H. Gregg Schuler

Laryngoscopy and tracheal intubation in the head-elevated position in obese patients: a randomized, controlled, equivalence trial.

BACKGROUND:The proper positioning of patients before direct laryngoscopy is a key step that facilitates tracheal intubation. In obese patients, the 25 degree back-up or head-elevated laryngoscopic position, which is better than the supine position for tracheal intubation, is usually achieved by placing blankets or other devices under the patients head and shoulders. This position can also be achieved by reconfiguring the normally flat operating room (OR) table by flexing the table at the trunk-thigh hinge and raising the back (trunk) portion of the table (OR table ramp). This table-ramp method can be used without the added expense of positioning devices, and it reduces the possibility of injury to the patient or providers that can occur during removal of such devices once tracheal intubation is achieved. In this study, we sought to determine if the table-ramp method of patient positioning was equivalent to the blanket method with regard to the time required for tracheal intubation. METHODS:Eighty-five adults with a Body Mass Index >30 kg/m2, scheduled for elective surgery, consented to participate in this prospective randomized equivalence study conducted in a teaching hospital. The randomization scheme used permuted blocks with subjects equally allocated to be positioned using either the blanket method or the table-ramp method. The end-point in either case was to achieve a head-elevated position, where the patients external auditory meatus and sternal notch were in the same horizontal plane. Although all patients were positioned by the same anesthesiologist, laryngoscopy and tracheal intubation were performed by trainees with various levels of expertise. Standard IV induction and tracheal intubation techniques were used. The time from loss of consciousness to the time after tracheal intubation when end-tidal CO2 was detected was recorded. The effectiveness of mask ventilation and quality of laryngeal exposure were also noted. RESULTS:The mean time (sd) to tracheal intubation was 175 (66) s in the blanket group, as compared to 163 (71) s in the table-ramp group. Assuming the bounds for equivalence are −55,55 s, our study found a 95% confidence interval of −36.22, 13.52 s using two one-sided tests for equivalence corresponding to a significance level of 0.05. There was no difference in the number of attempts at laryngoscopy (P = 0.21) and tracheal intubation (P = 0.76) required to secure the airway between the two groups. CONCLUSIONS:Before induction of anesthesia, obese patients can be positioned with their head elevated above their shoulders on the operating table, on a ramp created by placing blankets under their upper body or by reconfiguring the OR table. For the purpose of direct laryngoscopy and tracheal intubation, these two methods are equivalent.

Prevention of postoperative nausea and vomiting with granisetron and dolasetron in relation to CYP2D6 genotype.

We investigated the efficacy of granisetron and dolasetron in preventing postoperative nausea and vomiting. Because the metabolism of the various antiemetic 5-hydroxytryptamine type 3 (5-HT3) antagonists involves different isoforms of the hepatic cytochrome P450 system, we examined the relationship between the clinical efficacy of these drugs and polymorphic cytochrome P450 2D6 (CYP2D6) genotype. This prospective, randomized, double-blind study involved 150 adult patients with a moderate to high risk for postoperative nausea and vomiting. All subjects received dexamethasone at induction of anesthesia followed by either 12.5 mg of dolasetron or 1 mg of granisetron. We analyzed the number of complete responders (no vomiting or rescue medication) during the first 24 hours after surgery. CYP2D6 genotyping was performed using a TaqMan real-time polymerase chain reaction. A complete response was more frequent in the granisetron group (54.7%) compared with the dolasetron group (38.7%, P < 0.05). In subjects receiving dolasetron, carriers of the duplication of the CYP2D6 allele predicting ultrarapid metabolizer status had more frequent vomiting episodes (P < 0.05) than patients in the granisetron group. It is postulated that the difference in the antiemetic efficacy between two investigated 5-HT3 receptor antagonists may be associated with differences in the carrier status for the duplication of the CYP2D6 allele.

Comparison of the alteration of cardiac function by sevoflurane, isoflurane, and halothane in the isolated working rat heart

OBJECTIVES Despite its widespread use, little is known about sevofluranes physiologic effects. The direct myocardial effects of sevoflurane were compared with both halothane and isoflurane. DESIGN Administration of minimum alveolar concentration (MAC) fractions of anesthetic (0 to 3.0) was systematically varied to decrease the possibility of time-related effects on measured parameters. SETTING Isolated rat hearts were perfused using a working heart model where the parameters affecting myocardial work were carefully controlled and monitored. PARTICIPANTS To avoid confounding effects of prior anesthetic administration, hearts were removed from rats, after decapitation, in the absence of anesthetic. INTERVENTIONS In the first series, isolated perfused rat hearts were exposed to one of the three anesthetics in doses of 0 to 1.5 times MAC. In the second series, hearts were exposed to either sevoflurane or isoflurane in doses of 0 to 3.0 times MAC. The following variables were measured: the rate of change of left ventricular pressure; aortic flow rate; cardiac output; left ventricular end-diastolic pressure; the time constant of isovolumetric relaxation; and coronary vascular resistance. Oxygen consumption was measured during the first series. MEASUREMENTS AND MAIN RESULTS In the first series, all systolic variables were reduced in the presence of halothane when compared with either isoflurane or sevoflurane. Halothane affected diastolic function to a greater degree than either sevoflurane or isoflurane, as measured by the rate of relaxation and end-diastolic pressure. In the second series, at a dose of 3.0 times MAC, both sevoflurane and isoflurane decreased systolic and diastolic function, with a greater reduction in cardiac output, and peak aortic flow and higher left ventricular end-diastolic pressures observed with isoflurane. Coronary resistance and oxygen consumption were not affected by any of the anesthetics. CONCLUSIONS These data suggest that sevoflurane depresses cardiac function less than either halothane in doses of 1.0 and 1.5 x MAC or isoflurane at doses of 3 x MAC.

Metabolic and functional consequences of chronic alcoholism on the rat heart.

Abstract Conflicting data concerning cardiac function and energy metabolism in chronic alcoholism have been reported. Previous studies have shown preferential metabolism of ketone bodies and acetate, a primary metabolite of ethanol, leading to diminished myocardial high energy phosphate stores. We evaluated the following parameters in chronically, severely alcoholic rats: cardiac function utilizing working heart preparations with variable afterload; high energy phosphate stores; and mitochondrial respiratory activity. At low work load no differences existed in hemodynamic measurements between hearts from alcoholic and control animals; however, immediately after the imposition of an increased afterload, hearts from alcoholic animals exhibited a subnormal increment in pressure development. This decrement normalized during the following 30 min of perfusion. ATP and creatinine phosphate levels in hearts from alcoholic animals which were excised and immediately frozen and in those which had been perfused as working heart preparations for 120 min were not different from those found in controls. Studies on mitochondrial respiration revealed a diminished activity of the myocardium from alcoholic rats to utilize glutamate as a substrate; however, the utilization of other substrates was unaffected by alcohol consumption. It is concluded that in chronically alcoholic rats minor changes occur in cardiac function; the heart maintains normal high energy stores; however, alternative substrates are utilized for the production of energy.

Clinical associations between tinnitus and chronic pain

OBJECTIVE We sought to estimate the prevalence and severity of tinnitus in patients with chronic pain. STUDY DESIGN AND SETTING We conducted a prospective nonrandomized study in which a survey and the Tinnitus Handicap Inventory (THI) were distributed at a tertiary chronic pain clinic. RESULTS Seventy-two patients participated. 50 women (mean age, 53 years) and 22 men (mean age, 47.5 years); 54.2% reported having tinnitus. There was an even distribution of patients reporting the onset of tinnitus as before versus after the onset of pain. Four patients reported a direct association between tinnitus and pain. The mean THI score was 27 (of 100) (n = 35). Fifteen subjects scored less than 16, indicating no handicap, and 4 scored over 58, indicating a severe handicap. CONCLUSION The study results suggest a high incidence of tinnitus within this population. There were few strong associations between pain and tinnitus. Tinnitus does not significantly handicap the majority of these patients. SIGNIFICANCE Tinnitus is a common symptom in the chronic pain population but is not a significant problem for these patients.

The influence of neurophysiologic monitoring on the management of pediatric cardiopulmonary bypass.

We describe a process by which we sought to determine how the addition of intraoperative neurophysiologic monitoring (IONM) impacted the management of cardiopulmonary bypass (CPB) during pediatric cardiac surgery. While maintaining a consistent team of surgeons, anesthesiologists, nurses, and perfusionists, a multi-modal, IONM program was established consisting of Near Infrared Spectroscopy, Transcranial Doppler, and eight channel electroencephalography. A retrospective review of cases from 1 year before the institution of the IONM program was compared with data obtained from cases performed after neurophysiologic monitoring was established as a standard of care for pediatric patients on CPB. This comparative analysis of CPB management revealed a significant increase in the use of donor blood added to the CPB circuit prime as well as in the maintenance of a higher hematocrit during the bypass period after the implementation of IONM. These changes in the management of pediatric CPB correlated with recommendations of previous studies that examined postoperative neurophysiologic outcomes, suggesting that these changes were not only consistent with best practices, but that the presence of IONM data facilitated a transition to evidence-based practice.

Effect of valdecoxib pretreatment on pain and secondary hyperalgesia: a randomized controlled trial in healthy volunteers [ISRCTN05282752, NCT00260325]

BackgroundInduction of the COX-2 isoenzyme appears to play a major role in the genesis of central sensitization after nociceptive stimulation. This study aimed to investigate the efficacy of a single, oral dose of the specific COX-2 inhibitor-valdecoxib in attenuating the central sensitization – induced secondary hyperalgesia in a heat/capsaicin pain model in healthy volunteers.MethodsThe study was a randomized, double blind, placebo controlled, crossover, single dose efficacy trial using 20 healthy volunteers. Two hours following placebo or 40 mg, PO valdecoxib, participants underwent skin sensitization with heat/capsaicin, as well as supra-threshold pain and re-kindling measurements according to an established, validated pain model. Subjects rated pain intensity and unpleasantness on a visual analog scale and the area of secondary hyperalgesia was serially mapped.ResultsThe area of secondary hyperalgesia produced after 40 mg of valdecoxib was no different than that after placebo. Furthermore, there were no significantly relevant differences when volunteers were treated with valdecoxib or placebo in relation to either cold- or hot pain threshold or the intensity of pain after supra-threshold, thermal pain stimulation.ConclusionWe demonstrated that a single, oral dose of valdecoxib when does not attenuate secondary hyperalgesia induced by heat/capsaicin in a cutaneous sensitization pain model in healthy volunteers.

Effect of alloxan-induced diabetes on the hypertrophic response of rat heart.

Rats with alloxan-induced moderate and severe diabetes underwent banding of the ascending aorta. The increase in myocardial tissue and RNA was similar to controls in both groups of diabetic animals. This study indicates that the myocardial response to increased afterload is normal in the diabetic animal.

537 AEROBIC EXERCISE AND ATHEROSCLEROTIC RISK FACTORS IN ADOLESCENTS

The effect of a 7 week aerobic exercise program on atherosclerotic risk factors was assessed in 65 adolescent white males (mean age 15.8 yrs). Each subject was evaluated before and after the program for body weight, body mass index (BMI) (wgt/ ht2), % fat, systolic and diastolic blood pressure, maximum oxygen consumption (MVO2), exercise duration (ED) and fasting plasma lipids (cholesterol (CHL), triglyceride (TGL), high density lipoprotein (HDL-C) and low density lipoprotein (LDL-C)). Mean weight (± SD) was 70.7 ± 16.5 kg before and 71 ± 16.5 after training (p NS). BMI was 23.2 ± 4.6 and 23.2 ± 4.7 (p NS). % fat decreased by 7.9% from 20.3 ± 6.9 to 18.7 ± 6.3% (p <0.001). Systolic and diastolic blood pressure remained unchanged, MVO2 increased by 10.8% from 45 ± 6.5 to 49.9 ± 7.8 ml/kg-min−1 (p < 0.0001) and ED increased from 20.5 ± 2.6 to 21.1 ± 2.5 min (p < 0.01). Plasma lipids (mg/dl) were similar pre and post exercise-CHL 154 ± 32 and 152 ± 31, TGL 87 ± 46 and 92 ± 40, HDL-C 46 ± 12 and 45 ± 9 and LDL-C 90 ± 21 and 88 ± 27. These results demonstrate that with the exception of obesity, atherosclerotic risk factors are not modified by an effective aerobic training program in adolescent males. This is at variance from that reported in adults undergoing aerobic training.

226 HEMODYNAMIC EFFECTS OF PROLONGED SEIZURES IN NEONATAL PIGS

The cardiovascular effects of seizures in the neonate are not well defined. To determine the changes in systemic and pulmonary artery pressure, cardiac output, and left ventricular contractility during seizures, one week old pigs were intubated, paralyzed, mechanically ventilated, and catheterized with a swan-ganz catheter. Seizures were induced with bicuculline (5 mg/kg/hr continuously i.v.) in 5 animals (6 controls received saline). Early changes consisted of significant systemic and pulmonary arterial hypertension. After 2 hours of seizures, the animals developed progressive systemic hypotension (saline, 93 ± 4 mmHg; bicuculline, 66 ± 8; Mean ± SE; p<0.01; student t test) and decreased cardiac function (cardiac output: saline, 174 ± 27 ml/kg/min; bicuculline, 91 ± 15 ml/kg/min; p<0.01). M-mode echocardiography disclosed a decrease in left ventricular contractility (Ejection Fraction: Saline, 0.70 ± 0.03; bicuculline, 0.49 ± 0.08; p<0.001). Cardiac tissue frozen in situ showed significant increase in lactate (Saline, 13.3 ± 0.7 mmol/g/dry wt.; bicuculline, 102.8 ± 4.9: p<0.01), and reductions in glucose, triglyceride, and ATP (Saline, 17.1 ± 0.1 mmol/g/dry wt.; bicuculline, 11.5 ± 0.3; p<0.01). Prolonged seizures result in severe cardiac dysfunction which may be due to tissue acidosis or catecholamine release.