Shearer Ir

Techniques of paediatric modified ultrafiltration: 1996 survey results.

In September 1996, perfusionists from 50 paediatric open-heart surgery programmes were contacted to identify centres that are currently using the technique of modified ultrafiltration (MUF). Of the 50 centres contacted, 22 (44%) were utilizing the technique. These centres were surveyed on the following: neonatal circuit description, patient entry criteria, MUF circuit description, conduct of MUF, use of extracorporeal safety devices and/or modifications, and technical complications. All 22 centres used roller pumps and membrane oxygenators. In 19 centres, MUF was utilized exclusively in the arteriovenous mode (86%), while two centres (9%) used the venovenous mode and one centre (5%) used both methods. Most (82%) of the 22 MUF centres used a blood cardioplegia system for myocardial preservation. After cardiopulmonary bypass (CPB), these blood cardioplegia systems were often converted for use as MUF circuits in a variety of ways. Other methods of accessing the CPB circuit for MUF included utilizing either a recirculation line or a dedicated port added to the circuit specifically for MUF. Blood flow rates during MUF, pump strategies, haemoconcentrator vacuum levels and endpoints were variable from centre to centre. Technical complications related to MUF were reported by 82% of the surveyed MUF centres. The most common complication, air cavitating into the circuit, was reported by 15 centres. From these data, we propose recommendations on the integration of MUF into CPB circuits, the conduct of perfusion during MUF, and appropriate safety considerations to minimize technical complications.

Impact of modifying priming components and fluid administration using miniaturized circuitry in neonatal cardiopulmonary bypass

Following a succession of changes in circuitry and priming additives between 1993 and 1998, a comprehensive re-evaluation of neonatal cardiopulmonary bypass (CPB) practice was undertaken. Samples from 10 infants (Group 1) undergoing CPB were evaluated for osmolality, oncotic pressure, total protein, hematocrit, glucose, and electrolytes (Na+, K+, iCa2+). These samples were tested at six measurement points: (1) after priming, (2) patient pre-CPB, (3) CPB-start, (4) CPB-mid, (5) CPB-end, and (6) post-modified ultrafiltration (MUF). Prime volumes were also carefully measured as well as the type and amount of volume given during CPB. After evaluating the initial data, changes in protocol regarding mannitol, calcium correction, and oncotic strength on CPB were made. Following implementation of these protocol changes, a second set (Group 2) of 10 infants was identically evaluated. Group 1 prime osmolality was 379 ± 44 mOsm/kg, while Group 2 prime osmolality was 324 ± 14 mOsm/kg (p = 0.003). There were no differences in osmolality between groups during bypass and osmolality was unaffected by modified ultrafiltration. Ionized calcium levels were significantly different at the end of bypass between Group 1, 0.6 ± 0.1 mmol/l; and Group 2, 1.17 ± 0.24 mmol/l (p < 0.001). In Group 1, there was a 40% drop (p = 0.001) in colloid osmotic pressure (COP) levels from pre-CPB (13.3 ± 3.4 mmHg) to CPB-end (8.8 ± 1.2 mmHg). In Group 2, there were no differences in COP during CPB. COP levels of Group 1 and Group 2 at CPB-end were 8.8 ± 1.2 mmHg and 14 ± 1.9, respectively (p < 0.0001). Total volume addition during bypass for Group 1 was 363.5 ± 148.7 ml and for Group 2 was 245.1 ± 92.2 ml (p < 0.05). In conclusion, progressive changes in neonatal circuits and techniques can have potentially wide-ranging effects on electrolyte and osmotic/oncotic homeostasis. An audit of perfusion management through expanded laboratory tests is recommended, especially in periods of change.

Development of a collaborative program to provide extracorporeal membrane oxygenation for adults with refractory hypoxemia within the framework of a pandemic.

Objective: We report the process used to rapidly develop a collaborative adult respiratory extracorporeal membrane oxygenation program as a response to caring for young adult patients with refractory hypoxemia in the setting of the pH1N1 pandemic. Design: Interdisciplinary response of a complex medical system to a public health crisis. Patients, Interventions, Measurements, and Main Results: After the successful use of extracorporeal membrane oxygenation in young adults with pH1N1-induced acute respiratory distress syndrome refractory to conventional therapies, an adult venovenous extracorporeal membrane oxygenation program was implemented over an 8-wk period. Implementation of this program involved a number of key steps that were crucial in the development process, including administrative and institutional support, multidisciplinary leadership and collaboration, extensive interdisciplinary educational initiatives, and substantial technical modifications. Conclusions: In the setting of the pH1N1 influenza pandemic, an adult respiratory extracorporeal membrane oxygenation program was successfully developed to complement an established neonatal-pediatric program. This program expansion integrated all of the necessary components involved in the development process from start to finish and confirms that a healthcare system can respond very quickly and successfully to an urgent healthcare need.

Evaluation of a preprimed microporous hollow-fiber membrane for rapid response neonatal extracorporeal membrane oxygenation.

Delays in initiating extracorporeal membrane oxygenation (ECMO) in the critically ill pediatric patient may lead to adverse outcomes. Maintaining a primed ECMO circuit can considerably reduce the initiation time. The predominant concerns precluding this practice are a decrease in oxygenator efficiency due to the saturation of microporous hollow fibers and compromised sterility when the oxygenator has been primed for 30 days. For institutions using a hollow-fiber oxygenator for ECMO, there are no data reporting pre-primed hollow-fiber oxygenator viability. This study reports the efficiency of oxygen transfer and the sterility of the Carmeda Minimax Plus (Medtronic, Inc, Minneapolis, MN) oxygenator after being crystalloid primed for 30 days. A total of 10 Minimax Plus oxygenators were tested for oxygen transfer in a laboratory setting utilizing fresh whole bovine blood. The control group (n=5) were tested immediately after priming. The test group (n=5) were oxygenators primed for 30 days with crystalloid solution and left stagnant until tested. Prior to testing, all oxygenators were circulated for 5 min and samples drawn to test for circuit sterility. Venous inlet saturations were manipulated to achieve three levels of testing: venous saturation (SvO2) of 55% for an oxygen challenge, SvO2 of 65% to comply with AAMI standards, and SvO2 of 75% to assess oxygen transfer rates and peak PaO2 achievement. Blood flow for all tests was maintained at 2 L/min with 1:1 blood to gas flow ratio and 100% FiO2. Samples were drawn pre- and postoxygenator at 1- and 6-hour time intervals to compute actual oxygen transfer values. All cultures from the test group priming solution produced no microbial growth after 30 days of stagnant prime. Average oxygen transfer values (ml/O2/min) for the control group after 1 hour of continuous use were 130.1±15.5 (@55% SvO2), 113.7±10.4 (@65% SvO2),97.7±8.9 (@75% SvO2). After 6 hours, the average transfer values increased to 134.2±13.2 (@55% SvO2), 118.76±6.6 (@65% SvO2) and 98.9±8.3 (@75% SvO2). The average oxygen transfer values after 1 hour for oxygenators primed for 30 days were 114.9±10.0 (@55% SvO2), 112.4±8.2 (@65% SvO2) and 89.6±16.0 (@75% SvO2). After 6 hours of use, the average transfer values all decreased to 111.4±2.1 (@55% SvO2, p <0.05 versus control), 104.0±5.6 (@65% SvO2, p<0.05 versus control) and 88.4±3.2 (@75% SvO2, p<0.05 versus control). In conclusion, there was a decrease in the average oxygen transfer values for the test group after 6 hours versus the control. The modest loss of oxygen transfer ability observed can be considered acceptable due to the amount of surface area of the Minimax Plus oxygenator when used on a neonate, making it feasible to adopt the practice of prepriming the Minimax oxygenator for neonatal ECMO.

Serum creatinine patterns in coronary bypass surgery patients with and without postoperative cognitive dysfunction

Renal dysfunction is common after coronary artery bypass graft (CABG) surgery. We have previously shown that CABG procedures complicated by stroke have a threefold greater peak serum creatinine level relative to uncomplicated surgery. However, postoperative creatinine patterns for procedures complicated by cognitive dysfunction are unknown. Therefore, we tested the hypothesis that postoperative cognitive dysfunction is associated with acute perioperative renal injury after CABG surgery. Data were prospectively gathered for 282 elective CABG surgery patients. Psychometric tests were performed at baseline and 6 wk after surgery. Cognitive dysfunction was defined both as a dichotomous variable (cognitive deficit [CD]) and as a continuous variable (cognitive index). Forty percent of patients had CD at 6 wk. However, the association between peak percentage change in postoperative creatinine and CD (parameter estimate = −0.41;P = 0.91) or cognitive index (parameter estimate = −1.29;P = 0.46) was not significant. These data indicate that postcardiac surgery cognitive dysfunction, unlike stroke, is not associated with major increases in postoperative renal dysfunction.

A clinical evaluation of the Dideco Kids D100 neonatal oxygenatora

In August 2006, Duke University Perfusion Services had the opportunity to be the first institution in the United States to clinically evaluate the Dideco D100 Neonatal Oxygenator. The device was used on six pediatric patients to facilitate correction or palliation of their cardiac defects, which included two arterial switch operations, two truncus arteriosus repairs, one stage 1 Norwood and one repair of total anomalous pulmonary venous return. The average patient weight was 3.1 kg. The average cardiopulmonary bypass(CPB) time was 135 minutes and the average cross-clamp time was 61 minutes. Arterial and venous blood gasses were drawn and used to calculate oxygen transfer. The average oxygen transfer was 14.8 ± 10.3 ml/O2/min. The Dideco D100 Oxygenator is the first oxygenation device designed specifically for neonates. The Dideco D100 is a microporous hollow-fiber device. It has a static priming volume of 31 ml and a maximum rated flow of 700 ml/min. The integral hard-shell venous reservoir has a minimum operating level of 10 ml and a reservoir capacity of 500 ml. For this evaluation, the Dideco Kids D100 Neonatal Oxygenator performed adequately on patients weighing up to 5 kg. This device provides an excellent first step towards offering very small children appropriate circuitry without having to sacrifice safety or performance.

Venous line filtration: a novel technique for cases involving inferior vena caval and right atrial tumor and associated thrombus: a two-case series:

Two patients are presented with right atrial tumors, who were considered to be at risk for tumor thrombus migration down the venous line into the cardiopulmonary bypass (CPB) circuit during surgical excision, which may lead to compromised or interrupted venous drainage. An arterial line filter was placed in the venous line to capture any material that might become dislodged and embolize into the circuit. Vacuum-assisted venous drainage, at approximately -50 mmHg, was used to overcome any resistance caused by the filter in the venous line. In one case, tumor thrombus obstructed the filter, requiring the use of the bypass line around the filter, so venous return could be maintained. In both cases, thrombus was found in the filter. The first case was a 44-year-old female (81 kg, 137 cm, body surface area (BSA) 1.66 m2) who presented with a metastatic pheochromocytoma with associated thrombus arising from the left adrenal gland and extending into the inferior vena cava (IVC) and right atrium. The second case was a 37-year-old male (95 kg, 178 cm, BSA 2.17 m2), who presented with a very large angiosarcoma tumor involving almost the entire right atrium. We have shown that venous line filtration with vacuum-assisted venous drainage can be performed safely, and should be considered in cases where there is tumor thrombus in the vena cava or right atrium, which may threaten venous return.