Ann Thorac Surg 2010;89:e2-e3. doi:10.1016/j.athoracsur.2009.09.051
© 2010 The Society of Thoracic Surgeons
How To Do It
Transition to Post-Bypass Pediatric Mechanical Support
Katherine Cleveland, MS, PAC,
Robert Keenan, BS, CCP,
Ronald K. Woods, MD, PhD*
Mary Bridge/Swedish Pediatric Cardiothoracic Surgery Program, Mary Bridge Children's Health Center, Tacoma, Washington
Accepted for publication September 22, 2009.
* Address correspondence to Dr Woods, Mary Bridge/Swedish Pediatric Cardiothoracic Surgery Program, Mary Bridge Children's Health Center, 311 South L St, PO Box 5299, Tacoma, WA 98415 (Email: ronald.woods{at}multicare.org).
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Abstract
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We report an alternative technique for achieving hemostasis in the conversion from bypass to post-repair mechanical cardiac support.
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Introduction
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Significant coagulopathic bleeding frequently occurs with post-repair transition from bypass to extracorporeal life support (ECLS), with re-exploration for bleeding required in 30% to 50% of cases [1, 2]. A common approach is to wean from bypass, reverse heparin, administer factors, and then initiate ECLS with variable degrees of re-heparinization [3, 4]. Excessive coagulopathic bleeding or limited time for heparin reversal due to cardiac dysfunction can lead to ongoing bleeding on ECLS.
We recently encountered two cases that prompted us to take a different approach. We were impressed by the results; therefore, we offer this approach for consideration. However, we want to be very clear in regard to certain points: (1) This is a very preliminary report with limited data to substantiate its use, and (2) we currently only consider its use in very high-risk contexts. We refer to this technique as "coagulation under full-flow bypass" (CUFF). Surgical consent was uniform. This study was approved by our institutional review board.
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Technique
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The technique, summarized in the following steps is applicable to post-repair transition to ECLS in the operating room for patients demonstrating significant nonsurgical bleeding and intolerance of the time off support required by more customary measures to control bleeding:- 1 Verify immediate availability and functionality of the ECLS circuit.
- 2 Bypass circuit in use should have arterial line filter.
- 3 Briefly wean patient from bypass if possible and perform echocardiogram to confirm no residual defects. Document hemodynamics and confirm necessity of postoperative mechanical support.
- 4 Resume high-flow bypass and administer platelets and clotting factors, and partially reverse heparin.
- 5 Continue use of cardiotomy suction and assess degree of hemostasis; if inadequate, completely reverse heparin and administer additional factors as needed. With complete heparin reversal, it may be prudent to discontinue cardiotomy suction.
- 6 During steps 4 and 5, closely monitor the entire circuit from cannula to cannula with emphasis on the reservoir and oxygenator for clot formation.
- 7 As soon as hemostasis is adequate, or there is evidence of clot in the circuit (eg, pre-oxygenator pressures, inspection of reservoir), then promptly convert to ECLS.
- 8 If converting with adequate hemostasis to a bonded circuit, administer 25 to 50 units heparin per unit of packed cells to the circuit (for standard neonatal arrangement), no heparin to the patient, and run high-flow (150 cc/kg/min), heparin-free to the patient for the next 1 to 2 hours (potentially longer if necessary). Heparin is subsequently administered to achieve a target activated clotting time of 160 to 180 seconds.
Our cardiopulmonary bypass circuit is biocompatible polymer-coated (X Coating [Terumo Cardiovascular Systems, Ann Arbor, MI] includes oxygenator; excludes cannula) whereas our ECLS circuit is heparin-bonded (Carmeda [Medtronic Perfusion Systems, Minneapolis, MN]) with biopassive coating of the oxygenator (Quadrox, Softline Coating [Maquet Cardiovascular, Wayne, NJ]). For cardiac repair, epsilon-aminocaproic acid is administered at induction and infusion maintained for 12 hours postoperatively.
Thus far, we have used this technique only as a salvage maneuver. The first patient was a former preemie (weight, 1.7 kg) with double-outlet right ventricle (ventricular septal defect type), unrestricted pulmonary flow, bacterial sepsis, and failure. She re-presented 5 weeks after a band with progressive cyanosis and a saddle embolus depicted on angiogram. She deteriorated after catheter-directed lytic therapy (desaturation and cardiac failure), and she was placed on ECLS. After 48 hours and no improvement, she was converted to bypass for operative exploration, which revealed thrombus and aspergilloma filling a disintegrated pulmonary artery bifurcation. A trial wean after repair of double-outlet right ventricle (pulmonary artery bifurcation reconstructed with pericardium) confirmed complete pump dependence and massive coagulopathy bleeding, as well as pulmonary hemorrhage, despite partial heparin reversal and administration of platelets, factors, and recombinant factor VII. As death from the hemorrhage seemed to be inevitable, we continued high-flow bypass and repeated the later steps of the CUFF sequence. Hemostasis substantially improved, and she was converted to ECLS. During the next 12 hours, she required 30 mL of blood transfusion. Re-exploration for bleeding was not required. She was weaned from ECLS on day 5 with good cardiopulmonary function and unchanged neurologic status; a head computed tomographic scan demonstrated moderate low attenuation of periventricular white matter, but no evidence of embolic stroke. The patient ultimately died weeks later from overwhelming invasive aspergillosis, despite maximal antifungal therapy.
The second patient (weight, 3.7 kg; age, 7 weeks) presented late with severe coarctation, hypoplastic arch, and aortic stenosis with very poor left ventricular function, with a shortening fraction of 8%. He underwent an extended end-to-end repair of the arch and coarctation through the left chest with no residual gradient. On the operating table, an echocardiogram showed mildly improved function and unchanged left ventricular outflow gradient (peak, 45 mm Hg). Six hours postoperatively, acute decompensation with ventricular arrhythmia required emergent ECLS. Two days of support with no change in function led to a surgical valvotomy (converted from ECLS to bypass) aperture increased from 4 mm to 7 mm with no aortic insufficiency). He demonstrated an inability to wean from bypass and significant coagulopathic bleeding, including pulmonary hemorrhage. Using CUFF, hemostasis was quickly achieved (< 10 minutes) prior to transition to ECLS. During the following 12 hours, he required 80 mL of blood transfusion. Re-exploration for bleeding was not required. He was weaned from ECLS after 18 days of support. The patient is currently doing well as an outpatient. His neurologic status and head ultrasound are normal. For both patients, clot appeared in the primary circuit only after flow was terminated.
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Comment
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The prudence of deferring heparin reversal and administration of clotting factors to the post-bypass period is acknowledged. The paucity of data confirming the negative consequences of doing otherwise admittedly does not justify departure from first principles. However, the practice of preserving the pump in the event of a need to return to bypass was established before widespread availability of intraoperative transesophageal or epicardial echocardiography and post-cardiotomy mechanical support. With current technology, it should be possible to minimize the unpredictable event of needing to "crash" back on bypass after heparin reversal to correct a residual intracardiac defect. Deterioration due to other causes should be amenable to support with ECLS (or other assist device). Also, two characteristics of standard ECLS practice are noteworthy: (1) platelets and clotting factors are routinely administered during support, and (2) in the context of excessive bleeding and a coated circuit, limited duration heparin-free support is considered acceptable [5]. The CUFF method simply applies these principles in a slightly different context. Particularly for transition to ECLS, the downside of clotting the bypass circuit seems minimal.
It is tempting to further speculate that the CUFF method may be useful for the uncommon but very real phenomenon of post-bypass massive coagulopathy bleeding outside the context of transition to ECLS. The theoretical advantages would be maintenance of high flow; avoidance of the negative impact on cardiac output of a large-volume transfusion of platelets and clotting factors, and maintenance of a normal blood pH and body temperature. The obvious disadvantage is the increased resource inherent to backing up a failed circuit, should the need emergently arise.
Regardless of context, formation of clot in the circuit and embolization to the patient are important safety concerns. Although a clot should first occur in the reservoir or oxygenator, and some protection is afforded by the arterial line filter, further investigation is appropriate. Spectral Doppler of the arterial line and post-CUFF brain magnetic resonance imaging would be potentially relevant. Although we are initiating a protocol for investigation, acquisition of statistically meaningful data will require several years, given the anticipated low frequency of the CUFF method in our program. We regret not having this data to present, but we believed that a preliminary report might allow other programs to consider evaluation of this technique.
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References
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- Duncan BW, Hraska V, Jonas RA, et al. Mechanical circulatory support in children with cardiac disease J Thorac Cardiovasc Surg 1999;117:529-542.[Abstract/Free Full Text]
- Alsoufi B, Al-Radi OO, Gruenwald C, et al. Extra-corporeal life support following cardiac surgery in children: analysis of risk factors and survival in a single institution Eur J Cardiothorac Surg 2009;35:1004-1011.[Abstract/Free Full Text]
- Jaggers JJ, Forbess JM, Shah AS, et al. Extracorporeal membrane oxygenation for infant postcardiotomy support: significance of shunt management Ann Thorac Surg 2000;69:1476-1483.[Abstract/Free Full Text]
- Aharon AS, Drinkwater DC, Churchwell KB, et al. Extracorporeal membrane oxygenation in children after repair of congenital cardiac lesions Ann Thorac Surg 2001;72:2095-2102.[Abstract/Free Full Text]
- Alsoufi B, Shen I, Karamlou T, et al. Extracorporeal life support in neonates, infants, and children after repair of congenital heart disease: modern era results in a single institution Ann Thorac Surg 2005;80:15-21.[Abstract/Free Full Text]
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Abstract
Introduction
