Carbon monoxide wash-in method to determine gas transfer in vascular beds: application to rat hindlimb.

The vascular barrier to gas transfer is an important physiological parameter; however, no readily applicable technique exists to quantitate the process. A simple technique to measure the permeability-surface area (PS) product for gas transfer in vascular beds is proposed using wash in of carbon monoxide (CO) and Crone-Renkin analysis. Wash-in experiments were performed on the perfused hindlimbs of male Wistar rats (n = 15) by using CO as a surrogate marker for oxygen and technetium-99m-labeled albumin as the vascular marker. The use of CO and erythrocyte-free perfusate and the collection of outflow samples into tubes preloaded with erythrocytes obviated the need for an anaerobic collection device or consideration of Hb binding in the analysis. The PS product for CO was determined from the early extraction as 0.013 +/- 0.006 ml. s(-1). g(-1). Compartmental analysis revealed that the fractional recovery of CO was 0.45 +/- 0.14 and the volume of distribution was 2.31 +/- 0.76 ml/g. This technique detected a small measurable barrier to the transfer of CO across the hindlimb vasculature and is potentially applicable to other vascular beds in health and disease.

Computed tomography in the diagnosis of equivocal appendicitis.

BACKGROUND: The clinically obscure right iliac fossa (RIF) pain remains a diagnostic problem. The present study examines the use of computed tomography (CT) in improving the accuracy of clinical assessment in these difficult surgical cases. METHODS: The trial design was a retrospective review of all patients admitted under one surgeon with suspected acute appendicitis, between 1 January 1995 and 30 June 1997. The study setting was a district hospital (Calvary Hospital) that received patients from both an urban and rural environment. The patient cohort was identified from the Unit Registry and an International Classification of Diseases-based review of medical records. Twenty-one prospective data points were obtained from patient records. Those patients admitted with RIF pain and equivocal symptoms and signs subsequently underwent a CT and/or ultrasound (US) examination, conducted by the attending radiologist. For those patients who proceeded to appendicectomy, the histopathological findings were correlated with the imaging report. Those patients who were discharged after imaging without proceeding to operation were not readmitted to any regional hospital during the course of the study. RESULTS: A total of 84 patients were identified. Thirty-three patients (39%) underwent appendicectomy without imaging and were excluded from further analysis. A total of 51 patients (61%) underwent 61 imaging procedures. The CT scan was correct in 35/36 patients (97%), while US was correct in 17/25 patients (68%). CONCLUSIONS: The present study suggests that CT can be used to improve the accuracy of diagnosis of obscure RIF pain. As a pilot study, it supports the development of a randomized controlled trial in a multicentre regional study.

In situ measurements of skeletal muscle power output using new capacitive strain gauge.

Experiments are described in which a fatigue index is determined for the latissimus dorsi muscle of sheep in situ, using capacitive strain gauges. Parallel experiments for invasive and non-invasive measurements are conducted, measuring global contraction and relaxation rates and shortening duration for paced muscle. The results show that, above one pulse per burst (5 V, 100 microseconds pulsewidth), contraction rates (62 +/- 11 mm s-1) and relaxation rates (50 +/- 7 mm s-1) are constant for unloaded muscle. For one animal, fatigue testing with a 2.5 kg load at six pulses per burst shows shortening rates increasing to a maximum (80 mm s-1) after 30 s and reducing to 5 mm s-1 after 150 s. The decrease in shortening amplitude is used as a fatigue index, log displacement against time. Power output is load dependent, measuring 4.7 W kg-1 with a 2.5 kg load. There is good agreement between the invasive and non-invasive measurements, thus providing a method for monitoring changes in muscle parameters non-invasively during future pacing transformation.

Aortic reconstructive surgery for limb ischaemia: immediate and long-term follow-up to provide a standard for endovascular procedures.

PURPOSE: Aortobifemoral and aortobiliac bypass has been a preferred treatment of severe aortoiliac occlusive disease. Recently, endovascular procedures and unilateral bypass grafting have been introduced. We report the results of aortic reconstructive surgery over a 19-year period (1975-1994). METHODS: A total of 285 patients underwent surgery. Follow-up data from clinical notes, general practitioner questionnaire or phone interview was available in 93.3% (266/285). RESULTS: Of the total 68% were male (180/226) and the median age was 63 years (range 22-85 years). Indications for surgery were tissue loss/gangrene (n = 32), rest pain (n = 84), severe claudication (n = 40), moderate claudication (n = 110). Total of 177 bifurcated grafts, 51 iliofemoral, eight left/right aortofemoral, and 30 other procedures were performed. The median duration of follow-up was 49.8 months. Cumulative secondary graft patency for 2, 5 and 10 years was 97.7%, 95.9%, and 94.4%. The amputation rate was 4.5% (12/266). Early mortality occurred in eight of 266 patients (3%) and late mortality in 60 patients. The most common cause of late death was ischaemic heart disease (24/60 followed by cancer (14/60). Data was further analysed by type of graft, risk factors, complications and previous and subsequent surgery. In our experience, aortic reconstructive surgery is a successful option for the management of severe aortoiliac occlusive disease. The outcome of other methods of maintaining arterial patency should be measured against this standard.

Teaching normal physical examination in a large-group interactive using artists' models.

BACKGROUND: The innovative use of artists' models within the context of a large-group interactive teaching session, at Royal North Shore Hospital is reviewed. METHODS: The models were used to teach normal physical examination skills to a group of junior medical students, during their surgical rotation. This same group of students were also exposed to traditional bedside tutorials. The students evaluated both teaching experiences. RESULTS: In the four areas of evaluation (interaction, explanation, presentation, and organization), the large-group interactive sessions were consistently rated higher than the bedside tutorial (P < 0.001). CONCLUSIONS: The teaching technique is presented as an effective way of delivering quality clinical training to a group of junior medical students in an environment where access to good teaching material is becoming increasingly difficult.

Limitations of intra-arterial thrombolysis.

The purpose of this study was to assess the efficacy, costs and complications of acutely ischaemic limbs initially treated with urokinase-induced thrombolysis, and to compare the subsequent patencies of occluded native arteries, vein grafts and prosthetic grafts. Data from 45 consecutive episodes of thrombolysis in 37 patients (37 limbs) were reviewed retrospectively. An initial bolus dose of urokinase was used in all limbs, with pulse-spray in nine 30 limbs received additional infusions of urokinase including six who received initial treatment with pulse-spray. Percutaneous transluminal angioplasty or surgical intervention was undertaken at any stage when considered appropriate. There were 14 occluded native arteries (31%), 12 vein grafts (27%), 16 prosthetic polytetrafluoroethylene grafts (35%), and three composite grafts (7%). Thrombolysis was initially successful in 33 episodes (73%). Of these, no additional procedure was required in three, percutaneous transluminal angioplasty in 23, other surgery in 11 and bypass surgery in seven with more than one additional procedure being undertaken in 10. Of the 12 episodes with initial failure, major surgery was performed in eight and no procedure in four. Lysis-related complications occurred in 19 treatment episodes (42%) with major bleeding in seven (16%), minor bleeding in 10 (22%), distal embolization in 11 (24%) and arterial dissection in two (4%). One amputation (2%) and one death (2%), both directly attributable to thrombolysis, occurred within 1 month of treatment. Complications occurred in 10 of 19 (53%) prosthetic or composite grafts, five of 12 (42%) vein grafts, and four of 14 (29%) native artery occlusions (P = 0.38). The median follow-up of patients remaining alive was 24 months. The overall mean (s.e.m.)patency rate at 6 months of lysed vessels or replacement bypass grafts was 44% (8%). Presentation with a native artery and or graft occlusion was associated with superior long-term patency (any subsequent conduit) compared with presentation with an occluded prosthetic graft (log rank chi2[1] = 7.00, P = 0.008) and reflects the inferior run-off of the latter patients. The average cost of thrombolysis in radiological procedures and disposables alone excluding intensive care and complications was AUD$2440.

The incidence of deep venous thrombosis after laparoscopic cholecystectomy.

OBJECTIVE: To determine the incidence of deep venous thrombosis (DVT) after laparoscopic cholecystectomy. DESIGN: Prospective cross-sectional analysis, with a one-month follow-up, conducted in 1994. SETTING: University teaching hospital. SUBJECTS: 20 patients undergoing elective or urgent laparoscopic cholecystectomy, consecutively recruited. INTERVENTIONS: Patients received thromboprophylaxis according to the normal practice of the attending surgeon and underwent laparoscopic cholecystectomy. A venous duplex scan was performed before the operation and on Day 1, 7 and 30 after the operation. MAIN OUTCOME MEASURE: The presence of postoperative DVT. RESULTS: All patients were given graduated compression stockings to wear and 16 received electrical stimulation of the calf during the operation. Only 16 patients received pharmacological thromboprophylaxis before the operation, but all patients received this after the operation. The median duration of pneumoperitoneum was 80 minutes (40-160 minutes). Eleven of 19 patients completing all the required scans developed venous thrombosis (incidence, 55%); in three the thromboses involved major axial veins. In one patient the Day 7 and Day 30 scans were not performed, but the Day 1 scan was negative. Seven of the 11 thromboses were detected on the Day 1 scan. None of the DVTs were suspected clinically. CONCLUSIONS: This extremely high incidence of venous thrombosis correlates with the haemodynamic changes which occur in the venous system during pneumoperitoneum. Laparoscopic cholecystectomy should not be considered a procedure with a low risk of DVT, and further studies are needed to determine optimal DVT prophylaxis for laparoscopic surgery.

Cellulitis and the occult diabetic.

BACKGROUND: Occult diabetes may be an important factor in the development of cellulitis and cellulitis may act as a precipitant to the diagnosis of diabetes mellitus. The present study defines the prevalence of diabetes and glucose tolerance impairment in a group presenting with cellulitis to a teaching hospital. A description of the demographic and pathological presentation of the group is undertaken. METHODS: Five hundred consecutive admissions for cellulitis to a Sydney teaching hospital were analysed. The cases presented between 1985 and 1994. Precipitating factors, length of stay, site of infection, white cell count, degree of fever, blood sugar estimation, history of diabetes mellitus and microbiological diagnosis were recorded. RESULTS: Forty-nine patients had a prior diagnosis of diabetes mellitus. Twenty-one percent of patients (56/265) were noted to have abnormal glucose tolerance on routine testing. Thirty-seven per cent of the 1994 cohort (14/38) demonstrated abnormal glucose tolerance. The most common precipitant was trauma (137/500). Mean length of stay was 8.7 days. Microbiological diagnosis was made in 32% of cases. CONCLUSIONS: Cellulitis requiring admission to hospital is a significant problem in terms of cost and bed occupation. A presentation with cellulitis may be a clinical indicator of impaired glucose tolerance. All patients presenting with cellulitis should have a fasting blood sugar level determined as part of routine workup.

Ruptured abdominal aortic aneurysms: who should be offered surgery?

PURPOSE: Operation for ruptured abdominal aortic aneurysm is generally still associated with a high mortality rate. A review of our experience over a 9-year period was undertaken to identify factors present on admission associated with 30-day operative mortality. METHODS: A retrospective analysis of 154 patients with ruptured abdominal aortic aneurysm submitted for operation in a university teaching hospital between January 1985 and December 1993 was undertaken. RESULTS: The hospital mortality rate was 39%. Logistic regression identified a set of five independent preoperative factors associated with mortality: age (> 76 years), creatinine level (> 0.19 mmol/L), loss of consciousness after arrival, Hb (< 9 g%), and electrocardiographic ischemia. In the 52 patients with a single risk factor present, the mortality rate was 37%, with two factors (32 patients) it was 72%, with three or more factors (8 patients), it was 100%, and no patient had all five risk factors. A 16% mortality rate was found in the 62 patients with no risk factors. CONCLUSION: These risk factors can be easily determined on admission and may be used to help improve patient selection for surgical intervention. The current operative mortality rate for ruptured abdominal aortic aneurysm remains high, and in some cases health care resources are used in a nonproductive fashion. Restricted patient selection and allocation of scarce resources will bring advantages to both the patient and the community.

The economic cost of elective carotid endarterectomy.

Cost awareness and accountability for the use of health care resources have become major issues for clinicians. In order to identify the economic costs associated with carotid endarterectomy (CEA), a retrospective review of 50 elective CEA between May 1993 and April 1994 was undertaken. Despite our belief [based on the Australian National Diagnostic Related Groupings (ANDRG)], that our resource utilization had been refined to produce a median length of stay significantly below the New South Wales (NSW) State average, this study has identified several areas of non-productive expenditure. The mean cost of CEA per patient was $7053. This figure includes non-productive expenditure of $793 per patient in the pre-operative period and $395 per patient in the postoperative period. If these costs, which did not contribute to patient care, were removed the mean cost of CEA would be $5865. The major causes of non-productive resource utilization included prolonged pre-operative stay, duplicated or omitted investigations, as well as the use of the Intensive Care Unit for patient monitoring in the postoperative period.