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Biomedical subjects

J L Knight

Publications and source records attributed to J L Knight.

At least 19 recordsLinked to original sources
PubMed2002

Systematic review of beating heart surgery with the Octopus Tissue Stabilizer.

The safety and efficacy of off-pump coronary artery bypass surgery with the aid of the Octopus Tissue Stabilizer (Octopus OPCAB), in comparison to conventional on-pump coronary artery bypass surgery (CPB-CABG), was examined by a systematic assessment of the peer-reviewed literature. The limited comparative data suggested that there was no difference in safety outcomes between Octopus OPCAB and CPB-CABG. The paucity of efficacy data reported in the higher level comparative studies meant that it was impossible to assess whether Octopus OPCAB was more efficacious than CPB-CABG. The evidence base for the procedure was deemed inadequate and an audit of the procedure was recommended.

Cardiopulmonary Bypass↗
PubMed2001

Preoperative depression and mortality in coronary artery bypass surgery: preliminary findings.

BACKGROUND: There is convincing evidence to suggest that depression significantly increases the risk of mortality following myocardial infarction. There are few data concerning depression as a risk factor for mortality following cardiac surgery. The aim of the present observational study was to determine if preoperative depressive symptoms resulted in an increased risk of late mortality following cardiac surgery. METHODS: Preoperative assessments of depressive symptoms were performed on 158 patients undergoing coronary artery bypass surgery. Elevated preoperative depression symptoms were defined as a depression anxiety stress scale score of > or = 10. RESULTS: Twenty-four of the 158 patients ( 15.2%) were classified as having elevated preoperative depressive symptoms. Patients were followed for a median of 25 months (range: 4-38 months). Three of the 24 patients (12.5%) with preoperative depressive symptoms died within the follow-up period, compared with three of the 134 (2.2%) non-depressed patients (odds ratio: 6.24; 95% CI: 1.18-32.98; P = 0.046). There were no other group differences on variables including population demographics, medical risk factors, surgical parameters, and indices of postoperative morbidity. CONCLUSIONS: Elevated depressive symptoms before coronary bypass surgery may be a significant predictor of late death. Prospective studies evaluating the prevalence of depressive symptoms in cardiac surgical patients and their effect on long-term outcome must be undertaken.

Analysis of Variance↗
PubMed2001

Coronary artery baroreceptor-mediated changes in arterial pressure: a pilot study in conscious and anaesthetized sheep.

1. Evidence suggesting the presence of coronary artery baroreceptors on coronary arteries has existed for over 30 years. 2. Evidence that activation of ventricular mechanoreceptors can elicit cardiovascular changes has been challenged, with those changes now thought to be due to coronary artery mechanoreceptors. 3. Studies have suggested that coronary artery mechanoreceptors act as coronary baroreceptors with a role in cardiovascular regulation. However, all evidence to date has been obtained in anaesthetized animal models in physiologically compromised intra-operative states. 4. The purpose of the present study was to design an ovine model that would allow the discrete stretch of coronary arteries without causing ischaemia or changing flow or intra-arterial pressure and that would confirm results seen in previous studies. In addition, the possibility that the technique could be used for studies of coronary artery baroreflexes in conscious sheep was investigated. 5. Controlled stretch of the proximal left anterior descending coronary artery elicited decreases in arterial pressure without changes in heart rate or electrocardiographic activity in halothane-anaesthetized sheep. Similar results were demonstrated in conscious sheep after surgical recovery of up to 2 weeks. 6. The present study supports the possibility that coronary artery baroreceptors exist and likely have a role in cardiovascular regulation. The results of the present study in anaesthetized sheep are in agreement with previous results in anaesthetized animals, but also provide the first demonstration of coronary baroreceptor activity in a conscious animal model, underscoring the potential use of the model in the study of coronary artery baroreceptors in the intact animal.

Anesthesia↗
PubMed2001

A comparison of neuropsychologic deficits after extracardiac and intracaradiac surgery.

OBJECTIVE: To compare the incidence of neuropsychologic deficits 1 week and 6 months after coronary artery bypass graft (CABG) surgery (extracardiac) and valve surgery with or without CABG surgery (intracardiac) using reliable change indices to define the incidence of neuropsychologic deficits. DESIGN: Prospective study. SETTING: Cardiac surgical unit in a university teaching hospital. PARTICIPANTS: Patients scheduled for elective multiple-graft (> or =3 grafts) CABG surgery (n = 59), or elective valve surgery (with or without concomitant CABG surgery) (n = 50) and a matched sample of nonsurgical controls (n = 53). INTERVENTIONS: Neuropsychologic assessments were performed 1 day before surgery, 7 days and 6 months after surgery. MEASUREMENTS AND MAIN RESULTS: The 7-day assessment showed no significant differences between valve surgery patients and CABG surgery patients in the incidence of neuropsychologic deficits. When reassessed 6 months postoperatively, the valve group displayed a significantly higher incidence of deficits on the digit symbol test compared with the CABG group (valve 26.7% v CABG 6.8%). In the CABG group, there was a significant change in the incidence of deficits per patient from 7 days to 6 months (p = 0.03) that was not evident in the valve group. CONCLUSION: There are some differences in the neuropsychologic outcome of extracardiac and intracardiac surgery. Patients undergoing isolated CABG surgery showed a greater reduction in the incidence of persisting deficits at 6 months than patients undergoing valve surgery with or without CABG surgery. This finding warrants further investigation, with particular attention to patients undergoing combined valve and coronary artery procedures.

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PubMed2001

Evaluation of neurologic assessment and outcomes in cardiac surgical patients.

It is well recognized that cardiac surgery with cardiopulmonary bypass can potentially induce a wide spectrum of central nervous system (CNS) sequelae. Our awareness of the prevalence of these CNS complications is dependent on the validity of the available diagnostic methods. Current assessment methods designed to detect both focal and diffuse cerebral ischemia include neurologic examination, imaging techniques, biochemical markers, neuropsychologic assessment, and patient perceived outcomes. These techniques vary in their sensitivity and specificity, as well as feasibility for use in everyday clinical practice. There are currently only limited standardized methodologic guidelines for the assessment of CNS complications after cardiac surgery, which has resulted in considerable interstudy variability in the identification and reporting of outcomes. The application of clearly definable endpoints for reporting of CNS outcomes would be beneficial. The wealth of available data suggests that the incidence of overt CNS injury such as stroke has declined since the 1980s and is now approximately 2%, whereas evidence suggests that up to one third of cardiac surgery patients experience postoperative cognitive deficits. One of the clear strengths of the current era is the recognition of CNS injury associated with cardiac surgery, and the quest to improve our understanding of these outcomes. The application of more uniform assessment and reporting practices is surely vital to the continued advancement of cardiac surgery.

Biomarkers↗
PubMed2001

The Octopus II stabilizing system: biochemical and neuropsychological outcomes in coronary artery bypass surgery.

INTRODUCTION: The aim of this study was to determine if coronary artery bypass graft (CABG) surgery performed utilizing the Octopus II stabilizing system provides myocardial and cerebral protection comparable to traditional CABG surgery utilizing cardiopulmonary bypass (CPB). METHODS: Elective patients requiring surgery for double or triple vessel disease were randomized to receive either conventional CABG with CPB (n = 14) or OPCAB using the Octopus II stabilizing system (n = 12), after receiving institutional approval and written consent. Exclusion criteria included previous cardiac surgery, recent myocardial infarction, and previous cerebrovascular disease. Troponin T (TnT) was measured preoperatively and at 2, 4, 6, 8, 10, 12, 24, and 72 hours after initiation of grafting. Neuropsychological assessments (10 measures) were performed in the week prior to surgery, one week, and six months after surgery. RESULTS: Troponin T release was reduced in the OPCAB patients at all time points (repeated measures ANOVA p = 0.043), reaching significance at 8, 10 and 12 hours (p = 0.033, 0.038, 0.019). Other factors (composite clinical end point (prolonged LOS or ICU stay or 30-day mortality), infarction, and intubation time) did not show any significant differences between the two groups. The incidence of neuropsychological deficits was not different between the two groups at both seven-day and six-month follow-up assessments. CONCLUSIONS: Decreased TnT release suggests a myocardial benefit for the OPCAB procedure. A neuropsychological benefit remains to be demonstrated.

Aged↗
PubMed2000

Mood state as a predictor of neuropsychological deficits following cardiac surgery.

OBJECTIVES: mood disorders and neuropsychological deficits are both commonly reported occurrences after cardiac surgery. We examined the relationship between mood state and postoperative cognitive deficits in this population. METHODS: assessments of neuropsychological functions and mood state (depression, anxiety, stress scales; DASS) were performed preoperatively and postoperatively on 147 patients undergoing cardiac surgery. RESULTS: the incidence of preoperative depression, anxiety, and stress symptomatology was 16%, 27%, and 16%, respectively. The incidence of postoperative anxiety symptomatology significantly increased to 45% (p<0.001), while the incidence of depression and stress symptomatology remained stable (19% and 15%, respectively; ns). Changes in mood state did not influence changes in neuropsychological performance. Preoperative mood was a strong predictor of postoperative mood, and was related to postoperative deficits on measures of attention and memory. CONCLUSIONS: an assessment of preoperative mood is critical in identifying patients at risk of postoperative mood disorders and neuropsychological deficits. Measures assessing somatic manifestations of anxiety may not be suitable for a surgical population.

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PubMed2000

Collarless polished tapered impaction grafting of the femur during revision total hip arthroplasty: pitfalls of the surgical technique and follow-up in 31 cases.

Impacting morcellized allograft bone into the femur during revision total hip arthroplasty is a simple concept with the goal of rebuilding femoral bone stock and providing secure fixation to the femoral stem. Using the collarless polished tapered (CPT, Zimmer, Warsaw, IN) stem impaction grafting system, we became concerned about the discrepancy between the straightforward concept and precise execution of the technique. In this study, we examined 31 consecutive procedures to determine intraoperative difficulties and report on the clinical outcome of 30 cases at an average follow-up of 31 months. Modified Harris Hip Scores averaged 41 points preoperatively and improved to 86 points at follow-up. Nineteen cases were performed on intact femora, whereas 12 cases had disrupted femoral integrity, either extended trochanteric osteotomy or periprosthetic fracture. Successful outcome was seen in all cases with an intact femur, and restoration of femoral integrity was key to successful outcome in cases with compromised femoral integrity. Among cases with disrupted femoral integrity, 3 distal fractures occurred as a result of the rigid CPT cement plug, and 2 complete femoral fractures occurred as a result of bone impaction, for a technique-related fracture rate of 16%. Difficulty packing bone distally occurred in 94% of cases and was associated with varus and valgus stem alignment and medial and lateral stem displacement. Complete cement mantles were seen in 77% of cases. No stem subsidence was seen in 15 of 30 cases (50%). Stem subsidence of <5 mm was seen in 10 of 30, stem subsidence of 6 to 8 mm was seen in 4 of 30, and stem subsidence of >10 mm was seen in 1 patient (4%). Of the patients, 87% thought the procedure improved their function, and 97% would recommend it to a friend with a failed femoral component. Although we hope that the instruments for this procedure can improve, we endorse the concept of impaction grafting with the CPT stem as a successful way of dealing with revision femoral surgery.

Aged↗
PubMed1999

Posterior distal cement extrusion during primary total hip arthroplasty: a cause for concern?

Manually operated injection systems are routinely used to deliver polymethyl methacrylate during cemented femoral component primary total hip arthroplasty (THA). The goal of cement delivery is to achieve sufficient intrusion of cement into the trabecular bone of the prepared femur so that the femoral component is securely bonded to the femur. We have observed posterior distal cement extrusion (PDCE), which appears to be secondary to too-successful pressurization. We sought to quantify and offer a possible explanation for this phenomenon. Eight patients with PDCE were identified, with an estimated incidence range of 0.90%, to 1.6% of primary cemented femoral component THA. All occurred in female patients of small stature. Endosteal canal diameters were also small, averaging 11 mm, 10 cm from the lesser trochanter. The PDCE occurred at an average distance of 9.8 cm from the midpoint of the lesser trochanter, and was most easily visualized on the lateral radiograph where it resided in the posterior soft tissues. Examination of 49 human femora showed 1 or more vascular channels in the posterior aspect of the femur in all specimens. The most proximal vascular channel averaged 10.1 cm distal to the lesser trochanter and had an average lumen diameter of 1 mm. The vascular channel contained an artery and 2 veins by histologic examination. We postulate that PDCE represents the escape of low-viscosity cement out of the vascular channel, and laboratory simulation supports this possibility. Because this finding has not previously been reported, we hoped that other centers will look closely for this phenomenon.

Aged↗
PubMed1999

Mechanical circulatory support devices in the treatment of heart failure.

With an increasingly aging population, heart failure is a major health issue, affecting more than 10% of the population over 65 years of age, and costing hundreds of millions of dollars per year for ongoing care. Even with maximal medical therapy, annual mortality rates of in excess of 25% are commonly reported. Over the last three decades, various surgical approaches have been examined in the hope of improving the outcome of congestive cardiac failure. These procedures range from simple coronary revascularisation to left ventricular reduction surgery and cardiac transplantation. Although of value in selected situations, no surgical approach, beyond transplantation, has had significant impact on the outcome of heart failure. In the last decade, development in the area of mechanical support for the failing heart has continued to expand at a rapid rate. Strong evidence now exists to show that in many patients with advanced heart failure, prolonged mechanical support results in significant myocardial recovery. There are currently several mechanical support devices available for clinical use, although most are considered experimental in this country. These devices are expensive and are not without significant complications, but early results of their use as either a bridge to transplantation or as a stand alone treatment, have been very encouraging. Currently available mechanical assist devices are described, with discussion of indications for implantation, complications and results of their use.

Australia↗
PubMed1998

Neuropsychologic changes after coronary artery bypass grafting: use of reliable change indices.

BACKGROUND: A method of defining change in neuropsychologic test scores that accounts for test reliability and practice effects was applied to determine accurately the incidence of acquired neuropsychologic deficits after coronary artery bypass grafting. METHODS: Neuropsychologic assessment was performed on 50 patients before and at 7 days after either hypothermic or normothermic coronary artery bypass grafting. From a matched control group of 24 normal subjects who were examined twice over a similar interval, reliable change indices that controlled for measurement error and practice effects were calculated for each neuropsychologic measure. With the use of these indices, the incidence of postoperative decline among the study patients was determined. For comparison, the incidence of decline using the "one standard deviation" criterion also was calculated. RESULTS: Comparing the reliable change and standard deviation methods, statistically significant differences in the incidence of decline were observed in 5 of 11 neuropsychologic measures. The reliable change method identified more patients with neuropsychologic deficits on most measures. CONCLUSIONS: The control of measurement error and practice effects can alter significantly the calculated incidence of neuropsychologic impairment after coronary artery bypass grafting.

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PubMed1998

Neuropsychological dysfunction after minimally invasive direct coronary artery bypass grafting.

BACKGROUND: We compared postoperative neuropsychological dysfunction after minimally invasive direct coronary artery bypass grafting (MIDCAB) operation with coronary artery bypass graft operations using cardiopulmonary bypass. METHODS: Neuropsychological assessment was performed preoperatively and before discharge on 7 patients undergoing MIDCAB procedures, 9 patients undergoing single-graft cardiopulmonary bypass operation, and 27 patients undergoing multiple-graft cardiopulmonary bypass operation. From a matched control group of 40 normal subjects reliable change indices were derived for each measure and used to determine the incidence of postoperative decline. RESULTS: There was little difference between the MIDCAB and single-graft cardiopulmonary bypass groups on the incidence of neuropsychologic decline. However, the multiple-graft cardiopulmonary bypass group had a significantly higher incidence of decline than the MIDCAB and single-graft cardiopulmonary bypass groups on specific neuropsychologic measures, coupled with a significantly greater number of postoperative deteriorations per patient. CONCLUSIONS: The elimination of cardiopulmonary bypass does not prevent neuropsychological dysfunction after cardiac operation as patients undergoing MIDCAB and single-graft cardiopulmonary bypass experience similar deteriorations in performance. However, the deterioration is markedly worsened when the number of surgical grafts is increased.

Aged↗
PubMed1998

Clinical results of the midstem porous-coated anatomic uncemented femoral stem in primary total hip arthroplasty: a five- to nine-year prospective study.

The clinical and radiologic results of an inclusive series of 60 patients (70 hips) who had primary total hip arthroplasty using the porous-coated anatomic (PCA) midstem femoral prosthesis was prospectively studied. The midstem component features a proximal circumferential porous bead coating similar to the PCA primary stem; but increased proximal thickness, increased length, and a distal anterior curve for additional rotational stability. The mean Harris Hip Score rose from 39.5 points before surgery to 91.3 points at a minimum follow-up of 5 years (average, 69 months); 88% were good or excellent. Moderate or severe thigh pain on a visual analogue scale was reported by 30% of cases, and was more common in women. Radiographic analysis indicated preservation of proximal bone stock and bony ingrowth in 87%, but stem subsidence in 9%. One stem has been revised for subsidence and thigh pain (1.4%), and one stem is radiographically loose, but the patient refuses surgical revision. Endosteal osteolysis was rarely seen (2.8%) and was benign in appearance. Acetabular components used included 63 nonmodular PCA metal-backed cups and 7 hemispherical porous ingrowth cups fixed with screws. One PCA cup was revised for loosening (1.4%), and one is radiographically loose but stable (1.4%). Only one cup exhibited an area of osteolysis. At this intermediate follow-up the clinical outcome of the midstem component is stable and excellent. The radiographic results appear superior to the PCA primary stem, with a lower incidence of stem subsidence and osteolysis. The prevalence of thigh pain is a concern and we recommend regular follow-up of patients with the midstem femoral implant, and the use of a visual analogue thigh pain scale when any femoral prosthesis is evaluated.

Arthroplasty, Replacement, Hip↗
PubMed1998

Blood transfusion strategies for total knee arthroplasty: minimizing autologous blood wastage, risk of homologous blood transfusion, and transfusion cost.

In this nonrandomized study, alternative strategies were suggested to 10 orthopaedic surgeons to minimize autologous blood wastage, the risk of homologous blood transfusion, and cost associated with blood product usage after total knee arthroplasty (TKA). One hundred fifty-five patients with 177 consecutive TKAs over a 2-year period were studied. Group 1 patients had undergone unilateral TKA and did not predonate; 1A patients (n = 19) were drained with a Hemovac, and 1B patients (n = 28) with a postoperative blood recovery system. Group 2 patients (n = 47) predonated one packed red blood cell (pRBC) unit. Group 3 patients (n = 20) predonated 2 pRBC units. Group 4 patients had undergone bilateral sequential TKAs (n = 21) and had predonated 2 pRBC units. Group 5 patients (n = 14) had undergone revision TKA procedures and their blood requirements were individualized. Group 6 patients (n = 6) had preexisting anemia and were excluded from the study. There was no significant difference in total blood loss (909 mL) between groups. Female sex was associated with significantly lower admission hematocrit. Homologous blood was required for 4% of patients in the entire study and the percentage was not statistically different between groups. Twenty-five percent of patients who predonated autologous pRBCs did not use all or some of it. In group 1, the postoperative blood recovery system had a significant effect on reducing postoperative hematocrit drop (P = .0001), but it was not a significant factor if autologous pRBCs were available. The costs associated with group 1A were significantly less (P = .0001) compared with the other groups; group 1A had the highest admission hematocrit (43.2). Transfusion with autologous pRBCs was related to lower admission hematocrit rather than to increased postoperative blood loss. An algorithm is presented to provide cost-effective management of blood products after TKA.

Aged↗
PubMed1998

A computational quantitative structure-activity relationship study of carbamate anticonvulsants using quantum pharmacological methods.

A pattern recognition quantitative structure-activity relationship (QSAR) study has been performed to determine the molecular features of carbamate anticonvulsants which influence biological activity. Although carbamates, such as felbamate, have been used to treat epilepsy, their mechanisms of efficacy and toxicity are not completely understood. Quantum and classical mechanics calculations have been exploited to describe 46 carbamate drugs. Employing a principal component analysis and multiple linear regression calculations, five crucial structural descriptors were identified which directly relate to the bioactivity of the carbamate family. With the resulting mathematical model, the biological activity of carbamate analogues can be predicted with 85-90% accuracy.

Anticonvulsants↗
PubMed1997

Early failure of the porous coated anatomic cemented unicompartmental knee arthroplasty. Aids to diagnosis and revision.

Unicompartmental knee arthroplasty (UKA) is performed less frequently than total (tricompartmental) knee arthroplasty (TKA). This study examined the range of presenting symptoms and usefulness of diagnostic tests to determine the failure mode; the outcome of surgical revision of failed UKA is also reported. From a consecutive prospective series of 43 Porous Coated Anatomic (Howmedica, Rutherford, NJ) UKAs performed between 1985 and 1992 and followed for an average of 64 months, 12 cases have come to revision surgery (28%). The average time to failure was 37 months. Symptoms preceded revision surgery by an average of 10 months. The most common presenting symptom was pain (100%), followed by swelling (92%), reduced range of motion (42%), instability (42%), and clicking (17%). Failure was caused by polyethylene wear in 50%, loosening of the femoral component in 42%, and progression of patellofemoral arthritis in one patient. The combination of single leg standing anteroposterior radiographs and supine lateral radiographs detected most causes of UKA failure. A bone scan was confirmatory in every case of suspected loosening of the femoral component. Arthroscopy diagnosed polyethylene wear in two cases and progression of joint arthritis in one case and was not helpful in one case. Revision surgery was done with primary TKA components, and follow-up periods averaged 27 months. Bone stock deficiency was found in 58%, but required bone-grafting in only one case. Revision surgery successfully restored pain-free function and range of motion in all cases. Two-year postrevision Hospital for Special Surgery scores are equal to those for primary TKA. Survivorship analysis showed a 33% failure rate at 57 months after Porous Coated Anatomic UKA when revision was the endpoint and a 41% failure rate when unsatisfactory clinical status was the endpoint. Regular follow-up evaluation is suggested for the Porous Coated Anatomic UKA.

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