Nanosecond laser therapy reverses pathologic and molecular changes in age-related macular degeneration without retinal damage.

Age-related macular degeneration (AMD) is a leading cause of vision loss, characterized by drusen deposits and thickened Bruch's membrane (BM). This study details the capacity of nanosecond laser treatment to reduce drusen and thin BM while maintaining retinal structure. Fifty patients with AMD had a single nanosecond laser treatment session and after 2 yr, change in drusen area was compared with an untreated cohort of patients. The retinal effect of the laser was determined in human and mouse eyes using immunohistochemistry and compared with untreated eyes. In a mouse with thickened BM (ApoEnull), the effect of laser treatment was quantified using electron microscopy and quantitative PCR. In patients with AMD, nanosecond laser treatment reduced drusen load at 2 yr. Retinal structure was not compromised in human and mouse retina after laser treatment, with only a discrete retinal pigment epithelium (RPE) injury, and limited mononuclear cell response observed. BM was thinned in the ApoEnull mouse 3 mo after treatment (ApoEnull treated 683 ± 38 nm, ApoEnull untreated 890 ± 60 nm, C57Bl6J 606 ± 43 nm), with the expression of matrix metalloproteinase-2 and -3 increased (>260%). Nanosecond laser resolved drusen independent of retinal damage and improved BM structure, suggesting this treatment has the potential to reduce AMD progression.

In situ simulation training for paediatric cardiorespiratory arrest: initial observations and identification of latent errors.

In response to a successful, although difficult resuscitation in one of our paediatric wards, we developed and implemented an educational program to improve the resuscitation skills, teamwork and safety climate in our multidisciplinary acute-care paediatric service. The program is ongoing and consists of didactic presentations, high-fidelity in situ simulation and facilitated debriefing to encourage reflective learning. The underlying goal, to provide this training to all staff over a two-year period, should be achieved by late 2011. In this preliminary report we describe teamwork difficulties that are commonly found during such training. These included inconsistent leadership behaviours, inadequate delegation of areas of responsibility, failure to communicate problems during the execution of technical tasks (such as difficulty opening the resuscitation trolley) and failure to challenge inadequate or inappropriate therapy (such as poor chest expansion during bag-mask ventilation). In addition, we unexpectedly discovered seven latent errors in our clinical environment during the first nine months of course delivery. The most disturbing of these was that participants repeatedly struggled to identify and overcome the locking-mechanism and tamper-proof device on a newly introduced resuscitation trolley.

Percutaneous liver biopsy in adult haemophiliacs with hepatitis C virus: safety of outpatient procedure and impact of human immunodeficiency virus coinfection on the spectrum of liver disease.

Both HCV and HIV are common in haemophiliacs previously treated with non-viral-inactivated clotting factor concentrates. Because of increased bleeding risks, little data are available on the safety of percutaneous outpatient liver biopsy (LBx) and impact of HIV coinfection in this population. This study aims at reporting our experience with percutaneous LBx in a cohort of haemophiliacs infected with HCV and describe the spectrum of disease and impact of HIV coinfection. A retrospective review of consecutive patients with haemophilia and HCV who underwent percutaneous LBx was performed. All patients were positive for HCV RNA by commercial assay and received factor concentrate prior to biopsy. A total of 29 male patients (mean age 36, 24 haemophilia A, five haemophilia B, and 44% coinfected with HIV) underwent successful outpatient percutaneous LBx without bleeding complication. Histologic activity index was 6.44 with advanced fibrosis (bridging fibrosis/cirrhosis) in 31%. When patients were stratified by HIV positive (n = 13) vs. HIV negative (n = 16), coinfected patients had higher fibrosis scores and higher proportion advanced fibrosis (54% vs. 12%; P = 0.0167) with no differences in age, demographic or other laboratory parameters. Multivariate logistic regression found that HIV positivity was independently associated with advanced fibrosis (OR = 3.7; 95% CI: 1.17-11.8; P = 0.026). Outpatient percutaneous LBx can be safely performed in patients with haemophilia. Despite similar age, HIV coinfection was an independent predictor of advanced fibrosis. These data support the hypothesis that HIV accelerates fibrosis progression in those coinfected with HCV and highlights the importance of liver histology in this population.

Polymorphisms in cytokines and growth factor genes and their association with acute rejection and recurrence of hepatitis C virus disease in liver transplantation.

Acute rejection (AR) and recurrence of hepatitis C virus (HCV) infection are complications after liver transplantation (LTx). Genetic factors play a role in cytokine production as a consequence of polymorphisms within cytokine genes. Our goal was to identify genetic factors that might be associated with AR and recurrence of HCV in liver transplant recipients (LTxRs). We studied 77 Caucasian LTxRs and 100 Caucasian healthy individuals. We studied single-nucleotide polymorphisms (SNPs) in tumor necrosis factor-alpha[TNF-alpha, interleukin-6 (IL-6), IL-10, transforming growth factor-beta1, and angiotensin-converting enzyme genes by SNaPSHOT trade mark Multiplex assay. SNPs were classified as high producers (HP), intermediate producers (IP), or low producers (LP), and their association with AR and recurrence of HCV were studied. The frequency of TNF-alpha IP and HP genotypes was significantly higher in LTxRs with AR in comparison to patients without AR (TNF-alpha HP -238: 63 vs 20%, p < 0.001; TNF-alpha HP -308: 47.4 vs 20%, p = 0.02). The frequency of IL-6 IP and HP genotypes was higher in patients with AR episodes, but the difference was not statistically significant (p = 0.14). However, when we analyzed the simultaneous presence of pro-inflammatory genotypes in the same patient, we found a significant difference between patients with and without AR, respectively (42.1 vs 14.6%, p = 0.012). Moreover, the frequency of the IL-10 LP genotype was higher in LTx patients with AR (p = 0.001) compared to patients without AR. There was an association between pro-inflammatory genotypes and HCV recurrence. Our data suggest that cytokine gene polymorphisms might play a role in AR and HCV recurrence in LTxRs.

Mutation of a strictly conserved, active-site residue alters substrate specificity and cofactor biogenesis in a copper amine oxidase.

The copper amine oxidases (CAOs) catalyze both the single-turnover modification of a peptidyl tyrosine to form the active-site cofactor 2,4,5-trihydroxyphenylalanine quinone (TPQ) and the oxidative deamination of primary amines using TPQ. The function of a strictly conserved tyrosine located within hydrogen-bonding distance to TPQ has been explored by employing site-directed mutagenesis on the enzyme from H. polymorpha to form the mutants Y305A, Y305C, and Y305F. Both Y305A and Y305C behave similarly with regard to aliphatic amine oxidase activity, showing 3-7-fold decreases in kinetic parameters relative to WT, while the more conservative substitution of Y305F results in a >100-fold decrease in kcat and >500-fold decrease in kcat/Km relative to WT for the reductive half-reaction. The oxidation of benzylamine by all three mutants is severely impaired, with very significant effects seen in the oxidative half-reaction. CAO activity was studied as a function of pH for WT and Y305A proteins. Profiles for WT-catalyzed methylamine oxidation and Y305A-catalyzed ethylamine oxidation are comparable, while profiles of Y305A-catalyzed methylamine oxidation suggest the pH-dependent build-up of an inhibitory intermediate, which was subsequently observed spectrophotometrically and is attributed to the product Schiff base. The relative effects of mutations at Y305 on catalytic turnover are, thus, concluded to be dependent on the nature of the amino acid which substitutes for tyrosine and the substrate used in amine oxidase assays. TPQ biogenesis experiments demonstrate a approximately 800-fold decrease in kobs for apo-Y305A compared to WT. Despite the strict conservation of Tyr305 in all CAOs, neither biogenesis nor catalytic turnover is abolished upon mutation of this residue. We propose an important, but nonessential, role for Tyr305 in the positioning of the TPQ precursor for biogenesis, and in the maintenance of the correct conformation for TPQ-derived intermediates during catalytic turnover.

Risk factors for cerebral injury and cardiac surgery.

Cerebral complications represent the leading cause of morbidity after cardiac operations. With the growing awareness of their social and economic importance, increasing attention is being given to their prevention. In the coronary artery bypass population, advanced age (> or = 75 years) is associated with an 8.9% neurologic deficit rate. Mortality is increased ninefold in the elderly patient with a neurologic deficit. Cardiopulmonary bypass has long been recognized as a cause of neuropsychologic deficits. Emboli are thought to be the causal agent. Retinal microvascular lesions during cardiopulmonary bypass as well as recent demonstration of widespread pathologic subcapillary arteriolar dilatations in the brain after cardiopulmonary bypass have been documented. Despite widespread interest in cerebral blood flow and neurologic deficits, there is no convincing evidence that defines a critically low or dangerously high level of flow. The ascending aorta represents a leading source of embolic neurologic injury. The use of intraoperative ultrasound to identify the diseased aorta may result in alternative operative strategies in an effort to minimize emboli and improve neurologic outcome. Existing literature offers conflicting views on optimal management of carotid artery stenosis in the coronary artery surgical patient. A trend that combined carotid endarterectomy and coronary artery bypass may often be appropriate will need confirmation through a multicenter clinical trial. Open cardiac surgical procedures, particularly in the aged population, carry a significant increased risk of adverse neurologic outcome. Postoperative arrhythmias may result in embolic neurologic deficit. A further understanding of risk factors for cerebral injury will be of value in developing therapeutic approaches to this major clinical problem.

Predictive value of blood clotting tests in cardiac surgical patients.

This study prospectively evaluated numerous tests of clotting function in 897 consecutive adult cardiac surgical patients over 18 months. This included coronary operation, valve replacement, and reoperative patients. The tests included activated clotting time, activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen, fibrin/fibrinogen degradation products, platelet count, and Duke's earlobe bleeding time. Other variables such as age, sex, and cardiopulmonary bypass duration were included in the multivariate analysis. Statistically significant correlations were found between 16-hour mediastinal drainage and activated partial thromboplastin time, fibrinogen, activated clotting time, fibrin/fibrinogen degradation products, platelet count, and prothrombin time. Scatter plots indicate that these relationships, although statistically significant, had little predictive value and were largely significant as a result of the large number of patients in each group, which permitted weak correlations to reach statistical significance. The best multivariate model constructed could explain only 12% of the observed variation in postoperative blood loss. Because the predictive values of the tests are so low, it does not appear sensible to screen patients routinely using these clotting tests shortly after cardiopulmonary bypass.

Surrogate tissues for detecting brain microemboli after cardiopulmonary bypass.

During cardiopulmonary bypass (CPB) microemboli lodge in the brain and other organs. Microemboli were counted in tissue samples of skin, muscle and brain from autopsy cases that had recently undergone CPB, and in skin and muscle biopsies obtained from patients before and after CPB. Unlike the brain, skin and muscle showed few microemboli.

Cerebral injury and cardiac operations.

Cerebral complications constitute the leading source of morbidity and disability after cardiac operations. The incidence of stroke after coronary artery bypass grafting has increased in tandem with the mean age of the patient population. Although many cerebral deficits resolve with time, others remain sources of disability for otherwise functional patients and detract from an otherwise successful procedure. The clinical spectrum of cerebral complications includes both neurologic and neuropsychologic deficits. Neurologic deficits include fatal cerebral injury, stroke, impaired level of consciousness, and seizures. The incidence of these deficits is 1% to 6%. Neuropsychologic deficits refer to cognitive changes, and are quantitated with tests of memory and learning and speed of visual-motor response. The incidence of these deficits is 60% to 80% at 1 week after operation and 20% to 40% at 8 weeks after operation. Central nervous system complications after cardiac operations have been attributed in large part to the effects of cardiopulmonary bypass on the brain. Potential mechanisms include macroembolization of air or particulate matter; microembolization of gas, fat, aggregates of blood cells, platelets or fibrin, and particles of silicone or polyvinylchloride tubing; and inadequate cerebral perfusion pressure. Methods of assessment include those applied during the procedure (clinical observation, assessment of cerebral blood flow and metabolism, intraoperative electroencephalography, transcranial and carotid Doppler echography, quantitative embolic measurement, and fluorescein angiography) and those performed to measure outcome (neurologic and neuropsychologic testing, computed tomographic scans, magnetic resonance imaging, and cerebrospinal fluid studies). Much of the literature regarding cerebral injury and cardiopulmonary bypass is descriptive, relating patient risk factors to the incidence of postoperative stroke.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitral valve operation via an extended transseptal approach.

The extended transseptal approach to the mitral valve has been used for 71 consecutive procedures. Four patients died; none had complications directly attributable to the exposure. Twenty underwent a primary reparative procedure; 30, a primary replacement procedure; and 21, a repeat procedure. Despite division of the sinus node artery, 26 of 32 patients with sinus rhythm preoperatively had sinus rhythm postoperatively; 4 had atrial fibrillation postoperatively. Twenty-seven of 37 patients with atrial fibrillation preoperatively had atrial fibrillation postoperatively; 8 had sinus rhythm postoperatively. Because the exposure provided by this extended transseptal approach is superior to that of standard approaches, we now use it routinely for mitral valve operations.

Sodium nitroprusside infusion does not dilate cerebral resistance vessels during hypothermic cardiopulmonary bypass.

This study determined whether sodium nitroprusside (SNP) changes cerebral vascular resistance during stable, hypothermic cardiopulmonary bypass (CPB). Cerebral blood flow (CBF) was measured using Xenon clearance in 39 patients anesthetized with fentanyl. In 25 patients (group 1), CBF was measured before and during infusion of SNP at a rate sufficient to reduce mean arterial pressure (MAP) approximately 20%. In 14 other patients (group 2), CBF was measured before and during simultaneous infusion of SNP and phenylephrine; SNP was continued at a rate that had reduced MAP approximately 20% while phenylephrine was added in a dose sufficient to restore MAP to preinfusion levels. Patients within each group were randomized to maintenance of PaCO2 approximately 40 mmHg (groups 1a and 2a), uncorrected for body temperature, or to maintenance of PaCO2 approximately 50 mmHg (groups 1b and 2b). The following variables were maintained within a narrow range: nasopharyngeal temperature (26-29 degrees C), pump oxygenator flow (1.7-2.5 l.min-1.m-2), PaO2 (150-300 mmHg), and Hct (22-28 vol%). In each patient, controlled variables varied no more than +/- 5% between measurements. In group 1a (PaCO2 approximately 40 mmHg), MAP was 86 +/- 9 mmHg (mean +/- SD) before and 65 +/- 8 mmHg during SNP infusion (P less than 0.0001). CBF was 12 +/- 3 ml.100g-1.min-1 before and 10 +/- 2 ml.100(-1).min-1 during SNP infusion (P less than 0.01). In group 1b (PaCO2 approximately 55 mmHg), MAP was 86 +/- 11 mmHg before and 66 +/- 13 mmHg during SNP infusion (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Improved lung preservation with cold air storage.

Conventional topical slush cooling limits lung transport to 4 to 6 hours. For this canine study of an alternate air cooling system, 37 canine lungs were removed: 24 were placed in plastic bags, and inserted in a Transplanthermm container at core air temperatures (n = 6 lungs each) of (A) 4 degrees C, (B) 8 degrees C, (C) 12 degrees C, and (D) 20 degrees C; 6 were stored conventionally in ice slush (E); and 7 were transplanted immediately (F). After 8 hours, the stored lungs were transplanted and the contralateral pulmonary artery was ligated. Survival, arterial oxygen tension, and extravascular lung water were monitored at 15 minutes and every hour for 4 hours. Four-hour survival was 100% in groups A, B, and F; 83% in group C, 50% in group D, and 17% in group E. The mean arterial oxygen tension at 1 hour was lower in group E (6.4 +/- 2.4 kPa) than in group A (39.8 +/- 13.2 kPa) (p = 0.0002) or in group F (42.0 +/- 16.2 kPa) (p = 0.0035). Extravascular lung water in group E was higher at 15 minutes (15.44 +/- 5.63 mL/kg) than in group A (3.76 +/- 0.63 mL/kg) (p = 0.0001) and group F (4.69 +/- 1.65 mL/kg) (p = 0.003). Cold air storage appears to provide better lung preservation than hypothermic immersion in ice slush.

Effect of desmopressin on vein graft patency in a microvascular model.

Desmopressin acetate decreases blood loss after cardiac surgery by activating platelets. We studied whether this effect was detrimental to small-caliber vein grafts in rats. Thirty minutes before femoral artery grafting with 0.75-mm-diameter reverse autogenous saphenous vein grafts, 20 rats received desmopressin acetate intravenously at 1.0 micrograms/kg over 10 minutes, and 20 control rats received normal saline intravenously over 10 minutes. In each group, 10 rats received a 6-mm-long graft and 10 an 18-mm-long graft. Graft patency was evaluated at 20 minutes, 24 hours, and 30 days. Intimal thickening was assessed by light and scanning electron microscopy. At 30 days, 9 short grafts and 8 long grafts in the desmopressin-treated group were patent, whereas only 8 short control grafts and only 6 long control grafts were patent. Intimal thickening and platelet deposition were the same in both groups. These data show no detrimental effects of desmopressin acetate on saphenous vein graft patency.

Neuropsychiatric complications following cardiac surgery.

Few patients are neurologically devastated following cardiac surgery. However, a substantial number of patients suffer sufficient deterioration in neurologic and neuropsychologic function that the quality of their recovery is limited. Intensive research is necessary to determine what surgical and pharmacologic techniques are suitable for use in this large at-risk population.

Hypercarbia depresses cerebral oxygen consumption during cardiopulmonary bypass.

No human studies have systematically examined the relations among PaCO2, cerebral blood flow, and the cerebral metabolic rate for oxygen during hypothermic cardiopulmonary bypass. We varied PaCO2 during hypothermic (26-28 degrees C) cardiopulmonary bypass and estimated the cerebral metabolic rate for oxygen by multiplying cerebral blood flow (measured using xenon-133 clearance) by the cerebral arteriovenous difference in oxygen contents. Patients were randomly assigned to either of two methods of managing PaCO2 (uncorrected for body temperature). In group 1 (PACO2 32-48 mm Hg, n = 13) the mean +/- SD cerebral metabolic rate for oxygen was 0.40 +/- 0.11 ml O2 X 100 g-1 X min-1 at a mean +/- SD PaCO2 of 36 +/- 2.0 mm Hg and 0.40 +/- 0.14 ml O2 X 100 g-1 X min-1 at a mean +/- SD PaCO2 of 45 +/- 2 mm Hg. and 49-72 mm Hg, n = 12) the mean +/- SD cerebral metabolic rate for oxygen was 0.31 +/- 0.09 ml O2 X 100 g-1 X min-1 at a mean +/- SD PaCO2 of 55 +/- 3 mm Hg and 0.21 +/- 0.07 ml O2 X 100 g-1 X min-1 at a mean +/- SD PaCO2 of 68 +/- 2 mm Hg. Group 2 values differed significantly from those in Group 1 (p less than 0.05). In both groups, cerebral blood flow increased as PaCO2 increased. During cardiopulmonary bypass, increasing PaCO2 increases cerebral blood flow and decreases the cerebral metabolic rate for oxygen.

Labetalol for the control of elevated blood pressure following coronary artery bypass grafting.

In a multicenter study, the efficacy and safety of intravenous (IV) labetalol for the control of elevated blood pressure were studied in the intensive care unit (ICU) in 65 patients within 4 hours following coronary artery bypass grafting (CABG). Patients with pre-existing ventricular dysfunction, bradycardia, bronchospastic disease, or postoperative complications were excluded. All patients were monitored with a thermodilution pulmonary artery catheter. Entry criteria were a systolic blood pressure (SBP) greater than 140 mm Hg or diastolic blood pressure (DBP) greater than 90 mm Hg for at least five minutes. Intravenous labetalol was loaded incrementally (5, 10, 20, and 40 mg at 10-minute intervals) to a maximum cumulative dose of 75 mg, until either SBP decreased 10% or DBP decreased 10% and was less than 90 mm Hg. Responders were entered into a 6-hour maintenance period, and received 5 to 40 mg of IV labetalol every 10 minutes as needed for blood pressure control. Hemodynamic data and temperature were recorded at baseline, just before each dose of labetalol during the loading period, and at the end of the maintenance period. Alternative therapy was given in the case of nonresponse or adverse events. Intravenous labetalol successfully controlled post-CABG hypertension in 55 of 65 patients (85%); of these, 46 responded to 35 mg or less. Although 28 patients required no further labetalol in the maintenance period, in the others dosage varied from 5 to 400 mg. Reductions in SBP and DBP were associated with moderate reductions in pulse pressure (SBP-DBP) and heart rate (HR). Cardiac index decreased by 18.5%, with a 12.5% decrease in stroke index and 8.1% decrease in HR. Systemic vascular resistance did not increase significantly. Four patients (6%) developed hypotension related to IV labetalol. There was one death due to perioperative myocardial infarction, which was unrelated to labetalol use. The mechanism of action of IV labetalol in controlling hypertension after CABG surgery seems to be moderate negative inotropy and chronotropy. Its alpha-blocking effects seem to be important in preventing reflex vasoconstriction. This is directly opposite to the primary vasodilator effect found when IV labetalol is used to control nonsurgical hypertension. Because of these actions, labetalol should be avoided or used with caution in patients with preoperative and postoperative cardiac dysfunction. In patients with normal left ventricular function, IV labetalol appears to be a safe, effective agent in controlling post-CABG hypertension, with the added potential benefit of enhanced myocardial oxygen balance.

Heparin dosing and monitoring for cardiopulmonary bypass. A comparison of techniques with measurement of subclinical plasma coagulation.

Subclinical plasma coagulation during cardiopulmonary bypass has been associated with marked platelet and clotting factor consumption in monkeys. To better define subclinical coagulation in man, we measured plasma fibrinopeptide A concentrations before, during, and after cardiopulmonary bypass. Patients were assigned to one of three groups of heparin management: group 1 (n = 10)--initial heparin dose 300 IU/kg, with supplemental heparin if the activated coagulation time fell below 400 seconds; group 2 (n = 6)--initial heparin dose 250 IU/kg, with supplemental heparin if activated coagulation time was less than 400 seconds; and group 3 (n = 5)--initial heparin dose 350 to 400 IU/kg, with supplemental heparin if whole blood heparin concentration was less than or equal to 4.1 IU/ml. Activated coagulation time and heparin concentration were measured every 30 minutes during cardiopulmonary bypass, and fibrinopeptide A was measured at hypothermia, normothermia, and whenever activated coagulation time was less than 400 seconds. Quantitative and qualitative blood clotting competence was assessed after cardiopulmonary bypass, including mediastinal drainage for the first 24 hours. Fibrinopeptide A values were markedly elevated during cardiopulmonary bypass but were well below the levels present before and after cardiopulmonary bypass. Fibrinopeptide A correlated inversely with heparin concentration during cardiopulmonary bypass (r = -0.46, p = 0.03), but higher fibrinopeptide A levels during cardiopulmonary bypass did not correlate with post-cardiopulmonary bypass coagulopathy. Group 3 patients received the highest heparin doses (p less than 0.05) and had the greatest postoperative blood loss (p less than 0.05). Protamine dose and heparin concentration during cardiopulmonary bypass correlated best with postoperative mediastinal drainage. Our findings support the following conclusions: (1) compensated subclinical plasma coagulation activity occurs during cardiopulmonary bypass despite activated coagulation time greater than 400 seconds or heparin concentration greater than or equal to 4.1 IU/ml; (2) post-cardiopulmonary bypass mediastinal drainage correlates strongly with increased heparin concentration during cardiopulmonary bypass (p less than 0.05) and protamine dose (p less than 0.05); and (3) during cardiopulmonary bypass at both normothermia and hypothermia, activated coagulation times greater than 350 seconds result in acceptable fibrinopeptide A levels and post-cardiopulmonary bypass blood clotting.