Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the procine kidney

Summary In a series of experiments with pigs the completely obstructed renal pelvis was filled with Ringer's lactate at a constant rate of 2 ml/min. At various pressure levels lower than 50 mm Hg the relations pressure vs infused volume and pressure vs actual intrapelvic volume were repeatedly measured. It was concluded that the measurements were reproducible and that the pelvicalyceal system is under these experimental conditions- a stable elastic unit.     

肾盂内高压灌流对肾单位结构影响的实验研究

目的建立肾盂内高压灌流的动物模型，观察肾盂内高压灌流对肾单位结构的影响，探讨经皮肾镜时肾盂内灌流的安全压力。方法建立活体猪的肾盂内高压灌流动物模型（n=10），在无加压灌流至40．00kPa（1kPa=7．5mmHg）高压灌流间，每6．67kPa作为一个压力级别灌流10min，穿刺获取肾实质组织，分别在光镜（HE染色、六胺银染色）及透射电镜下观察各级压力梯度下肾小球、肾小囊及近曲肾小管的形态变化。结果肾盂内灌流压在6．67—20．00kPa时，肾单位各结构保持完整；当肾盂内灌流压达到26．66kPa，透射电镜下可见肾近曲小管上皮细胞细胞器扩张，胞质内空泡形成，微绒毛紊乱、脱落等细胞受损表现；当肾盂内灌流压达33．33～40．00kPa，可观察到肾小囊基底膜断裂、肾小囊壁破裂，红细胞及蛋白质漏入肾小囊，近曲小管上皮细胞微绒毛脱落、胞质内大量空泡形成，细胞膜及细胞器膜破裂等结构损伤表现。结论肾盂内灌流压力超过26．66kPa可对肾单位造成结构破坏，进行经皮。肾镜手术过程中，应注意保持肾盂内压不超过26．66kPa，避免对肾单位造成结构破坏。     

Cerebral blood flow at constant cerebral perfusion pressure but changing arterial and intracranial pressure: relationship to autoregulation

Therapeutic agents for reducing raised intracranial pressure (ICP) may do so at the expense of reduced mean arterial pressure (MAP). As a consequence, cerebral perfusion pressure (CPP) = (MAP - ICP) may not improve. It is unknown whether the level of MAP alters cerebral blood flow (CBF) when MAP and ICP change in parallel so that CPP remains constant. This study investigates CBF at a constant CPP but varying levels of MAP and ICP in 12 anaesthetized cats. CBF was studied at three levels of CPP: 60 (n = 4), 50 (n = 4), and 40 mm Hg (n = 4) under conditions of both intact and impaired autoregulation. At CPP levels of 50 and 60 mm Hg, when autoregulation was intact, CBF remained unchanged. With loss of autoregulation, there was a trend for CBF to increase as MAP and ICP were increased in parallel at a CPP of 50 and 60 mm Hg, although the relationship did not achieve statistical significance. Absolute CBF levels were, however, significantly different between the autoregulating and nonautoregulating groups (p <0.001). At a CPP of 40 mm Hg, CBF showed a linear correlation with blood pressure (BP) (r = 0.57, p <0.05). These results demonstrate that when autoregulation is impaired, there is a functional difference between autoregulating and nonautoregulating cerebral vessels despite similar MAP and CPP. These results also show that at a CPP of 40 mm Hg when autoregulation is impaired, CBF depends more on arterial driving pressure than on CPP.     

微创经皮肾输尿管镜碎石术中肾盂内压与术后康复的关系

目的介绍微创经皮肾输尿管镜碎石术（MPCNL）中肾盂内压力监测的方法,观察肾盂内灌注压力对术后康复的影响。方法用自制连接器密闭连接F5输尿管导管的尾端与无菌的换能器,建立肾盂内压测定装置,对46例肾结石患者术中即时监测肾盂内压,统计术后早期并发症,如发热、疼痛指数及血红蛋白的下降值,并观察住院时间和远期结石清除率,探讨其与压力变化的关系。高压冲洗组（n=20）为术中肾盂内压力≥30mm Hg（1mm Hg=0．133 kPa）,持续时间≥10min,其余情况归入低压冲洗组（n=26）。结果术中肾盂压力为3～50mmHg。高压冲洗组术后发热、血红蛋白的下降值、疼痛指数和平均住院时间均高于低压冲洗组（P〈0．05）,两组间术后1个月结石清除率差异无统计学意义（P〉0．05）。结论MPCNL术中常规监测肾盂内压变化,控制术中压力≥30mm Hg持续时间〈10min,以获得平稳的术后康复,减少术后并发症的发生,可有效缩短住院时间。     

Estimation of intra-abdominal pressure by bladder pressure measurement: validity and methodology

BACKGROUND: Increased intra-abdominal pressure (IAP) is an adverse complication seen in critically ill, injured, and postoperative patients. IAP is estimated via the measurement of bladder pressure. Few studies have been performed to establish the actual relationship between IAP and bladder pressure. The purpose of this study was to confirm the association between intravesicular pressure and IAP and to determine the bladder volume that best approximates IAP. METHODS: Thirty-seven patients undergoing laparoscopy had intravesicular pressures measured with bladder volumes of 0, 50, 100, 150, and 200 mL at directly measured intra-abdominal pressures of 0, 5, 10, 15, 20, and 25 mm Hg. Correlation coefficients and differences were then determined. RESULTS: Across the IAP range of 0 to 25 mm Hg using all of the tested bladder volumes, the difference between IAP and intravesicular pressures (bias) was -3.8 +/- 0.29 mm Hg (95% confidence interval) and measurements were well correlated (R2 = 0.68). Assessing all IAPs tested, a bladder volume of 0 mL demonstrated the lowest bias (-0.79 +/- 0.73 mm Hg). When considering only elevated IAPs (25 mm Hg), a bladder volume of 50 mL revealed the lowest bias (-1.5 +/- 1.36 mm Hg). A bladder volume of 50 mL in patients with elevated IAP resulted in an intravesicular pressure 1 to 3 mm Hg higher than IAP (95% confidence interval). CONCLUSION: Intravesicular pressure closely approximates IAP. Instillation of 50 mL of liquid into the bladder improves the accuracy of the intravesicular pressure in measuring elevated IAPs.     

乙醇法监测经皮肾镜取石术中灌流液吸收量的临床研究

目的 探讨减少经皮肾镜取石术(PCNL)中灌流液吸收量的途径.方法 PCNL患者20例.男13例,女7例.平均年龄40(25～56)岁.结石最大径平均25(18～36)mm.术中使用乙醇法监测灌流液吸收量,同时监测心率、平均动脉压,记录术中灌流液用量、手术时间和肾盂内压力,比较手术前后血红蛋白、血清Na+、K+、Cl-浓度、二氧化碳结合力及SCr值.结果 20例患者术中灌流液吸收量50.2～685.0(202.2±145.8)ml.手术前后心率、平均动脉压、Na+、K+、Cl和SCr值差异无统计学意义(P>0.05),术前血红蛋白浓度为(142.6±15.6)g/L,二氧化碳结合力(26.4±2.0)mmol/L,术后分别为(130.4士16.3)g/L、(24.1±3.2)mmol/L,手术前后比较差异有统计学意义(P<0.05).肾盂内压>30 mm Hg(1 mm Hg=0.133 kPa)累计时间>10 min,或手术时间>1 h,或灌注液用量>10000 ml者平均灌流液吸收量分别为381.1、301.6、261.6 m1,高于累计时间<10 min,手术时间<1 h,灌注液用量<10000 ml者的142.9、136.4、130.2 ml,差异有统计学意义P<0.05).结论 乙醇法监测灌流液吸收量简便易行、安全有效,适用于心、肺、肾脏均功能差,易因灌流液吸收导致容量超负荷的PCNL病例.     

利用外支架提高牛颈静脉带瓣管道机械性能

目的 探讨提高肺动脉移植物牛颈静脉带瓣管道(BJVC)机械性能的外支架方法.方法 使用尼龙纤维编织人造纤维织物外支架.牛颈静脉管道经去除细胞成分后光氧化交联处理.按BJVC有、无外支架支撑分组进行体外实验比较机械性能和体内实验进行组织学观察.结果 膨胀率的计算方法为测试管道在承受一定压力前后的变化率.有外支架组BJVC(实验组)在10～60mmHg(1 mm Hg=0.133 kPa)水压范围中的膨胀形变率最高在(11.4±3.1)%.而单纯的牛颈静脉(对照组)20 mm Hg时膨胀率即达(14.8±4.7)%.在30 mm Hg的逆行水压下实验组瓣膜反流量为0,而对照组同等压力下约32ml/min.渗漏方面,实验组在60mmHg时出现1ml/min的渗漏.而对照组在20、40、60mm Hg压力下渗出量分别为1、5、13 ml/min.两组比较差异均有统计学意义.9条犬接受牛颈静脉管道移植体内实验.6个月后组织学观察见实验组尼龙纤维周围炎性细胞浸润较密集,自体细胞浸润较快.结论 外支架易制作,是完善牛颈静脉机械性能的一种较理想方法.

Abstract：

Objective To increase the mechanic characteristic of bovine jugular veins conduit (BJVC) by combined knitted stent outside made of nylon fiber. Methods Get rid of the cells of BJVC by enzymolysis, then combined a fabric stent with a acellular bovine jugular vein conduit that cross-linked dealed by photooxidation method to improve the mechanic function of BJVC. To compare the mechanical function and histology change of BJVC combined with fiber stent outside with that of BJVC only without stent. BJVC combined with fiber stent outside was divided into experiment group and the latter into control group. Two roller pumps on cardiopulmonary bypass unit were designed to simulate the pulmonary circulation. One produce the stream, and the other assist to bring a certain pressure by regulating a degree of tightness. The pressure of forward stream was used in messuring extension rate and leakage volume of two BJVC groups, and the pressure of backward stream was used in messuring the regurgitation volume. Results Set the formula to calculate the rate of variation of BJVC diameter under a certain pressure or not. The experiment group extension rate was zero under pressure of 10-20 mm Hg, about ( 7.7 ± 2.3 ) % under pressure of 40 mm Hg, until 60 mm Hg to ( 11.4 ± 3.1 ) %. While the control group reached about ( 14.8 ± 4.7 ) % at 20mm Hg already. There was no regurgitation volume of the experiment group under pressure of 30 mm Hg vs. the control group' s reached 34ml/min at 30 mm Hg while the two groups were same under pressure that lower than 20 mm Hg. When the pressure higher, the difference between the two groups more notable. There was no leakage of the BJVCs with fabric stent till pressure from 40 mmHg to 60mmHg, vs. the control group 1,5, 13 ml/min at pressure 30, 40, 60 mm Hg. Except the regurgitation and leakage volumes under pressure at 10 -20 mm Hg, as the two numerical values were both zero that can not be caculated by the statistic software, the differences of the two groups above had statistics significance. In vivo, 9 dogs received bovine jugular vein conduit transplant procedure to observe the mechanic fnction and tissue reaction. Five adopted B.JVC with stent and four just BJVC only. Six month later after the transplant procedure, there was no significant difference between the two groups but more inflaming cells than the former group, especially at the location round the nylon fibers. Through the observation in HE stain, that was considered as foreign body reaction. Conclusion Fabric stent can improve the mechanical function of BJVC and relatively easy to get.     

Hydrodynamics of the spinal epidural space in pigs determined by constant-flow methods

BACKGROUND AND OBJECTIVES: Impressive quantities of fluid can be infused into the epidural space of the spine without causing dramatic or sustained increases in pressure. The epidural space is considered "leaky," but questions remain about how fluid leaves the epidural space. We used constant-flow infusions of saline to gain insight into the hydrodynamics involved. METHODS: We infused saline at a constant rate into the lumbar epidural space of 6 anesthetized pigs while measuring pressure at the adjacent interspace. Three or 4 infusions were performed at different flow rates in each animal. RESULTS: Epidural space pressure in the absence of flow was consistently 2 to 3 mm Hg above right atrial pressure. During each infusion, pressure increased slowly to a steady plateau value between 15 and 70 mm Hg. When flow was stopped, pressure declined exponentially to the starting pressure. The presence of a plateau indicates that fluid leaving the epidural space ends up in a structure with high capacitance. Plateau pressures were linearly related to flow rate in each animal, indicating constant resistance to outflow. The flow-pressure relation showed neither a critical opening pressure nor moderating pressures with increased flow. CONCLUSIONS: Fluid leaves the porcine spinal epidural space through channels that are open at baseline rather than being recruited as epidural pressure increases. This behavior is inconsistent with the view that the epidural space behaves like a Starling resistor.     

微创经皮肾取石术中肾盂内压测量

目的 探讨微创经皮肾取石术(MPCNL)中肾盂内压测量方法及其意义.方法 通过压力传感器连接逆行置入肾盂的5Fr输尿管导管与Mindray PM9000型监护仪有创压力测量通道,实施经皮肾取石术中肾盂内压测量,增加软件模块后的测压系统每秒采集1次数据,并将数据实时导入计算机数据库.结果 共对112例MPCNL术中肾盂内压进行测量,分析了MPCNL术中肾盂内压的影响因素以及肾盂内压与术后发热的关系.结论 MPCNL术中肾盂内压总趋势小于一般所认为的引起肾实质反流的极限[30 mm Hg(1 mm Hg=0.133 kPa)].任何引起灌注液流出受阻的因素,均可引起肾盂内压增高,术者应该在术中注意调整操作手法,降低肾盂内压.术后发热与MPCNL导致的肾盂内压短暂性增高无明显相关,但总手术时间过长,肾盂内高压状态(≥30 mmHg)累积到一定限度(50 s以上),总平均肾盂内压升高(20 mm Hg以上),将引起术后发热率增加.

Abstract：

Objective To introduce a new method to measure renal pelvic pressure in vivo during minimally invasive percutaneous nephrolithotomy (MPCNL), and investigate its clinical significance.Methods Renal pelvic pressure was measured by baroceptor which was connected to Mindray PM9000 monitor IBP channel and ureteric catheter positioned in renal pelvis during MPCNL, and a computer collected the renal pelvic pressure data each second. Results Renal pelvic pressure was measured in 112 cases during MPCNL, and the influence factors of renal pelvic pressure and its correlation with postoperative fever were analyzed. Conclusion Renal pelvic pressure generally remained lower than a level to back-flow [30 mm Hg(1 mm Hg=0.133 kPa)] during MPCNL. Any factors which brought about a bad drainage would result in a temporal elevated intrapelvic pressure greater than 30 mm Hg. It's necessary for the surgeons to adjust their manipulation to keep a low renal peivic pressure. A spurt high renal pelvic pressure greater than 30 mmHg wouldn't cause a postoperative fever, while a status of renal pelvic pressure greater than 30 mmHg(longer than 50 s) or a mean renal pelvic pressure greater than 20 mmHg all through the procedure may lead to an enough back-flow, resulting in a postoperative fever.     

The effects of inflation of antishock trousers on hemodynamics in normovolemic subjects

Antishock trousers may maintain mean arterial pressure in trauma patients by increasing central blood volume and cardiac output. Hemodynamics, end-diastolic volume, stroke volume, cardiac output, and blood pressure were recorded in eight supine, healthy men in antishock trousers using two-dimensional echocardiography. Two inflation protocols were used. The antishock trousers were inflated to 50 and 100 mm Hg in a random fashion and inflation was maintained for 30 minutes before deflation. End-diastolic volume and blood pressure rose significantly (p less than 0.05) after antishock trouser inflation of 50 and 100 mm Hg. With the 50 mm Hg inflation, the stroke volume and end-diastolic volume fell below baseline over time. This did not occur with the 100 mm Hg inflation. After suit deflation, the stroke volume, end-diastolic volume, and cardiac output increased with 50 mm Hg inflation. The study shows that the antishock trousers alter several hemodynamic parameters. With lower inflation pressures, antishock trousers cause an increase in arterial pressure by increasing peripheral resistance. At higher inflation pressures, the antishock trousers increase cardiac output and as the cardiovascular system adjusts, maintain the pressure by increasing peripheral resistance.     

Systemic and renal effects of dopamine in the infant pig

Dopamine is commonly employed in the management of hypotensive patients. Although this medication increases cardiac index (CI) and renal artery (RA) flow in adults, its effect in infants has not been adequately studied. In 13 infant pigs (mean wt 3.05 ± 0.75 kg; age 3–4 weeks) CI, RA flow and systemic blood pressure (BP) were measured at varying renal artery perfusion pressures before and after the administration of dopamine. Pigs were anesthetized with ketamine, intubated, and maintained on a ventilator with succinylcholine. Jugular vein, pulmonary (Swan-Ganz), carotid, and femoral artery catheters were placed. Laparotomy was performed and RA flow was measured with an electromagnetic flow probe. A Blalock clamp was placed around the suprarenal aorta to obtain graded aortic occlusions to pressures of 80 and 50 mm Hg. Dopamine had no significant effect on the CI vs control at 5, 10, 15, 20, 25, or 50 μg/kg/min. BP increased 25 mm Hg on Dopamine (10 μg/kg/min) P > 0.05). RA flow remained stable (318 ± 74 vs 300 ± 68 ml/min) despite reduction in perfusion pressure to 80 mm Hg, suggesting an autoregulatory flow mechanism. At 50 mm Hg perfusion pressure however, RA flow decreased significantly to 220 ± 54 ml/min (P < 0.05) indicating a loss of autoregulation at lower perfusion pressures.Dopamine (10 μg/kg/min) did not change RA flow at control BP (335 ± 76 vs 318 ± 74 ml/min). At 80 mm Hg perfusion pressure however, RA flow fell from 335 ± 74 to 175 ± 50 ml/min (P < 0.001) demonstrating a suppression of renal autoregulation by dopamine. At 50 mm Hg, RA flow was markedly reduced to 22 ± 31 ml/min (P < 0.001). These data suggest: (1) dopamine has no significant effect on CI in infant pigs, (2) an RA flow mechanism is present in infant pigs which protects the kidney at reduced perfusion pressures, and (3) dopamine interferes with autoregulation and may be harmful to the infant kidney in hypotensive states.     

Effect of fibronectin-rich human cryoprecipitate on fluid volume requirements in sheep during postoperative sepsis

Septic surgical patients often require fluid administration to maintain cardiovascular stability due, in part, to the sepsis-induced increase in vascular permeability and associated plasma volume depletion. Plasma fibronectin deficiency exists in such septic patients. We determined if maintenance of fibronectin levels by administration of fibronectin-rich human plasma cryoprecipitate would lower the resuscitative fluid volume needed for support of arterial pressure in septic postoperative sheep which were experimentally depleted of plasma fibronectin. Following a 2-hr postoperative baseline period, denatured collagen (gelatin, 8.7 mg/kg), which has a high affinity for fibronectin, was infused into both control and experimental sheep in order to acutely deplete plasma fibronectin. Sheep were then challenged both intraperitoneally and intravenously with live Pseudomonas (5 x 10(10) bacteria IP; 5 x 10(9) bacteria IV). Experimentals were given fresh plasma cryoprecipitate intravenously at a dose of 4 units bolus, followed by 3 units/hr for 5 hr. Controls received plasma cryoprecipitate selectively depleted of fibronectin by affinity chromatography. Bacterial challenge rapidly resulted in severe systemic hypotension. Ringer's lactate was infused intravenously into both groups at a rate sufficient to maintain a systemic arterial pressure of approximately 50 mm Hg with a maximum pulmonary artery wedge pressure of 15-18 mm Hg. Its rate of infusion was periodically adjusted to maintain this hemodynamic status. Comparison was made of the volume of Ringer's lactate required to maintain an arterial pressure of 50 mm Hg in both groups. Net fluid requirement was significantly (p less than 0.05) less in postoperative septic sheep (47.4 +/- 6.2 mg/kg/hr) treated with fibronectin-rich cryoprecipitate compared to the fluid requirement (71.7 +/- 4.7 mg/kg/hr) for postoperative septic sheep receiving fibronectin-deficient cryoprecipitate. Thus elevation of plasma fibronectin concentration lowers the fluid requirements needed for hemodynamic support in postoperative Gram-negative sepsis.     

Cerebrovascular carbon dioxide reactivity during general anesthesia: a comparison between sevoflurane and isoflurane

We compared cerebrovascular carbon dioxide reactivity during the administration of sevoflurane and isoflurane anesthesia by measuring cerebral blood flow velocity (CBFV) as an indirect measurement of cerebral blood flow. Thirty patients, 20-70 yr old, undergoing lower abdominal surgery and without known cerebral or cardiovascular system disease, were randomly assigned to either sevoflurane or isoflurane treatment groups. Anesthesia was induced with thiopental 5 mg/kg IV and maintained with either sevoflurane or isoflurane in 67% nitrous oxide and oxygen. The CBFV and pulsatility index (PI) of the left middle cerebral artery were monitored with transcranial Doppler. The P(ETCO)2 was increased stepwise from 20 to 50 mm Hg by changing the respiratory rate with a constant tidal volume. At every 5-mm Hg stepwise change in P(ETCO)2, CBFV and PI were recorded. CBFV increased with increasing P(ETCO)2. CBFV was significantly smaller in the isoflurane group at P(ETCO)2 = 20-40 mm Hg than in the sevoflurane group. The rate of change of CBFV with changes in CO2 was larger in the isoflurane group than in the sevoflurane group. PI was constant over time and was not different between groups. In conclusion, hypocapnia-induced reduction of intracranial pressure might be more effective during the administration of isoflurane than sevoflurane. IMPLICATIONS: Changes in cerebral blood flow caused by the changes of carbon dioxide tension are greater during the administration of isoflurane anesthesia compared with sevoflurane anesthesia. Attempts to decrease intracranial pressure by decreasing carbon dioxide tension may be more successful during isoflurane than sevoflurane anesthesia administration.     

Angiotensin II receptor blockade prevents acute renal sodium retention induced by low levels of orthostatic stress

BACKGROUND: Depending on its magnitude, lower body negative pressure (LBNP) has been shown to induce a progressive activation of neurohormonal, renal tubular, and renal hemodynamic responses, thereby mimicking the renal responses observed in clinical conditions characterized by a low effective arterial volume such as congestive heart failure. Our objective was to evaluate the impact of angiotensin II receptor blockade with candesartan on the renal hemodynamic and urinary excretory responses to a progressive orthostatic stress in normal subjects. METHODS: Twenty healthy men were submitted to three levels of LBNP (0, -10, and -20 mbar or 0, -7.5, and -15 mm Hg) for 1 hour according to a crossover design with a minimum of 2 days between each level of LBNP. Ten subjects were randomly allocated to receive a placebo and ten others were treated with candesartan 16 mg orally for 10 days before and during the three levels of LBNP. Systemic and renal hemodynamics, renal sodium excretions, and the hormonal response were measured hourly before, during, and for 2 hours after LBNP. RESULTS: During placebo, LBNP induced no change in systemic and renal hemodynamics, but sodium excretion decreased dose dependently with higher levels of LBNP. At -20 mbar, cumulative 3-hour sodium balance was negative at -2.3 +/- 2.3 mmol (mean +/- SEM). With candesartan, mean blood pressure decreased (76 +/- 1 mm Hg vs. 83 +/- 3 mm Hg, candesartan vs. placebo, P < 0.05) and renal plasma flow increased (858 +/- 52 mL/min vs. 639 +/- 36 mL/min, candesartan vs. placebo, P < 0.05). Glomerular filtration rate (GFR) was not significantly higher with candesartan (127 +/- 7 mL/min in placebo vs. 144 +/- 12 mL/min in candesartan). No significant decrease in sodium and water excretion was found during LBNP in candesartan-treated subjects. At -20 mbar, the 3-hour cumulative sodium excretion was + 4.6 +/- 1.4 mmol in the candesartan group (P= 0.02 vs. placebo). CONCLUSION: Selective blockade of angiotensin II type 1 (AT1) receptors with candesartan increases renal blood flow and prevents the antinatriuresis during sustained lower body negative pressure despite a modest decrease in blood pressure. These results thus provide interesting insights into potential benefits of AT1 receptor blockade in sodium-retaining states such as congestive heart failure.     

Hypertonic saline as a resuscitation solution in hemorrhagic shock: effects on extravascular lung water and cardiopulmonary function

To determine the effect of resuscitation with hypertonic saline on extravascular lung water, seven adult sheep were endotracheally intubated; mean arterial pressure (MAP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) were monitored. A 5-French, thermistor-tipped catheter was used to measure extravascular lung water (EVLW). Colloid oncotic pressure (COP), serum electrolytes and osmolality, and arterial and mixed venous blood gas tensions were measured. The COP-PCWP gradient and the shunt fraction (Qsp/Qt) were calculated. After baseline measurements, the animals were bled to an MAP of 50 mm Hg (blood volume removed, 16.2 +/- 3.6 ml/kg), which was maintained for 30 min, measurements then being repeated. Three percent sodium chloride solution was infused at 500 ml/15 min until two of three parameters--cardiac output (CO), PCWP, or MAP--were restored to baseline values. Data were recorded again and then 60 min later. No shed blood was reinfused. The total volume of hypertonic saline infused was 39 +/- 19 ml/kg. Pulmonary artery pressure did not vary throughout the study. PCWP, MAP, and CO were significantly lower than baseline (P less than 0.05) 30 min after bleeding but all except MAP returned to baseline with resuscitation. Throughout the study, EVLW did not vary despite a COP-PCWP gradient less than 4 mm Hg. Serum sodium levels and serum osmolality were significantly above baseline values after resuscitation. In this animal model of hemorrhagic shock, infusion of hypertonic saline effected resuscitation without compromising cardiopulmonary function or increasing EVLW.     

Is atrial function affected by conventional cardioplegic arrest?

Conventional cardioplegic arrest results in persistent atrial electrical and mechanical activity. This activity has been postulated to result in atrial ischemia which can induce postoperative arrhythmias and impair the transport function of the atrium. In this study, the effects of simple cardiopulmonary bypass (CPB) (seven pigs) and conventional cardioplegic arrest (CCA) (seven pigs) on right atrial function were evaluated. Function was assessed in an isolated right atrial preparation with a compliant balloon inserted via the superior vena cava. CCA for 1 hr produced significant deterioration in right atrial function (developed pressure 14.1 +/- 0.7 vs 18.9 +/- 0.8 mm Hg, P less than 0.05, diastolic pressure 10.0 +/- 1 vs 4.5 +/- 1.4 mm Hg, P less than 0.05, dP/dt 134 +/- 25 vs 187 +/- 19 mm Hg/sec, P less than 0.05 at a balloon volume of 20 ml after 1 hr of reperfusion). CPB alone caused no alteration in pressures in the right atrium but was associated with a late decrease in dP/dt (developed pressure 19.3 +/- 1.8 vs 18.9 +/- 0.8 mm Hg, diastolic pressure 4.0 +/- 1.2 vs 4.5 +/- 1.4 mm Hg, dP/dt 148 +/- 18 vs 187 +/- 19, P less than 0.05 at a balloon volume of 20 ml at a time corresponding to 1 hr of reperfusion in the CCA group). These results are consistent with the postulate that conventional techniques of cardioplegic arrest are associated with ischemic dysfunction of the right atrium.     

Nonuniform blood flow in the canine left ventricle

In order to investigate the relationship between coronary perfusion pressure and blood flow distribution in the left ventricle (LV), we measured myocardial blood flow in small regions using radioactive microspheres in six anesthetized, open-chest dogs. Mean coronary perfusion pressure (CPP) was controlled with a femoral artery to left main coronary artery shunt which included a pressurized, servo-controlled blood reservoir. In each dog, we measured flow in 192 regions of the LV free wall (mean weight per region = 206 +/- 38 mg) at different perfusion pressures. At CPP = 80 mm Hg, blood flow to individual regions varied fourfold (0.30 to 1.18 ml/min/g; relative dispersion (RD) = 21.8 +/- 2.3%). At CPP = 50 mm Hg, flow varied over sevenfold (0.08 to 0.60 ml/min/g; RD = 42.8 +/- 10%; P less than 0.01 vs 80 mm Hg). This relationship between flow variability and CPP was present within individual LV layers as well between layers and is much higher than the error associated with the microsphere technique. We conclude that blood flow to small regions of the LV is markedly nonuniform. This heterogeneity becomes more profound at lower CPP. These findings suggest that (1) global measurements of coronary flow must be interpreted with caution, and (2) even in hearts with normal coronary arteries some regions of the LV are more susceptible to ischemia than others. In addition, these findings may help explain the patchy nature of myocardial damage that occurs following periods of low coronary pressure or inadequate myocardial protection during cardiopulmonary bypass.     

Cardiovascular effects of positive end-expiratory pressure (PEEP) after pneumonectomy in dogs

Little is known regarding the hemodynamic effect of positive end-expiratory pressure (PEEP) following pneumonectomy. To investigate this, 9 mongrel dogs underwent PEEP before and after lung resection. With the chest closed, the dog anesthetized, and partial pressure of carbon dioxide constant, PEEP was added in increments of 2 mm Hg until the animal's condition became hemodynamically unstable. At each level of PEEP, aortic, pulmonary, left atrial, and central venous pressures were monitored while aortic flow (cardiac output) was determined with an electromagnetic probe and airway pressure was measured with a Millar catheter in the respiratory tubing. Pneumonectomy was then performed, PEEP was again sequentially added, and the same measurements were recorded. Both before and after pneumonectomy, a strong positive linear correlation exists between the level of PEEP and pulmonary vascular resistance (PVR) (r greater than 0.74; p less than 0.05). Also, there is a high negative linear correlation between the level of PEEP and cardiac output (r greater than -0.76; p less than 0.05). At 0 mm Hg of PEEP, the PVR is higher after pneumonectomy than before (p less than 0.02). The incremental elevation in PVR persists after pneumonectomy at each level of PEEP, and in 5 of the 9 dogs the slope of the linear regression line relating PVR to PEEP was steeper following resection (p less than 0.05), thereby demonstrating an exaggerated effect of PEEP on PVR. In addition, all animals had a lower cardiac output at each comparable level of PEEP following pneumonectomy (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

125I-hippuran absorption from the human renal pelvis

The absorption of 125I-hippuran from human renal pelvis was studied peroperatively in 18 patients with obstruction at the pelviureteric junction. Three types of experiment were included: absorption during induced diuresis, absorption at a constant intrapelvic pressure of 30 cm. H2O, and excretion of the indicator by the contralateral kidney. Total and separate glomerular filtration rate were measured using 51Cr-EDTA clearance technique and isotope renography. Distal tubular function was evaluated as maximum concentration ability. During induced diuresis the intrapelvic pressure increased to an average maximum value of 31.6 cm. H2O. The excretion of isotope from the contralateral kidney varied from one to 44% of the given dose. A significant correlation (r = 0.87) between the maximum intrapelvic pressure obtained and the amount of isotope excreted from the contralateral kidney was demonstrated. At a constant intrapelvic pressure of 30 cm. H2O the excretion of isotope from the contralateral kidney varied from two to 26% of the dosage given. The low value probably depended on the impaired function of the obstructed kidney. Our results show the existence of a significant reflux from the renal pelvis of small molecules, which was affected by renal function, intrapelvic pressure and volume.