Intraosseous hypertension and venous congestion in osteonecrosis of the knee

To determine whether an angiogenic factor affects the pathogenesis of the idiopathic osteonecrosis of the medial femoral condyle, intraosseous pressure and venogram in 11 knees with osteonecrosis were compared with intraosseous pressure and venogram in 11 knees with the medial type of osteoarthritis. Patients were matched by age, gender, obesity index, blood pressure, tibiofemoral angle, and clinical evaluation. The intraosseous pressure of the medial condyle of the knees with osteonecrosis (62.8 +/- 27.3 mm Hg) was significantly higher than that in the lateral condyle of the knees with osteonecrosis (25.4 +/- 18.9 mm Hg) and those of both condyles of the knees with osteoarthritis (medial, 31.6 +/- 17.4 mm Hg; lateral, 29.5 +/- 11.0 mm Hg). In contrast, there was no significant difference in the pressure between the medial and lateral condyles of the knees with osteoarthritis. Venography showed a marked disturbance of venous drainage in all patients with osteonecrosis. In addition, the average clearance time of the medium in the medial femoral condyle was significantly more prolonged in patients with osteonecrosis (17.7 +/- 6.1 minutes) than in patients with osteoarthritis (5.5 +/- 1.6 minutes). These data support the hypothesis that venous stasis within the medullar canal in the condyle increases intraosseous pressure and decreases arteriovenous pressure difference, leading to osteonecrosis.     

Bone marrow fat cell enlargement and a rise in intraosseous pressure in steroid-treated rabbits with osteonecrosis.

The etiology of steroid-induced osteonecrosis (ON) is unclear. This study was designed to determine whether bone marrow fat cell size, intraosseous pressure, and blood flow rate differed between steroid-treated rabbits with ON and those without. Twenty-nine rabbits were intramuscularly injected once with 20 mg/kg of methylprednisolone acetate (MPSL), and five rabbits were injected once with physiologic saline (PS) as a control. Intraosseous pressure and blood flow rate in the proximal femur were determined before and at 2 weeks after the injection. After these measurements, both femora and humeri were histopathologically examined for the presence of ON, and size of bone marrow fat cells were morphologically examined. At 2 weeks after steroid injection, the intraosseous pressure was significantly higher in rabbits with ON than in those without (p = 0.0251), and the blood flow rate had decreased significantly more in rabbits with ON than in those without (p = 0.0051). The size of the bone marrow fat cells was significantly (p = 0.0004) larger in rabbits with ON (diameter, 63.5 +/- 5.8 microm) than in those without (diameter, 53.3 +/- 6.9 microm). Injection of PS (5 rabbits), 1 (10 rabbits), 5 (10 rabbits), and 20 (10 rabbits) mg/kg of body weight of MPSL showed that a larger dose of steroid increased both fat cell size and prevalence of ON. These results suggest that bone marrow fat cell enlargement and a rise in intraosseous pressure may be important when considering the pathophysiology of steroid-induced ON in rabbits.     

Endothelial control of long bone vascular resistance.

This in vitro study investigates whether intraosseous endothelial cells can regulate long bone blood flow by secretion of vasodilator prostaglandin and EDRF (endothelium-derived relaxing factor). Canine tibia were perfused through the nutrient artery at a constant flow rate, and the increases in perfusion pressure caused by standard doses of norepinephrine were recorded first under control conditions and then during acetylcholine infusion. Acetylcholine attenuated the norepinephrine pressure responses (-62 +/- 3%). This attenuating effect of acetylcholine was partially abolished by inhibition of prostaglandin synthesis (-20 +/- 6%) and completely abolished by inhibition of EDRF synthesis (+73 +/- 43%) or combined inhibition of prostaglandin and EDRF synthesis (+134 +/- 30%). These results are statistically significant (p less than 0.0001) and suggest that both EDRF and vasodilator prostaglandin are synthesized by intraosseous endothelial cells, and can modify long bone vascular resistance. Thus, as in other organs, intraosseous endothelial cells may provide bone with an autoregulatory control mechanism and enable it to respond to a diverse group of vasodilator stimuli.     

Intracranial venous hypertension and the effects of venous outflow obstruction in a rat model of arteriovenous fistula

A model of rat arteriovenous fistula (AVF) was created using a proximal common carotid artery to distal external jugular vein anastomosis. Anatomical dissections revealed that the external jugular vein is the primary vessel draining intracranial venous blood. Physiological measurements were made with the AVF open and closed, and during venous outflow occlusion of the contralateral external jugular vein. Opening the AVF increased torcular pressure from 6.5 +/- 0.6 to 13.5 +/- 1.1 mm Hg and decreased mean arterial pressure from 82.7 +/- 1.8 to 62.8 +/- 1.8 mm Hg (both P less than .05), decreasing cerebral perfusion pressure from 76.2 +/- 1.7 to 49.3 +/- 2.2 mm Hg (P less than .05). Middle cerebral artery blood flow velocity (MCA BFV) decreased from 6.8 +/- 1.1 to 4.2 +/- 0.7 cm/s (P less than 0.05). In rats with an AVF, occlusion of venous outflow increased torcular pressure to 34.8 +/- 3.1 mm Hg (P less than 0.05), MCA BFV decreased to 1.8 +/- 0.5 cm/s (P less than 0.05), and severe ischemic changes were seen on the electroencephalogram. Under this condition, torcular pressure and systemic arterial pressure had a positive linear relationship (P less than 0.05), whereas in control rats torcular pressure and arterial pressure had no relationship. Restoration of cerebral perfusion pressure by release of venous outflow occlusion and AVF closure transiently increased MCA BFV to 69% above baseline (P less than 0.05). Histological examination 1 week after permanent venous outflow occlusion revealed venous infarction, subarachnoid hemorrhage, and severe brain edema in rats with an AVF but not in control rats without an AVF. This model of cerebrovascular steal with venous hypertension reproduces both hemodynamic and hemorrhagic complications of human AVF and emphasizes the importance of venous outflow obstruction and venous hypertension in the pathophysiology of these lesions.     

Adenosine for controlled hypotension: systemic compared with intracoronary infusion in dogs.

We hypothesized that either through local myocardial or systemic effects, adenosine could be used to control hypotension during ischemia. Therefore, we compared the effects of systemic with intracoronary infusion of adenosine on myocardial hemodynamics and metabolism during ischemia in 27 dogs. Left anterior descending artery (LADa) flow was measured and the LADa constricted by a micrometer to restrict resting flow by 50%, 75%, and 100%. Adenosine was infused either systemically (n = 9), to maintain mean aortic pressure at 50-60 mm Hg, or directly into the LADa (n = 9), to create maximal coronary hyperperfusion; no adenosine was infused in the control group (n = 9). With systemic adenosine, during each constriction aortic pressure, left ventricular first derivative (LV dP/dt), and heart rate (HR) decreased: aortic pressure by 56.1% +/- 2.9% (mean +/- SEM), LV dP/dt by 36.2% +/- 2.2%, systemic resistance by 42.7% +/- 5%, and HR by 38.7% +/- 3% during 50% constriction (P less than 0.05 for each variable). Intracoronary adenosine decreased only aortic pressure, LV dP/dt, and HR, all to a lesser extent: aortic pressure by 5% +/- 2.8%, LV dP/dt by 15% +/- 1.2%, and HR by 4.6% +/- 1.7% (P less than 0.05, compared with systemic adenosine for each variable). With systemic adenosine only in the nonischemic area, regional myocardial blood flow increased and remained high, from 224.6 +/- 65.2 to 342 +/- 46.2 mL.min-1.100 g-1 during 50% constriction (P less than 0.05); with intracoronary adenosine, ischemic zone regional myocardial blood flow increased, but not consistently. In the ischemic area, O2 consumption was less with than without systemic adenosine; also, lactate flux production was less positive (-60.2 +/- 37.6 compared with 80.3 +/- 20.2 mmol.min-1.100 g-1 x 10(-3) during 50% constriction; P less than 0.05). Systemic infusion of adenosine during coronary hypoperfusion improves regional metabolism during ischemia and, thus, may mitigate myocardial ischemia. The mechanism by which systemic infusion improves metabolic status may be by decreases in both systemic pressure and systemic vascular resistance.     

The variable outflow resistance catheter: a new method to measure bladder pressure noninvasively

PURPOSE: In a previous study an external condom catheter was used to measure noninvasively bladder pressure during interruption of the flow rate. The pressure increase in the condom sometimes caused a sphincter contraction that made bladder pressure measurement unreliable. Therefore, we developed a new variable outflow resistance catheter to measure noninvasively bladder pressure without interrupting the flow rate. MATERIALS AND METHODS: The new catheter consists of an incontinence condom connected to a set of various outflow tubes and a pressure transducer. A remotely controlled pneumatic valve was fitted over each tube to interrupt flow through it. We measured isovolumetric pressure, maximum flow rate, and pressure and flow rates at various outflow resistances in 9 healthy male volunteers. RESULTS: We derived a mathematical equation to estimate isovolumetric pressure from the pressure and flow rate values measured at various outflow resistances. The difference in the estimated and truly measured mean isovolumetric pressures plus or minus standard deviation was 0 +/- 6 cm. water. CONCLUSIONS: The new variable outflow resistance catheter may be used to measure isovolumetric bladder pressure noninvasively without interrupting the flow rate. It has been previously shown that a combination of this pressure and a separately measured maximum flow rate may be used to diagnose bladder outlet obstruction noninvasively.     

Quantitation of vascular outflow by measurement of impedance

One of the most important determinants of graft patency is the degree and character of vascular outflow. This study was designed to evaluate input impedance as a functional assessment of the outflow bed of vascular grafts. Four distinct outflow environments were created for external jugular vein conduits in 42 New Zealand white rabbits. Vein grafts (n = 14) were fashioned as end-to-side common carotid interposition bypass grafts. Arteriovenous fistulas (n = 15) were created by side-to-side anastomosis of the distal common carotid artery and linguofacial vein. Arteriovenous fistulas with outflow obstruction (n = 7) were fistulas with a metal clip partially obstructing the distal outflow channel (1 mm lumen). Vein graft/arteriovenous fistula combinations (n = 6) consisted of a vein graft and arteriovenous fistula in series. Pressure and flow in the external jugular vein were measured, and input impedance spectra were calculated by Fourier methods. By use of a PC-based acquisition and processing system, impedance results for 20 cardiac cycles could be obtained in approximately 10 minutes. The results revealed that vein grafts typically demonstrated high resistance to steady state flow (Rin = 235 +/- 50 x 10(3) dyne . sec/cm-5) and steadily decreasing impedance to pulsatile flow resulting in a characteristic impedance (Z0; average of fourth to tenth harmonics) of 35.5 +/- 8.0 x 10(3) dyne . sec/cm-5. Phase angle values were usually negative, especially at low harmonics (first harmonic phase angle = -1.11 +/- 0.10 radians) indicating that flow led pressure. In contrast, arteriovenous fistula Rin was minimal (6.3 +/- 1.4 x 10(3) dyne . sec/cm-5; p less than 0.05 compared to vein graft, and the impedance was flat across the frequency spectrum (Z0 = 8.5 +/- 1.5 x 10(3) dyne . sec/cm-5; p less than 0.05) with pressure and flow nearly in phase (first harmonic phase angle = -0.05 +/- 0.10 radians). Creation of outflow obstruction in arteriovenous fistulas resulted in significantly elevated Rin (136 +/- 41 x 10(3) dyne/sec . cm-5; p less than 0.05 compared to arteriovenous fistula and Z0 (23 +/- 9 x 10(3) dyne . sec/cm-5, p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)     

The contribution of valves to saphenous vein graft resistance

Saphenous vein resistance influences graft flow rates and may affect graft patency in lower limb revascularization. To quantitate specifically the contribution of saphenous vein valves to this resistance, 10 human saphenous veins (mean length 68 cm, diameter 0.42 mm, and 5.2 valves per vein) were perfused with water under carefully controlled pressure gradients designed to simulate different peripheral resistances in the outflow bed. The Reynolds number was maintained at 350 to 600, within the physiologic range for in vivo grafts. Veins were perfused under both venous (10 mm Hg) and arterial (100 mm Hg) mean pressures to determine the effects of distension on the overall resistance of the conduit. The valves were bisected according to Leather's techniques and flow was measured in both directions, antegrade (simulating "reversed" grafts) and retrograde (simulating "in situ" grafts). Data (mean +/- standard error) were normalized to the baseline flow for each vein with intact valves and expressed as a percentage change. Data were analyzed by means of Student's t test (p less than 0.05). Baseline antegrade flow with intact valves averaged 71.0 +/- 3.0 ml/min at pressure gradients (delta P) of 10 mm Hg and 95.0 +/- 2.6 ml/min for delta P = 20 mm Hg. After valve incision, antegrade flow (reversed) increased an average of 29% at both pressure gradients. Retrograde flow (in situ) through the bisected valves was only 19% greater than baseline antegrade flow and was significantly less than antegrade flow through bisected valves. The difference is explained by theoretic considerations of stenosis area and orifice shape. The increases in flow did not correlate with vein length or diameter, nor did flow change with different distension pressures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rate of Coronary Flow Adaptation in Response to Changes in Heart Rate before and during Anesthesia for Coronary Artery Surgery

Background: The rate of adaptation of coronary blood flow in response to stepwise changes in heart rate (HR) has been extensively studied in dogs and goats to improve our understanding of the dynamics of coronary regulation processes and their pathophysiology and to obtain time constants for mathematical modeling of the coronary regulation. However, little is known about the dynamic characteristics of coronary flow adaptation in humans. In patients undergoing coronary artery surgery, we investigated the rate of coronary adaptation in response to stepwise changes in HR, in the awake and anesthetized states.

Methods: In 11 patients with stable coronary artery disease, arterial blood pressure, right atrial pressure, and coronary sinus blood flow, measured by continuous thermodilution, were calculated per beat. The ratio of beat-averaged arterial blood pressure minus right atrial pressure and coronary sinus blood flow was calculated to obtain an index of coronary resistance. The rate of change of coronary resistance index was quantified by t50, defined as the time required to establish 50% of the total change in coronary resistance index. Responses of coronary resistance index after HR changes, before and after induction of anesthesia, were compared. The anesthesia technique consisted of 100 micro gram *symbol* kg sup -1 fentanyl and 0.1 mg *symbol* kg sup -1 pancuronium bromide in combination with oxygen in air ventilation (FIO2 = 0.5).

Results: In the awake situation, t50 values of the dilating and constricting responses, induced by an increase and a decrease in HR were 5.0+/-2.1 (SD) s (range 2.6-9.0 s) and 5.7+/-1.2 s (range 4.1-7.8 s), respectively. During fentanyl/pancuronium anesthesia, the rate of coronary flow adaptation was significantly slower, with t50 values of 10.2+/-2.1 s (range 7.7-13.1 s) after an HR step-up and 9.8+/-2.1 s (range 6.6-13.2 s) after an HR step-down. Compared to the awake situation, arterial blood pressure was significantly reduced during anesthesia, but coronary vascular resistance remained unchanged. This implies that the steady-state static regulation of coronary blood flow had not changed.     

Quantitative assessment of outflow resistance in lower extremity arterial reconstructions

Graft patency is thought to correlate with resistance in the runoff bed or outflow resistance. However, accurate measurement of this parameter has been difficult. A simple and reproducible method for direct measurement of outflow resistance following completion of the distal anastomosis of a bypass graft has been developed. This method employs injection of a fixed amount of normal saline through the proximal end of the graft and measurement of the resulting integrated pressure increment by an analog computer. Division of this pressure integral by the volume injected is a measure of the outflow resistance expressed in resistance units (mm Hg/ml/min). The median outflow resistance in 31 femoropopliteal bypasses was 0.29 units with a range of 0.08-1.38 units. The median outflow resistance in 33 femorodistal bypasses was 0.7 units with a range of 0.18-2.34 units. All bypasses with an outflow resistance of 1.1 units or less remained patent for 3 months. There were 51 grafts in this group (30 femoropopliteal; 21 femorodistal) and their outflow resistance ranged from 0.08 to 1.1 units. All bypasses with an outflow resistance of 1.2 units or higher thrombosed within the first postoperative month. There were 13 grafts in this group (1 femoropopliteal; 12 femorodistal) and their outflow resistance ranged from 1.2 to 2.38 units. Eight of the 13 grafts that failed originally were subjected to thrombectomy, which was uniformly unsuccessful. Although this method does not yet allow bypass surgery to be denied to any patient, it does define a group of patients in whom thrombectomy will not be effective and should not be attempted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical and therapeutic concepts in ischemic femur head necrosis

Bone ischaemia can result from four mechanisms: (1) interruption of arterial inflow (e.g. after femoral neck fracture), (2) occlusion of venous outflow (possibly due to capsular distension), (3) intravascular arteriolar occlusion (as in sickle cell disease); (4) extravascular sinusoidal tamponade (e.g. in Gaucher's disease). Osteonecrosis following high-dosage corticosteroid administration or alcohol abuse could, theoretically, be due to either intravascular fat embolism or sinusoidal tamponade resulting from the marked fat deposition in the marrow. It is proposed here that, except in traumatic osteonecrosis, vascular insufficiency is part of a cycle of events resembling the familiar soft tissue compartment syndrome of the forearm or leg; no matter whether it started with venous stasis, arteriolar occlusion or capillary tamponade, the result is a diffuse and self-enhancing ischaemia involving all three haemodynamic abnormalities in a vicious circle. The very earliest stage of "idiopathic" osteonecrosis is characterised chiefly by marrow changes; for some (undetermined) period the ischaemic effects are potentially reversible-provided the vicious circle is broken by relieving the high intraosseous pressure. Effective management involves: (a) early diagnosis by MR imaging, measurement of intraosseous pressure and venography: (b) decompression of the bone, and (c) elimination of the etiological factor. Later stages of osteonecrosis cannot be treated by decompression and will need realignment osteotomy, prosthetic replacement or arthrodesis.     

An ex-vivo evaluation of vascular catheters for continuous hemofiltration

OBJECTIVES: To measure outflow and inflow hydraulic resistance in double-lumen catheters used for hemofiltration under standardized laboratory conditions. SETTING: ICU Laboratory of tertiary unit. METHODS: Heparinized spent red cells diluted in polygeline solution to a constant hematocrit of 32% at 37 degrees C were pumped using a standard Prisma M60 circuit through several hemofiltration catheters. Blood pump speed was increased and decreased in steps of 30mL/min (30, 60, 90, 120, 150, and 180 mL/min) and catheter outflow and inflow pressures recorded and used to define the pressure flow relationship (line of hydraulic resistance) for each. RESULTS: Double-lumen catheters posed different resistances to outflow or inflow. Among the < 15 cm long catheters, the 11.5 Fr Quinton-Mahurkar (0.56 mmHg/mL/min) catheter offered the least resistance to outflow, while the Medcomp 11.5 Fr catheter offered the least resistance to inflow (0.78 mmHg/mL/min). Among the >19 cm long catheters, the 13.5 Fr Vascath Niagara catheter showed the lowest blood flow resistance to both outflow (0.63 mmHg/ mL/min) and inflow (0.83 mmHg/mL/min). Longer catheters did not pose statistically greater resistance to both outflow and inflow. Resistance to inflow was consistently greater than resistance to outflow (p = 0.003). Overall, the Prisma M60 blood circuit alone accounted for 40% of the total extracorporeal circuit blood flow resistance. CONCLUSIONS: Proprietary hemofiltration catheters have variable resistance to blood flow under standard ex-vivo conditions. This ex-vivo information might be useful to clinicians in guiding their choice of catheters for clinical use.     

An experimental study of the influence of positive end-expiratory pressure for a bidirectional cavopulmonary shunt

In 8 mongrel dogs (weight 9-13 kg), we created a bidirectional cavopulmonary shunt through 4th intercostal thoracotomy. Positive end-expiratory pressure (PEEP) was added from 0cmH2O to 16cmH2O at the steps of 2cmH2O. The heart rate (HR), central venous pressure (CVP), pulmonary artery pressure (PAP), femoral artery pressure (FAP), pulmonary vascular resistance index (PVRI), and systemic vascular resistance index (SVRI) were measured as parameters of hemodynamics. Cardiac output (CO), pulmonary artery flow at proximal and distal site of this shunt (D-SF, P-SF) were measured using a magnetic flow meter. Blood gas analysis (PH, PaO2, PaCO2, HCO3-) were performed at the same time. HR had no significant change. CVP, PAP, PVRI, SVRI increased significantly (p less than 0.05, p less than 0.05, p less than 0.05, p less than 0.05) at 2cmH2O (9.2 +/- 2.5 mmHg), 10cmH2O), (29.3 +/- 5.5 mmHg), 4cmH2O (287 +2- 56 dyne.sec.cm-5.m2), and 8cmH2O (1298 +/- 156 dyne.sec.cm-5.m2) compared with 0cmH2O (87.3 +/- 2.6 mmHg, 26.8 +/- 3.4 mmHg, 240 +/- 29 dyne.sec.cm-5.m2, 1136 +/- 176 dyne.sec.cm-5.m2). FAP, CO, D-SF, P-SF decreased significantly (p less than 0.01, p less than 0.05, p less than 0.01, p less than 0.05) at 6cmH2O (129 +/- 7 mmHg), 2cmH2O(0.44 +/- 0.05 L/min), 2cmH2O(449 +/- 47 ml/min), and 8cmH2O(105 +/- 17 ml/min) compared with 0cmH2O(148 +/- 11 mmHg, 048 +/- 0.06 L/min, 471 +/- 44 ml/min, 132 +/- 19 ml/min). On blood gas analysis, PaO2 increased significantly (p less than 0.05) from 2cmH2O PEEP except PH, PaCO2, HCO3-. A mechanism for decline in D-SF was considered of being a secondary effect due to increase in CVP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Outflow resistance and early occlusion of infrainguinal bypass grafts

Distal outflow vascular resistance (VR) has been measured intra-operatively during 67 infrainguinal bypass procedures to establish whether it might have a role as a predictive test for early graft thrombosis. The graft outflow was popliteal artery above the knee (48), popliteal artery distal to the knee (6) or a single calf vessel (13). VR was measured before anastomosis of the graft, calculated from the relationship between pressure and flow in the outflow artery during infusion of the patient's own blood at a constant rate. VR was measured before and after vasodilation with papaverine. Primary graft patency at 30 days was documented. In the 10 limbs in which graft thrombosis occurred, VR was 1167 +/- 367 mPRU, significantly higher than VR in 57 limbs with a patent graft, 850 +/- 310 mPRU (P = 0.02, Mann-Whitney U test). After papaverine, VR was 823 +/- 368 mPRU in the limbs with a thrombosed graft, significantly higher than that of limbs with a patent graft, 463 +/- 211 mPRU (P = 0.001). VR appeared to show most promise as a predictor of early thrombosis in the group of femoro-tibial and femoro-peroneal grafts. In this group, the value of 800 mPRU after papaverine was 92% efficient and was 80% sensitive, 100% specific and had a predictive value of 100% for early thrombosis. Distal outflow VR is an important factor in early graft thrombosis and might have a practical application as a predictor of early thrombosis of femoro-distal bypass grafts.     

Arteriovenous shunting is not associated with venous congestion in bone. Knee tamponade studied with 15-microns and 50-microns microspheres in immature dogs

Blood flow in the hind-limb bones of 8 immature labrador dogs with unilateral knee joint tamponade at 75 percent of the mean arterial pressure was measured with 15-microns and 50-microns microspheres to determine whether or not arteriovenous shunting occurs in bone with venous congestion caused by increased outflow resistance. The intraosseous pressure was 43 percent of the mean arterial pressure in the experimental distal femoral epiphysis versus 14 percent in the control knee (P less than 0.001). No pressure changes were found in the distal femoral metaphysis. Regional blood flow with 15-microns microspheres decreased centrally in the distal femoral epiphysis and increased centrally in the proximal tibial epiphysis. Metaphyseal blood flow was largely unchanged. A net shift in the preferred embolization site of 50-microns microspheres relative to that of 15-microns microspheres from central to peripheral regions occurred within both juxtaarticular epiphyses, indicating arteriolar vasodilation, but the relation between the uptake of the two microsphere sizes was unchanged when the epiphyses and other bony flow compartments were viewed in toto. The result speaks against the hypothesis of arteriovenous shunting in intraosseous hypertension.     

体外循环与非体外循环冠状动脉旁路移植术患者桥血流的对比研究

目的比较非体外循环和体外循环下冠状动脉旁路移植术(CABG)的左乳内动脉(LIMA)和大隐静脉(SV)桥血流的变化。方法将547例行CABG患者分为非体外循(OPCAB)组(403例)和体外循环(CCABG)组(144例)。常规用LIMA与左前降支(LAD)吻合,其余靶血管使用SV吻合。于全部吻合口吻合完毕血流动力学稳定情况下,用即时血流测量仪(TTFM)直接测量并记录桥血流各项参数。结果搏动指数(PI值)、无效血流率及舒张期峰流量,LIMA桥OPCAB组分别为2.7±1.8,(2.2±4.3)%,(46.8±2.7)m l/m in,CCABG组分别为2.8±2.0,(3.4±3.1)%,(52.8±3.7)m l/m in;SV桥,OPCAB组分别为2.8±0.1,(1.8±0.3)%,(85.8±3.2)m l/m in,CCABG组分别为2.6±0.2,(1.3±0.2)%,(93.9±5.6)m l/m in,两组比较差异均无统计学意义(P均>0.05);平均流量及收缩期峰流量,CCABG组[SV桥(62.9±3.9)与(106.9±7.3)m l/m in,LIMA桥(32.5±23.5)与(41.6±4.4)m l/m in]均大于OPCAB组[SV桥(47.2±1.7)与(58.0±2.7)m l/m in,LIMA桥(26.5±19.9)与(27.0±1.6)m l/m in],差异有统计学意义(t=6.61,6.77,5.16,5.96,P均<0.01);CCABG组血管阻力LIMA桥与SV桥分别为(3.6±0.3)与(1.6±0.2)mm Hg.m l-1.m in-1,小于OPCAB组的(4.7±0.2)与(2.7±0.1)mm Hg.m l-1.m in-1,两者比较差异有统计学意义(t=4.32,P均<0.01)。结论CCABG组与OPCAB组对比,桥血管的通畅率无显著性差别。     

Slowing of the heart during hypotension in major abdominal surgery

Heart rate (HR) and mean arterial blood pressure (MBP) were studied during abdomino-perineal resections of the rectum under neurolept anesthesia in order to observe HR deviations due to hypovolemic hypotension. Of the 65 patients followed, 18 developed a systolic BP under 100 mmHg. Their blood loss (37 +/- 9 ml/kg, mean +/- s.e. mean) was higher than that of the normotensive control group (20 +/- 2 ml/kg, P less than 0.01), the urine production lower (8 +/- 1 versus 10 +/- 3 ml/kg, P less than 0.01) and blood transfusions amounted to 40 +/- 8 versus 24 +/- 2 ml/kg (P less than 0.01). In the hypotensive patients a decrease in MBP from 108 +/- 3 to 94 +/- 3 mmHg was accompanied by a simultaneous increase in HR from 81 +/- 3 to 91 +/- 3 beats/min (P less than 0.05). However, during the hypotensive incident where the MBP averaged 69 +/- 4 mmHg, HR decreased temporarily to 75 +/- 3 beats/min (P less than 0.001). After MBP was restored to 94 +/- 3 mmHg using volume repletion, HR increased to 95 +/- 3 beats/min (P less than 0.001). The results demonstrated a temporary slowing of HR in anesthetized, bleeding and hypotensive patients.     

Effects of catheter size on urodynamic measurements in men undergoing elective prostatectomy

Thirty men undergoing prostatectomy for symptoms of bladder outflow obstruction and low measured maximum flow rates (20 before and 10 after operation) were studied by means of urodynamic investigation. Paired studies were performed on each patient using a large catheter assembly (4 and 10 F) and a small catheter assembly (epidural line, outside diameter 1.1 mm). The order in which the studies were performed was varied randomly. Detrusor pressure at maximum flow rate was significantly greater in the large catheter study (73 +/- 30 cm H2O) than in the small catheter study (65 +/- 27 cm H2O; P less than 0.003). The maximum flow rate was significantly smaller in the large catheter study (8.9 +/- 9.5 ml/s) than in the small catheter study (12 +/- 7 ml/s; P less than 0.001). The increase in detrusor pressure at maximum flow that was noted during the large catheter study was confirmed in the 20 men who were studied before prostatectomy (mean increase 11 +/- 11 cm H2O; P less than 0.001) but no difference was found between the two methods in the 10 men studied after prostatectomy (50 +/- 19 cm H2O and 49 +/- 15 cm H2O). Using a large catheter assembly to perform urodynamic investigations has the advantage that repeated studies can be performed without recatheterisation, but it has the disadvantage of producing a small increase in detrusor pressure at maximum flow in men with symptoms of bladder outflow obstruction. Few errors in diagnosis should result, however, if laboratories using such catheters are aware of this effect and establish their own limit of normal for voiding pressures.     

Regional myocardial blood flow in left ventricular hypertrophy. An experimental investigation in Newfoundland dogs with congenital subaortic stenosis

To test the hypothesis that left ventricular hypertrophy (LVH) may predispose the subendocardium to ischemia, we studied regional myocardial blood flow in dogs with the fibrous ring form of subvalvular aortic stenosis and concentric LVH. Radioactive microspheres, 9 +/- 1 mu in diameter, were used. Eleven dogs with LVH (left ventricular body weight ratio of 6.35 +/- 0.46 gm/kg [mean +/- SEM] and peak left ventricular outflow gradient of 51 +/- 7 mm Hg) were compared to 12 normal dogs (left ventricular/body weight ratio of 3.41 +/- 0.12 gm/kg and peak left ventricular outflow gradient of 6 +/- 3 mm Hg). The two groups of dogs were subjected to comparable experimental interventions including (1) tachycardia produced by atrial pacing (221 +/- 4 beats/min), (2) ascending aortic constriction producing systolic hypertension (212 +/- 5 mm Hg), and (3) creation of an aortic-right atrial fistula lowering diastolic blood pressure (38 +/- 3 mm Hg). Basal regional myocardial blood flow was distributed similarly for LVH and normal dogs (endocardial/epicardial ratio = 0.90 +/- 0.05 and 0.94 +/- 0.03, respectively). During experimental interventions, regional blood flow remained equal to all myocardial layers in normal dogs; however, the endocardial/epicardial ratio diminished in LVH dogs during atrial tachycardia to 0.61 +/- 0.08, during systolic hypertension to 0.68 +/- 0.06, and during diastolic hypotension to 0.50 +/- 0.09. When the diastolic/systolic pressure time index ratio (DPTI/SPTI) was less than 0.8, subendocardial ischemia occurred in dogs with LVH (endocardial/epicardial ratio = 0.66 +/- 0.04) but not in normal dogs (endocardial/epicardial ratio = 0.92 +/- 0.03) (p less than 0.0001). Animals with infracoronary obstruction and LVH demonstrate greater susceptibility to development of subendocardial ischemia for identical hemodynamic interventions than do normal animals.     

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)