Role of L-arginine-derived NO in ischemic acute renal failure in the rat

Nitric oxide (NO) is involved in the regulation of renal perfusion and glomerular hemodynamics under basal conditions. We examined the hypothesis that L-arginine-derived NO modifies ischemic acute renal failure (ARF) in the rat. After a basal period ischemia was induced by clamping of both renal arteries (40 min). Thereafter, in the reperfusion period, we intravenously infused L-arginine (Arg, 300 mg/kg/60 min), or L-monomethylarginine (MeArg, 30 mg/kg/60 min), or Arg + MeArg (300 mg/kg/60 min, 30 mg/kg/60 min, resp.). Besides monitoring of urinary flow rate and arterial blood pressure, and determination of sodium excretion, glomerular filtration rate (GFR, mL/min/100 g) was estimated at the end of the infusion period and again after another 30 and 120 min by inulin clearance (fluorescence-marked inulin). In the basal period GFR showed no differences between the groups (Arg: 0.86 +/- 0.07, MeArg: 0.92 +/- 0.06, Arg + MeArg: 0.89 +/- 0.08, control: 0.84 +/- 0.07). At 180 min after the beginning of the reperfusion period, GFR was 0.13-0.02 in the control group. After administration of Arg, a remarkable and persistent increase in GFR was observed (0.28 +/- 0.03), whereas infusion of MeArg showed no significant effects (0.13 +/- 0.04). Combined administration of Arg + MeArg revealed a moderate increase of GFR (0.19 +/- 0.05), ranging between the Arg and the control group. Also, 60 and 90 min after the beginning of the reperfusion period, the highest values for GFR were obtained in the Arg group. We conclude that in this model of ischemic ARF in the rat, L-arginine-derived NO is capable of improving renal function. These data underline the regulatory role of the L-Arg-NO pathway for renal function, not only under normal conditions, but also in ARF.

Fabrication and evaluation of an etched infrared diffraction grating

We evaluated the optical performance of an IR echelle grating produced on a silicon wafer with anisotropic etching techniques. We measured the diffraction efficiency of a sample with a 55° blaze angle and 25-µm groove spacing. We also calculated the efficiency for typical triangular and trapezoidal groove profiles of etched gratings. The diffraction efficiency for unpolarized light can be approximately as high as the efficiency of right-angle groove gratings. The great potential of the etched silicon grating lies in its ease of fabrication, its excellent surface quality, and the high reproducibility of the production process. Compact high-resolution diffraction gratings can be produced by etching the grating pattern into the rear side of a transparent prism. When used in internal reflection, this increases the resolving power of the grating by a factor equal to the refractive index of the prism over a front surface grating of the same length.

Structural valve deterioration in elderly patient populations with the Carpentier-Edwards standard and supra-annular porcine bioprostheses: a comparative study

From 1975 to 1989, over 1400 patients in the elderly population and over 1700 patients under 65 years of age received the Carpentier-Edwards standard (CE-Standard) and supra-annular porcine (CE-SAV) bioprotheses. The mean ages of the patients receiving the two protheses within the three subgroups of the elderly population-65-69 years, 70-79 years, and 80 years and over-were relatively similar. There was no statistically significant difference in the performance of the prostheses regarding structural valve deterioration (SVD) at seven years. The freedom from SVD for aortic valve replacement in the 65-69 years group at seven years was 98.7% +/- 1.3% for the CE-Standard and 98.7% +/- 1.0% for the CE-SAV, for both the 70-79 years group and the 80 years and over group the figure was 100% for both prostheses (p = NS). The freedom from SVD after mitral valve replacement in the 65-69 years group at seven years was 90.0% +/- 4.3% for the CE-Standard and 84.8% +/- 7.5% for the CE-SAV, for the 70-79 years group it was 95.3% +/- 3.2% and 95.5% +/- 3.6% respectively and for the 80 years and over group the figure was 100% for both prostheses (p = NS within groups). The long term freedom from SVD after aortic valve replacement was 98.4% +/- 3% at 15 years for the CE-Standard in the 65-69 years group, 94.9% +/- 5% at 13 years for the 70-79 years group and 100% at 13 years for the 80 years and over group.(ABSTRACT TRUNCATED AT 250 WORDS)

Embolic occlusion of a patent foramen ovale: a cause of false negative contrast echocardiogram

A 74-year-old man who had dyspnea and cyanosis demonstrated venous thrombosis and multiple lung ventilation-perfusion mismatches suggesting pulmonary emboli. Transthoracic echocardiography demonstrated a right atrial mass and a microbubble contrast study did not reveal right-to-left shunt. Transesophageal echocardiography revealed an embolus entrapped in the foramen ovale projecting into the left atrium that was subsequently removed. Embolic occlusion of patent foramen ovale is an important cause of false negative microbubble contrast study.

The effects of normovolemic hemodilution with dextran-40 on acute myocardial ischemia/reperfusion injury in rabbits

The effects of decreasing blood viscosity by normovolemic hemodilution with dextran-40 or normal saline (NS) on myocardial lipid peroxides, superoxide dismutase, infarct size and left ventricular function during acute myocardial ischemia/reperfusion were studied in rabbits. It was found that normovolemic hemodilution with dextran-40 could decrease the content of ischemic myocardial malondialdehyde and preserve ischemic myocardial superoxide dismutase activity after 1 h of coronary occlusion followed by 1 h of reperfusion. However, after administration of NS only a tendency in this aspect exhibited without statistical significance. Besides, hemodilution with dextran-40 reduced infarct size and improved left ventricular systolic function after 1 h of ischemia followed by 23 h of reperfusion. These results suggest that normovolemic hemodilution with dextran-40 may have anti-injury effect on acute myocardial ischemia/reperfusion to a certain degree.

The Carpentier-Edwards supra-annular porcine bioprosthesis: clinical performance to 8 years of a new generation porcine bioprosthesis

The Carpentier-Edwards supra-annular porcine bioprosthesis has been utilized at the University of British Columbia since its introduction in 1982. The prosthesis was designed to improve hemodynamics with the supra-annular configuration and to reduce tissue failure with low-pressure glutaraldehyde preservation of the porcine aortic tissue. The prosthesis was inserted in 1,956 patients with 2,129 prostheses between 1982 and 1989. The mean age of the patient population was 62.7 years (range 13 to 87 years). The mean follow-up was 3.7 years per patient. The freedom from thromboembolism and antithromboembolic therapy-related hemorrhage at 8 years was 92% for aortic valve replacement (AVR), 83% for mitral valve replacement (MVR), and 92% for multiple valve replacement (MR) (p less than 0.05, AVR greater than MR greater than MVR). The freedom from structural valve deterioration was 86% for AVR, 73% for MVR, and 96% for MR at 8 years (p less than 0.05, AVR greater than MR greater than MVR). The freedom from nonstructural valve dysfunction and prosthetic valve endocarditis was not different between positions (p = NS). The freedom from valve-related mortality at 8 years was 98% for AVR, 94% for MVR, and 98% for MR (p less than 0.05, AVR greater than MR greater than MVR). The freedom from residual morbidity was not different at 8 years (p = NS). The freedom from treatment failure (valve-related mortality and residual morbidity) was 96% for AVR, 89% for MVR, and 94% for MR (p less than 0.05, AVR greater than MVR greater than MR).(ABSTRACT TRUNCATED AT 250 WORDS)

Carpentier-Edwards porcine bioprostheses. Comparison of standard and supra-annular prostheses at 7 years

The performance of the Carpentier-Edwards supra-annular (CE-SAV) porcine bioprosthesis is compared with the Carpentier-Edwards standard (CE-S) porcine bioprosthesis at 7 years. The standard prosthesis was implanted in 1,195 patients between 1975 and 1987, while the supra-annular prosthesis was implanted in 1,956 patients between 1982 and 1989. The total follow-up for the standard prosthesis was 8,850 patient-years with a mean follow-up of 7.4 years, while for the supra-annular prosthesis it was 7,317 years with a mean of 3.7 years. The follow-up for the standard prosthesis was 96.7% and for the supra-annular prosthesis was 97.6%. The freedom from structural valve deterioration (SVD) for aortic replacements is 96.1 +/- 0.9% for CE-S and 97.6 +/- 1.4% for CE-SAV at 7 years (p = NS). The freedom for mitral replacements from SVD is 89.1 +/- 1.7% and 88.6 +/- 2.8%, respectively, for CE-S and CE-SAV (p = NS). The freedom for multiple replacements at 7 years was 80.0 +/- 4.5% for CE-S and 97.8 +/- 1.5% for CE-SAV (p less than or equal to 0.05). The freedom from SVD for the age group equal to or less than 35 years is 79.0 +/- 4.7% for CE-S and 85.0 +/- 9.4% for CE-SAV (p = NS). The freedom for the age group 36-50 years is 85.2 +/- 2.8% and 90.4 +/- 4.5%, respectively, at seven years for the CE-S and CE-SAV prostheses (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Age as a determinant for selection of porcine bioprostheses for cardiac valve replacement: experience with Carpentier-Edwards standard bioprosthesis

Almost exclusive use of Carpentier-Edwards porcine bioprostheses for cardiac valve replacement in 1194 patients between 1975 and 1987 at the authors' institutions has afforded the opportunity for a more scientific basis for prosthesis selection for subsets of patients, with regard to age and valve-related complications. The present study, performed according to previously established guidelines, investigated the influence of patient age and valve position as determinants of durability of 1315 porcine implants in terms of the following valve-related complications: structural valve deterioration, nonstructural dysfunction, thromboembolism, antithromboembolic therapy-related hemorrhage and prosthetic valve endocarditis. Age groups were as follows: 35 years and younger, 36 to 50 years, 51 to 65 years, and 66 years or older. Thromboembolism was found to be less common in the younger age groups, and significantly less common in patients following aortic compared to mitral valve replacement. The age group assessment for antithromboembolic therapy-related hemorrhage, nonstructural dysfunction and prosthetic valve endocarditis revealed no difference between positions or age groups. Patient age was found to be the major predictor of, and inversely related to, structural valve deterioration. In addition, porcine bioprostheses in the aortic position were shown to have durability superior to that of similar valves in the mitral position. Structural valve deterioration has very little influence on valve-related mortality and residual morbidity. This study thus supports the implantation of porcine bioprostheses in somewhat younger patients than would be advisable for mitral prostheses. The authors now recommend the selective implantation of porcine bioprostheses in the aortic position in patients over 65 years of age, and in the mitral position in patients over 70 years of age.

Aortic dissection: current expectations and treatment. Experience with 258 patients over 20 years

Aortic dissection, the most common acute disease of the thoracic aorta, is associated with high mortality and morbidity. The authors reviewed their experience over the last 20 years with 258 patients who had aortic dissection (259 dissections). The diagnosis was made at autopsy in 69 (27%) patients (59 type A, 10 type B). Of the remainder, 97 patients had type A dissection (78 acute, 19 chronic) and 93 had type B dissection (56 acute, 37 chronic). The sudden onset of severe, unremitting chest pain associated with hyper- or hypotension or a history of hypertension are suggestive of acute aortic dissection. The diagnosis should be followed by prompt investigation and treatment. The 30-day survival rate for patients with type A dissection who underwent surgical treatment was 62%; survival rates for patients with type B dissection, acute and chronic, were 70% and 86% respectively with pharmacotherapy and 66% and 91% with surgery. The authors stress the importance of early, accurate diagnosis and immediate surgical treatment for all patients who have type A dissection and complicated or unresponsive (carefully monitored pharmacologic control of blood pressure) type B dissection.

Allograft-implant composite reconstruction following periacetabular sarcoma resection

Ten patients with primary periacetabular sarcomas were treated with internal hemipelvectomy and allograft-implant composite reconstruction. Three patients developed local recurrences, one of which was salvaged with repeat resection. One patient underwent hemipelvectomy for infected wound recurrence. At a mean follow-up period of 25 months (range, 7-85 months; median, 18 months), six of nine patients assessed with the Musculoskeletal Tumor Society functional assessment had satisfactory results, with scores of 21 or better (of a possible 35). Although complications were frequent and functional scores were often limited by the muscle resection required for adequate tumor removal, we remain cautiously optimistic about the early results of this procedure.

The Carpentier-Edwards supra-annular porcine bioprosthesis: new generation low pressure glutaraldehyde fixed prosthesis

The Carpentier-Edwards supra-annular porcine bioprosthesis was implanted in 1,576 operations (1,536 patients with 1,704 valves) between 1981 and 1987. The mean age of the patients was 61.9 years (range 13 to 87 years). During the years 1981 and 1987, approximately 90% of the total valvular surgery population received the prosthesis. The early mortality was 7.0% (included patients with concomitant procedures including coronary artery bypass and ascending aortic aneurysm resection). Late mortality was 4.0% per patient-year. The total cumulative follow-up was 4,237 years. Thromboembolism (TE) was 2.4% per patient-year (fatal 0.4% per patient-year) (minor 1.2%; major 1.3%); antithromboembolic therapy-related hemorrhage (ATH) 0.5% (fatal 0.07%); prosthetic valve endocarditis (PVE) 0.5% (fatal 0.2%); periprosthetic leak (PPL) 0.3% (fatal 0%); clinical valve dysfunction (CVD) 0.3% (fatal 0.02%); and structural valve deterioration/primary tissue failure (SVD) 0.2%/patient-year (fatal 0%). Thromboembolism and structural valve deterioration were the significant complications, SVD occurring primarily between the fourth and fifth year of evaluation. The overall patient survival was 77.1% +/- 1.4% at five years. The patients were classified as 89.6% NYHA functional Class III and IV preoperatively and 96.1% Class I and II postoperatively. The freedom at five years from TE was 90.6% +/- 1.0%; SVD 98.9% +/- 0.5%; and reoperation 95.9% +/- 0.9%. Freedom from all valve-related complications at five years was 84.1% +/- 1.3%; valve-related mortality 96.8% +/- 0.7%; mortality and reoperation (valve failure) 92.9% +/- 1.1%; mortality and residual morbidity (treatment failure) 93.7% +/- 0.9%; and mortality, residual morbidity, and reoperation (valve failure and dysfunction) 90.0% +/- 1.2%. There were 28 valve-related deaths of a total 280 deaths (early 4, late 24) (TE 17; ATH 3; CVD 1; PVE 7; PPL 0; and SVD 0). Valve-related reoperations were performed in 32 patients (TE 2; CVD 4; PVE 7; PPL 11; and SVD 8). The supra-annular Carpentier-Edwards porcine bioprosthesis has provided very satisfactory clinical performance and afforded patients an excellent quality of life. The long-term durability of this low pressure glutaraldehyde fixed prosthesis will be determined by observation over the next five to seven years.

The mitral medical pericardial bioprosthesis: new generation bovine pericardial prosthesis

The Mitral Medical Mitroflow pericardial bioprosthesis was implanted in 99 operations (99 patients with 104 valves) between 1984 and 1987. The mean age of the patients was 62.8 years (range 28 to 94 years). The early mortality was 6.1% (including patients with concomitant procedures--coronary artery bypass and ascending aortic aneurysm resection). Late mortality was 2.3% per patient-year. The total cumulative follow-up was 172 years. Thromboembolism (TE) was 4.1% per patient-year (fatal 1.2% per patient-year) (minor 2.3%; major 1.8%); antithromboembolic therapy-related hemorrhage (ATH) 0.6% (fatal 0.6%); prosthetic valve endocarditis (PVE) 0.6% (fatal 0%); periprosthetic leak (PPL) 0.6% (fatal 0%); clinical valve dysfunction (CVD) 1.2% (fatal 0%); and structural valve deterioration/primary tissue failure (SVD) 1.2% per patient-year (fatal 0% per patient-year). Thromboembolism was the significant complication. SVD occurred in two patients during the third year of evaluation. The overall patient survival was 89.2 +/- 3.3% at four years. The patients were classified as 91.9% NYHA functional Class III and IV preoperatively and 97.7% Class I and II postoperatively. The freedom at four years from TE was 88.5% +/- 4.9%; SVD 92.5 +/- 5.1%; and reoperation 89.8% +/- 5.3%. Freedom from all valve-related complications at four years was 76.8% +/- 6.6%; valve-related mortality 97.2 +/- 2.0%; mortality and reoperation (valve failure) 87.3% +/- 5.5%; mortality and residual morbidity (treatment failure) 95.5% +/- 2.6%; and mortality, residual morbidity, and reoperation (valve failure and dysfunction) 85.6% +/- 5.7%. There were three valve-related deaths of a total of ten deaths (early 2; late 1) (TE 2; ATH 1; CVD 0; PVE 0; PPL 0; and SVD 0). Valve-related reoperation was performed in four patients (TE 0; CVD 0; PVE 1; PPL 1; and SVD 2). The Mitral Medical Mitroflow pericardial bioprosthesis has provided very satisfactory clinical performance and afforded patients excellent quality of life.

Carpentier-Edwards porcine bioprostheses: assessment of clinical performance

Carpentier-Edwards porcine bioprostheses have been implanted since 1975, commencing with the previous generation standard prosthesis in that year and the new generation supra-annular prosthesis in 1981. The first 700 operations with each prosthesis were evaluated: Carpentier-Edwards standard porcine bioprosthesis (CE-S), 692 patients (772 valves) and Carpentier-Edwards supra-annular porcine bioprosthesis (CE-SA), 698 patients (756 valves). The incidence of thromboembolism was CE-S 1.4% per patient-year and CE-SA 2.1% per patient-year (hazard interval rates not considered). The rate of structural valve deterioration was CE-S 1.8% per patient-year (79 prostheses) and CE-SA 0.2% (four prostheses). The reoperation rate was 2.5% per patient-year (110 prostheses) for CE-S and for CE-SA it was 0.9% (six prostheses). The late mortality rate was 3.7% per patient-year and 4.2%, respectively. The 10-year freedom rates for CE-S were thromboembolism, 82.7 +/- 2.8%; prosthetic valve endocarditis, 93.5 +/- 1.6%; structural valve deterioration, 77.1 +/- 2.9%; reoperation, 69.9 +/- 3.1%; valve related mortality, 85.9 +/- 2.4%; valve failure, 62.8 +/- 3.2%; treatment failure, 82.0 +/- 2.7%; mortality, reoperation and residual morbidity, 59.5 +/- 3.2%; and all complications, 53.4 +/- 3.1%. The four-year freedom rates for CE-SA were thromboembolism, 93.0 +/- 1.3%; prosthetic valve endocarditis, 98.7 +/- 0.5%; structural valve deterioration, 98.3 +/- 1.0%; reoperation, 95.6 +/- 1.3%; mortality, 97.9 +/- 0.6%; valve failure, 93.6 +/- 1.4%; treatment failure, 94.6 +/- 1.1%; mortality, reoperation and residual morbidity, 90.9 +/- 1.6%; and all complications, 85.6 +/- 1.9%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic dissection. A six year experience with 117 patients

Acute aortic dissection is a medical emergency that demands immediate recognition and early precise angiographic diagnosis. One hundred seventeen patients were found to have aortic dissection between 1980 and 1986. Clinical presentation is of importance since hypertension favors the presence of type B dissection, whereas normotension or hypotension is usually indicative of a type A lesion. Supportive treatment should allow stabilization for diagnosis by angiography or computerized tomography in order to proceed with early surgical repair of all type A dissections. Management of the acute type B patient should initially be medical, but immediate surgical treatment should be carried out if there is failure to control the hypertension, continued pain, expansion or rupture of the aneurysm (including appearance of a pleural collection), development of a neurologic deficit, or evidence of compromise of a major infradiaphragmatic aortic branch. Any delay in surgical treatment once an indicative complication is identified will have an early adverse effect on prognosis. By applying these guidelines, an overall 65 to 75 percent hospital survival rate should be achieved.

Cardiac temperature and cardioplegic volume during cardiopulmonary bypass

This study was designed to compare two methods of cardiac drainage on the rate of change of cardiac temperature and volume of cardioplegic solution required to maintain the cardiac temperature less than or equal to 12 degrees C in patients undergoing coronary artery bypass surgery. Two groups of 10 patients were studied who were comparable in age, sex, and smoking history. In Group 1, cardiac drainage was achieved by using single-port drainage cannulae in the superior and inferior vena cava with caval tapes. Group 2 patients had a caval atrial cannula to drain the noncoronary collateral flow from the right atrium as well as that from the venae cavae. Both groups had a sump line in the left ventricle to drain the bronchopulmonary anastomotic blood flow. Results from the study showed that there was no difference between groups in the initial amount of cold cardioplegic solution required to arrest and cool the heart or the initial recording of ventricular temperatures. However, the volume of cardioplegic solution required to maintain the cardiac temperature at less than or equal to 12 degrees C after administration of the initial volume was less (P less than 0.05) for Group 2 than Group 1. Group 2 also had a slower rate of increase in cardiac temperature than Group 1 (P less than 0.01). Results from this study indicate that the constant removal of blood from both cardiac chambers during coronary artery bypass surgery significantly reduces the rate of myocardial rewarming and decreases the amount of cardioplegic solution required to maintain a given cardiac temperature.

Surgical treatment of lung cancer: promise and problems of early diagnosis

Recent studies have shown that the survival of patients with lung cancer is improved if the tumour is resected before it becomes larger than 3 cm in diameter and before it spreads to lymph nodes. While this suggests a positive benefit from early detection, recent mass-screening studies have claimed that the benefit obtained from this procedure is illusory because it relates to a lead-time bias. This study reports the results of surgical resection of 143 primary lung cancers. The data confirmed that the predicted 5-year survival was greatest (74%) following resection of lesions that were less than 3 cm in diameter without node involvement. Analysis showed that the age of these patients was 63 +/- 8 years, the same as in patients with larger tumours and more extensive node involvement. This suggests that tumours progress rapidly from a stage at which resection is beneficial to stages at which it is not. Although it is desirable that tests predict the presence of small tumours, the high requirements for sensitivity and specificity at current prevalence rates for lung cancer make this goal impractical.

Bronchopulmonary anastomotic and noncoronary collateral blood flow in humans during cardiopulmonary bypass

The sole source of blood returning to the left atrium during cardiopulmonary bypass, while the aorta is cross-clamped, is the bronchopulmonary anastomotic blood flow. In addition, there is noncoronary collateral blood flow which returns to the right atrium. Routinely, the bronchopulmonary anastomotic flow is drained from the left ventricle by a cannula and returned to the main circuitry via a cardiotomy reservoir. The noncoronary collateral flow may be vented similarly by introducing a cannula into the right atrium. Both the anastomotic and the noncoronary collateral flow can be measured with no further surgical intervention. We measured bronchopulmonary anastomotic flow in 40 patients undergoing coronary artery bypass surgery and the noncoronary collateral blood flow in 27 of these patients. Results from this study show that the bronchopulmonary anastomotic flow for the 40 patients was 140 +/- 182 ml/min (range 8 to 1,043 ml/min), representing 3.23 +/- 4.15 percent of the pump flow (equivalent to the cardiac output), and the noncoronary collateral flow in the 27 patients was 48 +/- 74 ml/min (range 0 to 261 ml/min), representing 1.11 +/- 1.67 percent of the pump flow.