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Ann Thorac Surg 1999;67:1415-1420
© 1999 The Society of Thoracic Surgeons

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Original Articles

Intraaortic balloon pumping in children

^a Departments of Department of Cardiac Surgery, Royal Liverpool Children’s Hospital-Alder Hey, Liverpool, England, UK
^b Department of Anaesthetics, Royal Liverpool Children’s Hospital-Alder Hey, Liverpool, England, UK

Accepted for publication November 24, 1998.

Address reprint requests to Dr Pozzi, Department of Cardiac Surgery, Royal Liverpool Children’s Hospital-Alder Hey, Eaton Rd, Liverpool, L12 2AP, England
e-mail: mpozzi{at}liverpedcard.u-net.com

	Abstract

Top Abstract Introduction Patients and methods Results Comment Summary References

 
Background. Intraaortic balloon pump (IABP) usage in young children remains a rarity because, first, there is a widespread misconception that the greater elasticity of the aorta in children may prevent effective augmentation, and second, children in low cardiac output states are more likely to have associated right ventricular failure and pulmonary problems. We report our experience with the use of IABP in children undergoing cardiac surgery in whom mechanical support was necessary for the treatment of refractory cardiac failure.

Methods. Over a 3-year period, 14 children were identified as requiring IABP support after cardiac surgery. Their median age was 3 years (range 7 days to 13 years) and their median weight was 13.3 kg (range 3.5–51 kg). Indications for IABP use were: failure to wean from cardiopulmonary bypass (5 patients), sudden deterioration in intensive therapy unit (ITU) (3 patients), progressive deterioration in ITU (4 patients), and prophylactic therapy for known poor preoperative ventricular function (2 patients).

Results. Ten of 14 patients (71%) were successfully weaned from the IABP, of whom 8 became long-term survivors (57%). Among the survivors, the mean duration of IABP usage was 127 h (range 12–260 h), while for those who died while on IABP, the mean duration was 15 h (range 8–24 h). The most major IABP-related complication encountered was mesenteric ischemia, which had a fatal outcome.

Conclusions. IABP therapy, used as an adjunct to conventional medical treatment, can give properly selected young children in refractory low cardiac output states after heart surgery a greater than 50% chance of long-term survival.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Summary References

 
The intraaortic balloon pump (IABP) has become a well-established therapy in adults for the management of refractory low cardiac output states [1]. Although pediatric intraaortic balloon catheters and equipment modifications have been available since the mid 1980s [2, 3], there has not been widespread use of the IABP in pediatric cardiac centers. Literature reports on pediatric IABP usage have been sporadic [2–7]. Extracorporeal membrane oxygenation (ECMO) has become a more common mode of supporting refractory low-output states in children because it offers biventricular and pulmonary support [8, 9]. IABP and left ventricular assist devices (LVAD) are limited to supporting the left ventricle. Nevertheless, we believe that many children undergoing cardiac surgery for complex congenital heart defects may benefit from the IABP. We present our experience with the use of IABP in 14 children who were deemed to require mechanical support after undergoing cardiac surgery.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Summary References

 
Over a 3-year period from August 1994 to September 1997, 14 pediatric cardiac patients were identified as requiring IABP support in the perioperative period. Their medical records were reviewed for age, weight, diagnosis, operation, and inotropic support before IABP use, balloon size and site of insertion, timing of balloon deployment, duration of support, outcome, and complications (Table 1). There were 10 boys and 4 girls, with a median age of 3 years (range 7 days to 13 years) and a median weight of 13.3 kg (range 3.5–51 kg).

Timing of balloon pump deployment and indications
All the 14 patients were on mechanical ventilation and were receiving between one and four (mean of three) inotropic drugs before IABP use. Femoral arterial, central venous and left atrial pressures, oxygen saturation, electrocardiogram, and core and skin temperatures were monitored on a Hewlett Packard 66S system (Hewlett Packard, Boeblingen, Germany). Once IABP was deployed, arterial monitoring was transferred to the IABP console. Seven of 14 patients had the IABP initiated in the operating theater: 5 for failure to wean from cardiopulmonary bypass (patients 3, 4, 7, 10, and 11), and 2 for known poor preoperative left ventricular function (patients 1 and 6). The other 7 patients had the IABP instituted in the intensive care unit: 3 (patients 5, 8, and 13) for sudden deterioration within 6 h of arrival in intensive care, and the other 4 for progressive deterioration with hypotension, persistent metabolic acidosis and poor urine output despite optimal inotropic support. Three of these 4 patients were on peritoneal dialysis, and the time of balloon pump initiation ranged from 24 h to the seventh postoperative day (mean 136 h).

Site of balloon insertion
The balloon catheters were inserted directly via the ascending aorta in our 5 smallest patients (median weight 4.5 kg), utilizing the purse-stringed cardioplegia delivery site. In these patients, the chest was left open for the duration of IABP use, the wound being covered with a silicone membrane sutured to the skin edges. The other patients received the balloon via the common femoral artery by direct cut down to the artery, where the balloon was introduced either directly (6 patients), or via a 5-mm Gore-Tex sleeve (W.L. Gore & Assoc, Flagstaff, AZ) anastomosed end to side to the femoral artery (3 patients). The balloon position was verified on roentgenogram according to standard guidelines [3].

Pumping console
The Datascope System 97 pumping console (Datascope Medical Co Ltd) with pediatric volume-limiting chamber was used on all but 1 patient who received a 34-cc balloon, in whom the Datascope system 90 was used because it was the only console available at the time. Manual filling of the catheter balloon with helium was performed hourly, and balloon frequency was 1:1, except during weaning. Augmentation timing required manual adjustment for heart rate changes greater than 10 beats/min in order to obtain optimal diastolic augmentation and presystolic dip.

Weaning
Once hemodynamic stability was maintained, augmentation was reduced to 50% by pressing the augmentation reduction button once every 5 min until the visual indicator on the console corresponded to 50% reduction. If this was tolerated for 4 h, balloon frequency was reduced from 1:1 to 1:2 for 3–4 h, and then to 1:3 for 3–4 h before finally terminating IABP support and removing the catheter. This was done for all patients, with the weaning process taking 10–12 h. Where the catheter had been introduced into the femoral artery via a Gore-Tex sleeve, the sleeve was simply ligated and trimmed, leaving a short stump, otherwise the femoral artery was repaired by direct suture using 7/0 prolene. Criteria to begin weaning from the IABP were hemodynamic stability with signs of good cardiac output: normal blood pressure for age with central venous pressure (CVP) and left atrial pressure (LAP) < 10 mm Hg, improved myocardial contractility on echocardiography, substantially reduced inotropic requirement, usually enoximone and/or dobutamine at 5 µg/kg/min, satisfactory urine output (greater than 2 mL/kg/h), central/peripheral temperature gap not more than 2°C, and absence of metabolic acidosis. All patients received heparin infusion while on balloon pump, with dose adjustments to keep the activated partial thromboplastic time (APTT) 1.5 to 2 times the normal value.

All long-term survivors were followed up in the outpatient clinic with serial echocardiograms.

	Results

Top Abstract Introduction Patients and methods Results Comment Summary References

 
Table 1 summarizes the clinical status and outcome of the 14 patients in whom balloon deployment was deemed necessary in the postoperative period. Ten of 14 patients (71%) were successfully weaned from the IABP, of whom, 8 became long-term survivors. This represents 57% (8/14) of the patients receiving IABP therapy. There were 2 short-term survivors who died during the same hospital admission. Patient 13 died from extensive thrombosis of the superior vena cava and jugular veins 6 weeks after successful weaning from the IABP. The other (patient 14) suffered a possible balloon-related mesenteric infarction with ischemic colitis and fecal peritonitis. He died from overwhelming infection 4 weeks after undergoing laparotomy with colonic resection and ileostomy.

The 2 patients in whom the balloon was used prophylactically were both long-term survivors, whereas 2 out of the 5 who had initially failed to wean from cardiopulmonary bypass died (patients 3 and 10). Among the 3 patients who received the balloon in the intensive therapy unit (ITU) for sudden deterioration there was 1 long-term survivor (patient 8), 1 short-term survivor (patient 13), and 1 death (patient 5). There were 2 long-term survivors in the group of patients in whom the balloon was used for progressive deterioration, including patient 12, who had the IABP initiated on the seventh postoperative day and was ballooned for 10 days, 1 short-term survivor (patient 14), and 1 death (patient 9). Among both long-term and short-term survivors, the mean duration of balloon pump support was 127 h (range 12–260 h), while among those who died, the mean was 15 h (range 8–24 h).

Complications
In none of the patients was the balloon catheter removed prematurely as a result of a detected IABP-related complication incompatible with life. In retrospect, the mesenteric ischemia suffered by patient 14, although it was discovered 5 days after weaning from the IABP, may have been related to the IABP. There were no diagnostic indicators of this during the period of balloon pump use. Although loss of distal right limb pulses was detected in this patient soon after the balloon was inserted, there was no sign of acute limb ischemia, and pulses returned when hemodynamics improved. Chest radiograph confirmed the balloon was above L1.

Positive blood cultures were recorded in our first 2 patients, prompting a review of our antibiotic prophylaxis protocol. Mediastinitis did not occur in the 5 patients who had the balloon inserted via the ascending aorta and who had their chests closed only with silicone membrane for up to 5 days. There was one hemorrhagic complication requiring chest exploration 3 times. No specific bleeding was found on any occasion. No deterioration of renal function attributable to the IABP was encountered. On the contrary, urine output improved in all survivors as hemodynamics improved, and in the 3 patients who were undergoing peritoneal dialysis before the initiation of IABP, dialysis became unnecessary after 48 h of IABP use.

Figure 1 shows the pressure tracing of patient 2 at the start of IAB counterpulsation as augmentation is reduced from maximum to minimum. Even at maximum augmentation, suprasystolic augmentation is not achieved. This is frequently seen in patients under 2 years of age [10]. Nevertheless, even under these conditions, the pressure changes invoked by counterpulsation favor an increase in the diastolic pressure-time index, thereby augmenting myocardial oxygen supply, and a decrease in the tension-time index, thus diminishing myocardial oxygen demand [11]. We found that suprasystolic augmentation could often be achieved by active cooling to a core temperature of 34°C, which we did to suppress tachycardias above 200 beats/min. The combined effects of better tracking at lower heart rates and an element of induced peripheral vasoconstriction are the likely reasons for this. Regular serum lactate measurements were done to ensure that peripheral perfusion was adequate.

View larger version (57K): [in this window] [in a new window]   Fig 1. Arterial wave form of patient 2 at the start of intraaortic balloon counterpulsation as augmentation is reduced, though artificially quickly, from maximum (left) to minimum (right). Although suprasystolic augmentation is not achieved, the ‘area under the curve’ diminishes markedly.

View larger version (77K): [in this window] [in a new window]   Fig 2. Arterial wave form of patient 11 with IABP in 1:1 (left) and 1:2 (right) frequency. Suprasystolic diastolic augmentation is achieved as well as a lowered aortic end-diastolic pressure [‘presystolic dip’] (arrows).

Patient 10 underwent patch closure of ventricular septal and atrial septal defects with relief of right ventricular outflow tract obstruction. He could not be weaned from CPB because of persistent hypotension and elevated right atrial pressure. Intraoperative echocardiography showed a small, poorly contracting right ventricle. He was converted to bilateral superior cavopulmonary anastomoses with removal of the ventricular septal defect and atrial septal defect patches, and weaned from CPB on IABP and inotropes. His low cardiac output state persisted, and he died 9 h later. Autopsy was not performed.

Patient 5 suffered a cardiac arrest within 1 h of arriving in the ITU after undergoing superior cavopulmonary anastomosis, atrial septectomy, and extensive reconstruction of his branch pulmonary arteries. His chest was reopened for resuscitation and an IABP placed via the right femoral artery. He died 18 h later from progressive ventricular failure. Permission for postmortem examination was not granted.

Patient 9 underwent completion of Fontan and was weaned from cardiopulmonary bypass (CPB) on enoximone, dobutamine, and subsequently adrenaline. Escalating doses of inotropes during the succeeding 24 h resulted in initiation of IABP therapy, but the patient died 24 h later. Postmortem showed acute and chronic myocardial damage and a previously unappreciated drainage of pulmonary veins via a narrowed coronary sinus.

Follow-up
All the 8 long-term survivors were followed up with regular clinical and echocardiographic assessment. Follow-up ranged from 4 to 26 months (mean 18 months). All these patients are alive and well, and have shown improvement in ventricular function. One patient (No. 2) was reoperated 5 months later for supravalvular pulmonary stenosis produced by the intrapulmonary tunnel. The perioperative management was uneventful.

	Comment

Top Abstract Introduction Patients and methods Results Comment Summary References

 
Since the description of the concept of the IABP by Moulopoulos and associates in 1962 [12], and the first clinical application by Kantrowitz and associates in 1968 [13], the IABP has continued to develop and evolve, and it is now an accepted mode of supporting adults with left ventricular failure. Although balloon catheters and pumping consoles have been modified for pediatric use to respond to the small volumes and rapid heart rates encountered, the adoption of the technique to young children has met with variable success [2–7]. Early concerns about whether effective counterpulsation was achievable in the highly elastic and distensible aorta of young children have proved unfounded [2, 6]. Perhaps the major concern that has hindered the widespread use of the IABP in children is that in contradistinction to adults with coronary artery disease, who constitute the major users of IABP, children with congenital heart defects and severe LV failure are less likely to have preserved right ventricular and pulmonary function and, as such, may not be supportable with IABP. ECMO has been the most successful mode of circulatory support in children, with the Extracorporeal Life Support Organization (ELSO) registry recording 4% of all ECMO as initiated for postcardiotomy patients, with 44% of patients successfully weaned from ECMO [8, 9]. In this group of patients, cardiac failure is generally due to prolonged complicated surgery with extended cross-clamp times or preoperative ventricular dysfunction.

Intraaortic counterpulsation works by offloading the ventricle in the ejection phase of the cardiac cycle and increasing myocardial blood flow in the filling phase by diastolic augmentation. Hence, myocardial oxygen demand is reduced while oxygen availability is increased, providing optimal conditions for myocardial recovery from ischemic injury. Inotropic drugs tend to increase myocardial oxygen consumption, and using IABP allowed reduction of the doses of these drugs more quickly than would otherwise have been achieved [7].

Timing
The timing of balloon deployment is still a matter of clinical judgment and may be difficult, even though some useful guidelines have been suggested [3, 14]. In patients with severe preoperative ventricular dysfunction, or those who cannot be weaned from CPB, or who suddenly deteriorate after a good surgical repair, the decision to initiate IABP may be relatively straightforward. However, for progressive deterioration of ventricular function, the decision can be a more difficult one. In our series, the timing ranged from 24 h to the seventh postoperative day, highlighting the difficulty in decision making. We considered adrenaline at doses greater than 0.5 µg/kg/min as a strong indication for initiating IABP, but for patients who have had the Fontan procedure, the requirement to use even a low dose of adrenaline may prompt IABP use.

Complications
Excessive balloon length in small children can predispose them to cerebrovascular accidents and renal and mesenteric ischemia, which were common when balloon sizes were inappropriate. Mesenteric ischemia may present a difficult diagnostic problem, because the early signs of abdominal distension and ileus are common among postsurgical, ventilated patients [15]. This was probably the case with patient 13 in our series, who was found at laparotomy 5 days after successful weaning from the IABP to have ischemic large bowel with perforation and fecal peritonitis. It is not possible to dissociate this completely from the use of the balloon pump. A high index of suspicion may have helped to avert this problem.

Fontan procedure
There is a high incidence of failure to retrieve poor ventricular function after the Fontan procedure. At the Hospital for Sick Children, Toronto, only 1 of 9 children who required IABP therapy after the Fontan procedure survived (11%) [6]. Similarly there were no survivors (out of 2) at the Columbia Presbyterian Medical Center (New York, NY) [4]. In our series, 4 of 7 patients who had undergone the Fontan procedure were successfully weaned, although only 2 were long-term survivors, and 3 of the 4 deaths on IABP therapy were after the Fontan procedure. Theoretically, balloon pumping after the Fontan procedure should be beneficial by reducing afterload and end-diastolic and filling pressures and, thus, contribution to pulmonary vascular resistance. Myocardial oxygen supply is influenced favorably. However, this group of patients with pure ventricular failure is not the only cause of failure after the Fontan procedure. Clearly, there must be an exhaustive search for residual obstruction or other defects.

Deaths
In retrospect, patients 3 and 9 may not have survived with any form of circulatory support, but patient 5 may have benefited from earlier intervention. Even though it is not clear why patient 10 died, the attempt at biventricular repair was in retrospect inappropriate.

	Summary

Top Abstract Introduction Patients and methods Results Comment Summary References

 
Our overall survival rate (‘weaned from balloon’) of 71% (n = 14) compares well with the other published series: 56% (n = 9) [4] and 50% (n = 18) [5], though we found that experience aids in the identification of specific clinical indications that can predict successful or unsuccessful outcome.

Our choice in the use of IABP for the patients who could not be weaned from cardiopulmonary bypass was due to the fact that we do not have ECMO or left ventricular assist device (LVAD) facilities. IABP is not substitute for ECMO or LVAD. It is potentially useful support if started before there is an indication for ECMO or LVAD. Its main role is preventing ventricular deterioration. For this reason, it must be started well before ventricular function is not capable of sustaining the cardiac output. Beyond this point, it has no role to play, and its use too late will only discredit this potentially very useful technique.

	References

Top Abstract Introduction Patients and methods Results Comment Summary References

 

1. McEnany M.T., Kay H.R., Buckley M.J., et al. Clinical experience with intra aortic balloon pump in 728 patients. Circulation 1978;58(suppl 1):124-132.
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