1、 Measurement Renal hypoperfusionAcute renal failureUrinary sodium(mmol/l)40Urine:plasma urea ratio202 48 hours is very good 24 hours is acceptable 12 hours is problematic 24hrs.If patients are on Drotrecogin alpha Xigris and are receiving RRT they rarely need additional heparin to achieve acceptable
2、 filter life.The default position is no heparin whilst on Xigris.Platelet counts inevitably fall when on RRT.They fall further on anticoagulant free RRT c.f.than with the use of heparin.In a patient with thrombocytopenia e.g.from sepsis where one chooses to avoid heparin consideration can be given t
3、o the use of epoprostenol in a bid to prolong filter life and attenuate the anticipated fall in platelets c.f.heparin free RRT.GROUP 1-Patient at moderate risk of bleedingRegard this as the standard option-the typical ITU RRT patient e.g.1 Average 2 or more organ failures 4.Surgery 48 hours ago2 No
4、florid coagulopathy 5.No evidence of active bleeding3 Platelets 50 6.No ureamic complicationsHEPARIN BOLUS DOSEINITIAL HEPARIN INFUSION RATETARGET APTT and ratio20-25 units/kg maximum 3000 units10 units/kg/hr35 45 1.3 1.7GROUP 2-Patients at low risk of bleeding or where standard approach results in
5、poor filter life One may require to gradually escalate to this approach where the standard approach has failed and the risk is judged worthwhile.There will be the rare patient who justifies this approach from the start e.g.primary renal problem,another requirement for formal anticoagulationHEPARIN B
6、OLUS DOSE INITIAL HEPARIN INFUSION RATE TARGET APTT and ratio 50 units/kgmaximum 5000 units 15 units/kg/hr 50-65 1.9 2.4Aim for the lower end of this range at first if escalating from the standard approachGROUP 3-Patient at high risk of bleedingWith problems such as 1.Within 48 hours of surgery4.Pla
7、telets 25.Recent active bleeding3.APTT 506.Urea 45 or ureamic complicationGenerally it is worth trying anticoagulant free RRT in the first instance GROUP 3-Patient at high risk of bleeding If filter life is thereafter judged unacceptable and/or the risk considered worthwhile then starting heparin or
8、 epoprostenol as below is reasonable.If thrombocytopenia is a particular problem then perhaps Flolan should be the initial choice greater platelet sparing.If filter life is poor on either of these strategies then the use of them in conjunction may be worthwhile,alternatively it may be judged necessa
9、ry to escalate to the standard approach above.Epoprostenol Flolan target infusion rate 5nanograms/kg/min Start infusion at 2 nanograms/kg/min,increase the rate by 1nanogram/kg/min every 5 10 minutes until the target infusion rate is achieved.The patient should be primed with Flolan for 15 30 minutes
10、 prior to connecting the circuit.It is most practical to infuse Flolan directly into the patient.Although the dose of Flolan reaching the patient is reduced if it is infused directly into the circuit pre filter.Many units use higher target rates but the evidence base is not excessive for this practi
11、ceGuidelines for heparin dose alteration Remember the variable half-life of heparin and the exponential rise in APTT that can occur if excessive upward increments are employed.It is better to err on the side of caution and have a clotted filter rather than a bleeding patient.6 hours after an overgen
12、erous bolus dose steady state may not have been reached and an elevated APTT may reflect too large a bolus dose rather than excessive infusion rates Alteration in heparin infusion rateAPTT target Increase rate by 10 20%.This often translates into an increase of 100 200 units/hr APTT higher than targ
13、et by 30 seconds higher than target Stop infusion for at least 60 minutes&recheck APTT.When it is judged safe to restart the infusion the rate should be at least 20%lower than before Renal Replacement Therapy Key PointsContinuous renal replacement therapies(CRRT)have emerged as the defacto method in
14、 critical care.CRRT ensures adequate creatinine clearance in a hemodynamically stable environment.CRRT is superior to intermittent hemodialysis for volume control.Hemodynamic stability may have the added advantage of preventing secondary ischemic injury to the kidneys due to hypotensive episodes dur
15、ing hemodialysis.The biggest single problem encountered with continuous hemodiafiltration is the necessity for anticoagulation in patients who are,invariably,coagulopathic or bleeding.Care must be taken to ensure electrolyte balance,ideally the content of the dialysate should mirror that of the idea
16、l blood electrolyte composition.Due to the tendency for bicarbonate to caused precipitation,it is usually replaced by lactate in dialysis solutions.However,if the patient is in a state of liver failure,this lactate may not be metabolized,and may cause an academia.Hemofiltration may have a role in the management of septic patients,as a plasma cytokine filter,modulating the inflammatory response,but there is no evidence that this alters outcomes in humans.
