An open-source high-frequency lock-in amplifier.

We present characterization of a lock-in amplifier based on a field programmable gate array capable of demodulation at up to 50 MHz. The system exhibits 90 nV/√Hz of input noise at an optimum demodulation frequency of 500 kHz. The passband has a full-width half-maximum of 2.6 kHz for modulation frequencies above 100 kHz. Our code is open source and operates on a commercially available platform.

Massive right atrial myxoma causing exertional dyspnoea.

Metastatic tumours are the commonest cardiac tumours being found in 1-3% of patients dying of cancer while primary tumours are unusual and have an incidence of 0.02-0.5%. The majority (80%) of all primary cardiac tumours are benign with myxomas accounting for 50%. Myxomas arising from the right atrium are uncommon. We present the case of a 39-year-old female with a 4-month history of progressive exertional dyspnoea accompanied by symptoms of palpitations and presyncope. Transthoracic echocardiography showed an extremely large right atrial myxoma prolapsing into the right ventricle and obstructing the tricuspid valve. We demonstrate how intraoperative transoesophageal echocardiography, prior to sternotomy, was useful in providing information about the myxoma which clearly displayed its attachment and anatomical relationship in the planning of the 'safe' surgical excision.

Evaluation of the Sorin bicarbon bileaflet valve in 488 patients (519 prostheses).

The Sorin bicarbon bileaflet prosthesis was introduced in 1990. To evaluate the clinical performance of this prosthesis, we reviewed 519 prostheses that were implanted in 488 patients (275 men, 213 women; mean age 59 years; SD 10.8, range 19 to 88) from 1993 to 1997. Preoperatively, 82% of patients were in New York Heart Association (NYHA) functional class III or IV. There were 263 aortic valve replacements (AVRs) (54%), 194 mitral valve replacements (MVRs) (40%), and 31 AVRs and MVRs (both) (6%). Concomitant procedures were performed in 82 patients (17%). Follow-up was complete in 471 (97%) with a total cumulative follow-up of 866 patient-years. The 30-day mortality for patients with AVR was 5.7% (95% confidence interval [CI] 2.9 to 8.5), MVR 17.5% (CI 9.9 to 19.7), and both 19% (CI 7.6 to 51.1), with no early valve-related deaths. Patient survival at 55 months was 76% (SE 2.27%), with patients with AVR being 90%, MVR 63%, and both 61%. This was influenced by the following: (1) valve position, which was higher for MVR (p = 0.0001); (2) poor NYHA functional class (p = 0.0006); (3) reoperation (p = 0.02); and (4) age >70 years (p = 0.0001). Valve-related complications (expressed as percentage per patient year and number of events) were major thromboembolism at 0.9% per year (8), with AVR rates being 1.2% per year (6) and MVR 0.7% per year (2); major hemorrhage at 2.3% per year (20) with AVR rates being 2.4% per year (12) and MVR 2.5% per year (7); bacterial endocarditis at 0.2% per year (2); and nonstructural dysfunction rate of 0.7% per year (6). The reoperation rate was 0.9% per year (8) with AVR being 0.6% per year (3) and MVR 1.7% per year (5). At 55 months, actuarial freedom from major thromboembolism was 97% (SE 1.1%) with AVR being 96% and MVR 98%; major hemorrhage 89% (SE 3.1%) with AVR being 88.6% and MVR 91%; structural valve dysfunction 100% (SE 0.0%); and reoperation 97.1% (SE 1.10%) with AVR being 98.5% and MVR 94.6%. At follow-up, 88% of survivors were in NYHA class I or II. In this series, hospital mortality and overall survival in patients were influenced by the patients' clinical characteristics. There were no early valve-related deaths. Valve-related complications were similar to previously reported series with no episode of structural failure. Our experience with the Sorin bicarbon bileaflet prosthesis suggests that it has a satisfactory clinical performance, with low complication rates.

von Willebrand factor, fibrinogen, and soluble P-selectin levels after mitral valve replacement versus mitral valve repair.

Patients with mitral valve disease undergoing surgery are at an increased risk of thromboembolism. We hypothesized that this may be due in part to abnormalities in platelet activation, endothelial damage or dysfunction, and plasma fibrinogen in such patients. To test this hypothesis, we measured indexes of platelet activation (soluble P-selectin), endothelial damage or dysfunction (von Willebrand factor [vWf], enzyme-linked immunosorbent assay) and fibrinogen (modified Clauss) in 56 consecutive patients (35 women, mean age 65 years) admitted for isolated mitral valve repair (n = 39) or replacement (using mechanical implants, n = 17). Samples were taken from a peripheral vein before and at 3 months after valve surgery. Baseline results were compared with 56 healthy age- and sex-matched controls. Compared with controls, patients with mitral valve disease had higher levels of vWf (mean +/- SD 132 +/- 28 vs 101 +/- 35 IU/dl; p <0.001), but there were no significant differences in mean fibrinogen (p = 0.418) or soluble P-selectin (p = 0.855) levels between cases and controls. There was a significant increase in plasma vWf after mitral valve replacement: 142 +/- 25 IU/dl preoperatively, increasing to 161 +/- 33 IU/dl at 3 months after surgery (p = 0.0261). However, there were no significant changes in plasma fibrinogen (p = 0.306) or soluble P-selectin levels (p = 0.191). Patients undergoing mitral valve repair did not have any significant changes in mean vWf (p = 0.25), soluble P-selectin (p = 0.77), or fibrinogen (p = 0.22). There was a significant negative correlation (Spearman, r = -0.4, p = 0.003) in postoperative plasma vWf levels and the size of valve prosthesis used. Thus, patients with mitral valve disease have increased plasma vWf levels when compared with healthy controls, suggesting endothelial damage or dysfunction, with a further increase in levels after mitral valve replacement. Conversely, patients undergoing mitral valve repair do not demonstrate any significant changes in fibrinogen, or indexes of endothelial dysfunction or platelet activation.

Effect of aortic valve replacement on plasma soluble P-selectin, von Willebrand factor, and fibrinogen.

We measured indexes of platelet activation (soluble P-selectin), endothelial dysfunction (von Willebrand factor), and fibrinogen in 54 patients who underwent aortic valve replacement (AVR): after mechanical AVR implantation, there was a significant increase in plasma levels of soluble P-selectin and von Willebrand factor levels 3 months after surgery, with no change in mean plasma fibrinogen levels. No significant changes in measured indexes were noted in patients undergoing biologic AVR, suggesting that mechanical AVR results in abnormal endothelial damage and/or dysfunction and platelet activation, which is not apparent among patients undergoing this procedure.

Alpha-stat acid-base regulation during cardiopulmonary bypass improves neuropsychologic outcome in patients undergoing coronary artery bypass grafting.

Neuropsychologic impairment in patients undergoing cardiopulmonary bypass may be associated with cerebral blood flow changes arising from different management protocols for carbon dioxide tension during bypass. Seventy patients having coronary artery bypass grafting were randomized to either pH-stat or alpha-stat acid-base management during cardiopulmonary bypass with a membrane oxygenator. In each patient, cerebral blood flow (xenon 133 clearance), middle cerebral artery blood flow velocity (transcranial Doppler sonography), and cerebral oxygen metabolism (cerebral metabolic rate and cerebral extraction ratio) were measured during four phases of the operation: before bypass, during bypass (at hypothermia and at normothermia), and after bypass. A battery, of neuropsychologic tests were also conducted before and 6 weeks after the operation. During hypothermic (28 degrees C) bypass, cerebral blood flow was significantly (p < 0.001) greater in the pH-stat group (41 mlx100 gm(-1)xmin(-1); 95% confidence interval 39 to 43 mlx100 gm(-1)xmin(-1)) than in the alpha-stat group (24 mlx100 gm(-1)xmin(-1); confidence interval 22 to 26 mlx100 gm(-1)xmin(-1)) at constant pressure and How. Arterial carbon dioxide tensions were 41 mm Hg (40 to 41 mm Hg) and 26 mm Hg (25 to 27 mm Hg), respectively; pH was 7.36 (7.34 to 7.38) and 7.53 (7.51 to 7.55), respectively. Middle cerebral artery flow velocity was significantly (p < 0.05) reduced in the alpha-stat group to 87% (77% to 96%) of the prebypass value, whereas it was significantly (p < 0.05) increased (152%; 141% to 162%) in the pH-stat group. Cerebral extraction ratio for oxygen demonstrated relative cerebral hyperemia during hypothermic (28 degrees C) bypass in both the pH-stat and alpha-stat groups (0.12 [0.11 to 0.14] and 0.25 [0.22 to 0.28], respectively); however, hyperemia was significantly more pronounced in the pH-stat group, indicating greater disruption in cerebral autoregulation. Neuropsychologic impairment criteria of deterioration in results of three or more tests revealed that a significantly (Fisher's exact test, p = 0.02) higher proportion of patients in the pH-stat group fared poorly than in the alpha-stat group at 6 weeks (17/35, 48.6% [32% to 65.1%], and 7/35, 20% [6.7% to 33.2.2%], respectively). In conclusion, patients receiving alpha-stat management had less disruption of cerebral autoregulation during cardiopulmonary bypass, accompanied by a reduced incidence of postoperative cerebral dysfunction.

Primary left atrial fibrosarcoma.

An elderly female with refractory cardiovascular symptoms due to functional mitral stenosis secondary to a primary left atrial fibrosarcoma is described. The symptoms are often nonspecific and most of the patients present first time with hemodynamic compromise. A high index of suspicion is essential for the early diagnosis of these highly malignant cardiac tumors because of their rarity, a wide spectrum of nonspecific symptoms and poor survival.

Cardiopulmonary bypass: perioperative cerebral blood flow and postoperative cognitive deficit.

Increased cerebral blood flow occurring during cardiopulmonary bypass as a result of changes in arterial carbon dioxide tension during acid-base regulation is thought to increase postoperative cognitive dysfunction. We studied 70 patients undergoing coronary artery bypass procedures who were randomized to two different acid-base protocols: pH-stat or alpha-stat regulation. Cerebral blood flow, cerebral blood flow velocity, and cerebral oxygen metabolism were measured before bypass, during bypass (hypothermic [28 degrees C] and normothermic phases), and after bypass. Detailed cognitive tests were conducted before operation and 6 weeks after operation. During 28 degrees C bypass, cerebral blood flow was significantly (p < 0.05) higher in the pH-stat group than in the alpha-stat group (41 +/- 2 versus 24 +/- 2 mL.100 g-1.min-1), and cerebral blood flow velocity was significantly increased in the pH-stat group and significantly decreased in the alpha-stat group (152% +/- 10% versus 78% +/- 7%). Cerebral extraction ratio of oxygen demonstrated a relatively greater disruption of autoregulation in the pH-stat group than in the alpha-stat group with relative hyperemia of 0.12 +/- 0.02 versus 0.26 +/- 0.03, respectively, during 28 degrees C bypass. Using the criterion of deterioration in three or more neuropsychologic tests, a significantly higher proportion of patients in the pH-stat group fared less well than in the alpha-stat group (49% +/- 17% versus 20% +/- 13%). Patients in the alpha-stat group experienced less disruption of cerebral autoregulation during hypothermic cardiopulmonary bypass, and this was accompanied by a reduction in postoperative cognitive dysfunction.

Elective pneumonectomy: factors associated with morbidity and operative mortality.

We have retrospectively reviewed hospital records of 197 consecutive patients undergoing pneumonectomy for neoplastic disease between 1985 and 1990 to identify predictors of outcome. Seventeen of the 197 patients died during their hospital stay (8.6%; 95% confidence intervals, 6.7% to 11.2%). The most significant predictors of in-hospital mortality were presence of coexisting medical conditions (p less than 0.001), respiratory function tests showing an obstructive picture with a forced expiratory volume in 1 second/forced vital capacity ratio of less than 0.55 (p less than 0.001), 24-hour fluid replacement of more than 3 L (p less than 0.05), postoperative pulmonary edema (p less than 0.001), respiratory tract infection with positive sputum culture (p less than 0.01), postoperative renal failure (p less than 0.001), and cardiac arrhythmias (p less than 0.001). There were 232 postoperative management, problems occurring in 197 patients. The most significant predictors of postoperative morbidity were continued cigarette smoking up to the time of operation (p less than 0.05), perioperative blood loss or more than 2 L (p less than 0.05), and infusion of more than 3 L of fluid in the first 24 hours (p less than 0.05). Although retrospective analyses must be interpreted with caution, this study has identified preoperative and perioperative factors associated with in-hospital morbidity and mortality after pneumonectomy.

Relative changes in cerebral blood flow during cardiac operations using xenon-133 clearance versus transcranial Doppler sonography.

BACKGROUND: Changes in cerebral blood flow (CBF) during cardiac operations have implications in terms of postoperative neurologic and neuropsychological dysfunction. Current techniques of CBF measurement are cumbersome and invasive. Transcranial Doppler sonography offers a noninvasive means of assessing changes in CBF. The aim of this study was validation of this technique with existing methods of CBF measurement during cardiac operations. METHODS: We compared the changes in CBF using xenon-133 clearance with changes in middle cerebral artery velocity by transcranial Doppler sonography (VMCA) using pH-stat and alpha-stat acid-base management during cardiopulmonary bypass. Measurements were taken (1) before bypass, (2) at 28 degrees C on bypass, (3) at 37 degrees C on bypass, and (4) after bypass. Relative changes in CBF and VMCA, calculated as the percent change from the prebypass baseline value normalized to 100%, were used in this analysis. RESULTS: During the hypothermic phase of cardiopulmonary bypass, CBF and VMCA increased by 45.9% and 51.8%, respectively (p < 0.001), during pH-stat acid-base management but decreased by only 26.4% and 22.4%, respectively (p < 0.0001), during alpha-stat acid-base management. Linear regression analysis of the absolute changes in CBF (mL . 100 g-1 . min-1) and VMCA (cm/s) showed a significant correlation (r = 0.60; r2 = 0.36; p < 0.0001), but a better correlation was obtained when relative changes in CBF and VMCA were compared (r = 0.89; r2 = 0.79; p < 0.0001). CONCLUSIONS: Measurements of VMCA, expressed as relative changes of a pre-cardiopulmonary bypass level (using the noninvasive transcranial Doppler sonographic technique), can be used to examine CBF changes during cardiopulmonary bypass.

Retrograde cerebral perfusion: clinical experience in emergency and elective aortic operations.

We recently have used retrograde cerebral perfusion via the superior vena cava in association with hypothermic circulatory arrest as an adjunct to cerebral protection during aortic arch operations. Between April 1993 and March 1994, 23 patients (14 male; 9 female; median age, 64 years; age range, 25 to 76 years; 14 emergency, 9 elective) underwent operation on the ascending aorta, aortic arch, or both for acute dissection (11) or aneurysm (12). Aortic root replacement was performed in 13 patients (7 with arch replacement), ascending aortic replacement in 7 (4 with arch replacement), isolated aortic arch replacement in 2, and repair of sinus of Valsalva aneurysm in 1. Coronary artery bypass grafting was performed in 4 patients. Hypothermic circulatory arrest (15 degrees C) and retrograde cerebral perfusion were implemented in all cases (median circulatory arrest time, 21 minutes; range, 13 to 51 minutes; median retrograde cerebral perfusion time, 20 minutes; range, 12 to 50 minutes). Three hospital deaths occurred (atheromatous embolic stroke, sepsis, rupture of infrarenal aortic aneurysm). The remaining patients had no neurologic damage (median intensive therapy unit stay, 1 day; range, 1 to 5 days). Retrograde cerebral perfusion is easy to establish and safe, and may improve brain protection during hypothermic circulatory arrest.

Hospital morbidity and mortality and changes in quality of life following mitral valve surgery in the elderly.

BACKGROUND AND AIM OF THE STUDY: An increasing number of elderly patients are now requiring mitral valve surgery (MVS). However, due to a perceived increase in risk of morbidity and mortality following cardiac surgery, many elderly patients tend to be neglected or not referred for surgery. METHODS: The outcome of MVS in terms of hospital morbidity and mortality, length of intensive care unit (ICU) and hospital stays, and change in NYHA functional class and quality of life following surgery was assessed in 43 elderly patients (18 males, 25 females; median age 77 years (IQR 75-82 years)) who underwent primary open mitral valve repair (MVRr) or replacement (MVR) between November 1994 and September 1997. Their preoperative clinical characteristics, incidence of hospital morbidity, hospital mortality and length of ICU and hospital stays following MVS were recorded. At follow up, NYHA class was assessed and quality of life parameters monitored using the SF-36 questionnaire. RESULTS: At surgery, 69% of patients were in NYHA class III/IV, 36% underwent non-elective surgery and 44% had symptoms of more than three years' duration. Among patients, 80% presented with mitral incompetence and MVRr was undertaken in 51%. The median bypass and cross-clamp times for MVRr were significantly longer than for MVR. After surgery, 98% of patients required inotropic support, 9% renal dialysis, and 42% ventilatory support for >24 h. In addition, 37% developed respiratory complications, 12% renal failure, 19% needed re-exploration for bleeding, and 5% suffered a stroke. The mean ICU stay after surgery was three days; average in-hospital stay was 10 days. The 30-day mortality rate was 22.7% after MVRr and 38% after MVR. There was a significant improvement in energy, and role limitation due to physical and mental health after MVS. CONCLUSIONS: Elderly patients underwent MVS, usually after a degree of clinical deterioration. Although morbidity and mortality following mitral valve surgery were high, at follow up there was a significant improvement in both symptoms and quality of life of survivors.

A prospective study of changes in patients' quality of life after aortic valve replacement.

BACKGROUND AND AIM OF THE STUDY: After aortic valve replacement (AVR), 90% of survivors are in NYHA class I or II, and most return to work after three months. It is unclear, however, whether at that time patients have an improved quality of life (QOL), are able to perform physical and social activities, and live independently. METHODS: To assess this situation, 62 patients (39 males, 23 females; mean age 68.5 +/- 10 years) who underwent primary AVR completed the validated Short Form 36 (SF-36) questionnaire. QOL parameters were determined before and three months after surgery prospectively, and analyzed using the Wilcoxon matched pairs rank test. RESULTS: All patients showed significant improvement in all eight QOL parameters (score 0-100): (i) physical function (67 +/- 26 versus 37 +/- 28; p <0.00001); (ii) role limitation due to physical function (52 +/- 43 versus 20 +/- 37; p <0.0001); (iii) social function (80 +/- 25 versus 59 +/- 30; p <0.0001); (iv) role limitation due to emotional problems (64 +/- 41 versus 41 +/- 46; p = 0.01); (v) energy (62 +/- 22 versus 42 +/- 23; p <0.00001); (vi) mental health (78 +/- 19 versus 63 +/- 22; p <0.00001); (vii) pain (78 +/- 27 versus 67 +/- 32; p = 0.02); and (viii) general health perception (72 +/- 20 versus 58 +/- 21; p <0.00001). Significant improvements in QOL parameters were: (i) after mechanical and bioprosthetic AVR, seven of eight QOL parameters were improved; (ii) patients aged < 70 years had pronounced improvement in six of seven parameters, while those aged > or = 70 years had limited improvement in five of eight parameters; (iii) patients with valve sizes 19 and 21 mm improved in five of eight parameters, while those with > or = 23 mm implants improved in all eight parameters, regardless of post-AVR peak gradient of < 20 or > or = 20 mmHg; and (iv) patients with left ventricular end-diastolic dimension (LVEDD) < 55 mm improved in all eight parameters while those with LVEDD > or = 55 mm improved in only five parameters. CONCLUSION: There was significant improvement in patients' QOL at three months after AVR, regardless of the type of aortic implant used; improvement was greatest in those aged < 70 years. The results also suggest that patients with smaller implants (who were older) and those with LVEDD > or = 55 mm were less likely to show significant improvement in all QOL parameters at three months after AVR.

A prospective study of changes in the quality of life of patients following mitral valve repair and replacement.

OBJECTIVE: The primary aim of medical care and surgery for mitral valve disease is to improve the overall functional capacity and health of patients. AIM: To assess whether there was an actual improvement in quality of life (QOL) of patients 3 months following primary mitral valve repair (MRr) or mitral valve replacement (MVR). METHODS: Prospective study of 61 consecutive patients (34 males, mean age 64+/-12) who underwent primary, isolated mitral valve repair (MRr, n=40) or mitral valve replacement (MVR, n = 21) from April 1997 to October 1998. QOL parameters using the validated short form 36 (SF-36) questionnaire were determined before and at 3 months after surgery and analysed using the Wilcoxon matched pairs rank test. RESULTS: Mean QOL scores (scale 0-100) for all patients following mitral valve surgery showed clinical and statistically significant improvement in seven of eight QOL parameters, namely (i) physical function (post, 60+/-31 vs. pre, 44+/-29; P = 0.0001); (ii) role limitation due to physical function (50+/-42 vs. 23+/-36; P = 0.0002); (iii) social function (76+/-31 vs. 59+/-36; P = 0.0006); (iv) role limitation due to emotional problems (65+/-42 vs. 44+/-45; P = 0.003); (v) energy (57+/-24 vs. 40+/-24; P < 0.0001); (vi) mental health (73+/-20 vs. 66+/-21; P = 0.007); and (vii) general health perception (68+/-19 v 56+/-22; P = 0.0001); but not pain (73+/-29 v 71+/-30; P = 0.4). Following MRr there was significant improvement in seven of eight QOL parameters and following MVR there was significant improvement in three of eight QOL parameters. Whilst patients with ejection fraction > or = 50% showed significant improvement in seven of eight QOL parameters, there was no significant improvement in any QOL parameters in patients with impaired left ventricular (LV) function. Similarly, patients with mitral regurgitation with end-systolic dimensions of > or = 45 mm showed no significant improvement in any QOL parameters at 3 months follow-up. CONCLUSIONS: Our study suggests that following mitral valve surgery there was significant improvement in the QOL of patients especially in those patients requiring mitral valve repair. However, patients with impaired LV function and those with MR with end-systolic dimensions > or = 45 mm were unlikely to demonstrate a significant improvement in QOL at 3 months follow-up.

Hyperperfusion and cerebral dysfunction. Effect of differing acid-base management during cardiopulmonary bypass.

Alterations in cerebral blood flow (CBF) occurring during cardiopulmonary bypass (CPB), which are thought to be responsible for increased morbidity, are probably related to changes in arterial carbon dioxide during acid-base management. In this study, 70 patients undergoing elective coronary artery bypass surgery (CABS) were randomised to one of two differing, but widely practised, cardiopulmonary bypass acid-base protocols; pH-stat and alpha-stat. Cerebral blood flow was measured during surgery using the xenon-133 isotope clearance technique. Cerebral oxygen metabolism was measured as the cerebral metabolic rate for oxygen (CMRO2) and matching of the cerebral blood flow to oxygen demand as the cerebral extraction ratio for oxygen (CERO2). Detailed neuropsychological tests were conducted in all patients before surgery and repeated at 6 weeks after surgery for assessment of changes in cognitive function. During hypothermic (28 degrees C) CPB, CBF was significantly greater (P < 0.001) in the pH-stat group (41 ml/100 g per min; 95% confidence intervals (CI), 39-43) than in the alpha-stat group (24 ml/100 g per min; 95% CI, 22-26). The cerebral extraction ratio for oxygen indicated a degree of mismatch of cerebral perfusion and demand during CPB in both pH-stat and alpha-stat groups (0.12; 95% CI, 0.11-0.14 and 0.25; 95% CI, 0.22-0.28, respectively). This mismatch was far more pronounced in the pH-stat group than in the alpha-stat group, indicating greater disruption in cerebral autoregulation in the former group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of differing acid-base regulation on cerebral blood flow autoregulation during cardiopulmonary bypass.

Cerebral dysfunction following cardiopulmonary bypass may be aggravated by altered autoregulation of cerebral blood flow. We have used trans-cranial Doppler to measure middle cerebral artery blood flow velocity during cardiopulmonary bypass managed by either pH-stat or alpha-stat acid-base protocols. Fourteen patients were studied, 7 in each group. During bypass at 28 degrees C, patients underwent incremental alterations in mean arterial pressure from 20-90 mmHg, maintaining systemic perfusion flow at 1.75 L/min per m2. The cerebral extraction ratio of oxygen was measured to indicate matching of cerebral blood flow to demand. The pH-stat group showed a pressure passive cerebral circulation with significant (r = 0.999, P less than 0.05) increase in blood flow velocity with increasing arterial pressure. This also occurred in alpha-stat group during the pressure range of 20-50 mmHg (r = 0.951, P less than 0.05). During the pressure range of 50-90 mmHg in alpha-stat group the change in flow velocity (0.16 cm/sec per mmHg) was significantly (P less than 0.05) less than that in pH-stat group (0.58 cm/second per mmHg). The cerebral extraction ratio of oxygen was less depressed in the alpha-stat group than in the pH-stat group, indicating more appropriate matching of cerebral blood flow and tissue demand. These results suggest that, during alpha-stat managed cardiopulmonary bypass, cerebral blood flow velocity is less subject to wide pressure alteration than pH-stat.

Hemofiltration in a cardiac intensive care unit: time for a rational approach.

The typical annual expenditure for patients requiring continuous hemofiltration (CHF) is high. To audit the benefit of this expensive treatment, the outcome of 48 consecutive patients (34 men, 14 women; mean age, 65 years) requiring hemofiltration for acute renal failure was analyzed during a period of 24 months. The operations performed were 26 CABG, 8 AVR, 3 AVR/MVR, 2 post infarction VSD repairs, and 1 thoracoabdominal aneurysmectomy. Indications for hemofiltration were oliguria and fluid overload in 69%, uremia in 56%, acidosis in 33%, and hyperkemia in 13%. Twenty five patients (52%) died while in the hospital, and 10 more died within 9 months of discharge. Of the remaining 13 survivors, 6 (46%) were classified as III or IV according to the New York Heart Association classification system. The mean ITU and hospital stay per patient requiring CHF was 15.3 days and 25.4 days, respectively. There were no statistically significant differences between patients who did and did not survive in the hospital in age, pre-operative renal function, ejection fraction, duration of cardiopulmonary bypass, or urine output before CHF. However, there were no survivors when the cardiac index was less than 1.7 L/m2 and adrenalin requirement was more than 30 micrograms/min before CHF (seven patients). These results suggest that the short- and long-term outcome in patients requiring CHF after cardiac surgery is poor. Considering the large demand on resources, the use of CHF should be rationalized, particularly in patients with persistent low cardiac output.