Anasthesia during cpb

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Anasthesia during cpb

  1. 1. Anesthetic Management During Cardiopulmonary Bypass Dr.N.Kanagarajan
  2. 2. Preparations for Cardiopulmonary Bypass  CPB CIRCUIT  Function  Oxygenation and Carbon dioxide elimination  Circulation of blood  Systemic Cooling  Diversion of blood from the heart to provide a bloodless surgical field
  3. 3.  CIRCUIT DESIGN  Venous circuit  Venous blood drained by gravity from the right side of the heart into the reservoir  Most commonly single venous cannulation followed.  Arterial Cannula  Returns oxygenated blood from pump to aorta  Usually placed in ascending aorta/ femoral artery
  4. 4.  Total CPB  When all venous blood draining toward the heart is diverted into the pump oxygenator.  Partial CPB  When only a portion of systemic venous blood drains to the pump oxygenator while passes through the right heart and lungs and ejected by the left ventricle.
  5. 5. Anesthesiologist Pre Bypass Check List
  6. 6.  Anticoagulation  Generally adequate heparinisation requires a activated coagulation time > 480 seconds.  ACT accurately measured within two minutes of heparin administration.  Anesthesia  Concentration of drugs in the blood diluted by the prime  Supplemental medication necessary  Neuromuscular blockers  Anesthesia,Analgesics and Amnesics
  7. 7.  Cannulations  Aortic cannula  Position within the lumen of the aorta should be checked  Aortic pressure should be pulsatile and correlate with radial artery pressure  Check Carotid pulsation  Drips  IV lines closed on heparinisation to prevent further hemodilution.
  8. 8.  Monitoring  Check the zero and calibration of the arterial pressure transducer.  Insert nasopharyngeal temp. probe prior to heparinisation  Foley’s catheter to check urine output.
  9. 9. Maintenance Of Bypass  Anticoagulation  ACT > 480 seconds  ACT checked every 30-60 mins  Perfusion pressure on CPB  Lower flow and pressure during CPB may optimise revascularisation while higher flow and pressure may minimise patient complication.  Cerebral Autoregulation: Mean ABP of 50-150mm Hg.  Higher perfusion pressure needed in severe atheromatous states,advanced age, systemic hypertension and diabetes
  10. 10.  Pump flow on CPB  Careful balance between surgical visualization and adequate oxygen delivery must be maintained  1-2 L/min/m2 perfuses most of the microcirculation when Hct is 22% and hypothermic CPB is used.  Mixed Venous saturation is 70%  Blood gas and acid base status  Should be checked soon after intitiation of CPB  Every 30-60 min  Arterial oxygenation maintained at 100 - 300mm Hg
  11. 11.  Alpha Stat Vs. pH Stat  Alpha Stat Uncorrected (37°C) pH is kept at 7.40 with PCO2 at 40 mm Hg creating a relative alkalosis at the patient arterial body temperature.
  12. 12.  pH Stat  Maintains a pH of 7.40 and PCO2 of 40 mm Hg when corrected for body temperature, typically requiring the addition of CO2 during hypothermic CPB.  Potent vasodilatory effect  increased cerebral blood flow.  May be advantageous in paediatric patients
  13. 13.  Anesthetic Depth  Should be sufficient to  Suppress hypertensive or tachycardic responses to surgical stimuli  Prevent awareness  Prevent unconsciousness movement and respiration  because hypothermia reduces the anesthetic requirement they are most commonly used during the rewarming periods.
  14. 14.  Ventilation  Should cease during total CPB  During partial Bypass occasional ventilation wth 100% O2 may be needed.  Urine production  Sign of renal perfusion  As a guide for fluid management  >1ml/kg/hr should be maintained
  15. 15.  Fluid management  Hemodilution  Lowers the blood viscosity counteracting the deleterious viscosity changes caused by hypothermia  Organ blood flow improved  Optimal hematocrit > 20  Usually a clear priming(non-blood containing) solution is utilised.  Fluid replacement during CPB  Based on Hb, < 5g/dl – Blood, otherwise usually colloids used
  16. 16.  Ultrafiltration  If adequate diuresis cannot be produced an ultrafiltration device added to CPB circuit t remove excess water.  Heparin may be removed during ultrafiltration, so anticoagulation must be monitored frequently.
  17. 17. Weaning from CPB
  18. 18.  Temperature  Systemic hypothermia is widely used during CPB,therefore patient must be rewarmed  Core temp (nasopharnygeal / tympanic/bladder) > 36°C prior to terminating CPB.  Order of rewarming: Vessel Rich> Muscle> Fat  Excessive perfusate heating not advisable  Denaturation of plasma proteins  Cerebral hyperthermia  Air embolism  Rewarming may be enhanced  By increasing blood flow  Use of arterial vasodilators(SNP)
  19. 19.  Analysis and correlation of electrolyte , Acid base balance and Oxygen transport status  Acid base status must be optimised  Acidosis  Myocardial depressant  Increased Pulmonary hypertension  Metabolic acidosis due to inadequate tissue perfusion  Inadequate perfusion flow  A low hemoglobin level  Inadequate oxygenation of blood
  20. 20.  Other causes  DKA  Renal Failure  NaHCO3 can be used to treat the primary cause  Serum K+ >4.0 meq/l to reduce the incidence f arrhythmia  Ca2 + - to treat hypocalcemia and hyperkalemia  Dose- 5-15 ml/kg, can cause coronary spasm, augmentation of reperfusion injury
  21. 21.  Hematocrit  Must be adequate to provide oxyge carrying capacity  HCt > 20% or greater is appropriate for termination of bypass.  Coagulation  Additional heparin may be needed because rewarming accelerates heparin a metabolism  Blood products should be readily available to use if needed(Platelets /FFP / fibrinogen)  Blood products can be used after termination of CPB
  22. 22.  Re-establish adequate ventilation  Once ventricular ejection(pulsatile arterial waveform) is seen, ventilation is started (4 - 6 breaths/min)  Also help to eliminate air from the pulmonary veins  Adequate oxygenation and ventilation amust be nesured while pt is on CPB.
  23. 23.  Lungs should be re-expanded with 2-3 sustained breaths(15-20 seconds) with visualisation of bilateral lung expansion and resolution of atelectasis  tracheal suction done  Prevent LIMA graft damage caused by lung overdistension.  Inspired oxygen fraction should be 1.0
  24. 24.  Predictors  Preoperative EF>40%  Ongoing ischemia/Infarct in the pre-CPB period  Prolonged CPB duration  Inadequate Surgical Repair  Incomplete coronary revascularisation  Residual valvular regurgitation.  Incomplete Myocardial Preservation  Incomplete diastolic arrest  Incomplete Cardioplegia
  25. 25.  Other Drugs / Infusions  Volume expanders  Vasopressors and inotropes  Vasodilators  Anesthetic State  Because of the potential for hemodynamic instability during and shortly after weaning from CPB, it is better to avoid additional anesthetic adminstration.  Supplemental medications are best given during rewarming
  26. 26.  Post ACC removal  Atleast 10-15 min should elapse after the removal of the ACC before attempting sepertion from CPB.  Myocardial injury and edema are reduced by avoiding myoacrdial perfusion pressures in excess of 60 mm Hg in the first 10-15 mins after reperfusion.  Thereafter sustaining coronary perfusion pressure above above 70 mmHG for the last 5-10 min of CPB improves outcome.
  27. 27. Final Checklist for Terminating CPB  Confirm  Ventilation – lungs ventilated with 100% oxygen.  The patient is sufficiently rewarmed.  Complete de-airing done from heart/ grafts/ great vessels.  Optimal metabolic condition.  All equipment and drugs are ready.
  28. 28. Sequence Of events  Step1: Retarding the venous return to the pump  Slowly the venous line is partially occluded  Blood flow through RV increased - the Heart begins to eject  Preload- the amount of venous line occlusion is adjusted carefully and maintain a certain optimal pre- load(adequate cardiac output).
  29. 29.  Step 2: Lowering pump flow into aorta  Attaining partial bypass  The rise in preload causes the heart to begin to contribute to the cardiac output.  Reduced Pump outflow requirement  The amount of arterial blood returned from the pump to the patient can be reduced  Cardiac function And hemodynamics carefully monitored  Readjusting venous line resistance  To maintain the constant filling resistance.
  30. 30.  Step 3: Terminating Bypass  If the heart is generating adequate systolic pressure (90- 100 mm Hg) at an acceptable preload with a pump flow of 1L/min or less the patient is ready for termination of CPB.  The pump is stopped and both pump cannulas are clamped fully
  31. 31. Immediately After Terminating CPB  Preload  Infusing blood from the pump  In adult patients, volume is infused at 50-100ml increments from the venous pump reservoir to the patient through aortic cannula  Should be watched for air bubbles in aortic cannula  W/F blood pressure/ filling pressures/ heart
  32. 32.  Measuring cardiac function  Cardiac Index > 2.0 L/min/M2  Measuring patient perfusion  Adequate tissue perfusion –ABG/ pH after 5 min after CPB  U/O – normally rise after CPB.  Removing the venous cannulae  Removing the aortic cannula

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