摘要:

BackgroundLoad‐dependent impairment of left ventricular (LV) function was observed after leg elevation in a subgroup of coronary surgery patients. The present study investigated underlying mechanisms by comparing hemodynamic effects of an increase in LV systolic pressures with leg elevation to effects of a similar increase in systolic pressures with phenylephrine.MethodsThe study was performed in patients undergoing elective coronary surgery prior to cardiopulmonary bypass. High‐fidelity LV pressure tracings (n = 25) and conductance LV volume data (n = 10) were obtained consecutively during leg elevation and after phenylephrine administration (5 [micro sign]g/kg).ResultsLeg elevation resulted in a homogeneous increase in end‐diastolic volume. The change in stroke volume (SV), stroke work (SW) and dP/dtmaxwas variable, with an increase in some patients but no change or a decrease in other patients. For a matched increase in systolic pressures, phenylephrine increased SW and dP/dtmaxin all patients with no change in SV. Load dependence of relaxation (slope R of the [Greek small letter tau]‐end‐systolic pressure relation) was inversely related for changes in SV, SW, and dP/dtmaxwith leg elevation but not with phenylephrine.ConclusionsThe different effects of leg elevation and phenylephrine suggest that the observed decrease in SV, SW, and dP/dtmaxwith leg elevation in some patients could not be attributed to an impaired contractile response to increased systolic LV pressures. Instead, load‐dependent impairment of LV function after leg elevation appeared related to a deficient length‐dependent regulation of myocardial function.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundIntrathecal clonidine produces dose‐dependent postoperative analgesia and enhances labor analgesia from intrathecal sufentanil. The authors evaluated the dose‐response potency of intrathecally administered clonidine by itself during first stage of labor with respect to analgesia and maternal and fetal side effects.MethodsThirty‐six parturients requesting labor analgesia were included in this prospective, randomized, double‐blind study. Parturients with < 6 cm cervical dilatation received either 50, 100, or 200 [micro sign]g intrathecal clonidine. The authors recorded visual analog pain score (VAPS), maternal blood pressure and heart rate, ephedrine requirements, and sedation at regular intervals and fetal heart rate tracings continuously. Duration of analgesia was defined as time from intrathecal clonidine administration until request for additional analgesia.ResultsClonidine produced a reduction in VAPS with all three doses. The duration of analgesia was significantly longer in patients receiving 200 [micro sign]g (median, 143; range, 75–210 min) and 100 [micro sign]g (median, 118; range, 60–180 min) than 50 [micro sign]g (median, 45; range, 25–150 min), and VAPS was lower in the 200‐[micro sign]g than in the 50‐[micro sign]g group. In the 200‐[micro sign]g group, hypotension required significantly more often treatment with ephedrine than in the other groups. No adverse events or fetal heart rate abnormalities occurred.ConclusionsFifty to 200 [micro sign]g intrathecal clonidine produces dose‐dependent analgesia during first stage of labor. Although duration and quality of analgesia were more pronounced with 100 and 200 [micro sign]g than with 50 [micro sign]g, the high incidence of hypotension requires caution with the use of 200 [micro sign]g for labor analgesia.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe most common measure to compare potencies of volatile anesthetics is minimum alveolar concentration (MAC), although this value describes only a single point on a quantal concentration‐response curve and most likely reflects more the effects on the spinal cord rather than on the brain. To obtain more complete concentration‐response curves for the cerebral effects of isoflurane, sevoflurane, and desflurane, the authors used the spectral edge frequency at the 95th percentile of the power spectrum (SEF95) as a measure of cerebral effect.MethodsThirty‐nine patients were randomized to isoflurane, sevoflurane, or desflurane groups. After induction with propofol, intubation, and a waiting period, end‐tidal anesthetic concentrations were randomly varied between 0.6 and 1.3 MAC, and the EEG was recorded continuously. Population pharmacodynamic modeling was performed using the software package NONMEM.ResultsThe population mean EC50values of the final model for SEF (95) suppression were 0.66 +/‐ 0.08 (+/‐ SE of estimate) vol% for isoflurane, 1.18 +/‐ 0.10 vol% for sevoflurane, and 3.48 +/‐ 0.66 vol% for desflurane. The slopes of the concentration‐response curves were not significantly different; the common value was [Greek small letter lambda] = 0.86 +/‐ 0.06. The Ke0value was significantly higher for desflurane (0.61 +/‐ 0.11 min‐1), whereas separate values for isoflurane and sevoflurane yielded no better fit than the common value of 0.29 +/‐ 0.04 min (‐1). When concentration data were converted into fractions of the respective MAC values, no significant difference of the C50values for the three anesthetic agents was found.ConclusionsThis study demonstrated that (1) the concentration‐response curves for spectral edge frequency slowing have the same slope, and (2) the ratio C50(SEF95)/MAC is the same for all three anesthetic agents. The authors conclude that MAC and MAC multiples, for the three volatile anesthetics studied, are valid representations of the concentration‐response curve for anesthetic suppression of SEF95.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundLaparoscopic cholecystectomy is presumed to induce a reduction in diaphragmatic activity. Indirect indices of diaphragmatic function based on tidal changes in pressures and cross‐section area measurements can be unreliable in the post‐operative phase. The present study evaluates diaphragmatic activity by directly recording diaphragmatic EMG (EMG (dia)) data, along with indirect indices.MethodsThirteen adult patients (American Society of Anesthesiologists physical status I or II) undergoing laparoscopic cholecystectomy were examined preoperatively for inspiratory tidal changes in gastric (Pgas‐insp) and esophageal (Peso‐insp) pressures, and tidal changes in ribcage (Vthor) and abdominal (Vabd) cross‐section areas and then again at 1, 6, and 24 h postoperatively combined with EMGdiarecordings. Variations in inspiratory gastric (Delta Pgas‐insp) and inspiratory transdiaphragmatic (Delta Pdi‐insp) pressures were derived from the above.ResultsLaparoscopic cholecystectomy induced a significant reduction in mean Delta Pgas‐insp, mean Delta Pdi‐insp, and mean Vabdindicating a reduction of diaphragmatic activity postoperatively. Delta Pdi‐inspdecreased from 11.8 +/‐ 4.0 cm H2O preoperatively to 5.7 +/‐ 5.7 cm H2O at 1 h and 6.6 +/‐ 5.1 cm H2O at 6 h postoperatively (mean +/‐ SD; P < 0.05). Vabddecreased from 327.0 +/‐ 113.0 ml preoperatively to 174.0 +/‐ 65.0 ml at 1 h and 175.0 +/‐ 98.0 ml at 6 h postoperatively (mean +/‐ SD; P < 0.05). These values had partially recovered at 24 h.ConclusionThe direct and indirect indices of diaphragmatic activity taken together confirm the presence of reduction in diaphragmatic activity after laparoscopic cholecystectomy followed by its partial recovery at 24 h.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundFor the human brain, there are no data available concerning the significance of adenosine and its metabolites as biochemical indicators of cerebral ischemia. Since adenosine may counteract key pathogenetic mechanisms during cerebral ischemia, its sensitivity and specificity as a marker of cerebral ischemia was investigated in relation to hypoxanthine and lactate.MethodsArterial and jugular venous concentration changes of adenosine, hypoxanthine, and lactate were studied in 41 patients undergoing carotid endarterectomy. Cerebral tissue oxygenation was monitored continuously by somatosensory‐evoked potentials. A carotid artery shunt (n = 6) was placed only after complete loss of somatosensory‐evoked potentials.ResultsBefore carotid artery clamping jugular venous concentrations of adenosine, hypoxanthine, and lactate in subsequently shunted patients were 229 +/‐ 88 nM, 1105 +/‐ 116 nM, and 0.85 +/‐ 0.52 mM, respectively (mean +/‐ SD). In patients who required shunting, carotid artery clamping induced a significant increase in jugular venous adenosine (389 +/‐ 114 nM) and jugular venous hypoxanthine (1444 +/‐ 168 nM). In contrast, the increase in jugular venous lactate (0.91 +/‐ 0.48 mM) did not reach statistical significance. Focal cerebral ischemia was indicated by jugular venous adenosine with a sensitivity and specificity of 0.83 and 0.71, respectively.ConclusionsCarotid artery clamping induced significant increases in jugular venous adenosine and hypoxanthine in patients with inadequate collateral blood flow. In addition, focal cerebral ischemia was reflected by changes in adenosine concentrations.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThermoregulatory control is based on both skin and core temperatures. Skin temperature contributes [approximate] 20% to control of vasoconstriction and shivering in unanesthetized humans. However, this value has been used to arithmetically compensate for the cutaneous contribution to thermoregulatory control during anesthesia‐although there was little basis for assuming that the relation was unchanged by anesthesia. It even remains unknown whether the relation between skin and core temperatures remains linear during anesthesia. We therefore tested the hypothesis that mean skin temperature contributes [approximate] 20% to control of vasoconstriction and shivering, and that the contribution is linear during general anesthesia.MethodsEight healthy male volunteers each participated on 3 separate days. On each day, they were anesthetized with 0.6 minimum alveolar concentrations of isoflurane. They then were assigned in random order to a mean skin temperature of 29, 31.5, or 34 [degree sign]C. Their cores were subsequently cooled by central‐venous administration of fluid at [almost equal to] 3 [degree sign]C until vasoconstriction and shivering were detected. The relation between skin and core temperatures at the threshold for each response in each volunteer was determined by linear regression. The proportionality constant was then determined from the slope of this regression. These values were compared with those reported previously in similar but unanesthetized subjects.ResultsThere was a linear relation between mean skin and core temperatures at the vasoconstriction and shivering thresholds in each volunteer: r2= 0.98 +/‐ 0.02 for vasoconstriction, and 0.96 +/‐ 0.04 for shivering. The cutaneous contribution to thermoregulatory control, however, differed among the volunteers and was not necessarily the same for vasoconstriction and shivering in individual subjects. Overall, skin temperature contributed 21 +/‐ 8% to vasoconstriction, and 18 +/‐ 10% to shivering. These values did not differ significantly from those identified previously in unanesthetized volunteers: 20 +/‐ 6% and 19 +/‐ 8%, respectively.ConclusionsThe results in anesthetized volunteers were virtually identical to those reported previously in unanesthetized subjects. In both cases, the cutaneous contribution to control of vasoconstriction and shivering was linear and near 20%. These data indicate that a proportionality constant of [approximate] 20% can be used to compensate for experimentally induced skin‐temperature manipulations in anesthetized as well as unanesthetized subjects.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundAntifibrinolytic medications administered before skin incision decrease bleeding after cardiac surgery. Numerous case reports indicate thrombus formation with administration of [Greek small letter epsilon]‐aminocaproic acid ([Greek small letter epsilon]‐ACA). The purpose of this study was to examine the efficacy of [Greek small letter epsilon]‐ACA administered after heparinization but before cardiopulmonary bypass in reducing bleeding and transfusion requirements after primary coronary artery bypass surgery.MethodsSeventy‐four adult patients undergoing primary coronary artery bypass surgery were randomized to receive 125 mg/kg [Greek small letter epsilon]‐ACA followed by an infusion of 12.5 mg [middle dot] kg‐1[middle dot] h‐1or an equivalent volume of saline. Coagulation studies, thromboelastography, and platelet aggregation tests were performed preoperatively, after bypass, and on the first postoperative day. Mediastinal drainage was recorded during the 24 h after surgery. Homologous blood transfusion triggers were predefined and transfusion amounts were recorded.ResultsOne patient was excluded for surgical bleeding and five patients were excluded for transfusion against predefined criteria. One patient died from a dysrhythmia 2 h postoperatively. Among the remaining 67, the [Greek small letter epsilon]‐ACA group had less mediastinal blood loss during the 24 h after surgery, 529 +/‐ 241 ml versus 691 +/‐ 286 ml (mean +/‐ SD), P < 0.05, despite longer cardiopulmonary bypass times and lower platelet counts, P < 0.05. Platelet aggregation was reduced in both groups following cardiopulmonary bypass but did not differ between groups. Homologous blood transfusion was similar between both groups.ConclusionsProphylactic administration of [Greek small letter epsilon]‐ACA after heparinization but before cardiopulmonary bypass is of minimal benefit for reducing blood loss postoperatively in patients undergoing primary coronary artery bypass grafting.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundLow‐dose combined spinal‐epidural analgesia in labor has proved popular with women because lower‐limb motor power is preserved, allowing ambulation. However, there has been debate about the safety of allowing women to walk following low‐dose regional analgesia because of somato‐sensory impairment. The authors undertook a prospective controlled observational study using computerized dynamic posturography to examine balance function in pregnant women after combined spinal‐epidural analgesia.MethodsThe authors performed posturographic testing on 44 women in labor after institution of regional analgesia and compared them with a control group of 44 pregnant women. A separate group of six women were tested both before and after combined spinal‐epidural analgesia.ResultsNeurologic examination after regional analgesia showed two parturients (4%) to have motor weakness (excluded from posturography). Four women (9%) had clinical dorsal column sensory loss; these women all completed posturography. The spinal‐epidural analgesia group showed a small, statistically significant reduction in one of six posturographic sensory‐organization tests; however, this difference was functionally minor. There were no other differences in posturography between the control and spinal‐epidural groups. Similar results were found in the paired study, in which there was minimal change in balance function after spinal‐epidural analgesia.ConclusionsThis is the first study to objectively examine the effect of spinal‐epidural analgesia on balance function. Using computerized dynamic posturography, the authors were unable to find any functional impairment of balance function after spinal‐epidural ambulatory analgesia in women in labor who had no clinical evidence of motor block.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundPostoperative pain is a major problem in day‐case surgery in children. Nonsteroidal antiinflammatory drugs have gained popularity in management of pediatric surgical patients to reduce the need for opioids. The aim of this study was to evaluate the efficacy of different doses of rectal acetaminophen in day‐case surgery in children.MethodsA randomized, double‐blinded, placebo‐controlled study design was used. Patients (n = 120) were randomized to receive a single dose of 0, 20, 40, or 60 mg/kg of rectal acetaminophen after induction of anesthesia. General anesthesia was induced by mask ventilation with sevoflurane (7%) in nitrous oxide and oxygen and maintained with 2.5–4.0% end‐tidal sevoflurane. Opioids or local anesthetics were not used. Postoperative pain was evaluated by behavioral assessment and physiologic measurements every 10 min after arrival at the postanesthesia care unit. The pain intensity was scored using a 0–100 visual analog scale used in the author's clinic. The need for rescue medication, intravenous morphine 0.1 mg/kg, was decided by the nurse, who was unaware of the rectal acetaminophen dose. The parents were interviewed by phone after 24 h regarding pain and its treatment, nausea, and vomiting. Rescue analgesia at home was rectal ibuprofen, 10 mg/kg.ResultsIn the postanesthesia care unit pain scores were significantly lower in the 40‐ and 60‐mg/kg groups compared with placebo and 20‐mg/kg groups. Acetaminophen resulted in a dose‐related reduction in the number of children who required postoperative rescue opioid, with significance reached with 40 or 60 mg/kg doses. Calculated dose of acetaminophen at which 50% of the children not requiring a rescue opioid was 35 mg/kg. The need for rescue analgesia at home during the first 24 h after surgery was also significantly less in patients in the 40‐ or 60‐mg/kg groups than in the 0‐ or 20‐mg/kg groups (20–17 vs. 80–63%). Thirty‐three percent of patients receiving placebo had postoperative nausea and vomiting, compared with 0–3% in groups receiving 40 or 60 mg/kg acetaminophen.ConclusionsA single dose of 40 or 60 mg/kg of rectal acetaminophen has a clear morphine‐sparing effect in day‐case surgery in children if administered at the induction of anesthesia. Moreover, children with adequate analgesia with acetaminophen have less postoperative nausea and vomiting.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundAlthough systemic inflammation is believed to cause upregulation of nicotinic acetylcholine receptors (nAchRs) in muscle, chronic infections such as Chagas' disease occasionally are complicated by myasthenia gravis. The authors investigated how a nonlethal cecal ligation and puncture (CLP) peritonitis model in rats could affect muscle nAchR.MethodsOn day 1, 4, 7, 14, or 21 after CLP or sham operation, nAchR binding was assayed in the anterior tibial muscle and diaphragm using [(125) I] [Greek small letter alpha]‐bungarotoxin. The presence or absence of weakness, in vivo dose‐response relationships for d‐tubocurarine, and serum anti‐nAchR antibody titers were assayed in separate experiments.ResultsSystemic inflammation was most severe during the first 4 to 5 days. Numbers of nAchRs were decreased in anterior tibial muscle on days 7, 14, and 21 after CLP, and in the diaphragm on days 7 and 14 (P < 0.01). Both 50% and 90% blocking doses of d‐tubocurarine) were lower in CLP rats than in sham‐operated rats on days 7, 14, and 21 (P < .05). Weakness was overt in approximately half of CLP rats at these times. Serum anti‐nAchR antibody (0.7–1.4 nM) was detectable beginning on day 4 and continuing throughout the 21‐day observation period in 58–67% of CLP rats.ConclusionsDuring the recovery phase of injury, nonlethal CLP peritonitis resulted in downregulation of nAchR. However, further study is needed to determine the role of anti‐nAchR antibodies in the development of decreased receptor numbers and impaired neuromuscular function.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID