The Cauvery river basin in southern India: major challenges and possible solutions in the 21st century

India is facing major challenges in its water resources management (WRM) sector. Water shortages are attributed to issues such as an explosion in population, rapid urbanization and industrialization, environmental degradation and inefficient water use, all aggravated by changing climate and its impacts on demand, supply and water quality. This paper focuses on the contemporary and future situation in the Cauvery river basin in Southern India, shared by different states, predominantly Karnataka and Tamil Nadu. As water issues largely fall under the authority of the states, inter-state water disputes have a long tradition in the Cauvery river basin. Future changes in precipitation during the two monsoon seasons will only increase these tensions. Both states depend on the arrival of these monsoon rains to water their crops and to replenish the groundwater. The paper identifies the major challenges and general possible solutions for sustainable WRM within the river basin. It synthesises the relevant literature, describes practices that should be addressed in the scope of integrated WRM--including water availability increase and demand management--and stresses the need for further quantitative analyses.

All-optical steering of laser-wakefield-accelerated electron beams

We investigate the influence of a tilted laser-pulse-intensity front on laser-wakefield acceleration. Such asymmetric light pulses may be exploited to obtain control over the electron-bunch-pointing direction and in our case allowed for reproducible electron-beam steering in an all-optical way within an 8 mrad opening window with respect to the initial laser axis. We also discovered evidence of collective electron-betatron oscillations due to off-axis electron injection into the wakefield induced by a pulse-front tilt. These findings are supported by 3D particle-in-cell simulations.

Acute haemodynamic effects of a hypertonic saline/dextran solution in stable patients with severe sepsis

OBJECTIVE

To study the haemodynamic effects of a hypertonic saline/dextran solution compared with a normal saline solution in patients with severe sepsis.

DESIGN

Prospective double blind and control-randomised study.

SETTING

Adult intensive care unit in a university hospital.

PATIENTS

Twenty-nine patients with sepsis with a pulmonary artery occlusion pressure (PAOP) lower than 12 mmHg.

INTERVENTIONS

Patients were randomised to receive 250 ml of blinded solutions of either normal saline (SS group, n=16) or hypertonic saline (NaCl 7.5%)/dextran 70 8% (HSS group, n=13) solutions.

MEASUREMENTS AND RESULTS

Haemodynamic, blood gas, and sodium data were collected at the following time points: baseline, 30 min, 60 min, 120 min, and 180 min. PAOP was higher in the HSS group at 30 min (10.7+/-3.2 mmHg vs 6.8+/-3.2 mmHg) and 60 min (10.3+/-3 mmHg vs 7.4+/-2.9 mmHg); P<0.05. The cardiac index increased in the HSS group and it was greater than the SS group at 30 min (6.5+/-4.7 l min(-1) m(-2) vs 3.8+/-3.4 l min(-1) m(-2)), 60 min (4.9+/-4.5 l min(-1) m(-2) vs 3.7+/-3.3 l min(-1) m(-2)), and 120 min (5.0+/-4.3 l min(-1) m(-2) vs 4.1+/-3.4 l min(-1) m(-2)); P<0.05. The stroke volume index followed a comparable course and it was higher at 30 min [53.6(39.2-62.8) ml m(-2) vs 35.6(31.2-49.2) ml m(-2)] and 60 min [46.8(39.7-56.6) ml m(-2) vs 33.9(32.2-47.7) ml m(-2)]; P<0.05. Systemic vascular resistance decreased in the HSS group and became significantly lower at 30 min (824+/-277 dyne s(-1) cm(-5) m(-2) vs 1139+/-245 dyne s(-1) cm(-5) m(-2)), 60 min (921+/-256 dyne s(-1) cm(-5) m(-2) vs 1246+/-308 dyne s(-1) cm(-5) m(-2)), and 120 min (925+/-226 dyne s(-1) cm(-5) m(-2) vs 1269+/-494 dyne s(-1) cm(-5) m(-2)). Sodium levels increased in the HSS group (P=0.056) and were higher than in the SS group at 30 min (145+/-3 mEq l(-1)vs 137+/-7 mEq l(-1)), 60 min (143+/-4 mEq l(-1) vs 136+/-7 mEq l(-1)), 120 (142+/-5 mEq l(-1)vs 136+/-7 mEq l(-1)), and 180 min (142+/-5 mEq l(-1) vs 136+/-8 mEq l(-1)).

CONCLUSION

Hypertonic saline/dextran solution may improve cardiovascular performance in severe sepsis without significant side effects. The haemodynamic effect appears related mainly to a volume effect.

Blockade of the action of nitric oxide in human septic shock increases systemic vascular resistance and has detrimental effects on pulmonary function after a short infusion of methylene blue

To investigate the role of nitric oxide in human sepsis, ten patients with severe septic shock requiring vasoactive drug therapy and mechanical ventilation were enrolled in a prospective, open, non-randomized clinical trial to study the acute effects of methylene blue, an inhibitor of guanylate cyclase. Hemodynamic and metabolic variables were measured before and 20, 40, 60, and 120 min after the start of a 1-h intravenous infusion of 4 mg/kg of methylene blue. Methylene blue administration caused a progressive increase in mean arterial pressure (60 [55-70] to 70 [65-100] mmHg, median [25-75th percentiles]; P<0.05), systemic vascular resistance index (649 [479-1084] to 1066 [585-1356] dyne s-1 cm-5 m-2; P<0.05) and the left ventricular stroke work index (35 [27-47] to 38 [32-56] g m-1 m-2; P<0.05) from baseline to 60 min. The pulmonary vascular resistance index increased from 150 [83-207] to 186 [121-367] dyne s-1 cm-5 m-2 after 20 min (P<0.05). Mixed venous saturation decreased from 65 [56-76] to 63 [55-69]% (P<0.05) after 60 min. The PaO2/FiO2 ratio decreased from 168 [131-215] to 132 [109-156] mmHg (P<0.05) after 40 min. Arterial lactate concentration decreased from 5.1 +/- 2.9 to 4.5 +/- 2.1 mmol/l, mean +/- SD (P<0.05) after 60 min. Heart rate, cardiac filling pressures, cardiac output, oxygen delivery and consumption did not change. Methylene blue administration was safe and no adverse effect was observed. In severe human septic shock, a short infusion of methylene blue increases systemic vascular resistance and may improve myocardial function. Although there was a reduction in blood lactate concentration, this was not explained by an improvement in tissue oxygenation, since overall oxygen availability did not change. However, there was a significant increase in pulmonary vascular tone and a deterioration in gas exchange. Further studies are needed to demonstrate if nitric oxide blockade with methylene blue can be safe for patients with septic shock and, particularly, if it has an effect on pulmonary function.