Haemodynamic effects of rectal methohexitone for induction of anaesthesia in children

Pulsed Doppler and two-dimensional echocardiography were used to determine the haemodynamic effects of rectal methohexitone in 12 children 32.4 +/- 3.8 months old and weighing 13.3 +/- 1.1 kg (mean +/- SEM). Heart rate, blood pressure and echocardiographic measurements of cardiac output, stroke volume and left ventricular end-diastolic and end-systolic volumes were obtained prior to the induction of anaesthesia. Anaesthesia was induced with 25 mg.kg-1 two per cent rectal methohexitone. Immediately following the onset of sleep all cardiovascular measurements were repeated. Following the induction of anaesthesia with rectal methohexitone there was a significant increase in heart rate. Blood pressure, cardiac index, stroke volume and ejection fraction were unchanged. It is concluded that rectal administration of two per cent methohexitone for the induction of anaesthesia in healthy paediatric patients has minimal haemodynamic effect.     

Acute device-based blood pressure reduction: electrical activation of the carotid baroreflex in patients undergoing elective carotid surgery

Carotid sinus baroreceptors are involved in controlling blood pressure (BP) by providing input to the cardiovascular regulatory centers of the medulla. The acute effect of temporarily placing an electrode on the carotid sinus wall to electrically activate the baroreflex was investigated. We studied 11 patients undergoing elective carotid surgery. Baseline BP was 146+30/66+/-17 mm Hg and heart rate (HR) 72+/-7 bpm (mean +/- standard deviation). An electrode was placed upon the carotid sinus and after obtaining a steady state baseline of BP and HR, an electric current was applied and increased in 1-volt increments. A voltage dependent and highly significant reduction in BP was observed which averaged 18+/-26* and 8.0+/-12 mm Hg for systolic BP and diastolic BP, respectively. Maximal reductions occurred at 4.4+/-1.2 V: 23+/-24 mm Hg*, 16+/-10 mm Hg* and 7+/-12 bpm* for systolic BP, diastolic BP and HR, respectively ( = p <.05). Thus, electrical stimulation of the carotid sinus activates the carotid baroreflex resulting in a reduction in BP and HR. This presents a proof of concept for device based baroreflex modulation in acute BP regulation and adds to the available data which provide a rationale for evaluating this system in the context of chronic BP reduction in hypertensive patients.     

Altered autonomic cardiovascular regulation after combined deep and superficial cervical plexus blockade for carotid endarterectomy

Compromised cardiac autonomic modulation can produce cardiovascular disturbances. We investigated whether combined deep and superficial cervical plexus (CP) blockade for carotid endarterectomy (CEA) produces changes in autonomic cardiovascular regulation. To estimate alterations in cardiovascular autonomic control before and after combined CP blockade in 22 patients undergoing CEA, the heart rate (HR) variability, systolic blood pressure (SBP) variability, and baroreflex sensitivity were analyzed. We found that SBP (157 +/- 28 mm Hg versus 191 +/- 38 mm Hg before and after combined CP blockade, respectively) and HR (68 +/- 10 bpm versus 84 +/- 9 bpm) increased after combined CP blockade. The high frequency power of HR variability (3.7 +/- 0.9 versus 2.2 +/- 1.2 ln/ms2) decreased (decrease in parasympathetic drive), whereas the low frequency power of SBP variability (5.5 +/- 4.7 versus 8.6 +/- 9.4 mm Hg2) increased (increase in vascular sympathetic outflow). Baroreflex sensitivity decreased, and this decrease was negatively correlated with a SBP increase (r = -0.455). The present results suggest that combined CP blockade impairs autonomic cardiovascular homeostasis and suggests an association between combined CP blockade and intraoperative or postoperative adverse cardiovascular events in high-risk cardiac patients undergoing CEA that merits further studies.     

Methohexital plasma concentrations in children following rectal administration

Despite the increasing use of rectal methohexital as a premedicant-induction agent in pediatric anesthesia, there are no data to confirm the assumption that low plasma methohexital concentrations are the cause of inadequate sedation of children and that high concentrations are associated with the loss of consciousness. Plasma methohexital concentrations were determined in 20 ASA Class I children, ages 2-7 yr, after the rectal administration of methohexital (25 mg/kg). Seventeen of the 20 children in this study fell asleep after receiving the drug and achieved peak plasma concentrations greater than 2 micrograms/ml. The maximum plasma methohexital concentration in children that did not fall asleep was less than 2 micrograms/ml. The mean time to the onset of sleep after drug administration was 8.3 min (at which time the mean plasma concentration was 4.4 micrograms/ml). The mean peak plasma concentration and the mean time to peak plasma concentration were 4.7 micrograms/ml and 13.9 min, respectively. Loss of consciousness after rectal administration of methohexital correlates well with the plasma concentration of the drug.     

Rectal methohexital: concentration and length of the rectal catheters

In the study, the authors evaluated the concentration of rectal methohexital (1% vs 10%) and the length of the rectal catheter (3.8 vs 12.7 cm), on sleep-success rate, administration-sleep time, methohexital plasma concentrations, and recovery time in 85 healthy children scheduled for elective ophthalmic or ear, nose, or throat operations lasting approximately 1 h. At a dose of 25 mg/kg, the 1% solution of rectal methohexital was associated with a significant (P less than 0.05) higher sleep-success rate (95% vs 70%), shorter administration-sleep time (5.7 +/- 1.9 vs 7.0 +/- 2.0 min), higher methohexital plasma concentrations at 20 min (6.5 vs 4.7 ng/mL) and at 30 min (5.3 vs 3.7 ng/mL), and prolonged recovery time (53.2 +/- 31.1 vs 32.4 +/- 18.5 min). The length of the rectal catheters did not significantly affect sleep-success rate, administration-sleep time, methohexital plasma concentrations, or recovery time. The use of 25 mg/kg of 1% rectal methohexital solution to induce anesthesia in children is superior to the use of 25 mg/kg of 10% methohexital solution for induction of anesthesia in children, particularly in operations 1 h or longer in duration.     

Cardiovascular effects of meperidine-N2O anesthesia before and after pancuronium

The cardiovascular effects of 2 and 3 mg/kg of meperidine plus 60 to 67% N2O in O2 on cardiovascular dynamics in man were measured before and after the administration of 0.08 mg/kg of IV pancuronium. N2O and 2 mg/kg of meperidine did not change heart rate (HR) but produced a marked reduction (-49%) in cardiac output (QT) plus significant decreases in stroke volume (SV) and blood pressure (BP) and an increase in peripheral arterial resistance (PVR). Additional meperidine did not further alter any of the variables; however, surgical stimulation caused significant increases in HR, BP, and PVR. SV and QT were not significantly changed by surgical stimulation and were still markedly depressed when compared to control values. Pancuronium produced marked increases in HR, SV, QT, and BP and a reduction in PVR. These changes were maximal 4 to 8 minutes after pancuronium and returned toward pre-pancuronium values thereafter. These data demonstrate that N2O-meperidine anesthesia results in a moderate reduction in BP but a marked depression in QT. The findings also indicate that pancuronium reverses the cardiovascular depression produced by N2O-meperidine and is therefore, a desirable muscle relaxant when the above technic is employed.     

Cardiovascular parameter changes in patients with erectile dysfunction using pde-5 inhibitors: a study with sildenafil and vardenafil

Sildenafil is the most prescribed oral agent for patients with erectile dysfunction (ED). Vardenafil is a new phosphodiesterase type 5 (Pde-5) inhibitor that was approved by the US Food and Drug Administration last year to treat patients with ED of various causes. Both of these Pde-5 inhibitors have vasodilating properties and effects on blood pressure (BP), and like nitrates, they work through the nitric oxide cyclic guanosine monophosphate pathway. The aim of this study was to investigate the influence of these Pde-5 inhibitors on BP and heart rate (HR) in normotensive men with ED by a crossover comparison. Thirty-five patients with ED were enrolled to evaluate and compare the effect of sildenafil (50 mg) and vardenafil (10 mg) on BP and HR. At the screening (baseline [B]) visit, sitting systolic blood pressure (B-SBP), diastolic blood pressure (B-DBP), and HR were measured. We performed a multiple administration for both drugs and, therefore, multiple measurements of BP and HR changes, 3 doses a week, on alternate days, late in the afternoon, and on an empty stomach. B-SBP, B-DBP, and HR were recorded before each 50-mg sildenafil dosing and after 30, 60, 120, and 240 minutes. Data were averaged over the 4 time points and compared with the baseline values obtained before each dosing. After a 3-week wash-out period, patients were crossed over to vardenafil (10 mg) with the same study design. After administration of both drugs, we observed a statistically significant decrease of BP and an increase of HR. On average, sildenafil caused a decrease of SBP ranging from 5.1 +/- 3.9 mm Hg during the first dosing to 4.7 +/- 4.2 mm Hg during the third dosing, DBP ranged from 4.4 +/- 4.9 to 4 +/- 4.1 mm Hg, and HR increased 1.8 +/- 2.0 bpm (first dose) and 1.2 +/- 0.9 bpm (third dose). With vardenafil, we recorded a greater variation for SBP and DBP. SBP decreased from 8.02 +/- 8.0 mm Hg during the first dosing to 5.4 +/- 5.5 mm Hg during the third dosing, whereas DBP decreased from 6.6 +/- 7.2 to 5.0 +/- 5.3 mm Hg, respectively. Recorded HR showed an increase of 3.1 +/- 3.2 bpm (first dose) and 2.4 +/- 2.3 bpm (third dose). After the first vardenafil administration, we recorded fainting episodes in 3 patients because of a decrease in BP greater than 20 mm Hg. Two of the patients were in therapy with doxazosin for benign prostatic hyperplasia (BPH). Cardiovascular response was not significantly different after the first dose between the 2 treatments. Vardenafil demonstrated clinically significant differences (fainting) with respect to sildenafil only during the first doses. We suggest that before starting therapies with Pde-5 inhibitors, particularly with the newer ones, that baseline cardiovascular parameters are measured and monitored, especially during the first dose, because of the presence of a "first dose effect." Moreover, it is necessary to pay particular attention to those patients in treatment with other drugs that could have a synergistic hypotensive effect as a result of vasodilation potentiation.     

无创心输出量监测在心力衰竭患者循环支持时的应用

背景尽管肺动脉导管（PAC）热稀释法的有效性、安全性均存在问题且使用困难，然而该方法目前在围手术期心外科重症监护室中仍普遍被应用于对中心血流动力学的监测和管理。超声心输出量监测仪（USCOM）是一种无创性连续多普勒装置，用于直接测量心输出量（CO），可替代PAC。虽然USCOM的可靠性存在一些公认的局限性，但已证实该方法比PAC在心外科重症监护室更具主导地位。我们比较了心力衰竭（HF）患者在应用一种原位全人工心脏（TAH）控制治疗期间，USCOM与CardioWest的心输出量测量结果。方法选择安装全人工心脏的心力衰竭（TAHHF）患者，按照盲法使用CardioWest和USCOM设备监测患者心输出量（CO）、每搏心输出量（SV）和心率（HR）。根据CardioWest所控制流量的不同，监测7例患者18个不同时点，获得了508对测量结果。用Bland—Altman分析法比较一致性。结果使用CardioWest和USCOM设备测得患者的心输出量、每搏心输出量和心率的平均值和标准差（±标准差）分别是7．33±0．46和7．34±0．51L/min、56．2±3．8和56．6±3．8ml，以及131±3和130±4bpm。心输出量的范围为5．2，9．3L／min。两种方法检测的心输出量、每搏心输出量和心率的平均差值分别是-0．01±0．23L／min、-0．34±1．97ml和0．9±2．3bpm，平均百分比差为一0．3％、-0．6％和0．7％。心输出量、每搏心输出量和心率一致性的百分比范围分别为6．4％、7．1％和3．6％。结论USCOM对于安装全人工心脏的心力衰竭患者的心输出量无创性监测和管理不失为一个可行且准确的方法，其可能在心血管疾病的诊断和治疗中有更广泛的应用。     

Assessment of autonomic cardiovascular changes associated with recovery from anaesthesia in children: a study using spectral analysis of blood pressure and heart rate variability

Recovery from anaesthesia is associated with large changes in cardiovascular autonomic activity, which are poorly documented in children. This study was undertaken to investigate the cardiovascular autonomic activity in anaesthetized and recovering children, using a noninvasive approach based on spectral analysis of heart rate (HR) and blood pressure (BP) variability. Ten children (aged 5-13 years) undergoing major surgery were studied. Continuous HR and BP were recorded using a noninvasive device during deep anaesthesia and recovery. Spectral analysis was used to determine the main oscillatory components of HR and BP signals. For each power spectrum, the frequency components were identified as follows (i): the low frequency (LF) component (0.04-0.14 Hz) both parasympathetically and sympathetically mediated for HR and corresponding to vasomotor sympathetic modulation for BP; and (ii) the high frequency (HF) component (0.2-0.6 Hz) parasympathetically mediated for HR, and reflecting mechanical influence of ventilation on cardiac output for BP. In addition, the LF : HF ratio for HR, reflecting the cardiac sympathovagal balance, was calculated. Under deep anaesthesia, HR variability and BP variability were very low and mainly due to mechanical influence of intermittent positive pressure ventilation. Conversely, the recovery period was associated with a marked increase of HR and BP overall variability. Compared to anaesthesia, spectral analysis of HR and BP revealed that the LF component of BP and HR spectra increased 40-fold during recovery; the LF : HF ratio of HR was also increased during recovery (0.1 +/- 0.1 versus 1.3 +/- 1.2, P=0.008). The results of this study demonstrate that the recovery period is associated with an increase of cardiovascular sympathetic drive in children after major surgery.     

Anaesthesia for morbidly obese patients: a study of haemodynamic changes during bariatric surgery

BACKGROUND AND AIMS: Morbid obesity with body mass index (BMI) > 40 kg/m2 requires surgical correction if the diet program fails. Laparoscopic adjustable gastric banding (LAGB) (bariatric surgery) is the standard surgical procedure. The haemodynamic effects of the typical pneumoperitoneum had been studied but, the additional effects of morbid obesity and the consequences of LAGB surgery had not. Therefore, we conducted this study to determine the haemodynamic changes under anaesthesia during bariatric surgery. MATERIALS AND METHODS: Under general anaesthesia, 7 patients (4 males) were studied. Their mean age was 36.2 yr (range 25-50 yr) and mean BMI was 49.7 kg/m2 (range 39.3-67.3). Besides routine monitoring of vital signs, non invasive cardiac output monitor (NICO, Novametrix, Wallingford, CT, USA) was used to monitor cardiac output (CO), cardiac index (CI) and stroke volume (SV). All the haemodynamic variables were taken at three phases: A) after induction of anaesthesia, B) during pneumoperitoneum and C) after gas deflation. RESULTS: The mean HR and BP showed significant high values during phase B compared to phase A. The mean values of CO were 7.2 +/- 1.1 and 9.06 +/- 2.6 L/min during phases A and B respectively with significant differences. The mean values of SV were 91.1 +/- 12.3 and 123.2 +/- 42.6 ml during phases A and B respectively with significant differences. The mean values of CI during phases A and B were 3.1 +/- 0.7 and 3.4 +/- 1.09 L/min/m2 respectively with significant differences. CONCLUSIONS: We have reported high CO and CI during pneumoperitoneum, which may be due to increased heart rate induced by sympathetic stimulation.     

Exercise assessment in infants after cardiac transplantation

BACKGROUND: Few data describe exercise performance after cardiac transplantation during infancy. The aim of this study was to compare the cardiorespiratory response to exercise in healthy subjects with that of subjects who had undergone heart transplantation during infancy to treat hypoplastic left heart syndrome. METHODS: Subjects (24 heart transplant recipients and 25 healthy controls) exercised on a treadmill using pediatric ramp protocols. We measured heart rate (HR), blood pressure, and metabolic data. Median age at transplantation was 20 days (range, 4 to 97 days). Age of recipients at exercise testing was 9.7 +/- 2.3 years and in healthy subjects was 10.5 +/- 1.4 years (p=not significant [NS]). RESULTS: Exercise duration was similar in both groups (10.3 +/- 2.0 minutes in recipients vs 11.1 +/- 1.5 minutes in healthy subjects, (p=NS). Heart rate at rest was greater in recipients (94 +/- 15 beats per minute [bpm] vs 85 +/- 11 bpm, p=0.02). Peak HR also was less in the recipient group (158 +/- 15 bpm vs 189 +/- 12 bpm, p <0.001). Peak oxygen consumption was 14% less in the recipients (32.3 +/- 5.6 ml/kg/min vs 36.8 +/- 5.5 ml/kg/min, p <0.01). Ventilatory anaerobic threshold was decreased in recipients, 27.6 +/- 9.6 vs 32.8 +/- 6.0, p <0.05. Respiratory exchange ratio at peak exercise was equal in both groups (1.06 +/- 0.06 vs 1.06 +/- 0.08). Oxygen pulse index did not differ significantly, 5.5 +/- 1.1 ml/beat/m2 in recipients and 6.1 +/- 1.7 ml/beat/m2 in healthy subjects (p=NS). CONCLUSIONS: Overall, children who undergo cardiac transplantation in infancy have exercise capacities within the normal range. These recipients have a decreased heart rate reserve that may account for the differences in peak oxygen consumption when compared with healthy subjects.     

Effect of 2 liters of intraperitoneal dialysate on the cardiovascular system

In 21 patients receiving continuous ambulatory peritoneal dialysis (CAPD), the effect of 2 liters of intraperitoneal dialysate on the supine and upright hemodynamics (19 patients), and the hemodynamic responses to 45 degrees head-up tilt (9 patients) were studied. Blood pressure (BP), heart rate (HR) and stroke volume (SV) (using impedance cardiography) were measured. In the supine position there was no significant difference in BP, SV, HR, derived cardiac output (CO) and peripheral resistance (PR) between "empty" (E) and "full" (F) conditions. On standing in both E and F conditions there were significant falls in systolic BP (p less than 0.001, compared with supine), SV and CO (p less than 0.05) accompanied by an increase in HR (p less than 0.001) but no significant change in peripheral resistance nor diastolic BP. The fall in systolic BP was greater in the E condition (from 149.3 +/- 4.5 mmHg to 134.6 +/- 5.9 in E, from 148.8 +/- 4 mmHg to 140.8 +/- 5.0 in F, p less than 0.001) and was accompanied by a bigger rise in HR (from 80.2 +/- 4.3 beat/min to 91.8 +/- 5.3 (E), from 79.4 +/- 4.4 to 87.7 +/- 5.2 (F, p less than 0.001). On tilting in 13 normal subjects there was an increase in diastolic BP (76.7 +/- 2.0 mmHg to 81.4 +/- 0.6, p less than 0.01), HR (63.3 +/- 2.4 beat/min to 73.6 +/- 1.0, p less than 0.01) and PR (13.4 +/- 1.0 mmHg/l/min to 21.3 +/- 0.2, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of the cardiovascular responses to fiberoptic orotracheal intubation with television monitoring: comparison with conventional direct laryngoscopy

STUDY OBJECTIVE: To evaluate and compare cardiovascular responses to a new method of orotracheal intubation incorporating TV monitoring, with conventional orotracheal intubation via rigid blade laryngoscopy. DESIGN: Prospective single-blind study. SETTING: Operating room of a medical college hospital. PATIENTS: 90 ASA physical status I and II surgical patients requiring general anesthesia and orotracheal intubation. INTERVENTIONS: Patients were randomly allocated to two groups, one for the new intubation method and the other for conventional intubation using a rigid laryngoscope. In the new method, an anesthesiologist inserted an endotracheal tube alone into the trachea via TV monitoring through the bronchoscope, which was inserted by an assistant through the mouth to the middle larynx. The patient's trachea was intubated without extreme stretching of laryngeal tissues or deep insertion of the tip of the bronchoscope. In the conventional method, orotracheal intubation was performed with rigid direct laryngoscopy. MEASUREMENTS: Noninvasive blood pressure (BP) and heart rate (HR) were measured before arrival at the operating room, and before and after orotracheal intubation.Main Results: Although this method was expected to be a minimally invasive fiberoptic intubation technique, the patients showed significant increases in BP and HR. No significant differences between the two groups were observed in cardiovascular responses immediately after intubation: the systolic BP, 169.5 +/- 28.3 versus 167.0 +/- 23.1 mmHg, and HR, 100.2 +/- 18.2 versus 98.8 +/- 16.6 bpm. CONCLUSIONS: Insertion of an endotracheal tube may itself be the most invasive stimulus during intubation procedures.     

Acute left ventricular dysfunction during unsuccessful weaning from mechanical ventilation

The authors studied the hemodynamic effects of rapidly weaning from mechanical ventilation (MV) 15 patients with severe chronic obstructive pulmonary disease (COPD) and cardiovascular disease who were recovering from acute cardiopulmonary decompensation. In each patient, 10 min of spontaneous ventilation (SV) with supplemental oxygen resulted in reducing the mean esophageal pressure (X +/- SD, + 5 +/- 3 to -2 +/- 2.5 mmHg, P less than .01) and increasing cardiac index (CI) 3.2 +/- 0.9 to 4.3 +/- 1.3 1/min/M2, P less than .001), systemic blood pressure (BP 77 +/- 12 to 90 +/- 11 mmHg, P less than .001), heart rate (HR 97 +/- 12 to 112 +/- 16 beats/min, P less than .001), and, most importantly, transmural pulmonary artery occlusion pressure markedly increased (PAOPtm 8 +/- 5 to 25 +/- 13 mmHg, P less than .001), mandating a reinstitution of MV. In four patients with left ventricular (LV) catheters, the PAOP correlated with the LV end-diastolic pressure during both MV and SV. Gated blood pool imaging showed SV increased the LV end-diastolic volume index (65 +/- 24 to 83 +/- 32/M2, P less than .002) with LV ejection fraction unchanged. Patients were treated for a mean of 10 days with diuretics, resulting in a reduction of blood volume (4.55 +/- 0.9 1 to 3.56 +/- 0.55 1) and body weight (-5 kg, P less than .001). Subsequently, nine of the 15 patients were weaned successfully from mechanical ventilation with unchanged PAOP.     

The effect of maternal cocaine exposure on neonatal rat cardiac function

Fetal cocaine exposure has been associated with a variety of cardiovascular dysfunctions in humans. We treated pregnant rats with either saline or cocaine at 60 mg/kg by gastric lavage for the entire gestational period and for 14 days after parturition. We then performed high-frequency transthoracic echocardiography to determine whether cocaine exposure affected neonatal cardiac contractile function in vivo in 7- and 14-day-old neonatal rats. All studies were performed in the unsedated, conscious state. Heart rate (HR) and systolic function, expressed as fractional area of change at the midpapillary muscle level, were calculated from two-dimensional images. Resting HR was faster in the cocaine-exposed group at both ages, but baseline contractile function was not different between control (CTL) and cocaine-exposed (COC) neonatal rats. Dobutamine induced a significant increase in HR in all groups at only the largest dose tested (Day 7 CTL HR increased from 438 +/- 3 bpm to 462 +/- 10 bpm; Day 7 COC HR increased from 466 +/- 3 bpm to 493 +/- 7 bpm; Day 14 CTL HR increased from 443 +/- 4 bpm to 487 +/- 4 bpm; Day 14 COC HR increased from 477 +/- 4 bpm to 501 +/- 5 bpm). Dobutamine elicited a significant increase in contractile response at both Day 7 (from 76.6% +/- 0.6% to 81.5% +/- 0.7%) and Day 14 in CTL (from 78.2% +/- 0.7% to 81.9% +/- 0.7%), but not in COC, animals (from 76.7% +/- 0.8% to 78.9% +/- 0.8% at Day 7 and from 76.8% +/- 1.1% to 79.3% +/- 0.8% at Day 14). Epinephrine induced a significant increase in contractile response in CTL, but not in COC, rats at Day 7 and had no effect on fractional area of change at 14 days of age in either CTL or COC animals. Our results indicate that perinatal cocaine exposure does not modify resting contractile function but attenuates the contractile response to beta-adrenoceptor stimulation in the neonatal rat. These results suggest that perinatal cocaine exposure may lead to decreased responsiveness to inotropic drugs during the early neonatal period.     

复合异丙酚时不同靶浓度瑞芬太尼对神经外科手术患者脑电双频谱指数的影响

目的 探讨复合异丙酚时不同效应室靶浓度瑞芬太尼对神经外科手术患者脑电双频谱指数(BIS)的影响.方法 择期拟行额颞部开颅手术患者15例,年龄18～64岁,体重50～85 kg,ASA Ⅰ或Ⅱ级.先靶控输注异丙酚,效应室靶浓度为3μg/ml,效应室浓度达预设浓度后靶控输注瑞芬太尼,效应室靶浓度分别为2、3、4、5、6、7、8 ng/ml,效应室浓度依次达预设浓度时记录血压(BP)、平均动脉压(MAP)、心率(HR)和BIS.瑞芬太尼效应室浓度达5 ng/ml时行气管插管和机械通气,于气管插管前即刻和气管插管后即刻记录BP、MAP、HR和BIS.结果 与基础值比较,异丙酚效应室浓度3μG/ml 和瑞芬太尼不同效应室浓度时BIS降低(P<0.05或0.01);与异丙酚效应室浓度3μg/ml时比较,瑞芬太尼效应室浓度≥6 nG/Ml时BIS降低(P<0.05或0.01).结论 复合异丙酚时靶控输注瑞芬太尼效应室浓度≥6 ng/ml时可降低神经外科手术患者的BIS.     

Effects of thoracic epidural anaesthesia on central haemodynamics compared to cardiac beta adrenoceptor blockade in conscious rats with acute myocardial infarction

The study aimed to compare the effects of thoracic epidural anaesthesia (TEA) with those of the beta-adrenoceptor blocker, metoprolol, on central haemodynamics in conscious rats with acute myocardial infarction. During methohexital anaesthesia, appropriate vascular catheters were inserted, a thoracic epidural catheter was implanted and the left coronary artery was ligated. A recovery period of 1-2 h elapsed after termination of surgery and anaesthesia. Experiments were performed on four separate groups of animals (A-D). In Group A (n = 10) mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO) were measured, and stroke volume (SV) and systemic vascular resistance (SVR) were calculated before and 10-15 min after the induction of TEA (bupivacaine 5 mg.ml-1). In Group B (n = 6) left ventricular end-diastolic pressure (LVEDP) and maximal dP/dt were recorded as in Group A. In Group C (n = 10) central haemodynamics were measured 10 min after i.v. metoprolol (0.5 mg.kg-1) and again 10-15 min after the addition of TEA. In Group D (n = 6) LVEDP and max dP/dt were measured as in Group C. The reduction in CO, SV, HR and max dP/dt was of the same magnitude with TEA and metoprolol. TEA lowered MAP by 17%, while metoprolol did not change MAP. Metoprolol caused an increase in LVEDP from 20.8 +/- 1.8 to 27.5 +/- 2.7 mmHg (2.8 +/- 0.2 to 3.7 +/- 0.4 kPa) (P less than 0.01), while TEA induced a decrease in LVEDP from 24.2 +/- 1.4 to 17.8 +/- 1.6 mmHg (3.2 +/- 0.2 to 2.4 +/- 0.2 kPa) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Heart rate and pulse pressure at rest are major prognostic markers of early postoperative complications after coronary bypass surgery

OBJECTIVE: There is substantial evidence to consider both heart rate (HR) at rest and pulse pressure (PP) as significant markers of cardiovascular prognosis in the general population. Despite this, neither of these two parameters has been taken into consideration in the design of modern coronary artery bypass risk prediction scores, and little data on their early postoperative prognostic value are currently available. We aimed to assess the predictive value of preoperative HR and PP in the 30-day postoperative period. METHODS: We prospectively enrolled all patients referred to our institution for non-urgent coronary artery bypass grafting. We measured HR on ECG at admittance. Preoperative pulse pressure was obtained by the difference of the mean of three consecutive systolic and diastolic blood pressures. The primary outcome combined the 30-day postoperative mortality, myocardial infarction (new Q-waves on ECG or Troponin-I >20 microg/l) and stroke or transient ischemic attack. The secondary outcome corresponded to clinical events only (stroke or death). Statistical analysis was performed by usual methods. RESULTS: We enrolled 1022 patients (age 66.9+/-9.2 years). Those meeting the primary outcome (n=146) had a significantly higher HR (69.9+/-14.3 bpm vs 64.9+/-13.2 bpm, p<0.0001) and a higher proportion presented a PP >70 mmHg (17.1% vs 10.2%, p<0.03). After adjustments for age, gender, systolic blood pressure, preoperative beta-blocker therapy, left ventricular ejection fraction <0.40, unstable cardiac status, redo surgery, peripheral arterial disease, renal failure, and combined vascular surgery, both HR (OR=1.17 per 10 bpm, p<0.03) and PP >70 mmHg (OR=1.99, p=0.03) remained significant risk predictors. Similar results were found when considering only clinical events. CONCLUSION: This prospective study highlights the usefulness of HR and PP as preoperative risk markers in CABG candidates.     

Effect of halothane on regional cerebral blood flow and cerebral metabolic oxygen consumption in the fetal lamb in utero

The effects of halothane on maternal and fetal hemodynamics, distribution of fetal cardiac output, regional cerebral blood flow, and fetal cerebral oxygen consumption were studied in the ewe (N = 9) using radionuclide-labeled microspheres. An adjustable uterine artery occluder was used to produce a controlled state of fetal asphyxia. Measurements were taken during three periods of study: 1) control, 2) asphyxia, and 3) asphyxia plus 15 min of 1% maternal halothane. The fetal cardiovascular response to asphyxia was acidosis, hypoxia, hypertension, bradycardia, and preservation of vital organ blood flows. There was a significant drop in maternal blood pressure when halothane was administered but uterine blood flow was maintained, 308 ml X min-1 during asphyxia versus 275 ml X min-1 with halothane. Fetal blood pressure during asphyxia plus halothane (54 mmHg) was significantly lower than that during asphyxia alone (59 mmHg), while heart rate was significantly higher: 172 beats per minute (bpm) versus 125 bpm (P less than 0.05). Despite these changes, the administration of halothane during asphyxia did not produce a reduction in vital organ flows. Cerebral blood flow was maintained: 357 +/- 37 ml X 100 g-1 X min-1 during asphyxia alone and 344 +/- 26 ml X 100 g-1 X min-1 after halothane administration (P = NS, mean +/- SEM). Cerebral oxygen delivery also was maintained: 8.3 +/- 0.8 ml X 100 g-1 X min-1 during asphyxia alone versus 9.7 +/- 1.5 ml X 100 g-1 X min-1 after halothane, compared with 11.2 +/- 1.1 ml X 100 g-1 X min-1 during the control period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiopulmonary effects of an anterior mediastinal mass in dogs anesthetized with halothane

The authors evaluated the cardiac effects of an anterior mediastinal mass to better understand the acute cardiovascular collapse that has been associated with anesthesia and positive-pressure ventilation. An 800-ml-capacity intravenous bag was placed within the anterior mediastinum of 12 dogs to simulate a mediastinal mass. After mediastinal mass inflation, the authors measured cardiac index (CI) during periods of spontaneous ventilation (SV), SV with added continuous positive airway pressure (CPAP), intermittent positive-pressure ventilation (IPPV), and continuous positive-pressure ventilation (CPPV). Similar mediastinal mass volumes resulted in similar decreases in CI during SV (169 +/- 51 to 105 +/- 10 ml.kg-1.min-1); CPAP (175 +/- 48 to 122 +/- 34 ml.kg-1.min-1); IPPV (151 +/- 15 to 93 +/- 24 ml.kg-1.min-1); and CPPV (183 +/- 56 to 117 +/- 46 ml.kg-1.min-1). The authors also found, by linear regression, that the relationship between CI and mass volume was similar during both SV and IPPV. In six dogs, transesophageal echocardiography (TEE) was used to measure ventricular short axis dimensions. The authors found that mass inflation caused left ventricular end-diastolic dimension to decrease significantly by 6 +/- 2 mm and 4 +/- 1 mm during SV or IPPV, respectively, and right ventricle dimensions to increase by 2 +/- 1 mm and 3 +/- 1 mm during SV or IPPV, respectively. The changes in chamber dimensions were similar with either SV or IPPV. These results suggest that the decrease in CI associated with a mediastinal mass results from an increase in right ventricular afterload, causing right ventricular enlargement. Subsequently, there is impingement on the left ventricle volume because of interventricular interdependence.