Anaesthesia
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We have investigated the factors predicting umbilical arterial pH (UA pH) and standard base excess (UA BE) in 337 consecutive elective Caesarean sections performed under spinal anaesthesia. Multiple linear regression analysis was performed with UA pH and UA BE as the dependent factors. ⋯ The significant factors predicting UA BE were: use of ephedrine and the interaction between ephedrine use and duration of hypotension (adjusted R2 = 0.52, F15,321 = 25.0, p < 0.0001). We conclude that, in order to minimise the risk of fetal acidosis, ephedrine should not be used before delivery, uterine incision-to-delivery time should be as short as possible, and alpha-agonists such as metaraminol or phenylephrine should be used to minimise both the magnitude and duration of hypotension.
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Capnography is considered essential in the management of mechanically-ventilated patients. Helium, as an adjunct to mechanical ventilation, is the subject of renewed interest and used increasingly. However, helium affects the performance of infrared capnometry. ⋯ We found that addition of helium to the gas mixture caused all three capnographs to underestimate the concentration of carbon dioxide. The underestimation increased as the proportion of helium increased. The maximum underestimation (30%) occurred in a 79:21 helium/oxygen mixture.
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Over a period of one year, a weekly telephone survey identified 161 stable patients with weaning delay (defined as patients ventilated for at least 6 h per day for more than 2 weeks) in intensive care units in the Northern Region of England. Their median age was 69 years (range 21-88 years). Sixty patients (37%) were admitted with medical conditions, 89 (55%) were postoperative patients, whereas 12 (8%) were surgical but required non-operative admission. ⋯ Twenty patients (12%) required more than 28 days of respiratory support. These patients occupied on average 6.0% of available intensive care unit beds in the region. This study suggests that in the Northern Region of England there are a significant number of stable but ventilator-dependent patients occupying intensive care beds.