Respiration and heart rate complexity: Effects of age and gender assessed by band-limited transfer entropy

Aging and disease are accompanied with a reduction of complex variability in the temporal patterns of heart rate. This reduction has been attributed to a break down of the underlying regulatory feedback mechanisms that maintain a homeodynamic state. Previous work has established the utility of entropy as an index of disorder, for quantification of changes in heart rate complexity. However, questions remain regarding the origin of heart rate complexity and the mechanisms involved in its reduction with aging and disease. In this work we use a newly developed technique based on the concept of band-limited transfer entropy to assess the aging-related changes in contribution of respiration and blood pressure to entropy of heart rate at different frequency bands. Noninvasive measurements of heart beat interval, respiration, and systolic blood pressure were recorded from 20 young (21–34 years) and 20 older (68–85 years) healthy adults. Band-limited transfer entropy analysis revealed a reduction in high-frequency contribution of respiration to heart rate complexity (p < 0.001) with normal aging, particularly in men. These results have the potential for dissecting the relative contributions of respiration and blood pressure-related reflexes to heart rate complexity and their degeneration with normal aging.     

Microstructure of veneered zirconia after surface treatments: A TEM study

Objective

Clinical studies reveal that veneer chipping is one major problem associated with zirconia based dental restorations, the underlying mechanisms being still investigated. We semi-quantitatively analyzed the effects of different surface treatments (thermal etching, 35/105 μm sandblasting and coarse bur drilling (150 μm)) on the microstructure of a zirconia veneered dental ceramic.

Methods

The relative monoclinic content on zirconia surfaces was determined using X-ray diffraction (XRD). The microstructure at the zirconia–veneer interface has thereafter been investigated using transmission electron microscopy (TEM). Selected area electron diffraction (SAED) was used to qualitatively assess the depth of the stress-induced phase transformation.

Results

Sandblasting or bur drilling significantly roughened the zirconia surface. A reverse transformation of already transformed monoclinic zirconia grains back into the tetragonal polymorph has been observed after thermal veneering treatment. In TEM, the mechanically treated samples revealed a highly damaged area of 1–3 μm from the interface. The presence of monoclinic phase in veneered zirconia samples has been observed in SAED up to depths of 4 μm (35 μm sandblasted), 11 μm (105 μm sandblasted) and 9 μm (150 μm diamond drilled) below the interface.

Significance

Regardless of the treatment protocol and produced roughness, the veneering ceramic perfectly sealed the zirconia surface. XRD showed an increased amount of monoclinic phase on the surface treated zirconia. However after thermal treatment, the monoclinic phase was re-transformed into the tetragonal polymorph. TEM/SAED analysis has found indication for a greater extend of the monoclinic transformation into the bulk zirconia compared to the treatment related defective zone depth.     

Subarachnoid haemorrhage WFNS grade V: is maximal treatment worthwhile?

Background

Aneurysmal subarachnoid haemorrhage (SAH) WFNS grade V is commonly known to be associated with high mortality and a very poor prognosis for survivors. Therefore, maximal invasive therapy is frequently delayed until any spontaneous improvement with or without an external ventricular drainage occurs. The aim of the study was to verify possible predictive factors and the probability of a favourable outcome in maximally treated patients.

Methods

One hundred and thirty-eight consecutive patients with WFNS grade V SAH were admitted between 03/2006 and 12/2010. Thirty-five patients died before aggressive therapy could proceed. One hundred and three patients received maximal treatment and were retrospectively evaluated. The outcome was assessed at discharge and in the follow-up with the Glasgow Outcome Scale. Univariate and multivariate linear regression models were performed to find predictors for an unfavourable outcome.

Results

Despite treatment, early mortality was 30 % (n?=?31). At discharge, the rate of both vegetative and severely disabled patients was 27 % (n?=?28). Favourable outcome at discharge was observed in 16 % (n?=?16) of cases, whereas in the follow-up it rose to 26 % (n?=?27). Multivariate full model regression identified intraventricular haematoma (IVH) and increasing age as independently predictive for poor outcome.

Conclusions

Despite treatment, initial mortality and severe disability remain high. Nevertheless, a favourable outcome was achieved in 26 % of aggressively treated patients, rendering the withdrawal of maximal therapy for WFNS grade V SAH patients unacceptable today. In cases of old patients with IVH, the indication for aggressive therapy should be put in place more carefully due to a very poor prognosis.     

High Infection Rate Outcomes in Long-bone Tumor Surgery with Endoprosthetic Reconstruction in Adults: A Systematic Review

Background

Limb salvage surgery (LSS) with endoprosthetic replacement is the most common method of reconstruction following bone tumor resection in the adult population. The risk of a postoperative infection developing is high when compared with conventional arthroplasty and there are no appropriate guidelines for antibiotic prophylaxis.

Questions/purposes

We sought to answer the following questions: (1) What is the overall risk of deep infection and the causative organism in lower-extremity long-bone tumor surgery with endoprosthetic reconstruction? (2) What antibiotic regimens are used with endoprosthetic reconstruction? (3) Is there a correlation between infection and either duration of postoperative antibiotics or sample size?

Methods

We conducted a systematic review of the literature for clinical studies that reported infection rates in adults with primary bony malignancies of the lower extremity treated with surgery and endoprosthetic reconstruction. The search included articles published in English between 1980 and July 2011.

Results

The systematic literature review yielded 48 studies reporting on a total of 4838 patients. The overall pooled weighted infection rate for lower-extremity LSS with endoprosthetic reconstruction was approximately 10% (95% CI, 8%–11%), with the most common causative organism reported to be Gram-positive bacteria in the majority of cases. The pooled weighted infection rate was 13% after short-term postoperative antibiotics and 8% after long-term postoperative antibiotics. There was no correlation between sample size and infection rate.

Conclusions

Infection rates of 10% are high when compared with rates for conventional arthroplasty. Our results suggest that long-term antibiotic prophylaxis decreases the risk of deep infection. However, the data should be interpreted with caution owing to the retrospective nature of the studies.     

Hypoxaemic rescue therapies in acute respiratory distress syndrome: Why,when, what and which one?

Acute respiratory distress syndrome (ARDS) is an inflammatory condition of the lungs which can result in refractory and life-threatening hypoxaemic respiratory failure. The risk factors for the development of ARDS are many but include trauma, multiple blood transfusions, burns and major surgery, therefore this condition is not uncommon in the severely injured patient. When ARDS is severe, high-inspired oxygen concentrations are frequently required to minimise hypoxaemia. In these situations clinicians commonly utilise interventions termed ‘hypoxaemic rescue therapies’ in an attempt to improve oxygenation, as without these, conventional mechanical ventilation can be associated with high mortality. However, their lack of efficacy on mortality when used prophylactically in generalised ARDS cohorts has resulted in their use being confined to clinical trials and the subset of ARDS patients with refractory hypoxaemia.     

Intraoperative electron radiation therapy as an important treatment modality in retroperitoneal sarcoma

Background

Local recurrence (LR) rates in patients with retroperitoneal sarcoma (RPS) are high, ranging from 40% to 80%, with no definitive studies describing the best way to administer radiation. Intraoperative electron beam radiation therapy (IOERT) provides a theoretical advantage for access to the tumor bed with reduced toxicity to surrounding structures. The goal of this study was to evaluate the role of IOERT in high-risk patients.

Methods

An institutional review board approved, single institution sarcoma database was queried to identify patients who received IOERT for treatment of RPS from 2/2001 to 1/2009. Data were analyzed using the Kaplan–Meier method, Cox regression, and Fisher Exact tests.

Results

Eighteen patients (median age 51 y, 25–76 y) underwent tumor resection with IOERT (median dose 1250 cGy) for primary (n = 13) and recurrent (n = 5) RPS. Seventeen patients received neoadjuvant radiotherapy. Eight high-grade and 10 low-grade tumors were identified. Median tumor size was 15 cm. Four patients died and two in the perioperative period. Median follow-up of survivors was 3.6 y. Five patients (31%) developed an LR in the irradiated field. Three patients with primary disease (25%) and two (50%) with recurrent disease developed an LR (P = 0.5). Four patients with high-grade tumors (57%) and one with a low-grade tumor (11%) developed an LR (P = 0.1). The 2- and 5-y OS rates were 100% and 72%. Two- and 5-y LR rates were 13% and 36%.

Conclusions

Using a multidisciplinary approach, we have achieved low LR rates in our high-risk patient population indicating that IOERT may play an important role in managing these patients.