Predictive value of Bispectral Index (BIS) in emergency neurosurgical patients: Loss of BIS reactivity to propofol predicts poor functional outcomes.

AIM: In emergency neurosurgical patients, evaluation with Glasgow Coma Scale (GCS) alone immediately after stopping sedation post-operatively might not differentiate those with good recovery from those with poor outcomes at 3 months. This study aimed to evaluate the prognostic value of measuring the Bispectral Index (BIS) and the correlation to propofol dosage during the use of sedation in the early post-operative period. METHODS: This is a prospective study on consecutive post-operative neurosurgical patients admitted to the neurosurgical ICU on propofol sedation. The primary outcome was the correlation between early post-operative BIS and the Propofol dosage with the modified Rankin scale (mRS) at 3 months. Secondary outcomes included the post-operative propofol requirement in patients with good functional outcomes (mRS 0-3) versus poor functional outcomes (mRS 4-6) at 3 months. RESULTS: In total, 728 BIS readings were collected from twenty-four patients for analysis. The BIS readings were significantly correlated to the propofol dosage in patients with good function outcomes at 3 months (p < 0.0001). BIS readings in patients with no associations to changes in propofol dosage during their ICU stay had poor outcomes (mRS 4-6) at 3 months (r = -0.0407). For patients with good functional outcomes at 3 months, a significantly higher propofol dosage was used for deep sedation (BIS 40 - 60) during the post-operative period (p < 0.001). CONCLUSION: For emergency neurosurgical patients whose BIS readings had lost correlation to the propofol dosage upon recovery, their functional outcomes at 3 months were poor. For those with good functional outcomes at 3 months, a significantly higher propofol dosage was required for deep sedation during their ICU stay. Patients with preserved correlation of BIS readings to changes in propofol dosages during the early post-operative period were associated with good functional outcomes at 3 months.

Surgical revascularization for moyamoya angiopathy: Clinical and radiological outcomes of direct and indirect bypasses in 86 affected hemispheres.

Moyamoya is a progressive cerebral angiopathy that entails a formidable natural history of repeated ischemic or haemorrhagic insults if not intervened. The potential advantages of direct/combined bypass can be harvested only if they are not outweighed by perioperative morbidity. Direct bypasses for the paediatric group have been less utilized because of small vessel calibres and an inherently more robust angioplasticity. This study was undertaken to examine the clinical and perfusion imaging outcomes of operated moyamoya disease or syndrome patients in Hong Kong's Southeast Asian population. Comparison was made between direct/combined and indirect bypass cohorts. Subgroup analysis of the paediatric cohort was conducted to determine outcomes of a direct-bypass-first strategy. From November 2000 to September 2020, 86 hemispheres underwent revascularization at a tertiary neurosurgical unit with a mean clinical follow-up time of 70.0 months. 70.9% of the procedures involved direct bypasses. Direct/combined revascularization demonstrated superiority in restoring adequate cerebrovascular reserve capacity (CVRC) (63.2% vs 27.3%, p = 0.015), and freedom from transient ischemic attacks in the first 5 years post-operation by Kaplan-Meier plot with log-rank test (p = 0.038). Follow-up imaging revealed 96.5% of the bypass grafts remained patent. Direct/combined procedures significantly predicted restoration of adequate CVRC on follow-up perfusions scans by binary logistic regression (OR 4.57, p = 0.009). Compared to the adult cohort, direct bypasses in children carried no excessive perioperative morbidity. These results support a liberal bypass-first paradigm in both adult and paediatric cohorts.

Surgical repair of a large intrathoracic meningocele associated with neurofibromatosis type 1 after failed cystoperitoneal shunts: illustrative case.

BACKGROUND: Surgical treatment of intrathoracic meningoceles, commonly associated with neurofibromatosis type 1 (NF1), aims to reduce sac size for symptomatic relief. The procedures can be divided into cerebrospinal fluid diversion and definitive repair. The authors describe the management of an intrathoracic meningocele in a 56-year-old female with preexisting NF1. OBSERVATIONS: The patient presented with progressive dyspnea. Magnetic resonance imaging revealed a left hemithoracic meningocele arising from the thecal sac at C7-T2. Two attempts at diversion by cystoperitoneal shunts resulted in recurrence. For definitive repair, T2-3 costotransversectomy was performed, and intradural closure of the meningocele opening was performed utilizing spinal dura and autologous fascia lata graft. Trapezius muscle regional flap was turned for reinforcement. Persistent leak warranted reoperation 7 days later. A transthoracic approach was undertaken using video-assisted thoracoscopic resection of the sac at aortic arch level, with reinforcement by latissimus dorsi flap and synthetic materials. Mechanical pleurodesis was performed. Intradural repair of the meningocele opening was revised. LESSONS: Inherent dural abnormality makes repair difficult for meningoceles associated with NF1. A combined intradural and thoracoscopic approach with regional muscle flap and synthetic material reinforcement is a unique method for definitive treatment. Some essential points of perioperative management are highlighted.

Near-complete regression 19 years after Gamma Knife radiosurgery of vestibular schwannoma with massive pseudoprogression: case report.

Gamma Knife radiosurgery (GKRS) is a frequent treatment choice for patients with small- to moderate-sized vestibular schwannoma (VS). However, pseudoprogression after GKRS is commonly observed, with a reported incidence ranging from 7% to 77%. The wide range of the reported incidence of pseudoprogression reflects the fact that there is no consensus on how it should be diagnosed. The authors present the case of a 66-year-old woman who had a 2.5-cm right-sided VS treated with GKRS in 1997. The first posttreatment MRI obtained 5 months later showed that the tumor volume had increased to 9.7 cm3. The tumor volume increased further and reached its peak 24 months after treatment at 20.9 cm3, which was a 161% increase from pretreatment volume. Thereafter, the tumor shrank gradually and mass effect on the brainstem reduced over time. By 229 months after treatment, the tumor volume was 1.0 cm3, equaling 12.5% of pretreatment tumor volume, or 4.8% of peak tumor volume after treatment. This case demonstrates that if a patient remains asymptomatic despite a dramatic increase in tumor volume after GKRS, observation remains an option, because even a very sizable tumor can shrink with near-complete resolution. Patients undergoing GKRS for VS should be counseled regarding the possibility of pseudoprogression, and followed carefully over time while avoiding premature decisions for surgical removal after treatment.

Vertebral-carotid bypass for common carotid artery occlusion.

One of the treatment options for long segment common carotid artery (CCA) occlusion is bypass surgery with different combinations of donors and receipts. Using vertebral artery (VA) as the donor for CCA occlusion was uncommonly reported. The reported cases were using jump graft to connect V3 segment of VA to either CCA or ICA. We describe our patient using V2 segment as the donor for VA-CCA bypass as treatment for CCA occlusion. Our patient was a 51 years old gentleman with Marfan syndrome and had multiple operations that included total arch replacement. He presented with sudden onset of spontaneous right frontal subarachnoid haemorrhage and repeated episodes of TIA with left upper limb numbness. CTA showed occluded right CCA and anastomosis between branches from subclavian artery and occipital artery. CT perfusion showed hypoperfusion of right hemisphere. To avoid damaging the anastomosis at subclavian artery and occipital artery, we decided for V2-RAG (radial artery graft)-CCA bypass. It was done by exposing the V2 segment at C4/5 level, performing end-to-side anastomoses at V2-RAG and RAG-CCA junctions where the RAG was underneath the internal jugular vein. Patient had no new deficits after surgery and no more TIAs. CTA performed one week after surgery showed patent RAG. In conclusion, using V2 for VA-CCA bypass is technically feasible and may have theoretical advantages over using V3. V2-CCA bypass is an option for CCA occlusion in very selected patients.

Successful Emergency Rescue Open Embolectomy for Failed Endovascular Thrombectomy in Acute Ischemic Stroke: 2-Dimensional Operative Video.

This operative video demonstrates an open surgical thrombectomy for a 61-yr-old woman with failed endovascular embolectomy in acute ischemic stroke. Good functional outcome can be achieved when this operation is timely performed within the therapeutic window. This patient has atrial fibrillation. She was admitted for sudden onset of left-sided hemiplegia and aphasia. National Institutes of Health Stroke Scale (NIHSS) was 20/42 before the operation. Computed tomography (CT) cerebral angiogram showed right internal cerebral artery (ICA) occlusion from the cervical portion. Urgent intra-arterial (IA) thrombectomy was started 2 h after symptom onset, but failed despite the use of a stentriver and a large-bore aspiration catheter together. Emergency rescue open thrombectomy was performed with right pterional craniotomy 6 h after symptom onset. Sylvian fissure was dissected to expose the supraclinoid ICA, ICA bifurcation, A1, and M1. A transverse arteriotomy was made at the ICA bifurcation and open surgical thrombectomy was performed. Reperfusion was established in 86 min after skin incision. Intraoperative indocyanine green video-angiography showed patent flow over ICA bifurcation to M1 and A1. She had a good recovery with the return of the left-sided power and was discharged home. At 2-mo postoperative assessment, she was able to walk unaided independently. The modified Barthel Index (BI) was 74/100. Her activity of daily living was independent. We must emphasize IA thrombectomy is the standard treatment, and the role of open surgery remains a potential rescue procedure. Good functional outcome can be achieved when emergency rescue open thrombectomy is performed within the therapeutic window.

Endovascular Intervention for Early Postoperative Stenosis of Extracranial-Intracranial Bypass Graft: Case Report and Review of the Literature.

BACKGROUND: Bypass graft stenosis following extracranial-intracranial bypass surgery carries significant risks for morbidity and mortality. In case of graft failure, treatment options include surgical revision and endovascular intervention. Whereas endovascular intervention following coronary artery bypass is well established, the role of endovascular therapy in cerebral bypass conduits is rarely reported. We present a case of extracranial-intracranial bypass graft stenosis in the early postoperative period that was successfully treated by endovascular angioplasty and stenting. CASE DESCRIPTION: A middle-aged patient presented with a malignant skull base tumor with internal carotid artery invasion. Extracranial-intracranial bypass surgery was performed for flow preservation before tumor removal. Autologous radial artery was used as the bypass graft conduit. Symptomatic graft stenosis was encountered in the immediate postoperative period. Treatments in the form of intra-arterial vasodilator infusion and balloon angioplasty led to only minor flow improvement. The narrowing was eventually salvaged by endovascular stenting. Good clinical and radiologic outcomes were achieved at 6-month follow-up. CONCLUSIONS: Endovascular intervention is a feasible treatment option in management of graft stenosis after cerebral revascularization surgery. Our case adds evidence to the safety and role of endovascular intervention in early cerebral bypass conduit failure. In addition, endovascular stenting can be considered as a salvage option for cases that are refractory to angioplasty.

Thrombectomy Outcomes of Intracranial Atherosclerosis-Related Occlusions.

Background and Purpose- Intracranial atherosclerosis (ICAS) is an important cause of large vessel occlusion and poses unique challenges for emergent endovascular thrombectomy. The risk factor profile and therapeutic outcomes of patients with ICAS-related occlusions (ICAS-O) are unclear. We performed a systematic review and meta-analysis of studies reporting the clinical features and thrombectomy outcomes of large vessel occlusion stroke secondary to underlying ICAS (ICAS-O) versus those of other causes (non-ICAS-O). Methods- A literature search on thrombectomy for ICAS-O was performed. Random-effect meta-analysis was used to analyze the prevalence of stroke risk factors and outcomes of thrombectomy between ICAS-O and non-ICAS-O groups. Results- A total of 1967 patients (496 ICAS-O and 1471 non-ICAS-O) were included. The ICAS-O group had significantly higher prevalence of hypertension (odds ratio [OR] 1.46; 95% CI, 1.10-1.93), diabetes mellitus (OR, 1.68; 95% CI, 1.29-2.20), dyslipidemia (OR, 1.94; 95% CI, 1.04-3.62), smoking history (OR, 2.11; 95% CI, 1.40-3.17) but less atrial fibrillation (OR, 0.20; 95% CI, 0.13-0.31) than the non-ICAS-O group. About thrombectomy outcomes, ICAS-O had higher intraprocedural reocclusion rate (OR, 23.7; 95% CI, 6.96-80.7), need for rescue balloon angioplasty (OR, 9.49; 95% CI, 4.11-21.9), rescue intracranial stenting (OR, 14.9; 95% CI, 7.64-29.2), and longer puncture-to-reperfusion time (80.8 versus 55.5 minutes, mean difference 21.3; 95% CI, 11.3-31.3). There was no statistical difference in the rate of final recanalization (modified Thrombolysis in Cerebral Infarction score of 2b/3; OR, 0.67; 95% CI, 0.36-1.27), symptomatic intracerebral hemorrhage (OR, 0.79; 95% CI, 0.50-1.24), good functional outcome (modified Rankin Scale score of 0-2; OR, 1.16; 95% CI, 0.85-1.58), and mortality (OR, 0.94; 95% CI, 0.64-1.39) between ICAS-O and non-ICAS-O. Conclusions- Patients with ICAS-O display a unique risk factor profile and technical challenges for endovascular reperfusion therapy. Intraprocedural reocclusion occurs in one-third of patients with ICAS-O. Intraarterial glycoprotein IIb/IIIa inhibitors infusion, balloon angioplasty, and intracranial stenting may be viable rescue treatment to achieve revascularization, resulting in comparable outcomes to non-ICAS-O.

Repair of Anterior Skull Base Defect by Dual-Layer/Split-Frontal Pericranial Flap.

INTRODUCTION: Normal skull base structures are destroyed either by the skull base pathology itself or during surgery that results in cerebrospinal fluid (CSF) leak. Skull base repair is usually performed transnasally by using a nasal septal flap. But when NSF is not available and failed repeated transnasal repair, a cranionasal repair with frontal pericranial flap (PF) can be attempted to achieve the highest successful chance. We performed a dual layer/split PF repair of a skull base defect using cranionasal approach and here we describe the technique. CASE DESCRIPTION: A 74-year-old man suffered from CSF leak and ventriculitis after multiple transnasal surgeries for pituitary macroadenoma despite multiple repairs with intranasal vascularized flaps. We performed repair by cranionasal approach and using frontal PF. The frontal PF was divided into left and right halves. The left half went intradural, through the chiasmatic window to reach the sella and cover the tubercular and sellar defect from above. The right half went through the nasion into the nose to cover the defect from below. So the defect was covered by two vascularized flap from a single frontal PF. The repair was successful with no CSF leak and infection successfully treated by antibiotics. CONCLUSION: We introduced the cranionasal dual layer/split PF technique to repair anterior skull base and successfully stopped the CSF leak in a patient after multiple EEA surgeries. This technique should only be considered in specific difficult situation where usual repair by EEA is impossible.

Improving Survival with Tranexamic Acid in Cerebral Contusions or Traumatic Subarachnoid Hemorrhage: Univariate and Multivariate Analysis of Independent Factors Associated with Lower Mortality.

BACKGROUND: Fall with head injury is a pervasive challenge, especially in the aging population. Contributing factors for mortality include the development of cerebral contusions and delayed traumatic intracerebral hematoma. Currently, there is no established specific treatment for these conditions. OBJECT: This study aimed to investigate the impact of independent factors on the mortality rate of traumatic brain injury with contusions or traumatic subarachnoid hemorrhage. METHODS: Data were collected from consecutive patients admitted for cerebral contusions or traumatic subarachnoid hemorrhage at an academic trauma center from 2010 to 2016. The primary outcome was the 30-day mortality rate. Independent factors for analysis included patient factors and treatment modalities. Univariate and multivariate analyses were conducted to identify independent factors related to mortality. Secondary outcomes included thromboembolic complication rates associated with the use of tranexamic acid. RESULTS: In total, 651 consecutive patients were identified. For the patient factors, low Glasgow Coma Scale on admission, history of renal impairment, and use of warfarin were identified as independent factors associated with higher mortality from univariate and multivariate analyses. For the treatment modalities, univariate analysis identified tranexamic acid as an independent factor associated with lower mortality (P = 0.021). Thromboembolic events were comparable in patients with or without tranexamic acid. CONCLUSION: Tranexamic acid was identified by univariate analysis as an independent factor associated with lower mortality in cerebral contusions or traumatic subarachnoid hemorrhage. Further prospective studies are needed to validate this finding.

A2, M2, P2 aneurysms and beyond: results of treatment with pipeline embolization device in 65 patients.

BACKGROUND: Intracranial aneurysms located in the distal vessels are rare and remain a challenge to treat through surgical or endovascular interventions. OBJECTIVE: To describe a multicenter approach with flow diversion using the pipeline embolization device (PED) for treatment of distal intracranial aneurysms. METHODS: Cases of distal intracranial aneurysms defined as starting on or beyond the A2 anterior cerebral artery, M2 middle cerebral artery, and P2 posterior cerebral artery segments were included in the final analysis. RESULTS: 65 patients with distal aneurysms treated with the PED were analyzed. Median aneurysm size at the largest diameter was 7.0 mm, 60% were of a saccular morphology, and 9/65 (13.8%) patients presented in the setting of acute rupture. Angiographic follow-up data were available for 53 patients, with a median follow-up time of 6 months: 44/53 (83%) aneurysms showed complete obliteration, 7/53 (13.2%) showed reduced filling, and 2/53 (3%) showed persistent filling. There was no association between patient characteristics, including aneurysm size (P=0.36), parent vessel diameter (P=0.27), location (P=0.81), morphology (P=0.63), ruptured status on admission (P=0.57), or evidence of angiographic occlusion at the end of the embolization procedure (P=0.49). Clinical outcome data were available for 60/65 patients: 95% (57/60) had good clinical outcome (modified Rankin Scale score of 0-2) at 3 months. CONCLUSIONS: This large multicenter study of patients with A2, M2, and P2 distal aneurysms treated with the PED showed that flow diversion may be an effective treatment approach for this rare type of vascular pathology. The procedural compilation rate of 7.7% indicates the need for further studies as the flow diversion technology constantly evolves.

Long-Term Risk of In-Stent Restenosis and Stent Fracture for Extracranial Vertebral Artery Stenting.

PURPOSE: Stenting and angioplasty of the vertebral artery (VA) is used to treat symptomatic stenosis but the long-term outcomes and complications are unclear. This study evaluated the long-term clinical outcomes and procedure-related complications in patients who underwent extracranial VA stenting and angioplasty, in particular the risks of in-stent restenosis (ISR) and stent fracture. METHODS: This was a retrospective review of consecutive patients suffering from symptomatic extracranial VA stenosis who were treated with balloon-expandable bare metal stents. The clinical and angiographical outcomes were reviewed for procedural complications, recurrent stroke, ISR and stent fracture. RESULTS: In this study 22 patients (17 male, 5 female) with a mean age of 63.4 years (SD 9.1 years) were included. The median follow-up was 56 months (interquartile range IQR 51.8 months). There were no periprocedural complications. The cumulative ISR risk was 45% with 6 cases detected at 1 year and 3 cases detected at 3 years post operation. The cumulative stent fracture rate at 1 year, 3 years, 5 years and the entire follow-up period were 5%, 15%, 25%, and 30%, respectively. Posterior circulation stroke occurred in 1 patient (4.5%), and 3 patients died of non-cerebrovascular causes during follow-up. Of the patients 2 with ISR and stent fracture required additional treatment. CONCLUSION: The long-term ISR and stent fracture risks were high in extracranial VA stenosis treated with balloon-expandable bare metal stents. The risk of stent fracture increased over time during the follow-up period. Further studies should be conducted to clarify the long-term safety and efficacy of extracranial VA stenting.

Severity of intracranial carotid artery calcification in intracranial atherosclerosis-related occlusion treated with endovascular thrombectomy.

OBJECTIVES: Intracranial atherosclerosis related large vessel occlusions (ICAS-O) are challenging to diagnose and manage. The degree of intracranial carotid artery calcification may assist pre-thrombectomy diagnosis of ICAS and guide treatment strategy. The aim of the study is to determine if intracranial carotid calcification is associated with ICAS-O. PATIENTS AND METHODS: Consecutive large vessel occlusion patients who underwent thrombectomy from 2006 to 2017 were retrospectively studied. Patients were classified into ICAS-O if pre-existing atherosclerotic lesion was identified as the etiology for large vessel occlusion during the thrombectomy. The degree of intracranial carotid artery calcification (ICAC), technical and clinical outcomes of ICAS-O was compared with non-ICAS-O patients. RESULTS: In a retrospective cohort study of 64 thrombectomy patients, ICAS-O accounted for 14.1% of cases and was associated with higher degree of carotid calcification (mean Woodcock scale 2.8 vs 1.6, p = 0.044), need of stent-retreiver rescue (55.6% vs 5.5%, p = 0.001), and adjuvant stenting or angioplasty (33.3% vs 0%, p = 0.002) compared with non-ICAS-O. CONCLUSION: The severity of ICAC may be associated with ICAS-O as the underlying etiology amongst thrombectomy patients. Compared with large vessel occlusion of other causes, ICAS-O was associated with more failure of aspiration and a higher need of adjuvant stenting and angioplasty.

The application of point-of-care platelet function assay in guiding platelet transfusion in aspirin-users with intracranial haemorrhages.

BACKGROUND: An increasing number of patients with intracranial haemorrhages are aspirin-users. Neurosurgeons commonly attempt to minimize the risk of re-bleeding by withholding the medication and giving platelet transfusion. However, recent studies raised safety concerns and showed poorer outcome with platelet transfusion when the latter was not guided by changes in platelet function. AIM OF STUDY: To study the temporal pattern and degree of changes in platelet activities following a fixed dose of platelet transfusion in aspirin-users with intracranial haemorrhages. METHODS: Aspirin-users with intracranial haemorrhages underwent baseline aspirin response units (ARU) using the VerifyNow® assay. Those who showed abnormal platelet activity received a single dose of 4 units of platelet concentrate. ARU were then repeated at 4 h, 24 h and 48 h post-transfusion. Patients were classified according to their responses to transfusion. RESULTS: Twenty patients were recruited. At 4 h after transfusion, 11 (55%) patients had normalised platelet activities while the rest may show delayed or absent of normalization. Overall, eight (40%) patients were 'early and persistent transfusion responders', five 'delayed transfusion responders', and five (25%) had persistently abnormal platelet function. Two (10%) patients who initially responded to transfusion failed to maintain normalized platelet activity. CONCLUSION: Platelet activities in aspirin-users showed considerable heterogeneity up to 48 h following a blanket approach of platelet transfusion. The need for repeated transfusion or alternative therapy strongly argues for a guided practice for transfusion based on point-of-care platelet function assay. Future research should also adopt this approach to re-examine the safety and effectiveness of platelet transfusion in these patients.

Endoplasmic reticulum chaperone prolyl 4-hydroxylase, beta polypeptide (P4HB) promotes malignant phenotypes in glioma via MAPK signaling.

Endoplasmic reticulum (ER) chaperone Prolyl 4-hydroxylase, beta polypeptide (P4HB) has previously been identified as a novel target for chemoresistance in glioblastoma multiforme (GBM). Yet its functional roles in glioma carcinogenesis remain elusive. In clinical analysis using human glioma specimens and Gene Expression Omnibus (GEO) profiles, we found that aberrant expression of P4HB was correlated with high-grade malignancy and an angiogenic phenotype in glioma. Furthermore, P4HB upregulation conferred malignant characteristics including proliferation, invasion, migration and angiogenesis in vitro, and increased tumor growth in vivo via the mitogen-activated protein kinase (MAPK) signaling pathway. Pathway analysis suggested genetic and pharmacologic inhibition of P4HB suppressed MAPK expression and its downstream targets were involved in angiogenesis and invasion. This is the first study that demonstrates the oncogenic roles of P4HB and its underlying mechanism in glioma. Since tumor invasion and Vascularisation are typical hallmarks in malignant glioma, our findings uncover a promising anti-glioma mechanism through P4HB-mediated retardation of MAPK signal transduction.

Moving the goalposts: A comparison of different definitions for primary external ventricular drain infection and its risk factors: A multi-center study of 2575 patients.

External ventricular drainage is the most common procedure performed in daily neurosurgical practice. One devastating complication is ventriculostomy-associated infection, but the establishment of evidence-based management guidelines has been hindered by the lack of an universal definition. There is also limited data with regard to the utility of comorbidity health indices and surgery-related factors in predicting infection. This study aims to compare the incidence of infection according to five commonly used definitions and to identify risk factors for this complication. 2575 patients from seven neurosurgical centers in Hong Kong underwent primary external ventricular drainage. The frequency of infection according to Gozal was 2.2% (n=57), 4.7% (Chi), 0.6% (Lozier), 0.8% (Lyke) and 2.8% (Scheithauer). The commonest pathogen was coagulase negative staphylococcus (39%) and 49% of all microbial isolates were multiple-drug resistant. The mean Charlson comorbidity index was 0.5±1.1. Using Gozal's definition as the primary endpoint, the index was not predictive of infection and no surgical risk factors were identified. The only significant risk factor was the performance of two or more additional neurosurgical procedures within 30days of catheterization (OR: 2.1, 95% CI 1.1-4.5). The rate of infection is relatively low, but considerable disparity exists depending on the definition used. Our data implies that patient factors, in particular the Charlson comorbidity index, and variations in surgical practice are less influential than the strict observance of infection control measures. The high incidence of antibiotic-resistant bacteria is concerning and the routine of exchange of catheters within 30days should be discouraged.