Hypothermic Low-flow Cardiopulmonary Bypass Research Articles

Pseudoaneurysm following a neonatal coarctation repair; a dreadful complication.

Aneurysms of descending thoracic aorta following surgical repair of coarctation have been reported in literature. Almost always, they are seen in repairs involving prosthetic patch aortoplasty. We report a neonate who underwent resection and an extended end to end anastomosis repair of coarctation and subsequently developed a huge pseudoaneurysm at a 3-month follow-up. He underwent a repair of the same through a sternotomy approach under hypothermic low flow cardiopulmonary bypass. An autologous pericardial patch aortoplasty was done successfully.

Ulinastatin Protects against Acute Kidney Injury in Infant Piglets Model Undergoing Surgery on Hypothermic Low-Flow Cardiopulmonary Bypass.

ObjectiveInfants are more vulnerable to kidney injuries induced by inflammatory response syndrome and ischemia-reperfusion injury following cardiopulmonary bypass especially with prolonged hypothermic low-flow (HLF). This study aims to evaluate the protective role of ulinastatin, an anti-inflammatory agent, against acute kidney injuries in infant piglets model undergoing surgery on HLF cardiopulmonary bypass.MethodsEighteen general-type infant piglets were randomly separated into the ulinastatin group (Group U, n = 6), the control group (Group C, n = 6), and the sham operation group (Group S, n = 6), and anaesthetized. The groups U and C received following experimental procedure: median thoracotomy, routine CPB and HLF, and finally weaned from CPB. The group S only underwent sham median thoracotomy. Ulinastatin at a dose of 5,000 units/kg body weight and a certain volume of saline were administrated to animals of the groups U and C at the beginning of CPB and at aortic declamping, respectively. Venous blood samples were collected at 3 different time points: after anesthesia induction in all experimental groups, 5 minutes, and 120 minutes after CPB in the Groups U and C. Markers for inflammation and acute kidney injury were tested in the collected plasma. N-acetyl-β-D-glucosaminidase (NAG) from urine, markers of oxidative stress injury and TUNEL-positive cells in kidney tissues were also detected.ResultsThe expressions of plasma inflammatory markers and acute kidney injury markers increased both in Group U and Group C at 5 min and 120 min after CPB. Also, numbers of TUNEL-positive cells and oxidative stress markers in kidney rose in both groups. At the time point of 120-min after CPB, compared with the Group C, some plasma inflammatory and acute kidney injury markers as well as TUNEL-positive cells and oxidative stress markers in kidney were significantly reduced in the Group U. Histologic analyses showed that HLF promoted acute tubular necrosis and dilatation.ConclusionsHLF cardiopulmonary bypass surgery could intensify systemic inflammatory responses and oxidative stress on infant piglets, thus causing acute kidney injury. Ulinastatin might reduce such inflammatory response and oxidative stress and the extent of kidney injury.

Effects of pulmonary artery perfusion with urinary trypsin inhibitor as a lung protective strategy under hypothermic low-flow cardiopulmonary bypass in an infant piglet model

This study aimed to evaluate the effects of pulmonary artery perfusion with a urinary trypsin inhibitor (UTI) as a lung protective strategy in order to provide an experimental basis for immature lung clinical protective strategies on deep hypothermia with low-flow (DHLF) cardiopulmonary bypass (CPB)-induced pulmonary injury in an infant piglet model. The piglets (n=15), aged 18.7±0.3 days, weight 4.48±0.21kg, were randomly divided into 3 groups, with 5 piglets in each group: the control group, the pulmonary artery perfusion without UTI group (Group P) and the pulmonary artery perfusion with UTI group (Group U). The levels of the cytokines tumour necrosis factor-α, myeloperoxidase, malondialdehyde and interleukin-10 (TNF-α, MPO, MDA and IL-10) in pulmonary venous serum and lung tissue and the activity of NF-kappa B in lung tissue were measured by enzyme-linked immunosorbent assay (ELISA) and electrophoresis mobility shift assay (EMSA), respectively. After DHLF-CPB, all of the piglets demonstrated a state of lung injury as a deterioration of lung function indices, lung injury scores, pulmonary ultrastructure changes, expression of TNF-α, MPO, MDA and IL-10 and the activities of nuclear factor-kappa B (NF-κB), while pulmonary artery perfusion with UTI significantly ameliorated lung function and histopathological changes, with greatly decreased serum levels of TNF-α and MPO compared to the other two groups. Also, we found an increase in the level of IL-10 in Group U lungs compared with that in Group P lungs, which correlated with a strong inhibition in the activity of NF-κB. Pulmonary artery perfusion with UTI ameliorated the DHLF-induced immature pulmonary injury in the lungs via a reduction of pro-inflammatory cytokine expression and up-regulated levels of IL-10 by inhibiting the activity of NF-κB.

Invited Commentary

Fabiani and colleagues [1Fabiani J.-N. Raux M. Alsac J.-M. et al.Deep hypothermia and low flow for surgery for abdominal or extraperitoneal tumors with cavoatrial extension.Ann Thorac Surgery. 2013; 95: 2036-2041Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar] report the removal of tumor thrombus into the inferior vena cava (IVC) by use of deep hypothermic low-flow cardiopulmonary bypass (CPB). There was no mortality at the 1-year follow-up of these patients. The authors conclude that this technique allows for safe and complete removal of tumor thrombus into the IVC while providing organ protection. It is not clear whether the authors placed an IVC filter when the IVC was partially obstructed at the end of the operation to avoid pulmonary emboli. Perhaps the only limitation of this report is the limited number of patients, making it difficult to standardize the surgical approach for removal of these tumors. The prevalence of patients with extensive IVC tumor thrombus is very low. However, the surgical procedure is associated with high morbidity and mortality (over 8%) when deep hypothermic circulatory arrest is used [2Shuch B. Crispen P.L. Leibovich B.C. et al.Cardiopulmonary bypass and renal cell carcinoma with level IV tumor thrombus: can deep hypothermic circulatory arrest limit perioperative mortality?.BJU Int. 2010; 107: 724-728Crossref Scopus (42) Google Scholar]. This underscores the importance of the experience of the surgical team performing the operation. Some centers, such as ours, have gone to great lengths to avoid CPB altogether, using innovative technical maneuvers [3Ciancio G. Gonzalez J. Shirodkar S.P. Angulo J.C. Soloway M.S. Liver transplantation techniques for the surgical management of renal cell carcinoma with tumor thrombus in the inferior vena cava: step-by-step description.Eur Urol. 2010; 59: 401-406Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar, 4Ciancio G. Shirodkar S.P. Soloway M.S. Livingstone A.S. Barron M. Salerno T.A. Renal carcinoma with supradiaphragmatic tumor thrombus: avoiding sternotomy and cardiopulmonary bypass.Ann Thorac Surg. 2010; 89: 505-510Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar]. The best approach for such patients would be to refer them to centers with extensive experience with these complex operations, where the operation can be tailored to the specific location of the tumor, with use of a multidisciplinary surgical team that includes a urologic oncologist, a cardiothoracic surgeon, and an anesthesiologist with expertise in transesophageal echocardiography. It is important to determine the exact extension of the tumor thrombus and involvement of the IVC wall with imaging technology. This helps the surgeons to individualize the approach, the extent of expected surgical procedure, and the need for CPB. These tumors with vascular invasion into the IVC continue to be a challenge to the surgical team. It is clear that complete excision of the tumor, including removal of involved IVC, with negative margins, as described by the authors, allows the best chance for patient survival. Deep Hypothermia and Low Flow for Surgery for Abdominal or Extraperitoneal Tumors With Cavoatrial ExtensionThe Annals of Thoracic SurgeryVol. 95Issue 6PreviewSurgical treatment of retroperitoneal tumors with cavoatrial involvement can be challenging. Completeness of resection of the cava tumor extension is crucial for the patient's survival. We report a monocentric experience with the use of cardiopulmonary bypass and deep hypothermic low flow for the surgical resection of caval and atrial involvement of retroperitoneal tumors. Full-Text PDF

Ulinastatin as a neuroprotective and anti‐inflammatory agent in infant piglets model undergoing surgery on hypothermic low‐flow cardiopulmonary bypass

Infants are potentially more susceptible to brain injury mediated via cell death attributed to cardiopulmonary bypass (CPB) especially with prolonged hypothermic low flow (HLF). We hypothesized that a human urinary protease inhibitor (ulinastatin), by its anti-inflammatory effect, would reduce central nervous system (CNS) injury during HLF. Fifteen general-type infant piglets were randomized to ulinastatin group (group U, n = 5), control group (group C, n = 5), and sham operation group (group S, n = 5). Routine CPB was established after median thoracotomy in group U and C under anesthesia. When the temperature of infant piglets dropped down to 25 °C, low-flow CPB (50 ml·kg(-1) ·min(-1) ) was instituted. After 120 min of aortic cross-clamping and 20- to 30-min rewarming, the aortic cross-clamp was removed and finally the piglet was weaned from CPB. Five thousand units per killogram of ulinastatin and equivalently normal saline were, respectively, given at the beginning of and at aortic declamping in group U and group C. group S just received sham median thoracotomy. Venous blood samples were taken immediately after anesthesia induction in all three groups, 5- and 120-min post CPB in both group U and C, respectively; plasma markers of inflammation and CNS injury were compared. Pathology results of hippocampus were observed by light microscopy. Statistically significant differences between group C and U were noted in the expression of inflammatory markers such as IL-10, TNF-α and neuron-specific enolase at 120-min post CPB. Brain injuries were observed in both groups (index cases and controls) and were milder in group U. In our study, HLF CPB on infant piglets resulted in brain injury, and ulinastatin might reduce the extent of such injury.

Brain injury caused by deep hypothermic low-flow cardiopulmonary bypass surgery, an experimental study on piglets

Objective To evaluate the effect and mechanisms of prolonged deep hypothermic low-flow cardiopulmonary bypass (CPB) cardiac surgery to the immature brain on piglets. Methods 15 Beijing Landrace piglets were divided into study group (n=10) and control group (n=5).Routine CPB was established after median thoracotomy in study group under anesthesia.Lowflow CPB(50 ml·kg-1·min-1)was started when the temperature of the animal dropped down to 25 ℃.The aorta was reopened after 120 min cross-clamping.Brain hippocampus tissues were harvested after 120 min following CPB ceased.In control group,hippocampus tissues were harvested after median thoracotomy under anesthesia.In study group,venous blood samples were taken immediately after anesthesia induction (T1),5 min (T2) and 120 min (T3) after the CPB shutdown,and interleukin (IL)-6,tumor necrosis factor (TNF)-α were tested through enzyme-linked immunosorbent assay(ELISA).In both groups,HE staining for pathological examination of brain hippocampus tissues was adopted; and hippocampus tissues homogenates,contents of neuron-specific enolase (NSE),S100 protein β subtypes (S100β) were detected by ELISA method.Results 1 piglet from study group was died by heart arrest after CPB;the other 9 piglets in study group and all 5 in control group completed to the end of the experiment.In study group,compared with T1,IL-6,TNF-α were increased by 7.01％(P＜0.05),3.52％(P＜0.05)in T2,and by 5.10％(P＜0.05),1.47％(P＞0.05)in T3.Compared with control group,study group showed pathological changes of brain damage,and NSE,S100β were also increased by 40.08％(P＜0.05)、29.66％(P＜0.05). Conclusions Deep hypothermic low-flow CPB would result in brain injury on piglets and its key mechanism might be inflammatory injury. Key words: Hypothermic low-flow; Cardiopulmonary bypass; Cardiac surgery; Brain injury; Piglets

Resternotomy Using Hypothermic Arrest

Resternotomy during closed chest cardiopulmonary bypass in hypothermia with or without circulatory arrest has been the preferred method for cardiac reoperations with adherent structures to the sternum. Here, we report our experience with this method and the effects of omitting ventricular decompression during the cooling procedure. Twenty reoperations were performed in 19 patients. In half (n = 10) of the procedures aortic regurgitation was present. Cardiopulmonary bypass was instituted in all patients before resternotomy, and the re-entry into the chest was performed either under hypothermic low-flow cardiopulmonary bypass or circulatory arrest. The reason for this choice of technique was adherent structures to the sternum posing a substantial risk for rupture during resternotomy in all patients. Rupture upon re-entry into the chest occurred in five operations. No patient died due to re-entry injury. The overall hospital mortality was 15%. No differences in postoperative outcomes including heart failure, biochemical markers indicating myocardial damage, and three-month follow-up assessment of cardiac function were found between patients with aortic regurgitation and patients without aortic regurgitation. Based on our experience, omitting ventricular decompression in resternotomy in hypothermia and arrested circulation or low-flow cardiopulmonary bypass can be safely used, and the presence of aortic regurgitation does not seem to influence the outcome.

Primary Repair of Infracardiac Total Anomalous Pulmonary Venous Connection Using a Modified Sutureless Technique

Primary repair of infracardiac total anomalous pulmonary venous connection is associated with a significant risk of recurrent pulmonary venous obstruction. Herein we describe a technique of primary repair in which a modified sutureless anastomosis is constructed by suturing the left atrium to the posterior mediastinal pleura that surrounds the pulmonary venous confluence.

Brain oxygen and metabolism is dependent on the rate of low-flow cardiopulmonary bypass following circulatory arrest in newborn piglets☆

To determine the optimum rate of low-flow hypothermic cardiopulmonary bypass (LF), following circulatory arrest (DHCA) on brain oxygenation (bO(2)), extracellular dopamine (DA), phosphorylation of select neuroregulatory proteins responsible for neuronal injury, and survival following ischemic brain injury: CREB, Erk1/2, Akt, Bcl-2, and Bax. The piglets were placed on cardiopulmonary bypass (CPB) and cooled to 18 degrees C. They were then subjected to 30 min of DHCA followed by 1h of LF at 20, 50, or 80 ml/(kg/min), rewarmed, separated from CPB, and maintained for 2h. The bO(2) was measured by quenching of phosphorescence; DA by microdialysis; phosphorylation of CREB, ERK1/2, Akt, Bcl-2, and Bax by Western blots. The results are means+/-SD for seven experiments. Pre-bypass bO(2) was 47.4+/-4.2 mmHg and decreased to 1.9+/-0.8 mmHg during DHCA. At the end of LF at 20, 50, and 80 ml/(kg/min), bO(2) was 11.8+/-1.6, 26+/-1.8, and 33.9+/-2.6 mmHg, respectively. The DA increased 510-fold relative to control (p<0.001) by 15 min of LF-20 with maximum increase occurring at 45 min. With LF-50, increase in DA was not statistically significant and no increase was observed when LF-80 was used. Bcl-2 immunoreactivity increased after LF-50 and LF-80 (140+/-14.5%, p<0.05 and 202+/-34%, p<0.05, respectively). Neither flow increased Bax immunoreactivity. The ratio of Bcl-2/Bax, pCREB, pAkt, pErk increased significantly with increasing the flow rate of LF. The protective effect of LF following DHCA on brain metabolism is dependent on the flow rate. Flow-dependent increase in pCREB, pErk1/2, pAkt, increase in Bcl-2/Bax, and decrease in DA indicated that to minimize DHCA-dependent neuronal injury, LF flow should be above 50 ml/(kg/min).

Cardiac Output Augmentation During Hypoxemia Improves Cerebral Metabolism After Hypothermic Cardiopulmonary Bypass

Hypothermic circulatory arrest (HCA) impairs cerebral oxygen delivery (CDO2) and cerebral oxygen consumption (CMRO2), which are further reduced by perioperative hypoxemia. This study investigates if continuous hypothermic low-flow cardiopulmonary bypass (HLF) or intermittent hypothermic low-flow cardiopulmonary bypass (IHLF) can prevent reductions in CDO2 and CMRO2 during hypoxemia. Eighteen neonatal piglets, cooled to 16 degrees to 18 degrees C with cardiopulmonary bypass (CPB), were randomly assigned into three groups: HCA, HLF (50 cc.kg(-1).min(-1)), or IHLF (1 minute of HLF for every 15 minutes of HCA). After 60 minutes of hypothermia, normothermic CPB (100 cc.kg(-1).min(-1)) was established and cerebral perfusion data measured at hyperoxemia (PaO2 150 to 250 mm Hg), hypoxemia (PaO2 50 to 60 mm Hg), and severe hypoxemia (PaO2 30 to 40 mm Hg), and with increased CPB flow (200 cc.kg(-1).min(-1)) during severe hypoxemia. The CMRO2 (in mL O2.100 g(-1).min(-1)) was lower after HCA (2.5 +/- 0.3), compared with HLF (4.1 +/- 0.5, p = 0.02) and IHLF (6.2 +/- 0.8, p = 0.002). Within groups, the change from hyperoxemia to severe hypoxemia resulted in decreased CMRO2: HCA (1.3 +/- 0.2, p = 0.004), HLF (3.0 +/- 0.5, p = 0.01), and IHLF (2.9 +/- 0.5, p = 0.01). During severe hypoxemia, increasing CPB flow (from 100 cc.kg(-1).min(-1) to 200 cc.kg(-1).min(-1)) improved CMRO2: HCA (1.9 +/- 0.5, p = 0.05), HLF (4.2 +/- 0.5, p = 0.05), and IHLF (7.4 +/- 0.5, p = 0.04). Hypoxemia reduces CDO2 and CMRO2 despite the method of hypothermic CPB. Increased CPB flow during hypoxemia can restore both CDO2 and CMRO2 to values found with hyperoxemia and slower CPB flows. Augmenting cardiac output during periods of perioperative hypoxemia may prevent cerebral injury after exposure to hypothermic cardiopulmonary bypass.

Injury Pattern of the Neonatal Brain After Hypothermic Low-Flow Cardiopulmonary Bypass in a Piglet Model

Low-flow cardiopulmonary bypass (LF-CPB) is a widely used modality in neonatal heart surgery. While facilitating surgical repair, it poses a risk of neurological injury caused by hypoperfusion. In the present study, we characterize the injury pattern and influencing factors in a piglet hypothermic LF-CPB model. Piglets were anesthetized, tracheally intubated, ventilated, and prepared for CPB. After LF-CPB for 150 min at 22 degrees C (brain) using pH-stat strategy, animals were allowed to survive for 2 or 9 days. Neurological status was assessed daily and magnetic resonance imaging scans were performed. Brains were assessed histologically. Functional neurological impairment was seen in 64%, 30%, and 0% of animals 1, 2, and 9 days after CPB, respectively. All animals showed histological brain damage, predominantly in neocortex and hippocampus, less so in basal ganglia, thalamus, white matter, and cerebellum. Cell death appeared as selective neuronal necrosis in the deeper layers in neocortex and CA1-4 sections in hippocampus. Even in a pH-stat strategy, less neocortical and hippocampal damage correlated with higher arterial partial pressure for carbon dioxide. Less hippocampal damage was associated with higher blood glucose levels. Less functional neurological impairment and basal ganglia damage correlated with higher postoperative hematocrit. Neuronal injury after hypothermic low-flow cardiopulmonary bypass in a piglet model using pH-stat strategy occurs predominantly in deep neocortex and hippocampus. Factors mitigating injury were higher arterial carbon dioxide, hematocrit, and blood glucose levels.

Neurologic monitoring for special cardiopulmonary bypass techniques

Low flow hypothermic cardiopulmonary bypass, deep hypothermic circulatory arrest, and regional low-flow cerebral perfusion are special techniques used to facilitate complex intracardiac and aortic surgery in neonates and infants. Each carries a risk of cerebral hypoxia and neurologic morbidity. Neurologic monitoring in the form of near-infrared spectroscopy for cerebral oxygenation, transcranial Doppler ultrasound, and the bispectral index electroencephalogram can monitor the brain during these techniques to determine the minimum acceptable bypass flow rates or maximum acceptable duration of deep hypothermic circulatory arrest. The use of this monitoring has the potential to improve long-term neurologic and developmental outcome.

Brain oxygenation during cardiopulmonary bypass and circulatory arrest.

Quantitative measurements of oxygen distribution in the microcirculation of the brain cortex of newborn piglets were made during different modes of cardiopulmonary bypass. Three groups of animals, anesthetized and mechanically ventilated, were studied. The first group of animals were maintained on normothermic cardiopulmonary bypass (CPB) at a flow of 100 ml/kg/min, while the second and third groups underwent low flow hypothermic cardiopulmonary bypass (40 ml/kg/min at 18 degrees C) (LFCPB) and deep hypothermic (18 degrees C) circulatory arrest (DHCA), respectively. After bypass, the piglets were monitored for a two hours post-bypass recovery period. CPB caused a decrease in the cortical oxygen from 62 +/- 3 mm Hg to 32 +/- 7 mm Hg at the beginning of bypass and to 36 +/- 5 mm Hg at the end of bypass. During the recovery period, cortical oxygenation steadily decreased, reaching 29 +/- 8 mm Hg at the end of the experiment. With initiation of LFCPB, cortical oxygen decreased to 22 +/- 7 mm Hg. Upon rewarming cortical oxygen increased to 37 +/- 5 mm Hg and then decreased again to about 30 mm Hg at the end of two hours of post-bypass recovery. Similar changes in cortical oxygenation were observed during DHCA. In DHCA cortical oxygen decreased to 19 +/- 4 mm Hg and during rewarming and recovery increased to 35 +/- 6 mm Hg. In conclusion, it has been shown that in newborn piglets recovering from CPB, LFCPB and DHCA, when the blood pressure remained above 55 mm Hg and therefore total blood flow should be well maintained, oxygen pressure in the microvasculature is significantly lower than for pre-bypass. It is suggested that the decreased oxygenation is due to increased heterogeneity in resistance in the microcirculatory units, resulting in broadened distribution of flow rates and oxygen levels.

Na+/K+-ATPase activity in the erythrocytes of infants after normothermic and deep hypothermic low-flow cardiopulmonary bypass

Na+/K+-ATPase activity in the erythrocytes of infants after normothermic and deep hypothermic low-flow cardiopulmonary bypass

Experimental determination of the safe minimum perfusion flow rate for low-flow hypothermic cardiopulmonary bypass

This study investigated the safe minimum perfusion flow rate for low-flow hypothermic cardiopulmonary bypass in a canine model. The adequacy of cerebral oxygenation was determined from the adenosine concentration, the oxygen saturation of cerebral venous blood and brain oxyhemoglobin level. In experiment 1, nine beagles were cooled on bypass to a nasopharyngeal temperature of 18°C and the perfusion flow rate was reduced in a stepwise fashion every 30 min from 100 to 50, 30, 20 and 10 ml/kg per min. In experiment 2, six beagles were cooled on bypass as in experiment 1, and flow was maintained at 30 ml/kg per min for 120 min. At a perfusion flow rate of 30 ml/kg per min, adequate cerebral oxygenation was maintained for 120 min. In contrast, perfusion flow rates of 20 and 10 ml/kg per min were associated with cerebral ischemia.

The limits of detectable cerebral perfusion by transcranial doppler sonography in neonates undergoing deep hypothermic low-flow cardiopulmonary bypass

Objective: Neurologic morbidity including seizures, abnormal neurologic function, and delayed psychomotor development continue to be significant problems for some patients undergoing operations for congenital heart disease, particularly for those subjected to deep hypothermic circulatory arrest. The technique of low-flow cardiopulmonary bypass has been advocated to decrease the incidence of neurologic sequelae. Our study examined the limits of detectable blood flow in the middle cerebral artery during low-flow cardiopulmonary bypass in 28 neonates undergoing the arterial switch procedure. Methods: Cerebral blood flow velocity was measured noninvasively in the M1 segment of the middle cerebral artery with a 2 MHz range-gated pulsed-wave transcranial Doppler sonographic probe that was placed over the left temporal window. As part of the initiation of a planned period of deep hypothermic circulatory arrest, the cardiopulmonary bypass flow rate was decreased in stages to five low-flow rates (50, 40, 30, 20, and 10 ml/kg per minute). After a period of stabilization, cerebral blood flow velocities were recorded at each of the five low-flow rates and reported as a percentage of baseline. Results: All 28 neonates had detectable perfusion in the middle cerebral artery at flow rates of 30 ml/kg per minute or higher. At flows of 20 and 10 ml/kg per minute, one and eight, respectively, of the 28 neonates had no detectable perfusion in the middle cerebral artery. Conclusions: Our data show that cerebral perfusion can be detected by transcranial Doppler sonography in the middle cerebral artery in some neonates at bypass pump flows as low as 10 ml/kg per minute. However, when transcranial Doppler sonography was used in our patient population, a minimum bypass flow rate of 30 ml/kg per minute was needed to detect cerebral perfusion in all neonates. (J Thorac Cardiovasc Surg 1997;114:594-600)

Deep hypothermic low flow cardiopulmonary bypass in small dogs.

To evaluate the feasibility of and morbidity and mortality associated with cardiopulmonary bypass (CPB) using deep hypothermia and low flow perfusion in adult dogs weighing less than 10 kg. Prospective, descriptive study. Two groups of three dogs underwent CPB. Group 1 dogs underwent deep hypothermia (15 to 18 degrees C), 45 minutes of low perfusion flow (20 mL/kg/min) and 1 hour of aortic cross clamp time. In group 2, ultrafiltration of perfusate before discontinuation of bypass was added to the standard treatment. Complete blood counts, serum biochemistry, urine output, ejection fraction, and cardiac output were monitored before and for 7 days after surgery. All dogs were successfully weaned from bypass. Four of six dogs survived, three without major complications. One dog developed and recovered from septic pleuritis. Two dogs died or were euthanatized after surgery because of respiratory or gastrointestinal complications. Minor complications included anemia, hypoproteinemia, and electrolyte disturbances. Transfusion requirements and edema formation were reduced by ultrafiltration. The observations in this study support the feasibility of low flow hypothermic CPB. Meticulous tissue handling, precise equipment, ultrafiltration, and aggressive postoperative potassium supplementation are recommended for smaller patients. Increased sensitivity to adverse sequelae of CPB may be associated with small patient size. Further evaluation is necessary before routine clinical application of low flow hypothermic CPB in this patient population.

Low-flow cardiopulmonary bypass produces greater pulmonary dysfunction than circulatory arrest

Deep hypothermic circulatory arrest (DHCA) is used during the repair of congenital heart disease in neonates. However, because of concern about neurologic injury after DHCA, there is increasing use of continuous deep hypothermic low-flow cardiopulmonary bypass (DHCPB). This study examines the effects of DHCPB versus DHCA on pulmonary dynamics in 1-week-old piglets (weight range, 2.5 to 3.5 kg). Animals were placed on CPB (37 degrees C) at 100 mL.kg-1.min-1, cooled to 18 degrees C, and then assigned to one of two groups: DHCPB (n = 7), 25 to 50 mL.kg-1.min-1 DHCPB for 90 minutes; or DHCA (n = 8), DHCA for 90 minutes. Animals were rewarmed to 37 degrees C, weaned from CPB, and observed for 30 minutes. Static pulmonary compliance and pulmonary vascular resistance index were assessed before CPB, 5 minutes after CPB, and 30 minutes after CPB. There was greater impairment of static pulmonary compliance after DHCPB compared with 90 minutes of DHCA. There was a trend toward higher pulmonary vascular resistance index in the DHCPB group; however, significance was not reached. Deep hypothermic low flow cardiopulmonary bypass produces greater pulmonary dysfunction than DHCA, manifested by decreased static pulmonary compliance. If DHCPB is used in place of DHCA in congenital heart operations, close attention to ventilatory and fluid management is mandatory in the postoperative period to prevent further worsening of pulmonary dysfunction.

Cerebral oxygenation during normothermic, hypothermic, or low flow-hypothermic cardiopulmonary bypass in children

Cerebral oxygenation during normothermic, hypothermic, or low flow-hypothermic cardiopulmonary bypass in children

Cerebral blood flow during low-flow hypothermic cardiopulmonary bypass in baboons.

Neurologic injury after cardiopulmonary bypass (CPB) is a frequent and devastating complication of cardiothoracic surgery. Disordered cerebral hemodynamics during CPB has been implicated as an important factor in the etiology of these injuries. Evidence of disordered cerebral hemodynamics includes reports of a progressive time-dependent decrease in cerebral blood flow (CBF) during stable full-flow CPB. Low-flow hypothermic CPB has become a preferred technique for the management of pediatric patients undergoing surgical repair of complex cardiac lesions. Because CBF is already substantially reduced with the onset of low-flow CPB, we determined if a similar progressive decline in CBF occurs during the low-flow state. After induction of general anesthesia in seven baboons, CPB was instituted. alpha-Stat management of arterial blood gases was used. Animals were cooled at a pump flow rate of 2.5 l.min-1.m-2 until tympanic membrane temperature decreased to 18 degrees C. CPB flow was then reduced to 0.5 l.min-1.m-2 and maintained constant for at least 77 min. Thereafter, CPB flow was increased to 2.5 l.min-1.m-2 and baboons rewarmed to normal temperature. CPB was discontinued after return of cardiac function. CBF was measured before, during and after CPB by washout of intraarterial xenon 133. Low-flow CPB resulted in a decrease in CBF to about 50% of the prebypass rate and about 30% of the value measured during full-flow CPB. Sequential measurements of CBF at 30-min intervals during low-flow CPB showed no time-dependent change in cerebral perfusion. Although systemic flow is reduced to 20% of full-flow during low-flow CPB, CBF reduced by half is disproportionately preserved relative to systemic flow. Furthermore, there is no time-dependent change in CBF under these low-flow conditions.