Habituation of the cold shock response: A systematic review and meta-analysis.

Cold water immersion (CWI) evokes the life-threatening reflex cold shock response (CSR), inducing hyperventilation, increasing cardiac arrhythmias, and increasing drowning risk by impairing safety behaviour. Repeated CWI induces CSR habituation (i.e., diminishing response with same stimulus magnitude) after ∼4 immersions, with variation between studies. We quantified the magnitude and coefficient of variation (CoV) in the CSR in a systematic review and meta-analysis with search terms entered to Medline, SportDiscus, PsychINFO, Pubmed, and Cochrane Central Register. Random effects meta-analyses, including effect sizes (Cohen's d) from 17 eligible groups (k), were conducted for heart rate (HR, n = 145, k = 17), respiratory frequency (fR, n = 73, k = 12), minute ventilation (Ve, n = 106, k = 10) and tidal volume (Vt, n = 46, k=6). All CSR variables habituated (p < 0.001) with large or moderate pooled effect sizes: ΔHR -14 (10) bt. min-1 (d: -1.19); ΔfR -8 (7) br. min-1 (d: -0.78); ΔVe, -21.3 (9.8) L. min-1 (d: -1.64); ΔVt -0.4 (0.3) L -1. Variation was greatest in Ve (control vs comparator immersion: 32.5&24.7%) compared to Vt (11.8&12.1%). Repeated CWI induces CSR habituation potentially reducing drowning risk. We consider the neurophysiological and behavioural consequences.

The role of surgical transcatheter valve implantation for the treatment of severe mitral annular calcification.

With a rise in the aging population, mitral annular calcification is increasingly encountered with an incidence of 10% in over 70 years old. This with increasing patient comorbidities presents a technical challenge due to the risk of atrioventricular disruption which is associated with high operative mortality of up to 75%. We describe two cases of severe mitral disease with marked annular calcification successfully treated with a balloon expandable transcatheter valve which was deployed on cardiopulmonary bypass via a trans-atrial approach.

A pathway to earlier discharge following TAVI: Assessment of safety and resource utilization.

INTRODUCTION: There is considerable variability within the population of patients treated with transcatheter aortic valve implantation (TAVI), the procedural approach and time to discharge. In Belfast, from the commencement of our program, our approach has been to perform TAVI by the least invasive approach, where feasible, utilizing a percutaneous transfemoral route and local anesthetic. By analyzing our Belfast TAVI database we identified factors that predicted shorter admission times without impacting adversely on patient safety. Following this, we developed an early discharge pathway. The aim of this current study was to perform a prospective analysis of outcomes in our unit since implementation of this pathway assessing discharge time, mortality, serious adverse events, readmission, and resource implications for patients according to time to discharge. METHODS: Consecutive patients who underwent TAVI and were successfully discharged from 2013 to 2014 over a 14 month period were included, and analyzed according to time to discharge. Baseline and procedural characteristics, mortality, serious adverse events, readmission, and cost were assessed. RESULTS: In total 120 patients were included, 26 (21.7%) were discharged the same/next day, 39 (32.5%) early (>1-4 days), and 55 (45.8%) discharged in the late group. There was no significant difference in baseline or preprocedural characteristics. The incidence of complications was low, and there was no difference in 30-day mortality (P = 0.167) or readmission rates between groups (P = 0.952). Resource analysis revealed the late discharge group cost £3,091.6 more per patient per TAVI than same/next day discharge group. CONCLUSION: Same/next day discharge can be performed safely in appropriately selected patients. Although this will be achieved in a minority of patients (21.7% in this study using an early discharge pathway) it has potential for resource and cost savings. © 2015 Wiley Periodicals, Inc.

Effect of left atrial and ventricular abnormalities on renal transplant recipient outcome-a single-center study.

BACKGROUND: Premature cardiovascular (CV) death is the commonest cause of death in renal transplant recipients. Abnormalities of left ventricular (LV) structure (collectively termed uremic cardiomyopathy) and left atrial (LA) dilation, a marker of fluid status and diastolic function, are risk factors for reduced survival in patients with end stage renal disease (ESRD). In the present analysis, we studied the impact of pre-transplant LA and LV abnormalities on survival after successful renal transplantation (RT). METHODS: One hundred nineteen renal transplant recipients (first transplant, deceased donors) underwent cardiovascular MRI (CMR) as part of CV screening prior to inclusion on the waiting list. Data regarding transplant function and patient survival after transplantation were collected. RESULTS: Median post-transplant follow-up was 4.3 years (interquartile range (IQR) 1.9, 6.2). During the post-transplant period, 13 patients returned to dialysis after graft failure and 23 patients died with a functioning graft. Survival analyses, censoring for patients returning to dialysis, showed that pre-transplant LV hypertrophy and elevated LA volume were significantly associated with reduced survival after transplantation. Multivariate Cox regression analyses demonstrated that longer waiting time, poorer transplant function, presence of LV hypertrophy and higher LA volume on screening CMR and female sex were independent predictors of death in patients with a functioning transplant. CONCLUSIONS: Presence of LVH and higher LA volume are significant, independent predictors of death in patients who are wait-listed and proceed with renal transplantation.

Late gadolinium enhancement is common in patients with hypertrophic cardiomyopathy and no clinical risk factors for sudden cardiac death: A single center experience.

BACKGROUND: Cardiac magnetic resonance (CMR) is used in the diagnosis and risk stratification of hypertrophic cardiomyopathy (HCM) and can detect myocardial replacement fibrosis (anindependent predictor of adverse cardiac outcomes) using late gadolinium enhancement (LGE). METHODS: We retrospectively analysed CMR studies carried out over a 2 year period identifying those which were diagnostic of HCM. 117 cases were analysed. Mean age of subjects was 53 years and 78 (67%) were male. Mean ejection fraction (EF) was 68.3% with a mean left ventricular (LV) mass index of 89.4 g/m². Hypertrophy was predominantly asymmetric in 94 (80%). RESULTS: All subjects received gadolinium and 80 (68%) had evidence of LGE. LVEF was lower (67 vs. 71%; p = 0.015) and LV mass index higher (94 vs. 81 g/m²; p = 0.007) in the LGE group. The proportion of patients with at least 1 clinical risk factor for sudden cardiac death (SCD) was similar in groups with and without LGE (48% vs. 32%; p = 0.160). In this study, a significant proportion (62%) of patients without clinical risk factors for SCD were found to have LGE on CMR. These patients would not currently be considered for therapy with an implantable cardiac defibrillator. CONCLUSIONS: 1. Patients with HCM are at increased risk of SCD, but identifying patients who may benefit from implantable defibrillators is difficult. 2. LGE is associated with adverse cardiovascular outcomes in HCM, but is present in a large proportion of patients. 3. Many patients without clinical risk factors for SCD have LGE and would not currently be considered for an implantable cardiac device.

A pressing matter--mediastinal fibrosis with near obliteration of the pulmonary arteries.

Idiopathic mediastinal fibrosis is a rare, histologically benign condition which often presents with symptoms attributable to compression of vital mediastinal structures. Diagnosis can be difficult and individualized treatments are required for patients, with possible intervention including pharmacotherapy, surgery, and percutaneous stenting. We present a case of idiopathic mediastinal fibrosis present in a 50-year-old woman as compression and near obliteration of the pulmonary arteries. A percutaneous approach was utilized with bilateral balloon expandable kissing stents simultaneous deployed from the main pulmonary artery to the right and left pulmonary arteries. There was instantaneous improvement in the pulmonary and systemic hemodynamics. Her immediate postprocedure course was complicated by reperfusion injury to the right lung, requiring intubation and ventilation. The patient made a full recovery and remains well at 6 months. Our case highlights the procedural and postprocedural difficulties that exist in such cases, and reinforces the value of endovascular stenting strategies in the management of patients with this rare condition.

Particulate production during orthodontic production laboratory procedures.

Dental technicians are exposed to respirable particles during their everyday work. This study investigated particulate production during dental laboratory procedures. Real-time air sampling of dental laboratory production processes was carried out, including the use of a plaster hopper, trimming study models and the trimming and polishing of removable orthodontic appliances. Respirable dust volumes in mg/m(3) were determined using real-time air sampler and were compared with the Workplace Exposure Limits (WELs) advised by the Control of Substances Harmful to Health regulations. The use of the plaster hopper produced the highest level of respirable dusts, which might exceed the recommended WELs for respirable dusts. Trimming study models and removable orthodontic appliances using suitable ventilation produced levels of respirable dusts, well below the WEL. Suitable ventilation adjacent to the plaster hoppers is advisable in order to reduce any inhalation risk to dental technicians.

Magnetic resonance imaging in a patient with a dual chamber pacemaker.

Having a pacemaker has been seen an absolute contraindication to having an MRI scan. This has become increasingly difficult in clinical practice as insertion of pacemakers and implantable cardiac defibrillators is at an all time high. Here we outline a case where a 71-year-old male patient with a permanent pacemaker needed to have an MRI scan to ascertain the aetiology of his condition and help guide further management. Given this clinical dilemma, an emergency clinical ethics consultation was arranged. As a result the patient underwent an MRI scan safely under controlled conditions with a consultant cardiologist and radiologist present. The results of the MRI scan were then able to tailor further treatment. This case highlights that in certain conditions an MRI can be performed in patients with permanent pacemakers and outlines the role of clinical ethics committees in complex medical decision making.

Quantitative and qualitative analysis of particulate production during simulated clinical orthodontic debonds.

OBJECTIVES: The objectives of this investigation were firstly to quantitatively and qualitatively determine particulate production during orthodontic debond and enamel cleanup procedures, and secondly to examine what methods can be employed to minimize operator exposure to such dust particles. METHODS: A qualitative study was performed to determine the aerodynamic diameters and compositions of particulates produced during simulated clinical debonds and enamel cleanup procedures on extracted teeth. In each case the enamel was cleaned using tungsten carbide burs in either a high or slow speed handpiece, with or without water coolant spray, with or without high volume evacuation (HVE) or a face mask. RESULTS: The use of a high speed handpiece with a tungsten carbide bur and water irrigation at enamel cleanup produced the greatest concentration of respirable particulates. Within this dust, calcium, phosphorus, aluminum and silicon were the most commonly found elements. The dust levels observed did not exceed limits advised for respirable dusts in general. However, the concentration of silica within the dusts created is unknown. The face mask and HVE were effective at reducing exposure to respirable particles, but the mask was most effective, reducing exposure by up to 96%. SIGNIFICANCE: A face mask is an effective means of reducing dust inhalation and is advised for all clinical procedures that produce dusts.

Renal transplantation is not associated with regression of left ventricular hypertrophy: a magnetic resonance study.

BACKGROUND AND OBJECTIVES: Patients with end-stage renal failure (ESRD) have an increased risk of premature cardiovascular (CV) disease. Left ventricular hypertrophy is an independent risk factor for CV events and death in ESRD. Renal transplantation has been associated with reduction in CV risk and echocardiographic regression of left ventricular hypertrophy. However, echocardiography overestimates LV mass in ESRD patients. Cardiac magnetic resonance (CMR) provides more detailed, volume-independent, measures of cardiac structure. Changes in LV mass measured by CMR after renal transplantation were studied. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Fifty patients underwent CMR on two occasions. Twenty-five were transplanted before the second scan. CMR was performed to measure LV mass index (LVMI), ejection fraction, end-diastolic and end-systolic volumes. Changes were expressed as percentage change over time. Patients with CV events between scans (e.g., acute coronary syndrome, myocardial infarction) were excluded. All transplant patients had serum creatinine <150 mumol/L. RESULTS: There was no significant change in LVMI between patients who underwent renal transplantation and those who remained on dialysis (transplanted mean, 2.75%/yr, +/- 9.1 versus dialysis, -3.6%/yr +/- 16.7). In addition, there were no significant changes in end-diastolic volume (transplant, 0.1%/yr +/- 19.5 versus not transplanted, -3.4%/yr +/- 31.5), end-systolic volume (transplanted mean, 15.2%/yr +/- 65.2 versus not transplanted, 3.0%/yr +/- 55.5), or ejection fraction (transplant, 2.1%/yr +/- 11.9 versus not transplanted, -0.4%/yr +/- 5.3). CONCLUSIONS: Renal transplantation is not associated with significant regression of LVMI on CMR compared with patients who remain on the transplant waiting list.

Aortic stiffness and diastolic flow abnormalities in end-stage renal disease assessed by magnetic resonance imaging.

BACKGROUND: Arterial stiffness is associated with adverse cardiovascular outcomes, particularly in end-stage renal disease (ESRD). One mechanism linking arterial stiffness with cardiovascular events may be the changes in pressure wave reflection on ventricular ejection and coronary perfusion during diastole. We illustrate this using MRI to describe aortic elastic properties and alterations of diastolic flow in comparison to derived central pressure characteristics. METHODS: Ten patients with ESRD and ten control subjects were studied. Transverse images of the ascending aorta were obtained by cardiac MRI. Aortic distensibility was calculated using brachial pulse pressure. MRI flow maps were obtained from the ascending aorta and aortic pressure was calculated using SphygmoCor. RESULTS: ESRD patients had reduced aortic distensibility compared to the controls (median 0.00464 mm Hg(-1) vs. 0.00152 mm Hg(-1), p = 0.0057). Furthermore, in diastole, normal subjects show net reversal of blood flow in the ascending aorta, with a mean of -19.6 versus +7.6 ml/min in the ESRD group; p = 0.045. CONCLUSIONS: Using non-invasive methods we have demonstrated a marked reduction in aortic distensibility along with disturbances in aortic flow, providing insight into the pathophysiology of ventricular-vascular interaction. The normal group showed reversal of diastolic blood flow, which may have a direct relationship with coronary perfusion parameters, which was absent in the ESRD group.

Body temperature management after severe traumatic brain injury: methods and protocols used in the United Kingdom and Ireland.

OBJECTIVE: To establish whether there is consensus in the management of body temperature in patients with severe traumatic brain injury (TBI) admitted to hospitals in the United Kingdom and Ireland for neurosurgical intensive care. METHODS: Permission was granted from the Society of British Neurosurgeons (SBNS) and the Local Research Ethics Committee to undertake the survey. A senior member of nursing staff from all adult neurosurgical units, excluding our own, was contacted by telephone. RESULTS: All 33 adult neurosurgical centres participated. Six units had a formal written protocol for the management of body temperature. For the remainder (27 units), interest was expressed in a protocol for temperature management particularly for those patients with intractable hyperthermia/fever. Administration of the antipyretic paracetamol was the most common 'first-line' treatment (13 units). Other 'first-line' methods were: circulating air-cooling blankets (9 units), water-filled cooling blankets (6 units), tepid sponging or wet soaks (2 units), convection fans (2 units) and administration of cold fluids via the gut or circulation (1 unit). When 'first-line' methods failed to bring about a fall in temperature, different combinations of these methods were used. CONCLUSIONS: From this survey, it is evident that there is no consensus in the approach to temperature management in neurosurgical intensive care patients with severe TBI. Review and rationalisation of systems of care may be required in an effort to develop evidence-based nationwide guidelines.

Determinants of hypertension and left ventricular function in end stage renal failure: a pilot study using cardiovascular magnetic resonance imaging.

Cardiovascular disease is the principal cause of mortality in patients with renal failure. Left ventricular (LV) abnormalities are adverse prognostic indicators for cardiovascular outcome. The aim of this study was to use cardiac magnetic resonance scanning (CMR) to define LV functional abnormalities in haemodialysis (HD) patients and clarify the determinants of blood pressure (BP) and the effect of anaemia in this population. We studied 44 HD patients and 11 controls with CMR performed following dialysis. Forty patients and 11 controls completed the study. LV mass (P<0.001) and estimated systemic vascular resistance (SVR) (P = 0.002) were significantly higher in the dialysis group compared to controls. LV ejection fraction (P = 0.002) and SV (P = 0.043) were lower than controls. In the HD patients, BP correlated significantly with cardiac output (CO; r = 0.569, P<0.001) and end diastolic volume (EDV; r = 0.565, P<0.001) but there was no correlation between BP and SVR (r = 0.201, P = 0.594). Haemoglobin was inversely correlated with both CO (r = -0.531, P<0.001) and EDV (r = -0.493, P = 0.001) and positively with SVR (r = 0.402, P = 0.009). HD patients had a higher LV mass and lower ejection fraction than controls. The relationship of BP with CO, but not SVR, supports the theory that a major determinant of BP is intravascular volume and CO rather than vascular resistance although there was a fixed increase in SVR in this population. Improved understanding of the mechanisms underlying increased SVR and improved control of CO and intravascular volume may allow better therapeutic strategies. CMR provides insights into the pathophysiology of hypertension and LV dysfunction in HD patients.

Inhibition of proliferation and signalling mechanisms in human lymphocytes by fluvastatin.

1. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (statins) reduce serum cholesterol and have proven benefits in the treatment of cardiovascular disease. However, recent work suggests that statins may exert immunosuppressive effects in isolated lymphocytes and in solid organ transplant recipients. Fluvastatin does not interfere with the metabolism of commonly used immunosuppressive agents and, therefore, may have benefits in transplant recipients. 2. The aim of the present study was to investigate the potential immunomodulatory effects of fluvastatin in vitro in human lymphocytes and the underlying effects on signal transduction. 3. In vitro, fluvastatin (10 micromol/L) caused a time-dependent inhibition of T cell proliferation in response to cross-linking of CD3. 4. Thymidine incorporation was reduced by 22, 81 and 92% at days 1, 3 and 5, respectively. 5. Mevalonate (1 micromol/L) treatment for 4 or 24 h significantly reduced the inhibitory effects of fluvastatin; the reversal was abrogated by simultaneous exposure to mevalonate and a farnesyl transferase inhibitor. 6. At a subcellular level, fluvastatin treatment was associated with reduced functional activity of Ras-dependent extracellular signal-regulated kinase pathways and of Rho-dependent p38 activation. 7. These data suggest that the potential immunosuppressive actions of statins involve inhibition of subcellular pathways dependent on isoprenylation of signal peptides, including Ras, Rho and related G-proteins.