Vascular Access Emergencies in the Dialysis Patient

The recommended dose of protamine is 1 mg for every 100 U of heparin given during dialysis; protamine should be administered over 10 minutes. Alternatively, a 10- to 20-mg dose of protamine can be given if the amount of heparin administered during HD is unknown. Additionally, the patient’s medication list, as with any ED presentation, should be carefully reviewed as many dialysis patients have comorbidities requiring anticoagulation with potentially reversible agents.

Hemodialysis to Improve Platelet Dysfunction

It is thought that long-term exposure of platelets to the dialysis membrane can lead to chronic platelet activation leading to platelet dysfunction. There is conflicting data regarding the effects of HD on improving bleeding in renal patients. ^9,22,23 Hemodialysis is thought to be beneficial, at least partially, through reversing uremia, thus improving platelet function. ²⁴ Therefore, in the stable bleeding patient who missed a scheduled dialysis, initiating HD in the ED setting could be beneficial. If the vascular access site is deemed unsafe for HD, another access site must be obtained, for example, by placing a temporary central venous catheter that will allow for successful HD.

Desmopressin

Desmopressin acetate has been shown to reduce bleeding time in uremic patients by releasing vWF and factor VIII into plasma, taking effect within 1 hour and lasting 4 to 8 hours. ^25-27 Desmopressin has also been shown to reduce blood loss and bleeding times in patients with platelet dysfunction undergoing cardiac surgery. ²⁸ While the underlying mechanism is unclear, desmopressin acetate is thought to help with platelet adhesion to the endothelial wall.

Alternatively, one study by Soslau et al ²⁹ has suggested that desmopressin may increase serotonin uptake by platelets and increase adenosine triphosphate release, thereby facilitating platelet aggregation. The dosing of desmopressin is 0.2 to 0.3 mcg/kg IV. ³⁰ Adverse effects include facial flushing, mild headache, and transient small decrease in blood pressure (BP) with increase in heart rate. Historically, it was thought that desmopressin could lead to water retention, volume overload, congestive heart failure, and hyponatremia; however, these adverse effects have not been seen in uremic patients. ³⁰ Tachyphylaxis may occur after just a few doses of desmopressin are given. ³¹ Additionally, hyponatremia and seizures have been seen after repeated administration in children. ³¹

Anemia and Low Hematocrit

As mentioned earlier, anemia and low hematocrit (HCT) may actually exacerbate bleeding tendencies by decreasing the number of platelets exposed to the vessel wall. Red blood cells (RBCs) also produce TXA2 and ADP, both of which play vital roles in normal platelet aggregation. Secondly, RBCs have been shown to increase NO uptake. Nitric oxide is a potent vasodilator and inhibitor of platelet aggregation. The degree of uptake appears to be augmented by increasing HCT levels. ³² A goal HCT of greater than 30% has been suggested and demonstrated benefit. ³³

Cryoprecipitate

Cryoprecipitate is rich in fibrinogen and vWF. Its mechanism is thought to be secondary to increasing functional vWF levels and possibly fibrinogen levels. While the overall effects appear to be variable, studies suggest 10 U of cryoprecipitate is adequate to reverse significant bleeding with resolution of effect at 24 hours. ^34,35 Given the risks of adverse reactions, variable responses, and risks of hepatitis C and HIV transmission, this therapy must be used cautiously with risk-benefit analysis.