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Biomedical subjects

O Boyd

Publications and source records attributed to O Boyd.

34 records · Page 2Linked to original sources
PubMed1994

Effects of insertion depth and use of the sidearm of the introducer sheath of pulmonary artery catheters in cardiac output measurement.

OBJECTIVE: To investigate the effects of various insertion depths and sidearm functions of the introducer sheath of pulmonary artery flotation catheters on cardiac output measurement. DESIGN: Prospective, randomized, crossover study. SETTING: A general intensive care unit. PATIENTS: Ten patients who had a pulmonary artery flotation catheter placed in the right internal jugular vein as part of their clinical management. INTERVENTIONS: Cardiac output was measured at three insertion depths of the pulmonary artery catheter, each with a different rate of flow into the introducer sheath. MEASUREMENTS AND MAIN RESULTS: Significant differences of up to 23% occurred in the measurement of cardiac output under the various conditions. Cardiac output measurement is greater, the closer the injection port lies to the introducer sheath and the more open the introducer sheath sidearm. CONCLUSIONS: All users of pulmonary artery catheters should be alert to this problem. For reliable measurements of cardiac output by thermodilution, the cold saline injection port of the pulmonary artery catheter must be downstream of the introducer sheath, and the introducer sidearm must be closed.

Adult↗
PubMed1994

The cardiovascular changes associated with equipotent anaesthesia with either propofol or isoflurane. Particular emphasis on right ventricular function.

The differences in effects of anaesthetic agents on right ventricular function have not been studied. We have developed a cross-over study design to compare the effects of propofol and isoflurane on cardiac and specifically right ventricular function. Ten patients were anaesthetised with equivalent MAC of isoflurane to MIR of propofol. After measurements had been taken on the randomly assigned first agent the patients were crossed over to the other agent and measurements were repeated. Cardiac function was assessed using a pulmonary artery catheter with a fast response thermistor. There were no differences in heart rate or blood pressure between the two agents suggesting that equivalent anaesthetic doses had been given. There were significantly (P < 0.05) higher cardiac output (4.0 to 4.5 l.min-1), right ventricular ejection fraction (35.1 to 39.4%), stroke volume (35.4 to 39.6 ml) and right ventricular end-diastolic volume index (102 to 110 ml.m2-1) with propofol compared to isoflurane. We conclude that propofol results in improved right ventricular performance compared to isoflurane. We have also shown that anaesthetic agents can be compared using a cross-over study design, and have demonstrated that MAC of isoflurane and MIR of propofol can be directly compared. We suggest that propofol may be a more suitable agent than isoflurane for anaesthesia in patients who may already have impaired right ventricular function and in whom maintaining high cardiac output may be beneficial.

Aged↗
PubMed1993

A randomized clinical trial of the effect of deliberate perioperative increase of oxygen delivery on mortality in high-risk surgical patients.

OBJECTIVE: To assess the effect of deliberate perioperative increase in oxygen delivery on mortality and morbidity in patients who are at high risk of both following surgery. DESIGN: Prospective, randomized clinical trial. SETTING: A teaching hospital general intensive care unit, London, England. PATIENTS: A total of 107 surgical patients, who were assessed as high risk from previously identified criteria, were studied during an 18-month period. INTERVENTIONS: Patients were randomly assigned to a control group (n = 54) that received best standard perioperative care, or to a protocol group (n = 53) that, in addition, had deliberate increase of oxygen delivery index to greater than 600 mL/min per square meter by use of dopexamine hydrochloride infusion. OUTCOME MEASURES: Mortality and complications were assessed to 28 days postoperatively. RESULTS: Groups were similar with respect to demographics, admission criteria, operation type, and admission hemodynamic variables. Groups were treated similarly to maintain blood pressure, arterial saturation, hemoglobin concentration, and pulmonary artery occlusion pressure; however, once additional treatment with dopexamine hydrochloride had been given, the protocol group had significantly higher oxygen delivery preoperatively (median, 597 vs 399 mL/min per square meter; P < .001) and postoperatively (P < .001). Results indicate a 75% reduction in mortality (5.7% vs 22.2%; P = .015) and a halving of the mean (+/- SEM) number of complications per patient (0.68 [+/- 0.16] vs 1.35 [+/- 0.20]; P = .008) in patients randomized to the protocol group. CONCLUSION: Perioperative increase of oxygen delivery with dopexamine hydrochloride significantly reduces mortality and morbidity in high-risk surgical patients.

Aged↗
PubMed1993

Physiological scoring systems and audit.

Scoring systems designed to rate the severity of an illness are being used for comparison of hospital units to identify different standards of care and to allocate resources. One such scoring system is the Acute Physiology and Chronic Health Evaluation (APACHE) system which is designed to assess the severity of illness of patients in intensive care units (ICUs). It is widely assumed that different ICUs can be compared by the ratio of actual mortality to that predicted by the APACHE score. However, we suggest that the use of physiological data that can be influenced by medical and nursing intervention should not be used for audit. For example, by good care a patient may be made less severely ill and, therefore, may have a lower actual mortality while, at the same time, accumulating only a low APACHE score with low predicted mortality. This patient could have, therefore, the same mortality ratio as a patient treated inappropriately, who may have a higher actual mortality and a high APACHE score with greater predicted mortality. Paradoxically, the very accuracy of these scoring systems for assessing the severity of illness precludes their use for comparison and audit.

Humans↗
PubMed1993

Comparison of clinical information gained from routine blood-gas analysis and from gastric tonometry for intramural pH.

The measurement of gastric intramucosal pH (pHi) has been advocated to assist in decision-making for critically ill patients. To assess whether the information obtained from the measurement of pHi can be obtained from other measurements of metabolic acidosis, we studied 20 consecutive patients admitted to the intensive care unit. A mean of eight (range two to fourteen) data sets per patient were obtained, comprising measurement of arterial pH, pO2, pCO2, and oxygen saturation, tonometer balloon fluid pCO2, arterial pressures, and cardiac output. Bicarbonate concentration, base deficit or excess in blood and extracellular fluid, and pHi were calculated from these measurements. Relations between the variables and pHi were assessed by within-subject correlation comparisons. There were significant correlations (r > 0.6, p < 0.001) between markers of metabolic acidosis (base deficit in blood and extracellular fluid and bicarbonate concentration) and pHi. A blood base deficit of -4.65 or less and an extracellular-fluid base deficit of -6.13 or less could estimate pHi below 7.32 (lower limit of normal range) with sensitivity of at least 77% and specificity of at least 96%. There was no patient in whom either pHi or blood base deficit consistently reflected acidosis when the other variable did not. We conclude that the information that is obtained by gastric tonometry for pHi can be obtained more simply from measurements of metabolic acidosis; these variables can be calculated from routinely available blood-gas measurements.

Acidosis↗
PubMed1993

Propofol or midazolam for short-term alterations in sedation.

It is often necessary to adjust a patient's sedation level while they are in the intensive care unit. The purpose of this study was to compare propofol with midazolam for controlling short-term alterations in sedation. Twenty-three patients undergoing an interactive procedure, physiotherapy, during mechanical ventilation of the lungs were studied. The patients were randomly assigned to receive infusions of propofol or midazolam for sedation. Sedation was assessed using the method of Ramsay, where 3 is drowsy responding only to commands; and 5 is asleep with a slow response to light glabellar tap. Prior to physiotherapy sedation was deepened from 3 to 5 by increasing the sedative infusion rate, and level 5 was maintained during physiotherapy by adjusting the infusion rate whenever necessary. After physiotherapy, the sedative dose was reduced until level 3 was again achieved. During physiotherapy, sedation level 5 was achieved for 53.9% of the time with propofol but for only 25.7% with midazolam (P < 0.01). After physiotherapy, those patients sedated with propofol re-awakened to level 3 faster (8.3 +/- 2.3 min, mean +/- SE) than those receiving midazolam (92.8 +/- 35.0 min, P < 0.05). After physiotherapy, a further 1.8 +/- 0.5 dose adjustments were required to the midazolam infusion while only 0.4 +/- 0.2 adjustments were required to the propofol infusion (P < 0.05). During physiotherapy 3.0 +/- 0.5 dose adjustments to the propofol dose were required compared with 3.6 +/- 0.5 adjustments to the midazolam dose (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

The use of dopexamine hydrochloride to increase oxygen delivery perioperatively.

Perioperative increases in oxygen delivery may reduce morbidity and mortality in certain groups of surgical patients. However positive inotropic drugs, such as dobutamine and epinephrine themselves, may increase oxygen demand. Dopexamine hydrochloride is a new dopamine analogue with action at beta 2-adrenoceptors and DA1 receptors, but it possesses no direct alpha-adrenoceptor activity. We assessed the suitability of dopexamine to increase oxygen delivery perioperatively in eight patients having vascular surgery and studied its effects on oxygen demand. Oxygen delivery was increased toward 600 mL.min-1.m-2 by intravenous (IV) fluid infusion and IV titration of dopexamine hydrochloride. Oxygen delivery could be increased preoperatively (375 +/- 43 to 552 +/- 50 mL.min-1.m-2, P < 0.05) with > 600 mL.min-1.m-2 being achieved in five patients. This increase was achieved without significant increase in total body oxygen consumption (114 +/- 10 to 123 +/- 7 mL.min-1.m-2 P > 0.05) or rate pressure product (13.7 +/- 2.8 x 10(3) to 13.5 +/- 2.1 x 10(3) mm Hg.beats/min, P > 0.05). Postoperatively oxygen delivery was increased again without an increase in oxygen consumption (126 +/- 10 mL.min-1.m-2, P > 0.05) or rate pressure product (14.2 +/- 0.9 x 10(3) mm Hg.beats/min, P > 0.05). Dopexamine hydrochloride may provide a method for increasing oxygen delivery perioperatively with only limited increase in total body or myocardial oxygen demand.

Adrenergic Agonists↗
PubMed1992

The dependency of oxygen consumption on oxygen delivery in critically ill postoperative patients is mimicked by variations in sedation.

The finding of a dependence of oxygen consumption on oxygen delivery in critically ill patients has encouraged interventions to increase oxygen delivery index (DO2I) to overcome tissue hypoxia. In individuals other factors may influence oxygen consumption index (VO2I) and DO2I and may cause an apparently dependent relationship. We studied the effects of sedation and temperature on the VO2I/DO2I relationship in 13 perioperative patients. Pooled data showed significant correlations between VO2I and DO2I (r greater than 0.6, p less than 0.05) but also between VO2I and sedation score (r greater than 0.7, p less than 0.05), but not VO2I and temperature (r less than 0.5). When VO2I was standardized for the effects of sedation score (SS), the relationship between VO2I and DO2I was lost (r less than 0.5). Seven of 13 patients had significant (p less than 0.05) correlations between VO2I and SS and six of 13 between VO2I and DO2I; when standardized for the effect of varying sedation, no relationships were significant. When interpreting oxygen transport data from critically ill patients, the effects of sedation but not temperature must be taken into account; otherwise a false impression of a dependent relationship between VO2I and DO2I may cause unnecessary treatment.

Biological Transport↗
PubMed1990

Fibrosing alveolitis due to sulphasalazine in a patient with rheumatoid arthritis.

Rheumatoid arthritis is being increasingly treated with sulphasalazine. We report the first case of a patient being treated for rheumatoid arthritis who developed severe dyspnoea with chest radiograph shadowing, reversible on discontinuation of sulphasalazine and subsequent steroid therapy. An histological diagnosis of fibrosing alveolitis was made. Thirteen cases of similar reactions to sulphasalazine, all in patients treated for inflammatory bowel disease, can be found in the literature. We identify two types of pulmonary reaction, an eosinophilic pneumonitis and a fibrosing alveolitis. Adequate histological investigation is needed to differentiate between the two and management may be different. The diagnosis of pulmonary reactions are important because they can be easily confused with complications of the underlying disease but the prognosis is much better.

Arthritis, Rheumatoid↗
PubMed1987

Mianserin and complete heart block.

Cardiac complications are common in tricyclic antidepressant poisoning, but are rare with overdose of mianserin, which is a tetracyclic antidepressant. We report a case in which repeated episodes of complete heart block occurred following overdose with mianserin.

Female↗