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Kenneth A Harris

Publications and source records attributed to Kenneth A Harris.

30 records · Page 2Linked to original sources
PubMed2004

Cumulative sum failure analysis of the learning curve with endovascular abdominal aortic aneurysm repair.

PURPOSE: The purpose of this study was to evaluate the importance of experience and the learning curve with endovascular abdominal aortic aneurysm (AAA) repair. METHODS: A retrospective analysis was performed of all elective endovascular AAA repairs attempted by an individual surgeon and radiologist over a 4-year period. The primary outcome variable was achievement and 30-day maintenance of initial clinical success as defined by the Society for Vascular Surgery/American Association of Vascular Surgery reporting standards. Following standard statistical analysis, the cumulative sum (CUSUM) method was used to analyze the learning curve, with a predetermined acceptable failure rate of 10% and calculated 80% alert and 95% alarm lines. RESULTS: Ninety-six elective endovascular AAA repairs were attempted by this team between 1998 and 2002 (mean age 74 +/- 0.8 years; mean aneurysm diameter 5.98 +/- 0.8 cm). Initial clinical success was achieved and maintained in 85 of 96 patients (88.5%). Although results were acceptable throughout the study period, improved results with respect to the target failure rate (10%) were not achieved until 60 patients were treated. The learning or CUSUM curves did not differ for different device manufacturers, with improved results being achieved following 20 implantations of each device. The results did differ when comparing aortouniiliac grafts (n = 27) and bifurcated grafts (n = 64). Results with bifurcated grafts remained consistent throughout the study period, whereas with aortouniiliac grafts, results improved after only a few procedures in comparison with the target failure rate. CONCLUSION: Success rates with endovascular aneurysm repair will improve with an individual's experience. The CUSUM method is a valuable tool in the evaluation of this learning curve, which has credentialing and training implications. Although acceptable results were obtained throughout the study period, this analysis indicates that 60 endovascular aneurysm repairs, or 20 with an individual device, are necessary before optimal rates of initial clinical success can be achieved. These results can be achieved more readily with aortouniiliac grafts than with bifurcated grafts.

Aged↗
PubMed2004

Chronic lower extremity ischemia: a human model of ischemic tolerance.

BACKGROUND: Ischemic preconditioning (IPC) has been found in animals to have a protective effect against future ischemic injury to muscle tissue. Such injury is unavoidable during some surgical procedures. To determine whether chronic ischemia in the lower extremities would imitate IPC and reduce ischemic injury during vascular surgery, we designed a controlled clinical study. PATIENTS AND METHODS: Two groups of patients at a university-affiliated medical centre with chronic lower-extremity ischemia served as models of IPC: 6 patients awaiting femoral distal bypass (FDB) and 4 scheduled for aortobifemoral (ABF) bypass grafting for aortoiliac occlusive disease. Seven patients undergoing elective open repair of an infrarenal abdominal aortic aneurysm (AAA) were chosen as non-IPC controls. Three hematologic indicators of skeletal-muscle injury, lactate dehydrogenase (LDH), creatine kinase (CK) and myoglobin, were measured before placement of the proximal clamp, during surgical ischemia, immediately upon reperfusion, 15 minutes after and 1 hour after reperfusion, and during the first, second and third postoperative days. RESULTS: Baseline markers of skeletal-muscle injury were similar in all groups. In postreperfusion samples, concentrations of muscle-injury markers were significantly lower in the 2 PC groups than in the control group. For example, at day 2, LDH levels were increased by about 30% over baseline measures in the elective AAA (control) group, whereas levels in the FDB and ABF groups remained statistically unchanged from baseline. Myoglobin in controls had increased by 977%, but only by 160% in the FDB and 528% in the ABF groups. CK levels, in a similar trend, were 1432% higher in the control group and only 111% (FDB) and 1029% (ABF) in the study groups. Taken together, these data represent a significant level of protection. CONCLUSIONS: Patients with chronic lower-extremity ischemia suffered less severe ischemic injury after a period of acute ischemia than those with acute ischemia alone. Ischemic preconditioning is one proposed mechanism to help explain this protective effect.

Aged↗
PubMed2004

Is intensive care necessary after elective abdominal aortic aneurysm repair?

BACKGROUND: To review morbidity and mortality of patients undergoing elective, open repair of infra-renal abdominal aortic aneurysms and were admitted postoperatively to a surgical stepdown unit rather than routinely to the intensive care unit (ICU), we carried out a retrospective review. METHODS: All patients undergoing this type of repair in our centre, a division of vascular surgery in a tertiary-care teaching hospital in Ontario, over a 27-month period were reviewed. A consecutive 230 patients who underwent aneurysm repair from September 1999 through November 2001 were routinely admitted to a surgical stepdown unit postoperatively, with only a minority of patients requiring admission to ICU. We reviewed the rate of initial ICU admission and that of subsequent ICU admission after stepdown-unit admission. We also assessed morbidity, mortality and length of hospital stay for patients admitted to ICU as well as those admitted to the stepdown unit. RESULTS: ICU admission was avoided in 204 (89%) of these patients. The remaining 26 patients (11%) required ICU admission at some point during their hospital stay. Only 3 patients (1%) originally admitted to the stepdown unit subsequently required postoperative admission to ICU. CONCLUSIONS: Our experience demonstrates that proper preoperative assessment and selection allows the majority of elective infra-renal aneurysm repairs to be safely cared for postoperatively in a stepdown unit, and that subsequent ICU admissions are rare.

Aged↗
PubMed2003

Limitations of ischemic tolerance in oxidative skeletal muscle: perfusion vs tissue protection.

OBJECTIVES: This study determined if ischemic tolerance occurs in oxidative skeletal muscle following a severe ischemia/reperfusion (I/R) insult and if such protection involves the induction of nitric oxide synthase (NOS). METHODS: The soleus muscle of male Wistar rats (250-350 g) was preconditioned (PC + I/R) using five cycles of ischemia (10 min) and reperfusion (10 min) or had no PC (I/R) and 24 h later 2 h no-flow ischemia was induced. Calcium dependent (cNOS) and independent (iNOS) NOS activities were determined from PC (n = 5), or sham (n = 5) and the role of iNOS was tested by application of aminoguanidine (AMG) (100 microM; n = 4) to the muscle bath. Direct measures of the number of perfused capillaries (Npc; #/mm) during 90-min reperfusion were obtained using intravital microscopy. Tissue injury was estimated using the fluorescent vital dyes ethidium bromide (E; labels injured cells) and bisbenzimide (B; labels all cells) and expressed as the ratio E/B. RESULTS: PC prevented microvascular flow deficits (Npc:I/R = 23.4 +/- 1.3 vs PC + I/R = 29.9 +/- 1.1) and resulted in a modest, but significant reduction (21%) in tissue injury (I/R = 0.82 +/- 0.03 vs PC + I/R = 0.64 +/- 0.04). PC led to a nine fold increase in iNOS activity, but decreased cNOS activity by 94% compared to sham. AMG prevented the parenchymal protection following PC, but had no effect on microvascular perfusion. CONCLUSIONS: Ischemic tolerance, 24 h following PC, preserved microvascular perfusion, but only modestly improved tissue viability in the soleus muscle.

Animals↗
PubMed2003

Effect of electrical stimulation on chronic leg ulcer size and appearance.

BACKGROUND AND PURPOSE: Electrical current has been recommended for use on chronic pressure ulcers; however, the ability of this modality to improve healing of other types of chronic ulcers is less well established. The purpose of this study was to examine the effect of high-voltage pulsed current (HVPC) on healing of chronic leg ulcers. SUBJECTS: Twenty-seven people with 42 chronic leg ulcers participated in the study. METHODS: The subjects were separated into subgroups according to primary etiology of the wound (diabetes, arterial insufficiency, venous insufficiency) and then randomly assigned to receive either HVPC (100 microseconds, 150 V, 100 Hz) or a sham treatment for 45 minutes, 3 times weekly, for 4 weeks. Wound surface area and wound appearance were assessed during an initial examination, following a 1- to 2-week period during which subjects received only conventional wound therapy, after 4 weeks of sham or HVPC treatment, and at 1 month following treatments. RESULTS: The results indicated that HVPC applied to chronic leg ulcers reduced the wound surface area over the 4-week treatment period to approximately one half the initial wound size (mean decrease=44.3%, SD=8.8%, range=2.8%-100%), which was over 2 times greater than that observed in wounds treated with sham units (mean decrease=16.0%, SD=8.9%, range=-30.3%-83.7%). DISCUSSION AND CONCLUSION: The results of the study indicate that HVPC administered 3 times a week should be considered to accelerate wound closure of chronic leg ulcers.

Adult↗
PubMed2002

A CUSUM analysis of ruptured abdominal aortic aneurysm repair.

Studies have investigated the role of hospital and surgeon case volume in outcome after ruptured abdominal aortic aneurysm repair (rAAA). Few have analyzed the learning curve of an individual surgeon. The purpose of this study was to analyze this learning curve in reducing morbidity and mortality after rAAA repair. Thirty-two consecutive patients who underwent rAAA repair during the initial 2.5 years of a vascular surgeon's career were reviewed retrospectively. They were divided temporally into two groups of 16 patients (groups 1 and 2). Outcome measures included mortality, postoperative myocardial infarction, stroke, and renal and respiratory failure. Perioperative variables previously associated with increased mortality were analyzed. The cumulative sum (CUSUM) method was used to analyze the learning curve with respect to published acceptable event rates and predetermined 80% alert and 95% alarm boundary lines. Groups 1 and 2 did not differ statistically in age, preoperative blood pressure, hemoglobin or creatinine. There was no difference in transfusion requirements (6.8 +/- 1.2 units vs. 6.4 +/- 1.0 units; p = 0.78), urine output (340 +/- 65 mL vs. 389 +/- 94 mL; p = 0.72) or clamp position. There was no difference in the incidence of postoperative myocardial infarction, stroke, or respiratory or renal failure. Thirty-day mortality in group 2 was 12% as compared to 50% in Group 1 (p = 0.03). On CUSUM analysis, the cumulative failure rate in group 2 progressed lower than the 80% reassurance line, indicating improved results with time. Mortality after rAAA repair decreased over time during an early period of an individual surgeon's career. The CUSUM method is a valuable tool in analyzing an individual surgeon's experience and shows promise in quality control in vascular surgery.

Aged↗
PubMed2002

Acute aortic thrombosis following incorrect application of the Heimlich maneuver.

The Heimlich maneuver has been widely accepted as a safe and effective method of relieving life-threatening foreign-body upper airway obstruction. When applied incorrectly, however, it may result in direct trauma to the intraabdominal viscera. Only two cases of major aortic complications have been reported. Both have involved thrombosis of an abdominal aortic aneurysm. We report two further instances of aortic thrombotic complications due to the incorrect application of the Heimlich maneuver. The first case resulted in thrombosis of an abdominal aortic aneurysm. In the second case the abdominal thrusts caused dislodgement of thrombus from an atherosclerotic nonaneurysmal aorta, which resulted in thromboembolic occlusion of both lower extremities. In both cases, as with the two previously reported instances, massive reperfusion injury resulted, which eventually proved fatal. When applied incorrectly, the Heimlich maneuver may result in direct trauma to the abdominalaorta and is an unusual cause of acute aortic thrombosis.

Acute Disease↗
PubMed2002

The role of endogenous heme oxygenase in the initiation of liver injury following limb ischemia/reperfusion.

BACKGROUND/AIMS: Heme oxygenase (HO) derived liver protection was tested in mice following 1 h bilateral hindlimb ischemia and either 1.5 or 3 h reperfusion. METHODS: Groups consisted of limb ischemia/reperfusion (I/R), sham (no I/R), I/R+chromium mesoporphyrin (I/R+CrMP;40 micromol/kg, i.p.), or I/R+hemin (10 mg/kg, i.p.). The vital dye propidium iodide (PI), was used to measure hepatocellular death (#/0.1 mm(3)), while the number of sinusoids perfused by red blood cells (SP(RBC)) were measured from the periportal (Pp) and pericentral (Pc) zones of liver acini using intravital microscopy. Whole organ injury was estimated from serum alanine aminotransferase (ALT). RESULTS: SP(RBC) reduced within 1.5 h with no further decline following 3 h. CrMP resulted in a dramatic loss of SP(RBC) following 3 h only. Hemin restored perfusion in both zones. Hepatocellular death and organ injury increased at 1.5 and 3 h. At 1.5 h, CrMP further increased cell death in the Pc zone, as well as whole organ injury, while hemin restored cell viability. Increased HO mRNA, protein and activity suggested induction within 3 h. CONCLUSIONS: HO does not protect perfusion during the early stage (1.5 h), but becomes increasingly important in preserving liver perfusion and cell viability during the later stage (3 h) of liver injury.

Alanine Transaminase↗
PubMed2002

Is long-term anticoagulation after acute thromboembolic limb ischemia always necessary?

OBJECTIVE: After thromboembolectomy, patients with acute limb ischemia often receive anticoagulant therapy to prevent recurrent events. Patients with atrial fibrillation or cardiac thrombus have a higher risk of recurrent emboli than those without these risk factors. This study examines the importance of long-term anticoagulation in these 2 groups. DESIGN: A review of patients presenting with acute limb ischemia over a 5-year period (1994-1999). SETTING: A university-affiliated medical centre. PATIENTS: Fifty patients divided into 2 groups: 19 (38%) patients with atrial fibrillation (group 1) and 31 (62%) patients with no atrial fibrillation or cardiac thrombus (group 2) as confirmed by transthoracic echocardiography. INTERVENTION: All patients underwent surgical thromboembolectomy and received postoperative anticoagulant therapy. OUTCOME MEASURES: Mortality, limb loss, further thromboembolic events and bleeding complications as determined by telephone survey. RESULTS: There was a significant difference in 5-year survival (group 1, 84%; group 2, 64%) and early limb loss (group 1, 0%; group 2, 13%). Further thromboembolic events and bleeding complications were rare but were more common in group 1. In group 2 there were no instances of recurrent thromboemboli and no bleeding complications although only 39% of patients in this group were taking angicoagulants at the end of the study period. CONCLUSIONS: Patients with extremity thromboemboli without atrial fibrillation or cardiac thrombus may not be at the same risk for recurrent events as those with these risk factors, and long-term anticoagulant therapy may not be as necessary in this group.

Adult↗
PubMed2002

A cost-effectiveness analysis of standard versus endovascular abdominal aortic aneurysm repair.

OBJECTIVE: To compare endovascular and standard open repair of abdominal aortic aneurysms in terms of initial in-hospital costs and the costs of secondary interventions and surveillance. DESIGN: A retrospective study. SETTING: A university-affiliated tertiary care medical centre. PATIENTS: Seven patients who underwent elective endovascular (EV) repair of an abdominal aortic aneurysm in 1998 and 31 patients anatomically suitable for endovascular repair who underwent standard (STAN) elective repair. Follow-up ranged from 2 to 14 months. INTERVENTIONS: Elective repair of an abdominal aortic aneurysm with use of the standard technique or endovascular technology. OUTCOME MEASURES: Costs common to both groups were not determined. Costs were determined for total hospital stay, preoperative or postoperative embolization, grafts, additional endovascular equipment, and follow-up computed tomography. RESULTS: Groups were similar with respect to demographic data and aneurysm size (EV = 6.23 cm v. STAN = 6.05 cm). All patients were in American Society of Anesthesiologists class III or IV. Vanguar bifurcated grafts and extensions were used in the EV group. The total cost for both groups in Canadian dollars included: cost of stay (EV, 5.6 d, $2092.63 v. STAN, 10.7 d, $4449.19; p = 0.009); cost of embolization (EV, n = 3; $900/procedure); cost of follow-up CT (EV, 5.4 per patient; $450/CT); cost of grafts (EV = $8571.43, STAN = $374); additional radiologic equipment costs (EV = $1475). The mean total cost differed significantly between the 2 groups (EV = $14,967.63 v. STAN = $4823.19; p = 0.004). The additional cost associated with a reduction in hospital stay was calculated by determining the incremental cost-effectiveness ratio (ICER, difference in mean costs/difference in mean length of stay = $1604.51). CONCLUSIONS: Endovascular repair continues to be more expensive than standard open repair determined according to procedural and follow-up costs. The technology is still in the developmental stage, but as it evolves and follow-up protocols are streamlined, it is hoped that there will be an eventual reduction in the costs associated with the endovascular procedure.

Aortic Aneurysm, Abdominal↗
PubMedDate not supplied

Remote liver injury is attenuated by adenovirus-mediated gene transfer of heme oxygenase-1 during the systemic inflammatory response syndrome.

OBJECTIVES: Adenovirus-mediated gene therapy is being investigated with increasing success for future treatment of autoimmune diseases. However, the use of adenoviruses is still limited by inflammatory and immune responses in the target organ. Previous work by the authors' laboratory established that the adenovirus encoding inducible heme oxygenase (Ad-HO-1) does not elicit the acute hepatic inflammation normally caused by adenoviruses, inviting further investigation in models of severe inflammation. Concurrently, there is increasing evidence for an endogenous protective role for heme oxygenase (HO) in the liver during the systemic inflammatory response syndrome (SIRS). Building on our previous results, this study investigated the effect of Ad-HO-1 pretreatment on remote liver injury during normotensive SIRS, induced by bilateral hind limb ischemia and reperfusion. METHODS: Microvascular perfusion and hepatocyte death were quantified using established intravital videomicroscopy techniques. Hepatocellular injury and liver function were assessed using blood-borne indicators. RESULTS: Microvascular perfusion deficits and increased hepatocyte death occurred following limb ischemia and 3 h of reperfusion in vehicle-pretreated animals; however, Ad-HO-1 pretreatment prevented these deficits. In contrast, the increase in serum alanine transaminase levels was unaffected by Ad-HO-1 pretreatment. Serum bilirubin levels were increased during systemic inflammation, predominantly in the conjugated form; and, this increase was prevented by administration of Ad-HO-1. CONCLUSIONS: These data indicate that gene transfer of inducible HO is an effective method to protect the liver during SIRS, providing incentive for further investigation into gene therapy strategies exploiting this anti-inflammatory enzyme.

Adenoviridae↗