Low-pressure laparoscopy may ameliorate intracranial hypertension and renal hypoperfusion

BACKGROUND: Increased abdominal pressure is associated with elevations in the intracranial pressure (ICP) and impaired renal function. These adverse effects are potentially important in clinical situations such as severe abdominal trauma and laparoscopic donor nephrectomy. It was hypothesized that the secondary elevation of ICP leads to release of vasoconstrictors, which may affect renal function by decreasing the renal blood flow (RBF). We investigated the effect of laparoscopy on ICP and renal blood flow in a porcine model. MATERIALS AND METHODS: The abdominal pressure of swine (N = 5; 20-25 kg) was gradually increased from baseline to 5, 15, and 25 mm Hg by insufflation of nitrogen into the abdominal cavity. The ICP was measured using a Camino monitor, and RBF was simultaneously measured using a Transonic Doppler probe placed on the renal artery. Results were analyzed using repeated measures ANOVA and the paired t-test. RESULTS: No significant change from baseline was observed in ICP and RBF when the abdominal pressure was 5 mm Hg. However, both ICP and RBF were affected by increasing the abdominal pressure to 15 and 25 mm Hg (P = 0.035 and 0.04 for ICP and P = 0.074 and 0.034 for RBF, respectively). CONCLUSIONS: Low-pressure laparoscopy may reduce the adverse effects of pneumoperitoneum on ICP and RBF. It may be advisable to use low pressures in laparoscopic surgery, especially when changes in ICP or renal perfusion may have significant clinical implications.     

Effects of chronic cyclosporine administration on renal blood flow and intrarenal blood flow distribution

Cyclosporine-induced decreases in renal blood flow (RBF) and glomerular function are well documented. Glomerular filtration and tubular function may be affected by changes in both total renal blood flow and cortical blood flow distribution (CBFD). The effect of CsA on RBF, CBFD, glomerular filtration rate, and tubular function was studied in conscious ewes receiving a mean CsA dose of 30 mg/kg/day for 28 days with mean CsA trough levels of 344 +/- 45 ng/ml. RBF and CBFD were determined by the injection of 15 microns radioactive microspheres before and after one month of treatment with CsA or its vehicle, olive oil. RBF decreased by 24% from 7.65 +/- 0.87 to 5.79 +/- 0.42 ml/min/g of kidney in CsA-treated ewes (P = 0.014), while no decrease was noted in the control group (7.92 +/- 1.10 vs. 7.62 +/- 0.71). Intracortical blood flow decreased in proportion to the fall in total renal blood flow--thus CsA treatment did not change the cortical distribution of flow. There was a 25% decrease in GFR, as determined by inulin clearance, in the CsA-treated group (80 +/- 6 vs. 62 +/- 3 ml/min; P = 0.027) while there was a nonsignificant increase in control animals (62 +/- 11 vs. 92 +/- 7 ml/min). There was no evidence of tubular dysfunction in either group. There were also no changes in urinary excretion rates of prostaglandins PGE2, 6-keto-PGF1 alpha or thromboxane B2, nor were there changes in plasma renin activity. CsA induced decreases in RBF occur red without redistribution of cortical blood flow, indicating that altered cortical distribution of blood flow is not responsible for the changes in GFR or tubular function that have been reported. The changes in renal blood flow and glomerular filtration rate are independent of changes in renal prostaglandin production, and are likely not associated with altered plasma renin activity.     

腹腔镜胆囊切除术中患者肾血流量的变化

目的 探讨腹腔镜胆囊切除术中患者肾血流量的变化.方法 择期行腹腔镜胆囊切除术患者32例,年龄18～64岁.气管插管后经口置入食管超声探头,采用经食管超声心动图分别于气腹前(基础状态)、气腹1、5、10、15、20、30 min、气腹停止后1、5 min时测量左肾动脉主干内径、主动脉内径、左肾动脉主干血流速度时间积分和降主动脉血流速度时间积分,计算左肾血流量(LRAF)、降主动脉血流量(DAF)和LRAF与DAF的比值(LRAF/DAF).分析LRAF和DAF的最大下降时点、最大下降量和最大下降百分比.结果 与基础值比较,气腹中各时点LRAF和DAF下降(P＜0.05),气腹停止后差异无统计学意义(P＞0.05);气腹中和气腹停止后各时点LRAF/DAF差异无统计学意义(P＞0.05).气腹中LRAF和DAF最大下降时间点分别为8.9 min[95%可信区间(95%CI)5.5～12.4 min]和6.7 min(95%CI4.0～9.5 min),最大下降量分别为130 ml/min(95%CI 96～163 ml/min)和1.57 L/min(95%CI1.20～1.95 L/min),最大下降百分比分别为40%(95%CI 31%～49%)和38%(95%CI 31%～44%).结论 腹腔镜胆囊切除术中气腹1～30 min时肾血流量下降,下降的最大程度约40%,时间在气腹9 min左右,其下降的原因与心输出量下降有关.     

Effects of renal nerves on renal hemodynamics. I. Direct stimulation and carotid occlusion.

Renal nerves were stimulated either directly (loop electrodes) or indirectly (bilateral carotid occlusion with maintenance of control blood pressure) in anesthetized dogs to determine the effects on renal blood flow (RBF), glomerular filtration rate (GFR), sodium excretion (UNaV), and intrarenal distribution of blood flow (microsphere method). Direct nerve stimulation decreased RBF 20% in 9 of 10 dogs; but GFR, UNaV, and intrarenal distribution of blood flow did not change significantly. Carotid occlusion decreased RBF in 9 of 10 dogs. There was a 22% fall in RBF for the whole group, GFR decreased 33%, and UNaV decreased from 0.39 to 0.17 muEq/min/g (p smaller than 0.05). A small (8%) decrease in midcortical fractional flow (p smaller than 0.05 after carotid occlusion was the only distributional flow change observed. The results disclosed no relationship between changes in sodium excretion and changes in total RBF, GFR, or intrarenal distribution of blood flow following nerve stimulation. These studies also indicate that the renal effects of carotid occlusion are probably not mediated by renal nerve stimulation alone.     

Changes in renal function induced by anesthesia

The rate of urine formation and its composition are influenced by the different drugs used during surgery. Anaesthetics act on renal function, not only directly, but also by producing changes in cardiovascular function and in neuroendocrine activity. Many factors may be incriminated: lowered blood pressure and cardiac output, increased sympathetic outflow (renal nerve stimulation and increased plasma catecholamines), increased release of renin, angiotensin and vasopressin. The effects of anaesthetics on the kidney go beyond a simple change in basal haemodynamics and include, for some drugs, an alteration in the ability for the kidney to autoregulate its blood flow and glomerular filtration rate. Studies on toad bladders showed a decrease in transport of water, sodium and organic anions. But, in fact, renal effects of anaesthetics in man and animals depend on the species, the anaesthetic and the method used to study the effect. Most barbiturates and inhalational anaesthetics tend to decrease renal blood flow (RBF) and glomerular filtration rate (GFR). These trends are gradually reversed during recovery. The effects of ketamine and diazepam are not clearly defined. Morphine and fentanyl decrease urine flow and GFR, whilst RBF increases or decreases, depending on whether a direct or indirect measurement technique was used. Muscle relaxants have little effect on renal function. Spinal and epidural anaesthesia only slightly decrease GFR and RBF in proportion to the decrease in mean arterial pressure. Obviously, the preexisting intravascular volume and the quantity of intravenous fluids given strongly influence the renal response to spinal and epidural anaesthesia. Some studies have shown that urine flow rate, creatinine clearance, urinary sodium excretion and RBF are reduced during mechanical ventilation with positive end-expiratory pressure. Surgery itself influences renal function by inducing alterations in prerenal haemodynamics. Operative stress leads to an increase in circulating catecholamines and angiotensin. Significant fluid shifts, excessive blood loss and redistribution of a third space may lead to a prerenal oliguric state, increasing secretion of vasopressin. Acute renal failure (ARF) is a frequently lethal complication of critical surgical illness, due to a variety of factors which interfere with glomerular filtration and tubular reabsorption, such as renal hypoperfusion or nephrotoxic insults. In fact, the initiating aggression ultimately culminates in the development of one or more of the maintenance factors (decreased tubular function, tubular obstruction, decreased GFR and RBF) that reduce urine flow and osmolar excretion. Good management during the perioperative period tends to minimize the risk of developing ARF.     

Changing renal blood flow following sodium nitroprusside in patients undergoing nephrolithotomy

During nephrolithotomy in 23 adult patients under sodium thiopental-N2O-O2-fentanyl anesthesia, renal blood flow to one kidney was studied. Muscle relaxation was obtained with pancuronium, and renal blood flow (RBF) was measured with an electromagnetic flow probe. Percutaneous arterial pressures were also recorded. Administration of sodium nitroprusside caused a decrease in RBF in all patients when mean arterial pressure (MAP) was reduced approximately 44 percent below baseline. Patients whose initial RBF was below 300 ml/min showed greater falls in RBF with hypotension. Changes in renal vascular resistance (MAP/RBF) was found to be markedly higher in the "low-flow" group. As expected, the low-flow group started with a higher renal vascular resistance. From these observations, it is felt that more concern should be exercised when planning deliberate hypotension with nitroprusside, especially in patients with decreased renal function.     

Beneficial effect of insulin-like growth factor-1 on hypoxemic renal dysfunction in the newborn rabbit

Acute normocapnic hypoxemia can cause functional renal insufficiency by increasing renal vascular resistance (RVR), leading to renal hypoperfusion and decreased glomerular filtration rate (GFR). Insulin-like growth factor 1 (IGF-1) activity is low in fetuses and newborns and further decreases during hypoxia. IGF-1 administration to humans and adult animals induces pre- and postglomerular vasodilation, thereby increasing GFR and renal blood flow (RBF). A potential protective effect of IGF-1 on renal function was evaluated in newborn rabbits with hypoxemia-induced renal insufficiency. Renal function and hemodynamic parameters were assessed in 17 anesthetized and mechanically ventilated newborn rabbits. After hypoxemia stabilization, saline solution (time control) or IGF-1 (1 mg/kg) was given as an intravenous (i.v.) bolus, and renal function was determined for six 30-min periods. Normocapnic hypoxemia significantly increased RVR (+16%), leading to decreased GFR (−14%), RBF (−19%) and diuresis (−12%), with an increased filtration fraction (FF). Saline solution resulted in a worsening of parameters affected by hypoxemia. Contrarily, although mean blood pressure decreased slightly but significantly, IGF-1 prevented a further increase in RVR, with subsequent improvement of GFR, RBF and diuresis. FF indicated relative postglomerular vasodilation. Although hypoxemia-induced acute renal failure was not completely prevented, IGF-1 elicited efferent vasodilation, thereby precluding a further decline in renal function. Presented orally at the yearly meeting of the French Society of Pediatric Nephrology (SNP), Amsterdam, The Netherlands, 17–19 November 2005. Presented as an oral/poster at the 40th Annual Meeting of the European Society for Pediatric Nephrology (ESPN), Palermo, Italy, 7–10 October 2006.     

Effect of intravascular volume expansion on renal function during prolonged CO2 pneumoperitoneum

OBJECTIVE: To evaluate whether intravascular volume expansion would improve renal blood flow and function during prolonged CO2 pneumoperitoneum. SUMMARY BACKGROUND DATA: Although laparoscopic living donor nephrectomies have a considerably reduced risk of complications for the donors, significant concerns exist regarding procurement of a kidney in the altered physiologic environment of CO2 pneumoperitoneum. Recent studies have documented adverse effects of CO2 pneumoperitoneum on renal hemodynamics. METHODS: Renal and systemic hemodynamics and renal histology were studied in a porcine CO2 pneumoperitoneum model. After placement of a pulmonary artery catheter, carotid arterial line, Foley catheter, and renal artery ultrasonic flow probe, CO2 pneumoperitoneum (15 mmHg) was maintained for 4 hours. Pigs were randomized into three intravascular fluid protocol groups: euvolemic (3 mLkg/hour isotonic crystalloid), hypervolemic (15 mL/kg/hour isotonic crystalloid), or hypertonic (3 mL/kg/hour isotonic crystalloid plus 1.2 mL/kg/hour 7.5% NaCl). RESULTS: In the euvolemic group, prolonged CO2 pneumoperitoneum caused decreased renal blood flow, oliguria, and impaired creatinine clearance. Both isotonic and hypertonic volume expansions reversed the changes in renal blood flow and urine output, but impaired creatinine clearance persisted. CONCLUSIONS: Intravascular volume expansion alleviates the effects of CO2 pneumoperitoneum on renal hemodynamics in a porcine model. Hypertonic saline (7.5% NaCl) solution may maximize renal blood flow in prolonged pneumoperitoneum, but it does not completely prevent renal dysfunction in this setting. This study suggests that routine intraoperative volume expansion is important during laparoscopic live donor nephrectomy.     

Functional MR Imaging of the Porcine Kidney: Physiologic Changes of Prolonged Pneumoperitoneum

Background:

Increased intraabdominal pressure (IPA) during laparoscopy has been associated with decreased urine output. The purpose of this study was to use a noninvasive MRI technique to measure renal vessel flow velocity and change in differential renal medulla and cortex perfusion during pneumoperitoneum.

Study Design:

Six female farm pigs underwent general endotracheal anesthesia and dynamic imaging following left ventricular (LV) injection of Gd-DTPA, utilizing a dual echo gradient echo sequence. MRI was repeated after three hours of continuous 15 mm Hg pneumoperitoneum in three study pigs and after three hours of monitored general anesthesia without pneumoperitoneum in three control pigs. Renal artery and renal vein flow velocities were calculated using cine phase-contrast technique. Renal perfusion was independently measured by LV injection of radiolabelled microspheres.

Results:

There was a decrease in mean renal vein flow velocity in the pneumoperitoneum group as compared to the control group. During pneumoperitoneum there was a similar percentage reduction in the perfusion of the cortex (-28% ) and medulla (-31% ); this corresponded with a decreased urine output. In addition, radiolabelled microspheres corroborated the similar decrease in both cortical and medullary perfusion rates during pneumoperitoneum.

Conclusions:

Prolonged IAP is associated with a decrease in renal vein flow velocity and urine output. There is a similar decrease in the renal medulla and cortex perfusion rates during pneumoperitoneum of 15 mm Hg.     

Effects of carbon dioxide pneumoperitoneum on hemodynamics in cirrhotic rats

Background: The aim of our study was to investigate the effect of carbon dioxide pneumoperitoneum on systemic and splanchnic hemodynamics in cirrhotic rats. Methods: Sprague–Dawley rats (n = 80) were used in this study. Liver cirrhosis was induced by thioacetamide administration intraperitoneally (200 mg/kg body weight, twice a week for 16 weeks). The radioactive microsphere method was used to measure systemic and regional hemodynamic parameters before, 1 h after the start, and 1 h after the release of pneumoperitoneum. Results: Splanchnic blood flow and cardiac index were significantly depressed during pneumoperitoneum in liver cirrhosis and control groups, but no significant differences were seen between the two groups. In both groups, portal venous inflow decreased and hepatic arterial blood flow increased significantly during pneumoperitoneum. However, during pneumoperitoneum, total hepatic blood flow as a percentage of its value before pneumoperitoneum was lower in cirrhotic rats (71.0%) than in control rats (91.9%) (p <0.05, Mann–Whitney U-test). Conclusions: Carbon dioxide pneumoperitoneum markedly decreases total hepatic blood flow in cirrhotic rats due to the impaired hepatic arterial buffer response. Liver function should be carefully controlled in cirrhotic patients after laparoscopic surgery with pneumoperitoneum.     

Laparoscopic surgery: Pitfalls due to anesthesia, positioning, and pneumoperitoneum

Background Laparoscopic procedures are increasing in number and extensiveness. Many patients undergoing laparoscopic surgery have coexisting disease. Especially in patients with cardiopulmonary comorbidity, pneumoperitoneum and positioning can be deleterious. This article reviews possible pitfalls related to the combination of anesthesia, positioning of the patient, and the influence of pneumoperitoneum in the course of laparoscopic interventions. Methods A literature search using Medline’s MESH terms was used to identify recent key articles. Cross-references from these articles were used as well. Results Patient positioning and pneumoperitoneum can induce hemodynamic, pulmonary, renal, splanchnic, and endocrine pathophysiological changes, which will affect the entire perioperative period of patients undergoing laparoscopic procedures. Conclusion Perioperative management for the estimation and reduction of risk of morbidity and mortality due to surgery and anesthesia in laparoscopic procedures must be based on knowledge of the pathophysiological disturbances induced by the combination of general anesthesia, pneumoperitoneum, and positioning of the patient.     

Renal bloodflow and function in the rabbit after surgical trauma. I. An experimental study.

The aim of the present study was to examine the influence of surgical trauma on renal blood flow (RBF) and renal funciotn. The renal vessels were catheterized in lightly anaesthetized rabbits and the dye-dilution technique was used to measure renal blood flow and cardiac output. The renal fraction of the cardiac output (RBF % CO), the total peripherauation of the glomerular and tubular function was made by measuring the extraction of EDTA and of Hippuran. A decrease in the cardiac output was accompanied by a diminution of renal blood flow. Renal blood flow was reduced, regardless of whether surgery or puncture of the kidney was performed, probably due to vasoconstriction in the kidney caused by an increase in sympathetic tonus or in the concentration of plasma catecholamines. Manipulation of the renal artery seemed to stimulate further vasoconstriction in the ipsilateral kidney by a direct effect. The glomerular and tubular function decreased initially, independently of surgical trauma, and it is therefore assumed that the initial renal vasoconstriction includes the afferent arterioles. Renal function was not greatly influenced by handling of the renal artery.     

Elucidating the relationship between cardiac preload and renal perfusion under pneumoperitoneum

Introduction Pneumoperitoneum is associated with a well-described decrease in renal blood flow, but it remains unclear whether a decrease in cardiac preload is responsible. Our aim was to characterize the relationship between cardiac preload and renal perfusion during pneumoperitoneum. Methods Eleven pigs were submitted to three 30 minute study periods: 1) Baseline (n=11): no interventions, 2) Pneumoperitoneum (n=11): 12 mmHg CO2 pneumoperitoneum, 3) Preload Reduction: pneumoperitoneum and nitroglycerin infusion (n=8); or pneumoperitoneum and hemorrhage to a mean arterial pressure (MAP) of 40 mmHg (n=3). Echocardiographic measurements of left ventricular end-diastolic diameter (LVEDD) were used as an index of preload. Renal cortical perfusion (RCP) was measured using laser doppler flowmetry. Results LVEDD decreased from 4.2 ± 0.5 to 4.1 ± 0.6 cm (p=0.02) with pneumoperitoneum and then to 4.0 ± 0.5 cm (p=0.03) with the addition of nitroglycerin. There was no statistically significant change in RCP with pneumoperitoneum (33.5 ± 8.4 to 28.5 ± 8.4 ml/min/100g tissue, p=0.2), but it decreased to 18.5 ± 11.3 ml/min/100g tissue (p=0.001) with the addition of nitroglycerin. The correlation between RCP and LVEDD was weak (0.35, p=0.003), whereas correlation between RCP and MAP was superior (R=0.59, p<0.0001). Conclusions While decreasing preload under extreme lab conditions also decreases RCP, simply creating a pneumoperitoneum of 12 mmHg does not. The decrease in renal blood flow associated with pneumoperitoneum is likely not solely a function of preload.     

Acute cyclosporine A-induced nephrotoxicity: a rabbit model

Chronic cyclosporine A (CsA) nephrotoxicity has been widely assessed but only few studies have described acute nephrotoxicity. As CsA is now used for short periods, we developed an experimental model of acute CsA-induced nephrotoxicity. Renal clearances of inulin and para-aminohippurate were assessed in 35 New Zealand rabbits. Group 1: control, no treatment; group 2: CsA 25 mg/kg per day in 0.5 ml/kg per day for 5 days; group 3: vehicle Cremophor-EL, 0.5 ml/kg per day for 5 days; group 4: follow-up, the same as group 2, then CsA discontinuation for 31 days. Compared with group 1, CsA significantly decreased glomerular filtration rate (GFR), renal blood flow (RBF), and diuresis, with a significant increase in renal vascular resistance (RVR). The proportional fall in GFR (–32.3%) and RBF (–33.1%) suggests both pre- and postglomerular vasoconstriction.Discontinuation of CsA in group 4 led to normalization of RVR with improvement of other renal function parameters. Compared with group 1, Cremophor-EL induced no significant changes but an increased RBF. Microvacuolization of proximal tubule epithelial cells was the sole histological abnormality observed only in group 2. The overall results suggest that CsA induced a vasomotor acute renal failure which was not due to Cremophor-EL. This effect was partly reversible after discontinuation of treatment. Received: 20 January 1999 / Revised: 24 June 1999 / Accepted: 13 August 1999     

Renal vasoconstriction after low and high osmolar contrast agents in ischemic and non ischemic canine kidney

We have assessed the effect of contrast media on renal blood flow before and after inducing renal ischemia. Diatrizoate, iopamidol and ioxaglate were injected within 15 seconds at 20 min intervals, at the dose of 1 ml/kg during a control period and 15 min after applying an aortic clamp to reduce the renal perfusion pressure to 70 mmHg. During the control period iopamidol, ioxaglate (17 +/- 13%) and diatrizoate (16 +/- 2%) induced a comparable decrease in renal blood flow (RBF). During the ischemic period the effects of diatrizoate on renal hemodynamic were dramatically enhanced. Ioxaglate andiopamidol induced a 20 +/- 12 and a 32 +/- 9% decrease in RBF at 1 minute, respectively. Iopamidol induced an increase in renal vascular resistance (RVR) from 0.8 +/- 0.08 to 1.46 +/- 0.26 mmHg min/ml (p less than 0.05). Ioxaglate induced an increase in RVR from 0.8 +/- 0.09 to 1.36 +/- 0.38 (p less than 0.05). Diatrizoate induced a 77 +/- 10% decrease in RBF and a maximum increase in RVR at 1 minute from 0.9 +/- 0.09 to 26 +/- 12 mmHg min/ml. There was still a 36 +/- 14% and a 23 +/- 13% decrease in RBF 10 and 20 min after diatrizoate administration. These changes were significantly higher than those observed with all contrast media during the control period and low osmolar contrast media during the ischemic period. We have thus shown that ischemia potentiates the renal vascular effect of contrast media.(ABSTRACT TRUNCATED AT 250 WORDS)     

Renal effects of mannitol in the early stage of glycerol-induced acute renal failure in the rat.

The effects of mannitol on the hemodynamics and excretory function of the kidney in control rats and in rats with acute renal failure (ARF), induced by glycerol, were studied using clearance, micropuncture and flowmeter techniques. In control animals, 20% mannitol significantly increased renal blood flow (RBF), urinary volume and sodium excretion and decreased urinary sodium concentration and fractional tubular sodium reabsorption. Glomerular filtration rate (GFR) and effective filtration pressure remained unchanged. 50% glycerol (10 ml/kg bw) was injected intramuscularly in other groups of rats to induce ARF. Functional impairment of the glycerol-treated animals consisted in a significant decrease in urinary sodium concentration, RBF, GFR and effective filtration pressure of superficial nephrons. Urea concentration in arterial plasma and urine volume increased significantly. Infusion of 20% mannitol into these animals led to a significant further decrease in GFR and net filtration pressure, but not in RBF. Urine volume increased to the same degree as in controls.     

Tramadol has no effect on cortical renal blood flow--despite increased serum catecholamine levels--in anesthetized rats: implications for analgesia in renal insufficiency

Tramadol is an analgesic that inhibits norepinephrine (NE) reuptake. Although NE released from renal sympathetic nerves causes renal hypoperfusion, the effects of tramadol on renal hemodynamics have not been well characterized. We investigated the effects of tramadol on renal blood flow (RBF), mean arterial blood pressure (MAP), and heart rate (HR) by using a laser Doppler flowmeter, both in normal anesthetized rats and in rats with experimentally-induced nephritis secondary to anti-Thy 1.1 antibody administration. We also studied the effects of tramadol on serum NE levels. Tramadol increased MAP and decreased HR without changing RBF in normal rats at clinical doses. Serum NE levels increased up to 176% of control after a 2 mg/kg bolus injection of tramadol. Continuously infused, increasing doses of tramadol (0.5-4 mg.kg(-1).h(-1)) did not affect MAP, HR, or RBF. Tramadol also increased MAP and decreased HR without changing RBF in rats with experimentally induced renal insufficiency. These findings suggest that a bolus injection of tramadol does not alter RBF, although it causes a decrease in HR and an increase in MAP and serum NE in both normal rats and in rats with renal insufficiency. These results suggest that tramadol may have little effect on RBF during the postoperative period. IMPLICATIONS: A bolus and continuous injection of tramadol does not alter renal blood flow (RBF) in normal rats. A bolus injection of tramadol has little effect on RBF in rats with experimentally induced renal insufficiency. These results suggest that tramadol would be a safe analgesic for maintaining RBF during the postoperative period.     

Impaired renal blood flow autoregulation in two-kidney, one-clip hypertensive rats is caused by enhanced activity of nitric oxide

Increases in renal perfusion pressure will induce shear stress-mediated nitric oxide (NO) release, which could oppose autoregulation of renal blood flow (RBF). Although cardiac, cerebral, and mesenteric autoregulation is enhanced during nitric oxide (NO) synthesis inhibition, this has not been reported for renal autoregulation of blood flow. In the present study, the lower limit and efficiency of RBF autoregulation (as assessed by the degree of compensation) were studied before and during NO inhibition in normotensive Sprague Dawley rats (control; n = 9) and in the non-clipped kidney of two-kidney, one-clip Goldblatt hypertensive animals (2K1C; n = 9; 3 wk; 0.25-mm silver clip). In both groups, renal autoregulation curves were obtained before and during infusion of N(G) -nitro-L-arginine (L-NNA) (bolus 1.5 mg/kg intravenously, infusion 10 microg/kg per min intravenously), using a transit-time flow probe around the left renal artery. In control rats, mean arterial pressure (MAP) increased, RBF decreased, and renal vascular resistance (RVR) increased in response to L-NNA infusion. The lower limit of autoregulation in control animals did not significantly change during L-NNA infusion (78 +/- 3 to 70 +/- 2 mmHg). The degree of compensation in these rats slightly increased during L-NNA infusion, however, this was only significant below 90 mmHg. The 2K1C rats had elevated MAP under baseline conditions. L-NNA infusion resulted in a decrease in RBF and an increase in MAP and RVR. During L-NNA infusion, RVR in 2K1C rats greatly exceeded RVR in control rats. A significant decrease was observed in the lower limit of autoregulation from 85 +/- 3 to 72 +/- 5 mmHg (P < 0.05). In the contralateral kidney of 2K1C rats, the degree of compensation was lower than in control rats under baseline conditions. L-NNA infusion resulted in significantly higher degrees of compensation compared to baseline. In conclusion, the contralateral kidney displayed a high NO dependency, as RBF greatly decreased and RVR dramatically increased in response to L-NNA infusion. The contralateral kidney of 2K1C rats exhibited impaired RBF autoregulation, which was improved by NO inhibition, as judged from a decrease in the lower limit of autoregulation and an increase in the degree of compensation. This study indicates that perfusion pressure-dependent NO release can oppose autoregulation in the kidney. However, the enhanced influence of NO on pressure-dependent RBF may facilitate the preservation of renal function in the nonclipped kidney of 2K1C rats.     

Renal hemodynamics during carbon dioxide pneumoperitoneum

Background: Laparoscopic living donor nephrectomy is increasingly being performed, although the effects of carbon dioxide pneumoperitoneum (CO2 PP) on renal function and hemodynamics and the levels of vasopressin are not well studied. Methods: Renal blood flow, renal venous pressure, urine output, and vasopressin concentrations in renal venous blood were measured in pigs subjected to 12 mmHg of CO2 PP for 150 min. Results: Renal blood flow was decreased at induction of PP and increased during the first 30 min after exsufflation. Renal venous pressure was increased during PP. There was indirect evidence of a decrease in urine output during PP. No changes in renal venous vasopressin concentrations were seen. Conclusion: A CO2 PP of 12 mmHg causes changes in renal hemodynamics and urine output. No changes in vasopressin levels were seen in this pig model, suggesting that other explanations for the observed changes must be sought.     

不同年龄患者腹腔镜胆囊切除术中肾血流量变化的比较

目的 比较不同年龄患者腹腔镜胆囊切除术中肾血流量的变化.方法 择期行腹腔镜胆囊切除术患者60例,年龄18～75岁,ASA分级Ⅰ或Ⅱ级,性别不限,体重48～78 kg,根据年龄分为2组(n=30):中青年组(18～60岁)和老年组(61 ～ 75岁).经口气管插管后置入食管超声探头,分别于气腹前、气腹1、5、10、15、20、30 min、气腹结束后1和5 min时,采用经食管超声心动图测量左肾动脉主干内径(RAD)和血流速度时间积分(VTI),计算左肾血流量(LRAF),记录最大下降时间点,计算最大下降百分比.结果 与气腹前比较,两组气腹各时点和气腹结束后1 min时RAD、VTI和LRAF降低(P＜0.05).与中青年组比较,老年组气腹前LRAF降低,最大下降时间点延迟(P＜0.05),最大下降百分比差异无统计学意义(P＞0.05).结论 中青年患者和老年患者腹腔镜胆囊手术中肾血流量均发生可逆性下降;老年患者最大下降时间延迟.