Clinical use of computational modeling for surgical planning of arteriovenous fistula for hemodialysis

BACKGROUND

Autogenous arteriovenous fistula (AVF) is the best vascular access (VA) for hemodialysis, but its creation is still a critical procedure. Physical examination, vascular mapping and doppler ultrasound (DUS) evaluation are recommended for AVF planning, but they can not provide direct indication on AVF outcome. We recently developed and validated in a clinical trial a patient-specific computational model to predict pre-operatively the blood flow volume (BFV) in AVF for different surgical configuration on the basis of demographic, clinical and DUS data. In the present investigation we tested power of prediction and usability of the computational model in routine clinical setting.

METHODS

We developed a web-based system (AVF.SIM) that integrates the computational model in a single procedure, including data collection and transfer, simulation management and data storage. A usability test on observational data was designed to compare predicted vs. measured BFV and evaluate the acceptance of the system in the clinical setting. Six Italian nephrology units were involved in the evaluation for a 6-month period that included all incident dialysis patients with indication for AVF surgery.

RESULTS

Out of the 74 patients, complete data from 60 patients were included in the final dataset. Predicted brachial BFV at 40 days after surgery showed a good correlation with measured values (in average 787 ± 306 vs. 751 ± 267 mL/min, R = 0.81, p < 0.001). For distal AVFs the mean difference (±SD) between predicted vs. measured BFV was -2.0 ± 20.9%, with 50% of predicted values in the range of 86-121% of measured BFV. Feedbacks provided by clinicians indicate that AVF.SIM is easy to use and well accepted in clinical routine, with limited additional workload.

CONCLUSIONS

Clinical use of computational modeling for AVF surgical planning can help the surgeon to select the best surgical strategy, reducing AVF early failures and complications. This approach allows individualization of VA care, with the aim to reduce the costs associated with VA dysfunction, and to improve AVF clinical outcome.

The impact of haemodialysis arteriovenous fistula on haemodynamic parameters of the cardiovascular system

BACKGROUND

Satisfactory vascular access flow (Qa) of an arteriovenous fistula (AVF) is necessary for haemodialysis (HD) adequacy. The aim of the present study was to further our understanding of haemodynamic modifications of the cardiovascular system of HD patients associated with an AVF. The main objective was to calculate using real data in what way an AVF influences the load of the left ventricle (LLV).

METHODS

All HD patients treated in our dialysis unit and bearing an AVF were enrolled into the present observational cross-sectional study. Fifty-six patients bore a lower arm AVF and 30 an upper arm AVF. Qa and cardiac output (CO) were measured by means of the ultrasound dilution Transonic Hemodialysis Monitor HD02. Mean arterial pressure (MAP) was calculated; total peripheral vascular resistance (TPVR) was calculated as MAP/CO; resistance of AVF (AR) and systemic vascular resistance (SVR) are connected in parallel and were respectively calculated as AR = MAP/Qa and SVR = MAP/(CO - Qa). LLV was calculated on the principle of a simple physical model: LLV (watt) = TPVR·CO(2). The latter was computationally divided into the part spent to run Qa through the AVF (LLVAVF) and that part ensuring the flow (CO - Qa) through the vascular system. The data from the 86 AVFs were analysed by categorizing them into lower and upper arm AVFs.

RESULTS

Mean Qa, CO, MAP, TPVR, LLV and LLVAVF of the 86 AVFs were, respectively, 1.3 (0.6 SD) L/min, 6.3 (1.3) L/min, 92.7 (13.9) mmHg, 14.9 (3.9) mmHg·min/L, 1.3 (0.6) watt and 19.7 (3.1)% of LLV. A statistically significant increase of Qa, CO, LLV and LLVAVF and a statistically significant decrease of TPVR, AR and SVR of upper arm AVFs compared with lower arm AVFs was shown. A third-order polynomial regression model best fitted the relationship between Qa and LLV for the entire cohort (R (2) = 0.546; P < 0.0001) and for both lower (R (2) = 0.181; P < 0.01) and upper arm AVFs (R (2) = 0.663; P < 0.0001). LLVAVF calculated as % of LLV rose with increasing Qa according to a quadratic polynomial regression model, but only in lower arm AVFs. On the contrary, no statistically significant relationship was found between the two parameters in upper arm AVFs, even if mean LLVAVF was statistically significantly higher in upper arm AVFs (P < 0.0001).

CONCLUSIONS

Our observational cross-sectional study describes statistically significant haemodynamic modifications of the CV system associated to an AVF. Moreover, a quadratic polynomial regression model best fits the relationship between LLVAVF and Qa, but only in lower arm AVFs.

Impact of hyperhydration on the mortality risk in critically ill patients admitted in intensive care units: comparison between bioelectrical impedance vector analysis and cumulative fluid balance recording

BACKGROUND

Studies have demonstrated a positive correlation between fluid overload (FO) and adverse outcomes in critically ill patients. The present study aims at defining the impact of hyperhydration on the Intensive Care Unit (ICU) mortality risk, comparing Bioelectrical Impedance Vector Analysis (BIVA) assessment with cumulative fluid balance (CFB) recording.

METHODS

We performed a prospective, dual-centre, clinician-blinded, observational study of consecutive patients admitted to ICU with an expected length of ICU stay of at least 72 hours. During observational period (72-120 hours), CFB was recorded and cumulative FO was calculated. At the admission and daily during the observational period, BIVA was performed. We considered FO between 5% and 9.99% as moderate and a FO ≥ 10% as severe. According to BIVA hydration scale of lean body mass, patients were classified as normohydrated (>72.7%-74.3%), mild (>71%-72.7%), moderate (>69%-71%) and severe (≤ 69%) dehydrated and mild (>74.3%-81%), moderate (>81%-87%) and severe (>87%) hyperhydrated. Two multivariate logistic regression models were performed: the ICU mortality was the response variable, while the predictor variables were hyperhydration, measured by BIVA (BIVA model), and FO (FO model). A p-value <0.05 was considered to indicate statistical significance.

RESULTS

One hundred and twenty-five patients were enrolled (mean age 64.8 ± 16.0 years, 65.6% male). Five hundred and fifteen BIVA measurements were performed. The mean CFB recorded at the end of the observational period was 2.7 ± 4.1 L, while the maximum hydration of lean body mass estimated by BIVA was 83.67 ± 6.39%. Severe hyperhydration measured by BIVA was the only variable found to be significantly associated with ICU mortality (OR 22.91; 95% CI 2.38-220.07; p < 0.01).

CONCLUSIONS

The hydration status measured by BIVA seems to predict mortality risk in ICU patients better than the conventional method of fluid balance recording. Moreover, it appears to be safe, easy to use and adequate for bedside evaluation. Randomized clinical trials with an adequate sample size are needed to validate the diagnostic properties of BIVA in the goal-directed fluid management of critically ill patients in ICU.

[An unusual cause of ureteral obstruction in kidney transplant]

Inguinal herniation of the ureter in a kidney transplantation is a rare cause of late distal ureteral obstruction. Herniation is usually secondary to the implant of a long redundant ureter and to its course on the spermatic cord. This clinical condition can worsen graft function in the presence of ipsilateral hydroureteronephrosis. In this review, we describe the case of an asymptomatic 51-year-old man with a history of right iliac renal allotransplantation 12 years before. Kidney ultrasound showed moderate hydroureteronephrosis and ureteral kneeling at the upper third of the inguinal canal. The patient presented a mild increase in serum creatinine; physical examination revealed an ipsilateral inguinal hernia. A CT scan of the abdomen with no contrast medium confirmed middle-distal ureteral kneeling engaging in the sac of the right inguinal hernia. The patient underwent surgical hernia repair with no complications and his renal function recovered completely.

Vitamin D status and cholecalciferol supplementation in chronic kidney disease patients: an Italian cohort report

This study investigated the factors associated with hypovitaminosis D, in a cohort of 405 prevalent patients with chronic kidney disease (CKD) stages 2–4, living in Italy and followed-up in tertiary care. The effect of cholecalciferol 10,000 IU once-a-week for 12 months was evaluated in a subgroup of 100 consecutive patients with hypovitaminosis D. Vitamin D deficiency was observed in 269 patients (66.4%) whereas vitamin D insufficiency was found in 67 patients (16.5%). In diabetic patients, 25-hydroxyvitamin D deficiency was detected in 80% of cases. In patients older than 65 years, the prevalence of hypovitaminosis D was 89%. In the univariate analysis, 25-hydroxyvitamin D was negatively related to age, parathyroid hormone (PTH), proteinuria, and Charlson index, while a positive relationship has emerged with hemoglobin level. On multiple regression analysis, only age and PTH levels were independently associated with 25-hydroxyvitamin D levels. No relationship emerged between vitamin D deficiency and renal function. Serum levels of 25-hydroxyvitamin D or prevalence of hypovitaminosis D did not differ between patients on a free-choice diet and on a renal diet, including low-protein, low-phosphorus regimens. Twelve-month oral cholecalciferol administration increased 25-hydroxyvitamin D and reduced PTH serum levels. In summary, hypovitaminosis D is very prevalent in CKD patients (83%) in Italy, and it is similar to other locations. PTH serum levels and age, but not renal function, are the major correlates of hypovitaminosis D. Implementation of renal diets is not associated with higher risk of vitamin D depletion. Oral cholecalciferol administration increased 25-hydroxyvitamin D and mildly reduced PTH serum levels. Oral cholecalciferol supplementation should be recommended as a regular practice in CKD patients, also when serum 25-hydroxyvitamin D determination is not available or feasible.

[An unusual cause of acute pyelonephritis: the retrocaval ureter]

Retrocaval ureter is a rare congenital malformation in which the proximal right ureter courses toward the midline on the posterior aspect of the inferior vena cava before emerging medial and anterior to this structure and then descending into the pelvis. This anatomical anomaly may be asymptomatic or manifest clinically, usually starting from the fourth decade of life, with flank pain, pyelonephritis, gross hematuria or other rarer signs. We describe the case of a young woman being hospitalized because of acute pyelonephritis; she had previously complained of flank pain associated with episodes of high fever. Computed tomography of the abdomen identified the malformation. The patient underwent surgical correction by laparoscopy and, at one year of follow-up, did not show any further clinical problem.

Cisplatin-based chemoradiation plus cetuximab in locally advanced head and neck cancer: a phase II clinical study

BACKGROUND

Intensification of chemoradiation for advanced head and neck squamous cell carcinoma (HNSCC) is unlikely due to toxicity. Cetuximab combined either with radiotherapy or with chemotherapy showed favourable toxic profile with positive results in both combinations. Therefore, cetuximab could intensify chemoradiation without worsening toxicity. We conducted a phase II study of chemoradiation and cetuximab.

PATIENTS AND METHODS

Eligible patients had stage III-IV M0 HNSCC. Treatment consisted of three cycles of cisplatin (20 mg/m(2)/day × 5 days) and fluorouracil (200 mg/m(2)/day × 5 days) rapidly alternated to three split courses of radiotherapy up to 70 Gy and concurrent weekly cetuximab. The primary end point of the study was complete response (CR) rate. Secondary end points were toxicity, progression-free survival (PFS) and overall survival (OS).

RESULTS

Fourty-five patients were enrolled: median age was 56 years, 38 had stage IV disease and 40 nodal involvement. CR occurred in 32 patients (71%). PFS and OS was 21+ months and 32.6+, respectively. Acute grade 3-4 toxic effects were in the expected range, but grade 3 radiodermatitis occurred in 33 patients.

CONCLUSIONS

The combination of cetuximab, cisplatin, fluorouracil and radiotherapy leads to a very high proportion of CR and it is feasible with toxic effects similar to those expected by radiochemotherapy. The only unexpected toxicity was skin toxicity: grade 3 radiodermatitis occurred in 73% of the patients.

Cetuximab (C-mab) and chemo-radiation (CT-RT) for loco-regional advanced squamous cell carcinoma of the head and neck (HNC): A phase II study

6043

Background: C-mab is a monoclonal antibody targeting EGFR. C-mab combined with radiotherapy (RT) improved loco- regional control and overall survival over RT alone in HNC pts (Bonner 2006). Prior data of C-mab and CT-RT (Pfister 2006) were encouraging but the trial was stopped due to an excess of severe toxicities, suggesting the need for a less toxic scheduling. For these reasons we evaluate the safety and activity of C-mab combined with alternating CT-RT in HNC pts. Methods: The primary end-point is C.R. rate. The optimal two stage design was used: the calculated sample size is 45 pts. Eligible pts have locally advanced, measurable, untreated, stage III/IV HNC (excluding nasopharynx). Chemotherapy (CT) consists of Cis-PT 20 mg/m2/day and bolus 5Fu 200 mg/m2/day from day 1 to 5, repeated on days 22 and 43. RT, 2 Gy/day, 5 days a week, is given in the pauses between the chemotherapy courses and after the last CT week, up to a total dose of 70 Gy. Results: From 10/2005 to 12/2006 24 pts were enrolled: median age 59 (49–75); median ECOG P.S. 0 (0–1); Stage IV 73%; N1–3 86%; EGFR >80% cells: 55%; EGFR 3+: 91%; most pts had hypopharynx cancer, only 1 had oral cavity tumor. Toxicity is evaluable on 20 pts (4 ongoing). Grade 3–4 toxicities included febrile neutropenia (20%), diarrhea (20%), hypomagnesaemia (10%), mucositis (60%). Unexpected skin toxicity, starting as desquamating moist dermatitis and confined at the irradiated field, occurred in 18/20 pts, usually during the second part of the treatment. Acute colon diverticulitis with perforation (1 pt), gastric perforation (1 pt), fatal myocardial infarction (1 pt) and arterial thrombosis (1 pt) also occurred. Responses, evaluated 3 months after the treatment, are available for the first 16 pts. Objective responses were observed in all them (11 CR + 5 PR). Two PRs were then rendered disease free with salvage surgery. At a maximum follow-up of 15 months, 16/20 pts are alive and 16/20 progression free. Conclusions: This trial showed a skin toxicity not previously reported in other experiences of C-mab combined with RT or CT-RT. Preliminary activity data seems to confirm the Pfister experience.

No significant financial relationships to disclose.

Low-dose gemcitabine and radiation alternated to cisplatin/5fu in stage IV squamous cell carcinoma of the head and neck (HN- SCC): A phase II trial

6062

Background: At the National Institute for Cancer Research of Genoa, Italy, we conducted two consecutive phase II single-institution trials testing the addition of gemcitabine into an alternating chemo-radiation (CT/RT) regimen that is considered standard of care in our Institute for patients (pts) with loco-regional advanced HN-SCC (NEJM, 327:1115,1992). In the former trial (ALT-G trial; 47 pts) high dose gemcitabine was administered with cisplatin and RT (Annals of Oncology, 15:646,2004). Methods: In the present trial (ALT-g trial) 3 courses of cisplatin, 20 mg/m2/day and 5-fluorouracil, 200 mg/m2/day, days 1–5 (weeks 1, 4, 7) alternated to 3 courses of standard RT (weeks 2–3, 5–6, 8–9) up to 60 Gy and gemcitabine, 40 mg/m2 on monday of each week of RT, were administered to 47 pts with stage IV (42 pts) or relapsed after surgery (5 pts), unresectable SCC of the oral cavity (11 pts), oropharynx (11 pts) hypopharynx-larynx (24 pts). None had previously received CT or RT. Results: Seven pts (15%) did not complete the planned treatment. Four of them died due to pulmonary embolism (2 pts), fulminant pneumonia (1 pt) or uncertain causes (1 pt). Main grade 3–4 other than local toxicities were: neutropenia (11%), neutropenia with fever (6%), thrombocytopenia (30%), anemia (17% grade 3). 27 pts reached a CR (57%). 7 PRs were rendered disease-free by surgery mainly on the neck (final CR rate: 72%). At a median follow-up of 37 months, 3-yr results and acute local toxicity are compared with those from ALT-G trial and from our data-base of pts treated with alternating cisplatin/5-FU and RT without gemcitabine (ALT): Conclusions: In conclusion, the addition of low-dose gemcitabine into a consolidated cisplatin/5FU and RT alternating program may improve the outcomes with an acceptable increase in acute severe mucositis.

No significant financial relationships to disclose.

[Table: see text]

Induction chemotherapy followed by alternating chemo-radiotherapy in advanced undifferentiated nasopharyngeal carcinoma (UNPC)

15508

Background: Concomitant chemo-radiotherapy is the standard treatment for advanced UNPC. Induction chemotherapy may improve the results further by enhancing both locoregional and distant control. Methods: Fifty patients with previously untreated, locoregionally advanced UNPC were initially treated with 3 courses of epidoxorubicin, 90 mg/mq, day 1 and cisplatin, 40 mg/mq, days 1 and 2, every 3 weeks. After a radiological and clinical response assessment patients underwent 3 courses of cisplatin, 20 mg/mq/day, days 1–4 and fluorouracil, 200 mg/mq/day, days 1–4, i.v. bolus, (weeks 1,4,7) alternated to 3 splits of radiation (week 2–3, 5–6, 8–9-10), with a standard fractionation, up to 70 Gy. Histology was WHO type 1 in 1 pt (2%), WHO type 2 in 10 pt (20%), WHO type 3 in 39 pts (78%). All patients had stage IV disease (UICC 1992). Results: All the patients are evaluable for toxicity and response. All but one received 3 cycles of induction chemotherapy. Toxicities from induction chemoyherapy were: 2% grade 3 or 4 mucositis, 22% grade 3 or 4 nausea/vomiting, 6% grade 3 or 4 haematological toxicity and one episode of febrile neutropenia. At the end of induction phase 12% of CRs, 84% of PRs and 4% of SD were recorded. All patients but two had the planned number of chemotherapy courses in the alternating phase and all but one received the planned radiation dose. Toxicities from alternating chemo-radiotherapy were: 28% grade 3 or 4 mucositis, 8% grade 3 or 4 nausea/vomiting, 24% grade 3 or 4 haematological toxicity with no episodes of febrile neutropenia. At the final response evaluation 86% of CRs and 14% of PRs were observed. At a median follow up of 39 months, 14% of patients had locoregional failure, 20% had distant failure and 2% both. The 4-year actuarial progression free survival and overall survival rates were 71% and 81%. Conclusions: Treatment of locoregionally advanced UNPC with induction chemotherapy followed by alternating chemo-radiotherapy is feasible and patients’ compliance is optimal. 4-year outcomes seems better than those reported with concomitant chemo-radiotherapy alone.

No significant financial relationships to disclose.