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Biomedical subjects

J T Davidson

Publications and source records attributed to J T Davidson.

At least 73 records · Page 4Linked to original sources
PubMed1977

Preoperative intermittent positive pressure respiration as preparation for emergency valvular surgery for pulmonary edema.

Immediate emergency surgery is the accepted treatment of intractable pulmonary edema due to valvular heart disease. The presence of severe tissue hypoxia, acidosis, low cardiac output state and renal insufficiency results in a high operative risk. Delay of operation by several hours may prove advantageous in that it permits improvements of the patient's condition by means of intermittent positive pressure respiration with correction of acidosis and at the same time allows for treatment of the cardiac failure. Three illustrative cases are presented, all successfully managed by preoperative treatment in an intensive care unit. The pathophysiological basis of this therapeutic approach is discussed.

Adolescent↗
PubMed1976

Recurrent hallucinations following ketamine.

Recurrent hallucinations appeared in an 11-year-old boy during 5 days following ketamine anaesthesia. Previous anaesthesia with ketamine and adequate diazepam supplementation did not produce any such effect. The phenomenon of delayed recurring hallucinations is a rare but dangerous side-effect of ketamine, not unlike LSD flashbacks. The described case lends support to previous reports on the value of diazepam in the prevention of post-ketamine perceptual abnormalities.

Anesthesia, General↗
PubMed1976

Role of the carotid bodies in the heart rate response to breath holding in man.

To investigate the role of the carotid bodies in regulating the bradycardia of breath holding in man, we studied heart rate (HR) responses to prolonged breath holding (BH) in five asymptomatic asthmatic patients whose carotid bodies had been resected (CBR). Seven normal subjects served as controls. BH experiments were randomly initiated with single breaths of 100%, 21%, or 12% 92. During BH with 21% O2, normal subjects displayed the typical bradycardia; this response, however, was attenuated with the other O2 concentrations. In contrast, the CBR subjects manifested BH tachycardia which was inversely proportional to the O2 tension. HR increased in be CBR group by 5%, 31%, and 45% during BH with 100%, 21%, and 12% O2, respectively. These results demonstrate that the bradycardia of BH in normal man is under the influence of the carotid bodies. During BH and in the absence of carotid bodies, an O2 tension-dependent tachycardia is unveiled.

Adult↗
PubMed1976

The role of hypovolemic stress in the production of fat embolism in rabbits. 1. Morphologic alterations of the lungs.

In rabbits, an experimental model of fat embolism was produced that simulates the course of events in the clinical situation. Small doses of fat-cell suspension (0.075 ml/kg of body weight), prepared by collagenase treatment of homologous adipose tissue, were injected intravenously. Concomitantly, hypovolemia was produced in two animal groups by either withdrawing 20 percent of the estimated blood volume or by application of a hind-limb ischemic tourniquet for 90 minutes. The presence of pathoanatomic characteristics typical of fat embolism was evaluated by recording lung/body weights, macroscopic appearance, and semiquantitative microscopic estimation in the lungs of edema, hemorrhage, atelectasis, intravascular coagulation, and leukocytic thrombi. Mean indices of lung/body weight were higher in all animals receiving injections of fat-cell suspension, as compared to controls. The score for microscopic generalized pulmonary damage was significantly higher in rabbits exposed to both fat-cell injections and hypovolemia than in controls or after fat-cell injections alone. It is concluded that hypovolemia enhances the development of fat embolism in rabbits subjected to small doses of fat-cell suspension.

Animals↗
PubMed1976

The role of hypovolemic stress in the production of fat embolism in rabbits. 2. Changes in arterial blood gas levels and static compliance.

The purpose of this study was to assess the possible role of hypovolemia as a factor in the production of impaired pulmonary function in pulmonary fat embolizaiton. Iv vivo static lung compliance was measured by inflating the lungs with known volumes of air and recording the transpulmonary pressure, monitoring intraesophageal pressure as an index of intrapleural pressure. Arterial blood was drawn from the central artery of the ear. Embolization was produced by the intravenous injection of homologous fat cells either as the sole experimental procedure or in conjunction with hypovolemic shock. Two types of shock were studied. In one, 20 percent of the blood volume was removed, producing hypovolemia associated with hemodilution, and in the other a tourniquet was applied to induce hypovolemia and hemoconcentration. The results indicate that embolization is associated with significantly greater impairment of pulmonary function if it develops on a background of shock than if it occurs in an otherwise healthy animal. These pathophysiologic findings parallel the results of a morphologic study.

Adipose Tissue↗
PubMed1975

The acute effect of pulmonary burns on lung mechanics and gas exchange in the rabbit.

To determine the role of the thermal element in the production of lung injury uncomplicated by the inhalation of fumes and soot, 18 anaesthetized, paralysed and ventilated rabbits were subjected to a steam burn of the respiratory tract. Transpulmonary pressure (difference between airway and pleural pressure) was recorded under static conditions between functional residual capacity and 40 ml above this point and the values obtained were used to calculate lung compliance. Static compliance decreased progressively with time in each of the experimental animals, the maximum decrease occurring within the 1st hour. Ten of the 18 animals died within 4 hr of the burn. There was little impairment of gas exchange. This data would suggest the clinical value of the early measurement of lung compliance in the evaluation of thermal pulmonary burns. Postmortem studies showed the presence of pulmonary oedema with intra-alveolar peribronchial and perivascular haemorrhages. The lesions were most prominent centrally, apparently because the dissipation of the heat resulted in less damage to the peripheral areas of the lung. Pulmonary megakaryocytosis was noted in seven of the experimental animals. This may have been a non-specific reaction to lung trauma.

Animals↗
PubMed1975

Anesthesia in the Yom Kippur war.

The role of the anesthetist in the treatment of battle casualties is discussed in the light of personal experience in a field hospital and in the rear during the Yom Kippur War of October 1973. Resuscitation and intensive care both before and after evacuation play an important part in reducing mortality, and the importance of providing adequate facilities for these functions in the battle area as well as at the base is emphasized.

Anesthesia↗