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Continuous Veno-venous Hemofiltration

Continuous Veno-venous Hemofiltration. R4 周信旭 / VS 邱元佑 93.5.21. CVVH 簡介. CVVH 是以連續的血液過濾再加上適當的液體補充。 治療過程中對人體的血流動力變化穩定，容易達到水分移除與平衡，連續性去除體內毒性物質（如內毒素）。. 優點. 缺點. 連續性代替腎臟功能. 無法迅速移除毒物及電解質. 血流動力變化穩定. 無法限制抗凝物質. 容易達到水分平衡 ( 移除 ). 需加護護理照護. 患者不需要作養份的限制. 患者無法活動自如. 連續性去除體內強勢毒性物質. CVVH 的特點.

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Continuous Veno-venous Hemofiltration

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  1. Continuous Veno-venous Hemofiltration R4 周信旭/ VS 邱元佑 93.5.21

  2. CVVH 簡介 • CVVH 是以連續的血液過濾再加上適當的液體補充。 • 治療過程中對人體的血流動力變化穩定，容易達到水分移除與平衡，連續性去除體內毒性物質（如內毒素）。

  3. 優點 缺點 連續性代替腎臟功能 無法迅速移除毒物及電解質 血流動力變化穩定 無法限制抗凝物質 容易達到水分平衡(移除) 需加護護理照護 患者不需要作養份的限制 患者無法活動自如 連續性去除體內強勢毒性物質 CVVH的特點

  4. Indications for CVVH • Oliguria/Anuria • Significant organ edema (especially lung) • Severe electrolyte imbalance (Na, K, Ca) • Severe acidemia • Uremic pericarditis • Uremic encephalopathy/neuropathy/myopathy • Drug overdose or intoxication • Life-threatening hyperthermia • Inborn error of metabolism

  5. CVVH(D)之原理 (1) • 超過濾(Ultrafiltration):Filtration across an ultrafiltration membrane is convective, similar to that found in the glomerulus of the kidney. • 影響對流(convective)效應之因素: Clearance factors • Transmembrane pressure • WATER (not solute) permeability of membrane • blood flow rate • 擴散(diffusion):solute molecules are transferred across the membrane in the direction of the lower solute concentration

  6. CVVH(D)之原理 (2) • 血液過濾(Hemofiltration):no dialysate is used • diffusive transport cannot occur • Solute transfer is entirely dependent on convective transport, making hemofiltration relatively inefficient at solute removal • 血液透析(Hemodialysis):diffusive transport • Clearance factors • surface area and unit SOLUTE permeability of membrane • blood flow/dialysis flow • duration of dialysis

  7. 血液過濾膜之特性 血液過濾膜允許小分子通透( less than 100 daltons) (e.g. urea, creatinine, uric acid, sodium, potassium, ionized calcium and almost all drugs not bound to plasma proteins). 所有 CVVH 之血液過濾膜 對albumin 及其他分子量大於 50,000 daltons, 是不通透的 phosphate bicarbonate ionized Ca++ interleukin-6 endotoxin vancomycin heparin pesticides ammonia  albumin   protein-bound medications   platelets 

  8. CVVH的技術 • 幫浦：可區分為靠動靜脈壓力差推動或洗腎機幫浦推動。 • 抗凝劑：包括使用肝素或其他抗凝劑如Citrate於出血傾向的病患。 • 血管通路: CVVHD較CAVHD安全，不會引起動脈阻塞、出血、及栓塞。但是使用CVVHD則要注意是否有空氣跑入，或管路連接脫落導致大量出血。 • 透析器：一般使用高透量的短型人工腎臟，當然傳統的人工腎臟透析器也可使用。 • 補充液及透析液：可以使用一般腹膜透析的含1.5%葡萄糖透析液，或CAVHD專用補充液；或自己泡製。

  9. CVVH Order (1) • Check baselines ACT, PT, APTT, bleeding time • Heparin infusion: titrating to keep ACT: 1.5 ~ 2.0X or 200 ~ 300 sec (Normal: 100 sec) • Blood flow rate: ml/min • Replacement fluid: LR or Two-bag formulation: • Solution A: 1L 0.9% N/S + 15ml Ca-gluconate (7 mEq) • Solution B: 1L 0.45% N/S + 80ml NaHCO3 (67 mEq) (Keep negative balance: ml/min) • Check dialyzer arterial and venous side Hct simultaneously qd

  10. CVVH Order (2) • Check ACXT q1hr initially, if stable, check q2hr  q4hr  q8hr  q12hr • Check filtrate BUN, Cr, Na, K, Ca, P qd Check blood gas, BUN, Cr, Na, K, Ca, P q6hr • Check blood sugar, lactate qd • Check ultratiltrate, urine, and other drainage fluid as total output q1hr • Check oral intake, IVF, and other replacement fluid as total input q1hr • Check total I/Q q1hr • 加溫血環或烤燈於靜脈端 • Ultrafiltrate以磅秤計重量 q8h & prn

  11. Parameters to be specified • Blood flow rate (BFR) • Specify patient’s Hct • Ultrafiltration rate (UFR) • Negative balance • Replacement fluid infusion rate • Heparin infusion rate

  12. Sluggishness • A filtration rate of more than 25 - 30% greatly increases blood viscosity within the circuit, risking clot and malfunction.

  13. Filtration fraction • Filtration fraction (FF): the fraction of plasma water removed by ultrafiltration • FF(%) = (UFR x 100) / QP *QP: filter plasma flow rate (ml/min) *QP = BFR* x (1-Hct) *BFR: blood flow rate

  14. Pre-dilution • Sludging problems are reduced, but the efficiency of ultrafiltration is compromised, as the ultrafiltrate now contains a portion of the replacement fluid.

  15. 尿素清除率(urea clearance) • Curea =  UF urea conc. x UFR x 1.73 BUN pt’s BSA Curea: (ml/min/1.73 m2 BSA) • In CVVH, ultrafiltrate urea concentration and BUN are the same, canceling out of the equation, which becomes: • Curea = UFR x 1.73 pt’s BSA

  16. 尿素清除率(urea clearance) • CVVH clearance 的目標設定在至少 15 ml/min/1.73 m2 • 當將尿素清除率(Curea)設定在 15 ml/min/1.73 m2, 而病人之體表面積(BSA) = 1 , 所獲得之UFR: 15 = UFR x 1.73 / pt’s BSA(=1) • UFR = 15 / 1.73 = 8.7 ml/min(520 ml/hr). • 因此對於一體表面積1.73 m2之青少年所需之超過濾率約 UFR = 900 ml/hr.

  17. Blood flow rate & Clearance • 若孩子的 body surface area = 1.0 m2, BFR = 100 ml/min and FF = 30%, 則由前面公式 Curea = 36.3 ml/min/1.73 m2 (約正常腎臟小分子清除率之 1/3). *FF(%) = (UFR x 100) / QP • 過高的血流速度,可能增加CVVH 循環中之溶血效應.

  18. 體液平衡(Fluid balance) Filtration Replacement Fluid (FRF) = Total fluid out – Total fluid in - Desired 例如: 前一小時引流出 300 CC 前一小時所有灌入量 180 CC 欲達成每一小時 negative 20 CC FRF = 300 – 180 – 20 =100 CC

  19. Parameters to be specified (1) • Blood flow rate (BFR) • General rule: Infant: 50 ml/hr; child: 100 ml/hr; adolescent: 150 ml/hr • Specify patient’s Hct • Ultrafiltration rate (UFR) • Upper limit: FF(30%) = UFR/Qp • Lower limit: Urea clearance (15 ml/min) = UFRx1.73/BSA

  20. Parameters to be specified (2) • Negative balance: < BWx5% per day • Replacement fluid infusion rate • Heparin infusion rate: loading 5-20 U/kg; maintain 5-20 U/kg/hr

  21. 注意事項 • By pass 血量 > 8 ml/kg or 10% 全身血量  用 blood priming ( BW < 6 kg 都要) • Heparin: 除了看ACT; Hct, PLT是否太高 (AK易clot); PLT < 50000不用Heparin, prematurity不用Heparin, 以免ICH, 代以30分鐘沖水一次 • UF rate: 勿 > 10 ml/kg/hr, 以免血壓下降 • UF rate/Blood flow < 25-30%, 以免AK clot • Heparin儘量由CVVH機器上的heparin pump給予 (在血液尚未進入透析器之前), Heparin pump 的 control range: 1~10 ml/hr (只能調整數值)

  22. CVVH常見狀況及處置方法

  23. CVVH 的併發症 • 出血 • 透析器凝固 • 失溫 • 低血壓 • 電解質不平衡 • 通路脫落或阻塞 • 感染

  24. 人工腎臟凝固 • 發現方法: (1) 測靜脈壓腔室有fibrin (2) 沖N/S時發現人工腎臟有大量暗紅血絲 (3) 靜脈壓升高

  25. 透析器凝固的早期徵兆 • 通常如果透析液中的BUN比血液中BUN濃度小於0.6，則透析器可能在3-4小時後凝固。 • 另外如果突然人工腎臟的超過瀘率(Ultrafiltration)突然連續三個小時下降，可能表示透析器即將凝固。 • 定期每小時沖洗透析器時檢查; 若預期透析器凝固的可能性高, 增加沖洗頻率 (30 ~ 40 min)

  26. 靜脈壓突然上升不降

  27. 血液流速不足 • 發現方法: (1) 動脈腔室跳動 (2) 動脈管路被pump抽扁有空氣

  28. 濾出液不足

  29. 結語 • CVVH 對於 ARF 和 Multiple organs failure 病人是一種安全,有效的支持性療法 • 對於水份,電解質平衡的處理很有效,可移除代謝廢物與多重器官衰竭的inflammatory mediators,並可加強nutritional support • 預後大多和 underlying d’z 有關,若 organ failure > 3,則表示 poor prognosis

  30. Thanks for your attention !

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