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Biomedical subjects

L L Lau

Publications and source records attributed to L L Lau.

At least 19 recordsLinked to original sources
PubMed2006

Endovenous laser treatment for long saphenous vein incompetence.

BACKGROUND: Endovenous laser treatment is a percutaneous technique used for the treatment of long saphenous vein (LSV) incompetence. This paper presents the results of an uncontrolled case series undertaken to assess the feasibility, safety and efficacy of this technique. METHODS: Some 145 incompetent LSVs in 136 patients with saphenofemoral reflux were treated with endovenous laser. The data were evaluated prospectively. Assessment was carried out at 1 week, 3 and 12 months for LSV occlusion and symptomatic relief. RESULTS: Primary procedural success was achieved in 124 (85.5 per cent) of 145 LSVs. Reasons for primary failure included failed cannulation, failure to pass the guidewire and patient discomfort. At 3 months' follow-up, 105 (89.7 per cent) of 117 veins were totally and nine (7.7 per cent) were partially occluded. At 12 months, 63 (76 per cent) of 83 veins were totally and 15 (18 per cent) were partially occluded. At this stage 73 (88 per cent) of 83 patients remained satisfied, but 26 (31 per cent) had residual or recurrent varicosities. Of these, only five required further treatment. Complications included saphenous nerve injury in one patient and superficial skin burns in a second. CONCLUSION: Endovenous laser treatment for LSV reflux is safe and can be carried out under local anaesthesia in an outpatient setting with good patient satisfaction and low complication rates.

Adult↗
PubMed2005

The effect of pravastatin on intima media thickness of the carotid artery in patients with normal cholesterol.

OBJECTIVE: Carotid intima media thickness (IMT) is a good indicator of the severity of atherosclerotic disease. Statins have been found to reduce carotid IMT in patients with hypercholesterolaemia. The aim of this study was to investigate if pravastatin is effective in reducing IMT in normocholesterolaemic patients with carotid artery disease. METHODS: Patients with carotid artery stenosis and normal cholesterol levels who were not on a statin, were recruited. Patients were randomised to receive pravastatin or placebo daily. Serum concentration of cholesterol and IMT of common carotid arteries were measured before randomisation and at 3 monthly intervals thereafter, for 9 months. IMT was analysed to give the mean of a standardised 2 cm of the common carotid artery (CCA). Results are expressed as median (IQR) and comparison made using the Wilcoxon signed ranks test. RESULTS: Fifty-four patients were examined. Twenty-eight patients were randomised to active treatment. There was no difference in demographic details and co-morbid states between the two groups. A significant reduction in cholesterol concentration was observed from 3 months in patients randomised to the pravastatin group [5.14(4.72-5.88) vs. 4.11(3.44-5.33), p < 0.05], while there was also a significant decrease in combined IMT form 6 months [1.53(1.36-1.87) vs. 1.41 (1.33-1.78), p < 0.05]. CONCLUSIONS: The results demonstrate that pravastatin reduces intima media thickness of the common carotid artery in normocholesterolaemic patients with moderate carotid stenosis.

Aged↗
PubMed2004

Intra-mucosal acidosis as a predictor of cardiac outcome following abdominal aortic aneurysm surgery.

OBJECTIVE: To assess if sigmoid ischaemia is a prognostic indicator of early and late post-operative cardiac morbidity and mortality. MATERIALS AND METHODS: Patients undergoing elective abdominal aortic aneurysm repair (AAAR) were included in the study. Demographic details and risk factors for heart disease were recorded. Sigmoid pHi was measured at the time of surgery using a silicone tonometer and perioperative morbidity and mortality were recorded in all patients. Seven years following surgery the patients and their general practitioners were contacted to determine the patient's health. RESULTS: Thirty-eight patients were included in the study. Within the follow-up period, 22 (58%) had died. Eight patients died of cardiac failure or myocardial infarction. The pHi in patients with cardiac related deaths [6.99 (6.84-7.10)] was significantly lower than those with non-cardiac related deaths [7.11 (7.04-7.21), p<0.05]. Similarly, patients who suffered acute cardiac events (within 30 days following AAA repair) had lower pHi [7.01 (6.88-7.12)] compared to those who did not [7.09 (6.90-7.19), p<0.05]. CONCLUSION: The results show that sigmoid ischaemia is more frequent amongst patients that develop cardiac events after AAAR and is associated with a worse long term outcome. This suggests that global hypoperfusion as a result of an under performing heart may be partly responsible for the sigmoid ischaemia in patients following AAAR. Therefore, low sigmoid pHi may predict an increased risk of cardiac complications in these patients.

Acidosis↗
PubMed2004

Midterm outcome of endovascular abdominal aortic aneurysm repair in octogenarians: a single institution's experience.

OBJECTIVES: We analyzed midterm durability of endovascular abdominal aortic aneurysm repair (EVAR) in octogenarians compared with younger patients. METHODS: Data for 182 consecutive patients who underwent elective EVAR between 1999 and 2003 were retrospectively reviewed. Forty-nine patients (27%) were 80 years or older (study group [SG]; mean age, 84 years; range, 80-89 years), and 133 patients (73%) were younger (control group [CG]; mean age, 72 years; range, 53-79 years). Chi2 analysis, Fisher exact test, Student t test, and Mann-Whitney U test were used as appropriate to test for intergroup differences. Kaplan-Meier curves, log-rank tests, and multivariate Cox models were used for time-to-event analysis, with P < or =.05 considered significant. RESULTS: Mean follow-up was 16 months (range, 1-43 months). Body weight was higher (P <.001), and elevated plasma lipid levels (59% vs 43%; P =.042) and use of nicotine (47% vs 29%; P =.015) more frequent in the octogenarians. Baseline aneurysm size, procedure-related data, and hospital stay were comparable between groups. Aneurysm-related mortality was 0% in the study group and 0.7% in the control group (P =.740). Systemic complications occurred in 22% (SG) versus 11% (CG) (P =.035), owing to a rise in serum creatinine concentration greater than 30% of baseline in 14% in the octogenarian group (vs 5% in the CG; P =.048). Groin lymphoceles developed in 12% (SG) versus 2% (CG; P =.013). Technical success was 96% (SG) versus 98% (CG; P =.408), and clinical success was 86% versus 90% (P =.269). No aneurysm rupture occurred during follow-up, and aneurysm-related adverse events were comparable between groups. The estimated risk for any type of endoleak (2.2; 95% confidence interval [CI], 1.1-4.2; P =.023) or type II endoleak (2.1; 95% CI, 1.0-4.3; P = 0.51) was higher in the study group versus the control group; however, this did not affect secondary procedure rates (SG 16% vs CG 12%; estimated risk, SG vs CG,: 1.5; 95% CI, 0.6-3.6; P = 0.420) or aneurysm remodeling (97.2% combined aneurysm sac stabilization or decrease in both groups; P =.592). Aneurysm enlargement occurred in 2.8% (SG 1 vs CG 4; P =.592). CONCLUSION: Elective EVAR in octogenarians appears safe and effective over midterm follow-up, with a temporary decrease in renal function (14%) and postoperative lymphoceles (12%) being the most common postoperative adverse events. Advanced chronologic age is not associated with diminished procedural outcome, clinical success, or postoperative survival, compared with younger age. Because of low perioperative mortality and high procedural success, EVAR may be the preferred approach to abdominal aortic aneurysm treatment in selected elderly patients.

Age Factors↗
PubMed2003

The effect of lower limb ischaemia-reperfusion on intestinal permeability and the systemic inflammatory response.

OBJECTIVES: a relationship has been demonstrated between increased intestinal permeability, endotoxaemia and the development of the systemic inflammatory response syndrome (SIRS) after aortic surgery. The aim of this study was to evaluate whether isolated lower limb ischaemia-reperfusion (I/R) injury affects intestinal mucosal barrier function and cytokine release. PATIENTS AND METHODS: four groups of patients were investigated, group I, patients with critical limb ischaemia (CLI) undergoing infra-inguinal bypass surgery (n=18); group II, patients with intermittent claudication (IC) undergoing infra-inguinal bypass surgery (n=14); group III, patients with CLI unsuitable for arterial reconstruction, undergoing major amputation (n=12); and group IV, patients undergoing carotid endarterectomy for symptomatic carotid stenosis (n=13). Intestinal permeability, endotoxaemia and urinary soluble tumour necrosis factor receptors were assessed (p55TNF-R). RESULTS: an increase in intestinal permeability was observed on the 3rd postoperative day only in CLI group. This was found to correlate with arterial clamp time. Patients who had a femoro-distal bypass had significantly higher intestinal permeability compared to those who had femoro-popliteal bypass. Endotoxaemia was not detected in any of the groups. Postoperative urinary p55TNF-R concentrations were significantly higher in CLI group compared to the other groups. These did not correlate with the increased intestinal permeability. CONCLUSIONS: our results support the hypothesis that revascularisation of critically ischaemia limbs leads to intestinal mucosal barrier dysfunction and cytokine release. They also suggest that the magnitude of the inflammatory response following I/R injury is related to the degree of initial ischaemia.

Aged↗
PubMed2002

Accentuated oxidative stress following reperfusion injury in diabetic rats.

BACKGROUND: This study investigates whether diabetes mellitus accentuates hind limb ischemia-reperfusion injury. METHODS: Male Wistar rats rendered diabetic (n=40) following injection of streptozotocin were compared to non-diabetic control rats (n=30). Each group was divided into sham, 4 hrs of hind limb ischemia, 4 hrs of ischemia followed by 10, 30 or 60 min of reperfusion. Plasma concentrations of an end-product of lipid peroxidation [malondialdehyde (MDA)] and antioxidants (vitamins A and E) were measured together with the resting membrane potential (RMP) of the gastrocnemius muscle. RESULTS: Following reperfusion, the diabetic group showed greater and more persistent elevation of MDA and greater reduction of antioxidants. This was associated with reduction in the RMP only in the diabetic group. There was significant correlation between MDA level and the RMP in both groups of animals. CONCLUSIONS: These results indicate that oxidative stress following reperfusion injury is greater in the presence of diabetes mellitus. This may lead to a decrease in the RMP and increase in the vascular permeability, which may be associated with more complications.

Animals↗
PubMed2002

Acute pain services in Hong Kong: facilities, volume, and quality.

Acute pain services in public hospitals in Hong Kong were studied. Audit data on the volume and quality of acute pain services were collected prospectively from 1997 to 1999, and data on related facilities were collected in 2000. About 20% of patients undergoing a major operation received an acute pain service; of these, 78.6% were satisfied with the treatment provided. In 2000, 86% (18/21) of hospitals providing anaesthetic services were running an acute pain service. Staffing was better in hospitals providing a high volume of acute pain services, ranging from a full-time specialist anaesthesiologist assisted by a half-time trainee to a half-time specialist assisted by a full- or half-time trainee. However, only four hospitals were staffed with pain nurses. In total, 57% of patients received intravenous patient-controlled analgesia and 32% epidural analgesia. The mean duration of acute pain service treatment was 3.1 days. Currently anaesthesiologist-based acute pain services take care of a limited number of patients. To expand the coverage, there should be a move towards an anaesthesiologist-led, pain nurse-based, acute pain service. The present shortage of pain nurses should be addressed.

Analgesia, Patient-Controlled↗
PubMed2001

Extraperitoneal approach reduces neutrophil activation, systemic inflammatory response and organ dysfunctionin aortic aneurysm surgery.

OBJECTIVES: to compare the effects of transperitoneal and extraperitoneal approaches on systemic inflammatory response, neutrophil activation and organ dysfunction in elective abdominal aortic aneurysm (AAA) repair. PATIENTS AND METHODS: twenty patients admitted for elective infrarenal AAA repair were prospectively randomised into transperitoneal (n =10) or extraperitoneal ( n =10) groups. Neutrophil activation was assessed by measuring the plasma levels of neutrophil elastase/alpha(1)-anti-trypsin complexes before surgery, intraoperatively and at 6 h, 12 h, 24 h and then daily after surgery. Venous blood samples for estimation of liver function tests, full blood counts, urea and electrolytes and arterial samples for blood gas analysis were taken daily from preoperatively to day 5 after surgery. Multiple organ dysfunction (MOD) and systemic inflammatory response (SIR) scores were calculated daily. RESULTS: the concentrations of neutrophil elastase/alpha(1)-anti-trypsin complexes were significantly higher in the transperitoneal group at 6 h after surgery compared to the extraperitoneal group (799(455-921) ng/ml (median(i.q.r.)) vs 307(171-395) ng/ml, p<0.005), and at 12 h (397(364-936) ng/ml vs 319(134-352) ng/ml, p <0.05). The MOD scores were significantly higher in the transperitoneal group in comparison to the extraperitoneal group at day 1 (2.5(2-3.3) vs 1(0-1), p<0.001) and day 2 (2.5(2-3.3) vs 1(0-1), p <0.001). The SIR scores were also significantly higher at day 1 (1(0-2) vs 0, p <0.01), day 2 (1.5(0-2.3) vs 0, p <0.01), and day 3 (1(0-1) vs 0, p <0.05). CONCLUSIONS: neutrophil activation, systemic inflammatory response and organ dysfunction are increased in elective AAA repair when a transperitoneal approach is used. This may be related to intestinal manipulation and mesenteric traction which are reduced in the extraperitoneal approach.

APACHE↗
PubMed2001

Endovascular stent-graft repair of primary aortocaval fistula with an abdominal aortoiliac aneurysm.

A primary aortocaval fistula is present in less than 1% of all abdominal aortic aneurysms. Until recently, surgical repair was the only method of treatment and was associated with a high incidence of morbidity and mortality. With the rapid development of aortic stent-graft technique, endovascular stent-graft repair may offer an alternative to the management of this often fatal condition. We report a case of an aortoiliac aneurysm with an aortocaval fistula successfully treated with endovascular stent-grafting. The unique hemodynamic changes, technical problems, and complications associated with this case are discussed, and the literature is reviewed.

Aortic Aneurysm, Abdominal↗
PubMed2001

Anaesthetic clinical indicators in public hospitals providing anaesthetic care in Hong Kong: prospective study.

OBJECTIVES: To assess the quality of anaesthetic services as defined in the six anaesthetic clinical indicators against preset standards and to identify risk factors for adverse events in the recovery room. DESIGN: Prospective study. SETTING: All public hospitals providing anaesthetic care in Hong Kong. PATIENTS: Eighteen thousand, seven hundred and fifty-nine patients receiving elective or emergency anaesthesia administered by anaesthetists from June 1998 to July 1998. MAIN OUTCOME MEASURES: Patient demographics, American Society of Anesthesiologists status, category and nature of operation, presence of preoperative anaesthetic visit in ward, type of anaesthesia, reasons for a recovery room stay of more than a 2-hour duration, intubation to relieve respiratory distress in the recovery room, presence of hypothermia in the recovery room for operations lasting more than 2 hours, and dental or ocular injuries attributable to anaesthesia. RESULTS: There are two major findings from this study. Firstly, a high incidence of hypothermia in the recovery room was reported. Secondly, a greater risk of prolonged stay in the recovery room was identified for patients older than 65 years, major operations, and anaesthetic techniques using combined general and regional anaesthesia. CONCLUSION: The six anaesthetic clinical indicators reflected the provision of anaesthetic care in public hospitals in Hong Kong. Good compliance to the preset standard of the anaesthetic clinical indicators was achieved during the study period.

Adolescent↗
PubMed2001

Extraperitoneal approach reduces intestinal and renal dysfunction in elective abdominal aortic aneurysm repair.

BACKGROUND: Intestinal mucosal barrier dysfunction observed in patients undergoing transperitoneal abdominal aortic aneurysm (AAA) repair may contribute to the development of the systemic inflammatory response syndrome and dysfunction of various organs. The aim of this study is to investigate whether an extraperitoneal approach reduces intestinal mucosal barrier and renal dysfunction in elective infrarenal AAA repair. METHODS: Twenty patients admitted for elective infrarenal AAA repair were randomized into either the transperitoneal approach (n=10) or the extraperitoneal approach (n=10). Intestinal permeability was measured preoperatively, and at day 1 and day 3 after surgery using the lactulose/mannitol test by calculating the differential urinary excretion ratio of the two sugars after oral administration. Renal dysfunction was assessed by measuring the urinary albumin/creatinine ratio (ACR) at the same time points. RESULTS: Intestinal permeability was significantly increased in the transperitoneal group at day 1 [0.124+/-0.035 (mean+/-s.e.m.)] compared to the preoperative level (0.020+/-0.003), (p=0.001) and to the extraperitoneal group at day 1 (0.025+/-0.008), (p<0.05) which showed no change in comparison with the preoperative level (0.020+/-0.003). The ACR was also significantly increased in the transperitoneal group at day 1 (16.69+/-5.12) compared to the preoperative level (5.71+/-2.89), (p<0.05) and to the extraperitoneal group at day 1 (4.33+/-1.49), (p<0.05) which showed no significant change at any of the times examined. No correlation was observed between the lactulose/mannitol ratio and the albumin/creatinine ratio, or between age, operating time, aortic clamping time, amount of blood lost or blood transfused. CONCLUSIONS: These results support the suggestion that minimising intestinal manipulation using an extraperitoneal approach in AAA repair preserves intestinal mucosal barrier and renal glomerular functions.

Aged↗
PubMed2000

Altered aging-related thymic involution in T cell receptor transgenic, MHC-deficient, and CD4-deficient mice.

During aging in mice and humans, a gradual decline in thymus integrity and function occurs (thymic involution). To determine whether T cell reactivity or development affects thymic involution, we compared the thymic phenotype in old (12 months) and young (2 months) mice transgenic for rearranged alphabeta or beta 2B4 T cell receptor (TCR) genes, mice made deficient for CD4 by gene targetting (CD4(-/-)), mice made deficient for major histocompatibility complex (MHC) class I (beta2M-/-) or class II genes (A(beta)(b-/-) on C57Bl/6 background) or both. The expected aging-related reductions in thymic weights were observed for all strains except those bearing disruption of both class I and class II MHC genes. Therefore, disruption of MHC class I and class II appeared to reverse or delay aging-related thymic atrophy at 12 months. Immunohistochemical analysis of aging-associated alterations in thymic morphology revealed that TCR alphabeta transgenes, CD4 disruption, and MHC class II disruption all reduced or eliminated these changes. All strains examined at 12 months showed alterations in the distribution of immature thymocyte populations relative to young controls. These results show that aging-associated thymic structural alterations, size reductions, and thymocyte developmental delays can be separated and are therefore causally unrelated. Furthermore, these results suggest that the T cell repertoire and/or its development play a role in aging-related thymic involution.

Aging↗
PubMed2000

Intestinal manipulation during elective aortic aneurysm surgery leads to portal endotoxaemia and mucosal barrier dysfunction.

OBJECTIVES: to investigate the effect of intestinal manipulation on intestinal permeability and endotoxaemia during elective abdominal aortic aneurysm (AAA) surgery. DESIGN: prospective randomised controlled study. PATIENTS AND METHODS: fourteen patients undergoing elective infrarenal AAA repair were randomised into either the transperitoneal (n=7) or extraperitoneal approach (n=7). Intestinal permeability was measured preoperatively (PO), and at day 1 (D1) and day 3 (D3) after surgery using the lactulose/mannitol absorption test. Portal and systemic blood samples were taken before clamping, at completion of proximal and distal anastomoses and immediately before abdominal wound closure, for endotoxin measurement using the chromogenic limulus amoebocyte lysate assay. RESULTS: intestinal permeability was significantly increased at D1 (0.107+/-0.04 (mean+/-S.E.M.)) in the transperitoneal group compared to the PO level (0.020+/-0.004, p<0.05) and to the extraperitoneal group at D1 (0.020+/-0.004, p<0.05) which showed no change in comparison with the PO level. No correlation was seen between increased intestinal permeability and aortic clamp time, operation time, amount of blood lost or transfused. However, a significantly higher concentration of portal endotoxin was detected intraoperatively in the transperitoneal group of patients in comparison to the extraperitoneal group (p<0.05). There was a significant positive correlation between portal endotoxaemia and intestinal permeability (r(s)=0.955 p=0.001). CONCLUSION: an increase in intestinal permeability and a greater degree of portal endotoxaemia are observed during transperitoneal approach to the aorta. This suggests that intestinal manipulation may impair gut mucosal barrier function and contribute to the systemic inflammatory response seen in AAA surgery.

Aged↗
PubMed1999

Persistence of memory CD8 T cells in MHC class I-deficient mice.

An understanding of how T cell memory is maintained is crucial for the rational design of vaccines. Memory T cells were shown to persist indefinitely in major histocompatibility complex (MHC) class I-deficient mice and retained the ability to make rapid cytokine responses upon reencounter with antigen. In addition, memory CD8 T cells, unlike naïve cells, divided without MHC-T cell receptor interactions. This "homeostatic" proliferation is likely to be important in maintaining memory T cell numbers in the periphery. Thus, after naïve CD8 T cells differentiate into memory cells, they evolve an MHC class I-independent "life-style" and do not require further stimulation with specific or cross-reactive antigen for their maintenance.

Adoptive Transfer↗
PubMed1997

Delayed presentation of porta hepatis injury following blunt abdominal trauma.

A 73 year old lady developed abdominal pain, anaemia and obstructive jaundice 18 days after a road traffic accident. The jaundice was due to compression of the biliary confluence by a haematoma which was caused by a laceration of the left portal vein. The portal vein was repaired (lateral venorrhaphy) and post-operative recovery was uncomplicated. Porta hepatis injuries are difficult to diagnose and delayed presentation is not uncommon. Significant morbidity and mortality may ensue if aggressive management is not adopted.

Abdominal Injuries↗