Presentation on theme: "CPB & Body Water Changes"— Presentation transcript:
1 CPB & Body Water Changes Seoul National University HospitalDepartment of Thoracic & Cardiovascular Surgery
2 Total Body Water after CPB * Cardiopulmonary bypass inflammatory response Increased capillary permeability rise in total body water in extravascular fluid compartment ( massive edema because of relatively loose areolar tissue in children )1. Interstitial edema in the lungReduced efficiency of gas transferReduced pulmonary compliance2. Myocardial edema in heart ; Poor ventricular function3. Cerebral edema4. Ascites and prolonged ileus5. Renal function prejudiced ; Renal immaturity in neonate
3 Risk Factors for Rise in TBW 1. Low body weight2. Low temperatureLong duration of bypassExtremes of hemodilutionTissue ischemia
4 Pediatric Practice of Hemodilution 1. Background Hypothermia, Metabolic rate, Flow rate, Blood 2. Level of hematocrit 30% : recently 20-24% : majority less than 15% : accepted in some 3. Low hematocrit Fall in the delivery of oxygen Fall in colloid osmotic pressure Exaggerate any existing capillary leak
5 Strategies for Fluid Collection 1. Optimize bypass techniqueFlow rate for temperaturePerfusion pressureEven distribution by vasodilationMinimize circuit volumeBiocompatible circuitryAppropriate pump prime (albumin, buffers)Postoperative diuresisPeritoneal dialysisVarious anti-inflammatory therapiesUltrafiltration
6 Third-space Fluid Collection After CPB, they may continue to third-space fluid for 24 to 36 hours in younger patientsFactors favoring fluid accumulation1. Elevation of CVP2. Reduced cardiac output3. Reduced urine output4. Need for high ventilatory pressures
7 Pre-Bypass Management in Young Consider any patient who requires CPB in the first month of life as a high-risk patientPremedicate with methylprednisolone 10mg/kg IV 8 hours and again 2 hours before surgeryMany centers now administer aprotinin to neonate and infants at the beginning of exposure to CPB to reduce inflammatory response
8 Modifications of DHCAEvidence that continuous, low-flow, hypothermic CPB might lead to excessive post-bypass edema and diminished pulmonary function than deep hypothermic circulatory arrest. In part this may be because of prolonged exposure to CPB.Prebypass treatment with steroids and aprotinin, as well as pre-bypass and pre-DHCA hyperoxygenationAdequate duration of cooling(>20min), as well as higher Hct. during cooling phaseUse of pH-stat blood gas strategy, for high risk patientsLimiting the duration of DHCA by intermittent cerebral perfusion for 1-2 minutes at 15 to 20 minutes intervalsUse of modified ultrafiltrationAttention to postoperative cerebral energetics
9 Management of Fluid Collection Leaving a foramen defect openJudicious use of inotropesLeaving sternum open to prevent excessive increases in pulmonary pressuresSteroids, if given preoperatively and in the immediate post-CPB periodPlacement of PD catheterShort period of ECMO in extremely elevated CVP & persistent fluid accumulation
10 Development of Ultrafiltration * Fluids are passed across porous membranes, and in which aggregates with a molecular mass less than pore size are filtered, because of transmembrane gradient. * In the process of ultrafiltration, no fluid is transfused back as a replacement for the volume of ultrafiltrate removed. When the fluid is transfused to compensate the loss of ultrafiltrate, the process is termed hemofiltration.
11 Principles of Ultrafiltration 1. Transmembrane pressure 2. Blood flow rate 3. Depth of pores (membrane thickness) 4. Number of pores (membrane surface area) 5. Size of pores (membrane composition) 6. Hematocrit of blood
12 Construction of Ultrafilters 1. Structure of filter1) Depth filters2) Screen filters2. Type of ultrafilters1) Paralled plate type2) Hollow fibers as capillary type
13 Ultrafiltration During OHS 1. Conventional ultrafiltrationUsually commenced during rewarming phaseof bypass after temperature has reached 28oc.2. Modified(GOS) ultrafiltrationRate of blood flow( ml/min)Suction to the filtrate part(-100, -125cmH2O)Achieve a hematocrit of 36-42%
14 Adverse Effects of Ultrafiltration 1. Another source of trauma to the bloodminimal changes in the blood, particularly duringthe 1st 15~30 minutes2. Activate the component casacade, &leukopenia3. The ultrafiltrate has been shown toactivate neutrophils.
15 Ultrafiltration of Low Molecular Proteins 1. Molecular weight proteins upto 50 kilodaltonsare removed.2. Pressure drop across filter is about 75mmHg.3. Small molecules or small portion of heparin& aprotinin are ultrafiltrated & concentrated .4. Anesthetics, midazolam & alfentanil plasmalevel are decreased a bit, but they remainhigh enough.
16 Mechanisms of Beneficial Effects of MUF The mechanisms by which use of modifiedultrafiltration (MUF) results in improvedhemodynamics are unknownDecreased tissue edemaReversal of hemodilutionRemove systemic inflammatory mediators & vasoactive substances
17 Potential Clinical Benefits of MUF Improved cardiac functionImproved pulmonary function & resulted in a fall in PVRDecreased bleeding & blood product requirementsDecreased pleural effusions following Fontan operation
18 Beneficial Effects of MUF Reduce accumulation of total body waterDecrease postoperative blood lossDecrease postoperative blood productsIncrease in arterial blood pressureDecrease in PVR with unchanged SVR
19 Factors for Rise in Blood Pressure 1. Increase in viscosity and subsequent increase in systemic vascular resistance 2. Decrease in myocardial edema 3. Elimination of vasodilators or anesthetic agents 4. Filtration of toxic compounds (cytokines, myocardial depressant factor, TNF)
20 Advantages of MUF1. It ultrafilters the patient. 2. Hemoconcentrates the circuit. 3. Returns nearly all the blood to the patient. 4. Keep the circuit primed at all times. 5. Retains option to ultrafilter during bypass. 6. The perfusionist can devote his attention to the procedure.
21 Disadvantages of MUF 1. Delay of approximately 10 minutes 2. Potential for hemodynamic instability3. Creation of an arteriovenous shuntIntercompartmental fluid shiftEntrainment of air from a cannulaObstructive cannula in small aorta
22 Not Using Modified Ultrafiltration 1. Surgeon’s impatience2. Some bad experience3. Increased complexity4. Doubts about cost-effectiveness