Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2006
Randomized Controlled TrialIs depth of anesthesia, as assessed by the Bispectral Index, related to postoperative cognitive dysfunction and recovery?
We randomized 74 patients to either a lower Bispectral Index (BIS) regimen (median BIS, 38.9) or a higher BIS regimen (mean BIS, 50.7) during the surgical procedure. Preoperatively and 4-6 wk after surgery, the patients' cognitive status was assessed with a cognitive test battery consisting of processing speed index, working memory index, and verbal memory index. ⋯ No difference was observed in the other two test battery components. Somewhat deeper levels of anesthesia were therefore associated with better cognitive function 4-6 wk postoperatively, particularly with respect to the ability to process information.
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Anesthesia and analgesia · Sep 2006
Clinical TrialImaging pain modulation by subanesthetic S-(+)-ketamine.
Little is known about the effects of low-dose S-(+)-ketamine on the cerebral processing of pain. We investigated the effects of subanesthetic IV S-(+)-ketamine doses on the perception of experimental painful heat stimuli. Healthy volunteers were evaluated with functional magnetic resonance imaging (fMRI) while receiving the painful stimuli in conjunction with placebo and increasing doses (0.05, 0.1, 0.15 mg x kg(-1) x h(-1)) of ketamine infusion. ⋯ During placebo administration, a typical pain activation network (thalamus, insula, cingulate, and prefrontal cortex) was found, whereas decreased pain perception with ketamine was associated with a dose-dependent reduction of pain-induced cerebral activations. Analysis of the dose-dependent ketamine effects on pain processing showed a decreasing activation of the secondary somatosensory cortex (S2), insula and anterior cingulate cortex. This part of the anterior cingulate cortex (midcingulate cortex) has been linked with the affective pain component that underlines the potency of ketamine in modulating affective pain processing.
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Anesthesia and analgesia · Sep 2006
Change in expiratory flow detects partial endotracheal tube obstruction in pressure-controlled ventilation.
Only extreme degrees of endotracheal tube (ETT) narrowing can be detected with monitoring of tidal volume (V(T)) during pressure-controlled ventilation (PCV). To assess the degree of ETT obstruction in PCV and to compare it to V(T) monitoring, we produced 3 levels of partial ETT obstruction in 11 healthy anesthetized piglets using ETTs of 4 different inner diameters (IDs 9.0, 8.0, 7.0, and 6.0 mm). An expiratory flow over volume ((e)-V) curve was plotted and the time constant (tau(e)) at 15% of expiration time (T(e)) was calculated. ⋯ V(T) monitoring failed to detect ETT narrowing. By contrast, V(ex fract,15) decreased and tau(e) increased significantly with increasing ETT narrowing (for IDs 9.0, 8.0, 7.0, and 6.0, mean V(ex fract,15) was 195, 180, 146, and 134 mL respectively and mean tau(e) was 380, 491, 635, 794 ms for IDs 9.0, 8.0, 7.0, and 6.0 respectively). We conclude that when the elastic recoil that drives (e) is appropriately considered, analysis of (e) and V(ex fract,15) detects partial ETT obstruction during PCV.
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Anesthesia and analgesia · Sep 2006
Transcutaneous blood gas CO2 monitoring of induced ventilatory depression in mice.
We assessed a simple, noninvasive method of monitoring transcutaneous partial pressure of CO2 (Ptcco2) in mice to determine whether it would provide an accurate and reproducible method to assess ventilatory depression in mice. To this end, Ptcco2 and Paco2 (partial pressure of arterial CO2) measurements were performed on isoflurane-anesthetized male C57Bl/6 mice breathing differing percentages of CO2 or fentanyl, a known ventilatory depressive drug. All doses of fentanyl produced a sharp increase in Ptcco2 values within 20 min with difference in Ptcco2 values between saline and all fentanyl groups being statistically significant (P < 0.0001). ⋯ A Bland-Altman analysis likewise found that Ptcco2 measurements in the mice reliably and accurately reflected their Paco2 values. Therefore, under controlled conditions, Ptcco2 measurements were found to reliably reflect Paco2 values in mice. Consequently, the Ptcco2 method can be used as a means to rapidly and quantitatively assess the ventilatory depressive properties of a wide spectrum of drugs, under varying conditions in numerous mouse models.
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Anesthesia and analgesia · Sep 2006
Intermittent lumbar puncture in rats: a novel method for the experimental study of opioid tolerance.
Spinal subarachnoid opioid administration in rats has been a very important method for studying the pharmacological effects of opioids, including analgesia and tolerance. Intrathecal catheterization, either through the cervical or lumbar approach, has been the predominant method used to deliver opioids spinally. However, these methods have potential undesirable complications. ⋯ This method avoids catheter-associated morbidity. We demonstrate that this method can be readily used to induce spinal opioid tolerance without causing morbidity. Intermittent lumbar puncture should prove to be a useful technique for investigating mechanisms of spinal opioid analgesia and opioid tolerance development.