Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1998
Randomized Controlled Trial Clinical TrialEsmolol potentiates reduction of minimum alveolar isoflurane concentration by alfentanil.
Esmolol, a short-acting beta1-receptor antagonist, decreases anesthetic requirements during propofol/N2O/morphine anesthesia. This study was designed to determine whether esmolol affects the volatile anesthetic (isoflurane) required to prevent movement to skin incision in 50% patients (minimum alveolar anesthetic concentration [MAC]) with or without an additional opioid (alfentanil). One hundred consenting adult patients were randomly divided into five treatment groups: isoflurane alone (I), I with continuous large-dose (250 microg x kg(-1) x min(-1)) esmolol (E), I with alfentanil (effect site target of 50 ng/mL) via a continuous computer-controlled infusion (A), A plus continuous small-dose (50 microg x kg(-1) x min(-1)) esmolol (A1), or A plus large-dose esmolol (A2). Anesthesia was induced via a face mask, and steady-state target end-tidal isoflurane concentrations were maintained before incision. The MAC of isoflurane alone was 1.28% +/- 0.13%. Large-dose esmolol did not significantly alter the isoflurane MAC (1.23% +/- 0.14%). Alfentanil alone significantly decreased isoflurane MAC by 25% (0.96% +/-0.09%). Adding small-dose esmolol did not further decrease MAC with alfentanil (0.96% +/- 0.13%). However, large-dose esmolol significantly decreased isoflurane MAC with alfentanil (0.74% +/- 0.09%). Esmolol and alfentanil both significantly reduced the increases in heart rate and mean arterial pressure associated with endotracheal intubation and incision. The mechanism of this effect is unknown. ⋯ Most anesthetic techniques rely on a balance of several highly selective medications. The current results define a new anesthetic-sparing effect when volatile anesthetic, analgesic, and beta-adrenergic blocking drugs are combined.
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Anesthesia and analgesia · Sep 1998
Clinical TrialThe effects of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia.
We investigated the effects of body mass index (BMI) on functional residual capacity (FRC), respiratory mechanics (compliance and resistance), gas exchange, and the inspiratory mechanical work done per liter of ventilation during general anesthesia. We used the esophageal balloon technique, together with rapid airway occlusion during constant inspiratory flow, to partition the mechanics of the respiratory system into its pulmonary and chest wall components. FRC was measured by using the helium dilution technique. We studied 24 consecutive and unselected patients during general anesthesia, before surgical intervention, in the supine position (8 normal subjects with a BMI < or = 25 kg/m2, 8 moderately obese patients with a BMI >25 kg/m2 and <40 kg/m2, and 8 morbidly obese patients with a BMI > or = 40 kg/m2). We found that, with increasing BMI: 1. FRC decreased exponentially (r = 0.86; P < 0.01) 2. the compliance of the total respiratory system and of the lung decreased exponentially (r = 0.86; P < 0.01 and r = 0.81; P < 0.01, respectively), whereas the compliance of the chest wall was only minimally affected (r = 0.45; P < 0.05) 3. the resistance of the total respiratory system and of the lung increased (r = 0.81; P < 0.01 and r = 0.84; P < 0.01, respectively), whereas the chest wall resistance was unaffected (r = 0.06; P = not significant) 4. the oxygenation index (PaO2/PAO2) decreased exponentially (r = 0.81; P < 0.01) and was correlated with FRC (r = 0.62; P < 0.01), whereas PaCO2 was unaffected (r = 0.06; P = not significant) 5. the work of breathing of the total respiratory system increased, mainly due to the lung component (r = 0.88; P < 0.01 and r = 0.81; P < 0.01, respectively). In conclusion, BMI is an important determinant of lung volumes, respiratory mechanics, and oxygenation during general anesthesia with patients in the supine position. ⋯ The aim of this study was to investigate the influence of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia.
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Anesthesia and analgesia · Sep 1998
Clinical TrialThe laryngeal mask airway reliably provides rescue ventilation in cases of unanticipated difficult tracheal intubation along with difficult mask ventilation.
In 1995, our department of anesthesiology established an airway team to assist in treating unanticipated difficult endotracheal intubations and an airway quality improvement (QI) form to document the use of emergency airway techniques in airway crises (laryngeal mask airway [LMA], flexible fiberoptic bronchoscopy, retrograde intubation [RI], transtracheal jet ventilation [TTJV], and cricothyrotomy). Over a 2-yr period, team members and staff anesthesiologists completed airway QI forms to document the smallest peripheral SpO2 during an airway crisis, the number of direct laryngoscopies (DL) performed before using an emergency airway technique, and the emergency airway technique that succeeded in rescue ventilation. Team members agreed to use the LMA as the first emergency airway technique to treat the difficult ventilation/difficult intubation scenario. A SpO2 value < or =90% during mask ventilation defined difficult ventilation. Inability to perform tracheal intubation by DL defined difficult intubation. An increase in the SpO2 value >90% defined rescue ventilation. Review of airway QI forms from October 1, 1995 until October 1, 1997 revealed 25 cases of difficult ventilation/difficult intubation. Before airway rescue, the median SpO2 was 80% (range 50%-90%), and there were four median attempts at DL (range one to nine). The LMA had a success rate of 94% (95% confidence interval [CI] 77-100). Flexible fiberoptic bronchoscopy, TTJV, RI, and surgical cricothyrotomy had success rates of 50% (95% CI 0-100), 33% (95% CI 0-100), 100% (95% CI 37-100), and 100% (95% CI 37-100), respectively. LMA insertion as the first alternative airway technique was useful in dealing with unanticipated instances of simultaneous difficulty with mask ventilation and tracheal intubation. ⋯ Twenty-five cases of simultaneous difficulty with mask ventilation and tracheal intubation occurred after the induction of general anesthesia during the study period. The laryngeal mask was used in 17 cases, and it provided rescue ventilation without complication in 94% of these cases (95% confidence interval 77-100).
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Anesthesia and analgesia · Sep 1998
Randomized Controlled Trial Clinical TrialWidespread application of topical steroids to decrease sore throat, hoarseness, and cough after tracheal intubation.
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Anesthesia and analgesia · Sep 1998
Clinical TrialEffects of cardiopulmonary bypass and deep hypothermic circulatory arrest on the thyroid axis during and after repair of congenital heart defects: preservation by deep hypothermia?
Thyroid function is altered by cardiopulmonary bypass (CPB) in children. To better understand the cause of altered thyroid hormone levels, we compared the effects on the pituitary-thyroid axis of CPB in 23 children undergoing elective repair of congenital heart defects. Twelve patients underwent CPB with moderate hypothermia without a period of deep hypothermic circulatory arrest (DHCA), and eleven underwent CPB with DHCA. Nine blood samples were collected from each patient before, during, and after CPB. Free T3 (FT3), free T4 (FT4), total T3 (TT3), total T4 (TT4), thyrotropin (TSH), and albumin were measured; concentrations of each decreased significantly with the onset of CPB (P < 0.05). There was a greater decline in hormone than in albumin concentrations, which suggests that factors in addition to hemodilution were present (P < 0.05). TSH concentrations in the DHCA group began to increase during cooling, exceeding baseline values after rewarming and after separation from CPB. Patients undergoing CPB without DHCA had persistently low TSH concentrations (P < 0.05). By Postoperative Days 1 and 2, TSH concentrations in both groups were similar and significantly lower than baseline values (P < 0.001). FT3, FT4, TT3, TT4, and albumin all increased during CPB after an initial decrease. Of these, only albumin and FT4 recovered to their baseline values after the initial decrease. Nevertheless, by Postoperative Day 1, both groups demonstrated the "sick" euthyroid syndrome and could not be distinguished from one another. This study demonstrates greater pituitary release of TSH in children undergoing repair of congenital heart defects with DHCA compared with CPB alone, the cause of which could not be determined in this study. However, despite the increase in TSH in the DHCA group, the thyroid hormone concentrations failed to increase appropriately. ⋯ Early after deep hypothermia circulatory arrest, thyrotopin concentrations increase appropriately, responding to decreased concentrations of T3; however, all children undergoing cardiopulmonary bypass eventually develop a "sick" euthyroid syndrome by Postoperative Day 1. Whether this difference represents better protection of neuroendocrine function by deep hypothermic circulatory arrest (relative to cardiopulmonary bypass alone) remains speculative.