Anaesthesia
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We assessed the ability of palpating the radial arterial pulse and observing the oximeter trace to estimate the automated non-invasive systolic pressure reading in 20 healthy female volunteers and 20 parturients undergoing spinal anaesthesia for elective caesarean section. Using real-time values of cuff pressure during inflation/deflation, the pressure was recorded when the manually palpated radial arterial pulse or pulse oximeter waveform disappeared and reappeared. ⋯ In the parturients, the bias/precision was -19.0/47.6 mmHg (inflation) and -15.5/51.0 mmHg (deflation) for arterial palpation, and 22.6/16.1 mmHg (inflation) and -14.2/19.9 mmHg (deflation) for oximetry. Our results suggest that neither method is accurate at estimating the non-invasive systolic pressure, with all except oximetry (inflation) underestimating it by approximately 10-20 mmHg and with poor precision.
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We compared the propofol dose causing loss of verbal response and suppression of bispectral index to 50, between 50 white and 50 black patients, aged 18-65 years. Propofol was administered at 40 mg.kg⁻¹.h⁻¹ and reduced to 8 mg.kg⁻¹.h⁻¹ when bispectral index fell to 50. We recorded heart rate and mean arterial pressure for 15 min in total and calculated, for this period, maximal percentage change from baseline for each. ⋯ Corresponding figures for maximal percentage change in heart rate were 14.1 (12.6) % and 7.5 (14.0) % (p = 0.015). Other differences were non-significant. The dose of propofol required for loss of verbal response, but not for suppression of bispectral index to 50, is lower in black than in white patients.
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Venous air embolism activates platelets in vitro and can evoke platelet dysfunction in swine. We tested the hypothesis that venous air embolism during semi-sitting craniotomy induces thrombocytopenia in humans. ⋯ In age-matched controls without venous air embolism mean (SD) platelet count did not change (254 (82) × 10⁹ l⁻¹ vs. 250 (97) × 10⁹ l⁻¹ (NS). While mean (SD) haematocrit fell slightly in both groups (venous air embolism: 0.40 (0.05) to 0.32 (0.04), p <0.001; no venous air embolism: 0.41 (0.04) to 0.35 (0.05), p < 0.001), normalising platelet count to haematocrit did not alter the results.
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Letter Case Reports
Unexpected failure of rocuronium-mediated neuromuscular blockade.