Anesthesia and analgesia
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Anesthesia and analgesia · May 1998
Hydroxyethyl starch antibodies in humans: incidence and clinical relevance.
Hydroxyethyl starch (HES) is a plasma expander used for perioperative i.v. fluid management, as well as for resuscitation from trauma and shock. HES is very well tolerated, and the incidence of anaphylactic reactions is lower than with dextran or gelatin. Dextran anaphylaxis is caused by circulating dextran-reactive antibodies (ABs) of the immunoglobin G (IgG) class found in most adults. Histamine release from mast cells induces adverse reactions after gelatin infusion. The cause of adverse reactions due to HES is not yet clear. To investigate AB formation due to HES, we collected sera of 1004 patients at least 14 days after starch administration. Using a highly sensitive enzyme-linked immunoabsorbent assay technique, we found one patient with a low 1:10 titer of HES-reactive ABs (immunoglobin M [IgM] class). Despite repeated HES infusions, no clinical reaction could be detected in this patient. On the basis of a binomial distribution, a one-tailed confidence interval (99%) was used to calculate the percentage of the occurrence of ABs in general with maximum of 33 in 10,000 persons (IgM) and 23 in 10,000 persons (IgG). We suggest that HES-reactive ABs are extremely rare and that they do not necessarily induce anaphylaxis. Other mechanisms may be responsible for adverse reactions due to HES. ⋯ The frequency of antibody formation due to hydroxyethyl starch, a commonly used plasma expander, was prospectively investigated in 1004 patients. Only one patient showed transient antibody formation, which was not harmful to the patient. This low antigenicity could explain the excellent tolerance of hydroxyethyl starch compared with other plasma expanders.
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Anesthesia and analgesia · May 1998
Randomized Controlled Trial Clinical TrialThe effect of varied doses of epinephrine on duration of lidocaine spinal anesthesia in the thoracic and lumbosacral dermatomes.
The efficacy of epinephrine in prolonging spinal analgesia has recently been confirmed in the lumbosacral but not in the thoracic, segments. Most previous studies used doses of epinephrine smaller than 0.3 mg. We studied the effects of 0.2, 0.4, or 0.6 mg of epinephrine added to hyperbaric lidocaine 60 mg in 7.5% dextrose solution for spinal anesthesia. Eighty patients were randomly divided into four groups: Group A received lidocaine without epinephrine, Group B received lidocaine plus 0.2 mL (0.2 mg) of epinephrine 1:1000 solution, Group C received lidocaine plus 0.4 mL (0.4 mg) of epinephrine, and Group D received lidocaine plus 0.6 mL (0.6 mg) of epinephrine. The maximal cephalad sensory level was between T2 and T3 for all groups. The median times for analgesia to regress two and four segments were significantly prolonged in Group D, but not in either Group B or C, compared with those in Group A. Times for regression to T12 and L3 were significantly prolonged in Groups B, C, and D compared with Group A. We conclude that the dose-dependent relationship of spinal analgesia can be applied to epinephrine, and that larger doses prolong lidocaine spinal anesthesia in the thoracic as well as the lumbosacral dermatomes. ⋯ Prolongation of lidocaine spinal analgesia by intrathecal epinephrine is established in the lumbosacral, but not in the thoracic, dermatomes. Three doses of epinephrine--0.2, 0.4, and 0.6 mg--were compared. A dose-dependent response and significant prolongation with the 0.6-mg dose in the thoracic dermatomes were confirmed.
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Anesthesia and analgesia · May 1998
The arterial to end-tidal carbon dioxide gradient increases with uncorrected but not with temperature-corrected PaCO2 determination during mild to moderate hypothermia.
End-tidal carbon dioxide (PETCO2) monitoring is recommended as a basic standard of care and is helpful in adjusting mechanical ventilation. Gas solubility changes with temperature, which might affect the PaCO2 and thereby the gradient between PaCO2 and PETCO2 (PA-ETCO2) under hypothermic conditions. We investigated whether the PA-ETCO2 changes during mild to moderate hypothermia (36 degrees C-32 degrees C) using PaCO2 measured at 37 degrees C (uncorrected PaCO2) and PaCO2 corrected to actual body temperature. We preoperatively investigated 19 patients. After anesthesia had been induced, controlled ventilation was established to maintain normocarbia using constant uncorrected PaCO2 to adjust ventilation (alpha-stat acid-base regimen). Body core temperature was reduced without surgical intervention to 32 degrees C by surface cooling. Continuous PETCO2 was monitored with a mainstream PETCO2 module. The PA-ETCO2 was calculated using the uncorrected and corrected PaCO2 values. During body temperature reduction from 36 degrees C to 32 degrees C, the gradient between PETCO2 and uncorrected PaCO2 increased 2.5-fold, from 4.1 +/- 3.7 to 10.4 +/- 3.8 mm Hg (P < 0.002). The PA-ETCO2 remained unchanged when the corrected PaCO2 was used for the calculation. We conclude that when the alpha-stat acid-base regimen is used to adjust ventilation, the PA-ETCO2 calculated with the uncorrected PaCO2 increases and should be added to the differential diagnosis of widened PA-ETCO2. In contrast, when the corrected PaCO2 is used for the calculation of the PA-ETCO2, the PA-ETCO2 remains unaltered during hypothermia. ⋯ We investigated the impact of induced hypothermia (36 degrees C-32 degrees C) on the gradient between PaCO2 and PETCO2 (PA-ETCO2). The PA-ETCO2 increased 2.5-fold when CO2 determinations were not temperature-corrected. Hypothermia should be added to the differential diagnosis of an increased PA-ETCO2 when the alpha-stat acid-base regimen is used.
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Anesthesia and analgesia · May 1998
The effects of age and gender on the optimal premedication dose of intramuscular midazolam.
We conducted a double-blind study on the effects of age and gender on the optimal premedication dose of i.m. midazolam. We randomly divided 100 male and 100 female patients in each of three age groups: A = 20-39 yr, B = 40-59 yr, and C = 60-79 yr (total 600 patients) into five groups according to midazolam dosage: 0.04, 0.06, 0.08, 0.10, and 0.12 mg/kg. Midazolam was injected i.m. with atropine 0.01 mg/kg 15 min before the induction of anesthesia. Blood pressure (BP), heart rate, respiratory rate, oxygen saturation (SpO2), sedation level, tongue root depression, eyelash reflex, and anterograde amnesia were monitored. There were no significant differences between male and female patients in any variables in any age. Decrease of SpO2 and loss of eyelash reflex were seen with midazolam 0.10 mg/kg in Group A, and with 0.08 mg/kg in Group B. In Group C, decreases in BP and SpO2, loss of eyelash reflex, and depression of the tongue root were observed with midazolam 0.06 mg/kg. In conclusion, the optimal doses of i.m. midazolam administered 15 min before the induction of anesthesia in male or female patients were 0.08, 0.06, and 0.04 mg/kg for Groups A, B, and C, respectively. ⋯ Midazolam is the most widely used preoperative anxiolytic drug. Our purpose was to evaluate the optimal dose of i.m. midazolam that would maximize the desired effects and minimize the side effects in a common clinical setting. Results indicate that age, but not gender, should affect the i.m. midazolam dose selected for premedication.