Renal function and fluoride formation and excretion during enflurane anaesthesia

Fluoride in the drinking water of Nagaur tehsil of Nagaur District, Rajasthan, India

Fluoride concentration of groundwater samples from 100 villages of Nagaur tehsil was determined, 85 villages were found to have fluoride concentration more than 1.5 mg/L. The maximum fluoride concentration was recorded 6.6 mg/L in groundwater of Singhani village, while the minimum was recorded in Kurchhi village. As per the desirable and maximum permissible limit for fluoride in drinking water, determined by World Health Organization, the groundwater of about 85 villages of the studied sites is unfit for drinking purpose.

Intravenous fluid administration and urine output during radical neck surgery

This study examines perioperative urine output (UO) and hemodynamics in 24 patients who underwent radical head and neck surgery. The hypothesis tested was that "UO was not important in patients with normal renal function as long as hemodynamics were maintained." Intraoperatively, a "wet" group (13 patients) had generous amounts of intravenous (IV) fluid administered during surgery receiving 1,018 +/- 58 mL.h-1. The other "dry" group (11 patients) had fluids restricted to 426 +/- 23 mL.h-1. The intraoperative UOs for the wet and dry groups were 1.33 +/- 0.27 and 0.39 +/- 0.10 mL.kg-1 x h-1, respectively (p < 0.05). Postoperatively, the UOs for the wet and dry groups were 1.9 +/- 0.3 and 1.1 +/- 0.1 mL.kg-1 x h-1, respectively (p < 0.05). Perioperatively, there were no statistically significant differences between groups in systemic or pulmonary hemodynamics. Postoperatively, ordinary indices of renal function remained normal in both groups. We conclude that intraoperative oliguria due to moderate fluid restriction is not detrimental to renal outcome as long as systemic hemodynamics are maintained. Furthermore, not only does this relatively "dry" status not compromise hemodynamics, it affords the patient other benefits.

Anaesthesia for the patient with impaired renal function

Patients with renal disease are at risk of further deterioration of renal function and acute tubular necrosis when subjected to anaesthesia and surgery. Optimal fluid loading and careful selection of anaesthetic techniques and agents, appropriate monitoring and the use of mannitol and dopamine assist in the maintenance of renal blood flow and help preserve renal function in these patients. In association with renal failure, physiological changes in other systems result in reduced oxygen supply to the tissues, metabolic disturbances, impairment of the coagulation and immune defence mechanisms and an increased risk of cardiac and cerebrovascular catastrophe. Although many anaesthetic techniques including regional analgesia may be used successfully in these patients caution with most drugs, especially pethidine, phenoperidine, suxamethonium and all non-depolarising neuromuscular relaxants is recommended. Of the volatile anaesthetics currently available, halothane is the agent of choice. Oxygen therapy and close monitoring of cardiorespiratory function are necessary postoperatively.

Metabolic ability and enflurane defluorination in surgical patients

Antipyrine clearance and half-life, which are measures of the hepatic metabolic ability, were determined prior to anaesthesia in 14 surgical patients. The antipyrine results correlated neither with the highest serum fluoride concentrations nor with the fluoride excretion in urine following administration of enflurane. Enzyme induction may therefore have little influence on enflurane metabolism in man. Inorganic fluoride concentrations in serum and in excreted urine were determined following the exposure of a total of 21 surgical patients to measured doses of enflurane. In the group of 14 patients tested for metabolic ability, a mean dose of 0.4 end-tidal vol. % X h enflurane resulted in a mean peak serum fluoride concentration of 6.8 mumol/l (maximum 13.6 mumol/l) 2 h after enflurane exposure. In the material as a whole, the enflurane dose was positively correlated with both post-anaesthetic highest serum fluoride concentrations and the 24-h post-anaesthetic urine pH (P less than 0.01) as well as urinary volume and fluoride excretion in urine during that time. At a urinary pH below 5.0, the fluoride excretion was very low, while the highest excretions were associated with a urinary pH of about 7.0. Raising the patient's per- and post-anaesthetic urine pH and maintaining a good urinary output (which also tends to increase urine pH) may be enough to prevent accumulation of inorganic fluoride in the body following enflurane anaesthesia.

Renal fluoride excretion during and after enflurane anaesthesia: dependency on spontaneous urinary pH-variations

Renal function, fluoride formation and excretion were studied in seven patients during and after enflurane anaesthesia and surgery. The mean maximal plasma level of fluoride was 17.4 microM. It was reached 2 h after termination of anaesthesia. Pre-operatively, fraction fluoride clearance (CF/CIn) was 0.31. During anaesthesia and surgery it decreased to 0.10 and postoperatively rose to 0.55 and 0.77 during two consecutive measurement periods. There was a highly significant correlation (P less than 0.001) between this increase in CF/CIn and the simultaneous rise in urinary pH between the two periods (r = 0.91).