Baroreceptor-mediated reduction of jejunal mucosal perfusion, evaluated with endoluminal laser Doppler flowmetry in conscious humans

Risk Factors for Acute Hemorrhagic Rectal Ulcer Syndrome and Its Prognosis: A Density Case-Control Study

Acute hemorrhagic rectal ulcer syndrome (AHRUS) can cause fatal gastrointestinal bleeding. However, there have been few epidemiological studies investigating risk factors of AHRUS. To determine the risk factors and predict one-year survival after onset of AHRUS, we conducted a retrospective density case-control study in a tertiary referral hospital. Patients with hematochezia, bloody stool, and rectal ulcer confirmed by colonoscopy between 2003 and 2011 were diagnosed as AHRUS (n = 38). Patients with malignancies, infectious colitis, ulcerative colitis, or solitary rectal ulcer syndrome were excluded. Control subjects (n = 123) without rectal ulcer were selected by risk set sampling for each AHRUS. Multivariate logistic regression analyses revealed that the significant adjusted odds ratio (95% confidence interval) of hospitalization, antithrombotic drug use, and one gram increase of serum albumin was 15.7 (2.25–108.9), 12.1 (1.53–94.4), and 0.11 (0.02–0.52), respectively. Endoscopic hemostasis for rectal bleeding was performed in 8 cases (21%). Seventeen percent of patients died within one year after the episode of AHRUS from non-AHRUS causes. This study revealed that hospitalization, antithrombotic drug use, and lower serum albumin value were significant risk factors for AHRUS, and that AHRUS was an unfavorable prognostic condition. This information could be helpful in recognizing high-risk patients of rectal bleeding and applying preventive measures.

Rectal ischemia mimicked tumor mass

Ischemic proctitis is a rare disease which is usually encountered in elderly with comorbidities. We present a case of an 80-year old man with severe coronary disease who presented with severe hematochezia and hypotension. Endoscopy revealed a rectal mass 3-4 cm above the dental line and rectosigmoid mucosal inflammation compatible with ischemic colitis. The rectal insult was so intense that it resembled a neoplasmatic lesion. We discuss the causes, the prognostic factors, and the clinical and therapeutic challenges of this rare, albeit life-threatening entity, and we review the relative literature. A percentage of 10%–20% of patients with ischemic colitis usually have a distal potentially obstructing lesion or disorder such as cancer, diverticulitis or fecal impaction. Ischemic colitis, when mucosal and submucosal edema is severe and hemorrhagic nodules are large enough, can mimic a neoplasmatic lesion. The best treatment approach is a conservative management initially with a close clinical followup and after stabilization a repetition of rectal endoscopy with new biopsies. Early recognition of this clinical entity is of paramount importance to implement appropriate therapy (conservative or surgical) and avoid potentially fatal treatment of presumed inflammatory or infectious bowel diseases.

An unusual case of hematochezia: acute ischemic proctosigmoiditis

Acute ischemia of the rectum is uncommon and usually occurs after aorto-iliac surgery. In this report, we present a case of acute ischemic proctosigmoiditis that developed from a brief episode of hypotension. An 85-year-old male presented to the emergency room with hypotension, mental confusion, and passage of maroon-colored stool. He was resuscitated and treated for presumed sepsis. Computerized tomography of the abdomen and pelvis displayed signs of acute inflammation of the distal colon and rectum. Endoscopic findings and microscopic examination of the rectal biopsy revealed changes consistent with acute ischemic proctosigmoiditis. An evaluation for infectious etiologies was negative. The patient's clinical condition improved over the next 24 h with supportive care. Involvement of the rectum is rare in ischemic colitis because of its abundant collateral blood supply. Acute ischemic proctosigmoiditis should be considered in the differential diagnosis of elderly patients with multiple co-morbidities presenting with hematochezia.

Laser-Doppler flowmetry reveals rapid perfusion changes in adipose tissue of lean and obese females

The present study aimed to evaluate adipose tissue blood flow (ATBF) by means of laser-Doppler flowmetry (LDF) in humans. Lower body negative pressure (LBNP) and straining known to affect epidermal blood flow through the autonomic nervous system were performed in 11 lean and 11 obese female volunteers. ATBF changes were compared between both groups and also discriminated from skin blood flow (SBF) responses of the immediate vicinity. Additionally, LDF measurements were compared with flow measurements using (133)xenon washout in 10 lean subjects during whole body cooling. LDF estimations of SBF and ATBF showed a positive correlation to (133)Xe during cooling. SBF and ATBF were reduced to the same extent in both lean and obese subjects during LBNP. Straining induced divergent changes in SBF and ATBF: initially SBF decreased while ATBF increased, but toward the end of straining SBF increased above baseline and ATBF returned down to baseline level. Those changes were similar in both weight groups. Interestingly, only in obese subjects, both LBNP and straining were followed by ATBF augmentation, while SBF levels remained stable. In conclusion, LDF compares with (133)Xe washout in monitoring ATBF during tonic perfusion changes. Its strength, however, lies in the detection of rapid flow alterations within the subcutaneous tissue, allowing the evaluation of reflex responses of the subcutaneous microcirculation. Interestingly, those rapid changes in SBF and ATBF can be both concordant and discordant. With regard to ATBF, vasoconstrictor components of the reflex responses were similar in lean and obese subjects, whereas vasodilatory responses were more pronounced in obese volunteers.

Management of ischemic proctitis with severe rectal haemorrhage: A case report

Acute ischemic proctitis is a rare pathological condition. We report here a patient presented with massive rectal haemorrhage from a bleeding vessel superimposed on an underlying pathology of ischemic proctitis. This case report illustrates the difficulties in making the clinical distinction between ischemic proctitis and other pathological entities. We also discussed the beneficial role of arteriogram with embolotherapy as an effective therapeutic measure in the management of lower gastrointestinal bleeding. The literature on the subject is reviewed.

Autoregulation of Human Jejunal Mucosal Perfusion During Cardiopulmonary Bypass

Animal studies have suggested that autoregulation of intestinal blood flow is severely impaired during cardiopulmonary bypass (CPB). We investigated the jejunal mucosal capacity to autoregulate perfusion during nonpulsatile CPB (34 degrees C) in 10 patients undergoing elective cardiac surgery. Changes in mean arterial blood pressure (MAP) were induced by altering the CPB flow rate randomly for periods of 3 min from 2.4 L/min/m2 to either 1.8 or 3.0 L/min/m2. Jejunal mucosal perfusion (JMP) was continuously recorded by laser Doppler flowmetry. A typical pattern of flow motion (vasomotion) was recorded in all patients during CPB. Variations in CPB flow rates caused no significant changes in mean JMP, jejunal mucosal hematocrit, or red blood cell velocity within a range of MAP from 50 +/- 15 to 74 +/- 16 mm Hg. The vasomotion frequency and amplitude was positively correlated with CPB flow rate. IV injections of prostacyclin (10 microg, Flolan) blunted vasomotion and increased JMP from 192 +/- 53 to 277 +/- 70 (P < 0.05) perfusion units despite a reduction in MAP from 59 +/- 12 to 45 +/- 10 mm Hg (P < 0.05). Prostacyclin-induced vasodilation resulted in loss of mucosal autoregulation (pressure-dependent perfusion). We conclude that autoregulation of intestinal mucosal perfusion is maintained during CPB in humans.

Vasopressors and intestinal mucosal perfusion after cardiac surgery: Norepinephrine vs. phenylephrine

OBJECTIVES

To evaluate the potential differential effects of norepinephrine, an alpha1-, beta1-, and beta2-receptor agonist, to the alpha1-agonist phenylephrine on jejunal mucosal perfusion, gastric-arterial PCO2 gradient, and the global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A randomized, prospective, interventional crossover study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Ten patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

Each patient received randomly and sequentially norepinephrine (0.052+/-0.009 microg/kg/min) and phenylephrine (0.50+/-0.22 microg/kg/min) to increase mean arterial blood pressure by 30%.

MEASUREMENTS AND MAIN RESULTS

Data on jejunal mucosal perfusion, jejunal mucosal hematocrit, and red blood cell velocity (laser Doppler flowmetry) as well as gastric-arterial Pco2 gradient (tonometry) and splanchnic oxygen extraction were obtained before (control) and during a 30-min drug infusion period after the target mean arterial blood pressure was reached. The procedure was sequentially repeated for the second vasopressor. Both drugs induced a 40-46% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, jejunal mucosal hematocrit, red blood cell velocity, nor gastric-arterial Pco2 gradient was affected by any of the vasopressors. Splanchnic oxygen extraction increased from 38.2% to 43.1% (p<.001) with norepinephrine and from 39.3% to 47.5% (p<.001) with phenylephrine. This increase was significantly more pronounced with phenylephrine compared with norepinephrine (p<.05). Mixed venous-hepatic vein oxygen saturation gradient increased with both drugs (p<.01), and the increase was more pronounced with phenylephrine (p<.05). Splanchnic lactate extraction was not significantly affected by any of the vasopressors.

CONCLUSIONS

Phenylephrine induced a more pronounced global alpha1-mediated splanchnic vasoconstriction compared with norepinephrine. Neither of the vasoconstrictors impaired perfusion of the gastrointestinal mucosa in postcardiac surgery patients. The lack of norepinephrine-induced, alpha1-mediated impairment of gastrointestinal perfusion is not explained by a beta2-mediated counteractive vasodilation but instead by possible mucosal autoregulatory escape.

Cardiopulmonary bypass in humans--jejunal mucosal perfusion increases in parallel with well-maintained microvascular hematocrit

BACKGROUND

An imbalance between splanchnic oxygen supply and demand occurs during cardiopulmonary bypass (CPB) in man, which might disrupt the intestinal mucosal barrier function. The aim of the present study was to evaluate the effects of mild hypothermic CPB on intestinal mucosal perfusion in man undergoing cardiac surgery. Additionally we aimed to identify variables, which independently could predict changes of intestinal mucosal microcirculatory variables during CPB.

METHODS

Jejunal mucosal perfusion (JMP), jejunal mucosal hematocrit (JMHt), red blood cell (RBC) velocity and arteriolar vasomotion using endoluminal jejunal laser Doppler flow metry were studied in eight cardiac surgical patients before and during CPB at a temperature of 34 degrees C.

RESULTS

Cardiopulmonary bypass and the accompanied hemodilution (25-30%) induced a 44% increase in JMP (P < 0.05) and a 42% increase in RBC velocity (P < 0.01), with no change in JMHt. The oscillation amplitude of JMP, at a fundamental frequency of 2.8 cycles min(-1), increased with 175% (P < 0.05) during CPB. Splanchnic oxygen extraction increased by 64% during CPB (P < 0.05). Stepwise multiple regression analysis identified systemic hematocrit, arterial O2 and CO2 tension and splanchnic oxygen extraction as independent predictors of RBC velocity during CPB (R2=0.63, P < 0.001). The oscillation amplitude of JMP was predicted by RBC velocity and splanchnic oxygen extraction (R2= 0.68, P <0.0001).

CONCLUSIONS

The increase in RBC velocity and enhanced arteriolar vasomotion, as well as maintained jejunal mucosal hematocrit, are microcirculatory, compensatory mechanisms for the splanchic oxygen supply/demand mismatch seen during cardiopulmonary bypass in humans.

Effects of norepinephrine alone and norepinephrine plus dopamine on human intestinal mucosal perfusion

OBJECTIVES

To evaluate the effect of norepinephrine alone and norepinephrine combined with dopamine on jejunal mucosal perfusion, gastric-arterial pCO(2) gradient, and global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A prospective interventional study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Eighteen patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

After control measurements, each patient received norepinephrine (50+/-26 ng.kg.min) to increase mean arterial blood pressure by 30% followed by addition of low-dose dopamine (2.6+/-0.3 microg x kg x min). Postdrug control measurements were performed 120 min after discontinuation of the catecholamines.

MEASUREMENTS AND RESULTS

Norepinephrine induced a 32% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, assessed by laser Doppler flowmetry, nor gastric-arterial pCO(2) gradient (tonometry) was affected by norepinephrine. Splanchnic O(2)-extraction increased ( P<0.05) and this increase was positively correlated to the individual dose of norepinephrine ( r = 0.78, P<0.0001). Splanchnic lactate extraction was increased by norepinephrine ( P<0.05). None of the patients had splanchnic lactate production during norepinephrine infusion. The addition of dopamine increased cardiac index by 27% ( P<0.001) and decreased splanchnic O(2 )extraction. Dopamine increased jejunal mucosal perfusion by 32% ( P<0.001) while the gastric-arterial pCO(2) gradient remained unchanged.

CONCLUSIONS

Vasopressor therapy with norepinephrine after cardiac surgery did not jeopardize intestinal mucosal perfusion in spite of a dose-dependent increase of the global splanchnic oxygen demand-supply relationship. The addition of dopamine increased intestinal mucosal perfusion.

Do lung recruitment maneuvers decrease gastric mucosal perfusion?

OBJECTIVE

To evaluate effects of lung recruitment maneuvers on gastric mucosal perfusion, systemic circulation, and lung mechanics in patients with acute lung injury.

DESIGN

Prospective observational clinical study. SETTING. General intensive care unit of university hospital.

PATIENTS AND PARTICIPANTS

Fourteen patients with acute lung injury (ten in the main study group and four in a validation group). INTERVENTIONS. Three 2-min-long recruitment maneuvers (RM) with transient increases in mean airway pressure to 35 cmH(2)O (RM1 and RM2) and 44 cmH(2)O (RM3).

MEASUREMENTS AND RESULTS

Measurements of systemic hemodynamics, gastric mucosal perfusion (laser Doppler flowmetry), and lung mechanics were performed immediately before, at the end of, and 3 min after each RM. Cardiac index decreased during all RMs while mean arterial pressure decreased only during RM3. Gastric mucosal perfusion was not significantly changed during any of the RMs. When comparing values obtained before the first RM with values after the third RM there was a significant decrease in cardiac index ( P=0.043) and a non-significant ( P=0.051) decrease in gastric mucosal perfusion. There were no significant changes in systemic oxygenation or lung mechanics after three RMs, even though four patients showed marked transient increases in systemic oxygenation during RMs.

CONCLUSIONS

In this study of ten patients there were no significant changes in gastric mucosal perfusion during lung recruitment maneuvers. There was, however, a trend towards gradual decreases in gastric mucosal perfusion.

Pathogenesis of rotavirus diarrhea

Rotavirus diarrhea is a major cause of infantile gastroenteritis worldwide. This review is mainly devoted to the effects of Rotavirus on intestinal epithelial transport and to the pathophysiological mechanisms proposed to underlie the intestinal fluid secretion caused by the virus.

Jejunal mucosal perfusion is well maintained during mild hypothermic cardiopulmonary bypass in humans

In the present study, the effects of mild hypothermic (34 degrees C) cardiopulmonary bypass (CPB) on jejunal mucosal perfusion (JMP), gastric tonometry, splanchnic lactate, and oxygen extraction were studied in low-risk cardiac surgical patients (n = 10), anesthetized and managed according to clinical routine. JMP was assessed by endoluminal laser Doppler flowmetry. Patients were studied during seven 10-min measurement periods before, during, and 1 h after the end of CPB. Splanchnic oxygen extraction increased during hypothermia and particularly during rewarming and warm CPB. JMP increased during hypothermia (26%), rewarming (31%), and warm CPB (38%) and was higher 1 h after CPB (42%), compared with pre-CPB control. The gastric-arterial PCO(2) difference was slightly increased (range 0.04-2.26 kPa) during rewarming and warm CPB as well as 1 h after CPB, indicating a mismatch between gastric mucosal oxygen delivery and demand. None of the patients produced lactate during CPB. We conclude that jejunal mucosal perfusion appears well preserved during CPB and moderate (34 degrees C) hypothermia; this finding is in contrast to previous studies showing gastric mucosal hypoperfusion during CPB.

IMPLICATIONS

Jejunal mucosal perfusion increases during mild hypothermic cardiopulmonary bypass (CPB). Intestinal laser Doppler flowmetry, gastric tonometry, and measurements of splanchnic lactate extraction could not reveal a local or global splanchnic ischemia during or after CPB. A mismatch between splanchnic oxygen delivery and demand was seen, particularly during rewarming and warm CPB.

Jejunal and gastric mucosal perfusion versus splanchnic blood flow and metabolism: an observational study on postcardiac surgical patients

OBJECTIVES

To evaluate the association between changes in total splanchnic and mucosal perfusion, assessed either by gastric tonometry or jejunal laser Doppler flowmetry in postcardiac surgical patients.

DESIGN

A prospective, observational study.

SETTINGS

A general intensive care unit in a tertiary care center.

PATIENTS

Twelve, postoperative cardiac surgery patients were studied.

INTERVENTIONS

Patients were treated according to clinical routine. Total splanchnic blood flow (indocyanine green extraction), jejunal mucosal perfusion (laser Doppler flowmetry), gastric mucosal-arterial PCO2 gradients, and splanchnic lactate uptake were studied during four 30-min measurements periods, each separated by a period of 1 hr.

MEASUREMENTS AND MAIN RESULTS

There was no consistent association between either total splanchnic and local mucosal perfusion or between gastric and jejunal perfusion as assessed by two different techniques. The PCO2 gradient increased from 0.73+/-0.21 kPa to 1.15+/-0.30 kPa (p < .05), and splanchnic oxygen extraction increased from 40%+/-9% to 49%+/-14% (p < .01).

CONCLUSIONS

In this observational study on postcardiac surgical patients, local mucosal perfusion did not reflect total splanchnic blood flow and vice versa. Either changes in gastric and jejunal mucosal perfusion were different or increasing tissue metabolism was responsible for the observed lack of association between tonometry, laser Doppler flowmetry, and total splanchnic blood flow. Increasing mucosal arterial PCO2 gradient and splanchnic oxygen extraction may reflect a mismatch between splanchnic perfusion and metabolic demands.

Differential effects of dopamine, dopexamine, and dobutamine on jejunal mucosal perfusion early after cardiac surgery

OBJECTIVE

To evaluate the potential differential effects of dopamine, dopexamine, and dobutamine on jejunal mucosal perfusion, assessed by endoluminal laser Doppler flowmetry in uncomplicated postcardiac surgical patients.

DESIGN

A prospective, blinded, randomized, crossover study.

SETTING

A cardiothoracic intensive care unit in a tertiary care center.

PATIENTS

A total of ten postoperative cardiac surgical patients were studied.

INTERVENTIONS

Each patient received sequentially, randomly, and in a blinded fashion 2.7+/-0.2 microg x kg(-1) x min(-1) dopamine, 0.7+/-0.1 microg x kg(-1) x min(-1) dopexamine, and 2.7+/-0.1 microg x kg(-1) x min(-1) dobutamine. Each inotropic agent was titrated to increase cardiac output by 25% from baseline. Data on jejunal mucosal perfusion, splanchnic lactate, and oxygen extraction were obtained during a 5-min control period and a 5-min drug infusion period after the target cardiac output was reached. The procedure was sequentially repeated for each agent, and there was a 20- to 30-min washout period between each agent.

MEASUREMENTS AND MAIN RESULTS

Dopamine, dopexamine, and dobutamine increased jejunal mucosal perfusion by 27% (p < .01), 20% (p < .001), and 7% (p < .001), respectively. The increase in jejunal mucosal perfusion by dopamine and dopexamine were significantly more pronounced compared with dobutamine (p < .05 and p < .01, respectively), whereas there was no difference between dopamine and dopexamine. Splanchnic oxygen extraction decreased to the same extent with all three drugs. Splanchnic lactate extraction did not change for any of the drugs. The effects on central hemodynamics were similar for the three inotropic agents.

CONCLUSIONS

Endoluminal laser Doppler flowmetry is a new tool for the detection of perfusion changes at the local intestinal mucosal level. Dopamine, dopexamine, and dobutamine have differential effects on jejunal mucosal perfusion probably because of their different receptor stimulating properties. These findings may be of clinical importance when the therapeutic goal is to improve gut mucosal perfusion.

Specific angiotensin II receptor blockage improves intestinal perfusion during graded hypovolemia in pigs

OBJECTIVE

To investigate the potential of specific angiotensin II subtype 1 (AT1) receptor blockade to modify the mesenteric hemodynamic response to acute hypovolemia and retransfusion.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

University-affiliated animal research laboratory.

SUBJECTS

Fasted, anesthetized, ventilated, juvenile domestic pigs of both sexes.

INTERVENTIONS

Acute, graded hypovolemia by 20% and 40% of the total estimated blood volume followed by retransfusion in control animals (CTRL; n = 10) and animals pretreated with the AT1 receptor blocker candesartan (CAND; n = 10).

MEASUREMENTS AND MAIN RESULTS

Invasive monitoring of arterial and central venous blood pressures, cardiac output, portal venous blood flow, and jejunal mucosal blood flow. Blood gases were repeatedly analyzed to calculate oxygen delivery and consumption. Thirty minutes after each level of hypovolemia at 20% and 40%, cardiac output was decreased in CTRL animals from a baseline of 2.9 +/- 0.1 to 1.8 +/- 0.2 and 1.1 +/- 0.2 L/min, with no differences compared with CAND animals. Cardiac output was restored to 3.0 +/- 0.3 L/min 30 mins after retransfusion in CTRL animals, with no significant intergroup differences. Baseline portal venous blood flow (Q(MES)) and jejunal mucosal perfusion (PU(JEJ)) were greater in CAND animals compared with CTRL animals. During graded hypovolemia, CAND animals maintained Q(MES) and PU(JEJ) at significantly higher levels compared with CTRL animals, particularly after 40% hemorrhage (+221% and + 244%, respectively, relative to the mean values in CTRL animals). The same pattern was observed after retransfusion. Moreover, the calculated mesenteric critical oxygen delivery was significantly greater in CTRL animals (74 mL/min) compared with CAND animals (34 mL/min). No animals died in the CAND group, whereas four animals died during 40% hypovolemia or retransfusion in the CTRL group.

CONCLUSIONS

Specific AT1 blockade before acute hypovolemia significantly ameliorated mesenteric and, in particular, jejunal mucosal hypoperfusion. In addition, cardiovascular stability was improved, and mortality in conjunction with acute hypovolemia and retransfusion could be completely avoided. These findings support a fundamental role of the renin-angiotensin system in the mesenteric response to acute hypovolemia and indicate a substantial interventional potential for candesartan in conjunction with circulatory stress.