Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1999
Nitrous oxide increases normocapnic cerebral blood flow velocity but does not affect the dynamic cerebrovascular response to step changes in end-tidal P(CO2) in humans.
We sought to clarify the effect of nitrous oxide (N2O) on the immediate responses of cerebral vasculature to sudden changes in arterial carbon dioxide tension in healthy humans. By use of a transcranial Doppler ultrasonography, blood flow velocity in the middle cerebral artery (V(MCA)) was measured during a step increase followed by a step decrease in end-tidal CO2 tension (PET(CO2)) between normo- and hypercapnia while subjects inspired gas mixtures containing 70%O2 + 30% N2 (control) and 70% O2 + 30% N2O (N2O) separately. During the control condition, both step increase and decrease in PET(CO2) produced rapid exponential changes in V(MCA). An increase in V(MCA) produced by the step increase in PET(CO2) was smaller (P < 0.001) and slower (P < 0.001) than a decrease in V(MCA) induced by the step decrease in PET(CO2). These general features of the dynamic cerebrovascular response were not affected by substitution of N2O for N2 in the inspired gases although N2O increased baseline V(MCA) by 15% (P < 0.001) compared with the control condition. We conclude that N2(O) in itself does not affect the dynamic cerebrovascular response to arterial CO2 changes, although it produces static mild cerebral vasodilation. ⋯ This study suggests that nitrous oxide does not affect the dynamic cerebrovascular reactivity to acute arterial carbon dioxide (CO2) changes, i.e., exponential changes in cerebral blood flow in response to step changes in alveolar CO2 tension, although it does produce a mild increase in normocapnic cerebral blood flow velocity.
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Anesthesia and analgesia · Sep 1999
Which clinical anesthesia outcomes are important to avoid? The perspective of patients.
Healthcare quality can be improved by eliciting patient preferences and customizing care to meet the needs of the patient. The goal of this study was to quantify patients' preferences for postoperative anesthesia outcomes. One hundred one patients in the preoperative clinic completed a written survey. Patients were asked to rank (order) 10 possible postoperative outcomes from their most undesirable to their least undesirable outcome. Each outcome was described in simple language. Patients were also asked to distribute $100 among the 10 outcomes, proportionally more money being allocated to the more undesirable outcomes. The dollar allocations were used to determine the relative value of each outcome. Rankings and relative value scores correlated closely (r2 = 0.69). Patients rated from most undesirable to least undesirable (in order): vomiting, gagging on the tracheal tube, incisional pain, nausea, recall without pain, residual weakness, shivering, sore throat, and somnolence (F-test < 0.01). ⋯ Although there is variability in how patients rated postoperative outcomes, avoiding nausea/vomiting, incisional pain, and gagging on the endotracheal tube was a high priority for most patients. Whether clinicians can improve the quality of anesthesia by designing anesthesia regimens that most closely meet each individual patient's preferences for clinical outcomes deserves further study.