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Biomedical subjects

R A Gabel

Publications and source records attributed to R A Gabel.

At least 37 records · Page 2Linked to original sources
PubMed1984

Segmental levels of anaesthesia following the extradural injection of 0.75% bupivacaine at different lumbar spaces in elderly patients.

Segmental anaesthesia levels were determined in 80 elderly patients following the extradural injection of 0.75% bupivacaine 15 ml at four separate lumbar interspaces. Mean levels were T11 in the L5-S1 group, T7 in the L4-5, T5 in L3-4 and T3 in the L2-3 group (P less than 0.001). Varying the lumbar interspace at which the extradural anaesthesia is performed is recommended as a means of adjusting the levels of anaesthesia for different surgical procedures.

Abdomen↗
PubMed1984

Hemodynamic effects of weight reduction in the obese rat.

The effect of defined increments of weight loss on hemodynamics has been investigated in conscious, unrestrained, spontaneously obese rats. Obese rats were subjected to a calorically restricted diet and were used for experimentation on achieving a 10, 20, or 30% reduction in body weight. After monitoring resting blood pressure and heart rate, radioactive microspheres were infused for determination of blood flow distribution. Of 10 organs sample, only heart, liver, kidneys, and 2 adipose tissue depots exhibited significant decreases in weight associated with body weight reduction. Mean arterial blood pressure remained unchanged, while stroke volume, left ventricular work, and cardiac output decreased significantly. Blood flow decreased to kidneys, testes, and adipose tissue through a 30% reduction in body weight, but the fractional distribution of cardiac output decreased only to adipose tissue. Therefore the large decreases in renal and adipose tissue blood flow during weight reduction may contribute to the associated decrease in cardiac output. Of those vascular beds examined, however, both absolute and relative blood flow decreased only to adipose tissue, thus denoting the influence of fat mass on hemodynamics during obesity.

Animals↗
PubMed1984

Strength and cycle time of high-altitude ventilatory patterns in unacclimatized humans.

Respiration was monitored with magnetometers in 12 healthy supine young adults at sea level and in an altitude chamber at simulated high altitudes of 8,000, 9,000, 11,000, and 14,000 ft. Periodic breathing that was strong enough to include apnea at the time of minimum ventilation was seen in all subjects at high altitude. Cycle time of periodic breathing ranged from 12 to 34 s. On average across the population the incidence of periodic breathing increased with altitude. Cycle time of the periodic pattern increased as strength of the pattern increased. After normalizing to a standard pattern strength, cycle time decreased as altitude increased. The study included two series of experiments, the second occurring 3 wk after the first and involving seven of the same subjects. The standard cycle time at 14,000 ft for each subject in the second series was the same as in the first series to within, on the average, 6%. Each subject studied at 11,000 ft in both series reproduced his cycle time to within, on the average, 9%. The variation of standard cycle time for a given subject is less than the variation across the population, indicating characteristic cycle times for some individuals (one-way analysis of variance, P less than 0.025).

Acclimatization↗
PubMed1984

Adrenergic blockade does not change ventilatory response to CO2 in awake resting goats.

Although adrenergic agonists increase resting ventilation and responsiveness to CO2, there are conflicting data about the effect of adrenergic blockade on ventilatory responses. In this study, we investigated the effect of alpha- or beta-adrenergic blockade on the response to hyperoxic CO2 rebreathing in awake goats. In 5 goats, studied before and after intravenous administration of phentolamine or propranolol, there was no difference (compared to control studies) in the mean slope, x-intercept, or ventilation at end-tidal PCO2 (PETCO2) = 70 torr for the CO2 response curves after either drug. When mean inspiratory flow rate (VT/Ti) was plotted against PETCO2, there was also no change in these measurements after propranolol. After phentolamine, there was a slight decrease in the slope and x-intercept, but no change in VT/Ti at PETCO2 = 70 torr. We conclude that acute administration of alpha- or beta-adrenergic blockers does not affect ventilatory response to CO2 inhalation in goats, and suggest that adrenergic activity is not an important modulating influence for CO2 responsiveness in this species.

Animals↗
PubMed1983

Acclimatization to high altitude in goats with ablated carotid bodies.

In awake goats with ablated carotid bodies, we studied resting pulmonary ventilation, CO2 production, composition of arterial blood and cerebrospinal fluid (CSF), and ventilatory responsiveness to hyperoxic CO2 rebreathing at sea level (SL) and after 3 days at simulated high altitude (HA) (PB 446 +/- 5 Torr, equivalent to 4,300 m). At HA, resting pulmonary ventilation was increased, resulting in marked hypocapnia with appropriate base deficit in blood plasma; CSF became more alkaline; CO2-response curves were shifted to lower PCO2 levels, and their slopes were steeper than at SL. Although these changes in regulation of respiration were not demonstrably different from those seen after normal acclimatization to HA with carotid bodies intact, the mechanisms of their initiation and development are probably different.

Acclimatization↗
PubMed1983

Reversal of arterial-to-expired CO2 partial pressure differences during rebreathing in goats.

Whether CO2 partial pressure (PCO2) in expired gas may exceed that in arterial blood has been controversial. We measured arterial PCO2 (Paco2) and end-tidal PCO2 (PETco2) in four awake goats during air breathing and during hyperoxic CO2 rebreathing in various conditions of acid-base balance. During air breathing, Paco2 was slightly higher than PETco2; i.e., the mean (+/- SE) difference, Paco2 - PETco2, was positive by + 2.36 +/- 0.53 Torr (P less than 0.001). In contrast, during CO2 rebreathing with the same techniques of measurement, this difference was always negative (mean +/- SE = -11.63 +/- 0.22 Torr, P less than 0.001), and it widened as Paco2 increased with rebreathing. Magnitude of the negative difference during rebreathing was too great to be accounted for by incorrect assumptions or measurement error, even if reasonable contributions from all known sources of error were concurrently invoked. We conclude that during hyperoxic CO2 rebreathing in goats, PETco2 exceeds Paco2.

Animals↗
PubMed1983

Variation in PCO2 between arterial blood and peak expired gas during anesthesia.

Arterial PCO2 (PaCO2) can be continuously and noninvasively estimated by monitoring peak expired CO2 tension (PpeCO2). The practice of calibrating the estimate by an initial measurement of PaCO2 assumes that the difference in PCO2 tension between arterial blood and expired gas P(a-pe)CO2 remains constant. We examined the stability of P(a-pe)CO2 during anesthesia in 15 patients undergoing major surgery. Mean P(a-pe)CO2 values ranged from 0.8-7.9 torr with maximum P(a-pe)CO2 values ranging from 4.5-13.0 torr. Calibration of P(a-pe)CO2 based on a single initial measurement of PaCO2 often over- or underestimated PaCO2. Mean estimated PaCO2 from calibrated P(a-pe)CO2 varied from -7.9-6.4 torr with extreme estimates of -12.8-12.3 torr. No consistent correlation was shown between P(a-pe)CO2 and duration of anesthesia, variations in ventilation, blood pressure, blood-gas tensions, PpeCO2 or temperature. We conclude that estimation of PaCO2 by monitoring PpeCO2 is not invariably reliable.

Adult↗
PubMed1980

The case for abandonment of explosive anesthetic agents.

The use of inflammable anesthetics in the United States has been debated widely over the past several years. Those in favor of continued use of these agents argue for educational use, professional freedom, pharmacologic safety, and the need to retain an option. Those in favor of a ban on such agents cite the lack of demonstrated pharmacologic advantage, diminishing physician expertise, risk of fire, and cost. The use of inflammable anesthetics has declined markedly over the past 15 years; in 1978, only 15 per cent of American hospitals were reportedly using them. However, we estimate that the use of inflammable anesthetics adds approximately $9.4 million to the annual cost of surgical care. As their use declines further, the cost per patient increases because most of the costs are fixed. We advocate a ban on inflammable anesthetics. Without definitive action on the part of policy makers, the use of these agents is likely to continue at a very low, and hence a relatively expensive, rate.

Anesthesia, Inhalation↗
PubMed1980

Algorithms for calculating and correcting blood-gas and acid-base variables.

This is a review of the origins, derivations, and 'fidelity' of available equations for correcting PO2, PCO2, and pH for temperature, and for estimating blood-gas and acid-base variables from measured values: 1. Oxygen saturation (SO2) from PO2, PCO2, pH, and body temperature (T). 2. Oxygen concentration (CO2) from SO2, PO2, and hemoglobin concentration (Hb). 3. Base excess (BE) from pH, PCO2, and Hb. 4. 'In vivo BE' (BE3) from pH and PCO2. 5. 'Compensated BE3' (BEC) from PCO2. 6. Bicarbonate ([HCO3-]) and carbon dioxide concentrations (CCO2) from pH and PCO2. PHysiologic considerations are emphasized, with mathematical background when it contributes to understanding. Algorithms are variously compared with their graphic counterparts, with the data from which they were derived, and with each other.

Acid-Base Equilibrium↗
PubMed1979

Composition of cerebral fluids in goats adapted to high altitude.

We explored the ionic composition of cerebral interstitial fluid (cISF) in six unanesthetized goats at sea level (SL) and again after 5 days at a simulated high altitude (HA) of 4,300 m. By measuring net transependymal fluxes of HCO3-, Cl-, and lactate during ventriculocisternal perfusions with lactate-free artificial cerebrospinal fluid (CSF) with various [HCO3-] and [Cl-], we determined [HCO3-] and [Cl-] in the inflowing perfusate that produced zero flux, which are estimates of the concentrations of these ions in cISF. Ventilatory acclimatization to HA was established in the goats with alkaline shift in cisternal CSF pH. At SL zero flux of HCO3- and of Cl- occurred when [HCO3-] and [Cl-] in the perfusate were equal to those in CSF. At HA Cl- flux again was zero when [Cl-] in perfusate and in the goat's own CSF were equal; however, for HCO3-, zero flux occurred at HA when [HCO3-] in perfusate was significantly lower than in CSF. Mean transependymal washout of lactate was 16 times larger at HA than at SL. We conclude that at SL [HCO3-] and [Cl-] in CSF were the same as in cISF. In goats adapted to HA [Cl-] in cISF and in CSF were again equal, whereas [HCO3-] in cISF was lower and [lactate] presumably higher than in CSF. The fluid surrounding the central chemoreceptors appears to be more acidic in goats acclimatized to HA than at SL despite the alkalosis in cisternal CSF. This may contribute to ventilatory acclimatization to HA.

Acclimatization↗
PubMed1977

Prediction of PO2 from SO2 using the standard oxygen hemoglobin equilibrium curve.

We have fitted polynomial equations to three major segments of the standard oxygen hemoglobin equilibrium curve (OHEC) using oxygen saturation (SO2) rather than oxygen tension (PO2) as the independent variable. Hill's transformation contributes substantially to the very small residual errors of PO2, less than 0.21 Torr for all points. This characterization of the OHEC is more precise, and for certain applications more conveniently used than other available equations.

Hemoglobins↗