BNF for Children 2011-2012

BNFC 2011–2012 2.8.1 Parenteral anticoagulants 115tory monitoring of coagulation activity, preferably on adaily basis, involves determination of the activatedpartial thromboplastin time (APTT) (for unfractionatedheparin only) or of the anti-Factor Xa concentration (forlow molecular weight heparins). Local guidelines onrecommended APTT for neonates and children shouldbe followed; monitoring of APTT should be discussedwith a specialist prior to treatment for thrombotic episodesin neonates.Prophylaxis Low-dose unfractionated heparin by subcutaneousinjection is used to prevent thrombotic episodesin ‘high-risk’ patients; laboratory monitoring ofAPTT or anti-Factor Xa concentration is also required inprophylactic regimens in children. Low molecularweight heparins, aspirin (section 2.9), and warfarin(section 2.8.2) can also be used for prophylaxis.Pregnancy Heparins are used for the management ofthromboembolic disease in pregnancy because they donot cross the placenta. Low molecular weight heparinsare preferred because they have a lower risk of osteoporosisand of heparin-induced thrombocytopenia. Lowmolecular weight heparins are eliminated more rapidlyin pregnancy, requiring alteration of the dosage regimenfor drugs such as dalteparin, enoxaparin, and tinzaparin.Treatment should be stopped at the onset of labour andadvice sought from a specialist on continuing therapyafter birth.Extracorporeal circuits Unfractionated heparin isalso used in the maintenance of extracorporeal circuitsin cardiopulmonary bypass and haemodialysis.Haemorrhage If haemorrhage occurs it is usuallysufficient to withdraw unfractionated or low molecularweight heparin, but if rapid reversal of the effects of theheparin is required, protamine sulphate (section 2.8.3) isa specific antidote (but only partially reverses the effectsof low molecular weight heparins).HEPARINCautions see notes above; concomitant use of drugsthat increase risk of bleeding; interactions: Appendix1 (heparin)Heparin-induced thrombocytopenia Clinically importantheparin-induced thrombocytopenia is immune-mediated anddoes not usually develop until after 5–10 days; it can becomplicated by thrombosis. Platelet counts should be measuredjust before treatment with unfractionated or lowmolecular weight heparin, and regular monitoring of plateletcounts is recommended if given for longer than 4 days. Signsof heparin-induced thrombocytopenia include a 50% reductionof platelet count, thrombosis, or skin allergy. If heparininducedthrombocytopenia is strongly suspected or confirmed,the heparin should be stopped and an alternativeanticoagulant, such as danaparoid, should be given. Ensureplatelet counts return to normal range in those who requirewarfarinHyperkalaemia Inhibition of aldosterone secretion byunfractionated or low molecular weight heparin can result inhyperkalaemia; patients with diabetes mellitus, chronic renalfailure, acidosis, raised plasma-potassium concentration, orthose taking potassium-sparing drugs seem to be moresusceptible. The risk appears to increase with duration oftherapy and plasma-potassium concentration should bemeasured in children at risk of hyperkalaemia before startingthe heparin and monitored regularly thereafter, particularly iftreatment is to be continued for longer than 7 daysContra-indications haemophilia and other haemorrhagicdisorders, thrombocytopenia (including historyof heparin-induced thrombocytopenia), recent cerebralhaemorrhage, severe hypertension; peptic ulcer;after major trauma or recent surgery to eye or nervoussystem; acute bacterial endocarditis; spinal orepidural anaesthesia with treatment doses of unfractionatedor low molecular weight heparin; hypersensitivityto unfractionated or low molecular weightheparinHepatic impairment risk of bleeding increased—reduce dose or avoid in severe impairment (includingoesophageal varices)Renal impairment risk of bleeding increased in severeimpairment—dose may need to be reducedPregnancy does not cross the placenta; maternalosteoporosis reported after prolonged use; multidosevials may contain benzyl alcohol—some manufacturersadvise avoid; see also notes aboveBreast-feeding not excreted in milk due to highmolecular weightSide-effects haemorrhage (see notes above), thrombocytopenia(see Cautions); rarely rebound hyperlipidaemiafollowing unfractionated heparin withdrawal,priapism, hyperkalaemia (see Cautions),osteoporosis (risk lower with low molecular weightheparins), alopecia on prolonged use, injection-sitereactions, skin necrosis, and hypersensitivity reactions(including urticaria, angioedema, and anaphylaxis)Licensed use some preparations licensed for use inchildrenIndication and doseMaintenance of neonatal umbilical arterialcatheter. By intravenous infusionNeonate 0.5 units/hourTreatment of thrombotic episodes. By intravenous administrationNeonate initially 75 units/kg (50 units/kg if under35 weeks postmenstrual age) by intravenousinjection, then by continuous intravenous infusion25 units/kg/hour, adjusted according to APTTChild 1 month–1 year initially 75 units/kg byintravenous injection, then by continuous intravenousinfusion 25 units/kg/hour, adjustedaccording to APTTChild 1–18 years initially 75 units/kg by intravenousinjection, then by continuous intravenousinfusion 20 units/kg/hour, adjusted according toAPTT. By subcutaneous injectionChild 1 month–18 years 250 units/kg twice daily,adjusted according to APTTProphylaxis of thrombotic episodes. By subcutaneous injectionChild 1 month–18 years 100 units/kg (max.5000 units) twice daily, adjusted according toAPTTPrevention of clotting in extracorporeal circuitsconsult product literatureMaintenance of cardiac shunts and criticalstents consult local protocol2 Cardiovascular system