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Biomedical subjects

A F Connors

Publications and source records attributed to A F Connors.

At least 109 records · Page 6Linked to original sources
PubMed1986

Sodium morrhuate delivery to the lung during endoscopic variceal sclerotherapy.

We determined quantitatively the amount of sodium morrhuate that reaches the pulmonary vascular bed during endoscopic variceal sclerotherapy to ascertain whether this affects the diffusing capacity of the lung to carbon monoxide (DLCO). Eleven patients had measurements of DLCO and specific diffusing capacity (DLCO/VA) before and after sclerotherapy. In ten of these patients sclerotherapy was done using sodium morrhuate mixed with 99mTc-labeled albumin microspheres followed by quantitative radionuclide scanning. Most of the sodium morrhuate, 80 +/- 18% (SD) of the total dose, remained in the region of the esophagus. Only 20% of the injected dose reached the pulmonary circulation. There were no changes in DLCO or DLCO/VA. We conclude that most of the sclerosing solution injected during endoscopic variceal sclerotherapy remains at the site of injection. As a result, the pulmonary endothelium is exposed to small amounts of sodium morrhuate and no change in diffusing capacity occurs.

Adult↗
PubMed1985

Pleural effusions after endoscopic variceal sclerotherapy.

The prevalence of pleural effusions after endoscopic variceal sclerotherapy was reviewed in 30 patients undergoing 65 sclerotherapy sessions. Pleural effusions were identified radiographically after 31 of the 65 (48%) sclerotherapy sessions. Eleven of the effusions were right-sided, 10 were left-sided, and 10 were bilateral. Most of the effusions (20 of 31, 65%) were small. Significant postsclerotherapy chest pain was found more commonly in those patients who developed pleural effusions (11 of 31, 35%) compared with those who did not (4 of 34, 12%) (p less than 0.05). The total sclerosant volume injected was significantly greater in those who developed effusions (13.2 +/- 5.8 ml) (mean +/- SD) than in those who did not (8.5 +/- 4.5 ml) (p less than 0.001). Twelve effusions were analyzed biochemically after thoracentesis. Eleven effusions met one or more of three criteria commonly used to identify exudative effusions. We conclude that pleural effusions develop frequently after sclerotherapy. The effusions are predominantly exudative in character and presumably arise from inflammation of the mediastinal parietal pleura.

Adult↗
PubMed1985

Effect of endoscopic variceal sclerotherapy on gas exchange and hemodynamics in humans.

Adult respiratory distress syndrome has been reported after endoscopic variceal sclerotherapy with sodium morrhuate. It has been proposed that sclerosant entering the pulmonary circulation during intravariceal injections may cause pulmonary hypertension and capillary injury. The purpose of this study was to determine whether variceal sclerotherapy with sodium morrhuate causes capillary injury or pulmonary edema in humans. We studied the effect of sclerotherapy on gas exchange and pulmonary and systemic hemodynamics in 8 patients who required endoscopic variceal sclerotherapy for treatment of variceal hemorrhage. The pulmonary vascular resistance index increased from 246 +/- 67 dyn X s X cm-5/m2 (mean +/- SEM) at baseline to a high of 303 +/- 85 dyn X s X cm-5/m2 60 min after sclerotherapy (normal range 250-500 dyn X s X cm-5/m2). Pulmonary artery pressure remained stable while cardiac index decreased by 12% over the same period. There were also small increases in systemic vascular resistance index and systemic arterial pressure after sclerotherapy. Although there was no change in arterial oxygen tension, the alveolar-arterial oxygen difference improved after sclerotherapy. These results indicate that variceal sclerotherapy with sodium morrhuate is associated with clinically insignificant changes in pulmonary and systemic hemodynamics. We did not detect evidence of acute lung injury after sclerotherapy.

Adult↗
PubMed1985

Effects of changes in CO2 partial pressure on the sensation of respiratory drive.

The purpose of this study was to determine whether a change in respiratory sensation accompanies an increase in CO2 partial pressure (PCO2) in the absence of any changes in the level and pattern of thoracic displacement and respiratory muscle force. Eleven normal subjects were artificially hyperventilated with a positive-pressure mechanical respirator. In separate trials the tidal volume (VT) was set at 10 and 18 ml/kg and the frequency of ventilation (f) was adjusted to maintain the base-line end-tidal PCO2 at approximately 30 Torr. Thereafter, at a constant controlled VT and f, the PCO2 was progressively increased by raising the inspired CO2 concentration. There were no changes in respiratory motor activity as determined from the peak inspiratory airway pressure (Paw) until the PCO2 reached 40.8 +/- 1.0 and 40.1 +/- 1.0 (SE) Torr in the large and small VT trials, respectively. Initially there was no conscious awareness of the change in respiratory activity. Subjects first signaled that ventilatory needs were not being satisfied only after a further increase in PCO2 to 44.7 +/- 1.3 and 42.3 +/- 1.0 (SE) Torr in the large and small VT trials and after the Paw had fallen to 55-60% of the base-line value. The results suggest that changes in respiratory sensation produced by increasing chemical drive are a consequence of increases in respiratory efferent activity, but a direct effect of changes in PCO2 on respiratory sensation cannot be excluded.

Adult↗
PubMed1985

Complications of right heart catheterization. A prospective autopsy study.

The purpose of this study was to characterize the type and prevalence of abnormalities associated with right heart catheterization. We performed detailed post-mortem examinations of 32 consecutive patients brought to autopsy with a right heart catheter in the pulmonary artery. Thrombosis (17 patients, 53 percent), hemorrhagic lesions (25 patients, 78 percent), and intimal fibrin deposition (21 patients, 66 percent) were found at sites along the entire path of the catheter. Twenty-nine patients (91 percent) had either thrombosis, hemorrhage or both. While the superior vena cava was the most common site for all lesions, seven patients had thrombosis involving the chambers and valves of the heart and four had thrombosis involving the pulmonary artery. The incidence of thrombosis was significantly higher after 36 hours of catheterization (p less than 0.05). All five patients with thromboemboli in the more proximal pulmonary arteries had catheter-related thrombosis. We conclude that there is a high prevalence of thrombotic and hemorrhagic lesions in patients dying with pulmonary catheters in place; that the risk of thrombotic complications increases with duration of catheterization; and that patients with catheter-related thrombosis are at increased risk of thromboemboli to the proximal pulmonary arteries.

Adult↗
PubMed1981

Effects on breathing of putative neurotransmitters in the rostral hypothalamus of the rat.

The putative neurotransmitters norepinephrine (NE) and thyrotropin releasing hormone (TRH) are normally present in the rostral hypothalamic region (RHT) of the rat, and our aim was to evaluate possible effects of these agents on ventilatory regulations associated with this region. Using haloperidol-tranquilized Sprague-Dawley rats, microinfusions of both NE and TRH into the RHT resulted in an increase in rate, but not depth, of breathing. Control infusions and control infusion sites, mainly in the posterior hypothalamus, yielded no significant effect on breathing rate. Since NE and TRH can inhibit the discharge of some cells in the RHT, it was possible that the observed effects on breathing were due to depression of an inhibitory neural pathway. This idea was further tested by performing microinfusions using lidocaine. Evidence suggests that lidocaine can inhibit discharge in the central nervous system and that inhibitory pathways may be preferentially affected. Lidocaine produced effects on breathing comparable to NE and TRH, thereby supporting the proposition that inhibition of neural pathways in the RHT can stimulate breathing.

Animals↗
PubMed1981

Effect of inspiratory flow rate on gas exchange during mechanical ventilation.

We studied the effect of changes in inspiratory flow rate (VI) on gas exchange and respiratory system mechanics during mechanical ventilation. Seven patients with respiratory failure caused by severe chronic airway obstruction (CAO group) and 6 patients with other causes of respiratory failure (ORF group) were studied at 3 VI settings, 40 L/min, 70 L/min, and 100 L/min. In the CAO group, as VI increased from 40 L/min to 100 L/min, arterial oxygen tension increased 18%, venous admixture decreased 23.2%, dead space to tidal volume ratio decreased 23.7%, and tidal compliance of the respiratory system increased 31.2%. In the ORF group, as VI increased, there was little change in most parameters measured. The changes in the CAO group may be explained by redistribution of ventilation to low ventilation-perfusion ratio units, which empty more completely during the longer expiratory times allowed at high VI. Using a simple two-compartment lung model we determined that an increase in expiratory time from 4.2 to 6.1 s (the increase observed in the CAO group as VI increased from 40 L/min to 100 L/min) will result in redistribution of ventilation to long expiratory time constant respiratory units and produce changes in lung mechanics and gas exchange similar to those observed experimentally. We concluded that mechanical ventilation at high VI in patients with CAO is associated with improvement in gas exchange and more even distribution of ventilation, which appear to be due to the increased time available for alveolar emptying.

Aged↗
PubMed1980

Chest physical therapy. The immediate effect on oxygenation in acutely ill patients.

There is no documentation in the literature of the risk of hypoxemia after chest percussion in acutely ill adults with nonsurgical pulmonary disorders. We studied the immediate effect of postural drainage and chest percussion (PDP) on oxygenation in 22 hospitalized patients with a variety of acute, nonsurgical pulmonary disorders. Heart rate, respiratory rate, blood pressure, and arterial blood gas levels were measured at four points before, during, and after PDP. There was a significant fall in PaO2 after chest percussion in ten patients who produced no sputum or small amounts of mucoid sputum. The mean PaO2 fell 16.8 mm Hg (P < 0.05) immediately after PDP, when compared to the value obtained after postural drainage alone, and had fallen another 5.3 mm Hg (P < 0.01) 30 minutes after return to the pretreatment position. There was no significant change in PaO2 in 12 patients who produced moderate to large amounts of mucopurulent secretions. The fall in PaO2 was probably due to increased ventilation-perfusion mismatch since this fall was avoided in two patients restudied while receiving 100 percent oxygen. We concluded that all acutely ill patients receiving PDP should be carefully monitored and, if necessary, should receive increased levels of inspired oxygen to avoid hypoxemia. Our data suggest that the use of PDP in patients without sputum production is not indicated and is potentially dangerous.

Acute Disease↗
PubMedDate not supplied

Factors associated with use of cardiopulmonary resuscitation in seriously ill hospitalized adults.

CONTEXT: The epidemiology of do-not-resuscitate (DNR) orders for hospitalized patients has been reported, but little is known about factors associated with the use of cardiopulmonary resuscitation (CPR). OBJECTIVE: To identify factors associated with an attempt at CPR for patients who experienced cardiopulmonary arrest. DESIGN: Secondary analysis of data collected in 2 prospective cohort studies: the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT, 1989-1994) and the Hospitalized Elderly Longitudinal Project (HELP, 1994). Setting Five teaching hospitals across the United States. PARTICIPANTS: A total of 2505 seriously ill hospitalized patients and nonelectively admitted persons aged 80 years or older who experienced cardiopulmonary arrest. MAIN OUTCOME MEASURES: Medical records data on CPR efforts, DNR orders, disease severity, age, race, sex, length of stay, and survival; functional status and preferences concerning CPR obtained by interviews with patients or surrogates; and 2-month survival estimates provided by physicians. RESULTS: Five hundred fourteen study subjects (21 %) received CPR during their index hospitalization. Among them, 327 (63.6%) had CPR within 2 days of death and 93 (18.1 %) had resuscitation and survived their index hospitalization. Use of CPR was more likely in men (odds ratio [OR], 1.39; 95% confidence interval [CI], 1.12-1.73), younger patients (OR per 10-year increase, 0.90; 95% CI, 0.84-0.96), African Americans (OR, 1.76; 95% CI, 1.33-2.34), patients whose reported preferences were for CPR (OR, 2.60; 95% CI, 1.91-3.55), who reported better quality of life (OR, 1.49; 95% CI, 1.10-2.03), or who had higher physician estimates for 2-month survival (OR per 10% increase, 1.14; 95% CI, 1.09-1.19). Rates varied significantly with geographic location and diagnosis; the adjusted OR for patients with congestive heart failure was 3.31 (95% CI, 2.12-5.15) compared with patients with acute respiratory failure or multiple organ system failure. CONCLUSIONS: Our data suggest that a resuscitation attempt is more likely when preferred by patients and when death is least expected. Further study is required to understand variation in use of CPR among sites and for patients with different diagnoses, race, sex, or age.

Aged↗
PubMedDate not supplied

Lens model analysis of hemodynamic status in the critically ill.

The lens model recently has been extended to consider multiple outcomes and sequential use of clinical information. The authors have used this extended model 1) to describe the relationship between clinical information and physicians' assessments of hemodynamic status, 2) to describe the empirical relationship between clinical information and physiologic measures of hemodynamic status, and 3) to compare physicians' use of information with its empirical utility. Physicians prospectively provided estimates of cardiac index and pulmonary capillary wedge pressure for 440 intensive care unit patients prior to right heart catheterization. The correlation between physicians' estimates and measured hemodynamic status was lower than that between clinical information and hemodynamic status (0.42 versus 0.67). Only 7% of physicians' judgement was related to subsequent ancillary testing. Empirically, subsequent ancillary testing contributed 30% to the explanation of hemodynamic status. The lens model describes limitations of physician judgement in estimating left ventricular function and helps explain how patient features relate to measured hemodynamic status.

Cardiac Catheterization↗
PubMedDate not supplied

Hemodynamic assessment in managing the critically ill: is physician confidence warranted?

Prior to right-heart catheterization of 846 patients, 198 study physicians estimated values of pulmonary capillary wedge pressure (WP), cardiac index (Cl), and systemic vascular resistance index (VRI). The physicians also expressed their confidence in these estimates. Actual values of WP, Cl, and VRI as determined by catheterization enabled the authors to evaluate the quality of the physicians' judgments. The discrimination of the judgments was modest; areas under the ROC curves for WP, Cl, and VRI were 0.724, 0.681, and 0.656, respectively. Calculated using clinically relevant cutoff values, sensitivities were 64%, 50%, and 64%, and specificities were 71%, 75%, and 63%, respectively. Calibration of the estimates of WP, Cl, and VRI was also modest; physicians tended to overestimate low values and underestimate high values. Physicians were generally confident of their estimates, but there was no relation between confidence and accuracy. Experienced physicians were no more accurate than less experienced ones, although they were significantly more confident. The authors conclude that physicians should not use their levels of confidence in their subjective estimates of cardiac function in deciding whether to base therapy on these estimates.

Cardiac Catheterization↗
PubMedDate not supplied

The covariance decomposition of the probability score and its use in evaluating prognostic estimates. SUPPORT Investigators.

The probability score (PS) or Brier score has been used in a large number of studies in which physician judgment performance was assessed. However, the covariance decomposition of the PS has not previously been used to evaluate medical judgment. The authors introduce the technique and demonstrate it by analyzing prognostic estimates of three groups: physicians, their patients, and the patients' decision-making surrogates. The major components of the covariance decomposition--bias, slope, and scatter--are displayed in covariance graphs for each of the three groups. The decomposition reveals that whereas the physicians have the best overall estimation performance, their bias and their scatter are not always superior to those of the other two groups. This is primarily due to two factors. First, the physicians' prognostic estimates are pessimistic. Second, the patients place the large majority of their estimates in the most optimistic category, thereby achieving low scatter. The authors suggest that the calculational simplicity of this decomposition, its informativeness, and the intuitive nature of its components make it a useful tool with which to analyze medical judgment.

Bias↗