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Biomedical subjects

R A Saraiva

Publications and source records attributed to R A Saraiva.

15 recordsLinked to original sources
PubMed2001

The effect of nitrous oxide on the inhibition of somatosensory evoked potentials by sevoflurane in children.

Inhalational anaesthetics inhibit somatosensory evoked potentials. The present study examined the effect of nitrous oxide in anaesthetic mixture with sevoflurane on the somatosensory evoked potential in children. Forty-five patients aged between 6 months and 6 years undergoing club foot surgery were studied to verify the influence of sevoflurane alone (21 patients) and sevoflurane with nitrous oxide (24 patients) on the somatosensory evoked potential. Fractional inspired concentration of nitrous oxide and fractional end-tidal (alveolar) sevoflurane were measured to estimate the multiples and submultiples of the minimal alveolar concentration (age corrected). The somatosensory evoked potential signals were obtained by stimulation of the median nerve. Nitrous oxide (FI = 0.63 +/- 2.5) with sevoflurane caused more reduction in the amplitude of somatosensory evoked potential waves and a greater increase in the latency of somatosensory evoked potential waves in comparison with sevoflurane alone. The results show that it is possible to obtain the inhibition of somatosensory evoked potential with smaller concentrations of sevoflurane, when it is used with nitrous oxide.

Anesthetics, Combined↗
PubMed1984

Closed circuit anesthesia in infants and children.

A closed-system low-flow technique with enflurane, halothane, or isoflurane as the sole anesthetic was used in three groups of ten children each. Anesthesia was induced by injection into the expiratory limb of a priming standard dose of the liquid anesthetic, followed by additional doses at 15, 30, 60, and 90 sec, and 2, 3, and 4 min. Further injections following the "square root of time" sequence were used for maintenance. Volumes of anesthetics used averaged 3.7 +/- 1.1 ml for enflurane, 2.3 +/- 1.1 ml for halothane, and 3.0 +/- 0.9 ml for isoflurane. These volumes were higher than predicted on theoretical grounds, as was the frequency with which anesthetics had to be injected. Closed-system low-flow anesthesia is a practical, economical, and nonpolluting technique in pediatric patients. Complications associated with isoflurane suggest, however, that isoflurane is not as satisfactory as enflurane or halothane when using this technique in infants and children.

Anesthesia, Inhalation↗
PubMed1978

Effect of undernutrition on uptake and distribution of i.v. anaesthetic agents. A study in mice.

The uptake and distribution of two i.v. anaesthetics agents, thiopentone and Althesin, were studied in mice with normal and subnormal nutritional states. The results show that, following the administration of thiopentone, the induction time was signficantly shorter, and that the sleeping time was significantly longer following the administration of Althesin and thiopentone in mice that have low net protein utilization, and decreased total and dry body mass. The increase in the sleeping time in these undernourished mice was 2.2 times greater for Althesin and 4.0 times greater for thiopentone when compared with well-nourished mice.

Alfaxalone Alfadolone Mixture↗
PubMed1977

Halothane solubility in human blood.

In a study of the influence of nutritional state on halothane anaesthesia, results were obtained which showed how the blood/gas partition coefficient for halothane varied with blood chemistry in 20 patients undergoing elective surgery. For each patient the partition coefficient lambda was measured by equilibration at 37 degrees C of a blood sample with a 1% halothane in 5% carbon dioxide in air mixture, followed by chemical extraction and estimation of the halothane content by gas chromatography. The haematocrit and haemoglobin, serum albumin, total protein, triglyceride and cholesterol concentrations were measured by routine laboratory methods. Regressions were sought of lambda on each of these, and on the globulin concentration and the ratios of albumin: globulin and albumin: total protein, deduced from these determinations. The only statistically significant regression (P = 0.0004) was that of lambda on the serum triglyceride concentration (T) (mmol/litre): lambda = 1.83 + 0.424T. The dependence of lambda on haemoglobin concentration was not statistically significant, but the slope of the regression was consistent with those of previous investigators. The regressions of lambda, corrected to the mean triglyceride concentration, on the ratios of albumin: globulin and albumin: total protein were not statistically significant but were not significantly different from an earlier reported result.

Anesthesia, Inhalation↗
PubMed1977

Adiposity and the pharmacokinetics of halothane. The effect of adiposity on the maintenance of and recovery from halothane anaesthesia.

Thirty fit patients (15-70 years, 46-98 kg) undergoing body-surface operations were selected to include a wide range of adiposity (12-45% of total body weight estimated from measurements of skinfold thickness). They were anaesthetized with halothane and 70% N2O in O2. From measurements of total ventilation (ml min-1 kg-1) and of halothane concentrations in inspired (F1) end-tidal (FE') and 'mixed-spill' (FS) gases, the following parameters were calculated for 5-min intervals from 20 to 40 min after induction; the rate of uptake of halothane per percent inspired concentration (Vha1 ml min-1%-1) and the degree of equilibrium achieved with the inspired concentration, calculated as FE'/F1 expressed as a percentage. Multiple-regression analysis of the results for 19 patients, taking account of the effects of body fat, ventilation, age, and the blood-gas partition coefficient lambda of halothane for the individual patient, showed that Vha1 increased with adiposity (b=0-375, P=0-0019), and with ventilation (b=0-054, P=0-09) but decreased with increasing age (b=-0-258, P=0-006). The time intervals between the end of the anaesthetic and the achievement of four defined levels of recovery (response to painful stimulus obedience to a simple command, response to a question, orientation in time and space), were recorded. Multiple-regression analysis showed that recovery time increased with addiposity, duration of administration and end-tidal concentration at the end of the administration, and decreased with increasing age. All four effects were statistically non-significant at the first levels of recovery but all increased at the later levels and all eventually became significant.

Adolescent↗