Subject(s)
Anesthesiology/economics , Income Tax , International Educational Exchange , Humans , United Kingdom , United StatesABSTRACT
Changes in aortic blood flow were measured in rabbits with both normal and surfactant depleted lungs in order to elucidate the effect of different modes of ventilation on the circulation while optimizing arterial oxygenation (PaO2). Conventional mechanical ventilation (CMV), reversed inspiratory to expiratory ratio of CMV (IRV), high frequency positive pressure ventilation (HFV), and high frequency oscillation (HFO) were used. Normocapnia was maintained throughout during different modes of ventilation. In normal lungs the aortic blood flow during IRV was significantly lower with similar levels of PaCO2 compared with CMV, HFV, and HFO. In lavaged lungs, without positive end-expiratory pressure (PEEP), the aortic blood flow during CMV was significantly higher than with other modes of ventilation. When 10 cm H2O of PEEP was applied, the PaO2 increased maximally to normal values at all modes of ventilation, but the aortic blood flow was significantly reduced (P < 0.05) during CMV and IRV compared to HFV and HFO. The aortic blood flows at 5 cm H2O of PEEP were very similar during CMV, HFV, and HFO but significantly reduced during IRV. This study showed that at an optimal arterial oxygenation with higher PEEP levels, maintenance of aortic blood flow was maximal during HFV and HFO.
Subject(s)
Respiration, Artificial/methods , Respiratory Insufficiency/therapy , Animals , Blood Gas Analysis , Disease Models, Animal , High-Frequency Ventilation , Positive-Pressure Respiration , Pressure , Pulmonary Circulation/physiology , Pulmonary Gas Exchange/physiology , Pulmonary Surfactants/deficiency , Rabbits , Respiration/physiology , Respiratory Insufficiency/blood , Respiratory Insufficiency/physiopathologyABSTRACT
We compared high frequency ventilation (HFV) to conventional mechanical ventilation (CMV) under normoxic and normocapnic condition in surfactant depleted rabbits with bilateral pneumothoraces. We hypothesized that lower airway pressures would be required with HFV under these conditions. We applied CMV and HFV in 8 anaesthetized rabbits with a prototype ventilator at frequencies of 30, 100, 200, and 300 cycles/min. A positive end-expiratory pressure (PEEP) just below the pressure sufficient to open the air leak from the pneumothoraces was applied at all frequencies. Airway pressures, gas exchange, heart rate, and mean arterial pressure were recorded. Peak airway pressure decreased significantly from 2.50 to 2.10 kPa when the frequency of ventilation was increased from 30 to 300 cycles/min. There were no significant changes in mean airway pressure, PaO2, arterial pH, heart rate, and mean arterial pressure when HFV was compared to CMV. In conclusion, during HFV peak airway pressures measured at the mouth were decreased. Our ability to maintain adequate gas exchange in the face of ongoing pulmonary air leaks may reflect lower alveolar pressures.
Subject(s)
Blood Pressure/physiology , Heart Rate/physiology , Lung/physiopathology , Pneumothorax/physiopathology , Pulmonary Gas Exchange/physiology , Respiration, Artificial , Animals , High-Frequency Ventilation , Hydrogen-Ion Concentration , Lung/metabolism , Pneumothorax/pathology , Pneumothorax/therapy , Positive-Pressure Respiration , Pressure , Pulmonary Surfactants/deficiency , RabbitsABSTRACT
Sixty patients who required fibreoptic nasotracheal intubation were studied. Arterial oxygen saturation, arterial blood pressure and heart rate were monitored continuously during fibreoptic intubation under deep halothane anaesthesia. There were significant decreases (p less than 0.001) in arterial blood pressure and heart rate despite administration of intravenous colloid and atropine. Almost one third of the patients (18 out of 60) suffered a decrease in arterial oxygen saturation below 90% during the intubation sequence and in five patients the saturation fell below 80%. The episodes of desaturation were not related to the induction-intubation time or to the grade of laryngeal visibility at direct laryngoscopy.
Subject(s)
Anesthesia, General , Blood Pressure/physiology , Heart Rate/physiology , Intubation, Intratracheal , Oxygen/blood , Adolescent , Adult , Aged , Aged, 80 and over , Female , Fiber Optic Technology , Humans , Male , Middle Aged , Partial Pressure , Spinal Diseases/surgeryABSTRACT
The density of a drug in solution cannot be determined from a simple formula or from physicochemical tables, because it depends on the physical state of that substance in solution. The densities of agents which have been reported to be administered by the intrathecal route were measured at room and body temperatures. The results were compared with the density of cerebrospinal fluid. At room temperature, most drugs were isobaric with respect to cerebrospinal fluid, but as drugs warmed to body temperature they became relatively hypobaric.
Subject(s)
Anesthesia, Spinal , Anesthetics, Local/chemistry , Analgesics, Opioid/chemistry , Baclofen/chemistry , Body Temperature , Cerebrospinal Fluid/chemistry , Clonidine/chemistry , Droperidol/chemistry , Humans , Methadone/chemistry , Midazolam/chemistry , Naloxone/chemistry , Specific Gravity , TemperatureABSTRACT
Pain on injection of propofol was assessed in a controlled, randomised study of 273 patients. They received either lignocaine 10 mg, procaine 10 mg or isotonic saline 0.5 ml, 15 seconds before the injection of propofol into a vein on the back of the hand. The incidence of pain on injection in the control group (51%) was comparable with other studies. Lignocaine and procaine both significantly reduced the pain (35% and 34% respectively, p less than 0.05) but there was no statistical difference between these two groups.
