Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2004
Clinical TrialChronic treatment with antipsychotics enhances intraoperative core hypothermia.
Antipsychotics can induce hypothermia, but intraoperative temperature regulation in schizophrenic patients taking antipsychotics remains unclear. We investigated intraoperative temperature regulation and postoperative shivering in chronic schizophrenic patients receiving antipsychotics. We studied 30 schizophrenic patients and 30 control patients who underwent orthopedic surgery. Tympanic membrane temperatures (35.7 degrees C +/- 0.5 degrees C, 35.6 degrees C +/- 0.5 degrees C, 35.6 degrees C +/- 0.4 degrees C, 35.5 degrees C +/- 0.4 degrees C, 35.4 degrees C +/- 0.5 degrees C, and 35.4 degrees C +/- 0.3 degrees C) 15, 30, 45, 60, 75, and 90 min, respectively, after induction in schizophrenic patients were significantly (P < 0.001) lower than those (36.5 degrees C +/- 0.5 degrees C, 36.4 degrees C +/- 0.5 degrees C, 36.3 degrees C +/- 0.4 degrees C, 36.2 degrees C +/- 0.5 degrees C, 36.2 degrees C +/- 0.4 degrees C, and 36.1 degrees C +/- 0.4 degrees C) in control patients. Mean skin temperatures (31.1 degrees C +/- 0.4 degrees C [P = 0.008], 31.1 degrees C +/- 0.3 degrees C [P = 0.007], and 31.1 degrees C +/- 0.2 degrees C [P = 0.006]) 60, 75, and 90 min, respectively, after induction in schizophrenic patients were significantly lower than those (31.5 degrees C +/- 0.3 degrees C, 31.5 degrees C +/- 0.3 degrees C, and 31.5 degrees C +/- 0.3 degrees C) in control patients. Four of 30 schizophrenic patients and 7 of 30 control patients developed postanesthesia shivering. There were no significant differences within 1 h after tracheal extubation in tympanic membrane temperatures between patients who shivered and those who did not shiver. In conclusion, chronic schizophrenic patients were more hypothermic during anesthesia. The incidence of postanesthesia shivering was not significantly increased. ⋯ Antipsychotics inhibit autonomic thermoregulation. This is caused by decreased heat production, increased heat loss, and impaired central action at the hypothalamus. Thus, schizophrenic patients receiving antipsychotics may have impaired intraoperative temperature regulation.
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Anesthesia and analgesia · Jan 2004
Clinical TrialQuantitative and selective evaluation of differential sensory nerve block after transdermal lidocaine.
We evaluated the effect of transdermal lidocaine on differential sensory nerve block in 15 healthy volunteers. Lidocaine 10% gel was applied topically to a forearm and covered with a plastic film. Three types of sensory nerve fibers (Abeta, Adelta, and C fibers) were evaluated with a series of 2000-, 250-, and 5-Hz stimuli using current perception threshold (CPT) testing. Sensations of touch, pinprick, cold, and warmth were also measured. These measurements were made before the topical lidocaine (baseline), 60 min after the draping (T0), and at 1-h intervals until 5 h after T0 (T1 to T5). A significant increase in CPT compared with baseline was observed until T2 at 5 Hz and T4 at 250 Hz, whereas the increase in CPT at 2000 Hz continued throughout the study period. All subjects experienced the disappearance of pinprick and cold sensations, whereas touch and warmth sensations were detectable during the study period. We conclude that when lidocaine is applied transdermally, the sensitivity of nerves to local anesthetics is proportional to the axon diameters. However, pinprick and cold sensation are affected more strongly than other sensations at receptor sites. ⋯ We evaluated the effect of transdermal lidocaine on differential sensory nerve block in healthy volunteers. Our results show that the sensitivity of nerves to local anesthetics is proportional to the axon diameter.
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Anesthesia and analgesia · Jan 2004
Comparative StudySpinal chloroprocaine solutions: density at 37 degrees C and pH titration.
The density and pH of a local anesthetic are important characteristics in its use as an intrathecal drug. Preservative- and antioxidant-free formulations of chloroprocaine are available and are being investigated for short-duration spinal anesthesia. In this study, we evaluated the pH and density (to 5 significant digits in g/mL, at 37.0 degrees C) of these new chloroprocaine formulations. In addition to plain 2% and 3% chloroprocaine and 2% lidocaine, mixed solutions of 2% chloroprocaine with epinephrine or with bicarbonate were evaluated. Density was also measured after water dilution and after increasing amounts of added dextrose. Chloroprocaine, 2% or 3%, is hyperbaric relative to cerebrospinal fluid (CSF) before any addition of dextrose (density 1.00123 g/mL and 1.00257 g/mL, respectively). When diluted with water, all the solutions are hypobaric relative to CSF (density <1.00028 g/mL). Plain 2% lidocaine is the only dextrose-free solution measured to be hypobaric (density 1.00004 g/mL). Bisulfite-free 2-chloroprocaine remains very acidic (pH <4.0), but the pH can be increased to more than 7.0 with a small amount of bicarbonate (0.25-0.33 mL/10 mL). The increased density of plain chloroprocaine makes it a useful hyperbaric spinal drug without the addition of dextrose. ⋯ Dextrose-free 2-chloroprocaine is hyperbaric relative to cerebrospinal fluid at 37 degrees C, and therefore can be used for spinal anesthesia without dextrose. Bisulfite-free 2-chloroprocaine remains very acidic (pH <4.0). The pH can be increased to more than 7.0 with a small amount of bicarbonate (0.25-0.33 mL/10 mL).
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Anesthesia and analgesia · Jan 2004
Clinical TrialCorrelation of bispectral index and Guedel's stages of ether anesthesia.
Bispectral index (BIS) analysis is a method of electroencephalograph (EEG) analysis based on the interfrequency phase relationships of the EEG, designed to quantify anesthetic hypnosis. The BIS was created after concurrent collection of EEG and clinical data from a large number of patients anesthetized with various drugs over a prolonged period and then performing a Fourier analysis followed by a bispectral calculation. The clinical stages of anesthetic depth are very well demonstrated in etherized patients. In this study, we studied the BIS changes during various stages of ether anesthesia and quantified the hypnotic depth during the surgical stage of ether anesthesia. The values for BIS under various stages and planes of ether anesthesia were recorded in 21 patients listed for short surgical procedures. During diethyl ether anesthesia, BIS initially increased and subsequently decreased. During surgical anesthesia, a BIS value of 30 was observed. ⋯ For the first time, bispectral index (BIS) has been studied in patients being anesthetized solely with ether. Ether both causes an increase and decrease in BIS during induction and emergence. The index observed during the surgical stage of ether anesthesia is probably the correct value for the depth of hypnosis because no other volatile anesthetic can produce the true anesthetic state when used alone. This value could be taken as the value to be attained when balanced anesthesia is being practiced.
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Anesthesia and analgesia · Jan 2004
Risperidone and exaggerated hypotension during a spinal anesthetic.
Antipsychotic medications are often continued through pregnancy and may have important anesthetic interactions. For example, risperidone is an antipsychotic medication with therapeutic effects mediated by dopaminergic and serotonergic antagonism. However, it also possesses potent alpha-1 adrenergic antagonism. Here we report a case of a parturient with bipolar disease, controlled with lithium and risperidone, undergoing a spinal anesthetic for a cesarean delivery. The parturient developed exaggerated hypotension, refractory to conventional treatment with ephedrine and IV fluids, that eventually responded to large doses of phenylephrine. Risperidone alpha-antagonism should be a consideration for any patient receiving this medication during neuraxial anesthesia. Treatment of significant and refractory hypotension with an alpha-1 agonist such as phenylephrine may be warranted. ⋯ Parturients receiving neuraxial blocks may be taking antipsychotic medications. Although the therapeutic effects of antipsychotic medications are mediated by dopaminergic and serotonergic antagonism, many possess alpha-adrenergic antagonist properties. We report a case of exaggerated hypotension during a spinal anesthetic for cesarean delivery that may have been a result of the alpha-adrenergic antagonism of risperidone.