Anaesthesia and intensive care
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Anaesth Intensive Care · Nov 1992
Comparative StudyDerived oxygen saturations are not clinically useful for the calculation of oxygen consumption.
In critically ill patients, oxygen consumption (VO2) and delivery (DO2) are used to determine optimal haemodynamic management and to grade severity of illness. VO2 may be measured by indirect calorimetry with metabolic gas monitoring systems or derived using the reverse Fick principle. Oxygen saturation (SaO2) may be measured directly by co-oximetry or derived by equations for incorporation into reverse Fick equations. ⋯ When SaO2 was calculated from three logarithmic equations and incorporated into the reverse Fick equations, calculated VO2's were significantly greater (P < 0.001) than those measured by indirect calorimetry. Correlation was poor and wide limits of agreement (-118 to +350 ml/min) were demonstrated. VO2 should ideally be measured by indirect calorimetry in the critically ill, or if reverse Fick is used, SaO2 should be measured by co-oximetry as the use of equations for clinical measurement of SaO2 is clinically suspect.
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Anaesth Intensive Care · Nov 1992
Randomized Controlled Trial Comparative Study Clinical TrialThe effect of epidural blockade on postoperative hypercoagulability following abdominal aortic bypass surgery.
The effect of epidural blockade on postoperative hypercoagulability was assessed in patients undergoing elective abdominal aortic bypass surgery. Twenty patients were randomised to receive general anaesthesia alone, or general anaesthesia plus thoracic epidural blockade with 0.5% bupivacaine. ⋯ Similarly, epidural blockade did not affect the postoperative decrease in antithrombin III. The results suggest that epidural blockade with local anaesthetic agents does not prevent the postoperative hypercoagulability response following abdominal aortic bypass surgery.
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Anaesth Intensive Care · Nov 1992
Randomized Controlled Trial Clinical TrialPropofol induction for laryngeal mask airway insertion: dose requirement and cardiorespiratory effects.
The dosage, haemodynamic and respiratory effects of propofol for laryngeal mask airway (LMA) insertion were investigated. Fifty patients (ASA I-II) were randomly assigned one of four induction doses of propofol (1.5-2.5 mg/kg) delivered over 30 seconds and the first attempt at LMA insertion was made at 90 seconds. The LMA was inserted at 90 seconds in 35 patients and by 300 seconds in 13 others (mean plasma concentration at 90 seconds was 7.7 mcg/ml (no delay) versus 5.2 mcg/ml (insertion delayed), P < 0.01). ⋯ Additional propofol (0.5 mg/kg/30s) was required in 22 patients for LMA insertion or to prevent movement, resulting in propofol concentrations at 120-180 seconds above 7 mcg/ml. Respiratory effects were minor, but MAP decreased by 18 +/- 1.4 mmHg at 90 seconds. Cardiovascular effects did not differ significantly between dosage groups or with the use of additional propofol.
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Anaesth Intensive Care · Nov 1992
Randomized Controlled Trial Clinical TrialProphylactic intramuscular ephedrine prior to caesarean section.
Thirty healthy parturients, having given informed consent, were randomly allocated in a double-blind study to receive an intramuscular injection of either 0.9% sodium chloride (control), ephedrine 25 mg, or ephedrine 50 mg, 30 minutes prior to general anaesthesia for caesarean section. Nine patients (90%) in the 50 mg group and five patients (50%) in the 25 mg group demonstrated reactive hypertension of 20% or greater from control. The mean maximum increase in the 50 mg group was 28.2% (range 4.4-38.3%). ⋯ The associated increase in umbilical arterial base deficit suggests a metabolic component due to fetal asphyxia related to decreased uterine blood flow. We conclude that the prophylactic administration of intramuscular ephedrine prior to spinal anaesthesia is associated with an unacceptably high incidence of maternal hypertension, and should the spinal fail and general anaesthesia be required, also results in adverse neonatal biochemical changes. The technique is therefore not to be recommended.