Rapid electrochemical quantification of trace Hg2+ using a hairpin DNA probe and quantum dot modified screen-printed gold electrodes

Rapid, simple, sensitive and specific approaches for mercury(ii) (Hg²⁺) detection are essential for toxicology assessment, environmental protection, food analysis and human health. In this study, a ratiometric hairpin DNA probe based electrochemical biosensor, which relies on hairpin DNA probes conjugated with water-soluble and carboxyl functionalized quaternary Zn–Ag–In–S quantum dot (QD) on screen-printed gold electrodes (SPGE), referred to as the HP-QDs-SPGE electrochemical biosensor in this study, was developed for Hg²⁺ detection. Based on the “turn-off” reaction of a hairpin DNA probe binding with a mismatched target and Hg²⁺ through the formation of T–Hg²⁺–T coordination, the HP-QDs-SPGE electrochemical biosensor can rapidly quantify trace Hg²⁺ with high ultrasensitivity, specificity, repeatability and reproducibility. The conformational change of the hairpin DNA probe caused a significant decrease in electrochemical intensity, which could be used for the quantification of Hg²⁺. The linear dynamic range and high sensitivity of the HP-QDs-SPGE electrochemical biosensor for the detection of Hg²⁺ was studied in vitro, with a broad linear dynamic range of 10 pM to 1 μM and detection limits of 0.11 pM. In particular, this HP-QDs-SPGE electrochemical biosensor showed excellent selectivity toward Hg²⁺ ions in the presence of other metal ions. More importantly, this biosensor has been successfully used to detect Hg²⁺ in deionized water, tap water, groundwater and urine samples with good recovery rate and small relative standard deviations. In summary, the developed HP-QDs-SPGE electrochemical biosensor exhibited promising potential for further applications in on-site analysis.

A ratiometric hairpin DNA probe based electrochemical biosensor, which relies on hairpin DNA probes conjugated with water-soluble and carboxyl functionalized quantum dot on screen-printed gold electrodes, was developed for Hg²⁺ detection.     

Psychoonkologie

In recent years, the psychosocial stresses and sequelae of cancer have been increasingly focused on by the public interest. Psychosocial counseling and interventions are now an integrated and essential part of modern cancer therapy, although in Germany a large gap exists between the scientific state of the art and real-world psychosocial care. Psychooncology is a young discipline dealing with the intercorrelations of physical, psychological, and social factors in the etiology and course of cancer. Based on many scientific studies, specific psychosocial interventions regarding prevention, diagnosis, treatment, and aftercare have been developed to support cancer patients. This article gives an overview of the young field of psychooncology, focusing on its development during the last decades.     

Effects of the sitting position on the distribution of blood volume in patients undergoing neurosurgical procedures

The use of the sitting position in neurosurgery is often associated with decreased arterial pressure (MAP) and stroke volume index (SVI). A shift in blood from the intra- to the extrathoracic compartment may be responsible for this cardiovascular response. However, little is known of the amount of shift in blood volume after transfer from the supine to the sitting position. Therefore, we measured simultaneously changes in intrathoracic blood volume (ITBV) caused by a change in body position in anaesthetized patients. Measurements of cardiac index (CI), ITBV, pulmonary (PBV) and total circulating (TBVcirc) blood volumes were performed in the supine and sitting position. CI, ITBV, PBV and TBVcirc were measured using a thermodye dilution technique. Fluid input was restricted to 14 ml kg-1 before induction of anaesthesia. Change in body position caused a significant decrease in ITBV and was accompanied by a significant decrease in CI, SVI and MAP. Changes in ITBV correlated (r = 0.78) with changes in SVI. Thus a change in blood volume distribution between the intra- and extrathoracic compartment occurred after a change from the supine to the sitting position. Indicator dilution enables quantification of this shift and may be helpful in guiding fluid therapy in selected patients.      

Experimentelle Untersuchung zur Effektivität verschiedener Infusions- und Blutwärmeverfahren

Heat loses during surgery occur mainly to the environment and due to infusions and irrigations. Infusions given at room temperature account for a great deal of the total heat deficit during major operations, e.g., the infusion of 53?ml/kg 20°?C fluid leads to a loss of 1°?C in mean body temperature. Hence, heating i.v. fluids will add to the effect of other measures aimed at reducing heat loss to the environment. We investigated the efficacy of different warming methods for i.v. fluids in an experimental model by measuring the temperature at the end of the delivery line. Methods. The following in-line warmers were studied: Hotline HL-90 and System H-250/heat exchanger D-50 (Level 1 Technologies, Marshfield, USA), Astotherm IFT 260 (Stihler Elektronic GmbH, Stuttgart, Germany), RSLB 30 H Gamida (Productions Hospitalieres Francaises, Eaubonne, France), Bair Hugger 241/Modell 500 Prototype (Augustine Medical, Eden Prairie, USA). They were compared with prewarming infusions (39°?C) only using the Clinitherm S (Labor Technik Barkey GmbH, Bielefeld, Germany) and prewarming with “active insulation” of the delivery line using the Autotherm/Autoline system (Labor Technik Barkey GmbH, Bielefeld, Germany). We investigated the influence of four variables on the efficacy of warming: (1) flow rate (50–15,000 ml/h); (2) ambient temperature (20°?C and 25°?C); (3) infusion bag temperature (6°?C, 20°?C, and 39°?C); and (4) length of infusion system downstream from the heat exchanger. Fluid temperatures were measured using thermistors of 1?mm diameter (Modell YSI 520, Yellow Springs Instruments Co., Yellow Springs, USA) incorporated into 3-way stopcocks. Temperatures were recorded using Hellige temperature monitors (Hellige GmbH, Freiburg im Breisgau, Germany) and the signals were collected at 10?Hz through an AD converter and averaged over 1?min. Flows were calculated by timed collection into calibrated cylinders; 10 to 12 different flow rates were taken to define one temperature/flow plot. Effective warming was defined as a temperature?>33°?C at the end of the infusion line. Results. At high flow rates (>2,500?ml/h) using 20°?C fluids at 20°?C ambient temperature, the H-250/D-50 system gave the highest temperatures throughout the range and showed effective warming from 1,300?ml/h on over the entire range tested (35°?C at 17,000?ml/h) compared to the RSLB 30 H Gamida system (3,000–18,000?ml/h) (Fig. 2). This difference in performance was almost abolished with fluids at 6°?C (Fig. 4). Similar efficacy could be reached by using prewarmed infusions that gave effective warming at?>2,000?ml/h and reached 39°?C at 13,000?ml/h. Prewarmed infusions could be used effectively down to?>80?ml/h applying “active insulation” (Autotherm/Autoline) to the whole infusion system. The Hotline HL-90 (50–4,700?ml/h) appeared to be the most effective in-line warmer in the low (<250?ml/h) and middle (250–2,500?ml/h) flow range, followed by the Astotherm IFT 260 (400–4,000?ml/h), but only if used with a length of 40?cm down-stream from the heat exchanger (Fig. 1). Increasing this distance to 145?cm markedly reduced its efficacy below the range of 2,000?ml/min (1,200–3,000?ml/h) (Fig. 5). The Bair Hugger 241 Prototype showed a narrow effective range (700–1,300?ml/h) that could be extended beyond 1,300?ml/h by the use of prewarmed infusions (Figs. 1 and 3). The performance for 6°?C solutions and ambient temperatures of 25°?C are given in Fig. 4 and Table 1. Conclusions. The importance of infusion warming increases with the amount of fluid given. In general, the infusion bag temperature only influenced the efficacy of in-line warmers within the high-flow range, challenging the performance of the heat exchanger. The length of uninsulated i.v. line downstream from the heat exchanger influenced the efficacy within the low- and middle-flow range, as did the room temperature. Prewarmed solutions can be infused very effectively within the high-flow range. This efficiency can be preserved down to the low-flow range by using “active insulation” of the infusion system. In-line warming is essential for emergency and rapid massive transfusions.     

Influence of intra-aortic balloon pumping on cerebral blood flow pattern in patients after cardiac surgery

BACKGROUND AND OBJECTIVE: The effects of intra-aortic balloon pumping (IABP) on cerebral perfusion are still a matter of debate. End-diastolic reversal of blood flow in cerebral arteries has been observed in a small number of patients. We prospectively investigated the incidence and the amount of transient cerebral artery blood flow reversal during balloon pumping in patients recovering from cardiac surgery. METHODS: In 23 patients receiving IABP support, blood flow velocities in the right middle cerebral artery were assessed by transcranial Doppler-sonography. Additionally, systemic haemodynamics were monitored. In each patient, measurements were performed at three different pump settings: without support, assist ratio 1 : 1 and assist ratio 1 : 2. RESULTS: In 8 of 23 patients, balloon pumping caused a transient diastolic reversal of blood flow in the middle cerebral artery during balloon deflation. Antegrade mean flow velocity in the middle cerebral artery significantly increased from 57 +/- 27 to 61 +/- 26 (assist ratio 1 : 1) and 61 +/- 29 cm s(-1) (assist ratio 1 : 2) (P < 0.05). Taking transient blood flow reversal into account, net mean flow velocity did not increase with balloon pump support. Systemic haemodynamic parameters remained unchanged. CONCLUSION: Left ventricular support with IABP significantly changed flow patterns in basal cerebral arteries of our patients. In 35% of patients, support resulted in a transient reversal of intracranial blood flow which counterbalanced a slight increase in mean antegrade flow.     

Differences among forced-air warming systems with upper body blankets are small. A randomized trial for heat transfer in volunteers

BACKGROUND: Forced-air warming is known as an effective procedure in prevention and treatment of perioperative hypothermia. Significant differences have been described between forced-air warming systems in combination with full body blankets. We investigated four forced-air warming systems in combination with upper body blankets for existing differences in heat transfer. METHODS: After approval of the local Ethics Committee and written informed consent, four forced-air warming systems combined with upper body blankets were investigated in a randomized cross-over trial on six healthy volunteers: (1) BairHugger trade mark 505 and Upper Body Blanket 520, Augustine Medical; (2) ThermaCare trade mark TC 3003, Gaymar trade mark and Optisan trade mark Upper Body Blanket, Brinkhaus; (3) WarmAir trade mark 134 and FilteredFlow trade mark Upper Body Blanket, CSZ; and (4) WarmTouch trade mark 5800 and CareDrape trade mark Upper Body Blanket, Mallinckrodt. Heat transfer from the blanket to the body surface was measured with 11 calibrated heat flux transducers (HFTs) with integrated thermistors on the upper body. Additionally, the blanket temperature was measured 1 cm above the HFT. After a preparation time of 60 min measurements were started for 20 min. Mean values were calculated over 20 min. The t-test for matched pairs with Bonferroni-Holm-correcture for multiple testing was used for statistical evaluation at a P-level of 0.05. The values are presented as mean+/-SD. RESULTS: The WarmTouch trade mark blower with the CareDrape trade mark blanket obtained the best heat flux (17.0+/-3.5 W). The BairHugger trade mark system gave the lowest heat transfer (8.1+/-1.1 W). The heat transfer of the ThermaCare trade mark system and WarmAir trade mark systems were intermediate with 14.3+/-2.1 W and 11.3+/-1.0 W. CONCLUSIONS: Based on an estimated heat loss from the covered area of 38 W the heat balance is changed by 46.1 W to 55 W by forced-air warming systems with upper body blankets. Although the differences in heat transfer are significant, the clinical relevance of this difference is small.     

Severe accidental hypothermia: rewarming strategy using a veno-venous bypass system and a convective air warmer

Objective: To study a rewarming strategy for patients with severe accidental hypothermia using a simple veno-venous bypass in combination with a convective air warmer. Setting: Eighteen beds in a university hospital intensive care unit. Patients: Four adults admitted with a core temperature less than 30 °C. Hypothermia was caused by alcoholic intoxication in three patients and by drug overdose in one patient. Measurements and main results: All patients were rewarmed by a veno-venous bypass and in three cases a convective air warmer was also used. At a bypass flow rate of 100–300 ml/min the mean increase in core temperature was 1.15 °C/h (Range: 1.1–1.2 °C/h). One patient died 2 days after rewarming as a consequence of a reactivated pancreatitis. The other three patients survived without neurological sequelae. Conclusion: This rewarming technique seems safe and effective and allowed the controlled rewarming of our patients who suffered from severe accidental hypothermia Received: 15 September 1998 Final revision received: 4 January 1999 Accepted: 11 February 1999