204 A . Svec et al .: J Extra Corpor Technol 2024 , 56 , 203 – 206
perfusion was 6.2 L / min at a cardiac index of 2.0 L / min / m 2 . The patient ’ s home medications were metoprolol , empagliflozin , and spironolactone . The patient was allergic to Entresto and bee stings . Due to our patient ’ s larger size , we investigated the patient ’ s lean body mass to verify our oxygenator would support the patient ’ s needs . The calculated lean body mass for the patient was 105 kg . Using this to calculate our BSA we find a BSA of 2.3 m 2 and our calculated indexes to 2.0 : 4.6 L / min , 2.5 : 5.8 L / min , 3.0 : 7.0 L / min verifying that our single oxygenator setup should be able to support the patient .
Before patient induction , the baseline blood gas was pH 7.37 , PCO2 44.5 mmHg , PO2 383 mmHg , bicarbonate 25.5 mmol / L , base �0.1 , oxygen saturation 100 %, hemoglobin 13.9 g / dL , hematocrit 41.5 %, sodium 141 mMol / L , potassium 4.2 mMol / L , calcium 1.13 mMol / L , glucose 97 mg / dL , and lactate 0.7 mg / dL . Baseline ACT 125 at 0755 . The anesthesia team ran a thromboelastogram ( TEG ) at 0755 and the platelet count was 214,000 / mL . The baseline TEG had a max amplitude of 75 mm indicating a borderline hypercoagulable state . A Medtronic Affinity Fusion Oxygenation System was used for perfusion in this case ( Medtronic Inc ., Minneapolis MN ). Our CPB circuit consisted of LivaNova S5 HLM , Quest MPS3ND , Medtronic Affinity Fusion hardshell Venous Reservoir , Medtronic Affinity Fusion Adult Oxygenator , a Medtronic custom tubing pack comprises the remainder of the circuit that is coated with a Balance Biosurface coating . The pump was primed with 1400 mL of Plasmalyte-A , before initiating bypass a retrograde autologous prime was performed leaving only about 900 mL of Plasmalyte-A still in the circuit . To that final circulating volume , 5000 units of heparin and 25 g of 20 % mannitol are added . The Anesthesia team gave 4000 units of heparin . The post-heparin ACT 444 at 0825 . Cardiopulmonary bypass was initiated at 0842 and the patient was cooled for 30 min . The cooling gradient was maintained in the safe range always less than 10 ° C as is standard practice at our center . The patient ’ s starting bladder temp was 36.2 ° C and it was cooled to 29.5 ° C at the time of circ arrest . The revolutions per minute of the pump ( RPM ) were maximized at 3300 , with a measured flow of 6.1 L / min and an arterial resistance of 248 mmHg . The perfusion team was mindful to keep the FIO 2 set to 100 % due to the patient ’ s increased oxygenation requirements . After eight minutes on bypass , a blood gas was drawn to determine adequate oxygenation and lab values ; pH 7.30 , PCO2 50.7 mmHg , PO2 394 mmHg , bicarbonate 24.1 mmol / L , base �1.4 , oxygen saturation 100 %, hemoglobin 11.6 g / dL , hematocrit 35.5 %, sodium 136 mMol / L , potassium 7.5 mMol / L , calcium 1.00 mMol / L , glucose 146 mg / dL , and lactate 1.1 mg / dL . The hyperkalemia was due to running the arterial blood gas immediately after the initial dose of cardioplegia . Cardioplegia was given according to our standard microplegia protocol . Our protocol calls for a 1200 mL blood-based cardioplegia initial dose . Added to the blood by way of a Quest MPS3 was 40 mEq / L of Potassium Chloride and 4 mEq / L of Magnesium Sulfate . At this time , the venous blood return temperature was 31.4 ° C and the radial arterial blood pressure was measured at 65 mmHg . With the RPMs stable at 3500 , the flow had decreased to 3.9 L / min with a post-oxygenator arterial resistance of 153 mmHg , and it was observed that flow to the patient was below the calculated minimal flow . Because RPMs were set to the maximum value , flow could not be increased , and the perfusion team began troubleshooting with the assistance of the surgeon and anesthesiologist . Troubleshooting began with ensuring the centrifugal head was seated properly . To verify proper placement , the position was verified at a point during the aortic repair when the surgeon instructed to decrease flow . The perfusion team decreased the RPMs to 0 RPMs to disengage and reengage the pump head to confirm proper placement . Our circuit features a Medtronic Affinity CP centrifugal pump . After resuming flow to the patient , the flow was 3.9 L / min at 3500 RPMs . The second step in the troubleshooting process was checking to make sure the flow probe was accurately reading . The flow was measured via the LivaNova Sorin S5 built-in flow probe that was placed pre-oxygenator for the most accurate total flow measurements . To quickly verify accurate flow measurement , a Centrimag ( Abbott , Abbott Park , IL ) was brought into the operating room . The team disengaged the flow probe from the cardiopulmonary bypass machine and placed the flow probe from the Centrimag onto the CPB circuit and flows were correlating at 3.9 L / min at 3500 RPMs . The next step was to check the placement of the aortic cannula . Due to a discrepancy of about 20 mmHg in the aortic line pressure and the patient ’ sright radial artery pressure before bypass , it was believed it was in our best interest to check cannula placement . At this time , the line pressures were arterial line resistance 153 mmHg , radial arterial line 70 mmHg , and femoral arterial line 71 mmHg . At this time , the heart was arrested , and the line pressure was laminar flow . The transducers on the CPB circuit were zeroed prior to the start of the case during morning pump checks . We started with readjusting the arterial cannula and checking for an aortic dissection under a transesophageal echocardiogram . After it was determined that the cannula was still in the true lumen of the aorta and there was no new dissection , flows dropped gradually over about 10 – 15 min to 2 L / min . As a final troubleshooting step , the oxygenator purge line was used to check the pre-membrane pressure of the oxygenator . On the Medtronic Affinity Fusion , the purge line is a pre-membrane purge line and therefore could be used to read pre-oxygenator pressure . The purge line was connected directly to the arterial transducer on the CPB pump . With the transducer turned off to the circuit and onto the oxygenator purge line the pressure was reading > 550 mmHg . At this point , the perfusion team decided to change the oxygenator on the circuit to a new Affinity Fusion oxygenator . The oxygenator was primed and changed in the usual fashion without incident with the changeout process was completed in less than 1 min . With the new oxygenator connected , the flows were increased to 5.91 L / min at 3300 RPM with 229 mmHg resistance , and the radial artery blood pressure was 69 mmHg .
Five minutes following the replacement of the oxygenator , the flows decreased to 5.29 L / min with maximum RPMs of 3500 , and over the next 15 min , the flows continued to steadily decrease to 4.50 L / min although the RPMs remained high at 3497 . At this point , the patient was fully cooled to 22.1 ° C and DHCA with RCP was initiated and cardiopulmonary bypass was turned off . The perfusion team decided to exchange the oxygenator again during the DHCA period . For the second oxygenator exchange , it was decided to use a Terumo FX25