Effects of hypokalemia on the various parts of the conduction system of the dog heart in situ.

The effects of hypokalemia were studied on the various parts of the conduction system by means of His bundle potential recording in the heart of vagotomized dogs. Plasma potassium concentration was lowered by extracorporeal dialysis, precautions being taken against the simultaneous impairment of other parameters, especially humoral. In order to make sure that the changes in atrioventricular conduction observed were due to hypokalemia, a control series of experiments was carried out, under strictly identical conditions except that the dialysis fluid was not devoid of potassium. The following alterations were observed during the lowering of potassium concentration from 3.2 to 1.6 mmol/l: atrioventricular node conduction time (AH interval) increased steadily up to 250% of control values; conduction time in atrial contractile tissue (SA interval) and His Purkinje system (HV interval) exhibited variations much later and much smaller; conduction time in ventricular contractile tissue was not significantly affected; effective refractory period (ERP) of atrial muscle, initially the longest in ERPs of conduction system in vagotomized animals, was shortened by about 20%. The mechanism of all these alterations is discussed.

[Cerebrovascular accident: differential diagnosis of a compressive spinal hematoma]. / Accident vasculaire cérébral: un diagnostic différentiel de l'hématome médullaire compressif.

We report the case of a 84-year-old patient who developed a monoplegia of the left inferior limb after a spinal anaesthesia for femoral neck's fracture. The magnetic resonance imaging (MRI) carried out in emergency, eliminated a spinal compression. The final diagnosis was a cerebral stroke. This observation leads us to discuss the choice of anaesthesia technical, the various aetiologies of a neurological trouble after spinal anaesthesia. The appearance of clinical signs evoking a spinal haematoma, must make seek by the imagery (MRI or scanner) the signs of spinal compression in order to propose an emergency laminectomy. Finally we insist on the importance but also on the difficulties of the clinical examination in elderly traumatic patients.

[Changes in the affinity of oxygen for hemoglobin during general anesthesia]. / Variations de l'affinité de l'oxygène pour l'hémoglobine au cours de l'anesthésie générale.

The well known effects of the lowering of the intraerythrocyte 2, 3, diphosphoglycerate (2, 3, DPG) level and hypothermia, on the affinity of oxygen for hemoglobin, lead the authors to study the influence of these parameters on this affinity during general anesthesia. The following observations were made in 15 adult subjects, undergoing prolonged general anaesthesia (average time: 3 hrs. 10 minutes): the dissociation curve of oxyhemoglobin (DCO) by the method of mixing, the intraerythrocyte 2,3, DPG level, the hemoglobin concentration and arterial blood parameters (PO2, PCO2, pH). These measurements were recorded before and after the general anaesthesia. The results were the following: a significant reduction of P50, measured under standard conditions (from 27.64 +/- 1.74 torr to 25.57 +/- 2.28, p less than or equal to 0.01) associated with a decrease in 2,3, DPG (from 0.94 +/- 0.31 mol/mol Hb at 0.64 +/- 0.24 p less than 0.01). Among the factors responsible for this variation in the affinity, it was proved that the volume of blood transfused was of importance as well as a decrease in body temperature during the operation. When the temperature is made to vary from 37 degrees C to 35 degrees C. the P50 ranges from 25.57 +/- 2.28 to 22.86 +/- 0.97 (p less than 0.01). To conclude the authors underline the importance of hypothermia and the volume of blood transfused (average time of preservation = 15 days) on the effects of the affinity of oxygen for hemoglobin.