British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients.
We have compared four tests for assessing airway sealing pressure with the laryngeal mask airway (LMA) to test the hypothesis that airway sealing pressure and inter-observer reliability differ between tests. We studied 80 paralysed, anaesthetized adult patients. Four different airway sealing pressure tests were performed in random order on each patient by two observers blinded to each other's measurements: test 1 involved detection of an audible noise; test 2 was detection of end-tidal carbon dioxide in the oral cavity; test 3 was observation of the aneroid manometer dial as the pressure increased to note the airway pressure at which the dial reached stability; and test 4 was detection of an audible noise by neck auscultation. ⋯ Inter-observer reliability of all tests was classed as excellent. The manometric stability test had a higher mean airway sealing pressure (P < 0.0001) and better inter-observer reliability (P < 0.0001) compared with the three other tests. We conclude that for clinical purposes all four tests are excellent, but that the manometric stability test may be more appropriate for researchers comparing airway sealing pressures.
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Randomized Controlled Trial Clinical Trial
Thrombelastogram reveals hypercoagulability after administration of gelatin solution.
We have compared the effects of gelatin, low molecular weight hydroxyethyl starch (HES) or albumin on tests of haemostasis and on the thrombelastogram in 42 ASA I patients undergoing total hip or knee replacement. Patients were allocated randomly to receive one of the three blood substitutes to obtain moderate intraoperative haemodilution. Blood loss and packed red cell infusion was the same in each group. ⋯ Platelets were slightly but significantly lower after HES. Haemodilution was comparable between groups. TEG showed a state of hypercoagulability in the gelatin group with a significant decrease in r, r + k and an increase in alpha angle.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of midwife top-ups, continuous infusion and patient-controlled epidural analgesia for maintaining mobility after a low-dose combined spinal-epidural.
We studied 133 women given a combined spinal-epidural for analgesia in labour. The initial intrathecal dose contained bupivacaine 2.5 mg with fentanyl 25 micrograms. When the mothers were comfortable, they were allocated randomly to one of three groups: continuous infusion (group Cl, n = 46), midwife top-ups (group MW, n = 43) or patient-controlled epidural analgesia (group PCEA, n = 44), to maintain analgesia throughout labour. ⋯ Four hours after combined spinal-epidural analgesia, 88.1% of women could SLR in group MW, 83.7% in group PCEA and 57.8% in group Cl (P = 0.002). Total use of bupivacaine was highest in group Cl (mean 11.3 (SD 3.3) mg h-1) compared with group MW (7.5 (3.1) mg h-1) and group PCEA (9.1 (2.1) mg h-1) (P < 0.001). Analgesia was similar between groups and overall satisfaction was equally high.
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We have examined the response of lumbar dorsal horn cells to a noxious mechanical stimulus during differential delivery of isoflurane to the brain and spinal cord of goats. We hypothesized that isoflurane, acting in the brain, would depress dorsal horn neuronal responses to a noxious mechanical stimulus applied to the hindlimb. Eight goats were anaesthetized with isoflurane and neck dissections performed which allowed cranial bypass. ⋯ When the torso isoflurane concentration was 1.3%, decreasing cranial isoflurane from 1.3% to 0.3% did not significantly affect dorsal horn responses (from mean 325 (SD 262) to 379 (412) impulses min-1; P < 0.05). However, when torso isoflurane was 0.8%, decreasing cranial isoflurane from 1.3% to 0.3% increased mean evoked dorsal horn activity by 42% (388 (359) to 551 (452) impulses min-1; P < 0.05). These data suggest that the major effect of isoflurane on dorsal horn responses to noxious stimuli is direct, but there is an indirect effect occurring via descending projections from supraspinal regions.
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We have investigated gas composition during simulated inhalation induction with sevoflurane to elucidate possible mechanisms of incidental prolonged induction times and airway irritation. Using a circle system, 8% sevoflurane in oxygen 6 litre min-1 was washed into an absorbing canister filled with fresh soda lime containing 2.9% KOH (Draegersorb, 'D') or no KOH (< 0.01%, Sofnolime, 'S'). The absorbent was dried by oxygen 20,000 litre before every second experiment. ⋯ Sevoflurane degradation is aggravated by a high KOH content of the lime. The observed airway irritation may be caused by formic acid, which is generated in isomolar concentrations with methanol (Cannizzaro reaction). The amount of compound A found with dry KOH-containing lime is unlikely to be noxious.