Bertil Löfström

Thoracic Gas Volume and Chest-Abdomen Dimensions during Anesthesia and Muscle Paralysis

The aim was to study thoracic gas volume (TGV) in anesthetized and paralyzed subjects (n = 16) and to analyze any change in TGV in terms of thoraco-abdominal dimensions. TGV was measured by means of a body plethysmograph, using a super syringe for lung inflation during muscle paralysis. The thoraco-abdominal shape at the mamillary and umbilical levels was studied by means of magnetometry for the assessment of antero-posterior diameters (A-P), a strain gauge technique for measuring circumferences and respiratory inductive plethysmography for the recording of cross-sectional areas. TGV was reduced by an average of 28 per cent, from 2.38 1 awake to 1.72 1 during pentothal anesthesia and spontaneous breathing. No change in A-P diameters or cross-sectional areas were noticed. Muscle paralysis and mechanical ventilation caused no further change in TGV, nor were there any changes in A-P diameters, circumferences or cross-sectional areas of the chest or abdomen. The rib cage contribution to the tidal breath was significantly increased, from 41 per cent to 62 per cent to the tidal volume. The result of a lowered TGV during anesthesia concurrently with no measurable change in chest-abdomen dimensions remains a paradox not yet fully understood.

BILATERAL ULNAR NERVE BLOCKS FOR THE EVALUATION OF LOCAL ANAESTHETIC AGENTS

Bilateral ulnar nerve blocks with a double‐blind technique were performed in 10 male volunteers in order to evaluate a new local anaesthetic agent, prilocaine, and the effect of epinephrine when added to the local anaesthetic solutions.

CHANGES IN BLOOD VOLUME IN INDUCED HYPOTHERMIA

In earlier investigations (L.-E. GELIN and B. L~FSTROM (1954, 1955)l3

CARDIOVASCULAR EFFECTS OF BETA-RECEPTOR BLOCKING DRUGS DURING HALOTHANE ANAESTHESIA IN MAN

l4) induced hypothermia was found to be accompanied by intravascular aggregation and impairment of capillary flow. The purpose of the present investigation was to determine whether any correlation could be demonstrated between the changes in the capillaries and changes in blood volume. I t would also be of interest to examine whether the total amount of circulating hemoglobin was decreased after hypothermia as has been found to be true after fractures and burns (L.-E. GELIN ( 1956)12). By determination of the erythrocyte sedimentation rate and the dye disappearance curves for Evans blue it might also be possible to form an opinion of the cause of intravascular aggregation observed during hypothermia.

PROPRANOLOL IN ETHER ANESTHESIA

Fifteen patients anaesthetized with halothane were given a beta‐adrenergic receptor blocking substance intravenously, either propranolol or l‐alprenolol.

Effects of Epinephrine in Solutions of Local Anaesthetic Agents

In 10 subjects studied, intravenous administration of 5 mg propranolol during ether anesthesia produced falls in heart rate, systemic arterial pressures, cardiac output and stroke volume, with associated rises in Fentany1 venous pressure and total peripheral vascular resistance. The responses to propranolol could be ascribed to a blockade of the beta‐adrenergic cardiovascular stimulation by ether. The importance of such a stimulation in maintaining adequate circulation during ether anesthesia was demonstrated.

Studies on Pulmonary Function in Patients during Respirator Treatment. Diagnostic and Prognostic Evaluations

Carefully standardized test procedures are necessary to obtain true information on the blocking effect of local anaesthetic agents, as has been stressed by BONICA (1957). Stimulated by his article we tried several blocks possibly suited for testing local anaesthetic agents. We found that bilateral ulnar nerve blocks in double blind studies were ideal for testing local anaesthetic agents. A thin needle was used and exactly 1 ml of the test solution was injected into the nerve. In the preliminary study we obtained what seemed to be reliable data on onset time, duration of action (Table 1) and also of the penetration power or the frequency of successful blocks (Fig. 1). In this study a simple pinch test was used to evaluate analgesia. This test has also been compared to some objective methods by L.THULIN and B. LOFSTROM (Fig. 2). The relative differences between the blocked and unblocked side in skin temperature, in sympatho-galvanic response to a stimulus, and in muscle power were compared with a pinch test. As can be seen from the figure the results of the pinch test were well in accordance with the more

Induced hypothermia and intravascular aggregation.

Twenty‐nine patients, divided into three groups: 1) chronic obstructive pulmonary disease; 2) acute or chronic pulmonary disease with left heart failure; 3) respiratory insufficiency after peritonitis, pancreatitis, and/or sepsis, were studied during respirator treatment with regard to gas exchange, breathing mechanics and central circulation. The dead space ventilation was somewhat greater in group 1 than in the other groups. The alveolar‐arterial oxygen tension difference was least in group 1, greater in group 2 and extremely high in group J. Neither dynamic compliance of the thorax nor inspiratory resistance showed any significant differences between the groups. The cardiac output had the highest values in group J. The venous admixture was generally small in group 1 and extremely large in group 3. The pulmonary artery pressures were highest in group 2. Three variables proved to be valuable when assessing the prognosis of a patient: a large venous admixture; a lagge alveolar‐arterial oxygen tension difference, and a high pulmonary artery pressure indicated a less favourable prognosis.