Acute smoking increases ST depression in humans during general anesthesia.

UNLABELLED: We tested the hypothesis that acute smoking is associated with ST segment depression during general anesthesia in patients without ischemic heart disease. The carbon monoxide (CO) concentration in expired gas and hemodynamic data was measured during general anesthesia for noncardiac or nonperipheral vascular surgery in patients without symptoms or evidence of ischemic heart disease. Increased expired CO concentrations are indicators of recent smoking. Logistic regression analysis identified significant predictors of ST segment depression > or = 1 mm. Both rate pressure product (odds ratio 1.20 for each increase of 1000, 95% confidence interval = 1.04-1.41, P = 0.007) and expired CO concentration (odds ratio 1.05 for each part per million increase, 95% confidence interval = 1.03-1.08, P = 0.001) were significant predictors of ST segment depression when considered simultaneously. Males demonstrated a lower probability of having an episode of ST depression (odds ratio = 0.16, P = 0.01), but this did not change the relationship between rate pressure product and CO as predictors of ST depression. Approximately 25% of chronically smoking patients smoked on the morning of surgery despite instructions not to smoke. IMPLICATIONS: Patients under age 65 without symptoms of ischemic heart disease who smoked shortly before surgery had more episodes of rate pressure product-related ST segment depression than nonsmokers, prior smokers, or chronic smokers who did not smoke before surgery. Females were at greater risk of ST depression than males.

A method to evaluate upper airway mechanics following intervention in snorers.

PURPOSE: To describe a method that measures multisegment upper airway changes following intervention for snoring and obstructive apnea that controls for physiological fluctuations during sleep. PATIENTS AND METHODS: Retropalatal, retroglossal, and retrohyoid airway segments were evaluated before and after application of an oral appliance (OA) in four snoring subjects. Twelve airway segments were evaluated. Physiological fluctuations during sleep were controlled with variably applied nasal continuous positive pressure (CPAP), benzodiazepam-induced sleep, and obtaining measures at zero flow on the first test breath. Airway area was measured endoscopically. RESULTS: The methodology identified that following intervention with an OA, maximum retroglossal airway size increased 23.3% +/- 7.5% (P < .05) and retrohyoid size decreased -63.5% +/- 16.0% (P < .05). No changes in retropalatal area (-2.5% +/- 3.0%) or closing pressure were observed. The level of primary obstruction shifted inferiorly in one patient. Airway measures prior to intervention showed small alterations of applied pressure (1 cm H2O) changed retropalatal and retroglossal area an average of 10% +/- 0.9%/cm H2O. CONCLUSION: The mechanical effects of limited airway intervention can be measured with a hypotonic, pressure-controlled methodology. At small airway areas, the airway is highly collapsible and airway size fluctuates. Small changes in applied or physiological forces may alter the airway as significantly as the effects of the intervention being evaluated. The hypotonic upper airway method provides a method to control airway collapse and evaluate interventions, such as OA or surgery, for snoring and obstructive sleep apnea syndrome.

Opioid sedation does not alter intracranial pressure in head injured patients.

PURPOSE: This study aimed to examine the effects of sedative doses of morphine, fentanyl and sufentanil on intracranial pressure (ICP) in head-injured patients in whom changes in mean arterial pressure (MAP) were minimized. METHODS: Fifteen severely head-injured patients (GSC of < or = 8) were randomly assigned to receive either fentanyl, sufentanil or morphine, titrating the drug to a maximal 10% decrease in MAP. The patients were subsequently given an infusion of the same opioid. For four hours, ICP, MAP and heart rate were recorded. RESULTS: In all groups, there were no increases in ICP. There was a decrease in MAP in the sufentanil group at 10 min (P < 0.05) and 45 min after the initial opioid bolus. These decreases in MAP were not associated with increases in ICP. CONCLUSION: The study suggests that when opioids are titrated in head-injured patients, worsening intracranial pressure can be avoided.

Reduction in the incidence of carbon monoxide exposures in humans undergoing general anesthesia.

BACKGROUND: Carbon monoxide forms via reaction of isoflurane, enflurane, and desflurane with dried CO2 absorbents. The authors hypothesize that interventions by nonphysician support personnel to decrease absorbent drying will decrease the exposure rate of patients to carbon monoxide from anesthetic breakdown. METHODS: In the control group, all anesthetizing personnel were made aware of the factors enabling CO generation from anesthetic breakdown, and prevention techniques were left to the anesthetizing personnel. After data collection was complete, the following interventions were initiated to reduce absorbent drying: Anesthesia technicians and housekeeping personnel were instructed to turn off all anesthesia machines after the last case of the day in each room, and the CO2 absorbent was changed each morning if fresh gas was found flowing. Baralyme was used in all phases of this study. RESULTS: Five cases of intraoperative carbon monoxide exposure occurred among 1,085 (0.46%) first cases in the control group. Postintervention, patient carbon monoxide exposures decreased (P < 0.05), with one exposure among 1,961 (0.051%) first cases in the main operating room. Two exposures among 68 (2.9%) first cases occurred in remote locations (P < 0.001) versus main operating room. Predisposing factors for absorbent drying include the prolonged use of anesthesia machines for monitored anesthesia care, inappropriate drying techniques for expiratory flowmeters, understaffing of support personnel, and anesthesia in remote locations. CONCLUSIONS: These interventions reduced patient exposure to carbon monoxide. Monitoring for carbon monoxide exposures during general anesthesia may be necessary to recognize and end patient exposures that occur despite preventative measures.

Twelve hour anaesthesia in a patient with epidermolysis bullosa.

Epidermolysis bullosa (EB), an inherited disorder presents clinically with recurrent cutaneous blister formation with possible involvement of mucous membranes and other organs. The sequelae of this disease pose multiple challenges to the anaesthetist and operating room team. Recent literature describes several anaesthetic techniques for the short surgical procedures this patient population may undergo. We describe the anaesthetic technique employed in a 28-yr-old women with recessive dystrophic epidermolysis bullosa who underwent 12 hr reconstructive surgery followed by a review of the literature that includes a recent description of the possible association of EB with at least two distinct neuromuscular diseases. A detailed description of airway and skin management is described in addition to preoperative concerns. We conclude that a prolonged operative procedure can be undertaken successfully in this population with minimal sequelae involving skin integrity and airway management.

Anesthetic management of obstructive sleep apnea patients.

Presented in an illustrative case report and a review of the anesthetic management of obstructive sleep apnea patients. Preoperative evaluation should include a thorough airway evaluation and a comprehensive cardiovascular and pulmonary evaluation. With polysomnography, identification of the severity of sleep apnea can be idenified. Although sleep centers vary in their definitions, severe obstructive sleep apnea is diagnosed if the patient demonstrates an apnea index greater than 70 and an oxygen (O2) desaturation less than 80% with cardiovascular sequelae. Severe sleep apnea patients are at extreme risk for general anesthesia. These risks should be discussed preoperatively with the patient. Unsupervised preoperative sedation should be avoided because of the extreme sensitivity of these patients to sedatives and airway obstruction. Intraoperative management of the obstructive sleep apnea patient varies depending on the severity of the sleep apnea. Invasive monitoring may be necessary if the patient demonstrates evidence of cardiopulmonary dysfunction. With the assistance of the otolaryngologist, the anesthesiologist can formulate an approach to establishing an airway. Intraoperative opioids and sedatives should be limited. The recovery of the sleep apnea patient is extremely important and is the time when most airway emergencies occur. Extubation of the patient should occur when appropriate surgical personnel and equipment are available in case of an airway emergency. Steroids may be used to decrease the amount of airway swelling. Supplemental O2 should be used in patients who demonstrate desaturation. Opioids and sedatives should be avoided, as should other drugs that have central and sedating effects. Postoperative pain is effectively controlled with acetaminophen and topical anesthetic sprays. Postoperative monitoring for apnea, desaturation, and dysrhythmias is a necessity in sleep apnea patients.