Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialAssessing neuromuscular block at the larynx: the effect of change in resting cuff pressure and a comparison with video imaging in anesthetized humans.
Neuromuscular block (NMB) at the larynx has been assessed by measuring the cuff pressure (CP) in an endotracheal tube (ETT) placed between the vocal cords. In this study, we evaluated the decrease in resting cuff pressure (RCP) after the administration of rocuronium and the effect of this decrease on the assessment of NMB, and we compared CP measurement with an alternative technique, video imaging (VI). In 20 patients, NMB was determined at the hand by mechanomyography and at the larynx initially by CP and subsequently by VI, recording images using a fiberoptic bronchoscope via a laryngeal mask. Train-of-four stimuli were applied at both sites. After baseline measurements, the ETT was replaced, and rocuronium was infused to achieve a steady-state 50% (n = 10) or 75% (n = 10) block at the hand. CP measurements were recorded before and after restoration of RCP to prerocuronium pressure, followed by further VI measurements. The mean RCP decreased from 21 +/- 4 to 12 +/- 5 mm Hg after rocuronium. At 50% block at the hand, the CP estimate of block at the larynx with reduced RCP was 62% +/- 18%, and that after restoring RCP was 29% +/- 13%; VI estimated 27% +/- 14% block. At 75% block at the hand, CP and VI estimated 52% +/- 11% and 46% +/- 9% block, respectively (RCP maintained). We conclude that RCP decreases after the administration of rocuronium, that restoring RCP significantly alters CP estimates of NMB, and that VI is in agreement with CP measurement if RCP is maintained at prerelaxant values. ⋯ In this study, we show that a muscle relaxant-induced decrease in resting tension at the larynx may confound the assessment of neuromuscular block by cuff pressure measurement. The preliminary data suggest that video imaging may provide a suitable alternative to cuff pressure measurement to assess neuromuscular block at the larynx.
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialAssessment of the level of sensory block after subarachnoid anesthesia using a pressure palpator.
In a cross-over study, we compared two methods of assessing the level of sensory block during subarachnoid anesthesia: the traditional pinprick sensation or a novel pressure palpator exerting a pressure of 650 g. Fifty patients scheduled for transurethral surgery under subarachnoid anesthesia were randomly assigned to be tested for spread of sensory block. In Group 1, the pressure palpator was followed by pinprick; in Group 2, the reverse sequence was used. Evaluation was performed 15 and 25 min after the subarachnoid injection of 2 mL of 5% lidocaine hyperbaric solution. In Group 1, the level of sensory block assessed with the pressure palpator was 1.7 +/- 3.2 cm (0.5 +/- 1.2 dermatomes) higher than that with the pinprick at 15 min, and 2.2 +/- 3.4 cm (0.6 +/- 1.0 dermatomes) higher than that with the pinprick 25 min after the block. In Group 2, the difference was accentuated. The level of sensory block assessed by pinprick 15 min after subarachnoid lidocaine was 5.7 +/- 4.8 cm (1.2 +/- 0.9 dermatomes) lower than the level with the pressure palpator, and 4.2 +/- 3.3 cm (0.9 +/- 0.6 dermatomes) lower than that with the pressure palpator at 25 min. In all instances, the pressure palpator gave a significantly higher assessment than the pinprick. We conclude that the pressure palpator, when preceded by the pinprick test, is associated with an increased threshold. This method may be useful in assessing the sensory block produced by subarachnoid anesthesia. ⋯ A novel pressure palpator that maintains the integrity of the epidermis was used to assess the level of sensory block after subarachnoid anesthesia and was compared with the standard method of the pinprick sensation. This method assessed the block consistently higher than the pinprick method, but it may have advantages as a noninvasive sensory test.
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Anesthesia and analgesia · Feb 1999
Comparative Study Clinical Trial Controlled Clinical TrialDetermination of an effective dose of intrathecal morphine for pain relief after cesarean delivery.
Very small doses of intrathecal (i.t.) morphine (25-200 microg) have been used in an effort to provide effective postoperative pain relief while minimizing side effects after cesarean delivery. We performed a double-blinded study in 40 patients presenting for elective cesarean delivery in which i.t. morphine was administered along with oral hydrocodone/acetaminophen and other medications commonly administered after cesarean delivery. We administered i.t. morphine by up-down sequential allocation of doses. For the purposes of this study, adequate postoperative analgesia was defined as comfort not requiring i.v. morphine for 12 h after spinal anesthesia with bupivacaine, fentanyl, and morphine. In addition, a time and cost comparison was performed for study patients receiving intrathecal morphine compared with a historical group of patients receiving patient-controlled analgesia with i.v. morphine. We were unable to determine with meaningful precision a dose of i.t. morphine to provide analgesia in this context. However, very small doses of i.t. morphine combined with oral hydrocodone/acetaminophen and other medications commonly prescribed after cesarean delivery provided postoperative pain relief with no more time commitment than patient-controlled analgesia (148 +/- 61 vs 150 +/- 57 min) and with significantly less acquisition cost ($15.13 +/- $4.40 vs $34.64 +/- $15.55). ⋯ When used along with oral analgesics, very small doses of spinal morphine provide adequate pain relief after cesarean delivery. Spinal anesthetics, oral analgesics, and other medications commonly prescribed to treat side effects after cesarean delivery contribute significantly to this analgesia. When small doses of spinal morphine are used in this setting, they provide adequate analgesia and patient satisfaction that is time- and cost-effective.
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialSomatosensory evoked potential monitoring used to compare the effect of three asymmetric sternal retractors on brachial plexus function.
We compared the effect of three different asymmetric sternal retractors on brachial plexus dysfunction using intraoperative somatosensory evoked potentials (SSEPs). We studied 60 patients undergoing coronary bypass and internal mammary harvest. Assessment of brachial plexus function was performed pre- and postoperatively. Patients were assigned the use of a Pittman (MN Scientific Instruments Inc., Minneapolis, MN), Rultract (Rultract Inc., Cleveland, OH), or Delacroix-Chevalier (Delacroix-Chevalier, Paris, France) asymmetric sternal retractor for internal mammary exposure. SSEP changes from baseline during asymmetric retractor use and removal were determined, and average changes were compared among the retractor groups. Patient demographics and baseline SSEP values were similar. Fewer patients in the Delacroix-Chevalier group had decreases in SSEP amplitudes after retractor placement. Of the patients in the Rultract and Pittman groups, 45% and 25%, respectively, had amplitude decreases of >50%, compared with only 5% of the Delacroix-Chevalier patients. Three patients in both the Pittman and Rultract groups and one patient in the Delacroix-Chevalier group suffered brachial plexus symptoms postoperatively. We conclude that the Delacroix-Chevalier retractor is associated with less neurophysiologic evidence of brachial plexus dysfunction during asymmetric sternal retraction compared with either the Pittman or Rultract sternal retractors. ⋯ We used somatosensory evoked potentials to assess the effect of several different asymmetric sternal retractors on brachial plexus dysfunction and to determine which produced the least evidence of nerve damage during surgical exposure of the internal mammary artery.
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialThe effects of prostaglandin E1 on intraoperative temperature changes and the incidence of postoperative shivering during deliberate mild hypothermia for neurosurgical procedures.
We investigated the effects of i.v. prostaglandin E1 (PGE1) on intraoperative changes of core temperature and the incidence of postoperative shivering in neurosurgical patients undergoing deliberate mild hypothermia. Eighty-three patients were randomly assigned to one of three groups: patients in the control group did not receive PGE1, whereas patients in the PG20 group and PG50 group received PGE1 at a dose of 0.02 and 0.05 microg x kg(-1) x min(-1), respectively. The administration of PGE1 was started just after the induction of anesthesia and continued until the end of anesthesia. Anesthesia was maintained with nitrous oxide in oxygen, sevoflurane, and fentanyl. After the induction of anesthesia, patients were cooled using a water blanket and a convective device blanket. Tympanic membrane temperature was maintained at 34.5 degrees C. During surgical wound closure, patients were rewarmed. Intraoperative changes in tympanic membrane and skin temperatures and the incidence of postoperative shivering were compared among groups. Demographic and intraoperative variables were similar among groups. There were no significant differences in tympanic temperatures among groups at each point during the operation. Skin temperature 30 min after rewarming and just after tracheal extubation was significantly lower in the PG20 group than in the PG50 group. Postoperative shivering was more frequent in the PG20 group (43%) than in the control (13%) and PG50 (17%) groups. These results suggest that the intraoperative administration of PGE1 does not affect changes in core temperature during deliberate mild hypothermia and that PGE1 at a dose of 0.02 microg x kg(-1) x min(-1) may increase the occurrence of postoperative shivering. ⋯ Deliberate mild hypothermia has been proposed as a means of providing cerebral protection during neurosurgical procedures. Vasodilating drugs may be used during deliberate mild hypothermia to maintain peripheral circulation and to enhance the cooling and rewarming rate. In the present study, however, we found no benefit from i.v. prostaglandin E1 administration during deliberate mild hypothermia in neurosurgical patients.