Pulsatile Versus Nonpulsatile Cardiopulmonary Bypass Procedures in Neonates and Infants: From Bench to Clinical Practice

The effects of pulsatile versus nonpulsatile flow on cerebral pulsatility index, mean flow velocity at the middle cerebral artery, regional cerebral oxygen saturation, cerebral gaseous microemboli counts, and short-term clinical outcomes in patients undergoing congenital heart surgery

Objective

The objective of this retrospective review was to evaluate whether or not pulsatile flow improves cerebral hemodynamics and clinical outcomes in pediatric congenital cardiac surgery patients.

Methods

This retrospective study included 284 pediatric patients undergoing congenital cardiac surgery with cardiopulmonary bypass support utilizing nonpulsatile (n = 152) or pulsatile (n = 132) flow. Intraoperative cerebral gaseous microemboli counts, pulsatility index, and mean blood flow velocity at the right middle cerebral artery were assessed using transcranial Doppler ultrasound. Clinical outcomes were compared between groups.

Results

Patient demographics and cardiopulmonary bypass characteristics between groups were similar. Although the pulsatility index during aortic crossclamping was consistently higher in the pulsatile group (P < .05), a significant degree of pulsatility was also observed in the nonpulsatile group. No significant differences in mean cerebral blood flow velocity, regional cerebral oxygen saturation, or gaseous microemboli counts were observed between the perfusion modality groups. Clinical outcomes, including intubation duration, intensive care unit and hospital length of stay, and mortality within 180 days were similar between groups.

Conclusions

Although the pulsatility index was greater in the pulsatile group, other measures of intraoperative cerebral perfusion and short-term outcomes were similar to the nonpulsatile group. These findings suggest that while pulsatile perfusion represents a safe modality for cardiopulmonary bypass support, its use may not translate into detectably superior clinical outcomes.

A Randomized Clinical Trial of Perfusion Modalities in Pediatric Congenital Heart Surgery Patients

BACKGROUND

The objective of this randomized clinical trial was to investigate the effects of perfusion modalities on cerebral hemodynamics, vital organ injury, quantified by the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) Score, and clinical outcomes in risk-stratified congenital cardiac surgery patients.

METHODS

This randomized clinical trial included 159 consecutive congenital cardiac surgery patients in whom pulsatile (n = 83) or nonpulsatile (n = 76) perfusion was used. Cerebral hemodynamics were assessed using transcranial Doppler ultrasound. Multiple organ injury was quantified using the PELOD-2 score at 24, 48, and 72 hours. Clinical outcomes, including intubation time, intensive care unit length of stay (LOS), hospital LOS, and mortality, were also evaluated.

RESULTS

The Pulsatility Index at the middle cerebral artery and in the arterial line during aortic cross-clamping was consistently better maintained in the pulsatile group. Demographics and cardiopulmonary bypass characteristics were similar between the 2 groups. While risk stratification with The Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) Mortality Categories was similar between the groups, Mortality Categories 1 to 3 demonstrated more patients than Mortality Categories 4 and 5. There were no differences in clinical outcomes between the groups. The PELOD-2 scores showed a progressive improvement from 24 hours to 72 hours, but the results were not statistically different between the groups.

CONCLUSIONS

The Pulsatillity Index for the pulsatile group demonstrated a more physiologic pattern compared with the nonpulsatile group. While pulsatile perfusion did not increase plasma-free hemoglobin levels or microemboli delivery, it also did not demonstrate any improvements in clinical outcomes or PELOD-2 scores, suggesting that while pulsatile perfusion is a safe method, it not a "magic bullet" for congenital cardiac operations.

Frequency domain analysis and clinical outcomes of pulsatile and non-pulsatile blood flow energy during cardiopulmonary bypass

INTRODUCTION

The superiority of pulsatile perfusion during cardiopulmonary bypass remains controversial. We analyzed the frequency-domain characteristics and organ protection of pulsatile and nonpulsatile flow in adult patients with valvular disease.

METHODS

EEP and SHE were used to calculate blood flow energy in 60 patients. The Fast Fourier Transform was employed to analyze the power spectral density and power density ratio (Rvpd) of flow energy. Changes in endothelin-1, nitric oxide, interleukin-6,10, tumor necrotic factor, S100β, NSE, blood and urinary β2-microglobulin levels were investigated to assess the endothelial function, inflammatory reaction, kidney and brain injury during CPB.

RESULTS

EEP and SHE in PP group at each time point were 1.52-1.62 times and 2.03-2.22 times higher respectively compared with NP group. Power spectral density analysis demonstrated that the blood flow energy frequencies in each group were all within 40 Hz and the low frequency energy (0-5 Hz) was dominant in physiological perfusion (>90%). The energy ratio of 0-5 Hz at radial artery was significantly decreased compared with that of post arterial filter in PP (81% vs 64%) and NP (63% vs 37%) group. The power density ratio (Rvpd) was higher than that of NP in all frequency ranges at the radial artery (9.51 vs 4.68 vs 3.59) and arterial filter (3.87 vs 2.69 vs 2.38). The S100β, NSE Urinary and plasma β2-microglobulin level were significantly increased at 6 and 24 hours after surgery in two group, and significantly higher in group NP.

CONCLUSION

PP provided more energy than NP. The proportion of low frequency energy in the pulsatile or nonpulsatile flow is significantly reduced. The low-frequency energy is significantly attenuated during conduction to peripheral tissues in nonpulsatile flow. The surplus pulsatile energy influences the secretion of endothelial and inflammatory factors, and demonstrate better cerebral and kidney protective effect at the biological marker level.

Review Article: Comparison of perfusion modes on microcirculation during acute and chronic cardiac support: is there a difference?

Although heart-lung machines and cardiac assist devices have been used successfully for acute and chronic cardiac support for decades, controversies still remain concerning the benefits of pulsatile and non-pulsatile perfusion. The core of the debate is whether enough energy is generated by the artificial pulse to keep capillary beds open and cell metabolism stabilized during acute or chronic cardiac support. In other words, does artificial pulsatility exist in the microcirculation: small vessels of less than 100 μm in diameter? Many investigators have tried to use different tools and biomarkers to reflect directly or indirectly the state of the microcirculation when comparing the two different perfusion modes during acute and chronic cardiac support. However, the results are controversial. First, direct observation of the state of the microcirculation during acute and chronic cardiac support is limited; and reports concerning direct observation of the microcirculation with different perfusion modes in contemporary literature are rare. Secondly, different investigators have used their own criteria to define pulsatile flow. Therefore, it is necessary to develop more efficient methodologies, enabling direct observation of the microcirculation during acute and chronic cardiac support and also establish common criteria that will precisely quantify the pulsatile flow in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) levels. Using these critical parameters may explain how excess energy is created by pulsatile flow and maintains perfusion through the microcirculation by ensuring capillary patency. Perfusion (2007) 22, 115—119.

Why pulsatility still matters: a review of current knowledge

Continuous-flow left ventricular assist devices (LVAD) have become standard therapy option for patients with advanced heart failure. They offer several advantages over previously used pulsatile-flow LVADs, including improved durability, less surgical trauma, higher energy efficiency, and lower thrombogenicity. These benefits translate into better survival, lower frequency of adverse events, improved quality of life, and higher functional capacity of patients. However, mounting evidence shows unanticipated consequences of continuous-flow support, such as acquired aortic valve insufficiency and acquired von Willebrand syndrome. In this review article we discuss current evidence on differences between continuous and pulsatile mechanical circulatory support, with a focus on clinical implications and potential benefits of pulsatile flow.

A novel rotary pulsatile flow pump for cardiopulmonary bypass

It has been suggested that pulsatile blood flow is superior to continuous flow (CF) in cardiopulmonary bypass (CPB). However, adoption of pulsatile flow (PF) technology has been limited because of practicality and complexity of creating a consistent physiologic pulse. A pediatric pulsatile rotary ventricular pump (PRVP) was designed to address this problem. We evaluated the PRVP in an animal model and determined its ability to generate PF during CPB. The PRVP (modified peristaltic pump, with tapering of the outlet of the pump chamber) was tested in four piglets (10-12 kg). Cannulation was performed with right atrial and aortic cannulae, and pressure sensors were inserted into the femoral arteries. Pressure curves were obtained at different levels of flow and compared with both the animal's baseline physiologic function and a CF roller pump. Pressure and flow waveforms demonstrated significant pulsatility in the PRVP setup compared with CF at all tested conditions. Measurement of hemodynamic energy data, including the percentage pulsatile energy and the surplus hydraulic energy, also revealed a significant increase in pulsatility with the PRVP (p < 0.001). The PRVP creates physiologically significant PF, similar to the pulsatility of a native heart, and has the potential to be easily implemented in pediatric CPB.

Cerebral aspects of neonatal extracorporeal membrane oxygenation: a review

BACKGROUND

Neonatal extracorporeal membrane oxygenation (ECMO) is a lifesaving therapeutic approach in newborns suffering from severe, but potentially reversible, respiratory insufficiency, mostly complicated by neonatal persistent pulmonary hypertension. However, cerebral damage, intracerebral hemorrhage as well as ischemia belong to the most devastating complications of ECMO.

OBJECTIVES

The objectives are to give insights into what is known from the literature concerning cerebral damage related to neonatal ECMO treatment for pulmonary reasons.

METHODS

A short introduction to ECMO indications and technical aspects of ECMO are provided for a better understanding of the process. The remainder of this review focuses on outcome and especially on (potential) risk factors for cerebral hemorrhage and ischemia during ECMO treatment.

RESULTS

Although neonatal ECMO treatment shows improved outcome compared to conservative treatment in cases of severe respiratory insufficiency, it is related to disturbances in various aspects of neurodevelopmental outcome. Risk factors for cerebral damage are either related to the patient's disease, EMCO treatment itself, or a combination of both.

CONCLUSION

It is of ongoing importance to further understand pathophysiological mechanisms resulting in cerebral hemorrhage and ischemia due to ECMO and to develop neuroprotective strategies and approaches.

Comparison of parameters for detection of splanchnic hypoxia in children undergoing cardiopulmonary bypass with pulsatile versus nonpulsatile normothermia or hypothermia during congenital heart surgeries

The aim of this study is to evaluate gastric mucosal oxygenation together with whole-body oxygen changes in infants undergoing congenital heart surgery with cardiopulmonary bypass (CPB) procedure and the use of either pulsatile or nonpulsatile mode of perfusion with normothermia and pulsatile or nonpulsatile moderate hypothermia. Sixty infants undergoing congenital cardiac surgery were randomized into four groups as: nonpulsatile normothermia CPB (NNCPB, n = 15), pulsatile normothermia CPB (PNCPB, n = 15), nonpulsatile moderate hypothermia CPB (NHCPB, n = 15), and pulsatile moderate hypothermia CPB (PHCPB, n = 15) groups. In NNCPB and PNCPB groups, mild hypothermia was used (35°C), whereas in NHCPB and PHCPB groups, moderate hypothermia (28°C) was used. Gastric intramucosal pH (pHi), whole-body oxygen delivery (DO(2)) and consumption (VO(2)), and whole-body oxygen extraction fraction were measured at sequential time points intraoperatively and up to 2 h postoperatively. The measurement of continuous tonometry data was collected at desired intervals. The values of DO(2), VO(2), and whole-body oxygen extraction fraction were not different between groups before CPB and during CPB, whereas the PNCPB group showed higher values of DO(2), VO(2), and whole-body oxygen extraction fraction compared to the other groups at the measurement levels of 20 and 60 min after aortic cross clamp, end of CPB, and 2 h after CPB (P < 0.0001). Between groups, no difference was observed for pHi, lactate, and cardiac index values (P > 0.05). This study shows that the use of normothermic pulsatile perfusion (35°C) provides better gastric mucosal oxygenation as compared to other perfusion strategies in neonates and infants undergoing congenital heart surgery with CPB procedures.

Benefits of pulsatile flow in pediatric cardiopulmonary bypass procedures: from conception to conduction

This review on the benefits of pulsatile flow includes not only experimental and clinical data, but also attempts to further illuminate the major factors as to why this debate has continued during the past 55 years. Every single component of the cardiopulmonary bypass (CPB) circuitry is equally important for generating adequate quality of pulsatility, not only the pump. Therefore, translational research is a necessity to select the best components for the circuit. Generation of pulsatile flow depends on an energy gradient; precise quantification in terms of hemodynamic energy levels is, therefore, a necessity, not an option. Comparisons between perfusion modes should be done after these basic steps have been taken. We have also included experimental and clinical data for direct comparisons between the perfusion modes. In addition, we included several suggestions for future clinical trials for other interested investigators.

Improved cerebral oxygen saturation and blood flow pulsatility with pulsatile perfusion during pediatric cardiopulmonary bypass

Brain monitoring techniques near-infrared spectroscopy (NIRS) and transcranial Doppler (TCD) ultrasound were used in pediatric patients undergoing cardiopulmonary bypass for congenital heart defect (CHD) repair to analyze the effect of pulsatile or nonpulsatile flow on brain protection. Regional cerebral oxygen saturation (rSO2) and cerebrovascular pulsatility index (PI) were measured by NIRS and TCD, respectively, in 111 pediatric patients undergoing bypass for CHD repair randomized to pulsatile (n = 77) or nonpulsatile (n = 34) perfusion. No significant differences in demographic and intraoperative data, including surgical risk stratification, existed between groups. Patients undergoing pulsatile perfusion had numerically lower decreases in rSO2 from baseline for all time points analyzed compared with the nonpulsatile group, with significant ∼12% lower decreases at 40 and 60 min after crossclamp. Patients undergoing pulsatile perfusion had numerically lower decreases in PI from baseline for the majority of time points compared with the nonpulsatile group, with significant ∼30% lower decreases between 5 and 40 min after crossclamp. Pulsatile flow has advantages over nonpulsatile flow as measured by NIRS and TCD, especially at advanced time points, which may improve postoperative neurodevelopmental outcomes.

Pediatric Cardiopulmonary Bypass

This current review describes how components of the cardiopulmonary bypass (CPB) circuit are selected and examines the benefits of pulsatile perfusion for use during CPB. Pulsatile flow generates significantly greater surplus hemodynamic energy (SHE) than nonpulsatile flow; higher SHE values have been associated with better microcirculation perfusion, lower rates of systemic inflammatory response, and better vital organ protection. Pulsatile perfusion may have a positive effect on clinical outcomes, play a role in preserving homeostasis, and help to decrease morbidity associated with CPB.

Evaluation of perfusion modes on vital organ recovery and thyroid hormone homeostasis in pediatric patients undergoing cardiopulmonary bypass

The objectives of this study were: (i) to evaluate the effects of perfusion modes (pulsatile vs. nonpulsatile) on vital organs recovery and (ii) to investigate the influences of two different perfusion modes on the homeostasis of thyroid hormones in pediatric patients undergoing cardiopulmonary bypass (CPB) procedures. Two hundred and eighty-nine consecutive pediatric patients undergoing open heart surgery for repair of congenital heart disease were prospectively entered into the study and were randomly assigned to two groups: the pulsatile perfusion group (Group P, n = 208) and the nonpulsatile perfusion group (Group NP, n = 81). All patients received identical surgical, perfusional, and postoperative care. Study parameters included total drainage, mean urine output in the intensive care unit (ICU), intubation time, duration of ICU and hospital stay, the need for inotropic support, pre- and postoperative enzyme levels (ALT [alanine aminotransaminase] and AST [aspartate aminotransaminase]), c-reactive protein, lactate, albumin, blood count (leukocytes, hematocrit, platelets), creatinine levels, and thyroid hormones (thyroid stimulating hormone [TSH], FT(3) [free triiodothyronine], FT(4) [free thyroxine]). All patients survived the perioperative and postoperative periods. There were no statistically significant differences in either preoperative or operative parameters between the two groups. Group P, compared to Group NP, required significantly less inotropic support, had a shorter intubation period, higher urine output in ICU, and shorter duration of ICU and hospital stay. Lower lactate levels and higher albumin levels were observed in Group P and there were no significant differences in creatinine, enzyme levels, blood counts, or drainage amounts between two groups. TSH, Total T(3) , Total T(4) , and FT(3) , FT(4) levels were markedly reduced versus their preoperative values in both groups. FT(3) and FT(4) levels were reduced significantly further in the nonpulsatile group both during CPB and at 72 h postoperation. The results of this study confirm our opinion that pulsatile perfusion leads to better vital organ recovery and clinical outcomes in the early postoperative period as compared to nonpulsatile perfusion in pediatric patients undergoing CPB cardiac surgery. The plasma concentrations of thyroid hormones are dramatically reduced during and after CPB, but pulsatile perfusion seems to have a protective effect of thyroid hormone homeostasis compared to nonpulsatile perfusion.

Measurement of hemodynamic energy at different vessels in an adult swine model

Extra hemodynamic energy is one of the major benefits of pulsatile flow, improving blood flow to vital organs. But most (80%) of the hemodynamic energy generated from pulsatile flow is damped by the extracorporeal circuit. Most models devised to minimize hemodynamic energy loss have been in vitro pediatric models. The purpose of this study was to measure hemodynamic energy in different vessels of different organs with an in vivo adult swine model. An extracorporeal circuit was constructed for seven Yorkshire swine using a pulsatile pump (Twin-Pulse Life Support). The mean arterial pressure (MAP), energy equivalent pressure (EEP), and surplus hemodynamic energy (SHE) at the renal artery, carotid artery, aortic cannula site, and postoxygenator site were measured simultaneously before starting the pump and at the pump rates of 25, 35, and 45 bpm. The MAP of the renal or carotid artery was 40.0%-51.2% of the postoxygenator site. The EEP and SHE of both arteries were 11.6%-13.0% and 5.5%-7.4% of the postoxygenator site, respectively. The MAP and EEP of both arteries after starting the pump were lower than at baseline. The SHE of the renal artery after starting the pump was significantly higher than at baseline. The SHE of the carotid artery increased substantially after starting the pump although not statistically significantly. There was a significant hemodynamic energy loss in both arterial sites compared with the postoxygenator site. Also, a difference in hemodynamic energy loss was observed in vessel-to-vessel or vessel-to-circuit site comparison. This difference creates a bias in studying pulsatility and its effects. Therefore, the measurement method of hemodynamic energy must be standardized and the measurement site clarified to yield accurate study results.

In vitro characterization and performance testing of the ension pediatric cardiopulmonary assist system

In the last 40 years, mechanical circulatory support devices have become an effective option for the treatment of end-stage heart failure in adults. Few possibilities, however, are available for pediatric cardiopulmonary support. Ension Inc. (Pittsburgh, PA) is developing a pediatric cardiopulmonary assist system (pCAS) intended to address the limitations of existing devices used for this patient population. The pCAS device is an integrated unit containing an oxygenator and pump within a single casing, significantly reducing the size and blood-contacting surface area in comparison to current devices. Prototype pCAS devices produce appropriate flows and pressures while minimizing priming volume and preparation time. The pCAS was tested on a mock circulation designed to approximate the hemodynamic parameters of a small infant using a 10-Fr. extracorporeal membrane oxygenation inflow cannula and an 8-Fr. extracorporeal membrane oxygenation outflow cannula. Revision 4 of the device provided a flow rate of 0.42 L/min at 6,500 RPM. Revision 5, featuring improved impeller and diffuser designs, provided a flow rate of 0.57 L/min at 5,000 RPM. The performance tests indicate that for this cannulae combination, the pCAS pump is capable of delivering sufficient flows for patients <5 kg.

A novel, low cost, disposable, pediatric pulsatile rotary ventricular pump for cardiac surgery that provides a physiological flow pattern

Research is underway to develop a novel, low cost, disposable pediatric pulsatile rotary ventricular pump (PRVP) for cardiac surgery that provides a physiological flow pattern. This is believed to offer reduced morbidity and risk exposure within this population. The PRVP will have a durable design suitable for use in short- to mid-length prolonged support after surgery without changing pumps. The design is based on proprietary MC3 technology which provides variable pumping volume per stroke, thereby allowing the pump to respond to hemodynamic status changes of the patient. The novel pump design also possesses safety advantages that prevent retrograde flow, and maintain safe circuit pressures upon occlusion of the inlet and outlet tubing. The design is ideal for simple, safe and natural flow support. Computational methods have been developed that predict output for pump chambers of varying geometry. A scaled chamber and pump head (diameter = 4 in) were prototyped to demonstrate target performance for pediatrics (2 L/min at 100 rpm). A novel means of creating a pulsatile flow and pressure output at constant RPM was developed and demonstrated to create significant surplus hydraulic energy (>10%) in a simplified mock patient circuit.

Effect of Continuous and Pulsatile Flow Left Ventricular Assist on Pulsatility in a Pediatric Animal Model of Left Ventricular Dysfunction: Pilot Observations

Pediatric ventricular assist devices are being developed that can produce pulsatile flow (PF) or continuous flow (CF). An important aspect of choosing between these two modes is understanding the consequences of each mode on pediatric vascular pulsatility. Differences in vascular pulsatility generated by PF and CF operation of the 3-inch pediatric cardiopulmonary assist system (pCAS, Ension, Inc., Pittsburgh, PA) were investigated while providing left atrium-to-aorta left ventricular assist (LVA), using an infant animal model of left ventricular dysfunction. Hemodynamic data were digitally recorded with the pCAS providing LVA at incremental flow rates while operating in continuous mode, pulsatile mode at 100 bpm, and pulsatile mode at 140 bpm. These data were used to calculate vascular input impedance (Zart), energy equivalent pressure, and surplus hemodynamic energy as indices of pulsatility for partial (50% of maximum) and maximum LVA flow. Both CF and PF LVA by the pCAS resulted in favorable hemodynamic rectification of left ventricular dysfunction while generating equivalent flows. PF LVA maintained a greater degree of pulsatility compared with CF, as evidenced by increasing energy equivalent pressure and a lesser drop in surplus hemodynamic energy with increasing pCAS flow. Differences in Zart modulus and phase were indiscernible. The selection of flow mode may have long-term consequences on Zart and end-organ perfusion affecting clinical outcomes in pediatric patients.

Comparison of hollow-fiber membrane oxygenators with different perfusion modes during normothermic and hypothermic CPB in a simulated neonatal model

Purpose: The objectives of this investigation were (1) to compare two hollow-fiber membrane oxygenators (Capiox Baby RX versus Lilliput 1-D901) in terms of pressure drops and surplus hemodynamic energy (SHE) during normothermic and hypothermic cardiopulmonary bypass (CPB) in a simulated neonatal model; and (2) to evaluate pulsatile and non-pulsatile perfusion modes for each oxygenator in terms of SHE levels.

Methods: In a simulated patient, CPB was initiated at a constant pump flow rate of 500 mL/min. The circuit was primed with fresh bovine blood. After 5 min of normothermic CPB, the pseudo-patient was cooled down to 25°C for 10 min followed by 30 min of hypothermic CPB. The pseudo-patient then underwent 10 min of rewarming and 5 min of normothermic CPB. At each experimental site (pre- and post-oxygenator and pre-aortic cannula), SHE was calculated using the following formula {SHE (ergs/cm3) = 1332 [((ffpdt)/(ffdt))-mean arterial pressure]} (f = pump flow and p = pressure). A linear mixed-effects model that accounts for the correlation among repeated measurements was fit to the data to assess differences in SHE between oxygenators, pumps, and sites. Tukey’s multiple comparison procedure was used to adjust p-values for post-hoc pairwise comparisons.

Results: The pressure drops in the Capiox group compared to the Lilliput group were significantly lower during hypothermic non-pulsatile (21.3∓0.5 versus 50.7∓0.9 mmHg, p B < 0.001) and pulsatile (22∓0.0 versus 53.3∓0.5 mmHg, p < 0.001) perfusion, respectively. Surplus hemodynamic energy levels were significantly higher in the pulsatile group compared to the non-pulsatile group, with Capiox (1655∓92 versus 10 008∓1370 ergs/cm3, p < 0.001) or Lilliput (1506∓112 versus 7531∓483 ergs/cm3, p < 0.001) oxygenators. During normothermic CPB, both oxygenators had patterns similar to those observed under hypothermic conditions.

Conclusions: The Capiox oxygenator had a significantly lower pressure drop in both pulsatile and non-pulsatile perfusion modes. For each oxygenator, the SHE levels were significantly higher in the pulsatile mode.

Quantification of Perfusion Modes in Terms of Surplus Hemodynamic Energy Levels in a Simulated Pediatric CPB Model

The objective of this investigation was to compare pulsatile versus nonpulsatile perfusion modes in terms of surplus hemodynamic energy (SHE) levels during cardiopulmonary bypass (CPB) in a simulated neonatal model. The extracorporeal circuit consisted of a Jostra HL-20 heart-lung machine (for both pulsatile and nonpulsatile modes of perfusion), a Capiox Baby RX hollow-fiber membrane oxygenator, a Capiox pediatric arterial filter, 5 feet of arterial tubing and 6 feet of venous tubing with a quarter-inch diameter. The circuit was primed with a lactated Ringers solution. The systemic resistance of a pseudo-patient (mean weight, 3 kg) was simulated by placing a clamp at the end of the arterial line. The pseudo-patient was subjected to five pump flow rates in the 400 to 800 ml/min range. During pulsatile perfusion, the pump rate was kept constant at 120 bpm. Pressure waveforms were recorded at the preoxygenator, postoxygenator, and preaortic cannula sites. SHE was calculated by use of the following formula {SHE (ergs/cm) = 1,332 [((integral fpdt) / (integral fdt)) - Mean Arterial Pressure]} (f = pump flow and p = pressure). A total of 60 experiments were performed (n = 6 for nonpulsatile and n = 6 for pulsatile) at each of the five flow rates. A linear mixed-effects model, which accounts for the correlation among repeated measurements, was fit to the data to assess differences in SHE between flows, pumps, and sites. The Tukey multiple comparison procedure was used to adjust p values for post hoc pairwise comparisons. With a pump flow rate of 400 ml/min, pulsatile flow generated significantly higher surplus hemodynamic energy levels at the preoxygenator site (23,421 +/- 2,068 ergs/cm vs. 4,154 +/- 331 ergs/cm, p < 0.0001), the postoxygenator site (18,784 +/- 1,557 ergs/cm vs. 3,383 +/- 317 ergs/cm, p < 0.0001), and the precannula site (6,324 +/- 772 ergs/cm vs. 1,320 +/- 91 ergs/cm, p < 0.0001), compared with the nonpulsatile group. Pulsatile flow produced higher SHE levels at all other pump flow rates. The Jostra HL-20 roller pump generated significantly higher SHE levels in the pulsatile mode when compared with the nonpulsatile mode at all five pump flow rates.

An Evaluation of the Benefits of Pulsatile versus Nonpulsatile Perfusion during Cardiopulmonary Bypass Procedures in Pediatric and Adult Cardiac Patients

The controversy over the benefits of pulsatile and nonpulsatile flow during cardiopulmonary bypass procedures continues. The objective of this investigation was to review the literature in order to clarify the truths and dispel the myths regarding the mode of perfusion used during open-heart surgery in pediatric and adult patients. The Google and Medline databases were used to search all of the literature on pulsatile vs. nonpulsatile perfusion published between 1952 and 2006. We found 194 articles related to this topic in the literature. Based on our literature search, we determined that pulsatile flow significantly improved blood flow of the vital organs including brain, heart, liver, and pancreas; reduced the systemic inflammatory response syndrome; and decreased the incidence of postoperative deaths in pediatric and adult patients. We also found evidence that pulsatile flow significantly improved vital organ recovery in several types of animal models when compared with nonpulsatile perfusion. Several investigators have also shown that pulsatile flow generates more hemodynamic energy, which maintains better microcirculation compared with nonpulsatile flow. These results clearly suggest that pulsatile flow is superior to nonpulsatile flow during and after open-heart surgery in pediatric and adult patients.