Search

Although ultrasound-guided regional anaesthesia has gained in popularity, few data exist describing the optimal location(s) to inject local anaesthetic. Our objective was to compare, for interscalene blocks, the effectiveness of an injection between the middle scalene muscle and brachial plexus sheath (peri-plexus) with an injection within the brachial plexus sheath (intra-plexus). We enrolled 170 patients undergoing shoulder surgery with general anaesthesia and interscalene block in this randomised, controlled trial. Our primary outcome variable was loss of shoulder abduction. Block quality was also measured and defined by an evaluation of onset time, sensory and motor loss and duration. There was no difference between the two groups in block onset times or block quality. After adjusting for sex, age and volume injected, intra-plexus blocks lasted a mean of 2.6 h (16%) longer (95% CI 0.25-5.01, p=0.03) than peri-plexus blocks.

This study compared voluntary movement strategies of patients with unilateral peripheral vestibular hypofunction with those of age-matched healthy control subjects. All subjects performed three voluntary movement tasks with their dominant upper extremity: a forward flexion arm movement through 90 degrees, a reach to an overhead target, and a reach to a side target. Subjects performed the movement tasks sitting and standing (Body Position), and under precued and choice reaction time (RT) conditions (Task Certainty). Measures of motor planning and movement execution included RT and movement time (MT), respectively. Statistical analysis included separate Group x Task Certainty x Body Position ANOVA calculations for each task. Across tasks, results suggested no between group differences for RT. A Task Certainty main effect for the side and overhead tasks indicated that the choice RT situation resulted in longer RTs as compared to the precued RT condition. Movement time differed between the two groups. Across all three voluntary movement tasks, vestibular impaired subjects moved more slowly than control subjects. Providing vestibular subjects with a precue did not bring MT performance to the level of controls. Body position influenced MT for the side task only. Across both groups of subjects, MT for the side task was longer when performed in the standing position. The results of this study suggest that individuals with unilateral peripheral vestibular hypofunction initiate voluntary movement responses with similar timing as control subjects, but require more time to complete the movement. Vestibular rehabilitation should include goal-directed movement and should address issues of movement speed.

Pituitary abscesses, rare lesions, may be divided into primary and secondary types. Primary pituitary abscesses occur within a previously healthy gland, while secondary abscesses arise within an existing lesion, such as an adenoma, craniopharyngioma, or Rathke's cleft cyst. Secondary abscesses share radiologic characteristics with the lesions from which they arise. There has been no review of the MRI characteristics of primary pituitary abscesses. We report two cases and review the literature. The typical primary pituitary abscess gives the same or slightly lower signal than brain on T1-weighted images, and could be mistaken for a solid mass or presumed to represent a pituitary adenoma. Contrast-enhanced images are useful, demonstrating absence of central enhancement, suggesting a fluid or necrotic center. In one of our cases, meningeal enhancement was obvious; this has not been reported previously and may be diagnostic, when associated with a rim-enhancing pituitary mass.

Although halothane reduces digitalis toxicity, other anesthetics, notably cyclopropane, increase toxicity. This study determined the effects of isoflurane on digitalis toxicity in isolated cardiac tissue and compared these effects with those of halothane.Standard microelectrode techniques were used to record action potentials from excised canine Purkinje fibers. Fibers were paced at cycle lengths between 1,000 and 250 ms for 20 beats to induce delayed afterdepolarizations, which are membrane potential oscillations indicative of intracellular Na+ and Ca2+ overload, produced in these experiments by digitalis toxicity. The digitalis glycoside ouabain, 2 x 10(-7) M, was added to the Tyrode's solution superfusate to induce delayed after-depolarizations. Action potential variables and the coupling interval and amplitude of afterdepolarizations were then measured. Isoflurane (0.5%, 1%, or 2%) was added with a calibrated vaporizer (n = 8). In a second set of experiments (n = 10), isoflurane 1.25% or halothane 0.75% was added to the superfusate. After measurements had been made, the other agent was substituted.Ouabain produced primary and secondary delayed afterdepolarizations, which were reduced in amplitude by isoflurane in a dose-related manner (P = 0.0002). Action potential duration to 90% repolarization was shortened by ouabain (P = 0.009) and remained shortened during isoflurane administration. Action potential duration to 50% repolarization was shortened by isoflurane 2%. Halothane and isoflurane were equally effective in reducing the amplitude of delayed afterdepolarizations (both P = 0.0002). In three fibers, triggered extrasystoles appeared. Halothane and isoflurane each abolished extrasystoles. In two fibers, sustained triggered activity appeared. Isoflurane abolished the arrhythmia in each fiber.Isoflurane and halothane are equally effective in reducing delayed afterdepolarizations induced by ouabain toxicity.

Intraoperative reversible cryothermal mapping of recurrent ventricular tachycardia was performed in seven patients with left ventricular aneurysms with use of a 0 degrees C ice probe. A single, reproducible cryotermination site was found in each patient. The cryotermination site was uniformly located in an area where local electrograms obtained during ventricular tachycardia showed electrical activation during the diastolic portion of the surface electrocardiogram, and was different than the site of activation coincident with the onset of the QRS complex on the surface electrocardiogram (earliest reactivation site or ERS) by 4.5 +/- 2.7 cm (mean +/- SD) in five of seven patients. Sinus rhythm late potentials were recorded at the cryotermination site in five of six patients and from the ERS in one. In five patients, extensive subendocardial resection including both the ERS and cryotermination sites was performed. In two patients only the cryotermination site was excised. In six survivors, including one in whom only the cryotermination site was excised, ventricular tachycardia could not be induced 2 weeks after surgery and has not recurred during the follow-up period of 7 to 17 months (12 +/- 4.5 months, mean +/- SD). Reversible cryothermal mapping may provide additional important information not obtained by standard electrogram mapping of ventricular tachycardia that may help guide surgical therapy of recurrent ventricular tachycardia.

Large liquid scintillation counters offer a unique combination of high sensitivity and moderate energy resolution and hence are particularly useful for the rapid measurement of the radioactivity of the human body and other large samples. This counter permits measurements of internal gamma contamination of the human body at concentrations 1000 times less than maximum permissible levels. Such an instrument can, therefore, have many practical applications to diagnosis in clinical and experimental medicine. The instrumentation to be described is used with the new Los Alamos human counter but the techniques are applicable to large liquid scintillation counters in general. Objectives in this system are: 1) optimizing pulse-height (energy) resolution from the detector, 2) optimizing SNR, 3) long-term stability and freedom from rate and overload deficiencies and 4) accuracy, speed and versatility of data handling and processing.

SUMMARY Plasma human growth hormone (HGH) and serum phosphorus concentrations were measured during the fasting ambulatory state in middleaged men, pre- and postmenopausal women and postmenopausal women who had been taking 20–40 μg mestranol daily for 1–3 years. The mean plasma HGH concentrations were consistently higher in the women than they were in the men, there was little difference between the mean values for pre- and postmenopausal women, and the mestranoltreated women had significantly higher mean values than the untreated postmenopausal women. The mean serum phosphorus concentration was significantly higher after menopause and was significantly lower in those women on long-term lowdose mestranol therapy. A significant direct correlation was found between serum phosphorus and plasma HGH concentrations in untreated postmenopausal women. It is suggested that the postmenopausal relative hyperphosphataemia is consistent with increased HGH activity.

A new time‐delay analyzer encompassing a wide flexible time base is described. Time channels of 0.001, 0.01, 0.1, 1, and 10 sec width are provided; these may be combined in progressive sequence or used individually for essentially an infinite number of channels. Provision is made for either photographic or electric recording. Data obtained with the new analyzer agree with a conventional ten‐channel time‐delay analyzer over the limited range of the latter. A simple procedure is given for checking correct operation of the system.

The electrophysiologic effects of acutely and chronically administered amiodarone on canine Purkinje fibers were assessed using microelectrode techniques to record intracellular action potentials. Chronically treated dogs received amiodarone for 3 weeks (serum levels, 0.91 +/- 0.09 microgram/ml or 1.42 X 10(-6) M). Acute studies were performed using fibers from untreated dogs superfused for 1 h with 5 X 10(-5) M amiodarone (32 micrograms/ml) in Tyrode's solution (KCl = 4 mM). Acute superfusion shortened the action potential duration to 50 and 90% repolarization by 41 and 8%, respectively (p less than 0.01), and decreased Vmax of phase 0 from 418 +/- 20 to 309 +/- 23 V/s (p less than 0.01) (paced cycle length of 500 ms). Prominent use-dependent depression of Vmax was noted. Acute exposure of fibers from untreated dogs to blood from dogs chronically treated with amiodarone using the blood cross-perfusion technique decreased the action potential duration to 50% repolarization and Vmax, similar to acute exposure in Tyrode's solution. Blood cross-perfusion was used to study fibers from treated dogs superfused with blood from another amiodarone-treated dog. Chronic amiodarone prolonged the action potential duration to 90% repolarization by 13% (p less than 0.02) and did not change Vmax when compared to control studies using fibers obtained from untreated dogs superfused with blood from untreated dogs. Thus, the effects of acutely superfused amiodarone on action potentials of canine Purkinje fibers differ from the effects of chronically administered amiodarone.

The metabolism of halothane was examined in patients with acyanotic and cyanotic congenital heart disease undergoing open heart surgery. Statistically significant (P less than 0.05) pre-surgical differences between acyanotic and cyanotic groups included pH (7.46 +/- 0.02 vs 7.36 +/- 0.02), PaO2 (277 +/- 58 vs 51 +/- 3 torr), O2 saturation (97 +/- 1 vs 74 +/- 4%), and hematocrit (45 +/- 3 vs 58 +/- 2%). Serum fluoride levels were significantly greater in cyanotic than in acyanotic groups 2-4 hours after initial exposure to halothane. Both groups had significant intragroup increases in serum levels of fluoride, bromide, and trifluoroacetic acid. Significant increases in serum levels of lactate dehydrogenase, creatinine phosphokinase, and glutamic oxaloacetate transaminase were observed in both groups, whereas, the cyanotic patients had additional significant increases in blood urea nitrogen and direct bilirubin. The cyanotic group also had higher total and direct serum bilirubin levels than the acyanotic group. Therefore, patients with cyanotic congenital heart disease had greater reductive metabolism of halothane than acyanotics. However, cyanotic and acyanotic patients had essentially similar postoperative derangements in hepatic and renal function.

We evaluated the hemodynamic effects of 7 mg/kg intravenous calcium chloride (CaCl2) or placebo in 20 adults with regurgitant aortic and/or mitral valves before and after induction of anesthesia with fentanyl (50 micrograms/kg), followed by pancuronium (0.1 mg/kg) and 100% oxygen. CaCl2 produced no changes in mean systemic, pulmonary arterial, central venous, or pulmonary capillary wedge pressures or vascular resistances before or after induction of anesthesia. A significant increase in left ventricular stroke work index was seen 1 min after CaCl2 was administered after induction of anesthesia (from 31.29 +/- 3.00 to 37.44 +/- 3.81 g X m X M-2). Before induction, CaCl2 decreased heart rate from 93.9 +/- 9.6 to 85.2 +/- 8.7 beats/min (statistically significant 2.5 and 10 min after CaCl2) and after induction from 104.6 +/- 8.4 to 89.3 +/- 7.5 (significant at 1, 2.5, 5, and 10 min). These results suggest that CaCl2 is associated with an immediate increase in ventricular performance and that the subsequent decrease in heart rate is not sufficient to contraindicate use of CaCl2 as an inotrope in patients with chronic valvular regurgitation. The effects of CaCl2 injection in man on pulmonary shunt fraction (Qs/Qt) have not been described previously. We found no change in Qs/Qt, suggesting that CaCl2 has no direct effect on distribution of pulmonary blood flow.

The authors studied possible interactions between halothane and quinidine on the action potentials of canine Purkinje fibers superfused with Tyrode's solution. Using standard microelectrode techniques and a physiologic pacing rate (2 Hz), halothane in concentrations from 0.5% to 2% decreased the action potential duration to 50% repolarization (ADP50). Total ADP (APD100), in contrast, increased after 1% and 2% halothane. Resting membrane potential (RMP) and action potential amplitude (APamp) increased after 0.5% halothane, but returned to control with higher halothane levels. Conduction time (CT) increased at each halothane level. Pacing at faster (3 Hz) or slower (1 Hz) rates did not markedly alter the effects of halothane. Quinidine 1 X 10(-5)M decreased the phase O upstroke (Vmax) and prolonged APD100 and CT. When halothane was added, RMP and APamp decreased, Vmax decreased further, and APD100 and CT were markedly prolonged. This resulted in conduction block or inexcitability, especially at faster pacing rates (3 Hz). Synergistic interactions between halothane and quinidine were found on RMP, APamp, APD100, and CT. Effects on Vmax, APD50, and action potential duration to 90% repolarization (APD90) were additive. It is concluded that quinidine and halothane act synergistically to decrease action potential amplitude, lower RMP, and prolong conduction. Severe depression of conduction often progressed to conduction block or inexcitability when halothane, 2%, was administered during superfusion with therapeutic concentrations of quinidine.

The effect of pulmonary ventilation upon systemic arterial blood gases during cardiopulmonary bypass in the presence of left ventricular ejection was evaluated in 20 adult male patients undergoing coronary artery bypass grafting. Following rewarming, establishment of a sinus rhythm, and production of a pulse pressure of at least 20 mm Hg on the arterial pressure trace caused by left ventricular ejection, arterial blood gases were obtained from the arterial and venous extracorporeal circuits and the radial arterial cannula. Patients were then randomly assigned to a nonventilation (n = 10) or a ventilation (n = 10) group. The ventilation group was given 10 breaths/min with 100% oxygen at a tidal volume of 10 ml/kg. Whereas the nonventilation group received apneic oxygenation at zero end-expiratory pressure. After 5 minutes the arterial blood gas data were again obtained. Significant findings (p less than 0.05) included decreases in systemic carbon dioxide tension and increases in systemic pH in the ventilation group and decreases in systemic oxygen tension in the nonventilation group. Although the changes in the arterial blood gases were significant, these changes occurred well within the limits of clinical acceptability. It is concluded that left ventricular ejection for short periods during full cardiopulmonary bypass does not necessitate pulmonary ventilation.

The effect of postoperative fluid management on pulmonary extravascular thermal volume (ETVL) as in index of pulmonary extravascular water after coronary artery bypass grafting was compared, using the thermal-dye technique, among five patients who received 5% albumin (group A), five patients who received 6% hydroxyethyl starch (group H), and five who received lactated Ringer's solution (group C). Intraoperatively, all patients received lactated Ringer's solution intravenously, and the cardiopulmonary bypass (CPB) circuit prime included 5% albumin. No statistically significant changes in ETVL occurred postoperatively in any group, nor did ETVL differ significantly between groups. After CPB, colloid osmotic pressure (COP) significantly decreased and pulmonary artery wedge pressure (WP) and the WP-COP gradient significantly increased in each group, implying an increase in transcapillary fluid flux. Cardiac index changed variably. Pulmonary shunt fraction (Qsp/Qt) did not change in groups A and C but decreased during CPB in group H (from 0.22 +/- 0.03 to 0.16 +/- 0.11). Postoperatively, patients in the three groups received similar volumes of fluids and had similar perioperative weight gains. By the next morning (AM1), COP increased in all groups, returning to levels noted before CPB in group C, and exceeding these levels in groups A and H. Wedge pressure was similar in all three groups on AM1. PaO2 decreased significantly, and alveolar-arterial oxygen partial pressure difference increased significantly in all groups on AM1. In Group H, Qsp/Qt returned to levels observed before CPB by AM1 (0.27 +/- 0.09). We conclude that in patients without postoperative increases in WP, ETVL changes minimally during CPB and is not influenced by the type of fluid administered as the primary volume replacement in the postoperative period.