Acute alterations of body composition after open intracardiac operations

Hormonal response to fluid administration in cardiac surgery patients

The effects of three different fluid regimes administered before surgery on stress-related hormones were studied in 36 patients undergoing elective aortocoronary bypass grafting. Low-dose Ringer's solution (10 ml/kg; low-dose crystalloid group [LDC]), high-dose Ringer's solution (20 ml/kg; high-dose crystalloid group [(HDC]). or a combination of Ringer's solution (10 ml/kg) with high-molecular weight hydroxyethylstarch (HES) (10 ml/kg) (crystalloid-HES group [C-HES]) were randomly administered prior to operation. Haemodynamic variables and plasma concentrations of ADH, ACTH, renin, aldosterone, cortisol and catecholamines were studied before volume load, before commencement of cardiopulmonary bypass (CPB), and immediately after weaning from CPB.

Cardiac index and stroke volume index in the C-HES group increased by 20% and 18% respectively, systemic vascular resistance decreased by 25% after volume infusion. This was associated with a decrease in the plasma concentrations of ADH, renin and aldosterone. In contrast to this, in the LDC and HDC groups, haemodynamic parameters remained almost unchanged after volume load. This was associated with an increase in aldosterone (LDC 20%; HDC 58%) and renin (LDC 110%; HDC 44%). In all groups, plasma concentrations of catecholamines increased progressively during the time of surgery and were not influenced by the nature or volume of fluid administered.

We conclude that the administration of a combination of crystalloid and colloid solutions during induction of anaesthesia effectively improves haemodynamics and attenuates the increase of the plasma levels of ADH, renin and aldosterone often associated with surgery.

Lung inflammatory response syndrome after cardiac-operations and treatment of lornoxicam

The majority of patients survive after extracorporeal circulation without any clinically apparent deleterious effects. However, disturbances exist in various degrees sometimes, which indicate the harmful effects of cardiopulmonary bypass (CPB) in the body. Several factors during extracorporeal circulation either mechanical dependent (exposure of blood to non-biological area) or mechanical independent (surgical wounds, ischemia and reperfusion, alteration in body temperature, release of endotoxins) have been shown to trigger the inflammatory reaction of the body. The complement activation, the release of cytokines, the leukocyte activation and accumulation as well as the production of several "mediators" such as oxygen free radicals, metabolites of arachidonic acid, platelet activating factors (PAF), nitric acid, and endothelin. The investigation continues today on the three metabolites of lornoxicam (the hydroxylated metabolite and two other metabolites of unknown chemical composition) to search for potential new pharmacological properties and activities.

Effect of lornoxicam in lung inflammatory response syndrome after operations for cardiac surgery with cardiopulmonary bypass

BACKGROUND

The establishment of Extracorporeal Circulation (EC) significantly contributed to improvement of cardiac surgery, but this is accompanied by harmful side-effects. The most important of them is systemic inflammatory response syndrome. Many efforts have been undertaken to minimize this problem but unfortunately without satisfied solution to date.

MATERIALS AND METHODS

Lornoxicam is a non steroid anti-inflammatory drug which temporally inhibits the cycloxygenase. In this clinical trial we study the effect of lornoxicam in lung inflammatory response after operations for cardiac surgery with cardiopulmonary bypass. In our study we conclude 14 volunteers patients with ischemic coronary disease undergoing coronary artery bypass grafting with EC. In seven of them 16 mg lornoxicam was administered iv before the anesthesia induction and before the connection in heart-lung machine. In control group (7 patients) we administered the same amount of normal saline.

RESULTS

Both groups are equal regarding pro-operative and intra-operative parameters. The inflammatory markers were calculated by Elisa method. We measured the levels of cytokines (IL-6, IL-8, TNF-a), adhesion molecules (ICAM-1, e-Selectin, p-Selectin) and matrix metaloproteinase-3 (MMP-3) just after anesthesia induction, before and after cardiopulmonary bypass, just after the patients administration in ICU and after 8 and 24 hrs. In all patients we estimated the lung's inflammatory reaction with lung biopsy taken at the begging and at the end of the operation. We calculated hemodynamics parameters: Cardiac Index (CI), Systemic Vascular Resistance Index (SVRI), Pulmonary Vascular Resistance Index (PVRI), Left Ventricular Stroke Work Index (LVSWI), Right Ventricular Stroke Work Index (RVSWI), and the Pulmonary arterial pressure, and respiratory parameters too: alveolo-arterial oxygen difference D (A-a), intrapulmonary shunt (Qs/Qt) and pulmonary Compliance. IL-6 levels of lornoxicam group were statistical significant lower at 1st postoperative day compared to them of control group (113±49 and 177±20 respectively, P=0.008). ICAM-1 levels were statistical significant lower at the patient admission in ICU, compared to them of control group (177±29 and 217±22 respectively, P=0.014), and the 1st postoperative day compared to them in control group (281±134 and 489±206 respectively, P=0.045). P-selectin levels were statistical significant lower, compared to them in control group in four measurements (97±23 and 119±7 respectively, P=0.030, 77±19 and 101±20 respectively, P=0.044, 86±4 and 105±13 respectively, P=0.06, 116±13 and 158±17 respectively, P=0.000).

CONCLUSIONS

Hemodynamics and respiratory parameters were improved compared to control group, but these differences was not statistical significant. Eosinofil adhesion and sequestration in intermediate tissue of lung parenchyma were significantly lower compared to control group. Also, alveolar edema was not noted in lornoxicam's group. Lornoxicam reduce the inflammatory response in patients undergone coronary artery bypass grafting with extracorporeal circulation. This calculated from levels reduction of IL-6, ICAM-1 και p-Selectin, and from lung pathologoanatomic examination (absence of alveolar edema, reduce in eosinofil adhesion and sequestration in intermediate tissues). Despite the favorable effect of lornoxicam on the hemodinamics and respiratory parameters these improvement did not seem to be statistical significant.

Vision impairment during cardiac surgery and extracorporeal circulation: current understanding and the need for further investigation

The aim of this article was to provide a comprehensive review of current knowledge regarding ocular hemodynamic alterations affecting the retinal neuroglial cells and optic nerve head (ONH) function during cardiac surgery. Literature indicates that visual loss after heart surgery is a rare but devastating complication provoked by two main causes of optic ischaemia and infarction during on-pump cardiac procedures: microembolism and/or hypoperfusion. Retinal ischaemia and ischaemic optic neuropathy are two possible major consequences of extracorporeal circulation in cardiac surgery. The hemodynamic modifications within the vascular beds of retina and ONH during cardiovascular operations have been incompletely studied. Consequently, it is of great interest to investigate the hemodynamic changes during cardiopulmonary bypass within the choroidal, retinal and optic nerve microcirculations as well as other potential causes of vaso-occlusion. Maintaining stable hemodynamic parameters during cardiovascular surgery seems to be the key to prevent visual impairment.

The 'third space'--fact or fiction?

For decades, the 'third space' was looked upon as an actively consuming compartment. Therefore, perioperative fluid regimens were traditionally based on a generous replacement of this assumed primary loss, in addition to deficits due to insensible perspiration and fasting. The practical consequence was an extremely positive fluid balance in order to maintain blood volume during major surgery. Whereas the insensible perspiration and the preoperative deficits are in fact often negligible, and the third space appears to be only a fictional construct, the excess fluid most likely accumulates interstitially. Such shifting is related to a destruction of the endothelial glycocalyx, a key structure of the vascular barrier, by traumatic inflammation and iatrogenic hypervolaemia. This explains why patients undergoing major surgical interventions benefit significantly from an infusion regimen which does not substitute but avoids 'third-space shifting'. In summary, eradicating this notion from our minds could be a further key to achieving perioperative fluid optimisation.

Does cold blood cardioplegia solution cause deterioration in clinical pulmonary function following coronary artery bypass graft surgery?

OBJECTIVE

Deterioration in pulmonary function is a common complication following coronary artery bypass graft surgery and there is still speculation to the precise causative factors thereof. Cardioplegia solution not drained by the atriocaval cannula enters the lung parenchyma unless removed by a pulmonary artery (PA) vent. The hypothesis of the present study was that cold blood cardioplegia solution damages the lung parenchyma, resulting in an observed deterioration of clinical lung function.

METHODS

A prospective, double-blind, randomised trial was conducted on 142 patients. The study group of 71 patients had a PA vent inserted at the time of cannulation, preventing cardioplegia from going through the lungs. In addition, positive end expiratory pressure (PEEP) was applied and low-volume lung ventilation carried out during cardiopulmonary bypass (CPB). The control group (n =71) had cardioplegia enter the lung parenchyma during cardiopulmonary bypass. Clinical parameters of arterial blood gases, including estimated shunt fraction, spirometry tests and radiographic analysis was made preoperatively and at set times through the postoperative period.

RESULTS

Baseline demographics and intraoperative and postoperative management was the same in both groups, thus, yielding a homogenous sample for analysis. Significant changes were noted in arterial blood gases, spirometry, and radiographic analysis of effusion and atelectasis over the time periods studied (p<0.001). There was, however, no significant difference between the study and control groups at any point (p > 0.05).

CONCLUSIONS

The data, therefore, suggest that allowing cold blood cardioplegia solution to circulate the lungs during cardiopulmonary bypass does not have any (beneficial or detrimental) effect on clinical lung function postoperatively.

Fluid therapy for the surgical patient

Perioperative fluid therapy is the subject of much controversy, and the results of the clinical trials investigating the effect of fluid therapy on outcome of surgery seem contradictory. The aim of this chapter is to review the evidence behind current standard fluid therapy, and to critically analyse the trials examining the effect of fluid therapy on outcome of surgery. The following conclusions are reached: current standard fluid therapy is not at all evidence-based; the evaporative loss from the abdominal cavity is highly overestimated; the non-anatomical third space loss is based on flawed methodology and most probably does not exist; the fluid volume accumulated in traumatized tissue is very small; and volume preloading of neuroaxial blockade is not effective and may cause postoperative fluid overload. The trials of 'goal-directed fluid therapy' aiming at maximal stroke volume and the trials of 'restricted intravenous fluid therapy' are also critically evaluated. The difference in results may be caused by a lax attitude towards 'standard fluid therapy' in the trials of goal-directed fluid therapy, resulting in the testing of various 'standard fluid regimens' versus 'even more fluid'. Without evidence of the existence of a non-anatomical third space loss and ineffectiveness of preloading of neuroaxial blockade, 'restricted intravenous fluid therapy' is not 'restricted', but rather avoids fluid overload by replacing only the fluid actually lost during surgery. The trials of different fluid volumes administered during outpatient surgery confirm that replacement of fluid lost improves outcome. Based on current evidence, the principles of 'restricted intravenous fluid therapy' are recommended: fluid lost should be replaced and fluid overload should be avoided.

Hemorrhage and operation cause a contraction of the extracellular space needing replacement—evidence and implications? A systematic review

BACKGROUND

Hemorrhagic hypotension or operative trauma is believed to cause a contraction of the extracellular fluid volume (ECV) beyond the measured fluid losses. The aim of this review was to explore the evidence and implications of ECV loss.

METHODS

We performed a systematic review of original trials measuring ECV changes during hemorrhage or operation. PubMed, relevant periodicals, and reference lists were searched until no further original articles appeared. The quality of both the scientific and the technical methods of the trials were evaluated.

RESULTS

A total of 61 original articles were found. The pattern appeared that all investigators reporting shock or operation to cause a disparate reduction of the ECV had measured the ECV with the same method. The ECV was calculated from very few blood samples that were withdrawn after 20 to 30 minutes of equilibration of a tracer (the (35)SO(4)-tracer). Trials calculating ECV from multiple blood samples, after longer equilibration times, or using other tracers did not find a contraction of the ECV. On the contrary, trials using a bromide tracer found the ECV to be expanded after operation.

CONCLUSIONS

The evidence supporting the idea that hemorrhage or operation cause a contraction of the ECV is weak, and probably a result of flawed methodology.

Off-pump bypass grafting is safe in patients with left main coronary disease

BACKGROUND

Because of a concern about the ability to tolerate beating heart grafting, patients with left main coronary artery stenosis have been excluded from off-pump bypass. We reviewed our experience with off-pump coronary artery bypass grafting for patients with left main coronary artery disease.

METHODS

Eight hundred twenty-three patients underwent bypass grafting for left main coronary artery disease from January 1998 to October 1999. One hundred patients were revascularized without the use of cardiopulmonary bypass and compared with a contemporaneous cohort of 723 patients who underwent grafting with the aid of cardiopulmonary bypass. All patients had multivessel grafting performed through a sternotomy.

RESULTS

There was one death (1%) in the group undergoing off-pump grafting as compared with a 30-day mortality of 4.7% (p = 0.059) in the on-pump group. Univariate analysis established that patients revascularized without cardiopulmonary bypass were significantly less likely to require postoperative inotropic support (23% versus 62%, p < 0.001) and transfusion (35% versus 67%, p < 0.001). Logistic regression analysis revealed that cardiopulmonary bypass was an independent risk factor for mortality (odds ratio, 7.3; 95% confidence interval, 1.34 to 138.4).

CONCLUSIONS

Coronary artery bypass grafting using off-pump techniques are safe and effective in left main coronary artery disease.

Multivessel coronary bypass grafting without cardiopulmonary support

Coronary artery bypass grafting without the aid of cardiopulmonary bypass (CPB) continues to gain popularity as an alternative to standard techniques of revascularization. CPB with cardioplegic arrest is associated with complications that may negate an otherwise technically flawless procedure. Experience has identified aspects crucial to the success of off-pump bypass grafting, such as patient selection, anesthetic and operative technique, and grafting sequence. We review recent technical advances and reported results for multivessel bypass grafting without CPB.

A successful modification of ultrafiltration for cardiopulmonary bypass in children

Total body water (TBW) is increased after cardiopulmonary bypass (CPB) resulting in tissue oedema and organ dysfunction. Ultrafiltration has been used to reduce this accumulation of water, although conventional ultrafiltration seemed ineffective in reducing the rise in TBW after CPB in our clinical experience. We describe a modified technique in which ultrafiltration is performed in the first 10 minutes after the patient is weaned from bypass, returning nearly all the blood in the circuit to the patient and elevating the haematocrit (Hct) to any predetermined level. We carried out a pilot study on 21 children aged 4-144 months undergoing open-heart surgery and CPB for congenital heart defects. They were divided into three comparable groups: (1) controls (n = 6); (2) conventional ultrafiltration (n = 7); and (3) modified ultrafiltration (n = 8). TBW (bio-impedance), Hct, osmolality, mean corpuscular volume and mean corpuscular haemoglobin concentration were recorded at frequent intervals. Control patients showed elevation of TBW by 18.2% median (range 14.5-20.3), conventional ultrafiltration by 12.4% (7.9-15.0), modified ultrafiltration by 5.7% (4.5-7.1) (p less than 0.0001 compared to controls, p. less than 0.005 compared to conventional ultrafiltration, Mann-Whitney U test). Hct could be elevated to preoperative levels only by the modified method. Mean corpuscular volume, and mean corpuscular haemoglobin concentration osmolality were unaltered. Ultrafiltration by the modified method was more effective than conventional ultrafiltration in reducing the rise in TBW and elevating Hct after CPB.

Total body water in children with congenital heart disease, before and after cardiac surgery

The aim of this study was to measure total body water in children with congenital heart disease before and after cardiac surgery and to compare the results of deuterium and 18oxygen dilution methods. Seventeen children (aged 4 to 33 months) were given aliquots of isotopically labeled water 1 week before and 6 hours after cardiac surgery. Isotope equilibration and analysis of the declining enrichment of daily urine samples allowed calculation of the total body water content. Before operation, total body water was significantly elevated (p < 0.001, Wilcoxon test); after operation it fell to approximately normal values. This finding is in contrast to those of previous reports, but may be explained in that the method used for calculation depended on measurements taken over a 7-day period rather than on a single measurement of isotope dilution as used elsewhere. Nevertheless, these results do suggest that surgery can correct the preoperative fluid overload. Comparison of deuterium and 18oxygen dilution methods showed a 2% to 2.5% overestimation of the total body water content with deuterium sampling.

Bioelectric impedance detects fluid retention in patients undergoing cardiopulmonary bypass

Excessive fluid accumulation is associated with increased morbidity and prolonged convalescence after cardiopulmonary bypass. However, water fluctuations are difficult to assess solely on the basis of changes in body weight and fluid balance. Bioelectric impedance analysis is a simple, rapid, noninvasive bedside technique that measures the resistance of the body to a weak alternating current (50 kHz). The change in resistance is inversely proportional to the change in total body water. To investigate the relationship between body weight, fluid balance, and resistance, 18 patients who had cardiopulmonary bypass (9 men, 9 women, aged 61 +/- 3 years, weighing 80 +/- 4 kg, with ejection fraction 54% +/- 3% and bypass time 113 +/- 8 minutes [mean plus or minus standard error of the mean]) were followed up for 7 postoperative days. Body weight, fluid balance, and whole body and regional resistance were determined at 24-hour intervals. In the immediate postoperative period, fluid retention was accurately detected by simultaneous measurements of weight gain and decreased resistance (p < 0.001). Both measurements detected the initiation of diuresis by postoperative day 2 (p < 0.01). Whole body resistance returned to baseline values by day 7 (p > 0.05), and body weight returned to baseline on day 4 (p > 0.05). Change in weight and change in whole body resistance were highly correlated with cumulative fluid balance (r = 0.84, p < 0.001, and r = -0.81, p < 0.001, respectively), and these two measures were also related to each other throughout the study (r = -0.89, p < 0.001). The initial change in resistance was the best measurement associated with postoperative outcome (p < or = 0.01). The data suggest that the measurement of electric resistance across the body can accurately detect acute changes in total body water and in fluid redistribution through the body. However, determining the relative day-to-day change in whole body resistance seems more appropriate than calculating absolute fluid changes over time. Bioelectric impedance offers a simple, rapid, noninvasive method to monitor serial changes in total body water. This technique can be useful in situations in which rapid alterations in water compartments occur, and it may be useful in predicting outcome after cardiopulmonary bypass.

Conversion of postischemic ventricular fibrillation with intraaortic infusion of potassium chloride

BACKGROUND

Ventricular fibrillation after declamping of the aorta after cardioplegic arrest is commonly managed by direct-current countershock. However, in coronary artery bypass grafting, placement of the electrodes can cause mechanical damage to the grafts and anastomoses, and the surgical procedure must be interrupted. As an alternative, intraaortic infusion of potassium chloride through the arterial line from the heart-lung machine was investigated.

METHODS

In a series of 100 patients with postischemic ventricular fibrillation (group P), 20 mmol of potassium chloride (plus 10 mmol later if necessary) was added to the oxygenator reservoir and perfused through the arterial line into the proximal aorta. The results were compared with those in a matched control group of 100 patients primarily treated with direct-current countershock (group DC).

RESULTS

In group P, the ventricular fibrillation was effectively converted to a supraventricular rhythm in 82% of the patients. The remaining 18 patients required significantly (p < 0.005) fewer electric shocks than the patients in group DC. Serum K+ levels were slightly elevated for a short period after the potassium chloride infusion. Otherwise there were no significant differences in regard to incidence of heart block, temporary epicardial pacing, myocardial infarction, or atrial fibrillation between the two groups.

CONCLUSIONS

Conversion of postischemic ventricular fibrillation with potassium chloride administered through the arterial line from the heart-lung machine is an effective, gentle, and convenient method. No side effects were noted.

Pulmonary edema and fluid mobilization as determinants of the duration of ECMO support

The physiological variables that govern recovery of pulmonary function during neonatal extracorporeal membrane oxygenation (ECMO) remain poorly understood. We hypothesized that pulmonary hypertension (PHN) resolves soon after starting ECMO and that neonatal weight gain, pulmonary edema, and fluid mobilization are major determinants of recovery of pulmonary function and the ability to decrease ECMO support. To evaluate this, 17 consecutive neonates requiring ECMO for severe respiratory failure were reviewed. PHN was studied by daily echocardiography to assess the direction of ductal shunting. To evaluate fluid flux, pulmonary function, and edema during ECMO, we measured body weight, urine output, and ECMO flow every 12 hours. To evaluate pulmonary edema, serial chest radiographs obtained every 12 hours were randomly reviewed and scored by two radiologists with a semiquantitative chest radiograph index score (CRIS). By 25% of bypass time, PHN had resolved in all patients. However, at that time, weight had increased to 9.16% +/- 1.78% above birth weight, and the CRIS was 44% worse than the value just prior to ECMO. From 25% time on bypass, as urine output increased, patient weight and CRIS progressively decreased, allowing ECMO support to be weaned. At the time of discontinuation of ECMO support, weight had decreased to 2.0% +/- 1.3% above birth weight, and urine output remained steady at 3.0 +/- 0.3 mL/kg/h. Within 24 hours of stopping ECMO, the CRIS showed a 58% improvement compared to maximal scores during ECMO. We conclude that PHN decreases early in ECMO and that edema and its mobilization are important determinants of the improvement in pulmonary function and duration of ECMO.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary artery occlusion pressure is not accurate immediately after cardiopulmonary bypass

Elevated pulmonary vascular resistance (PVR), differential cardiac dynamics, and increased lung water following cardiopulmonary bypass (CPB) have been proposed as limitations to the accuracy of the pulmonary artery occlusion pressure (PAOP) in estimating left ventricular preload. A prospective study of 22 patients undergoing elective myocardial revascularization is described wherein PAOP was compared with directly measured left atrial pressure (LAP). The reliability of PAOP to estimate LAP in the hour immediately following CPB and at 1, 4, 8, and 12 hours post-CPB was examined with repeated measures analysis of variance. Relationships between the PAOP-LAP difference and PVR, core temperature, arterial CO2 tension, and right and left ventricular stroke work indices (RVSWI, LVSWI) were tested by linear regression analysis. There was greater variability in measurements at 15, 30, and 45 minutes immediately after CPB, demonstrated by a pooled correlation coefficient of 0.73 versus 0.90 in the postoperative period. The degree of discrepancy between PAOP and LAP lessened with time. There was no determinable relationship of the PAOP-LAP gradient to PVR, level of PCO2, temperature, RVSWI, or LVSWI. Potential sources of discrepancy include airway pressure effects, position of the measuring catheters, positive end-expiratory pressure, infusion of protamine sulfate, extremes of pulmonary artery pressures, and effects of an open pericardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Rib cage mechanics after median sternotomy

A substantial reduction in lung volumes occurs after sternotomy, but the mechanism or mechanisms are unclear. Measurements were made of lung volumes and of chest wall motion with four pairs of magnetometers (two pairs for anteroposterior rib cage, one for lateral rib cage, and one for anteroposterior abdominal dimensions) in 16 men before and one week and three months after coronary artery grafting. Reductions in all lung volumes occurred after sternotomy and were greater in the supine than in the sitting position. Supine vital capacity was reduced one week after surgery, with almost complete recovery at three months. One week after sternotomy there was a significant reduction in tidal volume from a mean (95% confidence limits) value of 0.88 (0.76-1.00) litre to 0.61 (0.52-0.70) l, and in supine rib cage displacement from 3.87 (1.96-5.78) mm to 0.44 (-0.61-1.49) mm in the lateral plane. Respiratory frequency increased from 16 (13-19) to 21 (19-24)/min. Coordination of the rib cage was assessed by measuring the difference in timing of onset of chest wall motion and airflow in four planes. At one week nine of 14 patients showed uncoordination between airflow and rib cage motion in one or more dimensions, and this was still present in three patients at three months. No loss of the temporal relation between airflow and abdominal wall motion was detected. The results suggest that reduced and uncoordinated rib cage expansion contributes to the restrictive ventilatory defect that follows median sternotomy.

Unreliability of hemodynamic indexes of left ventricular size during cardiac surgery

Pulmonary artery diastolic (PADP) and wedge pressures (PAWP) and left ventricular end-diastolic pressure (LVEDP) are commonly used to estimate left ventricular (LV) preload. To assess the ability of hemodynamic indexes of preload to estimate anatomical preload, or LV volume, we studied 45 patients during a coronary (18 patients) or aortic valve (27 patients) procedure and compared epicardial two-dimensional echocardiographic LV cavity area with simultaneous measurements of PADP, PAWP, and high-fidelity LVEDP. Pulmonary artery diastolic pressure, PAWP, and their percent change after bypass did not correlate with absolute values (before or after bypass) or percent change in LVEDP. Percent change in LV area correlated weakly with percent change in PADP (r = .34, p less than .03) but not with changes in PAWP or LVEDP. Changes were opposite in direction in 45% (PADP), 50% (PAWP), and 67% (LVEDP) of patients. In conclusion, both PADP and PAWP were poor guides to LVEDP and neither reflected changes in LV size. Thus, hemodynamic indexes of preload should be used with caution during cardiac operations.

Hetastarch as a prime for cardiopulmonary bypass

Hetastarch, a synthetic colloid osmotic plasma volume expander, was employed in a prime for cardiopulmonary bypass in 37 patients undergoing myocardial revascularization. Comparison of laboratory values to those of 42 patients undergoing myocardial revascularization using an albumin-containing prime showed lower postoperative platelet counts (p less than 0.02) with hetastarch. There were no differences in chest tube drainage, blood use, plasma hemoglobin, fibrinogen levels, of coagulation times. The hetastarch prime cost $119.50 per patient, whereas the albumin-containing prime cost $321.35 per patient.

The blood volume and the renin-angiotensin-aldosterone system following open-heart surgery

The circulating blood volume changes, plasma electrolytes, aldosterone as well as plasma-renin-activity (PRA) were studied in 14 patients following open-heart surgery with cardiopulmonary bypass (CPB) and in 14 patients following cardiac surgery without CPB. In both the groups a postoperative decrease of circulating blood volume was observed. This decrease occurred in spite of the positive fluid balance, and so a shift of fluid from vascular to extravascular compartment was likely. In the bypass group the plasma aldoserone level rose immediately after the operation and reached the peak on the first postoperative day. In the non-bypass group the aldosterone level started to fall after the operation, and reached the lowest level on the third postoperative day. The pattern of the postoperative PRA changes was almost identical with the aldosterone level changes in both the groups studied, which suggests that the activation of renin-angiotensin-aldosterone axis might be responsible for the observed plasma aldosterone changes.

Biochemical changes in extracorporeal circulation in patients

The effect of priming extracorporeal perfusion pumps with 50% and 80% diluted homologous blood on the serum electrolytes, acid-base status and plasma osmolality has been investigated in 103 patients undergoing open-heart surgery for congenital and acquired heart disease. The value in prognosis of plasma osmolality is discussed.

Plasma and tissue digoxin concentrations in patients undergoing cardiopulmonary bypass

Plasma myocardial, and skeletal muscle digoxin concentrations were measured in 32 patients undergoing cardiopulmonary bypass who were on long-term treatment with digoxin. The patients were divided into 4 groups according to the daily digoxin dose and the interval between discontinuation of the drug and operation. Before bypass, the mean digoxin concentrations were 1.58 nmol/l (1.24 ng/ml) in plasma 65.2 nmol/kg (50.9 ng/g) in the atria, 121.4 nmol/kg (94.98 ng/g) in 11 papillary muscles, and 16.6 nmol/kg (13.0 ng/g) in skeletal muscle. Mean atrial digoxin concentrations were significantly lower tham mean papillary muscle concentrations in 11 patients. Ratios of plasma of myocardial or skeletal muscle digoxin concentrations were very variable. Generally digoxin concentrations were higher in patients on the larger digoxin dose and with the shorter discontinuation time before surgery. These differences attained significance only with plasma digoxin concentrations. There was a slight fall in plasma digoxin concentration during cardiopulmonary bypass but no significant differences were observed between plasma, atrial, or skeletal muscle digoxin concentrations before and at the end of bypass. No clear relation was seen between plasma or atrial digoxin concentrations and postoperative cardiotoxicity. Stopping digoxin 48 hours before operation appeared to account for pre- or post-bypass plasma digoxin concentrations of less than 1.0 nmol/l (0.8 ng/ml) in most of the instances encountered, whereas the 3 patients who developed pulsus bigeminus postoperatively had received 0.5 mg digoxin only 24 hours before operation.

Osmolal balance after open intracardiac operations in children

Deverall, P. B., Muss, D. C., Macartney, F. J., and Settle, J. D. (1973).Thorax,28, 756-761. Osmolal balance after open intracardiac operations in children. Changes in plasma osmolality, urine osmolality, urine volume, total osmolal output, and free osmolal output have been studied in children between 2 and 10 years of age. All underwent elective open intracardiac operations.

Plasma hypo-osmolality develops after operation, and this was not influenced by altering the osmolal concentration of the prime in the extracorporeal system nor was it affected by severe water restriction in the immediate postoperative period. During the first 48 hours a water diuresis was not seen even in the presence of marked plasma hypo-osmolality.

Urine volume, urine osmolality, and solute concentration in the kidney are affected by both the perfusate prime and postoperative fluid regime. As the total osmolal output was the same in all study groups, there was an inverse relation between urine volume and urine osmolality.

The data obtained show no evidence of postoperative renal dysfunction. Free osmolal output, a measure of solute and water excretion, showed a normal renal response to a solute load but an abnormal response to a water load.

The data support the use of moderate haemodilution in the perfusate prime, the precise osmolal concentration not being of major importance. Postoperatively a regime of moderate fluid restriction is supported.