Anesthesia and analgesia
-
Anesthesia and analgesia · Aug 1995
Regional anesthesia and local anesthetic-induced systemic toxicity: seizure frequency and accompanying cardiovascular changes.
We sought to determine the contemporary frequency of seizures, and the associated cardiovascular changes, resulting from local anesthetic-induced seizures in all patients undergoing brachial plexus, epidural, and caudal regional anesthetics. We investigated the following variables: development and treatment of seizure or cardiac arrest during the regional anesthetic, type of anesthetic (including local anesthetic used), gender, age, ASA physical status class and type of operation (elective or emergent). In addition, each patient who experienced a seizure underwent retrospective review of the acute event to determine the arterial blood pressure and heart rate changes accompanying the seizure, as well as details of the regional block technique. ⋯ A significant difference was also noted in the rate of seizure development within types of brachial block, with supraclavicular and interscalene > axillary. No adverse cardiovascular, pulmonary or nervous system events were associated with any of the seizures, including the 16 patients who received bupivacaine blocks. The frequency of local anesthetic-induced seizures stratified by block type has a wide range, and cardiovascular collapse after bupivacaine-associated seizure has a low incidence.
-
Anesthesia and analgesia · Aug 1995
Fentanyl, clonidine, and repeated increases in desflurane concentration, but not nitrous oxide or esmolol, block the transient mydriasis caused by rapid increases in desflurane concentration.
Initial, but not subsequent, inhalation of 8% desflurane produces transient sympathetic stimulation. We hypothesized that initial but not subsequent increases should produce pupil dilation, and that N2O, fentanyl, and clonidine, but not esmolol, should blunt the response. In 10 volunteers, we maintained anesthesia with 4% end-tidal desflurane in oxygen for 32 min, then increased the concentration to 8% for 10 min. ⋯ Fentanyl 1.5 micrograms/kg and 4.5 micrograms/kg decreased peak diameter (2.3 +/- 0.9 and 1.6 +/- 0.3 mm), as did clonidine (2.3 +/- 1.7 mm) but not esmolol. We conclude that, concurrent with sympathetic stimulation, an initial rapid increase in desflurane concentration transiently increases pupil diameter, whereas repeated increases produce attenuated responses. N2O augments, fentanyl and clonidine attenuate, and esmolol does not affect the response.
-
Anesthesia and analgesia · Aug 1995
Differential age effects of mean arterial pressure and rewarming on cognitive dysfunction after cardiac surgery.
Central nervous system dysfunction is a common consequence of otherwise uncomplicated cardiac surgery. Many mechanisms have been postulated for the cognitive dysfunction that is part of these neurologic sequelae. The purpose of our investigation was to evaluate the effects of mean arterial pressure (MAP) during cardiopulmonary bypass (CPB) and the rate of rewarming on cognitive decline after cardiac surgery. ⋯ Multivariable linear regression revealed that the rate of rewarming and MAP were unrelated to cognitive decline. However, interactions significantly associated with cognitive decline were found between age and MAP area less than 50 mm Hg on one measure, and between age and rewarming rate in another, identifying susceptibility of the elderly to these factors. Although MAP and rewarming were not the primary determinates of cognitive decline in this surgical population, hypotension and rapid rewarming contributed significantly to cognitive dysfunction in the elderly.
-
Anesthesia and analgesia · Aug 1995
Case ReportsTransient neurologic deficit after spinal anesthesia: local anesthetic maldistribution with pencil point needles?
Recent reports of transient neurologic deficits have raised concern about the potential toxicity of single-dose spinal 5% lidocaine in 7.5% dextrose. Two cases of volunteers who experienced minor local sensory deficits after slow (60 s) injections of 2 mL 5% lidocaine via Whitacre needles are described. One case was a result of a double injection because of a "failed" block. ⋯ Triplicate injections were done at rapid (2 mL/10 s) and slow (2 mL/60 s) rates, with needle side ports oriented in a sacral and cephalad direction. At slow rates of injection, using 27- or 25-gauge sacrally directed Whitacre needles, injections showed evidence of maldistribution with extrapolated peak sacral lidocaine concentrations reaching 2.0%. In contrast, distribution after slow injection through sacrally directed Quincke needles was uniform.(ABSTRACT TRUNCATED AT 250 WORDS)
-
Anesthesia and analgesia · Aug 1995
Exhaled flow monitoring can detect bronchial flap-valve obstruction in a mechanical lung model.
Flap-valve obstruction to expiratory flow (V) in a major bronchus can result from inspissated secretions, blood, or foreign body. During inhalation, increasing airway caliber preserves inspired V past the obstruction; during exhalation, decreasing airway diameter causes airflow obstruction and even frank gas trapping. We reasoned that the resultant sequential, biphasic exhalation of the lungs would be best detected by measuring exhaled V versus time. ⋯ Airway P could not differentiate between bronchial and tracheal flap-valve obstruction because P decreased abruptly in both conditions. The flow-volume loop displayed less distinctive changes than the flow-time plot, in part because the flow-volume loop was data (flow) plotted against its time integral (volume), with loss of temporal data. In this mechanical lung model, we conclude that bronchial flap-valve obstruction was best detected by the flow-time plot, which could measure the sequential emptying of the lungs.