Acute Hypotension Research Articles

Dynamic Cerebral Autoregulation and Monitoring Cerebral Perfusion

Cerebral autoregulation (CA) describes the capability of the brain to maintain its flow as relatively stable over a wide rage of mean arterial pressures (MAPs), for example, from 60 to 150 mm Hg. Because the brain is encompassed in the skull, CA is vital for preventing cerebral edema and hemorrhage, as illustrated in some patients experiencing acute liver failure.1 Also, CA counteracts the effect on cerebral blood flow (CBF) of a reduction in MAP in response to, for example, hemorrhage or a change in body position. Yet, when rising from a supine or seated position, one sometimes experiences symptoms indicative of a reduced CBF, like blurred vision.2 Thus, CA is of general clinical interest. For example, diabetic patients have increased risk of developing ischemic or hemorrhagic stroke, and in some diabetic patients CA is affected. Evidence for CA was provided in the 1930s when Fog,3 through a cranial window, observed the pial artery reaction to manipulation of MAP. For humans, CBF was measured with introduction of the method of Kety-Schmidt in 1948,4 and it was used in 1954 by Finnerty et al5 to determine cerebral hemodynamics of the ischemic brain after an acute reduction in MAP in attempt to define what now would be considered the lower limit of CA. However, it was the review by Lassen6 that introduced the concept of CA by plotting CBF against MAP to illustrate the relative stability of CBF over a wide range of blood pressure. Also, the lower and upper limits of CA were identified by a decrease in CBF at a low MAP and an increase …

Acute hypotension associated with leucocyte depletion filters during cell salvaged blood transfusion

Summary Intra-operative cell salvage is used in more than 75% of NHS hospitals in the United Kingdom and is a safe and cost effective alternative to allogenic blood transfusion. We report a case of acute hypotension during reinfusion of cell salvaged blood through a leucocyte depletion filter that occurred during a caesarean section. We review the literature of hypotension associated with the use of bedside leucocyte depletion filters.

Echocardiographic diagnosis, management and monitoring of pulmonary embolism with right heart thrombus in a patient with myotonic dystrophy: a case report

Acute pulmonary embolism (PE) is a common disease which frequently results in life-threatening right ventricular (RV) failure. High-risk PE, presenting with hypotension, shock, RV dysfunction or right heart thrombus is associated with a high mortality, particularly during the first few hours. Accordingly, it is important to commence effective therapy as soon as possible. In the case described in this report, a 49-year-old woman with myotonic dystrophy type 1 presented with acute respiratory failure and hypotension. Transthoracic echocardiography showed signs of right heart failure and a mobile right heart mass highly suspicious of a thrombus. Based on echocardiographic findings, acute thrombolysis was performed resulting in hemodynamic stabilization of the patient and complete resolution of the right heart thrombus. This case underscores the important role of transthoracic echocardiography for the diagnosis, management and monitoring of PE and underlines the efficacy and safety of thrombolysis in the treatment of PE associated with right heart thrombus.

The Clock Is Ticking: The Case for Achieving More Rapid Control of Hypertension

The Clock Is Ticking: The Case for Achieving More Rapid Control of Hypertension

Changes of some amino acid concentrations in the medial vestibular nucleus of conscious rats following acute hypotension

Microdialysis and high performance liquid chromatography (HPLC) were used to measure the changes of certain amino acids in the medial vestibular nucleus (MVN) of conscious rats in order to understand whether those amino acids are involved in the regulation of blood pressure. Acute hypotension was induced by infusing sodium nitroprusside (SNP) into the femoral vein. In the control group, glutamate (Glu) release increased, though γ-aminobutyric acid (GABA) and taurine (Tau) release decreased in the MVN following acute hypotension. In the unilateral labyrinthectomy group, the levels of Glu, GABA, and Tau were unchanged in the ipsilateral MVN to the lesion following acute hypotension. Furthermore, in the contralateral MVN to the lesion, Glu release increased, and GABA and Tau release decreased following acute hypotension. These results suggest that SNP-induced acute hypotension can influence the activity of neurons in the MVN through afferent signals from peripheral vestibular receptors, and that certain amino acid transmitters in the MVN are involved in this process.

Dynamic cerebral autoregulation during and after handgrip exercise in humans

The purpose of the present study was to examine the effect of static exercise on dynamic cerebral autoregulation (CA). In nine healthy subjects at rest before, during, and after static handgrip exercise at 30% maximum voluntary contraction, the response to an acute drop in mean arterial blood pressure and middle cerebral artery mean blood velocity was examined. Acute hypotension was induced nonpharmacologically via rapid release of bilateral thigh occlusion cuffs. Subjects were instructed to avoid executing a Valsalva maneuver during handgrip. To quantify dynamic CA, the rate of regulation (RoR) was calculated from the change in cerebral vascular conductance index during the transient fall in blood pressure. There was no significant difference in RoR between rest (mean+/-SE; 0.278+/-0.052/s), exercise (0.333+/-0.053/s), and recovery (0.305+/-0.059/s) conditions (P=0.747). In addition, there was no significant difference in the rate of absolute cerebral vasodilatory response to acute hypotension between three conditions (P=0.737). This finding indicates that static exercise and related elevations in blood pressure do not alter dynamic CA.

Baroreflex, Cerebral Perfusion, and Stroke: Integrative Physiology at Its Best

To the Editor: We wish to congratulate Sykora et al for their timely review on the potential role the arterial baroreflex plays in cerebrovascular disease outcomes.1 Although it may seem intuitive that both arterial baroreflex function and cerebral blood flow (CBF) regulation are important modulators of stroke outcome, clear and consistent evidence implicating the arterial baroreflex as an independent clinical predictor of stroke-related mortality is only emerging. The authors proffer several plausible hypotheses linking baroreflex dysfunction to the etiology of acute stroke and related clinical outcomes. Among them, the proposed “cross-linked” impairment of cerebrovascular autoregulation (CA) and altered autonomic drive as part of an underlying regulatory continuum in the context of stroke require further discussion. …

Prediction of Intradialytic Hypotension Using Photoplethysmography

Intradialytic hypotension is the most common acute complication during conventional hemodialysis treatment. Prediction of such events is highly desirable in clinical routine for prevention. This paper presents a novel prediction method of acute symptomatic hypotension in which the photoplethysmographic signal is analyzed with respect to changes in amplitude, reflecting vasoconstriction, and cardiac output. The method is based on a statistical model in which the noise is assumed to have Laplacian amplitude distribution. The performance is evaluated on 11 hypotension-prone patients who underwent hemodialysis treatment, resulting in seven events with acute symptomatic hypotension and 17 without. The photoplethysmographic signal was continuously acquired during treatment as was information on blood pressure and oxygen saturation. Using leave-one-out cross validation, the proposed method predicted six out of seven hypotensive events, while producing 1 false prediction out of 17 possible. The performance was achieved when the prediction threshold was chosen to be in the range 57%-65% of the photoplethysmographic envelope at treatment onset.

Acute multiple organ failure with imidacloprid and alcohol ingestion

Imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] belongs to a relatively new class of insecticidal chemistry, the chloronicotinyl neonicotinoid compounds. Animal studies indicate relatively low toxicity to mammals due to nicotinic receptor resistance. Human poisoning is usually mild, and reports are quite limited. Here, we report a case of ingestion of alcohol with an insecticide containing imidacloprid. Clinical manifestation included mild disorientation, followed by bradycardia, ventricular arrhythmia, and cardiopulmonary arrest. Acute multiple organ failure, including oliguric kidney injury, acute lung injury, hypotension, and metabolic acidosis developed within hours of ingestion. Renal replacement therapy, including intermittent hemodialysis and continuous venovenous hemodialysis, quickly corrected the metabolic acidosis with better blood pressure. Despite original belief that imidacloprid has low mammalian toxicity, there is increasing evidence that imidacloprid may cause heart, kidney, and other organ damages and even death besides gastrointestinal irritation and neurological symptoms. The role of aldehyde oxidase, imidacloprid metabolites, and ethanol alcohol consumption in the pathogenesis of imidacloprid toxicity needs further study.

Influence of baroreflex-mediated tachycardia on the regulation of dynamic cerebral perfusion during acute hypotension in humans

The effect of acute arterial baroreflex dysfunction on cerebral autoregulation (CA) in otherwise healthy humans is unknown. We identified dynamic CA with and without arterial baroreflex-mediated tachycardia and consequent changes in cardiac output during acute hypotension whilst continuously monitoring changes in middle cerebral artery mean blood velocity (MCA V(mean)). Acute hypotension was induced in nine healthy subjects (mean +/- s.d.; 26 +/- 3 years) by releasing bilateral thigh cuffs after 6 min of supra-systolic resting ischaemia. Hypotension was induced before and after sympathetic blockade (beta-1 receptors), and combined sympathetic-cholinergic blockade. That sequential bolus injections of sodium nitroprusside (50 microg), followed 60 s later by phenylephrine hydrochloride (50 microg), elicited < 5 beats min(-1) change in heart rate was verified to confirm that full cardiac autonomic blockade was achieved. Thigh cuff release elicited a transient drop in mean arterial pressure and resultant tachycardia. This tachycardic response was diminished in full cardiac blockade (vs. control, P = 0.029; vs. beta-1 adrenergic blockade, P = 0.031). Dynamic CA was also attenuated in the full blockade condition compared to both control (P = 0.028) and beta-1 adrenergic blockade conditions (P = 0.015), and was related with the attenuated tachycardia response (P = 0.015). These data indicate an important role of the cardiac baroreflex in dynamic CA.

Effects of chronic sympatho‐inhibition on reflex control of renal blood flow and plasma renin activity in renovascular hypertension

We determined if chronic sympatho-inhibition with rilmenidine has functional significance for the kidney by altering responses of renal blood flow (RBF) and plasma renin activity (PRA) to stress and acute hypotension in rabbits with renovascular hypertension. RBF to each kidney and renal sympathetic nerve activity (RSNA) to the left kidney were measured in rabbits in which a renal artery clip induced hypertension (2K1C) and in sham-operated rabbits. After 2 weeks, a subcutaneous minipump was implanted to deliver rilmenidine (2.5 mg.kg(-1).day(-1)) to 2K1C rabbits for 3 weeks. After 5 weeks of renal artery stenosis, mean arterial pressure (MAP) was 23% higher and PRA 3-fold greater than in sham-operated rabbits. Blood flow and renal vascular conductance in the stenosed kidney were lower (-75% and -80%) compared with sham, and higher in the non-clipped kidney (68% and 39%). Responses of RBF and PRA to hypotension were similar in 2K1C and sham rabbits. Airjet stress evoked a greater increase in MAP in 2K1C rabbits than sham controls. Chronic rilmenidine normalized MAP, reduced RSNA and PRA, and did not reduce RBF in the stenosed kidney. Responses of RBF (clipped and non-clipped kidney), RSNA and PRA to hypotension and airjet were little affected by rilmenidine. Our observations suggest that chronic sympatho-inhibition is an effective antihypertensive therapy in renovascular hypertension. It normalizes MAP and reduces basal PRA without compromising blood flow in the stenosed kidney or altering responses of MAP, haemodynamics and PRA to acute hypotension and stress.

Transfusion-Related Acute Lung Injury

Transfusion-related acute lung injury is a clinical syndrome that occurs within 6 hours of transfusion. It is the leading cause of transfusion-related mortality. It presents with shortness of breath, acute pulmonary edema, fever, hypotension, or hypertension followed by hypotension. Treatment consists of respiratory support and fluid administration to support blood pressure. A majority of cases are associated with antibodies to white blood cells in the blood donor. Blood centers in the United States are currently taking measures to reduce the risk of transfusion-related acute lung injury from blood components.

General anaesthesia for insertion of an automated implantable cardioverter defibrillator in a child with Brugada and autism

A 14-year-old autistic boy presented with acute gastroenteritis and hypotension. The electrocardiogram showed a ventricular fibrillation rhythm – he went into cardiorespiratory arrest and was immediately resuscitated. On investigation, the electrocardiogram showed a partial right bundle branch block with a “coved” pattern of ST elevation in leads v1–v3. A provisional diagnosis of Brugada syndrome was made, for which an automated implantable cardioverter defibrillator (AICD) implantation was advised. Although the automated implantable cardioverter defibrillator implantation is usually performed under sedation, because this was an autistic child, he needed general anaesthesia. We performed the procedure uneventfully under general anaesthesia and he was discharged after a short hospital stay.

Intrathoracic Caecal Perforation Presenting as Dyspnea

Introduction. Bochdalek hernia is a congenital defect of the diaphragm that is usually diagnosed in the neonatal period and incidentally in asymptomatic adults. Small bowel incarceration in a right-sided Bochdalek hernia is exceptional for an adult. Case Presentation. A 54-year-old woman was admitted for acute dyspnea, tachycardia, hypotension, and fever. Five days before, she had been experiencing an episode of diffuse abdominal pain. The admission chest X-ray was interpreted as right pleural effusion and pneumothorax with left mediastinal shift. Chest tube drainage was purulent. The thoracoabdominal CT examination suspected an intestinal incarceration through a right diaphragmatic defect. At laparotomy, a right-sided Bochdalek hernia was confirmed with a complete necrosis of the incarcerated caecum. Ileocaecal resection was performed, but the patient died from delayed septic complications. Conclusion. Intrathoracic perforation of the caecum is a rare occurrence; delayed diagnosis due to misleading initial symptoms may lead to severe complications and poor prognosis.

Superior vena cava syndrome: A rare complication of percutaneous nephrolithotripsy laser lithotripsy

Purpose:To describe a case of acute superior vena cava syndrome during percutaneous nephrolithotomy (PCNL), and to review the associated clinical features, management and complications.Clinical features:A 34-year-old man, diagnosed as right renal calculi and nodal tachycardia, was admitted to receive percutaneous nephroscope laser lithotripsy. Shortly after stone disintegration, he suffered acute hypoxic and hypotension, and showed cyanoderma of face and chest skin, ocular proptosis, jugular filling and ventricular fibrillation. Dopamine and adrenaline was intravenously injected. The patient was turned over to supine position and external cardiac massage and electric defibrillation were carried out immediately. The patient finally cardioverted. His vital signs subsequently became stable and cyanoderma faded. The patient was eventually discharged from the intensive care unit three days following the event.Conclusion:Severe complications such as cardiac arrest could happen during PCNL. Close monitoring the vital signs is essential for early finding and quick response to rescue.

Extrapontine myelinolysis as presenting manifestation of adrenal failure: A case report

Background Hyponatremia is a fairly common metabolic disorder. Hyponatremic myelinolysis is a relatively rare, life threatening complication with poorly understood pathophysiology, varied clinical manifestations and uncertain treatment. This case report highlights the range of clinical and imaging phenomena associated with hyponatremic myelinolysis. Methods Case report. Result A middle aged lady presented with an acute delirious state, hypotension and severe hyponatremia on a background of skin hyper-pigmentation and weight loss. Her clinical course evolved to an akinetic-rigid state and later to parkinsonism. Extensive investigations for recognizing a primary neurologic disorder, including brain MRI and CSF analysis were normal, though she had disseminated miliary tuberculosis involving multiple organs. Brain MRI changes characteristic of extrapontine myelinolysis appeared two weeks after the onset of symptoms. The patient recovered completely over several weeks. Conclusion This case of hyponatremic extrapontine myelinolysis occurred as the presenting manifestation of adrenal failure secondary to disseminated tuberculosis. Extraponine myelinolysis is difficult to diagnose in the context of delayed brain MRI changes and can have a favorable outcome with modern management.

Endovascular Treatment of Ruptured Abdominal Aortic Aneurysm with Aortocaval Fistula

Aortocaval fistula (ACF) is a rare complication of abdominal aortic aneurysm (AAA). We report the endovascular repair of an AAA rupture into the inferior vena cava. A 78-year-old woman was admitted to our hospital for acute hypotension. She presented with a pulsatile abdominal mass and became rapidly anuric. Abdominal computed tomography (CT) showed an AAA rupture into the inferior vena cava. The features of the AAA made it suitable for endovascular repair. To prevent pulmonary embolism caused by the presence of sac thrombosis near the vena cava lumen, a temporary vena cava filter was deployed before the procedure. A bifurcated stent-graft was placed with the patient under local anaesthesia, and the AAA was successfully treated. A transient type II endoleak was detected on CT 3 days after endograft placement. At routine follow-up 6 and 12 months after the procedure, the patient was in good clinical condition, and the type II endoleak had sealed completely. Endovascular treatment offers an attractive therapeutic alternative to open repair in case of ACF; however, only small numbers of patients have been treated, and long-term follow-up interval is lacking.

The Association Between Emergency Department Crowding and Adverse Cardiovascular Outcomes in Patients with Chest Pain

While emergency department (ED) crowding is a worldwide problem, few studies have demonstrated associations between crowding and outcomes. The authors examined whether ED crowding was associated with adverse cardiovascular outcomes in patients with chest pain syndromes (chest pain or related complaints of possible cardiac origin). A retrospective analysis was performed for patients >or=30 years of age with chest pain syndrome admitted to a tertiary care academic hospital from 1999 through 2006. The authors compared rates of inpatient adverse outcomes from ED triage to hospital discharge, defined as delayed acute myocardial infarction (AMI), heart failure, hypotension, dysrhythmias, and cardiac arrest, which occurred after ED arrival using five separate crowding measures. Among 4,574 patients, 251 (4%) patients developed adverse outcomes after ED arrival; 803 (18%) had documented acute coronary syndrome (ACS), and of those, 273 (34%) had AMI. Compared to less crowded times, ACS patients experienced more adverse outcomes at the highest waiting room census (odds ratio [OR] = 3.7, 95% confidence interval [CI] = 1.3 to 11.0) and patient-hours (OR = 5.2, 95% CI = 2.0 to 13.6) and trended toward more adverse outcomes during time of high ED occupancy (OR = 3.1, 95% CI = 1.0 to 9.3). Adverse outcomes were not significantly more frequent during times with the highest number of admitted patients (OR = 1.6, 95% CI = 0.6 to 4.1) or the highest trailing mean length of stay (LOS) for admitted patients transferred to inpatient beds within 6 hours (OR = 1.5, 95% CI = 0.5 to 4.0). Patients with non-ACS chest pain experienced more adverse outcomes during the highest waiting room census (OR = 3.5, 95% CI = 1.4 to 8.4) and patient-hours (OR = 4.3, 95% CI = 2.6 to 7.3), but not occupancy (OR = 1.8, 95% CI = 0.9 to 3.3), number of admitted patients (OR = 0.6, 95% CI 0.4 to 1.1), or trailing LOS for admitted patients (OR = 1.2, 95% CI = 0.6 to 2.0). There was an association between some measures of ED crowding and a higher risk of adverse cardiovascular outcomes in patients with both ACS-related and non-ACS-related chest pain syndrome.

A fast-growing obstructive left atrial intramural hematoma causing acute prolonged chest pain

A 74-year-old woman was at the emergency department for acute chest pain, dyspnea and severe transient hypotension. History was arterial hypertension and external electrical cardioversion (EEC) for persistent atrial fibrillation (AF) 8 days before admission. At that time echocardiography was normal. The patient underwent coronary angiography with no evidence of significant coronary arteries disease. At echocardiography a large multi-loculated mass occupying most of the left atrial space and obstructing left ventricular inflow was evident. There was mild pericardial effusion. The patient was operated and a large thrombus totally encompassed in the left atrial wall was removed. Initial tearing into the pericardial space was revealed. Post-surgical follow-up was uneventful and at 3-6 months normalization of the atrial cavity with blending of atrial endocardium and epicardium was demonstrated. No apparent etiological factor was found. We have provided evidence of the possible rapid formation of a large intramural atrial hematoma. Spontaneous atrial wall dissection should be considered in the differential diagnosis of chest pain.

Have a safe night: intimate protection against cerebral hyperperfusion during REM sleep

studies using a variety of methods (transcranial Doppler ultrasonography,133Xe inhalation, and single-photon emission computerized tomography) have shown a reduction (∼10–20%) in cerebral blood flow (CBF) during non-rapid-eye-movement (NREM) sleep and an increase (∼20–35%) during rapid-eye-