scholarly journals Activation of spinal opioid receptors contributes to hypotension after hemorrhage in conscious rats

1999 ◽  
Vol 276 (5) ◽  
pp. H1552-H1558 ◽  
Author(s):  
Kooi K. Ang ◽  
Robert J. McRitchie ◽  
Jane B. Minson ◽  
Ida J. Llewellyn-Smith ◽  
Paul M. Pilowsky ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Opioid Receptors ◽  
High Dose ◽  
Binding Affinities ◽  
Opioid Antagonists ◽  
Severe Hemorrhage ◽  
Effective Doses ◽  
Spinal Opioid

Opioid receptors are activated during severe hemorrhage, resulting in sympathoinhibition and a profound fall in blood pressure. This study examined the location and subtypes of opioid receptors that might contribute to hypotension after hemorrhage. Intrathecal naloxone methiodide (100 nmol) abolished the fall in blood pressure after hemorrhage (1.5% of body wt; mean arterial pressure 122 ± 8 mmHg after naloxone methiodide vs. 46 ± 5 mmHg in controls, P < 0.001). Intracisternal naloxone methiodide was less effective than intrathecal naloxone methiodide, whereas intravenous naloxone methiodide, which does not cross the blood-brain barrier, did not alter the fall in blood pressure after hemorrhage. These results demonstrate that spinal opioid receptors contribute to hypotension after hemorrhage but do not exclude supraspinal effects. In separate experiments, the subtype-specific opioid antagonists ICI-174864 (δ-antagonist), norbinaltorphimine (nor-BNI; κ-antagonist), and H-d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr-NH2(CTOP; μ-antagonist) were each administered intrathecally to determine the minimum dose that would attenuate hypotension during severe hemorrhage. These antagonists were effective at similar doses (3 nmol for CTOP, 6 nmol for ICI-174864, and 10 nmol for nor-BNI), although the binding affinities of these three different agents for their target receptors varied >1600-fold. Comparisons of the minimum effective doses of these antagonists in relation to their binding affinities provides strong evidence for the participation of δ-receptors in mediating hypotension after hemorrhage. In contrast, the dose at which nor-BNI was effective suggests an effect at δ-receptors but not κ-receptors. The efficacy of CTOP, albeit at a high dose, also suggests an effect at μ-receptors.

CHARACTERISTICS OF 24-HOUR BLOOD PRESSURE INDICATORS IN PATIENTS WITH HYPERTENSION AND CHRONIC OBSTRUCTIVE PULMONARY DISEASE

2020 ◽  
pp. 31-41
Author(s):  
M.A. Bubnova ◽  
O.N. Kryuchkova
Keyword(s):  
Blood Pressure ◽  
Chronic Obstructive Pulmonary Disease ◽  
Mean Arterial Pressure ◽  
High Risk ◽  
Arterial Pressure ◽  
Pulmonary Disease ◽  
Comparison Group ◽  
Cardiovascular Complications ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease

Patients with hypertension (HT) and chronic obstructive pulmonary disease (COPD) have a high risk of cardiovascular complications. Up to now, there is no optimal strategy for combined antihypertensive therapy. Still, the data of 24-hour blood pressure monitoring (BPM) are important while choosing treatment tactics. The aim of the paper is to study the features of indicators in patients with arterial hypertension (AH) and COPD. Materials and methods. 130 patients with HT were included in the study. The main group (n=90) included comorbid patients with HT and COPD, their average age was 61.30±1.01; the comparison group (n=40) consisted of patients with HT, their average age was 59.10±1.53. All patients underwent 24-hour BPM. Results. Comorbid patients revealed an increase in the mean 24-hour and night systolic and mean arterial pressure values as well as a significant increase in the load index of systolic, diastolic and mean arterial pressure. Also, comorbid patients demonstrated higher blood pressure in contrast to the patients of the comparison group. They had increased systolic, diastolic and mean blood pressure variability and a quicker rate of morning blood pressure rise. According to 24-hour blood pressure dynamics, pathological types of the 24-hour blood pressure curve, a higher frequency of the night-peaker profile dominated in patients with COPD if compared to patients with HT. Conclusion. The obtained data indicated a high risk of cardiovascular complications in comorbid patients, early target organ damage and an unfavorable disease prognosis. It means that both further study of hypertension clinical course in such patients and personalization of antihypertensive therapy are relevant. Keywords: hypertension, chronic obstructive pulmonary disease, 24-hour monitoring, blood pressure. Пациенты с артериальной гипертензией (АГ) и хронической обструктивной болезнью легких (ХОБЛ) имеют высокий риск возникновения кардиоваскулярных осложнений. В настоящее время в лечении не определена наиболее оптимальная стратегия комбинированной антигипертензивной терапии. Для выбора тактики терапии важную роль играют показатели суточного мониторирования артериального давления (СМАД). Цель. Изучить особенности показателей СМАД у пациентов с АГ на фоне ХОБЛ. Материалы и методы. В исследование включено 130 пациентов с АГ. В основную группу (n=90) вошли пациенты с АГ и ХОБЛ (средний возраст – 61,30±1,01 года), в группу сравнения (n=40) – больные только АГ (средний возраст – 59,10±1,53 года). Всем пациентам проведено СМАД. Результаты. У пациентов с коморбидностью выявлены следующие особенности суточных показателей артериального давления: увеличение значений среднесуточных и средненочных показателей систолического и среднего артериального давления; существенное повышение индекса нагрузки систолическим, диастолическим и средним артериальным давлением. Также эти больные отличались от пациентов группы сравнения более высокими значениями пульсового давления, имели повышенную вариабельность систолического, диастолического и среднего артериального давления, у них наблюдалось увеличение скорости утреннего подъема артериального давления. Суточная динамика артериального давления у пациентов с ХОБЛ характеризовалась преобладанием патологических типов суточной кривой АД, более высокой частотой профиля night-peaker по сравнению с больными только АГ. Выводы. Выявленные особенности свидетельствуют о высоком риске сердечно-сосудистых осложнений у пациентов с коморбидностью, раннем поражении органов-мишеней и неблагоприятном прогнозе заболевания, что требует дальнейшего изучения особенностей клинического течения АГ у таких больных и индивидуализации антигипертензивной терапии. Ключевые слова: артериальная гипертензия, хроническая обструктивная болезнь легких, суточное мониторирование, артериальное давление.

scholarly journals Plasticity in breathing and arterial blood pressure following acute intermittent hypercapnic hypoxia in infant rat pups with a partial loss of 5-HT neurons

2015 ◽  
Vol 309 (10) ◽  
pp. R1273-R1284 ◽  
Author(s):  
Jennifer Magnusson ◽  
Kevin J. Cummings
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Arterial Blood Pressure ◽  
Cardiovascular Responses ◽  
Partial Loss ◽  
Rat Pups ◽  
Arterial Blood ◽  
Hypercapnic Hypoxia ◽  
Long Term Facilitation

The role of serotonin (5-HT) neurons in cardiovascular responses to acute intermittent hypoxia (AIH) has not been studied in the neonatal period. We hypothesized that a partial loss of 5-HT neurons would reduce arterial blood pressure (BP) at rest, increase the fall in BP during hypoxia, and reduce the long-term facilitation of breathing (vLTF) and BP following AIH. We exposed 2-wk-old, 5,7-dihydroxytryptamine-treated and controls to AIH (10% O2; n = 13 control, 14 treated), acute intermittent hypercapnia (5% CO2; n = 12 and 11), or acute intermittent hypercapnic hypoxia (AIHH; 10% O2, 5% CO2; n = 15 and 17). We gave five 5-min challenges of AIH and acute intermittent hypercapnia, and twenty ∼20-s challenges of AIHH to mimic sleep apnea. Systolic BP (sBP), diastolic BP, mean arterial pressure, heart rate (HR), ventilation (V̇e), and metabolic rate (V̇o2) were continuously monitored. 5,7-Dihydroxytryptamine induced an ∼35% loss of 5-HT neurons from the medullary raphe. Compared with controls, pups deficient in 5-HT neurons had reduced resting sBP (∼6 mmHg), mean arterial pressure (∼5 mmHg), and HR (56 beats/min), and experienced a reduced drop in BP during hypoxia. AIHH induced vLTF in both groups, reflected in increased V̇e and V̇e/V̇o2, and decreased arterial Pco2. The sBP of pups deficient in 5-HT neurons, but not controls, was increased 1 h following AIHH. Our data suggest that a relatively small loss of 5-HT neurons compromises resting BP and HR, but has no influence on ventilatory plasticity induced by AIHH. AIHH may be useful for reversing cardiorespiratory defects related to partial 5-HT system dysfunction.

Hypotensive and Regional Haemodynamic Effects of Exercise, Fasted and after Food, in Human Sympathetic Denervation

1998 ◽  
Vol 94 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Sharmini Puvi-Rajasingham ◽  
Gareth D. P. Smith ◽  
Adeola Akinola ◽  
Christopher J. Mathias
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Superior Mesenteric Artery ◽  
Vascular Resistance ◽  
Mesenteric Artery ◽  
Autonomic Failure ◽  
Sympathetic Denervation ◽  
Stroke Distance

1. In human sympathetic denervation due to primary autonomic failure, food and exercise in combination may produce a cumulative blood pressure lowering effect due to simultaneous splanchnic and skeletal muscle dilatation unopposed by corrective cardiovascular reflexes. We studied 12 patients with autonomic failure during and after 9 min of supine exercise, when fasted and after a liquid meal. Standing blood pressure was also measured before and after exercise. 2. When fasted, blood pressure fell during exercise from 162 ± 7/92 ± 4 to 129 ± 9/70 ± 5 mmHg (mean arterial pressure by 22 ± 5%), P < 0.0005. After the meal, blood pressure fell from 159 ± 8/88 ± 6 to 129 ± 6/70 ± 4 mmHg (mean arterial pressure by 22 ± 3%), P < 0.0001, and further during exercise to 123 ± 6/61 ± 3 mmHg (mean arterial pressure by 9 ± 3%), P < 0.01. The stroke distance—heart rate product, an index of cardiac output, did not change after the meal. During exercise, changes in the stroke distance—heart rate product were greater when fasted. 3. Resting forearm and calf vascular resistance were higher when fasted. Calf vascular resistance fell further after exercise when fasted. Resting superior mesenteric artery vascular resistance was lower when fed; 0.19 ± 0.02 compared with 032 ± 0.06, P < 0.05. After exercise, superior mesenteric artery vascular resistance had risen by 82%, to 0.53 ± 0.12, P < 0.05 (fasted) and by 47%, to 0.29 ± 0.05, P < 0.05 (fed). 4. On standing, absolute levels of blood pressure were higher when fasted [83 ± 7/52 ± 7 compared with 71 ± 2/41 ± 3 (fed), each P < 0.05]. Subjects were more symptomatic on standing post-exercise when fed. 5. In human sympathetic denervation, exercise in the fed state lowered blood pressure further than when fasted and worsened symptoms of postural hypotension.

Increased vascular resistance in paralyzed legs after spinal cord injury is reversible by training

2002 ◽  
Vol 93 (6) ◽  
pp. 1966-1972 ◽  
Author(s):  
Maria T. E. Hopman ◽  
Jan T. Groothuis ◽  
Marcel Flendrie ◽  
Karin H. L. Gerrits ◽  
Sibrand Houtman
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Arterial Blood Flow ◽  
Arterial Blood ◽  
Cord Injury

The purpose of the present study was to determine the effect of a spinal cord injury (SCI) on resting vascular resistance in paralyzed legs in humans. To accomplish this goal, we measured blood pressure and resting flow above and below the lesion (by using venous occlusion plethysmography) in 11 patients with SCI and in 10 healthy controls (C). Relative vascular resistance was calculated as mean arterial pressure in millimeters of mercury divided by the arterial blood flow in milliliters per minute per 100 milliliters of tissue. Arterial blood flow in the sympathetically deprived and paralyzed legs of SCI was significantly lower than leg blood flow in C. Because mean arterial pressure showed no differences between both groups, leg vascular resistance in SCI was significantly higher than in C. Within the SCI group, arterial blood flow was significantly higher and vascular resistance significantly lower in the arms than in the legs. To distinguish between the effect of loss of central neural control vs. deconditioning, a group of nine SCI patients was trained for 6 wk and showed a 30% increase in leg blood flow with unchanged blood pressure levels, indicating a marked reduction in vascular resistance. In conclusion, vascular resistance is increased in the paralyzed legs of individuals with SCI and is reversible by training.

scholarly journals EFFECT OF ORAL MOXONIDINE IN THE ATTENUATION OF THE HAEMODYNAMIC RESPONSES SEEN DURING LAPAROSCOPIC SURGERIES

2017 ◽  
Vol 10 (3) ◽  
pp. 409
Author(s):  
Sidharth Sraban Routray ◽  
Ramakanta Mohanty
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Placebo Group ◽  
Stress Response ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Significant Rise ◽  
Hemodynamic Stability ◽  
Blinded Study ◽  
Double Blinded

ABSTRACTObjective: During laparoscopic surgeries, pneumoperitoneum can lead to various pathophysiologic changes in the cardiovascular system resulting inhypertension and tachycardia. Search for ideal drug to prevent this hemodynamic response goes on. The aim of our study was to evaluate the effect oforally administered moxonidine in attenuating the hemodynamic responses that occur during the laparoscopic surgeries.Methods: A total of 50 adult acetylsalicylic acid I and II patients scheduled for elective laparoscopic surgeries were selected for this prospectiverandomized double-blinded study. They were randomly allocated into two groups: moxonidine group (M) and placebo group (P). M group receivedoral moxonidine 0.3 mg at 8 pm on the day before surgery and at 8 am on the day of surgery. P group received a placebo at the same timing as that ofthe M group.Results: Following pneumoperitoneum rise in systolic blood pressure (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and heart rate (HR)was higher in P group in comparison to M group which was statistically significant.Conclusion: Significant rise in HR, SBP, DBP, and mean BP was noted in the P group in comparison to moxonidine group. Moxonidine provided betterperioperative hemodynamic stability in patients undergoing laparoscopic surgeries.Keywords: Moxonidine, Stress response, Laparoscopic.

Direct Cerebral Vasodilatory Effects of Sevoflurane and Isoflurane 

1999 ◽  
Vol 91 (3) ◽  
pp. 677-677 ◽  
Author(s):  
Basil F. Matta ◽  
Karen J. Heath ◽  
Kate Tipping ◽  
Andrew C. Summors
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Middle Cerebral Artery ◽  
Flow Velocity ◽  
Cerebral Artery ◽  
Blood Flow Velocity ◽  
End Tidal

Background The effect of volatile anesthetics on cerebral blood flow depends on the balance between the indirect vasoconstrictive action secondary to flow-metabolism coupling and the agent's intrinsic vasodilatory action. This study compared the direct cerebral vasodilatory actions of 0.5 and 1.5 minimum alveolar concentration (MAC) sevoflurane and isoflurane during an propofol-induced isoelectric electroencephalogram. Methods Twenty patients aged 20-62 yr with American Society of Anesthesiologists physical status I or II requiring general anesthesia for routine spinal surgery were recruited. In addition to routine monitoring, a transcranial Doppler ultrasound was used to measure blood flow velocity in the middle cerebral artery, and an electroencephalograph to measure brain electrical activity. Anesthesia was induced with propofol 2.5 mg/kg, fentanyl 2 micro/g/kg, and atracurium 0.5 mg/kg, and a propofol infusion was used to achieve electroencephalographic isoelectricity. End-tidal carbon dioxide, blood pressure, and temperature were maintained constant throughout the study period. Cerebral blood flow velocity, mean blood pressure, and heart rate were recorded after 20 min of isoelectric encephalogram. Patients were then assigned to receive either age-adjusted 0.5 MAC (0.8-1%) or 1.5 MAC (2.4-3%) end-tidal sevoflurane; or age-adjusted 0.5 MAC (0.5-0.7%) or 1.5 MAC (1.5-2%) end-tidal isoflurane. After 15 min of unchanged end-tidal concentration, the variables were measured again. The concentration of the inhalational agent was increased or decreased as appropriate, and all measurements were repeated again. All measurements were performed before the start of surgery. An infusion of 0.01% phenylephrine was used as necessary to maintain mean arterial pressure at baseline levels. Results Although both agents increased blood flow velocity in the middle cerebral artery at 0.5 and 1.5 MAC, this increase was significantly less during sevoflurane anesthesia (4+/-3 and 17+/-3% at 0.5 and 1.5 MAC sevoflurane; 19+/-3 and 72+/-9% at 0.5 and 1.5 MAC isoflurane [mean +/- SD]; P&lt;0.05). All patients required phenylephrine (100-300 microg) to maintain mean arterial pressure within 20% of baseline during 1.5 MAC anesthesia. Conclusions In common with other volatile anesthetic agents, sevoflurane has an intrinsic dose-dependent cerebral vasodilatory effect. However, this effect is less than that of isoflurane.

Increases in intramuscular pressure raise arterial blood pressure during dynamic exercise

2001 ◽  
Vol 91 (5) ◽  
pp. 2351-2358 ◽  
Author(s):  
K. M. Gallagher ◽  
P. J. Fadel ◽  
S. A. Smith ◽  
K. H. Norton ◽  
R. G. Querry ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Arterial Blood Pressure ◽  
Dynamic Exercise ◽  
Positive Pressure ◽  
Intramuscular Pressure ◽  
Arterial Blood ◽  
Exercise In Humans ◽  
Cuff Occlusion

This investigation was designed to determine the role of intramuscular pressure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixteen subjects performed incremental (20 W/min) cycle exercise to fatigue under four conditions: control, exercise with thigh cuff occlusion of 90 Torr (Cuff occlusion), exercise with lower body positive pressure (LBPP) of 45 Torr, and a combination of thigh cuff occlusion and LBPP (combination). Indexes of central command (heart rate, oxygen uptake, ratings of perceived exertion, and electromyographic activity), cardiac output, stroke volume, and total peripheral resistance were not significantly different between the four conditions. Mechanical stimulation during LBPP and combination conditions resulted in significant elevations in intramuscular pressure and mean arterial pressure from control at rest and throughout the incremental exercise protocol ( P < 0.05). Conversely, there existed no significant changes in mean arterial pressure when the metaboreflex was stimulated by cuff occlusion. These findings suggest that under normal conditions the mechanoreflex is tonically active and is the primary mediator of exercise pressor reflex-induced alterations in arterial blood pressure during submaximal dynamic exercise in humans.

scholarly journals Perbedaan Respon Hemodinamik dengan Penambahan Blok Scalp Levobupivakain pada Operasi Kraniotomi

2020 ◽  
Vol 9 (1) ◽  
pp. 8-15
Author(s):  
Arya Justisia Sani ◽  
Ardhana Tri Arianto ◽  
Muhammad Husni Thamrin
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Hemodynamic Response ◽  
Anesthesia Induction ◽  
Group I ◽  
Significant Difference ◽  
Scalp Block ◽  
One Way Anova

Latar Belakang dan Tujuan: Peningkatan respon hemodinamik yang disebabkan oleh nyeri dapat menyebabkan peningkatan aliran darah otak dan tekanan intrakranial. Blok scalp pada kraniotomi menumpulkan respon hemodinamik karena rangsangan nyeri serta mengurangi penambahan analgesi lain. Penelitian ini bertujuan untuk mengetahui efektifitas blok scalp sebagai analgetik pada kraniotomi.Subjek dan Metode: Penelitian ini menggunakan uji klinik acak tersamar ganda pada 36 pasien dengan status fisik ASA 1–3 dilakukan operasi kraniotomi eksisi dan memenuhi kriteria inklusi. Sampel dibagi menjadi kelompok I (dengan blok scalp) dan kelompok II (tanpa blok scalp). Blok dilakukan sesaat setelah induksi anestesi. Digunakan levobupivakain 0,375% sebanyak 3 ml tiap insersi, pada masing-masing saraf. Tekanan darah, tekanan arteri rata-rata, detak jantung sebelum intubasi dan setelah intubasi, pemasangan pin, insisi kulit dan insisi duramater serta total kebutuhan fentanyl tambahan dicatat. Data yang diperoleh dianalisis dengan program komputer SPSS versi 17 lalu diuji menggunakan uji Kruskal-Wallis atau One-way ANOVA. Batas kemaknaan yang diambil adalah p < 0,05.Hasil: Selama kraniotomi, detak jantung, tekanan darah, tekanan arteri rata-rata secara signifikan lebih tinggi pada pasien tanpa blok scalp terutama pada saat pemasangan pin. Hasil uji statistik menunjukkan perbedaan signifikan, penambahan fentanyl pada pasien dengan blok scalp lebih sedikit dibandingkan tanpa blok scalp, p=0,000 (p<0,05).Simpulan: Blok scalp levobupivakain efektif dalam menurunkan respon hemodinamik terutama pada saat pemasangan pin. Pasien kraniotomi dengan blok scalp membutuhkan penambahan fentanyl lebih sedikit. Differences on Hemodynamic Response with Levobupivacaine Scalp Block in Craniotomy SurgeryAbstractBackground and Objective: Increased hemodynamic response caused by pain can lead to increased cerebral blood flow and intracranial pressure. Scalp block in craniotomy blunts hemodynamic response due to pain and reduce other analgesics addition. This study aims to determine effectiveness of scalp blocks as analgesic in craniotomy.Subject and Method: This study used a double-blind randomized clinical trial in 36 patients with physical status ASA 1-3 who underwent craniotomy and met inclusion criteria. Samples were divided into group I (with scalp block) and group II (without scalp block). Scalp Block was performed right after anesthesia induction. Using levobupivacaine 0.375% 3 ml for each insertion. Blood pressure, mean arterial pressure, heart rate before and after intubation, during pin placement, skin incision and duramater incision and total need for additional fentanyl were recorded. SPSS version 17 was used and data were analysed using Kruskal-Wallis or One-way ANOVA. Statistical significance was accepted at p < 0.05.Result: During craniotomy, heart rate, blood pressure, mean arterial pressure were significantly higher in patients without scalp block especially during pin placement. Statistical test showed significant difference, additional fentanyl in patients with scalp blocks was lesser, p = 0.000 (p <0.05). Conclusion: Levobupivacaine scalp block was effective to blunt hemodynamic response especially during pin placement. Scalp block also decreased additional fentanyl in craniotomy.

Abstract P154: Ultrasound Imaging for Serial Measurements of Venous Diameters in Rats

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Teresa Krieger-Burke ◽  
Bridget M Seitz ◽  
Gregory D Fink ◽  
Stephanie W Watts
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Real Time ◽  
Ultrasound Imaging ◽  
Imaging System ◽  
Sprague Dawley ◽  
Reliable Technique ◽  
Venous Capacitance ◽  
Anesthetized Rats

The purpose of our study was to investigate serial ultrasound imaging in rats as a means to quantify the diameters of splanchnic veins in real time and the effect of drugs on venous capacitance. A 21 MHz probe ( Vevo 2100 imaging system,Visual Sonics Inc.) was used to collect images containing the portal vein (PV) and the superior mesenteric vein (SMV) in anesthetized male Sprague-Dawley rats maintained at 37°C. Stable landmarks were established and we were able to repeatedly locate specific cross-sections of PV and SMV. When controlled for respiratory and cardiac cycles during measurements, respective diameters of these vessels remained within 0.75±0.15% and 0.2±0.10% of baseline (PV: 2.02±0.15 mm; SMV: 1.67±0.05 mm) when located and measured every 5 minutes over 45 minutes (n=3 rats). PV and SMV remained within 1.0±0.6% and 0.38±0.9% from baseline, respectively, when measured on separate days over 10 weeks in a preliminary study using 2 rats. The consistency of raw vessel measurements allowed these vessels to serve as their own control during subchronic pharmacologic interventions. In a second study, the vasodilator sodium nitroprusside (2 mg/kg, i.v. bolus) was administered to anesthetized rats (n=3) following collection of baseline vessel measurements. PV and SMV diameters increased 37.23±2.4% and 29.77±8.8% from baseline by 30 minutes post drug administration while mean arterial pressure decreased 10.32±1.7 mmHg. Conversely, the administration of the venoconstrictor sarafotoxin (S6C) (5 ng/kg, i.v. bolus) to other anesthetized rats (n=3) decreased PV and SMV diameters 22.10±2.4% and 9.44±1.6% from baseline within 5 minutes, associated with an increase in mean arterial pressure of 12.85±3.2 mmHg. Together these results support serial ultrasound imaging as a reliable technique to accurately measure acute and subchronic changes in the diameter of splanchnic veins concurrent with blood pressure changes in intact rats. The ability to follow rat abdominal vein diameters in real time will assist in determining the role of the venous circulation in blood pressure regulation.

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