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Biomedical subjects

A F Connors

Publications and source records attributed to A F Connors.

At least 91 records · Page 5Linked to original sources
PubMed1992

Incidence of thrombosis during central venous catheterization of newborns: a prospective study.

Forty-two newborns were studied prospectively to determine the incidence of thrombosis due to central venous catheterization. Following Broviac catheter placement, the catheter tip, distal superior vena cava, and right atrium were evaluated by weekly two-dimensional echocardiograms. The presence of thrombosis was examined in relation to birth weight, gestational age, age and weight at the time of catheter placement, antithrombin III levels, and platelet counts. Six newborns (14%) were noted to have a thrombus by echocardiographic examination after the catheter had been in place for a median duration of 7 weeks. The infants with thrombus formation had significantly lower birth weights (887 +/- 231 v 1,409 +/- 766 g; P = .003) and gestational ages (27 +/- 2.4 v 30.3 +/- 4.3 weeks; P = .018) than those without thrombus. Their weights (757 +/- 203 v 1,832 +/- 1,098 g; P = .000) and ages (2.75 +/- 0.76 v 7.24 +/- 7.8 weeks; P = .002) at the time of catheter placement were also lower; the antithrombin III levels were lower at the time of catheter placement (0.32 +/- 0.08 v 0.06 +/- 0.31 U/mL; P = .001), but were normal for gestational and postnatal age. The presence of thrombosis was not related to the sex of the baby, the platelet count, or the duration of catheterization.

Age Factors↗
PubMed1992

Cardiac arrhythmias during postural drainage and chest percussion of critically ill patients.

In this study we determine the prevalence and type of arrhythmias that occur during postural drainage and chest percussion (PDP) of critically ill patients, and identify those patients who are most at risk of developing them. We monitored the vital signs and ECGs of 72 ICU patients during their initial PDP treatment. Eight patients (11.1 percent) had development of major arrhythmias, 18 (25 percent) had minor arrhythmias, and 46 (63.9 percent) had none. Increased age (p < 0.0001) and the presence of acute cardiac disorders (p < 0.001) were associated with increased risk of arrhythmias. Individuals experiencing major arrhythmias had a significantly decreased BP and respiratory rate with an increased heart rate during PDP. We conclude that arrhythmias are common during PDP of critically ill patients and recommend that ICU patients be carefully monitored during PDP. When considering PDP for older patients and patients with acute cardiac disease, physicians should carefully weigh the risk of arrhythmias against the benefits of this treatment.

Adolescent↗
PubMed1990

Theophylline concentrations in patients with acute exacerbation of COPD.

Patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) frequently report a history of theophylline use prior to arrival in the emergency department. The reliability of using this history to guide aminophylline therapy is, however, unclear. The authors studied patients with an acute exacerbation of COPD to determine the relation between the initial theophylline level and the medication history. Seventy-nine patients with a mean age of 64.3 years were entered into the study. The average theophylline level was 10.8 micrograms/mL. Forty-seven percent of the patients had subtherapeutic levels, 46% had therapeutic levels, and 7% had toxic levels. There were weak although statistically significant correlations between the theophylline level and the interval since the last theophylline dose (r = -.40, P less than .001), as well as with the last recorded outpatient theophylline level (r = .45, P less than .001). However, the theophylline level could not be predicted accurately in a number of patients. The authors conclude, because the prediction rule was often inaccurate, aminophylline therapy in patients with acute exacerbation of COPD should be based on direct measurement of the serum theophylline level.

Aged↗
PubMed1990

Risk of toxicity in patients with elevated theophylline levels.

Toxic side effects of elevated theophylline levels range from minor symptoms to life-threatening complications. We investigated the incidence of life-threatening events in patients with elevated levels in order to identify those at low risk for significant theophylline toxicity. Five hundred ten episodes of elevated levels were reviewed in 214 hospitalized patients. Four seizures occurred in patients with prior seizures, while two had new onset seizures with levels of 27 and 30 micrograms/mL. All eight episodes of ventricular tachycardia occurred in patients who had a history of arrhythmias or who were critically ill. Seven patients had new supraventricular arrhythmias with levels of 21 to 40 micrograms/mL. Life-threatening events may occur in critically ill patients or patients with past seizures or arrhythmias with mildly elevated levels, although the extent to which theophylline toxicity contributes to morbidity or mortality in these patients is unclear. Patients who are otherwise healthy are unlikely to have significant theophylline toxicity with levels less than 25 micrograms/mL.

Aged↗
PubMed1990

Hemodynamic status in critically ill patients with and without acute heart disease.

Physicians have been urged to reduce the use of the pulmonary artery catheter. However, there are no guidelines to help the clinician make the decision to use or withhold invasive monitoring in the individual patient. This study was designed to examine the accuracy of physician estimates of cardiac function in a spectrum of patients with hemodynamic instability to determine whether differences in accuracy among subgroups would suggest subgroups of patients who could be managed without invasive measurements. Physician estimates of cardiac index were found to be sufficiently accurate in patients without acute heart disease that initial management without invasive monitoring may be appropriate in selected cases. However, due to the general inaccuracy of physician estimates, efforts to improve the accuracy of clinical judgments of cardiac function and hemodynamic status should be pursued with vigor in patients both with and without acute cardiac dysfunction.

Aged↗
PubMed1990

Peripheral vs central squamous cell carcinoma of the lung. A comparison of clinical features, histopathology, and survival.

We reviewed the clinical features and histopathologic findings of 21 peripheral pulmonary squamous cell carcinomas (SCC) resected at our institution between 1961 and 1981 and compared them with 19 central SCCs. Histologic features were scored semiquantitatively from 0 to 3+. Peripheral SCC represented 16% of all resected SCCs. The proportion of patients with multiple symptoms was lower and survival during the 5 years after surgery was better in the peripheral group. Tumor size, mitoses per high-power field (2.4 +/- 0.3 vs 4.1 +/- 0.6 [SEM]), prevalence of lymphatic invasion (19% vs 58%), and lymph node metastases (5% vs 37%) were lower, while chest wall invasion was more frequent (25% vs 0) for peripheral SCCs. Peripheral tumors also had more intense (2 or 3+) lymphoplasmacytic (86% vs 47%) and desmoplastic (95% vs 68%) reactions. Cox regression analysis did not support a significant relationship between tumor location and survival. We conclude that, compared with the central SCC, peripheral SCC is associated with fewer symptoms at presentation and better survival. Morphologically, peripheral SCCs are smaller, have fewer mitoses, less prevalent lymphatic invasion, and a more intense stromal reaction. Improved survival in patients with peripheral SCC may be due to a more favorable stage at the time of initial treatment.

Carcinoma, Squamous Cell↗
PubMed1989

Relationship between arterial blood gases and spirometry in acute exacerbations of chronic obstructive pulmonary disease.

Previous studies have established spirometric criteria for arterial blood gas analysis during acute asthmatic attacks. However, only general guidelines have been available regarding the need for blood gas analysis during an acute exacerbation of chronic obstructive pulmonary disease (COPD). We conducted a study to determine the relationship between arterial blood gases and spirometry in 70 emergency department patients during acute exacerbations of COPD. Arterial blood gas analysis and spirometry were performed on arrival at the emergency department. All of the patients with a pCO2 of more than 45 mm Hg had an FEV1 of less than 35% of the predicted normal. We found patients with a pO2 of less than 60 mm Hg who had an FEV1 as high as 54% of the predicted normal. There was no correlation between the FEV1 and pO2. Because spirometry was not reliable for identifying patients with significant hypoxemia, we conclude that arterial blood gas analysis is indicated for patients presenting to the ED with acute exacerbations of COPD. Spirometric criteria that have been used to eliminate the need for arterial blood gases in asthmatic patients cannot be applied safely to patients with COPD.

Acute Disease↗
PubMed1989

A randomized controlled trial of methylprednisolone in the emergency treatment of acute exacerbations of COPD.

We conducted a randomized, controlled double-blind study to determine whether intravenous administration of methylprednisolone early in the therapy for acute exacerbations of COPD would improve pulmonary function in the Emergency Department and reduce the need for hospitalization. Ninety-six patients completed the study. All were at least 50 years of age and had no history of asthma. Patients received aminophylline and hourly administration of aerosolized isoetharine. Methylprednisolone (100 mg) or physiologic saline solution was given within one-half hour of arrival in the Emergency Department. Spirometry was performed initially and after the third and fifth aerosol treatments. We found no greater improvement in FEV1 in the group receiving the steroid (37 percent) than in the control group (43 percent; NS). There was also no difference in the rate of hospitalization (33 percent in the steroid-treated group vs 30 percent in the control group; NS). We conclude that early administration of methylprednisolone does not affect the emergency phase of treatment for acute exacerbations of COPD.

Aerosols↗
PubMed1987

Level of consciousness as a predictor of complications following tricyclic overdose.

In order to determine whether patients at low risk for complications following tricyclic antidepressant (TCA) overdose can be identified, we analyzed the records of all admissions for TCA overdose from 1975 to 1985. Of the 92 patients reviewed, 37 had serious complications including hypoventilation, loss of protective airway reflexes, seizures, hypotension, hemodynamically significant arrhythmias, or death. Patients with complications had increased heart rate, depressed level of consciousness, depressed Glasgow Coma Scale, and prolonged QRS interval, as compared to patients without complications. All 37 patients with serious complications required intubation in the emergency department. A Glasgow Coma Scale of less than 8 was the most sensitive predictor of serious complications (sensitivity = .86; specificity = .89). This was significantly better than the QRS interval (QRS greater than or equal to 100 msec; sensitivity = 59; specificity = .76). We conclude that level of consciousness is a better predictor of risk of complications and need for ICU admission than the QRS interval. Patients who are responsive to verbal stimuli on leaving the ED are at very low risk of developing complications.

Adolescent↗
PubMed1987

Management of chronic alveolar hypoventilation with nasal positive pressure breathing.

Negative pressure ventilation is the most common method of providing assisted ventilation without a tracheostomy. Unfortunately, negative pressure devices have several disadvantages and are not well tolerated by all patients. We present a patient in whom intermittent assisted ventilation was applied successfully by using a nasal mask to provide positive pressure ventilatory support.

Adult↗
PubMed1986

Effects of volume and frequency of mechanical ventilation on respiratory activity in humans.

This study evaluated the interaction between respiratory chemical drive and non-chemical factors related to the frequency and level of thoracic displacement during mechanical ventilation in shaping respiratory activity. Ten normal subjects were artificially hyperventilated with a positive-pressure mechanical respirator to a baseline end-tidal PCO2 of approximately 30 Torr. Thereafter, in separate trials, the end-tidal PCO2 was increased by (a) progressively raising the concentration of CO2 in the inspired gas (FICO2) while holding tidal volume (VT) and breathing frequency (f) constant, (b) lowering f while holding VT and FICO2 constant, and (c) lowering VT while maintaining a constant f and FICO2. Initially, as the PCO2 rose above baseline levels with increases in FICO2, there was no change in inspiratory muscle activity, as measured by the peak inspiratory airway pressure, until the PCO2 reached 40 Torr. This PCO2 threshold for a change in respiratory activity was significantly reduced when the tidal volume or frequency of mechanical ventilation was lowered. These results suggest that non-chemical drives related to the frequency and level of thoracic displacement interact with chemical stimuli in shaping respiratory activity.

Adult↗
PubMed1986

Thrombosis and infection complicating central venous catheterization in neonates.

To determine the risk of complication associated with Broviac central venous catheterization in neonates, we reviewed the records of 107 infants who were catheterized an average of 5 weeks after birth and cared for in our neonatal intensive care unit. Forty-five of the 107 neonates (42%) had one or more catheter-related complications. Infants with complications had significantly lower birth weights and gestational age, longer duration of catheterization, and more repeat catheterizations than infants without complications. The mortality rate in infants with complications was not different than that of infants without complications. The most common complications were thrombosis (23 neonates) and infection (20 neonates). The birth weight and the number of catheterizations were the best predictors of the risk of complications as determined by multiple regression analysis. We conclude that the risk of complication associated with central venous catheterization is high in our population of predominantly premature neonates; that the risk of complication is increased in neonates weighing less than 1,000 g or requiring more than one catheter; and that despite the high complication rate central venous catheterization was not associated with increased mortality in this population.

Birth Weight↗