Femoral Pressure Research Articles

Case report: Inferior vena-cava right atrial anastomotic stenosis after bicaval orthotopic heart transplantation

This case report describes the occurrence of acute postoperative liver and renal failure after bicaval orthotopic heart transplantation (OHT) due to stenosis of the inferior vena cava (IVC)-right atrial (RA) anastomosis. We also discuss the role of measuring femoral venous pressure and transesophageal echocardiography (TEE) in establishing the diagnosis. A 42-yr-old female patient with idiopathic dilated cardiomyopathy underwent an OHT, using the bicaval anastomotic technique. During the first 12 hr postoperatively she developed unexplained kidney and liver failure. Her left and right ventricular functions were excellent and the right and left sided filling pressures were normal. The femoral pressure was elevated while the RA pressure was normal. An emergent TEE showed colour-flow and Doppler characteristics consistent with IVC-RA anastomotic stenosis. Emergent surgical re-exploration was undertaken; a hemostatic suture was found at the RA cannulation site that had caused the constriction of the IVC-RA anastomosis. Acute liver and renal failure after OHT can have multiple causes including ischemia due to a low flow state. This case demonstrates the importance of doing a detailed intraoperative TEE after OHT, and the importance of repeating the intraoperative examination after any hemostatic sutures are placed. Femoral venous pressure monitoring can be a useful diagnostic tool in detecting IVC-RA stenosis.

Wave reflection effects in the central circulation of American alligators (Alligator mississippiensis): what the heart sees

A large central compliance is thought to dominate the hemodynamics of all vertebrates except birds and mammals. Yet large crocodilians may adumbrate the avian and mammalian condition and set the stage for significant wave transmission (reflection) effects, with potentially detrimental impacts on cardiac performance. To investigate whether crocodilians exhibit wave reflection effects, pressures and flows were recorded from the right aorta, carotid artery, and femoral artery of six adult, anesthetized American alligators (Alligator mississippiensis) during control conditions and after experimentally induced vasodilation and constriction. Hallmarks of wave reflection phenomena were observed, including marked differences between the measured profiles for flow and pressure, peaking of the femoral pressure pulse, and a diastolic wave in the right aortic pressure profile. Pulse wave velocity and peripheral input impedance increased with progressive constriction, and thus changes in both the timing and magnitude of reflections accounted for the altered reflection effects. Resolution of pressure and flow waves into incident and reflected components showed substantial reflection effects within the right aorta, with reflection coefficients at the first harmonic approaching 0.3 when constricted. Material properties measured from isolated segments of blood vessels revealed a major reflection site at the periphery and, surprisingly, at the junction of the truncus and right aorta. Thus, while our results clearly show that significant wave reflection phenomena are not restricted to birds and mammals, they also suggest that rather than cope with potential negative impacts of reflections, the crocodilian heart simply avoids them because of a large impedance mismatch at the truncus.

Pressure gradients and transport in the murine femur upon hindlimb suspension

Interstitial fluid flow (IFF) is important in a number of processes, including stimulation of cells and nutrient and waste transport. In bone, it arises from the vascular pressure gradient between the medullary cavity and the lymphatic drainage at the periosteal surface and is enhanced by mechanical loading events. However, little is known about the pressure gradients experienced by bone cells in vivo and the role of the induced IFF in bone adaptation. This study investigated IFF changes in bone, in a disuse model and in ambulatory mice, from pressure gradients measured by telemetry, and by fluorescent tracers. The role of IFF-mediated transport of oxygen was assessed by the levels of hypoxic osteocytes in mouse femur after disuse by hindlimb suspension and with or without femoral vein ligation. Femoral intramedullary pressures in alert mice decreased to 77% upon hindlimb suspension and increased by 25% upon ligation, relative to baseline. To determine relative perfusion of cortical bone by IFF, the localization of intracardiac-injected fluorescent albumin conjugate with osteocytes was monitored. The number of osteocytic lacunae per bone area positive for Texas Red albumin was increased by 31% within 20–40 s, in the ligated femur compared to the contralateral sham femur. This confirmed that interstitial fluid flow was increased by femoral vein ligation and indicated that the increase was proportional to the pressure increase. Unloaded bone osteocytes were not hypoxic when compared to loaded controls and venous ligation did not alter these levels significantly. These results support the hypothesis that disuse by hindlimb suspension leads to decreased pressure gradients, which indicate lower IFF. Similarly, the increased pressure gradients, seen upon venous ligation, increased IFF from marrow to periosteum. While a decrease in intramedullary pressure in disuse suggests a decrease in IFF, this did not lead to hypoxia in osteocytes. We conclude that decreased oxygen convective transport in the mouse hindlimb disuse model does not account for cortical bone loss. This study is important in increasing our understanding of the mechanotransductory pathways involved in bone loading and unloading.

Douleurs ambiguës “de hanche” ou de fesse, artérite proximale ou canal lombaire sténosé?

Proximal arterial stenosis (bifurcation of the aortic, common iliac and especially hypogastric or hip arteries) can cause misleading 'hip' or buttock pain (two thirds of these cases involve the area of the trochanter, groin, or thigh). Their essential characteristic is that they cause patients to stop walking, improve in a minute or two and reappear when the patient starts walking again. Neither articular complications nor periarthritis of the hip fit this pattern, and physical examination and imaging exclude them. Neurogenic intermittent claudication is more difficult to rule out: it is 'often accompanied by paresthesia and anteflexion of the trunk to relieve the pain. A radiologic image of lumbar canal stenosis alone does not indicate that it is responsible for the pain: the stenosis may be asymptomatic and only fortuitously associated with the pain. The usual reduction in femoral pulse or ankle pressure index is absent if the stenosis is located on the hypogastric or gluteal artery and there is not substantial damage to the aorta-iliac axis. Arterial stenosis is confirmed by Doppler ultrasound. Arteriography is an examination performed during treatment, to guide angioplasty. It is indicated when medical treatment fails, as it frequently does.

Adenosine A2A receptor plays a pivotal role in mediating clonidine hypotension in aortically barodenervated rats

In a previous study, we have shown an important role of central adenosine in the hypotension caused by clonidine, a mixed α2/I1 centrally acting antihypertensive agent. Intracisternal (i.c.) 8-sulfophenyl theophylline (8-SPT) abolished, while dipyridamole enhanced, clonidine-evoked hypotension in conscious aortic barodenervated (ABD) rats. Since clonidine is a mixed α2/I1, we investigated whether the I1- or the α2-mediated hypotension is dependent on central adenosine signaling. To this end, conscious ABD rats were instrumented 5 days earlier for femoral blood pressure recording and i.c administration of selective I1 (rilmenidine 25 μg/kg;n=6–7) or α2 (α-methlnorepinephrine, αMNE, (4μg/kg; n= 6–7) agonist 30 min after central (i.c) adenosine receptor blockade (8-SPT; 10 μg/kg) or aCSF. The hypotensive response elicited by rilmenidine (24 ± 5 mmHg) and α-MNE (16 ± 3 mmHg) in aCSF pretreated animals was virtually abolished in 8-SPT pretreated rats. We concluded that I1/α2-mediated hypotension is dependent on central adenosine signaling. We hypothesized that the A2A is responsible for mediating clonidine-evoked hypotension. In the same animal model, the hypotensive and bradycardic responses elicited by i.c clonidine (0.6 μg) were investigated 30 min after central (i.c) adenosine receptor A2A blockade (SCH5826 0.5mg /kg, i.c; n=5) or aCSF. The hypotensive response to clonidine was abolished by SCH5826 compared to the respective control. In conclusion, adenosine is a key mediator of clonidine-evoked hypotension specifically through the A2A receptors. Mechanistic studies are underway to determine the cellular pathways mediating the receptors cross talk.

Neutrophils modulate post-thrombotic vein wall remodeling but not thrombus neovascularization

Early deep venous thrombosis (DVT) resolution is associated with neutrophil (PMN) influx. This study examined the role of PMNs in thrombus neovascularization and vein wall injury after DVT. A rat model of DVT by inferior vena cava (IVC) ligation was performed with control serum or rabbit anti-rat PMN serum administered perioperatively with sacrifice at 2 and 7 days. At 2 days, neutropenic rats had 1.6-fold larger thrombi (P = .04) and 1.4-fold higher femoral venous pressures by water manometry (P = .008) but no difference in thrombus neovascularization was observed. By 7 days, DVT sizes were similar, but vein wall injury persisted in the neutropenic rats with a 2.0-fold increase in vein wall stiffness by microtensiometry (P < .05), as well as a 1.2-fold increased thickness (P = .04). Collagen and profibrotic growth factors were significantly increased in neutropenic IVC at 7 days (all P < .05). Vein wall and intrathrombus uPA byWestern immunoblotting, and intrathrombus MMP-9 gelatinase activity were significantly less in neutropenic rats than controls (P < .001). Conversely, MMP-2 was significantly elevated in neutropenic IVC at 2 days after DVT. However, neutropenia induced 24 hours after DVT formation resulted in no significant increase in vein wall stiffness or collagen levels at 7 days, despite 1.4-fold larger thrombi (P < .05). These data suggest a critical early role for PMN in post DVT vein wall remodeling.

Testosterone and Nandrolone Sensitization of Brain Anteroventral Area of Third Ventricle to Hypertonic NaCl-Induced Sympathetic Response

Androgenic steroids increase atherogenesis, thrombogenicity and endothelial dysfunction when administered in high doses, however their effects on NaCl sensitivity of the brain anteroventral area of the third ventricle (ΔV3V) have not been explored. Sprague-Dawley male rats were anesthetized with sodium pentobarbital (40 mg/kg) and the femoral intra-arterial blood pressure and heart rate monitored through a strain-gauge blood pressure transducer and tachograph. ΔV3V microinjections of (2 µl) 1.5 mol/l NaCl solution were done according to brain coordinates: AP = 7.0 mm, L = 1.0 mm, D = 7.5 mm through a 0.2-mm diameter stainless steel needle. The injection site was verified with 1.0 µl neutral red solution. Basal systolic blood pressure increased 37.6 and 39.6 mm Hg after testosterone (1 mg/kg/day for 20 days) and nandrolone (1 mg/kg/day for 20 days) treatment respectively; diastolic blood pressure also increased upon testosterone and nandrolone treatment in 36.4 and 53.1 mm Hg, respectively; basal heart rate did not change. Vasopressor response to 1.5 mol/l NaCl ΔV3V microinjection was higher in testosterone-treated rats; systolic blood pressure increased 56.0 vs. 28.3 control mm Hg; diastolic blood pressure increased 54.0 vs. 25 control mm Hg. This hypertensive response was 29% longer lasting in testosterone compared to vehicle-treated rats. The same pattern of ΔV3V sensitization to hypertonic NaCl was observed in nandrolone-treated rats. Blood lipid profile changed to a proatherogenic fashion upon testosterone and nandrolone long-term treatment; the plasma-free testosterone concentration increased from 4.9 ± 0.9 to 36.0 ±7.1 pg/ml with the same testosterone treatment schedule. In conclusion, long-term androgenic steroid treatment sensitizes the brain ΔV3V region to hypertonic NaCl which in turn conducts into a sympathetic vasopressor and heart rate-stimulating action.

Radial to femoral arterial blood pressure differences during liver transplantation

This observational study compared femoral and radial arterial blood pressure in 72 patients undergoing liver transplant surgery. Simultaneous femoral and radial arterial blood pressures, cardiac index, core temperature and vasoconstrictor therapy were recorded at seven time points during the operation. No significant differences between radial and femoral pressures were found at the start of surgery. Femoral and radial systolic arterial blood pressures were statistically significantly different during liver reperfusion (mean (SD) arterial pressure = 92 (22) mmHg vs. 76 (22) mmHg, p < 0.01). Mean arterial blood pressures showed no statistically significant differences throughout the study. Vasoconstrictor drug administration was associated with a larger systolic pressure difference between femoral and radial arteries (28 (24) mmHg in patients being given vasoconstrictor drugs vs. 9 (19) mmHg in patients not needing vasoconstrictors during reperfusion, p < 0.001). In conclusion, differences in systolic arterial blood pressure occur between femoral and radial arterial monitoring sites during liver reperfusion, and in particular in patients being given vasoconstrictor therapy. Thus, if femoral arterial monitoring is not available, clinicians should rely on mean rather than systolic arterial pressure measurements from a radial artery catheter during liver transplantation.

Diagnosis and management of acyanotic heart disease: Part I - obstructive lesions

In this review, the clinical features and management of most commonly encountered acyanotic obstructive cardiac lesions are discussed. Mild lesions, especially in children are usually asymptomatic while neonates and infants may present with symptoms. Ejection systolic murmurs in patients with pulmonic and aortic stenosis and decreased femoral pulses and blood pressure difference (>20 mmHg) between arms and leg in patients with aortic coarctation are usually seen. Clinical diagnosis is not difficult and the diagnosis can be confirmed and quantitated by non-invasive echocardiographic studies. Whereas surgical intervention was used in the past, balloon dilatation appears to be effective in the treatment of these lesions.

Are there changes in leg vascular resistance during laparoscopic cholecystectomy with CO2 pneumoperitoneum?

The prompt haemodynamic response to carbon dioxide insufflation during laparoscopic cholecystectomy suggests involvement of the sympathetic system. The aim of the present study was to examine if a change in vascular resistance in leg skeletal muscle could be an important mechanism behind the increased afterload. Furthermore, the arterio-venous differences of the catecholamines were measured in the leg before and during insufflation of carbon dioxide into the peritoneal cavity. Ten patients (ASA I) scheduled for laparoscopic cholecystectomy were included. After induction of anaesthesia, catheters were introduced percutaneously into the radial artery, the femoral vein and the cubital vein for pressure monitoring and blood sampling. The arterial blood flow in the legs was measured by mercury-in-Silastic strain gauge venous occlusion plethysmography. Vascular resistance in the right leg (LVR) was calculated from the formula: (MAP-FVP)/calf blood flow. Measurements were made before and 5 min after insufflation of pneumoperitoneum. Induction of pneumoperitoneum increased the heart rate (P < 0.05) and also increased mean arterial pressure and femoral vein pressure as well as the calculated leg vascular resistance (P < 0.01). Calf blood flow did not change significantly in either leg. Both arterial and venous noradrenaline concentrations were higher after insufflation (P < 0.01). In patients without heart or lung disease, pneumoperitoneum at an intra-abdominal pressure level of 11-13 mmHg increased the peripheral vascular resistance in the leg while the arterial blood flow in the leg was unaffected. Catecholamine levels increased, but were still low. Therefore, we suggest that the increase in peripheral vascular resistance is caused by increased myogenic activity in the resistance vessels secondary to increased arterial and transmural pressure rather than by increased neurogenic sympathetic activity.

Blood flow response to a postural challenge in older men and women

BackgroundThe purpose of this study was to measure blood flow in the carotid and femoral arteries, heart rate and blood pressure in response to postural challenge in older adults. A second purpose was to determine if older men and women have different cardiovascular responses to a postural challenge such as tilt.MethodsThirty-seven healthy elderly men and women participated in this study (69–82 years old). All subjects had similar physical activity levels. Postural challenge was induced by a 60° tilt at the level of the waist. Continuous carotid blood flow and femoral blood flow was measured with Doppler ultrasound.ResultsCarotid blood flow was significantly reduced 17% in both men and women immediately after tilt (p < 0.001), and by 3.2% two minutes after tilt (p < 0.001). Femoral blood flow decreased 59.4% in men and 61% in women immediately after tilt (p < 0.001), and remained significantly decreased two minutes after tilt by 21% (p <0.001). Heart rate increased by 15% in men (p < 0.001), and 26% in women immediately after the tilt (p < 0.001). Heart rate returned to resting values within two minutes in both men and women. Response to tilt was not significantly related to self-report physical activity levels or to six-minute walk time.ConclusionA postural challenge induced larger changes in the femoral artery compared to the carotid artery. There were no differences between men and women to a tilt table test except for differences in heart rate response. There was no difference in the blood flow responses to postural challenge with physical activity level or between healthy older men and women.

Hemodynamic effects of a new percutaneous circulatory support device in a left ventricular failure model.

We have tested a new percutaneous circulatory support device in seven anesthetized calves with induced left ventricular failure. The device is based on a flexible catheter with a foldable propeller and cage at the distal end. The rotation of the propeller (1,000-15,000 rpm) is transmitted from a drive unit at the proximal end to the propeller by way of a rotating wire inside the catheter. This also contains an umbrella-like mechanism to open the pump head from the folded (diameter 4.6 mm) to the active position. The rotation of the propeller creates a pressure drop in front of the propeller and a pressure rise behind. Heart failure was induced with metoprolol and verapamil in combination with a VVI pacemaker to create a left atrial pressure greater than 20 mm Hg. A centrifugal pump was used to bypass the right ventricle and to ensure a sufficient filling of the left ventricle. After baseline recordings, the pump was run at 14,000 rpm, and the hemodynamic response was compared with the baseline. A 24 +/- 10 mm Hg pressure gradient was generated across the pump, resulting in a drop in the right carotid artery mean pressure from 80 +/- 11 to 71 +/- 13 mm Hg (p = 0.008) and a drop in the left ventricular systolic pressure from 109 +/- 17 to 100 +/- 19 mm Hg (p = 0.004). The pressure in the left atrium decreased from 25 +/- 3 to 20 +/- 5 mm Hg (p = 0.008). The mean femoral pressure increased from 78 +/- 10 to 95 +/- 20 mm Hg (p = 0.005). A moderate reduction in the right carotid flow was observed (15%, p = 0.029), whereas no significant changes were found in the coronary flow, the flow in the right femoral artery, or in the left kidney. The device showed a significant unloading of the left ventricle and an increased perfusion pressure for the lower part of the body. The moderate changes in flow were probably caused by still active autoregulation, and this needs to be tested with more pronounced circulatory failure.

A novel, valveless ventricular assist device: the FishTail pump. First experimental in vivo studies.

This article presents the first in vivo experiments with a new type of valveless ventricular assist device, a wave-generating pump. Our goal was to evaluate the hemodynamic performance of the pump by comparing it with the Biomedicus BP-80 centrifugal pump and by sustaining a 3 h long left ventricular assistance. We connected the two pumps in parallel and switched between them. We increased the aspiration by increments of -10 mm Hg at the inlet and measured developed flow, right carotid and femoral pressure, left atrial pressure, and left carotid flow. Then, we let the FishTail perform a 3 h long left ventricular assistance. The mean developed flow on the outlet was higher with the FishTail, with statistical significance, but this difference was not clinically significant. However, we observed an important amount of hemolysis during the ventricular assistance period. Although promising, this novel pumping device needs further prototypes to be clinically applicable.

Intima-media thickness in cardiovascularly asymptomatic hypopituitary adults with growth hormone deficiency: relation to body mass index, gender, and other cardiovascular risk factors.

Increased cardiovascular mortality and carotid atherosclerosis have been observed in hypopituitary patients with untreated GH deficiency (GHD), but results are contradictory and relations to cardiovascular risk factors are not clear. The aim of this study was to investigate intima-media thickness (IMT) in relation to cardiovascular risk factors in adults with GHD. Cross-sectional observational study of 21 men and 13 women with GHD, but without cardiovascular disease, compared to two healthy control groups matched for age, sex and smoking habits. One control group was matched for body mass index (BMI) and the other group was nonobese. IMT of the carotid and femoral arteries, blood pressure, blood samples and anthropometric data. Patients had 12% thicker composite carotid IMT [(IMT of common carotid artery + IMT of bulb)/2] compared to nonobese controls (P = 0.022), but IMT was not different compared to BMI-matched controls. Femoral IMT did not differ between patients and controls. Patients had higher waist : hip ratio (WHR), heart rate, serum triglycerides and fasting insulin concentrations in combination with lower high-density lipoprotein (HDL) cholesterol and smaller low-density lipoprotein (LDL) peak particle size compared to both nonobese and to BMI-matched controls. This cardiovascular risk pattern was more pronounced in female patients than in male patients compared to their gender controls. Carotid IMT was related to age, serum cholesterol, LDL cholesterol and smoking in the patient group. Only age was independently related to carotid IMT in multivariate analysis. These results indicate that high BMI in GH-deficient patients contribute to their increased intima-media thickness. However, several cardiovascular risk factors are present in this patient group independent of their increased BMI, especially in women.

Accuracy of radial arterial pressure measurement during surgery under controlled hypotension.

Radial arterial pressure underestimates the pressure in the aorta in several clinical situations. A central-to-radial pressure gradient was attributed to intense vasodilation. The aim of this study was to evaluate the accuracy of radial pressure monitoring during controlled hypotension achieved with profound arterial vasodilation. Ten patients with ASA physical status I and II undergoing maxillofacial surgery under general anesthesia were enrolled in this prospective study. Radial and femoral arteries were cannulated and connected to a pressure monitoring system. Controlled hypotension was achieved with an infusion of nicardipine titrated to maintain MAP between 50 and 60 mmHg. Simultaneous radial and femoral systolic, mean and diastolic arterial pressures were recorded before, during and after controlled hypotension. Results were expressed as mean +/- SD. Concomitant radial and femoral pressures were compared by a paired Student's test, P < 0.05 being significant. In all, 150 sets of arterial pressures measurement were obtained. There were no statistically significant differences between radial and femoral arterial pressures measured before, during or after controlled hypotension. Radial arterial pressure is an accurate measure of central arterial pressure during controlled hypotension achieved with arterial vasodilation.

A Comparison of Femoral and Radial Artery Pressure during an Adult Liver Transplantation

Background: The radial artery pressure is known to differ from central arterial pressure in normal patients (distal pulse amplification) and in the early postcardiopulmonary bypass period. We assumed that there may be a change in the normal relationship between central and peripheral arterial pressure in patients with hepatic failure due to an arterio-venous shunt caused by vasodilation and a complex surgical procedure with major vessel clamping. This study was done to examine the adequacy of the radial artery as a site for blood pressure monitoring in liver transplantation (TPL). Methods: We investigated when the pressure gradient developed and what mechanism could be responsible by comparing femoral to radial artery pressure in 11 patients undergoing liver transplantation. Radial and femoral artery pressures, systemic vascular resistance, cardiac output and temperature were compared during surgery in all 11 patients. Additionally measurements included pH, /kg, /kg, central venous pressure, puhnonary artery pressure and mixed venous oxygen saturation. Results: The femoral artery systolic pressure was higher than the corresponding radial artery pressures during the operation. Although not statistically significant, the radial mean and diastolic artery pressures were lower than corresponding the femoral artery pressure. Conclusions: Radial artery systolic pressures underestimate the femoral artery pressure when undergoing a liver TPL. Failure to recognize these effects on pressure recordings can lead to inappropriate patient management decisions.

Femoral artery pressures are more reliable than radial artery pressures on initiation of cardiopulmonary bypass

To compare radial and femoral artery perfusion pressure during initiation and various stages of cardiopulmonary bypass (CPB). Prospective study. The cardiac center of a tertiary referral teaching institute. Sixty consecutive patients of all ages undergoing a variety of cardiac operations. Radial and femoral arterial pressures were measured in all patients on the same transducer, from the beginning to end of CPB. Mean perfusion pressures on CPB measured at the femoral artery at 1, 5, 10, and 15 minutes of CPB were 38.4+/-3.6, 46.2+/-3.1, 49.7+/-3.9, and 52.8+/-4.1 mmHg and were significantly greater than the corresponding radial artery pressures (29.9+/-4.1, 35.3+/-6.1, 40.9+/-4.8, and 41.8+/-5.3 mmHg) (p < 0.001). At 30 minutes and 60 minutes of CPB, femoral artery pressures are higher (60.3+/-8.8 mmHg and 66.4+/-8.2 mmHg) compared with radial artery pressures (54.7+/-6.9 mmHg and 59.6+/-6.1 mmHg), but the difference is less significant (p < 0.05). On conclusion of CPB, mean femoral artery pressures (70.9+/-6.7 mmHg) are greater than mean radial artery pressures (67.6+/-8.1 mmHg) (NS). Although radial artery pressures are more commonly monitored during cardiac surgery, femoral artery perfusion pressures are more reliable during the initial part of CPB, and routine monitoring of femoral artery pressures may prevent vasoconstrictor use on initiation of CPB.

Femoral artery pressures are more reliable than radial artery pressures on initiation of cardiopulmonary bypass

Objective To compare radial and femoral artery perfusion pressure during initiation and various stages of cardiopulmonary bypass (CPB).Design Prospective study.Setting The cardiac center of a tertiary referral teaching institute.Participants Sixty consecutive patients of all ages undergoing a variety of cardiac operations.Interventions Radial and femoral arterial pressures were measured in all patients on the same transducer, from the beginning to end of CPB.Measurements and Main Results Mean perfusion pressures on CPB measured at the femoral artery at 1, 5, 10, and 15 minutes of CPB were 38.4 ± 3.6, 46.2 ± 3.1, 49.7 ± 3.9, and 52.8 ± 4.1 mmHg and were significantly greater than the corresponding radial artery pressures (29.9 ± 4.1, 35.3 ± 6.1, 40.9 ± 4.8, and 41.8 ± 5.3 mmHg) (p < 0.001). At 30 minutes and 60 minutes of CPB, femoral artery pressures are higher (60.3 ± 8.8 mmHg and 66.4 ± 8.2 mmHg) compared with radial artery pressures (54.7 ± 6.9 mmHg and 59.6 ± 6.1 mmHg), but the difference is less significant (p < 0.05). On conclusion of CPB, mean femoral artery pressures (70.9 ± 6.7 mmHg) are greater than mean radial artery pressures (67.6 ± 8.1 mmHg) (NS).Conclusions Although radial artery pressures are more commonly monitored during cardiac surgery, femoral artery perfusion pressures are more reliable during the initial part of CPB, and routine monitoring of femoral artery pressures may prevent vasoconstrictor use on initiation of CPB.

Femoral arterial pressure monitoring during cardiopulmonary bypass: a word of caution

A 69-year-old man was admitted for elective coronary artery bypass grafting. He had a history of chronic hypotension that caused him to have occasional dizziness upon standing and at the time of his exercise test he was noted to have low blood pressure. Subsequent coronary angiography showed poor left ventricular function but, due to his low blood pressure, he was not started upon Angiotensin Converting Enzyme inhibitors. During pre-operative assessment, his left brachial blood pressure was measured as 82/44 mmHg using a sphygmomanometer. When the left radial artery was subsequently cannulated prior to surgery, it showed a pressure of 85/50 mmHg which corresponded to a pressure of 88/54 mmHg measured at the same time noninvasively on the right arm. However, on review prior to the induction of anaesthesia, it was noted that at cardiac catheterisation the pressure measured in the aorta had been 178/88 mmHg and so a femoral arterial line was inserted. This measured a pressure of 165/85 mmHg. During the operation and cardiopulmonary bypass (CPB) the femoral arterial line was used for pressure monitoring and the mean arterial pressure (MAP) was maintained at 85 mmHg. This pressure was higher than we would normally use during CPB but it equated with a mean pressure in the radial artery of 55 mmHg. His postoperative course was uneventful and he recovered with no neurological problems. A postdischarge Duplex scan showed no flow to either common internal or external carotid arteries, the subclavian arteries were damped and the only patent arterial supply to the brain was a markedly enlarged right vertebral artery. Subsequent CT angiography showed that the left brachiocephalic artery was occluded with the distal subclavian filling by collaterals. It is well recognised that following the onset of CPB a pressure gradient may develop between the radial and femoral arteries [1]. Because the femoral pressure equates more consistently with the aortic pressure, it is increasingly used to monitor blood pressure of patients undergoing cardiac surgery. In our patient, a significant gradient existed even before surgery was begun but it was only appreciated when both the femoral and the radial arterial pressures were measured simultaneously prior to the induction of anaesthesia. If, as is common practice, a femoral arterial line had been used from the outset, then a lower mean arterial pressure would have been maintained during bypass. Since a large fixed gradient already existed between the femoral and the radial arteries, a lower femoral pressure would have produced a very low radial pressure but this would have gone unnoticed. Fortunately, the simultaneous monitoring of a radial and femoral arterial pressure revealed a large femoral–radial pressure gradient, and alerted us to bilateral subclavian arterial disease and the possibility of carotid disease. By assuming a correlation between radial MAP and cerebral perfusion pressure and maintaining the radial MAP at 55 mmHg during CPB, we achieved a cerebral perfusion pressure adequate to prevent detectable cerebral injury. If femoral lines are being routinely used to monitor blood pressure during cardiac surgery, or indeed other major surgery, then we would recommend that the pressure in the upper limbs be assessed noninvasively to exclude a significant femoral–radial pressure gradient. The presence of a large gradient may reflect impaired cerebral circulation and would be an indication for maintaining higher femoral pressures throughout the procedure.

Effects of chronic treatment by amiodarone on transmural heterogeneity of canine ventricular repolarization in vivo: interactions with acute sotalol.

The present study was designed to examine the effects of chronic amiodarone on the different ventricular cell subtypes in situ and to evaluate its interactions with sotalol. Three groups of dogs were studied. Group I (n = 8) received no treatment. Group II (n = 7) and group III (n = 8) received, respectively, 100 and 200 mg amiodarone orally twice a day for 6 weeks to 8 months. In vivo studies were performed under halothane anesthesia 14 h after the last administration of amiodarone. Three leads ECG, femoral blood pressure and left ventricular intramural monophasic action potentials (MAP) were continuously recorded. Bradycardia was obtained by clamping the sinus node and beta-blockade and the heart was driven by atrial pacing. Three weeks before the in vivo experiments, the cellular electrophysiologic properties of right ventricular tissues obtained by cardiac biopsy in six treated and six control dogs were studied with standard microelectrodes. Amiodarone produced a dose-dependent decrease in plasma levels of triiodothyronine (T3; 5.9 +/- 0.4 pM in control dogs, 3.1 +/- 0.2 pM in group III, P < 0.001) without affecting thyroxine (T4). Under anesthesia, the QT interval was 14% larger in group III compared to group I at a paced cycle length (PCL) of 1500 ms (P < 0.05). This is consistent with the 10% increase in endocardial MAP duration in group III at the same PCL (P < 0.05). There was no significant increase in transmural dispersion of MAP duration. In group I, sotalol induced a significant reverse use-dependent increase in MAP duration. This effect was reduced in group II and completely suppressed in group III. Amiodarone prevented the sotalol-induced increase in transmural dispersion of ventricular repolarization which was 69 +/- 12 ms in untreated dogs, 41 +/- 8 ms in group II (P < 0.05) and 34 +/- 8 ms (P < 0.05) in group III at PCL = 1500 ms. Amiodarone also prevented the sotalol-induced ventricular tachyarrhythmias. In vitro, the action potential duration was longer in amiodarone-treated dogs that in control ones (208 +/- 5 ms versus 188 +/- 9 ms at PCL = 1000 ms, P < 0.05). The sotalol-induced prolongation of repolarization was reduced in amiodarone-treated dogs. Chronic treatment of dogs with amiodarone induced a moderate prolongation of the QT interval and MAP duration without affecting transmural dispersion of repolarization and inhibited the effects of acute sotalol, including the prolongation of repolarization, the increase in transmural dispersion of repolarization and the induction of arrhythmias.