Paul Tam

The Scarborough Hospital, Pickering, Ontario, Canada

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Publications (41)69.38 Total impact

  • Transplantation 07/2013; 96(1):e1-e2. · 3.78 Impact Factor
  • International Journal of Endocrinology 01/2013; 2013:164103. · 2.52 Impact Factor
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    ABSTRACT: Purpose: To assess the technical success rate and safety of radiofrequency perforation guidewire (RF) technology for the recanalization of refractory chronic central venous occlusions in symptomatic hemodialysis patients with failed conventional endovascular methods. Methods: This single center retrospective cohort of hemodialysis patients comprised of six men (mean age 67 years, range 55 to 80) with autogenous fistulae, who had already undergone failed conventional endovascular methods. These patients underwent the RF perforation technique from December 2006 to January 2010. Results: Three patients were successfully treated using the RF perforation technique, after which they had PTFE stent grafts placed at the site of occlusion. There was no recurrence of clinical symptoms. In the remaining three patients, the procedure was terminated after multiple unsuccessful attempts. There were no complications. Conclusions: The RF perforation technique is a potential alternative technology for recanalization of refractory chronic central venous occlusions in hemodialysis patients in the setting of failed conventional endovascular recanalization techniques.
    The journal of vascular access 07/2012; · 0.97 Impact Factor
  • Int J Nephrol. 01/2012;
  • International Urology and Nephrology 10/2011; 44(5):1591-2. · 1.33 Impact Factor
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    ABSTRACT: Despite the risk of aluminum (Al) toxicity in dialysis patients, little is known about its toxicokinetics (TK) in this population. A national contamination of dialysate solutions with Al provided the opportunity to study Al TK in peritoneal dialysis (PD) patients and to better understand the influence of covariates on its disposition. Al levels in serum and dialysate as well as other laboratory values were collected prospectively from 83 PD patients after correction of Al contamination. Population TK analyses were conducted with NONMEM VI using standard model discrimination criteria. Covariate analyses were also performed using stepwise forward regression followed by backward deletion. After correction of Al exposure, serum levels declined in a biphasic manner, which was captured by the TK model. The TK of Al were best described by a 2-compartment model with linear elimination. Total creatinine clearance was a significant covariate for total clearance (CL). Mean parameter estimates for volume of central compartment (V1), CL, volume of peripheral compartment (V2), volume of distribution at steady-state (Vss), and intercompartmental clearance (Q) were 168 L, 8.99 L/day, 12 000 L, 12 168 L, and 4.93 L/day, respectively. Inter-individual variability for CL and V2 were 22.6 and 51.1%, respectively. Al distributional half-life was 8.5 days, while the terminal elimination half-life was 7.2 years. This model confirms that the large Vss reflects the widespread distribution of Al in bone, lungs, liver, and other tissues. This study describes the first population Al TK model in a large group of PD patients, which includes a covariate effect. The model confirms the extensive half-life and tissue distribution of Al in a dialysis-dependent population.
    Clinical Toxicology 08/2011; 49(7):659-63. · 2.59 Impact Factor
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    ABSTRACT: Preservation of the mesothelial cells (MCs) is crucial for longevity of the peritoneal dialysis membrane. Glucose accelerates aging of MC and we tested whether N-acetylglucosamine (NAG) has an identical effect. Replicative aging of MCs was studied during 10 passages performed every three days in cells cultured in standard medium or in medium supplemented with Glucose 30 mmol/L or NAG 30 mmol/L. Changes in population doubling time and ß-galactosidase activity were used as an index of aging and compared with other cellular parameters. Repeated passages of MC cause their aging, as reflected by prolongation of the population doubling time, increased ß-galactosidase activity, oxidative stress and release of cytokines. Healing of injured mesothelial monolayer is impaired in senescent cells. Glucose accelerates in vitro aging of MC, whereas NAG does not cause this effect. Replacement of glucose with NAG in the dialysis fluid can slow down aging of MC.
    The International journal of artificial organs 06/2011; 34(6):489-94. · 1.76 Impact Factor
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    ABSTRACT: Chronic kidney disease (CKD) is staged by glomerular filtration rate (GFR). CKD stages sometimes vary between routine office visits, and it is unknown if this impacts renal and patient survival separately from a cross-sectional CKD stage value. We quantified and categorized CKD stage variability in a large group of outpatients and correlated this with clinical and demographic features and with renal and patient survival. All estimated GFRs were staged in the first observation period. CKD stages were then categorized as static, improving, worsening, or fluctuating. Logistic regression analysis was performed to identify clinical variables associated with CKD stage variability. Death and dialysis progression rates were then collected and analyzed using Cox proportional regression. During a 1.1-year observation period, 1,262 patients (mean age 71.25 years) had a mean 5 eGFR's. CKD stages were static in 60.4%, worsened in 14.4%, improved in 7.4%, and fluctuated in 17.2% of patients. Secondary analysis revealed heavy proteinuria and East Asian ethnicity to be negatively, and diabetes mellitus and previous acute kidney injury to be positively associated with improving CKD stages. Cox proportional regression of 902 patients analyzed 2.3 years later revealed a negative association with improving CKD stage and subsequent need for dialysis. CKD stage changed in 40% of 1,262 elderly patients when determined 5 times in just over 1 year. Improving CKD stage was the only variability pattern significantly associated with any of the clinical outcomes when assessed 2.3 years later, being unlikely to be linked with subsequent need for dialysis.
    International Urology and Nephrology 03/2011; 44(5):1461-6. · 1.33 Impact Factor
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    International journal of nephrology. 01/2011; 2011:218974.
  • Journal of Vascular and Interventional Radiology - J VASC INTERVEN RADIOL. 01/2011; 22(3).
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    ABSTRACT: To assess the safety and effectiveness of a polytetrafluoroethylene (PTFE) encapsulated nitinol stents (Bard Peripheral Vascular, Tempe, AZ) for treatment of hemodialysis-related central venous occlusions. Study design was a single-center nonrandomized retrospective cohort of patients from May 2004 to August 2009 for a total of 64 months. There were 14 patients (mean age 60 years, range 50-83 years; 13 male, 1 female). All patients had autogenous fistulas. All 14 patients had central venous occlusions and presented with clinical symptoms of the following: extremity swelling (14%, 2 of 14), extremity and face swelling (72%, 10 of 14), and face swelling/edema (14%, 2 of 14). There was evidence of access dysfunction with decreased access flow in 36% (5 of 14) patients. There were prior interventions or previous line placement at the site of the central venous lesion in all 14 patients. Results were assessed by recurrence of clinical symptoms and function of the access circuit (National Kidney Foundation recommended criteria). Sixteen consecutive straight stent grafts were implanted in 14 patients. Average treated lesion length was 5.0 cm (range, 0.9-7 cm). All 14 patients had complete central venous occlusion (100% stenosis). The central venous occlusions were located as follows: right subclavian and brachiocephalic vein (21%, 3 of 14), right brachiocephalic vein (36%, 5 of 14), left brachiocephalic vein (36%, 5 of 14), and bilateral brachiocephalic vein (7%, 1 of 14). A total of 16 PTFE stent grafts were placed. Ten- or 12-mm-diameter PTFE stent grafts were placed. The average stent length was 6.1 cm (range, 4-8 cm). Technical (deployment), anatomic (<30% residual stenosis), clinical (resolution of symptoms), and hemodynamic (resolution of access dysfunction) success were 100%. At 3, 6, and 9 months, primary patency of the treated area and access circuit were 100% (14 of 14). This PTFE encapsulated stent graft demonstrates encouraging intermediate-term patency results for central vein occlusions. Further prospective studies with long-term assessment and larger patient populations will be required.
    CardioVascular and Interventional Radiology 11/2010; 34(5):949-57. · 2.09 Impact Factor
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    ABSTRACT: The aim of this study was to examine the accuracy of the Modification of Diet in Renal Disease (MDRD) equation and the Cockcroft and Gault formula (CCrCG) in predicting total creatinine clearance achieved by residual renal function plus peritoneal dialysis in patients on chronic peritoneal dialysis. Total creatinine clearance was defined as peritoneal creatinine clearance (PCcr) plus the average of urine urea and creatinine clearances (cGFR). Correlation analysis and Bland-Altman plot were used to establish the degree of correlation and agreement between the estimations of creatinine clearance achieved by PCcr and the average of cGFR and estimated creatinine clearance based on serum creatinine by using either MDRD equation or the Cockcroft and Gault formula. In one hundred fifty-six measurements, mean clearances by [cGFR + PCcr], CCrCG and MDRD were: 7.9 ± 3.1, 10.6 ± 5.2 and 8.5 ± 4.9 ml/min/1.73 m(2), respectively. There was a good correlation between [cGFR + PCcr] and MDRD (r = 0.776, P < 0.05) and [cGFR + PCcr] and CCrCG (r = 0.735, P < 0.05). The mean MDRD was not significantly different from the mean clearance by [cGFR + PCcr] (difference 0.4 ± 2.9 ml/min/1.73 m(2), agreement limit -5.4-6.3 ml/min/1.73 m(2)). The CCrCG formula gave a larger difference from the mean [cGFR + PCcr] (2.8 ± 10.5 ml/min/1.73 m(2)) and a much wider agreement limit (-3.7-9.3 ml/min/1.73 m(2)). In male patients, MDRD formula provided an estimate of clearance that was similar to the mean [cGFR + PCcr] (7.9 ± 3.8 ml/min/1.73 m(2) vs. 8.2 ± 3.2 ml/min/1.73 m(2), respectively; difference 0.10 ± 1.9 ml/min/1.73 m(2), limits of agreement -3.9-3.7 ml/min/1.73 m(2)). By contrast, in female patients, the MDRD equation significantly overestimated the clearance (difference between mean estimated and mean measured clearance 1.4 ± 4.1 ml/min/1.73 m(2), limits of agreement -6.6-9.5 ml/min/1.73 m(2) P < 0.05). In conclusion, the GFR estimated by MDRD formula is similar to [cGFR + PCcr] especially in males. GFR by the CCrCG formula tended to overestimate the highest values of [cGFR + PCcr].
    International Urology and Nephrology 04/2010; 42(4):1085-92. · 1.33 Impact Factor
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    ABSTRACT: The mean age of patients with end-stage renal disease increases steadily. The elderly on dialysis have significant comorbidity and require extra attention to meet their dialysis, dietary, and social needs, and some may need to be treated at a long-term care facility such as a nursing home (NH). Providing dialysis and caring for elderly patients in a nursing home (NH) presents a number of challenges. Few data are available in the literature about elderly patients on peritoneal dialysis (PD) in an NH. This paper describes our experience of starting and maintaining a peritoneal dialysis program in three community-based nursing homes. RESULTS: During the period 2004-2008, after the nursing home personnel had received appropriate training, we established a PD program in three community-based nursing homes and admitted 38 patients on peritoneal dialysis. We educated 112 NH staff over the three-year period. Mean age of the patients at entry was 77.3 + or - 8.5(18.4%) were male. The main causes of end-stage renal disease were diabetes mellitus (DM) 21 (55.8%) and hypertension 13 (34.2%). Comorbid conditions included DM (27, 71.1%), hypertension (26, 68.4%), coronary artery disease (18.5%), chronic heart failure (11, 28.9%), cerebrovascular event (12, 31.6%), and cancer(3, 7.9%). The average total time on chronic peritoneal dialysis was 36.5 + or - 29.8 months, (median 31, range: 1-110 months) of which the average time in the NH program, as of the time of this report, was 18.4 + or - 13.1 months (median 15.5, range: 1-45 months). During the study period, 16 (42.1%) of the patients died, 2 (5.3%) transferred to HD, 2 (5.3%) stopped treatment, and 18 (47.4%) are still in the program. Actuarial patient survival from entry into the NH program was 89.5% at six months, 60.5% at 12 months, 39.5% at 24 months and 13.2% at 36 months. Patient survival from initiation of chronic dialysis was 89.5% at six months, 76.3% at 12 months, 63.1% at 24 months, and 39.5% at 36 months. We observed 28 episodes of peritonitis with a rate of one episode every 40.3 treatment-months. Two PD catheters had to be replaced, giving a rate of one in every 362.5 patient months. CONCLUSION: Our results with elderly patients in a nursing home show an excellent patient and technique survival and a low peritonitis rate. With appropriate training of the NH nursing staff, peritoneal dialysis could be performed successfully in these nursing homes. Successful peritoneal dialysis in a nursing home requires a close collaboration between the nursing home staff and PD dialysis unit.
    International Urology and Nephrology 02/2010; 42(2):545-51. · 1.33 Impact Factor
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    ABSTRACT: To compare the immediate results of ultrahigh-pressure (UHP) balloons vs. peripheral cutting balloons (PCB) for the treatment of stenoses associated with autogenous fistulas using intra-access blood flow measurements. This prospective randomized study consisted of 22 hemodialysis (HD) patients with autogenous fistulas who had decreased intra-access blood flow (<500 mL/min). All patients underwent a fistulogram and intraprocedural blood flow measurements. Patients were randomized once into two groups; one group undergoing UHP angioplasty and the second group undergoing PCB angioplasty. Randomization occurred once after the diagnostic fistulogram and each patient in each arm only underwent percutaneous transluminal angioplasty with either UHP or PCB. The study cohort consisted of 12 patients in the UHP group and 10 patients in the PCB group. Data collected included fistula anatomy, degree of stenosis, length of stenosis, balloon specifications and residual stenosis. The 22 study patients underwent 35 angioplasty procedures; 23 in the UHP group (12 patients) and 12 in the PCB group (10 patients). The technical success rate was 91%. The pre-intervention mean blood flow was 288 mL/min in the UHP group and 391 mL/min in the PCB group. The post-intervention mean blood flow was 613 mL/min in the UHP group and 606 mL/min in the PCB group. The mean increase in blood flow was 325.8 mL/min in the UHP group and 213 mL/min in the PCB group. This represents a relative mean increase in blood flow of 253% in the UHP group and 85% in the PCB group. An unpaired t-test showed there was no significant difference between the groups with respect to pre-flow, post-flow, and mean and relative mean increase in flow. There were two failures; one in the UHP group and one in the PCB group. There was one minor complication (2.8%) but no major complications. In this small group of HD patients with autogenous fistulas our comparison of UHP to the PCB demonstrated that the immediate results, as determined by measurement of intra-access blood flow, were equivalent. Further long-term follow-up will be required to determine the longevity of these results.
    The journal of vascular access 01/2010; 11(4):303-11. · 0.97 Impact Factor
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    ABSTRACT: We report a patient with multifocal fibrosclerosis presenting as sialadenitis, hepatic fibrosis, and retroperitoneal fibrosis with renal failure. His medical management consisted of prednisone (4 months at 40 mg daily, then tapered down to 5 mg daily for another 14 months) and 18 months of tamoxifen. He responded clinically and radiographically to this regimen, and remains in clinical remission 10 months after discontinuing medical therapy. Subsequent histologic examination of submandibular gland tissue revealed strong staining for IgG4-positive plasma cells. To our knowledge, this is the first case of confirmed multifocal hyper-IgG4 disease to be successfully treated with sequential corticosteroids and tamoxifen.
    Clinical nephrology 11/2009; 72(5):414-7. · 1.29 Impact Factor
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    ABSTRACT: CKD patients referred to a renal management clinic are looked after by a multidisciplinary team whose care may improve outcome and delay the progression of kidney disease. This paper describes our experience and the results obtained in 940 patients with CKD stage 4 and 5 patients from two renal management clinics (RMC). We collected and analyzed the data from 940 patients with CKD stage 4 and 5 at the RMCs of the Toronto General Hospital (TGH), University Health Network and The Scarborough General Hospital (TSH) from January 2000 to November 2007. Inclusion criteria for the study required at least three measurements of serum creatinine over a minimum follow-up of 6 months. We calculated the change of slope of the estimated GFR by linear regression analysis. The slopes were further subdivided into five groups: improved eGFR (eGFR slope >or=+5 ml/min/year); mild improvement (slope >+1 to <+5 ml/min/year); stable (slope <+1 to >-1 ml/min/year); slow progression (i.e., deterioration; slope <-1 to >-5 ml/min/year) and rapid progression (slope >-5 ml/min/year). During a median follow-up of 1.57 year (range 0.5-8.7 year) of stage 4 patients, eGFR improved in 10.6%, showed mild improvement in 24.2%, was stable in 27.5%, showed slow progression in 28.8% and rapid progression in 8.9% of patients. During a median follow-up of 1.4 year (range 0.5-8 year) of CKD stage 5 patients, eGFR improved in only 1.3%, showed mild improvement in 4.3%, remained stable in 35.6%; showed slow progression in 19.7% and rapid progression in 39.1%. Between the two hospitals (TGH and TSH) there was a statistically significant difference in the number of visits per year for CKD stage 4 patients during the first, second and third year. However, the number of visits per year had no effect on the rate of decline. On univariate analysis, factors predicting non-progression in eGFR slope were eGFR at referral, the use of ACE inhibitors-ARBs and absence of cardiovascular disease. However, in logistic multivariate regression analysis, after adjusting for confounding factors only the eGFR at referral and ACE inhibitors-ARBs were independent factors for non-progression in eGFR. A significant percentage of CKD stage 4 patients attending a renal management clinic (RMC) showed non-progression or improvement in their kidney function. Although only few stage 5 CKD patients had improvement in their eGFR, 32% of them maintained their eGFR on conservative treatment for over 2 years delaying the initiation of dialysis.
    International Urology and Nephrology 08/2009; 41(4):977-82. · 1.33 Impact Factor
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    Peritoneal dialysis international: journal of the International Society for Peritoneal Dialysis 01/2009; 29(3):352-5. · 2.21 Impact Factor
  • Journal of Vascular and Interventional Radiology - J VASC INTERVEN RADIOL. 01/2009; 20(2).
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    ABSTRACT: The adverse effects arising from late referral to a nephrologist of patients with chronic kidney disease (CKD) are well known. Retrospectively we examined the initial characteristics of patients referred in various stages of CKD to our nephrology division and tried to identify potential baseline factors associated with subsequent changes in estimated glomerular filtration rate (eGFR). Between September 1997 and June 2006 1,443 patients (909 male, 534 female) with CKD, with eGFRs ranging from 15 to 89 ml/min, were referred to our nephrology division and categorized using the National Kidney Foundation classification for CKD based on eGFR. The slope of eGFR change (ml/min-1/1.73/m2-1/year-1) was determined by linear regression analysis and the patients were divided into five groups: (1) significantly progressive slope (deterioration) (more negative than -5 ml/min/year); (2) mildly progressive slope (>-5 to <or=-1); (3) stable slope (>-1 to <or=+1); (4) mildly improved slope (>+1 to <or=+5), and (5) significantly improved slope (>or=+5). At the first nephrology referral, 5.8% of the patients were on CKD stage 2 (eGFR: 90-60 ml/m), 46.7% on CKD stage 3 (eGFR: 59-30 ml/m), and 47.5% on CKD stage 4 (eGFR: 29-15 ml/m) CKD. Significantly improved slope was detected in 48.2% of CKD stage 2 patients, 29.3% of CKD stage 3 patients, and only 14.7% of CKD stage 4 patients (P<0.05). Being in stage 4 or stage 3 versus being in stage 2 significantly reduced the likelihood of an improved slope in logistic regression analysis whereas age, gender, presence of hypertension, and diabetes mellitus did not reach the level of significance. Referral to a nephrology clinic can lead not only to arrest of progression of CKD but also to regression/improvement. Early referral is a positive predictive factor for improvement in eGFR, which emphasizes the importance of such referral. The previously held idea that, once established, CKD progresses invariably is not valid anymore.
    International Urology and Nephrology 05/2008; 40(3):841-8. · 1.33 Impact Factor
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    ABSTRACT: Hyperphosphatemia is independently associated with an increased risk of death among dialysis patients. In this study, we have assessed the status of phosphate control and its clinical and laboratory associations in a large international group of patients on chronic peritoneal dialysis (PD) treatment. This cross-sectional multicenter study was carried out in 24 centers in three different countries (Canada, Greece, and Turkey) among 530 PD patients (235 women, 295 men) with a mean+/-s.d. age of 55+/-16 years and mean duration of PD of 33+/-25 months. Serum calcium (Ca(2+)), ionized Ca(2+), phosphate, intact parathyroid hormone (iPTH), 25-hydroxy vitamin D(3), 1,25-dihydroxy vitamin D(3), total alkaline phosphatase, and bone alkaline phosphatase concentrations were investigated, along with adequacy parameters such as Kt/V, weekly creatinine clearance, and daily urine output. Mean Kt/V was 2.3+/-0.65, weekly creatinine clearance 78.5+/-76.6 l, and daily urine output 550+/-603 ml day(-1). Fifty-five percent of patients had a urine volume of <400 ml day(-1). Mean serum phosphorus level was 4.9+/-1.3 mg per 100 ml, serum Ca(2+) 9.4+/-1.07 mg per 100 ml, iPTH 267+/-356 pg ml(-1), ionized Ca(2+) 1.08+/-0.32 mg per 100 ml, calcium phosphorus (Ca x P) product 39+/-19 mg(2)dl(-2), 25(OH)D(3) 8.3+/-9.3 ng ml(-1), 1,25(OH)(2)D(3) 9.7+/-6.7 pg ml(-1), total alkaline phosphatase 170+/-178 U l(-1), and bone alkaline phosphatase 71+/-108 U l(-1). While 14% of patients were hypophosphatemic, with a serum phosphorus level lower than 3.5 mg per 100 ml, most patients (307 patients, 58%) had a serum phosphate level between 3.5 and 5.5 mg per 100 ml. Serum phosphorus level was 5.5 mg per 100 ml or greater in 28% (149) of patients. Serum Ca(2+) level was > or =9.5 mg per 100 ml in 250 patients (49%), between 8.5 and 9.5 mg per 100 ml in 214 patients (40%), and lower than 8.5 mg per 100 ml in 66 patients (12%). Ca x P product was >55 mg(2)dl(-2) in 136 patients (26%) and lower than 55 mg(2)dl(-2) in 394 patients (74%). Serum phosphorus levels were positively correlated with serum albumin (P<0.027) and iPTH (P=0.001), and negatively correlated with age (P<0.033). Serum phosphorus was also statistically different (P = 0.013) in the older age group (>65 years) compared to younger patients; mean levels were 5.1+/-1.4 and 4.5+/-1.1 mg per 100 ml, respectively, in the two groups. In our study, among 530 PD patients, accepted uremic-normal limits of serum phosphorus control was achieved in 58%, Ca x P in 73%, serum Ca(2+) in 53%, and iPTH levels in 24% of subjects. Our results show that chronic PD, when combined with dietary measures and use of phosphate binders, is associated with satisfactory serum phosphorus control in the majority of patients.
    Kidney international. Supplement 04/2008;

Publication Stats

190 Citations
69.38 Total Impact Points

Institutions

  • 2006–2012
    • The Scarborough Hospital
      Pickering, Ontario, Canada
  • 2006–2011
    • Inonu University
      Malatia, Malatya, Turkey
  • 2009
    • Peking University Third Hospital
      Peping, Beijing, China
  • 2008
    • Akdeniz University
      Satalia, Antalya, Turkey
  • 2005
    • University of Toronto
      • Division of Neurology
      Toronto, Ontario, Canada
  • 2004
    • Democritus University of Thrace
      Komotina, East Macedonia and Thrace, Greece
  • 2001
    • Toronto Western Hospital
      Toronto, Ontario, Canada