Anesthesia and analgesia
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Anesthesia and analgesia · Oct 2001
Case ReportsThe inability to detect expired carbon dioxide after endotracheal intubation as a result of one-way valve obstruction of the endotracheal tube.
Failure to tracheally intubate and ventilate the lungs is a major cause of anesthesia morbidity. Expired carbon dioxide monitoring has become a standard for assessing correct endotracheal tube placement. We present a case of failure to detect expired carbon dioxide after successful intubation resulting from a one-way valve obstruction of the endotracheal tube.
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Anesthesia and analgesia · Oct 2001
The dynamics of vascular volume and fluid shifts of lactated Ringer's solution and hypertonic-saline-dextran solutions infused in normovolemic sheep.
Infusions of hyperosmotic-hyperoncotic solutions such as hypertonic saline dextran (HSD) are used in Europe for resuscitation of traumatic shock and perioperative volume support as an adjunct to conventional isotonic crystalloids. Whereas plasma volume expansion of HSD has been measured at single time points after the intravascular volume expansion, the detailed time course of fluid shifts during and after infusions have not been reported. We compared the time course of volume expansion during and after 30-min infusions of 4 mL/kg HSD and 25 mL/kg lactated Ringer's solution (LR) in normovolemic conscious splenectomized sheep. Peak plasma volume (Evans blue and hemoglobin dilution) expansion was similar for HSD (7.8 +/- 0.9 mL/kg) and the larger sixfold volume of LR (7.2 +/- 0.5 mL/kg). However, 30 min after the 30-min infusion (T60), plasma expansion remained larger after HSD (5.1 +/- 0.9 mL/kg) than after LR (1.7 +/- 0.6 mL/kg). Both solutions caused an equivalent diuresis. Intravascular volume expansion efficiency (VEE), defined as milliliter plasma expansion/milliliter fluid infused at 0 (T30), 30 (T60), and 60 (T90) min after infusion ended was 1.8, 1.3, and 0.8, respectively for HSD, whereas LR provided a VEE of only 0.27, 0.07, and 0.07. The relative expansion efficiency of HSD versus LR, calculated as the ratio (VEE(HSD)/VEE(LR)), was 7-fold that of LR at the end of infusion T30, and 20-fold at T60, but decreased to 9-fold by T120. Intravascular volume dynamic studies of different volume expanders in animals and patients may provide anesthesiologists with a new tool for monitoring the effectiveness of fluid therapy. ⋯ Hypertonic saline dextran (HSD) is a new plasma expander recently approved for clinical use in Europe. We compared the plasma volume expansion of HSD versus lactated Ringers (LR) in normovolemic sheep. After a 30 min infusion, HSD was 7 times as effective at expanding volume as an equal volume of LR, but for the next 90 minutes the relative effectiveness of HSD increased to 10-20 times.
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Anesthesia and analgesia · Oct 2001
Oxidative stress status during exposure to propofol, sevoflurane and desflurane.
We evaluated the circulating and lung oxidative status during general anesthesia established with propofol, sevoflurane, or desflurane in mechanically ventilated swine. Blood samples and bronchoalveolar lavage fluid (BAL) specimens were respectively performed via an internal jugular vein catheter and a nonbronchoscopic BAL for baseline oxidative activity measurements: malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPX). A 4-h general anesthesia was then performed in the three groups of 10 swine: the Propofol group received 8 mg x kg(-1) x h(-1) of IV propofol as the sole anesthetic; the Desflurane group received 1.0 minimum alveolar concentration of desflurane; and the Sevoflurane group received 1.0 minimum alveolar concentration of sevoflurane. We observed significantly larger levels of MDA in plasma and BAL during desflurane exposure than with the other anesthetics. We also observed smaller concentrations of circulating GPX and alveolar GPX. We found a significant decrease for MDA measurements in the plasma and the pulmonary lavage during propofol anesthesia. We also found larger values of GPX measurements in the serum and the pulmonary lavage. No significant changes were observed when animals were exposed to sevoflurane. No significant changes were found for circulating concentrations of SOD during exposure to all anesthetics. In this mechanically ventilated swine model, desflurane seemed to induce a local and systemic oxidative stress, whereas propofol and sevoflurane were more likely to have antioxidant properties. ⋯ Superoxide is an unavoidable byproduct of oxygen metabolism that occurs in various inflammatory reactions. Inhalation of volatile anesthetics under mechanical ventilation induces an inflammatory response. We evaluated the bronchoalveolar and systemic oxidative stress in swine during exposure to propofol and newer volatile anesthetics. Desflurane induces more lipid peroxidation than do the other anesthetics.
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Anesthesia and analgesia · Oct 2001
The synergistic interaction between midazolam and clonidine in spinally-mediated analgesia in two different pain models of rats.
Both midazolam, a benzodiazepine gamma-aminobutyric acid type A receptor agonist, and clonidine, an alpha2-adrenergic receptor agonist, induce spinally-mediated analgesia. We investigated the analgesic interaction of spinally-administered midazolam and clonidine in their effects on acute and inflammatory nociception. Rats implanted with lumbar intrathecal catheters were injected intrathecally with saline (control), midazolam (1 to 100 microg), or clonidine (0.1 to 3 microg) to test for their responses to thermal stimulation to the tail (tail-flick test) and subcutaneous formalin injection into the hind paw (formalin test). The effects of the combination of midazolam and clonidine on both stimuli were tested by isobolographic analysis by using the 50% effective doses. The general behavior and motor function were examined as side effects. When combined, the 50% effective doses of midazolam (clonidine) decreased from 1.57 microg (0.26 microg) to 0.29 g (0.05 microg) in the tail-flick test and from 1.34 microg (0.12 microg) and 1.21 microg (0.13 microg) to 0.05 microg (0.005 microg) and 0.13 microg (0.015 microg) in Phase 1 and 2 of the formalin test, respectively. Side effects did not increase by using the combination. These results suggest a favorable combination of intrathecal midazolam and clonidine in the management of acute and inflammatory pain after proper neurotoxicologic studies. ⋯ Spinally-administered midazolam, a benzodiazepine, and clonidine, an alpha2-adrenergic receptor agonist, have significant synergistic effects on thermally-induced acute and formalin-induced inflammatory pain.
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Anesthesia and analgesia · Oct 2001
Randomized Controlled Trial Comparative Study Clinical TrialLevobupivacaine combined with sufentanil and epinephrine for intrathecal labor analgesia: a comparison with racemic bupivacaine.
We performed a randomized, double-blinded study to compare levobupivacaine with racemic bupivacaine for labor analgesia. Eighty term parturients received either levobupivacaine 0.125% or racemic bupivacaine 0.125%, to which was added sufentanil 0.75 microg/mL and epinephrine 1.25 microg/mL. As part of a combined spinal-epidural procedure, 2 mL of this mixture was initially injected intrathecally, and the same solutions were subsequently administered epidurally. For both combinations, onset until the first painless contraction was 4 to 5 min. Most patients were pain free during the second contraction. The duration of initial spinal analgesia was 93.5 +/- 20 min and 94.7 +/- 31 min for levobupivacaine and racemic bupivacaine, respectively. The duration of analgesia for the first epidural top-up dose was also similar in the two groups. Total local anesthetic requirements during labor were not different. The only major difference observed was the absence of motor impairment in levobupivacaine-treated parturients as compared with the Racemic Bupivacaine group, in which the incidence of a Bromage-1 motor block was 34%. Other side effects and obstetric or neonatal outcomes were not different between groups. Intrathecal levobupivacaine has a similar clinical profile as racemic bupivacaine, but at equal doses it produced less motor block. ⋯ When used intrathecally and epidurally for labor analgesia, levobupivacaine had the same clinical profile as racemic bupivacaine, but at equal doses it produced less motor block.