A Comparison of Static Occlusion Setting Methods: Fluid Drop Rate and Pressure Drop

Tubing circuits primed with water were constructed on two roller pumps to characterize and compare two static methods of setting the occlusion on roller pumps (fluid drop rate and pressure drop rate). Twelve separate experiments were performed in which PVC boot tubing diameters (1/2 in, 3/8 in and 1/4 in), roller position (each roller alone on a two roller pump) and roller occlusion (total occlusion to 0.004 in underocclusion) were varied. Fluid drop rates were measured from two heights (30 in and 1 m) above the pump head where drops of 1 em and 1 in were timed for each occlusion setting. Pressure drop was measured by clamping the outlet tubing, injecting fluid into the tubing between the clamp and roller elevating the pressure to 300 mmHg and observing the rate that it dropped at each occlusion setting. Fluid drop rate and pressure drop rate were positively correlated at all occlusion settings and tubing sizes (p < 0.001). Using a single roller occlusion and an optimal fluid drop rate of .5 to 1.5 cm/min. at 30 in height, pressure drops (mmHg/min.) were (mean± SD); 1/2 in tubing= 263 ± 33, 3/8 in= 241 ±52, 1/4 in= 264 ± 11. For a fluid drop rate of 1.27 to 3.81 cm/min. at 1m height, pressure drops were (mean± SD); 1/2 in= 266 ± 33, 3/8 in=278 ± 17, 114 in=274 ± 20. The occlusion settings or occlusion gap varied significantly (p < 0.001) between pumps and tubing sets. Thus, it appears as though pressure drop rate can predict fluid drop rate at just nonocclusive pump settings; however, the occlusion should be rechecked every time a different pump or boot tubing is used

Use of the CDI Blood Parameter Monitoring System 500 for Continuous Blood Gas Measurement During Extracorporeal Membrane Oxygenation Simulation

The Oximetrix III Opticath (Abbott Critical Care Systems) is used for continuous measurement of venous saturation in a variety of applications, including extracorporeal membrane oxygenation (ECMO), despite clinical reports that have presented data showing poor accuracy of these devices. The CDI Blood Parameter Monitoring System 500 (Terumo) is an inline blood gas monitoring tool commonly used during cardiopulmonary bypass procedures to continuously assess oxygen saturation, blood gases, potassium, and bicarbonate. The purpose of this experiment was to compare the Opticath and the CDI 500 in trending venous blood saturation during a simulation of ECMO. An ECMO simulation circuit consisting of a silicone rubber membrane oxygenator and a stainless steel heat exchanger was constructed, and a standard venous reservoir bag was used to represent the patient. The CDI and the Opticath were incorporated side by side into a shunt that originated just before the oxygenator and returned flow to the venous line. The circuit was primed with fresh porcine blood and conditioned with the addition of CO2 to simulate typical venous blood under ECMO conditions. After an initial calibration procedure, samples were drawn and analyzed by an AVL Opti CCA (Roche/Osmetech) every 4–8 hours for a period of 7 days, with calibration of each device at sample intervals. The data were plotted, and a least squares regression line was calculated. The average error for venous saturation of the CDI and Opticath after 72 hours was 3.86 and 9.51 respectively. At 168 hours, error for the CDI was 8.37, and the Opticath had an error of 14.78. A correlation analysis of the CDI and AVL CCA analyzer yielded a correlation coefficient of r = .88 at 72 hours and r = .84 at 168 hours. Correlation between the Opticath and the AVL CCA yielded a correlation coefficient of r = .77 at 72 hours and r = .55 at 168 hours. Based on these findings, the CDI 500 is an effective tool for monitoring venous blood saturation under simulated conditions of ECMO

Oxygenator Evaluation: Maxima 1380 Versus Maxima Plus

Continual improvement of oxygenators has been important in the growing demands of patient safety and support during cardiopulmonary bypass. The purpose of this study was to compare the Maxima 1380 oxygenator to the upgraded Maxima Plus oxygenator. Thirty-two adult patients were randomized to either the 1380 group or the Plus group. Information was recorded on the patients' weight, age, body surface area, esophageal temperature, arterial temperature, venous oxygen saturation, arterial pO2, arterial pCO2, blood flow, hematocrit, gas sweep, and FiO2. No significant difference was found between the two groups' mean weight, body surface area, arterial pO2 arterial pCO2, age, esophageal temperature, arterial temperature, venous oxygen saturation, and blood flow (p > 0.05). The Plus group demonstrated significantly lower mean gas sweep rates and FiO2 settings than the 1380 group. FiO2 of the 1380 was dependent on age, body surface area, blood flow, and esophageal temperature (r = 0.89, p < 0.001). FiO2 of the Plus was correlated with weight, esophageal temperature, arterial temperature, and arterial pO2 (r = 0.93, p < 0.001). Gas sweep rate of the 1380 was dependent on age, weight, esophageal temperature, blood flow, arterial temperature, and arterial pCO2 (r = 0.84, p < 0.001). The gas sweep rate of the Plus was dependent on weight and esophageal temperature (r = 0.55, p < 0.001). Based on these analyses, the new Maxima Plus oxygenator is more efficient in oxygen and carbon dioxide transport than the Maxima 1380

Evaluation of Five In-Line Hematocrit Monitors

Monitoring the hematocrit is essential during cardiopulmonary bypass for efficacious administration of blood products. The purpose of this study was to evaluate five cardiopulmonary bypass in-line monitors designed to display continuous hematocrit or hemoglobin values. The devices were evaluated for accuracy using an in vitro circuit primed with human blood while randomizing hematocrit, blood flow rate, and temperature. Hematocrits correlated significantly with the error in all the devices (p < 0.01). Over evaluation time, the error of the CDI, Gish, IBC, and MX2 increased significantly (p < 0.05). Temperature correlated significantly with the error of the Gish device (r = -0.49, p < 0.01). Blood flow correlated significantly with the Gish error (r = -0.24, p < 0.01). The Cobe device had a significantly smaller overall error than the other devices (p < 0.001). Device evaluation, based on a low mean error, a low percent error, a high correlation with the actual hematocrit, low correlations between mean error, blood flow, and temperature, and insignificant correlation between time and error, suggests that the Cobe device is more accurate for the continuous monitoring of hematocrit during cardiopulmonary bypass

Evaluation of a Rapid Infusion System

Operative cases where there is a potential for massive blood loss necessitates a system to rapidly warm and transfuse large volumes of blood over short periods of time. An in-house system in which both crystalloid solutions and blood products can be quickly added, warmed and available for infusion was developed to meet this need. The purpose of this study was to evaluate how blood products are affected when warmed and recirculated for an extended period of time. A recirculating rapid infusion system was assembled utilizing two filtered cardiotomy reservoirs, a centrifugal pump, a stainless steel blood heat exchanger, and 1/4 inch tubing, and applied in six adult orthotopic liver transplantations. The system was primed with 2 to 4 units each of fresh frozen plasma and packed red blood cells. The prime was recirculated and warmed to 37°C. Samples for blood gases, oxygen saturation, hematocrit, plasma free hemoglobin, sodium and potassium levels were drawn after initial priming and then every 30 minutes until additional blood products were added. Results show no significant change in pH (6.57 ± 0.21), pO2 (56 mmHg ± 23 mmHg), pCO2 (173 mmHg ± 138 mmHg), hematocrit (27% ± 8.7%) and plasma free hemoglobin values (125 mg/dl ± 9.4 mg/dl), following 3 hours of recirculation. However, potassium levels significantly decreased from 11.6 meq/L ± 2.6 meq/L to 10.0 meq/L ± 2.3 meq/L (p<0.05), sodium levels significantly increased from 144 meq/L ± 5.9 meq/L to 147 meq/L ± 5.3 meq/L (p<0.05) and oxygen saturations significantly increased from 59%± 9.1% to 70% ± 16% (p<0.05). The results demonstrate that this system can maintain banked blood warm and available for immediate infusion without significant deterioration for up to 3 hours

Electrostatic Potential Generated During Extracorporeal Pump Prime Circulation Before Cardiopulmonary Bypass Initiation

The development of electrostatic potentials generated during cardiopulmonary bypass (CPB) procedures using polyvinylchloride (PVC) tubing in conjunction with roller pumps has been previously documented. The resulting damage from the electrostatic discharge (ESD) has been reported to affect gas transfer devices, but details of potential damage to electronic components commonly used during extracorporeal circulation have not been similarly described. The purpose of this study was to measure the ability of a triboelectric potential to be generated from a primed, circulating, adult CPB pump before the initiation of CPB. Two identical adult CPB circuits were assembled: one incorporating a roller pump and the second incorporating a centrifugal pump mechanism. Primed pumps were circulated (1–6 LPM), and evidence of generated triboelectric potentials was evaluated using a digital multimeter (Fluke 8062 A). The ESD generated from an adult CPB circuit using a roller head configuration elicited a charge in excess of 600 DC V. An identical circuit constructed with a centrifugal pump mechanism did not produce any measurable charge. Sensitive electrical components in the CPB hardware platform may be damaged by ESD potential spikes of this magnitude. Preventative measures, such as circuit charge dissipation, may reduce the potential for such damage when using PVC tubing

Triboelectric Charging and Dissipation Characteristics of the Maquet Quadrox-D Membrane Oxygenator

Triboelectric charging is commonly detected during cardiopulmonary bypass in circuits using roller pumps and PVC tubing. Dissipation of this charging is needed to prevent a spontaneous discharge from occurring. We evaluated the ability of the Quadrox-D (Maquet) to effectively remove the electrostatic charge accumulation, with and without a heater/cooler connection (H/C). A Quadrox-D oxygenator was evaluated using a Stockert SIII pump head, Cincinnati subzero H/E, and a custom adult extracorporeal membrane oxygenation tubing pack with 1/2′ PVC raceway. The circuit was primed and evaluated for triboelectric accumulation with and without H/C use. The results showed a linear relationship between increasing pump flow and static charge build-up when an H/C was not applied. The calculated r2 value was .95. Incorporation of the H/C effectively eliminated charge accumulation. Increasing pump speed increases the amount of static charge created without the use of an H/C. Incorporation of an H/C effectively eliminates charge build-up in the Quadrox-D and is recommended while priming the circuit

Hemicolectomy With Concomitant Heated Intraperitoneal Chemotherapy: A Case Study

The use of heated intraperitoneal chemotherapy is an emerging new adjunct in the treatment of adenocarcinoma of the colon. However, documentation regarding perfusion circuitry and techniques associated with this therapy remain largely undescribed. After consultation with the surgical service team, a custom designed circuit was constructed for this procedure. Institutional approval and informed consent were obtained for surgical debulking and heated intraperitoneal chemotherapy for a 58-year old female. After surgical resection, a right hemicolectomy was performed and pathological specimens obtained. A modified custom circuit using a roller pump was first primed with 3 liters of Dianeal® PD-2 and recirculated until temperature of 41°C was obtained. The circuit was then connected to the patient for infusion of perfusate via Blake drains placed in the deep pelvis. Two additional drains were placed in the subdiaphragmatic space for return. Perfusate containing 30 mg of Mitomycin-C was circulated at 600–800 mL/min for 60 min at 41°C. An additional 10 mg of Mitomycin-C was then administered through the circuit for an additional hour under similar conditions. Upon completion, a washout procedure was performed with 2 additional liters of Dianeal® PD-2. The patient tolerated the procedure well and was discharged postoperative day 7. We describe the successful use of a perfusion-administered heated intraperitoneal chemotherapy regimen as an integral part of successful treatment of adenocarcinoma of the colon

Correlation of ACT as Measured with Three Commercially Available Devices with Circulating Heparin Level during Cardiac Surgery

Automated activated clotting time (ACT) is utilized as the primary means of assessing anticoagulation status for cardiopulmonary bypass (CPB) procedures. Influences on the clotting cascade during CPB such as hypothermia, hemodilution, and platelet dysfunction are known to affect ACT. The recently introduced Thrombolytic Assessment System (T AS) has been reported to be less sensitive to changes in hemodilution and hypothermia during CPB than more conventional ACT devices. This study evaluated the ability of TAS, and two other commercially available automated ACT systems, the HemoTec and Hemochron, to correlate with circulating heparin levels. Reference standards for circulating heparin were determined by inactivation of factor Xa assay. Nineteen patients undergoing moderate hypothermic CPB served as subjects for this investigation. Blood samples were obtained for study at four time periods: 1) baseline (control), 2) post heparin administration (300-400 U/kg) prior to CPB, 3) during CPB, and 4) post protamine. Study results demonstrated a high correlation between the HemoTec and Hemochron (r = 0.99), increased heparin dose response on CPB compared to pre-CPB activity (p < 0.05), and a significant (p<0.05) negative correlation between devices and patient hematocrit during CPB. Additionally, device correlation with anti-Xa assay during collection periods 2 and 3 showed negative correlations in each of the three devices evaluated. We conclude that all automated devices tested demonstrated an inability to predict circulating heparin at levels necessary for CPB, and that these discrepancies become magnified during CPB procedures