Anesthesia and analgesia
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Anesthesia and analgesia · May 2001
Comparative StudyThe detection of interatrial flow patency in awake and anesthetized patients: a comparative study using transnasal transesophageal echocardiography.
The Valsalva maneuver in the awake patient and the ventilation maneuver in the tracheally intubated anesthetized patient are two provocation methods to detect a patent foramen ovale (PFO) by means of contrast transesophageal echocardiography. In 60 patients undergoing posterior fossa surgery, a contrast agent was administered via a peripheral vein during a Valsalva maneuver immediately before anesthesia induction, followed by central venous administration during a ventilation maneuver in the same patients when anesthetized and endotracheally intubated. We evaluated both maneuvers with a 32-element monoplane transnasal transesophageal echocardiography probe to trace the atrial flow of the contrast agent in a 90 degrees bicaval view. A maneuver was rated positive when more than four bubbles appeared in the left atrium during the first three cardiac cycles after intrathoracic pressure release. The right atrial cross-sectional area before pressure release, and the peak septal excursion during atrial contrast opacification, were measured. McNemar's test was used to assess a paired dichotomous response on the two maneuvers for a significant difference. In 56 patients, the ventilation maneuver was significantly (P < 0.037) more often positive for PFO (n = 14) than the Valsalva maneuver (n = 7). Although there was no difference in the methods regarding the peak septal excursion, the mean right atrial area before pressure release was significantly smaller during the ventilation maneuver than during the Valsalva maneuver (11.2 +/- 3.1 cm(2) vs 14.4 +/- 3.3 cm(2), n = 42, P < 0.05). In the patients with a positive ventilation, but a negative Valsalva maneuver, the discrepancy was even larger (10.9 +/- 4.4 cm(2) vs 16.3 +/- 4.2 cm(2), n = 7, P < 0.001). We conclude that the ventilation maneuver is superior to the Valsalva maneuver in detecting PFO. Our data suggest that a peak pressure of 30 cm H(2)O during the ventilation maneuver achieves a more pronounced reduction in right atrial load and allows right atrial pressure to exceed left atrial pressure when intrathoracic pressure is released. ⋯ A controlled ventilation maneuver in anesthetized patients immediately before posterior fossa surgery may be superior to the preoperative Valsalva maneuver in detecting a patent foramen ovale by contrast transesophageal echocardiography. This approach identifies patients at high risk for paradoxic embolism, but it is not practical for preoperative identification of patients who might benefit from patent foramen ovale closure before surgery.
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Anesthesia and analgesia · May 2001
Prolonged sedation with propofol in the rat does not result in sleep deprivation.
The use of propofol provides sedation without prolonging emergence in patients in the Intensive Care Unit. When prolonged, however, continuous sedation may overlap with naturally occurring sleep periods and potentially increase the risk of sleep deprivation. We modified an established rat model of sleep to determine whether prolonged, continuous sedation results in sleep deprivation. Rats were continuously sedated for a 12-h period overlapping completely with their normal sleep phase. Electroencephalogram (EEG) and movement data were collected before and after the sedation period. Rats were evaluated for EEG and movement evidence of sleep deprivation after sedation. When compared with baseline, the time spent in rapid eye movement (REM) and non-REM sleep was decreased during the first 4 h after sedation. The duration of non-REM sleep bouts was not altered. Power in the delta band (0.5-4 Hz) during non-REM sleep was diminished during the first 2 h only. Movements were reduced during the first hour after emergence from sedation only. In summary, no EEG or behavioral evidence of sleep deprivation was observed on emergence from sedation. These results imply that sedation is associated with a restorative process reversing the natural accumulation of sleep need that occurs during wakefulness. ⋯ Prolonged sedation in the Intensive Care Unit may alter the restorative effects of naturally occurring sleep. We sedated rats during their sleep phase to determine whether sedation interferes with sleep. Upon emergence, no evidence of sleep deprivation was observed. Sedation may thus be associated with a restorative effect similar to sleep.
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Anesthesia and analgesia · May 2001
Case ReportsArytenoid dislocation while using a McCoy laryngoscope.
Arytenoid dislocation (AD) involves either a complete disruption of the cricoarytenoid joint or a malpositioning of the arytenoid cartilages (AC) with reference to other laryngeal cartilages. In this report, we present a case of AD while using a McCoy laryngoscope. Although McCoy laryngoscope is recognized as a useful option for the cases of difficult endotracheal intubation, we are concerned that AD is likely with this device.
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Anesthesia and analgesia · May 2001
Ultrasonographic findings of the axillary part of the brachial plexus.
In this prospective study we sought to determine anatomic variations of the main brachial plexus nerves in the axilla and upper arm via high-resolution ultrasonography (US) examination. Positions of nerves were studied via US in three sectional levels of the upper arm in 69 healthy volunteers (31 men and 38 women, median age 28 yr). Analysis was done by subdividing the US picture into eight pie-chart sectors and matching sectors for the position of the ulnar, radial, and median nerves. Shortly after the nerves pass the pectoralis minor muscle, they begin to diverge. At the middle level 9%-13%, and at the distal level, 30%-81% of the nerves are not seen together with the artery in the US picture. At the usual level of axillary block approach, we found the ulnar nerve in the posterior medial position in 59% of the volunteers. The other two nerves had two peaks in distribution: the radial nerve in posterior lateral (38%) and anterior lateral (20%) position, and the median nerve in anterior medial (30%) and posterior medial (26%) position. Applying light pressure distally can displace nerves to the side, especially when they are positioned anterior to the axillary artery. We conclude that an axillary block should be attempted as proximal as possible to the axilla. ⋯ This prospective ultrasonography study demonstrates significant anatomic variations of the main brachial plexus nerves in the axilla and upper arm, which may increase the difficulty in identifying neural structures. Applying light pressure on the plexus can move nerves to the side, especially when they are positioned anterior to the axillary artery.
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Anesthesia and analgesia · May 2001
Inhibition of synovial plasma extravasation by preemptive administration of an antiinflammatory irrigation solution in the rat knee.
Inflammation and hyperalgesia during surgical procedures are caused by the local release of multiple inflammatory mediators. We used a rat knee joint model of acute inflammation (synovial plasma extravasation) to determine whether preemptive intraarticular irrigation of the antiinflammatory drugs ketoprofen, amitriptyline, or oxymetazoline, alone or in combination, can reduce inflammatory soup-induced plasma extravasation. These three drugs were selected because of their abilities to collectively inhibit the inflammatory effects of biogenic amines, eicosanoid production, and the release of neuropeptides from C-fiber terminals. Synovial perfusion of each one of the three drugs 10 min before, and then in combination with, the inflammatory soup (bradykinin, 5-hydroxytryptamine, and mustard oil) did not reduce plasma extravasation. Similarly, two-drug combinations did not significantly reduce inflammatory soup-induced plasma extravasation. The combination of all three drugs (amitriptyline, ketoprofen, and oxymetazoline) produced a dramatic inhibition of plasma extravasation and was more effective than any of the two-drug combinations. A comparison between the preemptive (10 min before inflammatory soup perfusion) and postinflammatory administration (10 min after inflammatory soup perfusion) showed that the postinflammatory administration of the three-drug solution lost all ability to inhibit inflammatory soup-induced plasma extravasation. We conclude that acute synovial inflammation, which is induced and maintained by multiple mediators, can be substantially inhibited only by the preemptive administration of a drug combination that targets multiple inflammatory mediators. ⋯ Preemptive, intraarticular irrigation of a combination of multiple antiinflammatory drugs is a novel and potentially effective method for reducing the synovial inflammatory response, such as that during arthroscopy. In this study, a three-drug combination infusion was statistically superior to one- or two-drug infusions in a rat model.