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Biomedical subjects

W S Howland

Publications and source records attributed to W S Howland.

At least 19 recordsLinked to original sources
PubMed1990

Origin of oncologic anesthetic techniques.

The patient with cancer poses a challenge to the anesthesiologist for a variety of reasons including the effects of cancer (altered hemostasis, depressed immune response, and compromised airways), the effects of chemotherapy (malfunction of the myocardium, lungs, kidneys, and bone marrow; depression of pseudocholinesterase; and production of the syndrome of inappropriate secretion of antidiuretic hormone), as well as effects of radical cancer surgery (massive blood loss and the need for prolonged anesthesia). Anesthetic techniques to address these problems had their beginnings in the Department of Anesthesiology at Memorial Sloan-Kettering Cancer Center. This paper traces the development of modern oncologic anesthesia and discusses how these advances significantly reduced operative mortality.

Adult↗
PubMed1986

Hemodynamic oxygen transport and 2,3-diphosphoglycerate changes after transfusion of patients in acute respiratory failure.

The goals of management of patients with respiratory failure include improving arterial oxygenation with PEEP and red cell transfusion to maintain oxygen carrying capacity, both of which contribute to improving tissue oxygen delivery. However, standard CPD-stored blood is rapidly depleted of 2,3 diphosphoglycerate (2,3 DPG) and ATP, with resultant inadequacy of the red cell oxygen transport function. In 15 patients requiring mechanical ventilation with PEEP whose initial Hct less than or equal to 35%, we studied the effect of transfusion of 7 ml/kg of CPD-stored packed red blood cells on hemodynamic and oxygen delivery variables, pulmonary venous admixture (QA/QT), and erythrocytic P50, 2,3 DPG and ATP concentrations. Hemodynamics were not significantly altered by transfusion. 2,3 DPG decreased significantly from 14.5 +/- 1.1 to 13.1 +/- 1.5 mcmol/g Hb (mean +/- SD, p less than 0.05). There was no significant change in P50 or ATP. QA/QT rose significantly, from 20.1 +/- 7.8 to 28.9 +/- 12.3% (mean +/- SD, p less than 0.02). In our patients, an increase in arterial oxygen content obtained by transfusion was not followed by any associated decrease in cardiac work, as implied by solution of equations for oxygen delivery and oxygen consumption. The rise in QA/QT is undesirable in patients requiring PEEP, since it complicates management of their mechanical ventilatory support.

2,3-Diphosphoglycerate↗
PubMed1984

Pneumatic-to-electrical analog for high-frequency jet ventilation of disrupted airways.

A pneumatic-to-electrical circuit analog is used to describe 2 separate mechanisms by which high-frequency jet ventilators sustain ventilation and oxygenation in the presence of large airway disruptions. The frequency-dependent mechanism is based on variations in the pneumatic equivalent to capacitive reactance. The pressure-dependent mechanism models lung defects on a voltage-controlled resistor. The electrical circuit model is also used to explain the factors leading to gas trapping and inadvertent positive end-expiratory pressure during high-frequency jet ventilation.

Airway Resistance↗
PubMed1984

High-frequency jet ventilation: technical implications.

A variety of technical decisions are required for the proper selection and safe and efficacious application of high-frequency jet ventilation (HFJV). Criteria for analyzing the performance of an HFJV system are presented, along with discussions of some of the more common respiratory measurements and their applicability to HFJV.

Equipment Safety↗
PubMed1984

Experimental evaluation of high-frequency jet ventilation.

The consensus of available studies indicates that high-frequency jet ventilation (HFJV) can adequately ventilate animals in respiratory failure, although a clear superiority to volume-cycled ventilation (VCV) cannot be established. HFJV is probably useful in the presence of airway disruption and in tracheal or pulmonary surgery. Clinical trials and additional bench and animal studies must be performed, to reach a full understanding of the potential benefits of this technique.

Animals↗
PubMed1984

Early prediction of outcome of respiratory failure. Comparison of high-frequency jet ventilation and volume-cycled ventilation.

Data from a prospective randomized investigation comparing volume-cycled ventilation and high-frequency jet ventilation were reexamined to determine whether improvement of respiratory and hemodynamic function, as well as ultimate outcome (death or survival), could be predicted early in the course of the disease. End points were selected for the ratio of the arterial oxygen pressure over the fractional concentration of oxygen in the inspired gas (PaO2/FIO2), the arterial oxygen saturation (SaO2), the arterial carbon dioxide tension (PaCO2), and the cardiac index. Patients were assigned to "success" or "failure" groups, according to the values recorded for those end points 24 hours after institution of mechanical ventilation. Values obtained from initiation of mechanical ventilation to 16 hours later were divided into four time groups. Differences between patients who "succeeded" and "failed" were compared at each time interval. Ultimate outcome was also compared. The PaCO2 and cardiac index were poor predictors of survival. Early values did not foretell the progression of these variables. The PaO2/FIO2 and SaO2 effectively discriminated, at all time intervals, between patients who succeeded and failed on volume-cycled ventilation. On high-frequency jet ventilation, significant differences were evident only after eight hours of support. With both types of ventilator, patients who reached the end point of oxygenation at 24 hours survived in far greater numbers than those who did not. On the basis of this investigation, it appears justified to attempt high-frequency jet ventilation in patients who do not rapidly improve on volume-cycled ventilation. Institution of high-frequency jet ventilation as the initial support method may not be advisable, since failure does not become apparent for many hours.

Cardiac Output↗
PubMed1983

Naloxone in septic shock.

Naloxone, 0.3 mg/kg of a 10 mg/ml solution, was administered as a single bolus to patients in septic shock if their systolic blood pressure (BP) was less than 100 mm Hg or MAP less than 70 mm Hg with evidence of renal or cerebral hypoperfusion. Patients with chronic or acute (less than 12 h) administration of narcotics were excluded. Ten patients received naloxone; 5 patients had significant increases in blood pressure; 5 had no response. Maximal response in BP occurred by 15 min, and lasted 45-165 min. Responders could not be separated by nonresponders by analysis of baseline, hemodynamics, or prior steroid therapy; nonresponders were hemodynamically compromised greater than 24 h; responders less than or equal to 8. Two patients in each group were chronically on high-dose steroids and responded to a 2nd smaller dose of naloxone when effects of initial bolus had ended. Naloxone, 0.3 mg/kg, can reverse endorphin-mediated hypotension in acute septic shock in patients who have received chronic steroid therapy.

Adult↗
PubMed1983

High-frequency jet ventilation. A prospective randomized evaluation.

Three hundred nine patients were randomly allocated to two ventilatory protocols; 157 patients were supported with a volume-cycled ventilator (VCV) (Bear Medical BEAR 1) and 152 with a high-frequency jet ventilatory (HFJV) developed at our institution. The two ventilators were compared for safety, reliability, ease of use, and efficacy in maintaining gas exchange. On VCV, end points of therapy were: fractional concentration of oxygen in the inspired gas (FIo2) less than or equal to 0.40; arterial oxygen pressure (PaO2) greater than or equal to 70 mm Hg; cardiac index (CI) greater than or equal to 3.5 L/min/sq m; and spontaneous respiratory rate less than or equal to eight breaths per minute. On HFJV, end points were: FIo2 less than or equal to 0.45; arterial oxygen saturation greater than or equal to 0.90; and CI greater than or equal to 3.5 L/min/sq m. Spontaneous ventilation and pulmonary venous admixture reduction were the goals on VCV, with oxygen transport the goal on HFJV, Total duration of use of the ventilators was approximately 800 days with both types of devices; there were no technical failures, and the incidence of barotrauma was less than 5 percent. The end point of mechanical ventilation was reached by a significantly higher percentage of the patients randomized to HFJV. Patients who failed to reach the therapeutic goal within 24 hours were crossed over to the other form of support. Those crossed from VCV to HFJV improved more rapidly and in greater number than those crossed from HFJV to VCV. When survival and total duration of stay in the intensive care unit were considered, there was no difference between VCV and HFJV. Considering data on gas exchange, VCV provided a higher PaO2 at equivalent positive end-respiratory pressure than HFJV. Alveolar ventilation was slightly better on HFJV. Differences were statistically but not clinically significant. On HFJV, oxygenation and ventilation were maintained with lower peak inspiratory pressures and smaller tidal volumes than those required for VCV. This investigation proves that HFJV is a safe and reliable method to provide mechanical support which does not, at this time, offer obvious benefits over VCV.

Female↗
PubMed1982

High-frequency jet ventilation: theoretical considerations and clinical observations.

High-frequency jet ventilation (HFJV) described a technique of mechanical respiratory support based on the delivery of gases under conditions of constant flow and low pressure. Among the benefits ascribed to HFJV are lessened interference with hemodynamic function and reduced danger of barotrauma. The theoretical and technical aspects of HFJV are discussed and the clinical experience with 39 patients in respiratory failure reported. Synchronization of HFMV with heart rate was attempted in three patients. Cardiac output and ejection fraction increased in all of them. At present, results suggest that HFJV may be the ideal form of support for patients with major airway disruption. The available data also indicated that extensive clinical trials are warranted to define advantages and limits of this form of ventilation.

Bronchial Fistula↗