Anesthesia and analgesia
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Anesthesia and analgesia · Apr 1998
Comparative StudyThe effect of prior dural puncture on cerebrospinal fluid sufentanil concentrations in sheep after the administration of epidural sufentanil.
Sufentanil is a highly lipid soluble opioid that provides potent analgesia when administered in the subarachnoid space. Unfortunately, the penetration of sufentanil into the cerebrospinal fluid (CSF) after epidural administration is poor, and limits its effectiveness for epidural analgesia. Dural puncture may enhance the movement of epidural sufentanil into the subarachnoid space and increase its effectiveness. To determine whether the administration of epidural sufentanil adjacent to a dural puncture results in significantly greater CSF concentrations, 18 adult ewes were studied. Animals in the control group had an epidural catheter placed at the superior border of the pelvis without dural puncture. Animals in the study group had an epidural catheter placed, followed by a dural puncture performed using an 18-gauge Touhy needle. The dural puncture was performed one interspace cephalad to the epidural catheter. One hour after dural puncture, each animal received a loading dose of 0.35 microg/kg of sufentanil (5 microg/mL) through the epidural catheter, followed by an infusion of epidural sufentanil 0.15 microg x kg(-1) x h(-1) for a period of 4 h. After 4 h, CSF was sampled from a site one interspace caudad to the epidural catheter as well as at the cisterna magna. The mean CSF concentration of sufentanil at the level of the pelvis for animals with a dural puncture was 12.1 +/- 3.0 ng/mL compared with 1.8 ng/mL in controls with intact dura. Sufentanil concentrations at the cisterna magna were below the level of detection (0.08 ng/mL) for all animals in both groups. We conclude that an 18-gauge dural puncture significantly increases movement of sufentanil from the epidural to the intrathecal space. This increase in sufentanil concentration at the level of the pelvis was not associated with detectable levels of sufentanil at the brainstem. ⋯ This study addresses the effect of dural puncture on spinal fluid concentrations of sufentanil after epidural administration. A sheep model was used to measure drug concentrations in the spinal fluid at the levels of the pelvis and brainstem after epidural administration. Dural puncture significantly enhanced movement of sufentanil into the spinal fluid at the level of the pelvis, but brainstem concentrations were below the level of detection. Analgesic concentrations of spinal sufentanil in the clinical setting, as well as brainstem concentrations associated with respiratory depression, have yet to be defined.
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Anesthesia and analgesia · Apr 1998
Bacterial colonization and infection rate of continuous epidural catheters in children.
Continuous epidural infusions are widely used for postoperative analgesia in children. We prospectively studied the incidence of bacterial colonization of caudal and lumbar epidural catheters, as well as the incidence of serious systemic and local infection, in 210 children after short-term epidural analgesia. Using aseptic technique, epidural catheters were inserted into either the lumbar or the caudal epidural space based on the preferences of the anesthesia team and/or clinical indication. The integrity of the catheter and overlying transparent dressing site was evaluated by a member of the pediatric pain service at least once a day. The catheters were aseptically removed if the patient had a fever greater than 39 degrees C, if the dressing was compromised, or when epidural analgesia was no longer required. The subcutaneous portion of the catheter was semiquantitatively cultured. Cellulitis (erythema, swelling, purulent discharge, pustule formation, or tenderness) was diagnosed by examination of the epidural insertion site. The mean (+/- SD) age of patients in the caudal catheter group (n = 170) was 3 +/- 3 yr; their mean weight was 13 +/- 11 kg. The mean (+/- SD) age of patients in the epidural catheter group (n = 40) was 11 +/- 4 yr; their mean weight was 36 +/- 23 kg. All catheters remained in place for 3 +/- 1 days (range 1-5 days). There was no serious systemic infection (meningitis, epidural abscess, or systemic sepsis). Of all epidural catheters, 35% (73 of 210) were colonized. Gram-positive colonization was similar in caudal (25%; 43 of 170) and lumbar (23%; 9 of 40) catheters. Gram-negative organisms were cultured from 16% of the caudal catheters (27 of 170) and 3% of the lumbar catheters (1 of 40). In patients treated with caudal epidural catheters, children aged >3 yr were less likely to have colonized epidural catheters than younger children. Age did not affect the probability of developing cellulitis at the insertion site. Although patients aged <3 yr with caudal catheters had a slightly greater risk of cellulitis than children aged >3 yr (14% vs 9%), this association was very weak (P = 0.33). We observed that, despite bacterial colonization of caudal and lumbar epidural catheters, serious systemic and local infection after short-term epidural analgesia did not occur in our study. ⋯ Continuous epidural infusions are widely used for postoperative analgesia in children. We found no serious systemic infections after short-term (3 days) continuous epidural analgesia in children.
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Anesthesia and analgesia · Apr 1998
The influence of acute normovolemic hemodilution on the dose-response and time course of action of vecuronium.
To evaluate the influence of acute isovolemic hemodilution on the dose-response and time course of action of vecuronium, we studied 60 adult patients with and without hemodilution during surgery. The patients with hemodilution underwent major elective plastic surgery with an anticipated surgical loss of more than 600 mL. Anesthesia was induced with thiopental 4-6 mg/kg and fentanyl 2-4 microg/kg i.v. and was maintained with 60% nitrous oxide in oxygen. Further increments of thiopental 2 mg/kg or fentanyl 2 microg/kg were given as required. Acute isovolemic hemodilution in the hemodilution group was induced by drainage of venous blood and an i.v. infusion of lactated Ringer's solution and 6% dextran, during which hematocrit and hemoglobin decreased from 45.7% to 26.2% and from 148.5 g/L to 90.2 g/L, respectively. Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12 s, and the percent depression of T1 response was used as the study parameter. The dose-response relationships of vecuronium in the two groups were determined by using the cumulative dose-response technique. The results showed that during hemodilution, the dose-response curve of vecuronium was shifted to the left in a parallel fashion, and the potency of vecuronium was increased. There were significant differences in the 50%, 90%, and 95% effective doses between the two groups. After the i.v. administration of vecuronium 80 microg/kg, vecuronium-induced neuromuscular block was significantly longer in the patients with hemodilution than in the control patients. The duration of peak effect, clinical duration, recovery index, and total duration in the hemodilution patients were significantly different from those in the control patients. We conclude that hemodilution induces significant changes in the pharmacodynamics of vecuronium. ⋯ We found that patients with hemodilution were 20% more sensitive to vecuronium and had a longer duration of action after the administration of the same dose than the controls. This should be taken into account when vecuronium is used as a muscle relaxant during acute hemodilution.
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Anesthesia and analgesia · Apr 1998
Inhaled prostaglandin E1 for treatment of acute lung injury in severe multiple organ failure.
Acute lung injury is characterized by hypoxemia due to pulmonary ventilation/perfusion-mismatching. I.v. administered prostaglandin E1 (PGE1), a vasodilator with a high pulmonary clearance, has been studied in acute lung injury. Inhalation of the vasodilators nitric oxide and prostacyclin improved oxygenation by selective dilation of the pulmonary vasculature in ventilated lung areas. In the present study, PGE1 inhalation was used for treatment of acute lung injury. Fifteen patients with acute lung injury defined as PaO2/fraction of inspired oxygen (FIO2) <160 mm Hg were treated with PGE1 inhalation in addition to standard intensive care. The drug was continuously delivered via a pneumatic nebulizer. Acute physiology and chronic health evaluation system II and multiple organ failure scores were (mean +/- SEM) 33 +/- 2 and 10 +/- 0.3, respectively. Inhaled PGE1 was administered for 103 +/- 17 h at a dose of 41 +/- 2 microg/h. The PaO2/FIO2 ratio increased from 105 +/- 9 to 160 +/- 17 mm Hg (P < 0.05) and to 189 +/- 25 mm Hg (P < 0.05) after 4 h and 24 h, respectively. PGE1 inhalation decreases in mean pulmonary artery pressure and central venous pressure were not statistically significant. Mean arterial pressure, pulmonary capillary wedge pressure, cardiac output, and heart rate remained unchanged. Intensive care unit mortality was 40%. The present data suggest that inhaled PGE1 is an effective therapeutic option for improving oxygenation in patients with acute lung injury. Whether inhaled PGE1 will increase survival in acute lung injury should be investigated in a controlled prospective trial. ⋯ In patients with severe acute lung injury and multiple organ failure, inhaled prostaglandin E1 improved oxygenation and decreased venous admixture without affecting systemic hemodynamic variables. Controlled clinical trials are warranted.
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Anesthesia and analgesia · Apr 1998
Laryngeal mask airway position and the risk of gastric insufflation.
A potential risk of the laryngeal mask airway (LMA) is an incomplete mask seal causing gastric insufflation or oropharyngeal air leakage. The objective of the present study was to assess the incidence of LMA malpositions by fiberoptic laryngoscopy, and to determine their influence on gastric insufflation and oropharyngeal air leakage. One hundred eight patients were studied after the induction of anesthesia, before any surgical manipulations. After clinically satisfactory LMA placement, tidal volumes were increased stepwise until air entered the stomach, airway pressure exceeded 40 cm H2O, or air leakage from the mask seal prevented further increases in tidal volume. LMA position in relation to the laryngeal entrance was verified using a flexible bronchoscope. The overall incidence of LMA malpositions was 40% (43 of 108). Gastric air insufflation occurred in 19% (21 of 108), and in 90% (19 of 21) of these patients, the LMA was malpositioned. Oropharyngeal air leakage occurred in 42%, and was independent of LMA position. We conclude that clinically unrecognized LMA malposition is a significant risk factor for gastric air insufflation. ⋯ Routine placement of laryngeal mask airways does not require laryngoscopy. In our study, fiberoptic verification of mask position revealed suboptimal placement in 40% of cases. Such malpositioning considerably increased the risk of gastric air insufflation.