Nonpulsatile Research Articles

Cardiopulmonary Bypass Settings for the Prevention of Early Hypotension During CABG.

Vasoplegic syndrome is a form of vasodilatory shock that can occur before, during or after cardiopulmonary bypass (CPB). We introduce a strategy to reduce the incidence of early hypotension phenomena during Coronary Artery Bypass Graft (CABG) procedures. In this prospective cohort study, 100 patients underwent elective CABG with two perioperative CPB settings. The study group (50 patients) was managed with retrograde autologous priming (RAP), 3-minute stepwise for the institution of CPB, and pulsatile flow (PP). The control group (50 patients) was managed without RAP, with the rapid initiation of CPB, and non-pulsatile (NP) flow. The primary endpoints were MAP (mmHg), number of hypotensive phenomena (MAP < 50 mmHg for > 30 sec), the venous return volume on CPB (ml), the cardiac index (L/min/m2), hemoglobin (g/dL), indexed oxygen delivery (DO2i, ml/min/m2), the systemic vascular resistance index (SVRI, dynes s m2/cm5), number of 1-ml boluses of a vasoactive substance (norepinephrine), the positive fluid balance (ml), and the number of red blood cell units for transfusion. During CPB, the mean values in the study and control groups were as follows: MAP, 68± 7 vs 56 ± 7 (p-value, 0.0019); hypotensive phenomena, 3 ± 1 vs 8 ±2 (p-value, 0.019); venous return volume, 840±79 vs 1129 ±123 (p-value, 0.0017); cardiac index, 2.4 ± 0.4 vs 2.7 ±0.2 (p-value, 0.0023); hemoglobin, 9.13 ± 0.29 vs 7.8± 0.23 (p-value, 0.0001); DO2i, 301± 12 vs 276±23 (p-value, 0.0011); SVRI, 1879 ±280 vs 2210 ±140 (p-value, 0.0017); norepinephrine, 1±2 vs 8 ±3 (p-value, 0.0023); positive fluid balance, 750 ±212 vs 1450 ±220 (p-value, 0.005); and total number of red blood cell units for transfusion, 16 ±4.2 vs 27 ± 5.3 (p-value, 0.008). In this prospective cohort study, during CPB, the study group showed a better preservation of MAP, SVRI, and DO2i, and a reduction of vasoconstrictor use in a CPB setting with the RAP technique, 3-minute stepwise for the initiation of CPB and pulsatile pump flow, compared to the control group. Further studies are needed to validate this perioperative approach to CPB.

Efficacy of Pulsatile Flow Perfusion in Adult Cardiac Surgery: Hemodynamic Energy and Vascular Reactivity.

Background: The role of pulsatile (PP) versus non-pulsatile (NP) flow during a cardiopulmonary bypass (CPB) is still debated. This study’s aim was to analyze hemodynamic effects, endothelial reactivity and erythrocytes response during a CPB with PP or NP. Methods: Fifty-two patients undergoing an aortic valve replacement were prospectively randomized for surgery with either PP or NP flow. Pulsatility was evaluated in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE). Systemic (SVRi) and pulmonary (PVRi) vascular resistances, endothelial markers levels and erythrocyte nitric-oxide synthase (eNOS) activity were collected at different perioperative time-points. Results: In the PP group, the resultant EEP was 7.3% higher than the mean arterial pressure (MAP), which corresponded to 5150 ± 2291 ergs/cm3 of SHE. In the NP group, the EEP and MAP were equal; no SHE was produced. The PP group showed lower SVRi during clamp-time (p = 0.06) and lower PVRi after protamine administration and during first postoperative hours (p = 0.02). Lower SVRi required a higher dosage of norepinephrine in the PP group (p = 0.02). Erythrocyte eNOS activity results were higher in the PP patients (p = 0.04). Renal function was better preserved in the PP group (p = 0.001), whereas other perioperative variables were comparable between the groups. Conclusions: A PP flow during a CPB results in significantly lower SVRi, PVRi and increased eNOS production. The clinical impact of increased perioperative vasopressor requirements in the PP group deserves further evaluation.

Intrapulmonary shear stress enhancement: A new therapeutic approach in acute myocardial ischemia

Ischemic heart disease (IHD) is a leading cause of mortality with insufficient results of current therapies, most probably due to maintained endothelial dysfunction conditions. Alternatively, we propose a new treatment that promotes endothelial shear stress (ESS) enhancement using an intrapulmonary pulsatile catheter. Twelve piglets, divided in equal groups of 6: pulsatile (P) and non-pulsatile (NP), underwent permanent left anterior descending coronary artery ligation through sternotomy. After 1 h of ischemia and heparin injection (150 IU/kg): in P group, a pulsatile catheter was introduced into the pulmonary trunk and pulsated intermittently over 1 h, and irrespective of heart rate (110 bpm). In NP group, nitrates were given (7 ± 2 mg/kg/min) for 1 h. In P group all 6 animals survived ischemia for 120 min, but in NP group only 2 animals survived. The 4 animals that died during the experiment in NP group survived for 93 ± 14 min. Hemodynamics and cardiac output (CO) were significantly improved in P group compared with NP group: CO was 0.92 ± 0.15 vs. 0.52 ± 0.08 in NP group (L/min; p < 0.05), respectively. Vascular resistances (dynes.s.cm(-5)/kg) were significantly (p < 0.05) lower in P group versus NP group: pulmonary resistance was 119 ± 13 vs. 400 ± 42 and systemic resistance was 319 ± 43 vs. 1857 ± 326, respectively. Myocardial apoptosis was significantly (p < 0.01) lower in P group (0.66 ± 0.07) vs. (4.18 ± 0.27) in NP group. Myocardial endothelial NO synthase mRNA expression was significantly (p < 0.01) greater in P group (0.90 ± 0.09) vs. (0.25 ± 0.04) in NP group. Intrapulmonary pulsatile catheter could improve hemodynamics and myocardial contractility in acute myocardial ischemia. This represents a cost-effective method, suitable for emergency setting as a first priority, regardless of classical coronary reperfusion.

Pulsatile flow decreases gaseous micro-bubble filtering properties of oxygenators without integrated arterial filters during cardiopulmonary bypass

Cardiopulmonary bypass (CPB) has a risk of embolic injury with an important role of gaseous micro-bubbles (GMBs), coming from CPB-circuit. Pulsatile perfusion (PP) can provide specific conditions for supplementary GMB-activity with respect to non-pulsatile (NP). We aimed to test GMB-filtering properties of three modern oxygenators under pulsatile and non-pulsatile conditions. Seventy-eight patients undergoing on-pump myocardial revascularization were randomized prospectively into three equal groups according to the oxygenator model used during CPB. Terumo Capiox-FX25, Sorin Synthesis or Maquet Quadrox-i-Adult membrane oxygenators were tested. Each group was divided equally to undergo PP or NP. GMBs were counted by means of a GAMPT-BCC200 bubble-counter with two probes placed at preoxygenator and arterial post-filter positions. Results were evaluated in terms of GMB-volume, GMB-number, amount of large over-ranged GMBs, a series of filtering indices and major neurological outcomes. PP decreased GMB-filtering properties of the tested oxygenators. Those with integrated filters (CAPIOX-FX25 and SYNTHESIS) did not show significant differences between perfusion groups, while QUADROX-i oxygenator with external arterial filter showed significantly higher GMB-volume (P < 0.001), GMB-number (P < 0.001) and amount of over-ranged bubbles (P < 0.001) detected in arterial line during PP. Despite the differences in filtering capacity of all circuits with both types of perfusion, no important differences in clinical outcomes and major neurological events were observed. Pulsatile flow decreases gaseous micro-bubble filtering properties of oxygenators without integrated arterial filters during CPB. PP requires specially designed circuit components to avoid the risk of additional GMB delivery.

The effects of pulsatile flow characteristics on hemolysis, transfusion requirement, and hemostasis in open heart surgeries

Background: The aim of this study was to investigate the effects of pulsatile and nonpulsatile perfusion on hemolysis parameters and protection of blood components. Methods: This randomized, controlled and prospectively designed study included two independent groups, consisting of 27 nonpulsatile (NP) and 24 pulsatile (P) cases who had undergone open heart surgical procedures. Demographic and hemodynamic data were recorded. The effects of perfusion types were evaluated in terms of free hemoglobin (free Hb), haptoglobin (Hp), lactate dehydrogenase (LDH), potassium (K+), platelet number (plt) and urine Hb. These levels were measured in preoperative period, 30 and 60 minutes after initiation of cardiopulmonary bypass (CPB), two and 24 hours postoperatively. Also, total chest drainage and transfusion requirement were assessed. Results: Demographic and hemodynamic measurements did not differ between the groups. The mean arterial pressure of the NP group was statistically higher at the 30th minute. Free Hb, Hp, LDH and K+ levels did not differ in both groups in all time points. The urine Hb levels were significantly higher in the P group in the 30th minute. There was no difference regarding total chest drainage amounts and number of transfused erythrocyte cell packages. Conclusion: A clinically nonsignificant hemolytic effect of pulsatile perfusion can be outlined, although it is mentioned only in the urine Hb measurements on the laboratory basis.

Pulsatile Versus Nonpulsatile Cardiopulmonary Bypass Flow: An Evidence-Based Approach

To derive evidence-based recommendations for the use of pulsatile perfusion (PP) technique for the reduction of mortality and nonfatal complications after elective coronary artery bypass grafting surgery (CABG). Incidence of total mortality, myocardial infarction (MI), stroke, and renal failure during hospital stay. Medline, Embase, and the Cochrane controlled trial register (CCTR) on the Cochrane library were searched from the earliest achievable date of each database to March 2005. No language restrictions were applied. Retrieved reprints were evaluated according to a priori inclusion criteria, and those included were critically appraised using established internal validity criteria. BENEFITS AND HARMS: Only one fair quality randomized controlled trial demonstrated the beneficial effect of PP in reducing the incidence of total mortality and MI. No studies demonstrated the beneficial effect of PP in reducing the incidence of stoke or renal failure. One randomized controlled trial demonstrated that PP was associated with increased hemolysis compared to nonpulsatile (NP) perfusion. The evidence is conflicting and therefore does not support making recommendation for or against routinely providing the PP to reduce the incidence of mortality or MI. The evidence is insufficient to recommend for or against routinely providing the pulsatile profusion to reduce the incidence of stroke or renal failure.

Effect of Pump Flow Mode of Novel Left Ventricular Assist Device Upon End Organ Perfusion in Dogs With Doxorubicin Induced Heart Failure

End organ effects of nonpulsatile (NP) and pulsatile (P) left ventricular assist device (LVAD) flow were compared in a canine model of doxorubicin-induced heart failure. After heart failure induction, a prototype bimodal LVAD was implanted. Hemodynamics, cardiac dimensions, and myocardial metabolism were monitored with the LVAD off (baseline) and on (in NP and P modes at 70% or 100% power). End organ perfusion was assessed by colored microsphere analysis. Seven dogs were used: two died before pump implantation and were excluded from analysis, and the remaining five survived to study termination. At 70% NP, ascending aortic flow and myocardial oxygen consumption (MVO2) decreased significantly. At 100% NP, LV dimensions decreased, aortic systolic, pulse, and LV pressures decreased but not significantly, and ascending aorta flow reversed. At 100% NP, coronary blood flow, MVO2, and LV free wall subepicardial and subendocardial blood flows decreased significantly. However, as NP support increased, the subepicardial/subendocardial blood flow ratio remained near baseline. At 100% NP, right ventricular perfusion decreased but not significantly, cerebral perfusion decreased significantly, and renal perfusion stayed constant. P mode results were similar, except that ascending aorta flow decreased significantly at 100% P instead of reversing as at 100% NP. These results suggest that end organ perfusion is not differentially affected by LVAD flow mode during chronic heart failure.

Comparative study of pulsatile and nonpulsatile flow during cardio-pulmonary bypass.

The use of nonpulsatile flow during extracorporeal circulation remains popular despite theoretical advantages of pulsatile cardiopulmonary bypass (CPB). Pulsatile CPB is considered to be more physiological than nonpulsatile flow as the pulsatile energy ensures the patency of the vascular bed and mechanical motion of tissue fluid around the cell membrane, improves microcirculation and enhances diffusion. The purpose of this study was to compare the effect of pulsatile and nonpulsatile flow on the coagulation profile, liver and kidney function and also on the haemodynamics in patients undergoing coronary artery bypass grafting on CPB. One hundred patients between 35 and 65 years of age with normal left ventricular function were randomly divided into two equal groups: Pulsatile (P) and nonpulsatile (NP). Haematological parameters, clotting profile, renal parameters, hepatic function tests and haemodynamic variables were measured preoperatively and postoperatively at specific intervals. Surgical, anaesthetic and CPB regimen was standard in all cases. There was a decrease in platelet count during and after CPB in both groups. Coagulation profile and renal function parameters remained similar in both groups except that creatinine clearance was better in group P on the first postoperative day. Urine output was also better in group P. There was no change in liver function tests in both groups. The haemodynamic variables were comparable in both groups. The systemic vascular resistance was higher in group NP postoperatively and oxygen consumption was higher in group P post CPB. In conclusion we did not find any significant difference between pulsatile and nonpulsatile flow during CPB except the creatinine clearance and urine output were better in pulsatile group.

Comparison of pulsatile versus nonpulsatile perfusion on the postcardiopulmonary bypass aortic-radial artery pressure gradient

Objective: To investigate whether the type of perfusion, pulsatile (PP) or nonpulsatile (NP), has any effect on the pressure gradient that exists between the aortic root and the radial artery after cardiopulmonary bypass (CPB). Design: Prospective, randomized study. Setting: Tertiary care, university hospital. Participants: Eighty patients undergoing elective, hypothermic coronary artery bypass graft (CABG) surgery. Interventions: Pulsatile perfusion with a pulse pressure of 10 to 20 mmHg and a frequency of 60 to 80 beats/min was created during the hypothermic phase of CPB. Both the radial artery and aorta were cannulated and attached to separate transducers but displayed and analyzed on the same monitor. Measurements and Main Results: Simultaneous recordings of radial artery and aortic root blood pressure were made prebypass, during CPB, and after discontinuation of CPB at 2,5, and 10 minutes. During CPB, the PP group had a significantly higher mean pulse pressure measured at the aortic root than the NP group (15.5 ± 8.1 v 1.7 ± 2.7, p < 0.0001). The aortic-to-radial-artery gradient within both groups was significantly different after CPB for systolic (SBP), diastolic (DBP), and mean pressure (MAP) ( p < 0.0001). There were, however, no statistically significant differences between the PP and NP groups in the aortic-to-radial-artery gradient after CPB for either SBP, DBP, or MAP. Conclusions: Pulsatile perfusion had no effect on the aortic root radial artery blood pressure gradient after CPB in elective CABG surgery patients.

IN-VIVO AND IN-VITRO EVALUATION OF A PULSATILE MODE OF A MAGNETICALLY SUSPENDED CENTRIFUGAL PUMP (MSCP)

The authors have been developing a magnetically suspended centrifugal pump (MSCP). They have devised a pulsatile mode for the MSCP, which was generated by altering rotational speed. This article describes in vitro and in vivo studies with the pulsatile mode of the MSCP. Hemolysis tests were performed in two identical circuits to compare the nonpulsatile (NP) mode and the pulsatile (P) mode. In vivo studies were performed in sheep. First, biventricular assisted circulation was instituted in the left heart with the MSCP and in the right heart with the Biopump. The native heart was induced to ventricular fibrillation. Second, a left ventricular assisted circulation was instituted as the native heart was beating. An inflow cannula was inserted into the left atrium in one sheep and into the left ventricle in the other. The normalized indices of hemolysis of the NP and P groups were 0.0025 +/- 0.0018 g/100 L, and 0.0032 +/- 0.0024 g/100 L (N = 4, not significant). During ventricular fibrillation in the P mode, the pulse pressure was 14 mmHg (the rotational speed: 1,500 to 2,600 rpm). In a beating heart, at atrial withdrawal, the pulse pressure increased from 10 to 24 mmHg (2,100 +/- 500 rpm), while at ventricular withdrawal, it decreased from 17 to 40 mmHg (2,000 +/- 500 rpm) on P mode. The MSCP in pulsatile mode did not increase hemolysis. At ventricular withdrawal, it was easier to produce a pulsation than at atrial withdrawal. The pulsatile mode of the MSCP is applicable to a left ventricular assist system.

Myocardial Metabolism during Fixed-Rate Pulsatile Left Ventricular Bypass

Fixed-rate pulsatile cardiopulmonary bypass may improve subendocardial perfusion during ventricular fibrillation and has been employed during intermittent aortic cross-clamping. Variable-rate pulsatile left heart bypass that is governed by venous inflow and is asynchronous to the electrical activity of the heart is currently used in clinical practice. To study the effect of fixed-rate pulsation on myocardial metabolism during left heart bypass, six adult pigs underwent alternating periods of pulsatile (PLS) and nonpulsatile (NPLS) centrifugal pump left atrial-to-aortic bypass in randomized block design. Coronary sinus, aortic, and bypass circuit flows were recorded. Oxygen content and lactate concentration of coronary sinus and aortic blood were measured. Pulsatility index and pulse power index during pulsatile bypass were 4.4 and 4.7 (cycles/s)2, respectively. Percent bypass was maximal at a mean pulsation rate of 41.3 and averaged 92.2 and 91.3 for PLS and NPLS, respectively. Myocardial oxygen consumption per minute was reduced 14.3% during NPLS but was unchanged during PLS compared to control (CTRL). Percent lactate extraction was significantly lower than CTRL during NPLS only. Competition for inflow with the ejecting heart appeared to limit circuit pulsation rate and pulse power index. Fixed-rate pulsation is ineffective in reducing myocardial metabolism and should be avoided in left heart bypass.

Relationship of ischemic contracture to high energy phosphate content and mitochondrial function in hypertrophied myocardium

Relationship of ischemic contracture to high energy phosphate content and mitochondrial function in hypertrophied myocardium

Effect of pulseless perfusion on gastrointestinal blood flow and its distribution.

The effect of nonpulsatile (NP) arterial perfusion on gastrointestinal organ blood flow and intraorgan flow distribution was studied in 10 anesthetized (pentobarbital) dogs utilizing the radionuclide-labeled microsphere (15 micrometer) technique. Measurements of flow to the stomach, small intestine, and colon were made during a pulsatile perfusion control period and after 1- and 2-h periods of NP perfusion with a centrifugal left ventricular bypass pump (Medtronic). Total gastric blood flow (0.178 +/- 0.021 ml/min per g) as well as the partitioning of that flow between gastric subsegments such as antrum (17% of total gastric flow), body (83%), and mucosa (73%) was not significantly altered during the 2-h period of NP perfusion (P greater than 0.20). Similarly, flow to the intestine showed significant change during NP perfusion. Under conditions of equivalent hemodynamic states (mean perfusion pressure), nonpulsatile arterial perfusion results in no significant alteration in gastrointestinal blood flow or its intraorgan distribution.

Comparison of Nonpulsatile and Pulsatile Extracorporeal Circulation on Renal Tissue Perfusion

This study was designed to compare the physiologic effects of nonpulsatile (NP) and pulsatile (P) perfusion on the kidney. Serial specimens for blood gases and serum lactic acid (L) were taken from the renal artery and vein in three groups of dogs; one group served as control. The aortic arch was crossclamped and NP and P left atrial to left subclavian artery bypass was performed for two hours on two groups of dogs. Renal blood flow (RBF) and arterial (AP) and the venous pressures (VP) were continuously monitored. Vascular resistance (VR) was calculated by the formula VR = (AP—VP)/RBF. In order to maintain nearly equal arterial pressures above and below the crossclamped aorta, a higher flow rate was required with NP (80 ml/kg/min) than with P (60 ml/Kg/min). Marked reduction in pH (7.255) along with elevated L (50 mg/100 ml) were consistent with NP. There was less reduction in pH (7.37) and less elevation of L (35 mg/100 ml) with P, whereas control pH was 7.37 and L was 17 mg/ml. Pulsatile pumping provides better tissue perfusion during extracorporeal bypass.