Journal of clinical anesthesia
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One of the sources of error in pulse oximetry readings is associated with an abnormal signal-to-noise ratio. The pulse oximeter distinguishes the light absorbance of arterial blood from that of other absorbers by differentiating between a constant component and a pulsating component. The pulsating component is almost exclusively the result of arteriolar bed pulsations. ⋯ We report a case in which a low pulse oximetry reading was associated with concomitant use of a pulse oximeter and a peripheral nerve stimulator on the same arm. Further tests conducted using a nerve stimulator and a sensory evoked potential stimulator with different amplitudes and frequencies confirmed the association and delineated the relationship between frequency and amplitude of stimulation and the degree of artificial desaturation. A theoretical explanation for this phenomenon is presented.
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To examine contemporary practices and opinions regarding preoperative testing requirements, with special emphasis on perioperative pregnancy recognition and consequences thereof. ⋯ The desire to identify pregnancy using patient history was most prevalent among anesthesiologists, with less than one third using mandatory, departmentally imposed screening programs. Positive test results in minors are shared primarily with surgeons and patients, occasionally with parents and social services, but rarely with police, although a positive test almost universally signified child abuse, and mandatory reporting laws were acknowledged by anesthesiologists surveyed.
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In conclusion, providing anesthesia for a small child undergoing craniofacial reconstructive surgery is an enormous challenge. Even with the most experienced pediatric anesthesiologist and pediatric surgeons, problems can develop suddenly and lead, as they did in this case, to serious morbidity and even death. It is difficult to determine whether the anesthesiologists' "success" in this case in warding off a malpractice verdict was due to their lawyer's ability to convince the court they delivered a level of "care ordinarily supplied by physicians in their specialty," or, rather, due to the fact that defense experts were more convincing than those of the plaintiffs. Regardless, I do not think there were any "winners" in this situation.
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The pharmacokinetic and pharmacodynamic interactions between opioids and propofol increasingly have been described and used in clinical practice. It is now known that propofol inhibits both alfentanil and sufentanil metabolism, thereby increasing the plasma concentrations of these opioids, while alfentanil also elevates propofol concentrations. ⋯ From the interaction data, the optimal propofol concentrations have been extracted that assure adequate anesthesia and the most rapid recovery possible. In the presence of fentanyl, sufentanil, and alfentanil, the optimal propofol concentration is approximately 3.5 microgram/ml, whereas in the presence of remifentanil, lower propofol concentrations of 2.5 to 3 microgram/ml are required.