Analytic study of laryngeal mask airway cuff pressure on the pharyngeal mucosa and postoperative adverse airway events

Sixty patients scheduled in order to calculate the pressure exerted by the cuff upon the pharyngeal mucosa and incidence of adverse airway events [hypoxia, hypercarbia, coughing, regurgitation, vomiting, airway obstruction, hiccup or biting]. At the end of surgery patients were interviewed about pharyngolaryngeal morbidity [sorethroat, dysphagia and dysphonia] immediately before leaving the post- anesthesia care unit and 24 hours following surgery. Patients were divided into three groups, each 20 patients were studied for each of the size 2, 3 and 4 laryngeal mask airway [LMA]. A noninvasive method was used to compare intracuff pressures. Cuff inflation with normal injection volumes recommended resulted in the residual volumes of the cuffs being exceeded. The intracuff pressures recorded with the mask in situ at these normal injection volume were in the range of 103-251 mmHg. The calculated transmitted mucosal pressures were substantial for all three sizes of the cuff and potentially exceeded the capillary perfusion pressure of the adjacent pharyngeal mucosa, despite apparent pharyngeal accommodation to the mask. Analysis showed more partial airway obstruction in the LMA size 2 group, also heart rate was slightly higher in LMA size 2 group upon arrival in the post- anesthetic care unit [PACU], otherwise there is no differences in cardio-respiratory responses. Sore throat and dysphagia were more common in the LMA size 2 group. The transmitted pharyngeal mucosal pressure were calculated over the clinical range of injection volumes. Study concluded that in general, emergence characteristics with the laryngeal mask airway are not influenced by volume of air used to inflate, but that postoperative sore throat and dysphagia are more likely at high initial cuff volumes

Stress responses after major surgery in infant: comparison of two analgesic regimens of morphine

Infants under 1 year classified to receive either continuous morphine [CM, 10 microg/kg/h] with three-hourly placebo boluses or intermittent morphine [IM, 30 microg/kg every 3h] with a placebo infusion for postoperative analgesia. Plasma concentration of norepinephrine, insulin, glucose and lactate were measured before and at the end of surgery, 12h and 24h after surgery. Pain was assessed with the comfort scale and visual analogue scale [VAS] with the availability or additional morphine doses. Minor differences occurred between the three groups, IM group in infants aged 6m-1 yr [group 3] having a higher blood glucose concentration [p = 0.003] mean arterial pressure [p = 0.02] and comfort score [p = 0.02] than the CM group. In the neonates, preoperative plasma. Concentration of norepinephrine [p = 0.01] and lactate [p < 0.001] were significantly higher, while the postoperative plasma concentration of insulin significantly higher [p < 0.005] than in the group II and III. Postoperative pain scores [p < 0.003] and morphine consumption [p < 0.001] were significantly lower in the neonates [Group I] than in the group II and III. The study shows that continuous infusion of morphine does not provide any major advantages over intermittent morphine boluses for postoperative analgesia in neonates and infants

comparison of effects and antagonism of vecuronium-induced neuromuscular blockade during sevoflurane and isoflurane anaesthesia

Volatile anaesthetic agents potentiate neuromuscular blocking agents and retard their rate of reversal. Patients divided into three groups, a control group [n= 18], isoflurane group [n=24] and sevoflurane group [n = 24]. The study examined the interactions of 1 MAC of isoflurane and sevoflurane [66% nitrous oxide in oxygen] with vecuronium. Accurate baseline value values [100% reference values for amplitudes of first response [T[1]] and ratio of fourth to the first T of response [T[4]-T[1]] were obtained. The dose response curves for vecuronium constructed in 54 patients [18 patients each]. The curves for both isoflurane and sevoflurane had a significant lefward shift compared with that for fentanyl-nitrous oxide anaesthesia [P<0.01] Fig. 1]. When surgery was complete, recovery from neuromuscular block was allowed to occur spontaneously in three groups [part 1]. When the amplitude of the first response T[1] had recovered to 50% of control, subsequently we compared the spontenous recovery rate of the ratio of the fourth to the first TOF response [T[4]-T[1]] at 3 min intervals during the 15-min period in the presence of two volatile anaesthetics or after discontinuation of administration of anaesthetics [Fig.2]. Times from reversal to T[1]=25, 50 and 60% and TOF =0.6 were recorded, mean [SD] times to train of four ratio =0.6 in isoflurane and sevoflurane groups were 330 [134] and 353 [130] s, respectively. The mean [SD] times to single twich response T[1] = 25, 50 and 60% in the isoflurane group were 50 [35], 103 [40] and 252 [87] s, respectively, and in sevoflurane group were 93 [37], 205[90] and 254 [124] s respectively [Table 2]. The rate of recovery of T[4]: T[1] was significantly greater when both anaesthetics were discontinued. However, this rate was similar for both anaesthetics, suggesting that the mechanism or action or the two anaesthetics is similar. The T[4]: T[1] values recovered spontaneously more rapidly in both stop groups than in both stable groups [P<0.05]. There was no significant differences in the spontaneous T[4]: T[1] recovery rate between the I [stop] and S [stop] groups or between the I [stop] and S [stable] groups [Fig.2]. After completion of the study, residual neuromuscular block was studied [part 2], evoked reversal characteristics of vecuronium using edrophonium and compared them this those obtained following neostigmine. It is concluded that edrophonium antgonizas more rapidly residual vecuronium- induced neuromuscular blockade [Table 3]

Assessement of patient-controlled analgesia using remifentanil as an effective and safe alternative to patient-controlled epiduralúanalgesia for labour

This study compared the administration of intravenous infusion of remifentanil using patient-controlled analgesia [PCA] device for analgesia in normal labour with that of 0.1% bupivacaine plus sufentanil 0.5 microg/ml via patient-controlled epidural analgesia [PCEA]. One hundred healthy pregnant women at term with a single fetus with a vertex fetal presentation were divided in two equal groups to receive either 0.25 microg to 1 microg/kg as bolus dose of remifentanil PCA in a stepwise manner with or without a background infusion [0.025-0.05 microg/kg] or 0.1% bupivacaine and 0.5 microg/ml sufentanil using PCEA. Pain Score on visual analog score [VAS]. Modified bromage scale [0-3]. Level of sensory block, drug use, supplemental boluses and side effects were recorded. Mode of delivery, duration of first and second stages of labour, umblical cord pH, Apger scores of the newborn and a measure of maternal satisfaction were recorded after delivery. VAS pain score during the progress of labour was significantly less in bupivacaine group PCEA [16.9 +/- 13.4mm] compared with the lowest pain scores in remifentanil group recorded at L[1]B[1] bolus 0.25 microg/kg [30.2 +/- 23 mm] and at L[1]B[2] bolus 0.5 microg/kg [24.4 +/- 18 mm] respectively, P<0.01, Maternal satisfaction with the relief of contraction pain was greater in bupivacaine group [90.8 +/- 10.8] than in remifentail group L[1]B[1] 70.20 +/- 20 mm, L[1]B[2] 50.2 +/- 12.8] P<0.0001, as with the relief of delivery pain [bupivacaine group 88.7 +/- 14.1 mm, L[1]B[1] 78.3 +/- 2.3 mm, L[1]B[2] 80.1 +/- 25.2 mm] P < 0.0001. On visual scale: 0 = not satisfied, 100 = fully satisfied. Motor and sensory block were assessed with the progress of labour in bupivacaine group. No differences were seen between the two groups for mode of delivery, maternal blood pressure, fetal heart rate, apger score 0, 5, 10 min and umblical pH. Patients in remifentanil group requested more supplemental boluses to achieve labour analgesia than those in bupivacaine group, adding background infusion at level two or three bolus doses not reduce pain scores but serves only to increase respiratory depression, sedation and opioid side effects [vomiting, nausea and itching]. Delivered as patient-controlled epidural analgesia 0.1% bupivacaine plus 0.5 microg/ml sufentanil are more potent than PCA remifentanil. Remifentanil PCA system [bolus doses 0.25-0.5 microg/kg without a background infusion] may safely provide worthwhile, although incomplete analgesia for labour

Low concentration sevoflurane anaesthesia supplemented with remifentanil: effect on recovery and cognitive function, also sevoflurane and hepatic integrity in elderly patients

The aim of this study was to assess hepatic function in elderly patients anaesthetized with sevoflurane - Nitrous oxide and to compare recovery and psychomotor performance after maintenance of anaesthesia with sevoflurane - nitrous oxide supplemented with remifentanil 80 patients. 70 to 90 yr old, were allocated randomaly to four groups, twenty patients each were allocated to maintenance of anaesthesia with sevoflurane only in concentration necessary to mentain adequate anaesthesia [Group I] with 1.5, 1.0, 0.5 MAC [end tidal] of sevoflurane supplemented with remifentanil. Measurement if cytosolic liver enzyme alpha glutathione S-transferase [alpha GST], the formation of the lidocaine metabolite monoethylglycinexylidide [MEGX] and gastric mucosal tonometery-derived variable as sensitive markers of hepatic function and splachnic perfusion. No significant changes in standard liver enzyme markers were seen throughout the study. Tonometric measurements showed a significant decrease from baseline in regional Pco[2]' regional to arterial difference in Pco[2] and intermucosal PH at 90 min after skin incision, alpha GST concentration increased significantly in group I. A return to base line values in tonometric values and alpha GST levels was seen 24 h postoperatively. MEGX formation did not charge significantly after surgery. The median dosage of ramifentanil required in the last three groups was 0.21, 0.25 and 0.34 mg/kg/min, respectively [P<0.05]. The median times to eye opening were 10.3, 12.7, 11.0 and 6.5 min in the four groups [P<0.05 between the 0.5 MAC and other groups] and for orientation 12.1, 14.9, 12.3 and 8.3 respectively [P<0.05 between 0.5 and 1.5 MAC groups]. There was no significant difference in the mini-mental state assessment scores on the actual discharge times from the recovery ward among the groups. Significantly greater numbers of patients could perform the critical thicker fusion test at 15 min in the group receving the lowest concentration of sevoflurane and the highest doses of remifentanil [p<0.05]. Patients in this group also showed the highest incidence of chest wall rigidity [P<0.003]. We conclude that, liver function in elderly patients is well preserved during sevoflurane anaesthesia, increased serum levels of alpha GST and changes of gastric tonometry-derived variables imply a reduction in splanchnic perfusion, leading to temporary impairment of hepatocyte oxygenation. Also the use of remifentanil with lower concentration of sevoflurane facilitate early recovery, it does not influence discharge time from recovery ward and may be associated with side effects as chest wall rigidity