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Biomedical subjects

R T Geer

Publications and source records attributed to R T Geer.

At least 19 recordsLinked to original sources
PubMed1993

Cardiovascular stability with rapid intravenous infusion of ondansetron.

The acute cardiovascular effects of rapid iv administration of the antiemetic ondansetron, a selective serotonin (5-HT3) receptor antagonist were determined in a randomized, blinded, placebo-controlled study. Measurements of heart rate, blood pressure, oxygen saturation and respiratory rate were made preoperatively over a five-minute period which followed a two-minute infusion of the medication. Intraoperative and postoperative data were not collected. None of the variables recorded changed significantly during the infusion or in the observation period which followed. Within the limitations of this study, we detected no cardiovascular change in the five minutes between the end of the drug infusion and the induction of anaesthesia.

Adult↗
PubMed1986

A departmental policy addressing chemical substance abuse.

Substance abuse is a major socioeconomic problem. However, the ready availability of potent narcotic and sedative drugs probably constitutes a unique risk for anesthesiologists. Until recently, few anesthesia departments were prepared to recognize or safely manage afflicted colleagues. Because we felt it important to educate our staff and residents and to have a response mechanism established prior to the advent of a substance abuse problem, a departmental committee was formed to develop a Substance Abuse Policy. The policy has served to increase our general awareness and to direct our actions effectively when dealing with physician impairment. It is presented here in the belief that other departments might find it useful in tailoring their approach to this problem.

Anesthesiology↗
PubMed1985

Errors in measurement of oxygen uptake due to anesthetic gases.

Errors in measurement of exhaled gas volume, mixed expired oxygen and carbon dioxide concentrations, and inspired oxygen concentration and the presence of exhaled anesthetic agents cause errors in on-line calculated oxygen uptake that increase geometrically with increasing inspired oxygen concentration. No one has quantified the decrease in the magnitude of the error that might be realized if directly measured nitrogen concentration were included in the calculation. We used a computer model to evaluate this improvement, assuming an oxygen uptake of 200 ml/min and normal ventilatory parameters. Using a Monte Carlo technique, we generated 100 sets of data points, with random errors averaging 0.5% around the expected gas concentrations, and compared the accuracy of oxygen uptake calculated with and without inclusion of directly measured inspired and expired nitrogen concentrations. When the inspired oxygen fractions were 0.2, 0.5, and 0.8, the calculated oxygen uptakes +/- % standard deviation were 200 +/- 4.3, 200 +/- 12, and 196 +/- 21 when directly measured nitrogen was included versus 200 +/- 3.5, 196 +/- 16, and 205 +/- 71 when it was not. The procedure was repeated, assuming 50 ml/min of anesthetic excretion and the calculated oxygen uptakes were 200 +/- 4.6, 202 +/- 12, and 195 +/- 17 versus 212 +/- 3.8, 251 +/- 17, and 398 +/- 64. Including direct measurement of inhaled and exhaled concentrations of nitrogen or another insoluble inert tracer gas allows accurate measurement of oxygen uptake, even in the presence of exhaled anesthetic gases. It also decreases the error in oxygen uptake determination by a factor of nearly six when the inhaled oxygen fraction is 0.8.

Anesthetics↗
PubMed1985

Pneumothorax during positive-pressure mechanical ventilation.

The hemodynamic and respiratory effects of unilateral pneumothorax were studied during positive-pressure mechanical ventilation in five sheep. The sheep were anesthetized, intubated, and placed on mechanical ventilation with positive end-expiratory pressure (5 cm H2O). After baseline studies, including chest roentgenograms, were taken, increments of air were injected into the right pleural cavity. Measurements were repeated at pneumothoraces of 500, 1,000, and 1,500 ml. There was a steady fall in cardiac output (p less than 0.02) at pneumothoraces of 1,000 and 1,500 ml. The decrease in cardiac stroke volume paralleled that of cardiac output. Heart rate rose (p less than 0.05) at a pneumothorax of 1,500 ml. There appeared to be a linear relationship between the percent increase in pneumothorax as estimated by roentgenogram and the percent fall in cardiac output (r = 0.991). There was a steady rise in mean pulmonary arterial, pulmonary arterial capillary wedge, superior vena caval, and inferior vena caval pressures, although the changes in inferior vena caval pressure were not statistically different from baseline. Peak airway pressure increased from baseline at pneumothoraces of 1,000 and 1,500 ml. Both right and left end-expiratory intrapleural pressures increased and were statistically different (p less than 0.01) from baseline. However, there was a substantially greater rise in right intrapleural pressure than left. Arterial oxygen tension remained physiological throughout the study. This study indicates that cardiac output decreases as the amount of pneumothorax increases in sheep during mechanical ventilation. This study also demonstrates that, during positive-pressure mechanical ventilation, a relatively benign-appearing pneumothorax by chest roentgenogram may be associated with a significantly depressed cardiac output. In addition, arterial oxygen tension may not be useful in predicting the onset of pneumothorax during mechanical ventilation.

Animals↗
PubMed1984

Intraoperative diagnosis of rate-dependent bundle branch block.

Rate-dependent left bundle branch block (LBBB) occasionally occurs during anaesthesia when the heart rate exceeds a critical value. While it is usually a benign disorder, it may mask the electrocardiographic manifestations of myocardial ischaemia and the ST-T wave pattern associated with LBBB may be mistaken for those of ischaemia. This case report presents two cases in which rate-dependent LBBB was clearly documented during the perioperative period. It demonstrates the use of pharmacologic agents (e.g., atropine and neostigmine) and physiologic manipulations (e.g., carotid sinus massage) to alter the heart rate and confirm the diagnosis of benign rate-dependent LBBB in the operating room. These interventions should be used with caution in patients who have hypertension, angina, cerebrovascular, or AV node disease or in the setting of myocardial ischaemia or severe bundle branch disease.

Aged↗
PubMed1984

The effect of long-term controlled mechanical ventilation with positive end-expiratory pressure on renal function in dogs.

The effects of 46 h of mechanical ventilation and PEEP on urinary output, sodium excretion, and renal and cardiovascular function were examined. Dogs sedated with sodium pentobarbital were ventilated using one of three modes: spontaneous ventilation (SV), controlled mechanical ventilation (CMV), or CMV with 10 cmH2O positive end-expiratory pressure (CMV with PEEP). Intravenous fluids were given at a constant rate throughout the study and measurements of renal and cardiovascular function were made over four periods. Dogs whose lungs were ventilated with PEEP displayed more than two times the amount retention seen in the other groups as assessed by mean weight gain. This was due to an initial depression of urine flow, sodium excretion, and free water clearance. Urinary flow rate approximated the rate of fluid infusion by 20 h in SV dogs and by 27 h during CMV, while the maximum during CMV with PEEP occurred at 46 h. There were no significant differences in glomerular filtration rate, renal corticomedullary blood flow distribution, or renal blood flow between groups. During the 46 h, cardiac index increased (SV, +16%; CMV, +19%; CMV with PEEP, +64%), while systemic vascular resistance (SV, -28%; CMV, -30%; CMV with PEEP, -57%), renal vascular resistance (SV, -12%; CMV, -20%; CMV with PEEP, -23%), and mean arterial pressure (SV, -16%; CMV, -15%; CMV with PEEP, -15%) decreased in all groups. This study has demonstrated that when a constant sodium and water load was provided, the SV and CMV groups were rapidly able to adjust the urinary excretion to meet input, while the return of renal function toward normal in the CMV with PEEP group was delayed until almost 46 h from the start of ventilation.

Animals↗
PubMed1982

Influence of ventilation on response to fluid load in dogs: body water and albumin distribution.

Beagle dogs were sedated with intravenous pentobarbital ventilated for 46 h with either spontaneous ventilation (SV), controlled ventilation (CV), or controlled ventilation with 10 cmH2O end-expiratory pressure (CV + PEEP). Throughout the study period saline (0.45 per cent with added KCl) was infused at 120 ml/h. The influence of ventilatory mode on the accumulation and organ distribution of body water during continuous fluid loading was determined. Five animals were studied with each ventilatory mode. In all groups body weight increased, but with SV weight increase began only after 28 h and increased by 7.2 per cent of body weight by 46 h. With CV the weight increase was continuous and was 9.2 per cent of initial body weight at 46 h. With CV + PEEP the increase was earlier and greater reaching 22 per cent by 46 h. Radioisotopic analysis of total body water, extracellular water, and plasma and erythrocyte water demonstrated that the body weight increase was due to water retention principally in the extracellular compartment. Postmortem analysis of the major body organs for water and albumin distribution demonstrated increased water in the muscle and subcutaneous tissue of the CV + PEEP group that accounted for the total difference in water retention compared to the SV or CV animals. Organ extravascular albumin content varied relatively little between ventilatory modes. Ventilation with increased mean pressure was accompanied by marked and prolonged fluid retention. In these otherwise healthy dogs the water accumulation confined to sites that appeared unlikely to interfere with organ function.

Albumins↗
PubMed1981

Low flow continuous positive airway pressure with a modified fresh gas reservoir.

To minimize respiratory effort, continuous positive airway pressure (CPAP) must be applied in a manner that maintains a constant airway pressure. Conventional CPAP circuits depend on relatively high fresh gas flows (FGF) to maintain circuit pressure during inspiration. The authors describe a CPAP circuit employing a "weighted bellows." This simple modification of the conventional gas reservoir allows the FGF to be significantly reduced. In fact, minimal changes in circuit pressure can be achieved with FGF that barely exceeds the patient's minute ventilation. The modified system is compact, mechanically uncomplicated, and simply constructed.

Humans↗
PubMed1976

Effects of albumin and/or furosemide therapy on pulmonary edema induced by hydrochloric acid aspiration in rabbits.

Aspiration of hydrochloric acid in rabbits resulted in an increased P(A-a)O2 together with increases in both lung water volume and lung extravascular albumin. This finding suggests lung damage following acid aspiration is related to changes in capillary permeability, with pulmonary edema resulting from the movement of albumin and water into the interstitial space. Therapy with albumin and furosemide together reduced the lung water and albumin accumulation and decreased P(A-a)O2. Treatment with albumin or furosemide alone was ineffective. Caution should be exercised in administering albumin alone for therapy of pulmonary edema when plasma protein is not clearly decreased, or when increased pulmonary capillary permeability is suspected.

Albumins↗
PubMed1975

Anesthetic management of patients with cardiac disease.

The course of anesthesia for patients with cardiac disease includes assessment and management of complications during the entire perioperative period. A thorough understanding of the pharmacology of anesthetic drugs and their interactions with medications taken by patients with heart disease is of utmost importance. The rapid changes in intraoperative circulatory status may often necessitate second-to-second invasive monitoring techniques to maintain stability. Finally, knowledge of complications occurring commonly in such patients allows the anesthesiologist to prepare ahead of time for corrective measures which may be lifesaving.

Anesthesia↗