Milrinone, a phosphodiesterase III inhibitor, prevents reduction of jugular bulb saturation during rewarming from hypothermic cardiopulmonary bypass

Introduction: Inadequate cerebral oxygen balance during cardiopulmonary bypass may cause neuropsychological dysfunction. Milrinone, a phosphodiesterase III inhibitor, augments cerebral blood flow by direct vasodilatation. We conducted a prospective, randomized study in patients undergoing cardiac surgery with cardiopulmonary bypass to clarify the clinical efficacy of milrinone in the imbalance of cerebral oxygen supply and demand during the rewarming period of cardiopulmonary bypass. Methods: This is a prospective, randomized and placebo-controlled study. After anesthesia, a 5.5 F fiberoptic oximeter catheter was inserted into the right jugular bulb retrogradely for monitoring the jugular venous oxyhemoglobin saturation (SjO(2)). Patients were randomly assigned to two groups, one receiving a continuous infusion of milrinone, 0.5 μg/kg/min during hypothermic cardiopulmonary bypass, and the other receiving saline as control. Results: Milrinone significantly prevented the reduction of the jugular venous oxyhemoglobin saturation at 10 minutes from the start of rewarming compared with the control group, but did not do so from 10 to 20 minutes after rewarming. Conclusion: Milrinone suppresses the reduction of SjO(2) and improves the balance of cerebral oxygen supply and demand during the early rewarming period of hypothermic cardiopulmonary bypass.     

体外循环心脏手术中辅助复温致手掌烫伤1例

报告1例体外循环心脏手术中辅助复温致手掌低温烧伤患者的致伤过程和护理体会。患者在低温体外循环下行心脏手术,术中为配合体外循环复温,将用敷料包裹的水温45℃的温水瓶放于患者双手掌行辅助复温,导致其低温烧伤,经及时发现、积极对症处理后痊愈。提示护理人员应加强对低温烧伤的认识,在局部加热时,控制温度,缩短观察间隔时间,间断加热,以防止低温烧伤的发生。     

Arterial isoflurane concentration and EEG burst suppression during cardiopulmonary bypass

Isoflurane (1.5 to 3.0 vol% in oxygen) was used to control intraoperative hypertension in 10 patients undergoing hypothermic cardiopulmonary bypass surgery. Isoflurane was administered through the membrane oxygenator of the bypass pump and yielded plateau concentrations in arterial blood ranging from 36.6 to 84.4 micrograms/ml (0.5 and 1.16 vol%, respectively). Isoflurane dosing resulted in prolonged periods (21 to 63 minutes) of EEG burst suppression and isoelectric activity in nine patients. Burst suppression was not a result of hypothermia. There was a close temporal relationship between isoflurane concentration and the onset of burst suppression (mean onset time: 27.3 +/- 4.56 minutes after isoflurane begun). The mean arterial isoflurane concentration at the onset of burst suppression was 46.5 +/- 10.7 micrograms/ml; the nasopharyngeal temperature was 26.0 degrees +/- 0.61 degrees C. Isoflurane was eliminated rapidly from blood with a mean apparent t1/2 of 18.8 +/- 5.46 minutes.     

Accidental hypothermia with cardiac arrest: recovery following rewarming by cardiopulmonary bypass.

A 22-year-old man eventually had a good neurologic recovery following prolonged coma after extracorporeal rewarming from profound hypothermia (24 degrees C) due to exposure. The patient was in full arrest for 60 minutes prior to institution of cardiopulmonary bypass (CPB). Total bypass time was 50 minutes. Cardiopulmonary bypass is the current rewarming method of choice for severe hypothermia associated with a persistent nonperfusing cardiac rhythm. CPB provides the most rapid core rewarming with the additional benefit of circulatory support during the period of cardiac instability.     

High risk of intraoperative awareness during cardiopulmonary bypass with isoflurane administration via diffusion membrane oxygenators

In cardiac surgery with the aid of extracorporeal circulation (ECC), inhalation anaesthetics can be administered via the oxygenator. Until the recent advent of a new type of diffusion membrane oxygenator, we routinely added the inhalation agent, isoflurane, to the gas flow of a microporous capillary membrane-type oxygenator. Applying this procedure to the diffusion-type oxygenators, the depth of anaesthesia appeared to be affected, which manifested itself through unusually high intraoperative perfusion pressures. This observation led to a prospective randomized study comprising 60 patients and two models of a microporous capillary membrane oxygenator, as well as two models of a diffusion membrane oxygenator. Simultaneous isoflurane concentration measurements at both the gas inlet and outlet ports of the oxygenators showed that, whereas in the microporous capillary-type oxygenators the isoflurane administered was reduced by about 50% during the passage of gas through the device, there was only a minimal transfer of isoflurane in the diffusion-type membrane oxygenators.     

Cefamandole kinetics during cardiopulmonary bypass

The kinetics of cefamandole during cardiac surgery was studied in 16 adult patients given a single intravenous infusion of 20 mg/kg at the time of anesthesia induction. Five normal volunteers who received the same dose served as controls. Cardiopulmonary bypass (CPB) was found to signficantly increase the half-life (t 1/2) of cefamandole. The mean t 1/2 during CPB (113.2 min) was longer than the terminal t 1/2 in normal volunteers (52.0 min; p less than 0.005). Throughout CPB (maximum, 3,7 hr), cefamandole plasma levels were maintained above the minimum inhibitory concentration for those organisms most likely to cause postoperative infections. We conclude that if 20 mg/kg of cefamandole is given within an hour of the beginning of cardiovascular surgery, a supplemental dose is not needed until the patient has been on CPB for at least four hours.     

Inflammatory mediator removal by zero-balance ultrafiltration during cardiopulmonary bypass

The abnormal conditions to which blood is subjected during cardiopulmonary bypass (CPB) trigger an activation of the inflammatory response in all patients to varying degrees. Both complement activation and the release of cytokines characterize this response. Most inflammatory mediators have a molecular weight that is below the membrane pore size of commonly used ultrafilters, which should allow them to be freely filtered. However, some mediators have been shown to fail to cross through the membrane even though they are small enough to cross. The purpose of the present study was to determine whether certain inflammatory mediators could be removed by ultrafiltration when performed during the rewarming phase of CPB. Thirty adult patients undergoing a single, open-heart procedure were randomized to either control (no ultrafiltration) or to the zero-balance ultrafiltration (ZBUF) group. ZBUF was performed by removing 3 l/m2 blood using a 65-kDa ultrafilter with 1.3-m2 surface area. A volume of a balanced salt crystalloid solution (Plasmalyte) equal to the filtered blood volume was given to replace the fluid removed. Patient data was taken before CPB (T1), immediately following CPB (T2), and 12 h following the procedure (T3). The average volume of filtrate removed during ZBUF was 6405 ml, which was analyzed for the presence of interleukin (IL)-1, IL-6, tumor necrosis factor-alpha (TNF-alpha), C3a, and C5a. The average concentrations of the mediators measured in the effluent were: IL-1, 0.17 pg/ml; IL-6, 0.64 pg/ml; TNF-alpha, 1.25 ng/ml; C3a, 782.6 ng/ml; C5a, 25.6 ng/ml. In every case except for IL-1, the amounts of mediators removed were significantly greater than zero. This study demonstrates that ultrafiltration is a strategy that can be used during CPB in the adult to remove significant amounts of inflammatory mediators.     

Monocyte activation markers during cardiopulmonary bypass

Extracorporeal support during cardiac surgery initiates an inflammatory response, causing damage to cardiac, pulmonary and renal tissue [Post Pump Syndrome (PPS)]. This is accompanied by a neutrophil leucocytosis and lymphopenia, but less is known about the role of monocytes and markers of monocyte activity. We studied 19 patients undergoing cardiac surgery, obtaining blood samples from the aortic root (AR) and from the coronary sinus ( < s) before the cardiopulmonary bypass (CPB), 1 min after release of the aortic crossclamp and 10 min after weaning from CPB (periods 1, 2 and 3). Leucocyte count, monocyte count and HLA-DR, CD15, CD11b and CD62L activation markers were measured. In samples obtained from the coronary sinus (CS), HLA-DR, expressed as a percentage of the monocyte count, decreased between periods 1, 2 and 3 by 78%, 66% and 43%, respectively. A similar change was observed in samples from the AR. Conversely, CD62L increased in the CS samples (55%, 68% and 73%), but revealed a lesser increase in the AR samples (51%, 68% and 63%). The other markers showed little change throughout the procedure. Reduced immunological competence could result from the decrease in HLA-DR counts. Increases in CD62L sensitizes monocytes to the tethering effects of endothelial integrins and might contribute to the atherosclerotic process.     

Occupational exposure to sevoflurane during cardiopulmonary bypass

Volatile anaesthetic agents are widely used for maintenance of anaesthesia in all kinds of surgical procedures. Despite the implementation of measures such as adequate ventilation of the operating room and the use of efficient scavenging systems, concern remains about the risks for occupational exposure, especially in situations associated with an increased risk of anaesthetic gas waste, such as with the use of volatile anaesthetic agents on cardiopulmonary bypass. The present contribution reports the results of a preliminary safety assessment involving measurements of sevoflurane concentrations in the ambient air of a cardiac surgery operating room. In 22 cardiac surgical procedures with cardiopulmonary bypass (11 with open and 11 with closed venous reservoir), measurements of trace concentrations were obtained every 10 min at the following sites: at the outlet of the oxygenator, at the outlet of the cardiotomy reservoir, in the breathing zone of the perfusionist and above the surgical field. The concentrations were measured on-line using a photoacoustic infrared spectrometer. Mean sevoflurane waste concentrations remained consistently below the recommended target value of 4.68 ppm throughout the observation period at the different measurement sites. These results indicate that, with the use of sevoflurane on cardiopulmonary bypass, the recommended levels for occupational exposure are not exceeded, provided adequate operation room ventilation and waste gas scavenging is performed.     

Altered d-tubocurarine disposition during cardiopulmonary bypass surgery

Kinetics of the neuromuscular blocker d-tubocurarine (dTc) were investigated in 13 adult patients undergoing surgery involving cardiopulmonary bypass (CPB). Approximately 1 hr before CPB surgery, each received dTc as an intravenous bolus of 0.6 mg/kg and a maintenance infusion of 3 micrograms/kg/min. dTc plasma concentration-time data before CPB did not differ from those reported in normal surgical patients. There was an abrupt discontinuity in the plasma concentration-time profile with the onset of CPB, and both total and free plasma concentrations increased 400% during the period of CPB. Although computer simulations suggest that these rises in dTc plasma concentrations can be attributed to contraction in central compartment volume, there also was decreased renal and total plasma clearance of dTc together with a prolonged elimination 1 1/2, which suggests that clearance processes of dTc are also altered as a result of CPB. A 27% rise in dTc free fraction in plasma during CPB could be attributed to hemodilution associated with the CPB procedure itself. Lower doses of dTc will need to be used in patients undergoing surgery that involves CPB unless the concentration-effect relationship for dTc is so altered that higher concentrations are needed to elicit the same response as in normal patients.     

Whole blood calcium activity during cardiopulmonary bypass

Whole blood calcium activity, total plasma calcium, pH, pCO₂, and plasma albumen concentrations were measured in ten patients undergoing cardiopulmonary bypass. Since calcium activity was the same before and after bypass, routine monitoring of calcium activity is only recommended when large blood transfusions are given. Depression of myocardial contractility post-bypass is rarely related to a low blood calcium activity.     

Intercompartmental fluid volume shifts during cardiopulmonary bypass measured by A-mode ultrasonography

To investigate the time course of fluid extravasation during cardiopulmonary bypass (CPB), we measured the peripheral tissue thickness (TT) by A-mode ultrasound in 34 patients undergoing elective cardiac surgery. TT of the forehead was determined by a handheld A-mode ultrasound device and 10 MHz Transducer at nine defined intervals, from the night before surgery until the first postoperative day. Mean calculated loss of 1700 +/- 40 mL (SEM) water during the fasting period resulted in a significant reduction of TT by 0.28 +/- 0.03 mm. From induction to start of CPB, rehydration with 1000 mL of fluid was performed and TT increased to baseline. After 60 min of extracorporal circulation, forehead TT increased significantly by 0.75 +/- 0.08 mm and remained unchanged until the end of surgery when the measured fluid gain was 1580 +/- 138 mL. At discharge from ICU, negative fluid regimen resulted in a balance of -127 +/- 146 mL whereas TT declined significantly to +0.16 +/- 0.09 mm compared to baseline. Dehydration due to fasting and the marked interstitial fluid extravasation during CPB could be detected by the changes of the peripheral TT. We conclude that parts of the fluid load during CPB are shifted from the intravascular compartment to the interstitial space in a time-dependent manner.     

Changing the priming solution from Ringer's to Hartmann's solution is associated with less metabolic acidosis during cardiopulmonary bypass

BACKGROUND AND OBJECTIVE: Previously, it was noted that changing the solutions used for priming and intravascular volume replacement from Hartmann's to Ringer's resulted in a more profound metabolic acidosis developing during cardiopulmonary bypass (CPB). The aim of this study was to examine the effects of changing the solutions back to Hartmann's on metabolic acidosis that develops during CPB in patients undergoing heart surgery. METHODS: Two groups of patients were studied sequentially: the first received Ringer's (n = 63) and the second Hartmann's solution (n = 66). Arterial blood samples were taken before induction of anaesthesia and towards the end of CPB. Samples were analysed in a blood gas analyser. RESULTS: Hydrogen ion concentration increased from 38 (4) to 41 (7)mmol/L in the Ringer's group, but decreased from 38 (5) to 36 (6) mmol L(-1) in the Hartmann's group. Changes in PaCO2 (0.77, p < 0.001) and volume of fluid administered (r= 0.23, p <0.01) were significant univariate correlates of change in hydrogen ion concentration, but haemoglobin concentration was not (r < 0.01, p = 0.97). Analysis of variance for repeated measures found significant between subject effects on the change in hydrogen ion concentration during CPB caused by the choice of intravascular solution used (p < 0.001) and PaCO2 (p = 0.001), but not as a result of the volume of solution administered (p > 0.10). CONCLUSIONS: Changing the solutions used for priming and intravascular volume replacement from Ringer's to Hartmann's was associated with a reduction in metabolic acidosis that developed during CPB.     

Adjustment of sweep gas flow during cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is one of the major tools of cardiac surgery. However, no clear data are available for the ideal value of sweep gas flow to oxygenator during CPB. The aim of this study was to determine the best value for sweep gas flow during CPB. Thirty patients undergoing isolated CABG were randomly and equally allocated into three groups. Sweep gas flow to oxygenator was kept at 1.35 l/min/m2 in group 1, 1.60 l/min/m2 in group 2, and 2.0 l/min/m2 in group 3. All patients were operated on under the same anaesthetic regime and surgical techniques. Samples for blood gas analysis were collected at T1: before CPB; T2: 5 min after the initiation of CPB; T3: just before rewarning; and T4: at the end of rewarming. Five minutes after the initiation of CPB (T2), pCO2 decreased significantly in groups 2 and 3 compared to group 1 (p < 0.02). With the addition of hypothermia (T3), the changes in the pH and pCO2 became more profound and, in this period, the levels in group 3 patients outranged the physiologic limits, with pCO2 and pH values being 28 +/- 3 mmHg and 7.50 +/- 0.04, respectively. At the end of the rewarming period (T4), in spite of increased carbon dioxide production, pCO2 values were below the physiologic limits in groups 2 and 3. We conclude that sweep gas flow to the oxygenator should be kept between 1.35 and 1.60 l/min/m2 during CPB to avoid hypocapnia, which results in alkalosis and has hazardous effects on lung mechanics, cerebral blood flow, and the cardiovascular system.     

Neurological injury during cardiopulmonary bypass in the rat

Cerebral injury is a well-known complication of cardiac surgery. Investigations of both injury mechanisms and neuroprotective strategies have partially been limited by the lack of an adequate preclinical model of small animal cardiopulmonary bypass (CPB). We sought to determine if neurological injury could be demonstrated in a recovery model of complete CPB in the rat. Rats (n = 5) underwent 45 min of normothermic CPB followed by 24 h of recovery. Compared to sham-operated rats (n = 5), the CPB group showed a worse neurological outcome score (median, 25-75th percentile) compared to controls (5, 4-7 vs 9, 8-9, p = 0.016). This rat model of CPB may allow for the study of CPB-associated neurological injury.