Decrease In Systemic Blood Pressure Research Articles

Higher perfusion pressure and pump flow during cardiopulmonary bypass are beneficial for kidney function-a single-centre prospective study.

Background: Kidneys play an essential role in the circulatory system, regulating blood pressure and intravascular volume. They are also set on maintaining an adequate filtration pressure in the glomerulus. During the CPB, a decrease in systemic blood pressure and hemoglobin concentration may lead to renal ischemia and subsequent acute kidney injury. Methods: One hundred nine adult patients were prospectively enrolled in this study. The intervention in this study was increasing the flow of the CPB pump to reach the target MAP of > 90mmHg during the procedure. The control group had a standard pump flow of 2.4L/min/m2. Results: Standard pump flow of 2.4L/min/m2 resulted in mean MAP < 90mmHg during the CPB in most patients in the control group. Maintaining a higher MAP during CPB in this study population did not affect CSA-AKI incidence. However, it increased the intraoperative and postoperative diuresis and decreased renin release associated with CPB. Higher MAP during the CPB did not increase the incidence of cerebrovascular complications after the operation; patients in the highest MAP group had the lowest incidence of postoperative delirium, but the result did not obtain statistical significance. Conclusion: Maintaining MAP > 90mmHg during the CPB positively impacts intraoperative and postoperative kidney function. It significantly reduces renal hypoperfusion during the procedure compared to MAP < 70mmHg. MAP > 90mmHg is safe for the central nervous system, and preliminary results suggest that it may have a beneficial impact on the incidence of postoperative delirium.

Проблемні питання патогенезу, діагностики, профілактики та підходи до лікування артеріальної гіпотензії в дітей (літературні дані, власні дослідження)

Arterial hypotension (AHT) is an actual problem in pediatrics. It is a symptom complex characterized by a decrease in systemic blood pressure (BP) and accompanied by a number of clinical symptoms that reflect a decrease in blood flow and perfusion pressure in all organs and tissues. Purpose - to summarize data from the literature and own experience regarding diagnosis, pathogenetic and clinical features of the course and principles of treatment of AHT in children. Results. A review of modern literary data showed a wide range of etiopathogenetic mechanisms of AHT formation and a high specific weight of primary AHT in the pediatric population. A modern method of accurate diagnosis of AHT is daily blood pressure monitoring (DBPM). According to the results of DBPM conducted by us in 677 children aged 8-17 years with complaints of BP fluctuations, AHT was established in 107 (15.8%) examined. AHT in girls occurred almost twice as often compared to boys - 66.4% versus 33.6% (p&lt;0.0001). In 64.5% of cases there was labile AHT, in 33% - stable AHT of the first stage, in 2.5% of children - stable AHT of the II stage. There were no gender differences in the frequency of different degrees of AHT. Conclusions. The issue of low BP is an urgent problem in pediatrics. According to the results of DBPM, AHT is detected in 15.8% of children aged 8-17 years and has a mostly labile course. AHT requires in-depth study in order to develop new preventive and therapeutic measures and to alleviate the consequences in children. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors.

FEATURES OF ARTERIAL PRESSURE IN SCHOOLCHILDREN WITH ACUTE OBSTRUCTIVE BRONCHITIS

Objective – to assess blood pressure indicators in children with acute obstructivebronchitis.Materials and methods. The paper presents the results of a survey of 68 childrenhospitalized for acute obstructive bronchitis. Patients were examined for clinical symptomsand severity of the clinical course according to the BSS-ped scale. BP parameters andechocardiography data were determined and compared with the results of a control groupof healthy individuals (20 children).Results. In patients, the severity of bronchitis clinical course on the fi rst day was average –according to the BSS scale – 7.79±0.19 points. BP indicators in patients were probablylower than in healthy children and had an inverse correlative dependence on the severityof the disease. Echocardiography showed a decrease in the end systolic and diastolicvolume of the left ventricle, a decrease of the pressure gradient in the mitral valve and itsincrease in the pulmonary valve.Conclusions. In acute obstructive bronchitis in children, changes in the activity of thecardiovascular system are observed due to a decrease in systemic blood pressure and anincrease of pressure in the pulmonary circulation system.

Chlortalidone and bumetanide in advanced chronic kidney disease: HEBE-CKD Trial

Abstract Introduction Current treatment for hypertension and volume overload in chronic kidney disease consists of loop diuretics, nevertheless, chronic use leads to adaptive changes at the distal nephron, which in turn decreases their efficacy. The use of thiazide diuretics could be another treatment option in these patients, notwithstanding, there's not enough evidence to justify their use in this population. Purpose To evaluate the efficacy and safety of treatment with bumetanide plus chlorthalidone in in patients with advanced chronic kidney disease. Methods A double-blind randomized controlled trial was conducted at our hospital. Thirty-two patients with hypertension, chronic kidney disease stage IV/V, and chronic loop diuretic use where divided in two groups. The dual treatment group received bumetanide (4 mg QD) plus chlorthalidone (100 mg QD), while the control group was given bumetanide (4 mg QD) plus placebo, both for twenty-eight days. Systemic blood pressure, bioimpedance, and urinary electrolytes were measured at seven and twenty-eight days of treatment. Results There was a significant decrease of systemic blood pressure in the dual treatment group when compared with the control group; systolic blood pressure −26.1±15.3 vs. −10±23.3 mmHg (p=0.028), diastolic blood pressure −13.5±10.7 vs. −3.4±11.9 mmHg (p=0.018), and mean arterial pressure −18.1±8.7 vs. −5.4±14.3 mmHg (p=0.006). There was also a significant decrease of volume overload in the dual treatment group when compared to the control group; total body water −4.36±3.29 vs. +0.075±1.78 litres (p&amp;lt;0.001), extracellular water −2.55±1.1 vs. +0.150±1.2 litres (p&amp;lt;0.001), and extracellular water to total body water ratio −2.92±4.76 vs. −0.24±1.42 (p=0.039). The treatment group increased its fractional excretion of sodium, while the control group demonstrated an increase, though differences were non-significant. As for adverse effects, there was a non-significant increase of urea and creatinine levels in the dual treatment group when compared with controls. Conclusions In advanced chronic kidney disease plus hypertension patients whose treatment with loop diuretics is insufficient, combined use of bumetanide plus chlorthalidone can be useful for systemic blood pressure and volume overload control. Figure 1 Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Hospital General de México

Resuscitative endovascular balloon occlusion of the inferior vena cava is made hemodynamically possible by concomitant endovascular balloon occlusion of the aorta-A porcine study.

Resuscitative endovascular balloon occlusion of the vena cava inferior (REBOVC) may provide a minimal invasive alternative for hepatic vascular and inferior vena cava isolation in severe retrohepatic bleeding. However, circulatory stability may be compromised by the obstruction of venous return. The aim was to explore which combinations of arterial and venous endovascular balloon occlusions, and the Pringle maneuver, are hemodynamically possible in a normovolemic pig model. The hypothesis was that lower-body venous blood pooling from REBOVC can be avoided by prior resuscitative endovascular aortic balloon occlusion (REBOA). Nine anesthetized, ventilated, instrumented, and normovolemic pigs were used to explore the hemodynamic effects of 11 combinations of REBOA and REBOVC, with or without the Pringle maneuver, in randomized order. The occlusions were performed for 5 minutes but interrupted if systolic blood pressure dropped below 40 mm Hg. Hemodynamic variables were measured. Proximal REBOVC, isolated or in combination with other methods of occlusion, caused severely decreased systemic blood pressure and cardiac output, and had to be terminated before 5 minutes. The decreases in systemic blood pressure and cardiac output were avoided by REBOA at the same or a more proximal level. The Pringle maneuver had similar hemodynamic effects to proximal REBOVC. A combination of REBOA and REBOVC provides hemodynamic stability, in contrast to REBOVC alone or with the Pringle maneuver, and may be a possible adjunct in severe retrohepatic venous bleedings.

Comparative Study of Propofol and Etomidate on the Haemodynamic Effects During Induction and Endotracheal Intubation

Introduction: While most intravenous induction agents decrease arterial blood pressure, laryngoscopy and endotracheal intubation increase the heart rate and blood pressure. Propofol causes a decrease in systemic blood pressure whereas etomidate has minimal effects on the cardiovascular system. This study aims to evaluate and compare the hemodynamic effects of propofol and etomidate during induction and endotracheal intubation.&#x0D; Methods: 62 ASA I and II patients, 20-60 years of age, scheduled for elective surgery were enrolled in this prospective, randomised and double blind comparative study. Group A received inj. Propofol (2 mg/kg) and group B received inj. Etomidate (0.3 mg/kg), as induction agents. Heart rate, systolic blood pressure, diastolic blood pressure and mean arterial blood pressure were recorded after induction and after intubation at one, three, five and ten minutes and intergroup comparisons were made.&#x0D; Results: After induction the decrease in systolic, diastolic and the mean arterial pressures were more in group A compared to group B (p = 0.003, 0.004 and 0.002). After 1 minute of intubation all haemodynamic parameters increased from the baseline with no significant differences between the two groups (p &gt;0.05). At three minutes the decrease in heart rate, diastolic blood pressure and mean arterial pressure was more in group A than group B with p values of 0.001, 0.002 and 0.05, however systolic blood pressures showed no significant difference (p = 0.144). The decrease in blood pressures showed significant difference between the two groups (p &lt;0.05) at five and ten minutes but the decrease in heart rate remained significant only at five minutes of intubation (p = 0.001).&#x0D; Conclusions: Propofol and etomidate are both effective in preventing the haemodynamic changes due to induction and endotracheal intubation, with etomidate providing more haemodynamic stability.

Inotropic Effects of Nicorandil on Cardiac Contractility Assessed by Left Ventricular Pressure-Volume Relationship Analyses in Anesthetized Monkeys.

Nicorandil is a representative antianginal drug that has dual properties of a nitrate and adenosine triphosphate-sensitive potassium (KATP) channel agonist; however, its effects on integrated cardiac function have not been fully understood. This study was conducted to clarify the functional, hemodynamic, and electrophysiological effects of nicorandil using ventricular pressure-volume loop analysis in isoflurane-anesthetized monkeys. Nicorandil was given intravenously at therapeutic doses of 0.2 and 2 mg/kg over 10 minutes to cynomolgus monkeys (n = 5) with a pause of 10 minutes between the 2 doses. Nicorandil at 0.2 mg/kg caused decreases in systemic blood pressure and left ventricular end-diastolic pressure by its vasodilating action. Nicorandil at 2 mg/kg also exhibited positive inotropic action demonstrated by increased slopes of preload recruitable stroke work relationship, which is a load-independent inotropic parameter. In load-dependent inotropic parameters, positive inotropy of nicorandil was also indicated by the shortened QA interval and increased contractility index; however, significant changes were not observed in the maximal upstroke velocity of left ventricular pressure. Moreover, reflex tachycardia accompanied by shortening of QT/QTc intervals was observed. Overall, the isoflurane-anesthetized monkey model with pressure-volume loop analysis revealed cardiac variables of nicorandil, including a positive inotropy contributable to cardiac performance in addition to its vasodilatory effect. These findings provide useful information when considering the prescription of nicorandil in patients.

Lithium-induced NDI: acetazolamide reduces polyuria but does not improve urine concentrating ability.

Lithium is the mainstay treatment for patients with bipolar disorder, but it generally causes nephrogenic diabetes insipidus (NDI), a disorder in which the renal urine concentrating ability has become vasopressin insensitive. Li-NDI is caused by lithium uptake by collecting duct principal cells and downregulation of aquaporin-2 (AQP2) water channels, which are essential for water uptake from tubular urine. Recently, we found that the prophylactic administration of acetazolamide to mice effectively attenuated Li-NDI. To evaluate whether acetazolamide might benefit lithium-treated patients, we administered acetazolamide to mice with established Li-NDI and six patients with a lithium-induced urinary concentrating defect. In mice, acetazolamide partially reversed lithium-induced polyuria and increased urine osmolality, which, however, did not coincide with increased AQP2 abundances. In patients, acetazolamide led to the withdrawal of two patients from the study due to side effects. In the four remaining patients acetazolamide did not lead to clinically relevant changes in maximal urine osmolality. Urine output was also not affected, although none of these patients demonstrated overt lithium-induced polyuria. In three out of four patients, acetazolamide treatment increased serum creatinine levels, indicating a decreased glomerular filtration rate (GFR). Strikingly, these three patients also showed a decrease in systemic blood pressure. All together, our data reveal that acetazolamide does not improve the urinary concentrating defect caused by lithium, but it lowers the GFR, likely explaining the reduced urine output in our mice and in a recently reported patient with lithium-induced polyuria. The reduced GFR in patients prone to chronic kidney disease development, however, warrants against application of acetazolamide in Li-NDI patients without long-term (pre)clinical studies.

Effects of Progressive Hypoventilation on Left Ventricular Appearance: An Alternative Etiology of Acute Sonographic Short-Axis D-Shaping.

The purpose of this study was to evaluate the effects of progressive hypoventilation on echocardiographic measures of the left ventricular (LV) appearance in a porcine model. Ten piglets were included in the experimental group, and 5 served as controls. The experimental group underwent 3 interventions of progressive hypoventilation (baseline: tidal volume, 240 mL; respiratory frequency, 16 minutes-1 ; first intervention: tidal volume, 240 mL; respiratory frequency, 8 minutes-1; second intervention: tidal volume, 240 mL; respiratory frequency, 4 minutes-1 ; and third intervention: tidal volume, 120 mL; respiratory frequency, 4 minutes-1 ). Respiratory resuscitation was initiated if the MAP decreased to 50% of the baseline level or at the end of the third intervention. Transthoracic sonography and invasive measurements were obtained throughout. The primary end point was the LV end-diastolic eccentricity index, a measure of LV D-shaping. The median LV end-diastolic eccentricity index increased from 1.1 (interquartile range, 1.0-1.1) at baseline to 1.4 (1.3-1.4) 3 minutes after the third intervention (P < .001) and returned to baseline after resuscitation (P = .093). The MAP declined from 87 mm Hg (81-92 mm Hg) to 50 mmHg (33-66 mm Hg) after initiation of the third intervention (P < .001). The mean pulmonary arterial pressure increased from 20 mm Hg (15-21 mm Hg) to 39 mm Hg (38-40 mm Hg) during the second intervention (P < .001). Progressive hypoventilation led to a marked D-configuration of the LV and a sharp decrease in systemic blood pressure. After respiratory resuscitation, sonographic measures normalized. These findings were explainable by the pressure changes observed within the left and right ventricles.

Hemodynamic effects of sodium bicarbonate administration.

To describe the hemodynamic changes that occur with sodium bicarbonate (NaHCO3) administration in premature neonates. This retrospective study included premature neonates 23 to 31+6 weeks of gestational age who underwent continuous cardiac and cerebral monitoring as participants in prospective trials at our institution, and who received NaHCO3 infused over 30 min in the first 24 h of life. Blood pressure (BP), heart rate, cardiac output (CO), SpO2 and cerebral oximetry (StO2) were captured every 2 s. A baseline was established for all continuous data and averaged over the 10 min before NaHCO3 administration. Baseline was compared with measurements over 10 min epochs until 80 min after administration. Arterial blood gases before and within 1 h of administration were also compared. Significance was set at P<0.05. A total of 36 subjects received NaHCO3 (1.3±0.3 mEq kg-1) in the first 24 h (14±8.5 h) of life. NaHCO3 administration increased pH (7.23 vs 7.28, P<0.01) and decreased base deficit (-8.9 vs -6.8, P<0.01) and PaCO2 (45 vs 43 mm Hg, P<0.05). There was a transient but significant (P<0.05) decrease in systemic BP coinciding with an increase in cerebral oxygenation without an increase in oxygen extraction. CO did not change. Early postnatal NaHCO3 administration does not acutely improve CO but does cause transient fluctuations in cerebral and cardiovascular hemodynamics in extremely premature infants.

64-Year-Old Woman With Diarrhea and Increased Abdominal Girth

64-year-old woman presented to our institution for evaluation of diarrhea and increasing abdominal girth. She had a 1-month history of postprandial diarrhea unrelated to the type of foods she consumed. Her stool was watery, with no evidence of gastrointestinal bleeding. Concurrently, she also noted increasing abdominal girth requiring new pants with a larger waist size. She had no abdominal pain, nausea/vomiting, flushing, light-headedness, or constitutional symptoms. Her medical history was notable for a previous stroke with a mild residual right hand tremor. She was a lifetime nonsmoker, had no history of illicit drug use, and drank alcohol rarely. She had no history of recent travel, infectious exposures, new medications, or herbal supplement intake. Her blood pressure was 136/83 mm Hg, and herheart rate was 98beats/min.Heroxygensaturation was 95% while she breathed room air, and her respiratory rate was 18 breaths/min. Her temperature was 36.9C. Her mental status was normal. Her abdomen was soft, nontender, and mildly distended with hyperactive bowel sounds. Shifting dullness with a fluid wave was present. 1. Which one of the following is the most appropriate diagnostic approach to evaluate the patient’s abdominal symptoms? a. Paracentesis b. Colonoscopy c. Clostridium difficile toxicology screen or polymerase chain reaction d. Serology testing for transglutaminase antibody e. Abdominal radiography

Estenose arterial subclávia bilateral: mais do que uma descida da tensão arterial – Relato de caso

Introduction: Chronic ischaemia of the upper extremities is rare, particularly when it is bilateral. Depending on the existence and location of collateral vessels, it may remain asymptomatic or it may present with symptomatic ischemia of the upper limbs and a high risk of coronary and cerebrovascular disease. Although the diagnosis is made by ultrasonography, the physical examination may reveal abnormalities, including differences in blood pressure values between both arms with unilateral occlusion. In this case report, blood pressure values were consistently low bilaterally, which led to an erroneous initial approach based on a presumed decrease in systemic blood pressure. Case description: The authors describe the case of a 77 year old female patient, with controlled hypertension and dyslipidaemia, who presented with brachial blood pressure (BP) measurements consistently lower than 90/60 mmHg, as well as complaints of fatigue with movements of the upper extremities. In the absence of other abnormalities, changes were made to the dose of her anti-hypertensive medication, without clinical improvement. After a few months without change in the clinical situation, the physical examination revealed a bilateral decrease in radial pulses and an increase in the ankle-brachial index, suggesting occlusive upper extremity arterial disease. This was confirmed by an arterial Doppler ultrasound, which revealed bilateral occlusion of the subclavian arteries. Comment: Blood pressure measurements were erroneously low because they were made at the brachial artery in a patient with a bilateral occlusion of the subclavian arteries. In these cases, the evaluation of BP based solely on brachial measurements may lead to an incorrect approach. It is important to integrate other signs and symptoms as well as a more complete physical examination when evaluating a possible diagnosis of this condition.

Role of VPAC2 receptor in monocrotaline-induced pulmonary hypertension in rats.

Pulmonary hypertension (PH) is associated with significant morbidity and mortality. Vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase activating peptide (PACAP) have pulmonary vasodilatory and positive inotropic effects via receptors VPAC1 and VPAC2, which possess a similar affinity for both peptides, and PAC1, a PACAP-preferring receptor. VIP is a promising option for PH treatment; however, various physiological effects of VIP have limited its clinical use. We investigated the effects of VPAC1 and VPAC2 selective agonists VIP and PACAP to explore more appropriate means of treatment for PH. We examined hemodynamic changes in right ventricular systolic pressure (RVSP), systemic blood pressure (SBP), total pulmonary resistance index (TPRI), total systemic resistance index, and cardiac index (CI) in response to their agonists with monocrotaline (MCT)-induced PH and explored involvement of VIP/PACAP expression and receptors in PH. Sprague-Dawley rats were divided into the MCT group (administered MCT 60 mg/kg) and control group. In MCT-induced PH, decreased VIP and PACAP were associated with upregulation of VPAC1, VPAC2, and PAC1 in lung tissues. Intravenous injection of VPAC2-selective agonist BAY 55-9837 and VIP, but not [Ala(11,22,28)]VIP, improved the CI. The decrease in SBP with VPAC2 agonist was significantly less than that in the control. Although they decreased SBP, these agonists hardly affected RVSP in the control. Activation of VPAC2 receptor with BAY 55-9837 effectively improved RVSP, TPRI, and CI in MCT-induced PH, suggesting a VPAC2 agonist as a possible promising treatment for PH.

Hemodynamic response to fluid management in children undergoing dexmedetomidine sedation for MRI.

Dexmedetomidine is administered for pediatric sedation for MRI studies. It has the advantage of preserving respiratory function and producing a sedation state identical to that of natural sleep. It can, however, cause a dose-dependent decrease in systemic blood pressure in children. The purpose of this study was to investigate whether i.v. fluid loading with normal saline solution before the initiation of dexmedetomidine administration would affect the frequency of hypotension. Quality assurance data on consecutively registered children who were sedated with dexmedetomidine for MRI were reviewed. All children received a bolus of 3 μg/kg dexmedetomidine followed by a continuous infusion of 2 mg/ kg/h. A normal saline fluid bolus consisting of 0, 10, or 20 mL/kg was administered to each child within 1 hour before initiation of dexmedetomidine administration. Hypotension was defined as a greater than 20% decrease in mean arterial blood pressure from baseline. Sedation was administered to 1692 children. Data on fluid administration were missing in three cases. In the other cases, 252 (14.9%) children received 0 mL/kg of normal saline solution, 598 (35.3%) received 10 mL/kg, and 839 (49.6%) received 20 mL/kg. In a multiple logistic regression model controlled for confounding variables, the odds of development of hypotension with 10 mL/kg of fluid decreased 53% (odds ratio, 0.47; 95% CI, 0.28-0.79; p = 0.004) compared with 0 mL/kg. Administration of 10 mL/kg of normal saline solution before the initiation of dexmedetomidine administration for pediatric MRI sedation is effective in decreasing the incidence of observed hypotension.

Permeability and contractile responses of collecting lymphatic vessels elicited by atrial and brain natriuretic peptides

Atrial and brain natriuretic peptides (ANP and BNP, respectively) are cardiac hormones released into the bloodstream in response to hypervolaemia or fluid shifts to the central circulation. The actions of both peptides include natriuresis and diuresis, a decrease in systemic blood pressure, and inhibition of the renin-angiotensin-aldosterone system. Further, ANP and BNP elicit increases in blood microvessel permeability sufficient to cause protein and fluid extravasation into the interstitium to reduce the vascular volume. Given the importance of the lymphatic vasculature in maintaining fluid balance, we tested the hypothesis that ANP or BNP (100 nM) would likewise elevate lymphatic permeability (Ps) to serum albumin. Using a microfluorometric technique adapted to in vivo lymphatic vessels, we determined that rat mesenteric collecting lymphatic Ps to rat serum albumin increased by 2.0 ± 0.4-fold (P = 0.01, n = 7) and 2.7 ± 0.8-fold (P = 0.07, n = 7) with ANP and BNP, respectively. In addition to measuring Ps responses, we observed changes in spontaneous contraction amplitude and frequency from the albumin flux tracings in vivo. Notably, ANP abolished spontaneous contraction amplitude (P = 0.005) and frequency (P = 0.006), while BNP augmented both parameters by ∼2-fold (P < 0.01 each). These effects of ANP and BNP on contractile function were examined further by using an in vitro assay. In aggregate, these data support the theory that an increase in collecting lymphatic permeability opposes the absorptive function of the lymphatic capillaries, and aids in the retention of protein and fluid in the interstitial space to counteract volume expansion.

Acute cor pulmonale in ARDS

Acute cor pulmonale in ARDS

Diuretics in Meniere disease: A therapy or a potential cause of harm?

Despite the lack of clear evidence for their effectiveness in treating vertigo, tinnitus, hearing loss and aural fullness, diuretics, represent a common treatment for Meniere disease (MD), as they are supposed to decrease volume and pressure in the endolymphatic partition of the labyrinth. Our group have outlined the possibility of an adverse effect on inner ear function derived from an abrupt lowering of blood pressure: a subsequent exaggerated vasomotor response inducing local ischemia could be responsible for more or less permanent damage. The inner ear, owing both to its terminal vascular supply and to the necessity of a steady metabolism, seems a reliable target for any hemodynamic imbalance that acutely affect its perfusion. In our opinion, the complexity of the inner ear anatomy and function argues against the usefulness of diuretics to reduce endolymphatic volume, in analogy to their effect on the volemia: too many active mechanisms and “buffer” systems are involved in the labyrinth. Even considering that the finding of mean low pressure values is relatively common in subjects with MD, an attempt should be to maintain a stable blood perfusion to the labyrinth; in fact, an abrupt decrease in systemic blood pressure can trigger an adverse sympathetic reaction and transmit misleading information to the cochlear vasopressin receptors.

Comparison of the autoregulatory mechanisms between central retinal artery and posterior ciliary arteries after thigh cuff deflation in healthy subjects

PurposeTo compare dynamic autoregulation in the Central Retinal Artery (CRA) and the Posterior Ciliary Arteries (PCAs) after a step decrease in systemic blood pressure. MethodsTen healthy male young subjects were studied. Flow velocities in retrobulbar vessels and systemic blood pressure were recorded in each subject before, during, and after a step decrease in blood pressure. Continuous blood pressure recordings were made with a finger plethysmograph system and flow velocities in the CRA and the PCAs were continuously measured with color Doppler imaging. Large bilateral thigh cuffs were inflated and a pressure approximately 20 mm Hg above peak systolic blood pressure was maintained for 3 minutes. A decrease in blood pressure was induced by rapid deflation of bilateral thigh cuffs. Experiments were performed separately for the CRA and the PCAs. ResultsSystemic blood pressure showed a step decrease between −9% and −12% (p<0.001 each) immediately after thigh cuff release and returned to baseline 6 to 7 pulse cycles later. Peak systolic flow velocity in the CRA decreased by −10±7% (p=0.043) and returned to baseline earlier than systemic blood pressure, showing a delay of 3 pulse cycles after the blood pressure decrease. Peak systolic and end diastolic flow velocities in the PCAs decreased by −13±3% (p=0.004) and by −10±1% (p=0.0009), respectively and returned to baseline with a comparable time course to systemic blood pressure, reflecting no change in peripheral vascular resistance. There was a statistically significant difference in the time course of the velocity changes in the two selected arteries after thigh cuff release (p=0.008). ConclusionsThe results of the present study indicate differences in the autoregulatory behavior of the vascular beds peripheral to the CRA and the PCAs. Our data indicate that the vascular bed distal to the CRA shows better autoregulatory properties as compared to the PCAs. Whether this is related to a myogenic mechanism remains to be investigated. The thigh cuff technique represents an interesting approach to study dynamic autoregulation in the human eye.

Effect of indomethacin on the blood pressure and plasma catecholamine responses to acute endotoxaemia.

Injection of E. coli endotoxin (7 mg kg-1 i.v.) to pentobarbitone anaesthetized cats resulted in prolonged decrease of systemic blood pressure and increases in plasma concentrations of adrenaline, noradrenaline and 6-ketoprostaglandin (PG) F 1 alpha. Indomethacin pretreatment (10 mg kg-1 i.v.) attenuated the decrease in blood pressure following endotoxin injection. Plasma adrenaline, noradrenaline and 6-keto-PG F1 alpha were significantly lower in the indomethacin-treated cats. These data indicate that the superior haemodynamic status of the indomethacin pretreated animals exposed to endotoxic shock is not the result of potentiation of the peripheral sympathetic response.

Physiologic response of human brain death and the use of vasopressin for successful organ transplantation

The dynamic physiologic response of human brain death and the impact of vasopressin on successful organ transplantation is reported. A 60-year-old woman was admitted to the intensive care unit after severe traumatic brain injury resulting in brain death. Initial Cushing reflex was followed by a precipitous decrease in systemic blood pressure that was refractory to the alpha-agonist phenylephrine. After intravenous vasopressin was given, hemodynamic stability was restored and maintained until successful organ transplantation. Vasopressin, a catecholamine-sparing vasopressor and antidiuretic agent, may be an effective agent in the treatment of refractory hypotension after brain death prior to organ transplantation.