摘要:

The authors studied the abnormalities of gas exchange and lung mechanics in a canine model of bronchopleural fistula during intermittent positive pressure ventilation (IPPV) and high-frequency oscillatory ventilation (HFOV). The left lower lobe bronchus was opened to atmosphere and it was determined that end expired volume was best maintained at frequencies of 45–50 breaths/min. during IPPV. Comparing alternating periods of IPPV and HFOV in six dogs (Group 1) at matched airway opening pressure (Pao), we found that PaO2decreased significantly to 68 ± 14 mmHg and 69 ± 24 mmHg, respectively, on opening the fistula. In a second group of six dogs (Group 2), when Paowas increased by additional bias flow into the ventilatory circuit during both IPPV and HFOV, PaO2increased significantly to 89 ± 12 mmHg and 87 ± 8 mmHg, respectively. Repeating Group 2 studies after induction of oleic acid lowpressure pulmonary edema demonstrated that conventional IPPV was associated with large intrapulmonary shunts. HFOV, however, maintained gas exchange at near baseline values. For both Group 1 and Group 2, the calculated gas flow through the fistula was significantly less at all levels of airway pressure during HFOV. The authors conclude that HFOV offers advantages over conventional IPPV in the maintenance of oxygenation and in the reduction of gas leak through the fistula.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

A carcinogen bioassay of nitrous oxide (N2O) was performed in groups of male and female Swiss-Webster mice exposed to either air (n = 179), 10% N2O (n = 152), or 40% N2O (n = 151) for 4 h per day, 5 days per week. After 78 weeks of exposure, there was a 5- week period without treatment following which surviving mice were killed. Mice killed at this time or dyingin extremisat other times were subjected to complete autopsy unless advanced autolysis or cannibalism precluded examination. Mean body weights for male and female mice in the 10% N2O group were the same as those in the air control group throughout the study, whereas they were 5% less in the 40% N2O group. Mean organ weights for N2O-treated mice were not statistically different from those of control mice. Gross and microscopic examination of tissues revealed a variety of neoplastic and nonneoplastic lesions; however, their presence was unrelated to treatment.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The influence of etomidate on regional cerebral function as reflected by regional cerebral glucose utilization (rCMRGlc) was studied. Three experiments were performed. In the first, rats had both left femoral vessels cannulated and were placed in restraining cages. Etomidate was infused intravenously (12 mg/kg) at a rate of 6 mg · kg−1· min−1. This large dose had a modest effect on blood pressure and heart rate, which could be explained by the elimination of stress in restrained rats, and no effect on body temperature, PaO2, PaCO2, orpH. A second group of rats were used to determine the effect of etomidate on the ratio of brain glucose to plasma glucose, which is necessary for calculating rCMRGlc. In the third experiment rCMRGlcwas measured in unstressed rats. The rats were anesthetized with an intravenous dose of 1, 2, 6, or 12 mg/kg etomidate infused at a rate of 6 mg · kg−1· min−1. Etomidate had a marked effect on glucose consumption in many, but not all, cerebral structures. The forebrain (telencephalon and diencephalon) was most affected (–25% to –35%) while the hindbrain was minimally affected. There was no demonstrable dose dependency; 1 mg/kg depressed rCMRGlcas much as 12 mg/kg. The pattern of rCMRGlcdepression is in accord with the minimal effects observed on physiologic variables and similar to that caused by the steroid anesthetic Althesin,® although the depression seen was not as severe. The pattern of metabolic depression produced by etomidate differs markedly from that produced by barbiturates, which affect all brain regions to a similar degree. The possibility is discussed that the anesthetic effect of etomidate may be mediated by receptors.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The prolonged effect of barbiturates and inhalation anesthesia on airway response to histamine was studied in five groups of dogs. Group B (n = 10), H24 (n = 5), and H72 (n = 5) were anesthetized with sodium thiamylal (B) or halothane and N2O (H24, H72) for 3 h, during which a dose-response curve to histamine was obtained. The animals were then allowed to recover; 24 h (B and H24) or 72 h later, the animals were killed and anin vitrodose–response curve to histamine was obtained on a tracheal smooth muscle (TSM) specimen. Group C (n = 5), the control group, had no prolonged exposure to anesthesia. The dogs were immediately killed and thein vitrohistamine response of the TSM was measured. The results (mean ± SE) showed that the smooth muscle contractile properties (i.e., the maximum contraction to electrical field stimulation) were comparable in all four groups: 111 ± 12 g (B); 168 ± 23 g (H24); 106 ± 32 g (H72); and 107 ± 31 g (C). The maximum response (mean ± SE) to histamine (as % of maximum electrical contraction) was: 15 ± 6% (B), 30 ± 9% (H24), 32 ± 12% (H72), and 50 ± 8% (C). Statistical analysis of the data showed that the histamine response of Group B and Group H24 was significantly decreased compared to Group C (P< 0.01 and < 0.05, respectively); in Group H72 the results were not significantly different from Group C (0.1 >P> 0.05). To exclude the possibility that the diminution in histamine response was due to thein vivoexposure to histamine, a fifth group of animals served as sham. The animals were anesthetized with sodium thiamylal and killed 24 h later, having inhaled no histamine. The results obtained in this group were comparable with those obtained in Group B. The authors conclude that exposure to general anesthetics decreased airway smooth muscle sensitivity to histamine for at least 24 h after the cessation of anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors studied 12 surgical patients in the intensive care unit post coronary artery bypass graft surgery and ten nonsurgical patients in the coronary care unit with chronic heart failure to determine the usefulness of the pulmonary arterial wedge pressure as an indicator of left ventricular preload. Left ventricular end diastolic volume was derived from concomitant determination of ejection fraction (gated blood pool scintigraphy) and stroke volume (determined from thermodilution cardiac output). In the nonsurgical patients, there was a significant correlation between changes in pulmonary arterial wedge pressure and left ventricular end-diastolic volume (P< 0.05, r = 0.57). In the 12 patients studied during the first few hours after surgery, there was a poor correlation between changes in pulmonary wedge pressure (range = 4–32 mmHg) and left ventricular end-diastolic volume (range = 25–119 ml/m2), and a poor correlation between pulmonary arterial wedge pressures and stroke work index. In contrast, there was a good correlation between left ventricular end-diastolic volume and stroke work index. The poor correlation between the pulmonary arterial wedge pressure and left ventricular end-diastolic volume was not explained by changes in systemic or pulmonary vascular resistance. The altered ventricular pressure–volume relationship may reflect acute changes in ventricular compliance in the first few hours following coronary artery bypass graft surgery. While measurement of pulmonary arterial wedge pressure remains valuable in clinical management to avoid pulmonary edema, it cannot reliably be used as an index of left ventricular preload while attempting to optimize stroke volume in patients immediately following coronary artery bypass graft surgery.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Neurophysiologic and local cerebral metabolic mapping techniques indicate that seizures associated with lidocaine toxicity originate in subcortical brain structures. Normally local cerebral blood flow (1-CBF) is quantitatively coupled to local cerebral metabolic rate for glucose (1-CMRg). In the present study the response of 1- CBF to a lidocaine-induced preconvulsive state (localized seizure activity in the absence of a grand mal seizure) was evaluated in rats anesthetized with 60% nitrous oxide. Lidocaine administered as a bolus (20 mg/kg) followed by an infusion (4 mg/kg) over 5.5 min resulted in progressive alteration in the electroencephalogram (EEG). L-CBF was studied with the14C-iodoantypyrine autographic method when the preconvulsive EEG pattern consisted of a repetitive spike and wave complex at a frequency of 14 ± 1 · min−1complexes, superimposed on practically isoelectric background activity. Under these conditions high doses of lidocaine significantly (P< 0.05) decreased (range –30% to –68%) 1-CBF in 71% of the 34 brain regions studied. The greatest exception to this trend for 1-CBF to decrease was observed in the limbic system wherein 1-CBF remained within control ranges in eight of the 11 structures evaluated. Qualitative comparison of lidocaine 1-CBF changes with 1-CMRgchanges obtained under similar conditions indicated a general trend for local flow and metabolism to decrease in parallel. Exceptions to this were confined to certain limbic areas (amygdala and hippocampus) in which increases in l-CMRgwere more than 100% greater than slight (P> 0.05) increases in 1-CBF. This comparison demonstrates uncoupling of local brain metabolism from blood flow during lidocaineinduced subcortical epileptoid discharges (preconvulsive state) in areas recognized to be prone to irreversible damage when seizure activity is much prolonged beyond the duration of this study.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of three different plasma levels of verapamil on coronary hemodynamics and myocardial metabolism in the presence of 1.61 ± 0.05% end-tidal concentration of isoflurane (mean ± SEM) were studied in a canine model, using a thermodilution coronary sinus catheter to measure coronary sinus blood flow and pressure and to provide coronary sinus plasma samples. A control group receiving only isoflurane was also studied (n = 6). Plasma arterial verapamil levels of 55 ± 7 (n = 6); 134 ± 7 (n = 10); and 301 ± 37 ng · ml−1(n = 5), were achieved by a loading dose followed by a continuous infusion for 30 min. The only changes with time in the isoflurane group were decreases in left ventricular maximum rate of tension development (dP/dt) and left ventricular stroke work index compared with control after 90 min without changes in myocardial oxygen balance. The low plasma verapamil level caused reductions in heart rate, mean and diastolic arterial pressure, and left ventricular dP/dt without changes in myocardial oxygen supply or myocardial metabolism. Intermediate verapamil concentrations produced a transient initial increase in heart rate and a reduction in stroke volume index. With the intermediate and the highest levels of verapamil, mean and diastolic arterial pressure, left ventricular dP/dt, and cardiac index were decreased. An increase in arterial norepinephrine plasma levels was seen in the intermediate and the highest levels of verapamil; however, a transient coronary vasodilation occurred without changes in myocardial oxygen balance. Significant prolongation of the PR interval was observed in all verapamil groups, with second or third degree heart block in some of the higher-dose animals. Despite no adverse effects on myocardial oxygen balance when these concentrations of isoflurane and verapamil were combined, conduction block at moderate plasma levels may limit the usefulness of verapamil during isoflurane anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of prophylactic infusion of 1 µg · kg−1· min−1nitroglycerin (NTG) on the incidence of ischemia, hypertension, hypotension and perioperative myocardial infarction were studied in 81 patients during coronary artery bypass grafting (CABG). Forty-one patients (Group 1) received NTG and 40 patients (Group 2) received placebo. All patients received fentanyl for anesthesia and pancuronium. Mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), heart rate (HR), and cardiac output (CO) were measured before and after induction of anesthesia, after intubation, before and after chest incision, after sternotomy, after the pericardium was opened, and during normothermic cardiopulmonary bypass. Myocardial ischemia and infarction were diagnosed from the ECG, hypertension was denned as a 20% increase in MAP, and hypotension was defined as a 20% decrease in MAP compared with preinduction values. No significant differences between Groups 1 and 2 in HR, PCWP, or CO were seen. MAP was significantly lower in Group 1 than Group 2 (P< 0.05) before chest incision, but increased to levels equal to Group 2 after sternotomy. Hypertension occurred in 32 Group 2 patients and 25 Group 1 patients (0.05 <P< 0.1). Group 1 patients had 0.95 ± 0.14 episodes per patient of hypertension, while Group 2 patients had 2.10 ± 0.31 episodes (P< 0.05). Hypotension occurred in 20 Group 1 patients but only six Group 2 patients (P< 0.05). There was no difference in the incidence of ischemia. In Group 1, nine patients (22%) had ECG changes of ischemia, while 12 patients in Group 2 (30%) had ischemia. Three patients in each group (7%) had evidence of perioperative myocardial infarction. We conclude that prophylactic administration of 1 µg · kg−1· min−1of NTG during fentanyl anesthesia in patients undergoing CABG did not prevent myocardial ischemia or reduce the incidence of perioperative myocardial infarction, but both lowered the incidence of hypertension, especially during intubation, and increased the incidence of hypotension (P< 0.05).

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

In an attempt to define the risk to the fetus associated with anesthesia and surgery during pregnancy, a study was performed using health insurance data from the province of Manitoba (1971 to 1978). Each of the 2,565 women undergoing incidental surgery during pregnancy (Group A) was paired with a pregnant female not undergoing surgery (Group B) by maternal age and area of residence. Both groups were linked to a separately maintained provincial congenital- anomalies registry to ascertain the frequency of anomalies. There was no signficant difference in the rate of congenital anomalies between the two groups, implying no strong teratogenic effect. However, there was an increased risk of spontaneous abortion in those undergoing surgery with general anesthesia in the first or second trimester, most notably after gynecologic procedures (estimated risk ratio = 2.00), but also following procedures anatomically remote from the conceptus (estimated risk ratio = 1.54). While it is concluded that surgery with general anesthesia is associated with a higher incidence of abortion, it is conjectural at present which factor(s) account for the observed increase in fetal risk.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

There is no single, simple diagnostic test available to enable identification of malignant hyperthermia (MH) susceptible individuals. Recently, two novel low-molecular-weight proteins (15,000 daltons and 13,500 daltons) that were not present in normal muscle were identified in MH muscle and it was felt that this might eventually be of assistance in diagnosing MH. The authors of this report have been unable to verify these results. Polyacrylamide gel electrophoresis of the soluble proteins from muscle of four MH-susceptible and four normal individuals showed no differences in the electrophoretic fractionation patterns. Therefore, the authors conclude that the differences in protein composition previously reported in MH muscle are not characteristic of this syndrome.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID