoagulaEon: Heparin Mechanism of AcEon Binds to ATIII (cofactor) Aier binding, increases ATIII Dose requirement affected by Age of paeent ATIII acevity (at least >50-70%) Urine output/renal funceon Platelet and FFP administraeon DIC and Post- cardiac surgery Lot number of product x

17 AnEthrombin III Low ATIII acevity seen in following paeents: Neonates (physiologic) Liver disease Sepsis Inherited deficiency Normal level is 80% acevity Lower than 50% may have difficulty with heparin dose Major risk of AT replacement is bleeding Sepsis studies

18 Monitoring of Heparin PTT: Measurement of intrinsic and common pathway FuncEonal measurement of anecoagulaeon Not as effeceve at very high doses of heparin May be prolonged in response to hemodilueon Affected by factor deficiencies and lupus anecoagulant May not be ideal for infants

19 AnE- Xa AcEvity Gold Standard test Target Level: Not a good point of care test or funceonal test LimitaEons important to neonates Chromogenic assay Influenced icteric, lipemic, and/or hemolyzed samples Bilirubin (10-20 mg/dl) Triglycerides (600-1,250 mg/dl) Can resolve with ultracentrifugaeon Hemoglobin (2mg/mL) in plasma Vera- Aguilera 2016, Kostousov 2014

20 Global Assays: Thromboelastography TEG- R is dependent on formaeon of Factor Xa Point of care test Not available at all centers Further data needed: CorrelaEon with PTT and AnE- Xa Neonatal and pediatric normaeve data Data on specific populaeons Wallskog et al. 2018, Shinoda et al 1990, White et al. 2012

21 Case 3: Primary Hemostasis A 1 week old female infant has a seizure and is found to have a subdural hematoma Screening coagulaeon studies are normal You learn that the parents are first- cousins

22 Primary Hemostasis ConsideraEons Platelet numbers and survival studies are similar between neonates and adults Neonatal platelets are generally hyporeaceve Compensated for by increased vessel wall interaceon via increased VWF levels Normalizes by 2-4 weeks Depends on gestaeonal age

23 Platelet FuncEon TesEng Review medicaeons Indomethacin, ibuprofen, ampicillin Maternal condieons can alter platelet funceon Pregnancy- induced hypertension and diabetes Platelet aggregometry Large volume needed (10mL) Lack of appropriate neonatal normaeve values Reduced clinical applicaeon Flow cytometry for platelet acevaeon µl Minimal sample manipulaeon before analysis High cost, lag Eme in results, lack of neonatal reference ranges, not globally available Del Vecchio et al. 2015)

24 Summary Component Parameter Neonatal period (mean value)* Normalization Net effect on hemostasis Primary Platelets Normal or increased 1 year (after Enhanced primary hemostasis hemostasis transient increases) von Willebrand Increased (153%)* 3 months factor Platelet closure Shortened 2 4 weeks time (PFA-100 â ) Coagulation FII, FVII, FIX, FX Decreased (40 66%)* 1 year (up to 16 year for FVII) Decreased coagulation potential FXI, FXII, PK, HMWK Decreased (37 54%)* 1 year FV Normal or decreased (70%)* 1 year (up to 16 year) FVIII Normal or 1 month increased (100%)* Fibrinogen Decreased ** or normal 1 year PT Prolonged or normal 1 year aptt Prolonged 1 year (up to 16 year) Natural Antithrombin Decreased (63%) 3 months Decreased regulatory/ coagulation Protein C Decreased (35%) 16 years inhibitory potential inhibitors Protein S Decreased (36%)* 3 months Fibrinolysis Plasminogen Decreased (36%)* 6 months Increased fibrinolytic activity Alpha 2 antiplasmin Normal or 6 months decreased (85%)* tpa Increased 1 week D-dimer Increased 16 years

25 Summary The neonatal coagulaeon system is dynamic CoagulaEons studies in neonates and children need to be interpreted in the seqng of age adjusted normaeve values AddiEonal pre- analyecal and comorbid factors may influence the reliability of teseng results CoordinaEon with the coagulaeon laboratory can assist with appropriate planning and improve quality of results

26 The diagnosis of thrombophilia or of a bleeding disorder in neonates should be based on the presence of a posieve clinical phenotype, family history, and of reproducible abnormal laboratory results Revel- Vilk 2012