Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1999
ReviewHypothesis: volatile anesthetics produce immobility by acting on two sites approximately five carbon atoms apart.
All series of volatile and gaseous compounds contain members that can produce anesthesia, as defined by the minimum alveolar anesthetic concentration (MAC) required to produce immobility in response to a noxious stimulus. For unhalogenated n-alkanes, cycloalkanes, aromatic compounds, and n-alkanols, potency (1 MAC) increases by two-to threefold with each carbon addition in the series (e.g., ethanol is twice as potent as methanol). Total fluorination (perfluorination) of n-alkanes essentially eliminates anesthetic potency: only CF4 is anesthetic (MAC = 66.5 atm), which indicates that fluorine atoms do not directly influence sites of anesthetic action. Fluorine may enhance the anesthetic action of other moieties, such as the hydrogen atom in CHF3 (MAC = 1.60 atm), but, consistent with the notion that the fluorine atoms do not directly influence sites of anesthetic action, adding -(CF2)n moieties does not further increase potency (e.g., CHF2-CF3 MAC = 1.51 atm). Similarly, adding -(CF2)n moieties to perfluorinated alkanols (CH2OH-[CF2]nF) does not increase potency. However, adding a second terminal hydrogen atom (e.g., CHF2-CHF2 or CH2OH-CHF2) produces series in which the addition of each -CF2- "spacer" in the middle of the molecule increases potency two- to threefold, as in each unhalogenated series. This parallel stops at four or five carbon atom chain lengths. Further increases in chain length (i.e., to CHF2[CF2]4CHF2 or CHF2[CF2]5CH2OH) decrease or abolish potency (i.e., a discontinuity arises). This leads to our hypothesis that the anesthetic moieties (-CHF2 and -CH2OH) interact with two distinct, spatially separate, sites. Both sites must be influenced concurrently to produce a maximal anesthetic (immobility) effect. We propose that the maximal potency (i.e., for CHF2[CF2]2CHF2 and CHF2[CF2]3CH2OH) results when the spacing between the anesthetic moieties most closely matches the distance between the two sites of action. This reasoning suggests that a distance equivalent to a four or five carbon atom chain, approximately 5 A, separates the two sites. ⋯ Volatile anesthetics may produce immobility by a concurrent action on two sites five carbon atom lengths apart.
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Anesthesia and analgesia · Jun 1999
Patients with malignant osteopetrosis are at high risk of anesthetic morbidity and mortality.
The anesthetic literature contains no focused discussion of the perioperative management and risks of children with malignant autosomal recessive osteopetrosis (osteopetrosis). We retrospectively analyzed the perioperative morbidity and mortality rates encountered in the anesthetic management of children with osteopetrosis. We compared the perioperative mortality rate for this patient population with that for other pediatric patients in our institution and that reported in the literature for children and other high-risk patients. We also investigated the inability to intubate the tracheas of children with osteopetrosis compared with other pediatric patients in our institution. Using Fisher's exact test, patients with osteopetrosis were found to have a higher likelihood of perioperative mortality compared with other children or all ASA physical status III, but not ASA physical status IV, patients (P < 0.05). Finally, we discovered that children with osteopetrosis were more likely to have tracheas that could not be intubated than other pediatric patients in our institution. We conclude that children with osteopetrosis are at risk of adverse respiratory events and mortality associated with these adverse events. ⋯ Osteopetrosis is a rare disease that increases perioperative morbidity and mortality. By performing a retrospective chart review, we found that this increased perioperative morbidity and mortality is primarily related to airway and respiratory factors. Anesthetic management strategies should consider the factors that cause the high frequency of adverse airway events in this patient population.
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Anesthesia and analgesia · Jun 1999
Randomized Controlled Trial Comparative Study Clinical TrialGranisetron/dexamethasone combination for reducing nausea and vomiting during and after spinal anesthesia for cesarean section.
We compared the efficacy of granisetron plus dexamethasone with that of granisetron alone for preventing nausea and vomiting in parturients undergoing cesarean section under spinal anesthesia. In a randomized, double-blinded manner, 120 patients received either granisetron 3 mg (Group I, n = 60) or granisetron 3 mg plus dexamethasone 8 mg (Group II, n = 60) IV immediately after clamping of the fetal umbilical cord. A complete response, defined as no emetic symptoms and no need for another rescue antiemetic medication in the intraoperative, postdelivery period was 83% in Group I and 98% in Group II (P = 0.008); the corresponding rates during the first 24 h after surgery was 85% and 98% (P = 0.016). No clinically serious adverse events were observed in any of the groups. In conclusion, the prophylactic use of a granisetron/dexamethasone combination is more effective than granisetron alone for reducing nausea and vomiting in patients during and after spinal anesthesia for cesarean section. ⋯ Intraoperative, postdelivery, and postoperative nausea and vomiting are distressing to patients undergoing cesarean section under spinal anesthesia. The combination of granisetron plus dexamethasone was evaluated and found to be effective for preventing these emetic symptoms.
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Anesthesia and analgesia · Jun 1999
Randomized Controlled Trial Comparative Study Clinical TrialHemodynamic and catecholamine stress responses to insertion of the Combitube, laryngeal mask airway or tracheal intubation.
In a prospective, randomized, and controlled trial, we compared the stress responses after insertion of the Combitube (CT; Kendall-Sheridan Catheter Corp., Argyle, NY), the laryngeal mask airway (LMA), or endotracheal intubation (ET). Seventy-five patients scheduled for routine urological or gynecological surgery were randomly allocated to one of three groups and were ventilated via either an ET, a LMA, or a CT. All three devices could be inserted easily and rapidly, providing adequate ventilation and oxygenation. Insertion of the CT was associated with a significant increase in mean maximal systolic arterial pressure (160+/-32 mm Hg) and diastolic arterial pressure (91+/-17 mm Hg) compared with ET (140+/-24, 78+/-11 mm Hg; P < 0.05, P < 0.01, respectively) or insertion of the LMA (115+/-33,63+/-22 mm Hg, both P < 0.001). The mean maximal epinephrine and norepinephrine plasma concentrations after insertion of the CT (37.3+/-31.1 and 279+/-139 pg/mL, respectively) were significantly higher than those after ET (35.8+/-89.8 and 195+/-58 pg/mL, respectively) or insertion of a LMA (17.3+/-13.3 and 158+/-67 pg/mL, respectively). This might be attributed to the pressure of the pharyngeal cuff of the CT on the anterior pharyngeal wall. We conclude that insertion of the CT causes a pronounced stress response and that precautions should be taken when used in patients at risk of hypertensive bleeding. ⋯ In this study, we showed that the hemodynamic and catecholamine stress responses after insertion of the Combitube (Kendall-Sheridan Catheter Corp., Argyle, NY) were significantly higher compared with laryngeal mask airway or endotracheal intubation. We conclude that the increased stress response to insertion of a Combitube may represent a serious hazard to patients with cardiovascular disease.
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Anesthesia and analgesia · Jun 1999
Clinical TrialD-Dimer formation during cardiac and noncardiac thoracic surgery.
The ability to make therapeutic decisions regarding excessive fibrinolysis in the perioperative period is limited by the lack of availability of a near site monitor of fibrinolysis. We investigated the use of a latex agglutination D-dimer assay to detect perioperative fibrinolysis in patients undergoing thoracic surgery with and without extracorporeal circulation. We studied 27 patients who underwent thoracic surgery requiring cardiopulmonary bypass (CPB; coronary artery bypass grafting, n = 12; valvular surgery, n = 15) and a cohort of 20 patients who underwent noncardiac thoracic surgical procedures not requiring CPB. The purpose of this investigation was to determine the relationship among alterations in the latex agglutination D-dimer assay, use of extracorporeal circulation, type of cardiac surgical procedure, and mediastinal and/or chest tube drainage (cardiac surgery only) in patients undergoing thoracic surgery. Perioperative D-dimer levels, measured by latex agglutination, had significant (P < or = 0.05) intragroup changes among patients undergoing cardiac surgery (requiring CPB) and the cohort of patients who underwent noncardiac thoracic surgery without CPB. Although intraoperative D-dimer levels were not increased in patients undergoing noncardiac thoracic surgery, postoperative levels were significantly (P < 0.05) increased (compared with preinduction). In cardiac surgery patients requiring CPB, intraoperative D-dimer formation was significantly (P < or = 0.05) increased but did not demonstrate any intragroup (coronary artery bypass grafting versus valvular surgery) differences. Finally, D-dimer levels were not associated with postoperative mediastinal and/or chest tube accumulative drainage measured at intervals up to 48 h postoperatively in patients undergoing cardiac surgery requiring CPB. Our study indicates that the latex agglutination D-dimer assay can detect excessive fibrinolysis perioperatively, and that extracorporeal circulation can significantly influence the pattern of D-dimer formation in patients undergoing thoracic surgery. ⋯ We assessed the ability of a readily available D-dimer assay to detect excessive fibrinolysis in patients undergoing thoracic surgery with and without extracorporeal circulation. The findings demonstrate that the assay used in this investigation reflected variable amounts of fibrinolysis in patients undergoing both types of thoracic surgery.