Anesthesiology
-
Comparative Study
Which vasopressor should be used to treat hypotension during magnesium sulfate infusion and epidural anesthesia?
Ephedrine restores and/or protects uterine blood flow and fetal well-being in laboratory animals. In contrast, alpha 1-adrenergic agonists worsen uterine blood flow and fetal condition. We previously demonstrated that magnesium sulfate (MgSO4) attenuates the detrimental effects of phenylephrine on uterine vascular resistance in gravid ewes. ⋯ Phenylephrine significantly increased uterine vascular resistance when compared with NS-control, but ephedrine did not. As a result, fetal pH and PO2 were significantly greater during ephedrine infusion than during infusion of NS-control. Fetal pH was stable during ephedrine infusion, but it continued to decrease during phenylephrine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
-
Comparative Study
A comparison in a lung model of low- and high-flow regulators for transtracheal jet ventilation.
There is widespread agreement that transtracheal jet ventilation (TTJV) using a percutaneously inserted intravenous (iv) catheter through the cricothyroid membrane is a simple, quick, relatively safe, and extremely effective treatment for the situation in which neither ventilation nor intubation can be achieved. No study has reported whether a low-flow pressure-reducing regulator (LFR) can provide enough driving pressure and flow under a variety of clinical circumstances for adequate TTJV. We determined, using a high-flow regulator (HFR) as our control, the tidal volume (VT) (measured by integrating a pneumotachograph signal) that a LFR could deliver via a Carden jet injector through 14- and 20-G iv catheters initially at an inspiratory:expiratory ratio (I:E) = 1:1 (unit of time = 1 s) in a mechanical model that had varying lung compliance (Cset, 10-100 ml/cmH2O) and airway diameters (proximal trachea 15.0, 4.5, or 3.0 mm ID and distal mainstem bronchi 9.0 or 4.5 mm ID). ⋯ Decreasing Cset (with the largest airway diameter) and decreasing airway diameter (at Cset = 50 ml/cmH2O) over the full range studied resulted in approximately a 45-80% decrease in VT for all iv catheter/regulator combinations. Increasing Cset and narrowing airway diameter over the full range studied resulted in a progressive increase in end-expiratory volume (EEV) for all iv catheter/regulator combinations. The I:E ratio was also varied from 1:3 to 3:1 (unit of time = 1 s) using the 14-G catheter at Cset = 50 ml/cmH2O with both regulators at the extremes of the proximal tracheal diameters (15.0 and 3.0 mm ID), and we found that jet ventilation through a proximal tracheal diameter of 3.0 mm with the HFR at I:E ratios = 1:1 and 3:1, EEV exceeded the capacity of the mechanical lung (4,000 ml).(ABSTRACT TRUNCATED AT 400 WORDS)
-
Although the clinical properties of propofol have been studied extensively, the pharmacodynamics have not yet been described fully. We studied the propofol concentration-effect relationships for loss of eyelash reflex, loss of consciousness, and hemodynamic changes in 18 female patients, ASA physical status 1, aged 20-49 yr. Propofol was given by computer-controlled infusion. ⋯ The systolic and diastolic blood pressure decreased with increasing blood propofol concentration. The correlation coefficients for the decrease in systolic and diastolic blood pressure versus the blood propofol concentration were r2 = -0.663 and r2 = -0.243, but heart rate did not change. In conclusion, propofol concentrations inducing loss of eyelash reflex are less than those inducing loss of consciousness.
-
Difficult tracheal intubation, often unexpected, has been identified as the commonest contributory factor to anesthetic-related maternal death. The ability to predict such cases preoperatively would be of great value. Preoperative airway assessment and potential risk factors for difficult tracheal intubation were recorded in 1,500 patients undergoing emergency and elective cesarean section under general anesthesia. ⋯ Multivariate analysis removed obesity and missing and single maxillary incisors as risk factors. Obesity was eliminated because of its strong association with short neck. The probability of experiencing a difficult intubation for various combinations of risk factors was determined.(ABSTRACT TRUNCATED AT 250 WORDS)
-
When systemic cooling and rewarming are performed during cardiopulmonary bypass (CPB), the pulmonary artery temperature typically decreases after CPB. This decrease may be rapid enough to cause substantial underestimation of cardiac output (CO) measured by thermodilution, due to changing baseline temperature during the thermodilution measurement. In 16 patients undergoing CPB for coronary artery grafts, digital recording of pulmonary artery temperature was done during room-temperature thermodilution CO (TDCO) injections. ⋯ At 30 min the temperature change was -0.012 degrees C/min (not significant), and CO error was -0.13 +/- 0.14 l/min. Duration of CPB was 104 +/- 30 min, with rewarming for 44 +/- 13 min; the average minimum bladder temperature was 25.1 +/- 2.3 degrees C during cooling and 36.7 +/- 0.7 degrees C at the end of CPB. Under these conditions TDCO measurements within the first 10 min after CPB often underestimate the true CO.