Passive Leg Elevation Research Articles

Stretch-induced compliance mechanism in pregnancy-induced cardiac hypertrophy and the impact of cardiovascular risk factors.

Pressure overload-induced hypertrophy compromises cardiac stretch-induced compliance (SIC) after acute volume overload (AVO). We hypothesized that SIC could be enhanced by physiological hypertrophy induced by pregnancy's chronic volume overload. This study evaluated SIC-cardiac adaptation in pregnant women with or without cardiovascular risk (CVR) factors. Thirty-seven women (1st trimester, 1stT) and a separate group of 31 (3rd trimester, 3rdT) women [healthy or with CVR factors (obesity and/or hypertension and/or with gestational diabetes)] underwent echocardiography determination of left ventricular end-diastolic volume (LVEDV) and E/e' before (T0), immediately after (T1), and 15 min after (T2; SIC) AVO induced by passive leg elevation. Blood samples for NT-proBNP quantification were collected before and after the AVO. Acute leg elevation significantly increased inferior vena cava diameter and stroke volume from T0 to T1 in both 1stT and 3rdT, confirming AVO. LVEDV and E/e' also increased immediately after AVO (T1) in both 1stT and 3rdT. SIC adaptation (T2, 15 min after AVO) significantly decreased E/e' in both trimesters, with additional expansion of LVEDV only in the 1stT. NT-pro-BNP increased slightly after AVO but only in the 1stT. CVR factors, but not parity or age, significantly impacted SIC cardiac adaptation. A distinct functional response to SIC was observed between 1stT and 3rdT, which was influenced by CVR factors. The LV of 3rdT pregnant women was hypertrophied, showing a structural limitation to dilate with AVO, whereas the lower LV filling pressure values suggest increased diastolic compliance.NEW & NOTEWORTHY The sudden increase of volume overload triggers an acute myocardial stretch characterized by an immediate rise in contractility by the Frank-Starling mechanism, followed by a progressive increase known as the slow force response. The present study is the first to characterize echocardiographically the stretch-induced compliance (SIC) mechanism in the context of physiological hypertrophy induced by pregnancy. A distinct functional adaptation to SIC was observed between first and third trimesters, which was influenced by cardiovascular risk factors.

Analgesic Efficacy of Ultrasound-guided Fascia Iliaca Block and Three-in-one Block in Elderly Patients Undergoing Hip Surgeries: A Randomised Double-blinded Clinical Trial

Introduction: Hip surgery is a common surgical procedure in the elderly population, leading to significant pain. Ultrasound (USG) guided regional nerve blocks are a newer, safe, and effective postoperative pain control modality for elderly patients. Aim: To compare the analgesic efficacy of Fascia Iliaca Compartment Block (FICB) with the three-in-one block for postoperative analgesia in elderly patients after lower limb orthopaedic surgeries. Materials and Methods: It was a randomised double- blinded study performed at Uttar Pradesh University of Medical Sciences, Saifai, Etawah, Uttar Pradesh, India on 60 elderly patients of Americian Soceity of Anaesthesiologists (ASA) class I-II scheduled for elective hip and femur shaft surgery under spinal anaesthesia.All patients were randomly allocated into two groups. Group A received ultrasound-guided FICB with 35-40 mL of 0.25% bupivacaine, and group B received ultrasound-guided three-in-one block with 35-40 mL of 0.25% bupivacaine after completion of surgery. In the postoperative period, pain was assessed using the Visual Analogue Scale (VAS), and inj. diclofenac sodium 1.5 mg/kg intravenous (i.v.) was given as rescue analgesic whenever VAS was ≥4. The primary outcome was changes in VAS scores at rest and during passive leg elevation between the two groups at various time intervals within 24 hours. Secondary outcomes measured were the duration of analgesia and total rescue analgesic required in 24 hours. Qualitative variables were compared between groups using the Chi-square test. A p-value<0.05 was considered statistically significant. Results: Demographic data were comparable in both groups, with a mean age of 65.11±1.89 years in Group A and 65.57±1.46 years in Group B. The VAS score at rest was significantly lower in Group A compared to Group B at the 6th hour (1.21±1.17 vs. 1.61±0.78) and 12th hour (2.80±0.12 vs. 3.33±0.92), respectively. The VAS score during passive movement was significantly lower in Group A at the 6th hour and 12th hour compared to Group B. The mean time for the first demand of rescue analgesic was 9.27±2.16 hours in the Fascia Iliaca Compartment Block (FICB) group and 6.67±1.45 hours in the three-in-one group. The difference was significant, with a p-value of 0.006. The mean requirement of total rescue analgesia was 133.33±33.27 mg in Group A and 198.53±29.16 mg in Group B, which was statistically significant. Conclusion: The fascia iliaca block had lower pain scores both at rest and during passive movement compared to the three-inone block. Total analgesic requirement was lower in the fascia iliaca group compared to the three-in-one block group.

Load-dependence of myocardial deformation variables - a clinical strain-echocardiographic study.

The effects of left ventricular (LV) loading on myocardial deformation variables are not well-studied in the clinical setting. In the present study, we evaluated the effects of isolated changes in preload, afterload and heart rate on LV longitudinal strain, systolic (SR-S) and early diastolic strain rate (SR-E) in post-cardiac surgery patients. Twenty-one patients were studied early after cardiac surgery. Longitudinal myocardial strain and SR were analysed off-line using 2-D speckle echocardiography. The experimental protocol consisted of three consecutive interventions: (1) preload was increased by passive leg elevation, (2) afterload was increased by an infusion of phenylephrine to increase arterial blood pressure by 10-15% and (3) heart rate was increased 10% and 20% by atrial pacing. During both the preload and afterload challenges heart rate was kept constant by atrial pacing. Central venous pressure was kept constant during pacing by infusion of hetastarch/albumin. The increase in preload increased LV strain, SR-S and SR-E by 20%, 11% and 17%, respectively. The phenylephrine-induced increase in afterload, did not affect LV strain, SR-S or SR-E. LV strain was not affected while SR-S and SR-E increased by pacing-induced heart rate increase. After cardiac surgery, systolic and early diastolic strain rate are dependent on both preload and heart rate, while neither of these variables was afterload-dependent. LV strain was preload-dependent but not affected by atrial pacing. When evaluating the direct effects of various pharmacological or other interventions on myocardial contractility and relaxation, preload and heart rate must be controlled.

The Effect of Passive Leg Elevation and/or Trendelenburg Position on the Cross-sectional Area of the Internal Jugular Vein in Infants and Young Children Undergoing Surgery for Congenital Heart Disease

Kim, Won Ho; Lee, Jong Hwan; Lee, Sangmin M.; Kim, Chung Su; Kang, Ryunga; Yoo, Chan Seon; Cho, Hyun Sung Author Information

CONTRIBUTION OF TRANSCUTANEOUS OXYMETRY IN DIABETIC FOOT SYNDROME

Four major complications are participating in tissue damage in diabetic foot syndrome – diabetic angiopathy, neuropathy, osteoarthropathy and inflammation. Low ankle-brachial pressure index (ABI) is a well-known indicator for ischemia of lower limbs, but in patients with diabetes mellitus is common also a high ABI (over 1.3) as reliable predictor of the presence of arterial calcification – medial calcinosis. Aim of the study is to determine the degree of ischemia using transcutaneous oximetry in patients with diabetic foot syndrome - with clinical manifestations of peripheral arterial occlusive disease (PAOD) and medial calcinosis. We investigated three groups: first consisted of 46 members in IInd stage of PAOD according to Fontaine classification, in second group were 30 members in IIIrd stage of PAOD and third had 29 members in IVth stage of PAOD. The ABI was determined with Doppler ultrasound examination. Transcutaneous oxygen tension (TcPO2) was measured with Oxykapnomonitor Hellige SMK Germany equipment with sensing probe – transoxode. Resting values of TcPO2 were obtained in lying patient on the foot in first metatarsal space. Subsequently leg was passively elevated into 30 degree angle for 3 minutes and then reimposed into primary position. One minute exercise – plantar and dorsal feet flexion was performed and after the TcPO2 values stabilization the patient hung his shin from the edge of the bed touching the floor. TcPO2 values were continuously recorded by analog waveform. In more severe stages of PAOD according to Fontaine stage III and IV we detected lower levels of TcPO2 under basal resting conditions: 20 respectively 5 mmHg. Patients with IInd stage of PAOD had basal TcPO2 values of 40 mmHg. Conclusions of the study are: TcPO2 values are not affected by the presence of medial calcinosis and sothis method is particularly beneficial in patients where Doppler ultrasound examination shows artificial high pressure values on lower limbs. In the third and fourth stage of PAOD passive leg elevation is as effective in determination of ischemia as working test.

The Effect of Passive Leg Elevation and/or Trendelenburg Position on the Cross-Sectional Area of the Internal Jugular Vein in Infants and Young Children Undergoing Surgery for Congenital Heart Disease

In this study we evaluated the effect of passive leg elevation (LE) and Trendelenburg (T) position on the cross-sectional area (CSA) of the internal jugular vein (IJV) in infants and young children undergoing surgery for congenital heart disease. A secondary aim was to compare the CSA of the IJV between subjects with right-to-left (RL) shunt and left-to-right (LR) shunt. Ninety infants and small children from 10 days to 31 months old weighing from 1.5 to 9.7 kg were assigned to group RL (n = 48) or LR (n = 42). In both groups, the CSA, transverse, and vertical diameters of the IJV on both sides of the neck were measured using a 2-dimensional ultrasound transducer in the following positions: supine position, 15° of T position, supine position with 50° of LE, and 15° of Trendelenburg position with 50° of LE (TLE). A more than 25% increase in mean CSA of the IJV was considered clinically significant. In group LR, T, LE, and TLE significantly increased CSA of both right (at least 12.3%, 10.3%, and 18.3%, respectively, "at least" refers to the lower 95% confidence limits) and left (at least 15.8%, 15.0%, and 18.9%, respectively) IJVs, whereas only TLE increased the CSA of both IJVs significantly in group RL (at least 8.2% and 7.7% in the right and left, respectively). The increase in the CSA of the right IJV related to T and TLE was larger in group LR than in group RL (at least 12.3% vs 1.2% for T and at least 18.3% vs 8.2% for TLE, respectively). A clinically significant increase in CSA was achieved in both right and left IJVs with TLE in group LR (mean 28.6% and 26.3%, respectively). The CSA of the right IJV was larger than that of the left IJV in most (at least 69.2%) patients. Passive LE was as effective as T position to increase the CSA of the IJV, but there was no clinically significant increase in the CSA with any single maneuver. Only T position with passive LE achieved a clinically significant increase in the CSA of both IJVs in infants and young children with LR shunt, but not in the same age group with RL shunt.

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Effect of increased preload on the synthesized aortic blood pressure waveform

In the present study, we examined the influence of preload augmentation via passive leg elevation (PLE) on synthesized aortic blood pressure, aortic augmentation index (AIx), and aortic capacitance (a reflection of aortic reservoir function). Central and peripheral hemodynamics were measured via tonometry with a generalized transfer function in 14 young, healthy men (age = 24 yr). Aortic blood flow was calculated from the left ventricular outflow tract (LVOT) velocity-time integral (VTI) using standard two-dimensional echocardiographic-Doppler techniques. Measures were made in the supine position at rest (Pre), during PLE, and during recovery (Post). There was a significant increase in LVOT-VTI, synthesized aortic systolic blood pressure (BP) and AIx from Pre to PLE, with values returning to baseline Post (P < 0.05). There was a reduction in aortic capacitance from Pre to PLE, with values returning to baseline Post (P < 0.05). There was no change in heart rate, systemic arterial compliance, aortic elastance, aortic wave travel timing, or vascular resistance (P > 0.05). Change in AIx from Pre to PLE was associated with change in LVOT-VTI (r = 0.66, P < 0.05) and inversely associated with change in aortic capacitance (r = -0.73, P < 0.05). These data suggest that in a setting of isolated augmented preload with minimal changes in other potential confounders, the morphology of the synthesized aortic BP waveform and AIx may be related to changes in aortic reservoir function.

Assessment of myocardial blood flow (MBF) in humans using arterial spin labeling (ASL): Feasibility and noise analysis

Arterial spin labeling (ASL) is a powerful tool for the quantitative measurement of tissue blood flow, and has been extensively applied to the brain, lungs, and kidneys. ASL has been recently applied to myocardial blood flow (MBF) measurement in small animals; however, its use in humans is limited by inadequate signal-to-noise ratio (SNR) efficiency and timing restrictions related to cardiac motion. We present preliminary results demonstrating MBF measurement in humans, using cardiac-gated flow-sensitive alternating inversion recovery (FAIR) tagging and balanced steady-state free precession (SSFP) imaging at 3T, and present an analysis of thermal and physiological noise and their impact on MBF measurement error. Measured MBF values in healthy volunteers were 1.36 +/- 0.40 ml/ml/min at rest, matching the published literature based on quantitative (13)N-ammonia positron emission tomography (PET), and increased by 30% and 29% with passive leg elevation and isometric handgrip stress, respectively. With thermal noise alone, MBF can be quantified to within +/- 0.1 ml/ml/min with 85.5% confidence, for 3.09 cm(3) regions averaged over 6 breath-holds. This study demonstrates the feasibility of quantitative assessment of myocardial blood flow in humans using ASL, and identifies SNR improvement and the reduction of physiological noise as key areas for future development.

Abstract 2844: Preload Augmentation by Leg Elevation is Helpful in Triaging the Patients with Grade 1 Diastolic Dysfunction

Grade 1 diastolic dysfunction (DD) is a spectrum of a variety of conditions. Objectives: We sought to investigate whether the responses of mitral inflow and annular velocity to leg elevation can provide additional information regarding triaging patients with grade 1 DD. One hundred fifty-four consecutive patients with hypertension with abnormal left ventricular (LV) relaxation on Doppler mitral inflow (early (E)/late (A) mitral inflow velocity &lt;0.75 or deceleration time &gt; 240 ms) were enrolled. Patients with LV ejection fractions less than 50%, a previous history of ischemic heart disease, inducible regional wall motion abnormality, valvular or myocardial disease, or any other volume overloading diseases were excluded. After resting evaluation, echo-Doppler measurements were performed during passive leg elevation and symptom-limited graded bicycle exercise. Patients were divided into two groups according to resting E/E’: Group I (E/E’&lt;15) and II (E/E’≥15, n=23). Group I subjects were further subdivided into IA (persistent E/E’ &lt;15, n=112) and IB (change to E/E’≥15, n=19) according to response to leg elevation. Group II had lower systolic (S’), early (E’), and late (A’) diastolic annular velocity, and diastolic reserve index to exercise (E’xΔE’50W) and higher LV elastance index (E/E’/stroke volume) than that of group IA; there was no significant difference compared to group IB. Group IB had more female predominance, older age, lower E’, higher diastolic elastance index, and higher E/E’ at 25W and 50W exercise accompanied by lower exercise capacity compared to group IA. Preload augmentation by leg elevation might provide additional information in triaging patients with grade 1 DD.

The Influence of Passive Leg Elevation on the Cross-Sectional Area of the Internal Jugular Vein and the Subclavian Vein in Awake Adults

The aim of this study was to evaluate the influence of passive leg elevation and Trendelenburg position on the cross-sectional area (CSA) of the internal jugular (II) and subclavian veins (SCV). Ultrasound imaging was used for the following measurements of both the IJV and SCV baseline in the supine position (control); Trendelenburg position 15 degrees; reverse Trendelenburg position 15 degrees and passive leg elevation 50 degrees. Twenty healthy male volunteers were studied. Mean CSA of the IJV was 1.12 +/- 0.57 cm2 in control, 1.66 +/- 0.67 cm2 in the Trendelenburg position (P < 0.0001 vs. control), 0.38 +/- 0.23 cm2 in the reverse Trendelenburg position (P < 0.0001 vs. control), and 1.40 +/- 0.64 cm2 during passive leg elevation (P < 0.0001 vs. control). Mean CSA of the SCV was 0.92 +/- 0.23 cm2 in control, 0.98 +/- 0.17 cm2 in the Trendelenburg position, 0.86 +/- 0.21 cm2 in the reverse Trendelenburg position and 0.93 +/- 0.18 cm2 during passive leg elevation. The results indicate that passive leg elevation increases the CSA of the IJV, but has little effect on the SCV. The CSA of the IJV appears to be influenced more by gravitational factors than the SCV.

Effect of Preload Augmentation on Pulsed Wave and Tissue Doppler Echocardiographic Indices of Diastolic Function After a Marathon

The mechanisms underlying alterations in left ventricular diastolic function after a marathon are unknown and may be a consequence of a reduced preload. We sought to assess the effect of preload augmentation through passive leg elevation (PLE) on echocardiographic indices of diastolic function after a marathon. Fourteen trained participants (13 male) were echocardiographically assessed before and after a marathon in the supine position and during PLE. Diastolic function was measured via conventional Doppler, color M-mode, and tissue Doppler echocardiography. Early and late transmitral filling velocities (E and A, respectively), flow propagation velocity of early filling, and basal early and late left ventricular wall velocities (E' and A', respectively) were obtained. The E/A ratio, flow propagation velocity of early filling, and the E'/A' ratio decreased by 31%, 24%, and 32%, respectively (P < .05), after marathon running. Postrace PLE returned E to baseline and increased E/A compared with postrace supine (P < .05). However, E/A remained depressed compared with baseline as a result of the persistent elevation in A. Postrace PLE caused Vp to return to baseline; mean E' also increased (9%, P < .05), but did not return to resting levels. Mean A' was unaffected by postrace PLE, therefore, E'/A' was unchanged postrace despite PLE. Postexercise alterations in Doppler indices of diastolic function can be partially explained by a reduction in preload. However, data from tissue Doppler echocardiography indicate that there is an intrinsic impairment in myocardial relaxation after marathon running.

Left Ventricular Performance and Dimensions in Patients with Severe Emphysema

Concomitant heart dysfunction during the course of chronic obstructive pulmonary disease is well recognized. The prevailing view is that mainly the right side of the heart is involved. We evaluated left ventricular (LV) function and dimensions in patients with severe emphysema. Patients with severe emphysema undergoing lung volume reduction surgery were studied after anesthesia induction (n = 10). Non-emphysematous patients scheduled for lobectomy served as controls (n = 10). LV dimensions were measured with patients in the supine position by transesophageal two-dimensional echocardiography and systemic hemodynamics by a pulmonary artery thermodilution catheter, before and during central blood volume expansion by passive leg elevation. Baseline cardiac index (-25%), stroke volume index (SVI, -32%) stroke work index (-34%) and LV end-diastolic area index (EDAI, -33%) were significantly (P < 0.001) lower in the emphysema group. Passive leg elevation increased SVI and LV area ejection fraction more in the emphysema group than in controls (P < 0.05). The DeltaSVI/Delta pulmonary capillary wedge pressure and the DeltaSVI/DeltaEDAI relationships were significantly (P < 0.05) higher in the emphysema group compared to controls (2.2 +/- 0.71 vs 0.6 +/- 0.2 mL/mm Hg x m2 and 5.8 +/- 0.89 vs 2.8 +/- 0.8 mL/cm2 x m2, respectively). Preload-recruitable stroke work (Deltastroke work index/DeltaEDAI), a load-independent index of systolic LV function, did not differ between the two groups. The LV in patients with severe emphysema is hypovolemic, and operates on a steeper portion of the LV function curve, while indices of systolic function are not significantly impaired compared to non-emphysematous controls.

Effects of Lung Volume Reduction Surgery on Left Ventricular Diastolic Filling and Dimensions in Patients With Severe Emphysema

Data on the influence of lung volume reduction surgery (LVRS) on cardiac function and hemodynamics are scarce and controversial. Previous studies have focused mainly on right ventricular function and pulmonary hemodynamics. Here, we evaluated the effects of LVRS on left ventricular (LV) end-diastolic filling pattern, dimensions, stiffness, and performance, as well as pulmonary and systemic hemodynamics. A prospective, open, controlled study. Patients with severe emphysema undergoing LVRS (10 patients). Patients scheduled for pulmonary lobectomy due to carcinoma (ie, the lobectomy group) served as control subjects (10 patients). LV dimensions and mitral flow velocities were measured by transesophageal, two-dimensional, Doppler echocardiography, and central hemodynamics were measured by a pulmonary artery thermodilution catheter. Measurements were performed during anesthesia in the supine position, before and after surgery, without and with passive leg elevation. Baseline cardiac index (CI) [- 21%], stroke volume index (SVI) [- 31%], stroke work index (SWI) [- 26%], and LV end-diastolic area index (EDAI) [- 15%] were significantly (p < 0.001) lower, whereas LV end-diastolic stiffness (LVEDS) did not differ in the LVRS group compared to the lobectomy group. The time from peak early diastolic filling to zero flow (E-dec time) [58%] and the deceleration slope of early diastolic filling (E-dec slope) [45%] were significantly higher (p < 0.01), whereas peak early diastolic filling velocity (E-max) [- 31%; p < 0.01] and the proportion of E-max vs peak late diastolic filling velocity (A-max) [ie, the E/A ratio] (- 27%; p < 0.001) were significantly lower compared to the lobectomy group. LVRS significantly increased CI (40%; p < 0.001), SVI (34%; p < 0.001), SWI (58%; p < 0.001), LV EDAI (18%; p < 0.001), E-max (44%; p < 0.01), A-max (15%; p < 0.05) and E/A ratio (28%; p < 0.01), decreased E-dec time (- 31%; p < 0.05) and E-dec slope (- 98%; p < 0.01), and had no effect on LVEDS. In the lobectomy group, surgery affected none of these variables. LV function is impaired in patients with severe emphysema due to small end-diastolic dimensions. LVRS increases LV end-diastolic dimensions and filling, and improves LV function.

Noninvasive determination of venomuscular efficiency.

The purpose of this study was to express quantitatively and noninvasively the efficiency of the venomuscular pump by using photoplethysmography (PPG). METHODS AND PATIENTS PPG was used to record volume changes induced by dorsiflexion resulting in exercise displacement volume (EDV) and subsequently by passive limb elevation resulting in tilt displacement volume (TDV). Dividing EDV by TDV yields efficiency of the venomuscular pump. Twenty-four control subjects, 21 patients with venous valvular insufficiency (VVI), and 10 additional patients with both VVI and deep venous thrombosis (DVT) were studied. Data for one leg in each subject are reported. Though calculation of efficiency does not require calibrated or quantitative PPG, in this case because we used calibrated PPG we recorded the respective values for EDV after dorsiflexion and TDV after passive leg elevation. EDV decreased from a normal value of 3.15% optical reflectance (% OR) to 1.68% OR in patients with VVI and 1.09% OR in patients with VVI plus DVT. TDV response was quite opposite, increasing from 6.55% OR in the control group to 10.30% OR in the VVI group and 16.66% OR in the VVI plus DVT group. Finally, efficiency decreased from the average normal value of 50.5% to 24.4% in the VVI group and 8.8% in the VVI plus DVT group. Dividing EDV by TDV, venomuscular efficiency can be determined and may be considered a useful index of venous hemodynamics.

Passive leg elevation and head-down tilt: effects and duration of changes.

I am intrigued by the recent further evaluation of passive leg elevation (PLE) in the perioperative period for patients undergoing cardiac surgery [1]. Following prior involvement with somewhat similar evaluations [2], I am left wondering what conclusions may have been reached if the experimental protocol had been expanded to include a penultimate assessment with the legs still elevated (i.e. between time point 3 and time point 4), and also to examine the effects of head-down tilt (HDT) as used during central venous cannulation. On the one hand, the autonomic [2] and haemodynamic effects [3-5] of postural manipulation have been shown to be both minimal and short lived. I surmise that the adverse effects observed may have been self-correcting during the course of PLE, rather than only after resumption of the supine position (i.e. before time point 4). This perhaps thereby minimises the clinical importance of these effects. On the other hand, the patterns of changes seen with HDT are very similar to those induced by PLE [2,3]. It follows that any caution advised regarding PLE for patients known to have reduced right ventricular ejection fraction should be extrapolated to the use of HDT for central venous catheter placement. The data provided could justifiably be added to a list of reasons for avoiding the indiscriminate use of PLE as a therapeutic manoeuvre in hypotensive conditions. As for other applications, it is difficult to think of an immediate alternative to PLE for the preparation of the sterile field required for a coronary artery bypass vein graft requiring use of harvested saphenous veins (or to HDT in central venous catheter placement). The advised caution deserves due consideration for both PLE and HDT.

Lung volume reduction surgery improves left ventricular diastolic function

Background and goal: Lung volume reduction surgery (LVRS) improves pulmonary function and increases exercise performance in patients with severe emphysema (1). We evaluated the effects of LVRS on left ventricular function, assuming that LVRS improves diastolic function by reducing the pulmonary tamponade of the heart. Materials and Methods: Ten patients scheduled for LVRS were studied after informed consent. After induction of anaesthesia, a pulmonary artery thermodilution catheter was inserted for measurements of pulmonary hemodynamics. A multiplane transesophageal echocardiographic transducer visualised the left ventricle for measurements of end-diastolic area (EDA), and for analysis of mitral Doppler flow profiles. Images were stored on VHS videotape and analysed using a PC-based off-line analysis system (2). Pulmonary capillary wedge pressure (PCWP) and EDA were measured before and after surgery in the supine position and during passive leg elevation to establish the left ventricular end-diastolic pressure-area curve. For statistical analysis, a paired Students t-test and a repeated measures ANOVA was used. Results are reported as Mean S.E.M. *p 0.05. **p 0.01. Results:

Cardiopulmonary baroreflex stimulation and blood pressure-related hypoalgesia

Results from both experimental animals and humans suggest that baroreflex stimulation may be involved in blood pressure-related hypoalgesia. However, most of this research, especially in the area of human experimentation, has focused on sinoaortic baroreceptors. Cardiopulmonary baroreflex stimulation may also be an important moderator of pain. Sixty-six healthy male undergraduates varying in risk for hypertension participated in an experimental protocol in which painful mechanical finger pressure was presented three times in a counterbalanced fashion. One pain stimulus was preceded by 6 min of supine rest, another by a period of rest interspersed with periodic Valsalva manoeuvres, and another by a period in which cardiopulmonary baroreceptors were stimulated by passive leg elevation. Significantly lower pain was reported by men with relatively elevated systolic blood pressure following leg elevation but not the other conditions. Cardiopulmonary baroreflex stimulation was documented by increased forearm blood flow and other data obtained via impedance cardiography. These results suggest that blood pressure related hypoalgesia may be at least partially related to cardiopulmonary baroreflex stimulation.

Alternations in atrial natriuretic peptide release after DC cardioversion of non-valvular chronic atrial fibrillation.

The response of atrial natriuretic peptide (ANP) release to haemodynamic influences after cardioversion of atrial fibrillation has not been fully examined. We measured plasma concentrations of ANP and assessed haemodynamic changes 60-120 min after DC cardioversion in 22 patients with non-valvular chronic atrial fibrillation. Passive leg elevation to enhance volume expansion was performed 60 min after DC cardioversion. Sinus rhythm was restored in 18 of the 22 patients (successful DC cardioversion group). The control group consisted of seven patients with non-valvular chronic atrial fibrillation who did not undergo DC cardioversion (atrial fibrillation control group). In the successful DC cardioversion group, the mean pulmonary artery wedge pressure decreased significantly 15 min after cardioversion (P < 0.05) and then remained unchanged. Plasma concentrations of ANP also decreased significantly 15 min after cardioversion (P < 0.05). Furthermore, there was an additional significant decrease in ANP levels for up to 60 min after cardioversion (P < 0.05 from 15 min). Passive leg elevation for 15 min led to an increase in the mean pulmonary artery wedge pressure (P < 0.01) and right atrial pressure (P < 0.05), but did not result in increased plasma concentrations of ANP (47.1 +/- 27.6 vs 43.9 +/- 34.4 pg.ml-1, mean +/- SD, P = ns). In the atrial fibrillation control group, passive leg elevation increased the mean pulmonary artery wedge pressure (P < 0.01), the mean right atrial pressure (P < 0.05) and plasma concentrations of ANP (139.9 +/- 85.8 vs 168.1 +/- 108.2, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Human pulmonary vascular and venous compliances are reduced before and during left-sided heart failure

Human pulmonary vascular and venous compliances were measured in 41 patients with or without left-sided heart failure. Two methods were used. Method 1 was based on analysis of pulmonary capillary wedge (PCW) pressure tracings according to Cv,PCW = (SF/100)(0.075PCW + 0.90)SV/[(v - d)PCW + 1], where Cv,PCW is compliance of pulmonary venous system, SF is systolic fraction of pulmonary venous flow [related to pulmonary capillary wedge pressure (PCW) as SF = 82 - 2.01PCW], (v - d)PCW is pulse pressure in PCW position, and SV is stroke volume. The (0.075PCW + 0.90) term equals k", i.e., systolic run-off ratio. Method 2 was used to measure to pulmonary vascular volume-pressure (V-P) relationship and pulmonary vascular compliance (Cvasc) and is based on measurement of pulmonary blood volume (PBV) and its increase with passive elevation of the legs to calculate Cvasc. Assuming the proportion of blood entering pulmonary venous system (in increase of PBV) during passive leg elevation to be 0.8, pulmonary venous compliance (Cv,PBV) was calculated as Cv,PBV = 0.8Cvasc. Cv,PCW correlated fairly closely with Cv,PBV (r = 0.81, coefficient of variation = 31%). This fair agreement between two independent methods suggests strongly that both methods may be valid, although other interpretations are possible. Cv,PCW, Cvasc, and Cv,PBV decreased going from New York Heart Association class I to classes II and III. When PBV was plotted vs. PCW, average V-P line for class II patients was flatter and shifted downward to the right compared with that for class I. This suggests pulmonary vasoconstriction as well as other factors. Average V-P line for class III patients is flatter but not displaced compared with that for class II. Another previously reported series of 50 patients, most of whom had ischemic heart disease, are included in this study.