Distal Blood Pressure Research Articles

Effects of physical and mental task demands on cervical and upper limb muscle activity and physiological responses during computer tasks and recovery periods

The present study examined the effects of physical and mental workload during computer tasks on muscle activity and physiological measures. Activity in cervical postural muscles and distal forearm muscles, heart rate and blood pressure were compared among three tasks and rest periods of 15min each in an experimental study design. Fourteen healthy pain-free adults participated (7 males, mean age=23.2±3.0years) and the tasks were: (1) copy-typing ("typing"), (2) typing at progressively faster speed ("pacing"), (3) mental arithmetic plus fast typing ("subtraction"). Typing task was performed first, followed by the other two tasks in a random order. Median muscle activity (50th percentile) was examined in 5-min intervals during each task and each rest period, and statistically significant differences in the "time" factor (within task) and time×task factors was found in bilateral cervical erector spinae and upper trapezius muscles. In contrast, distal forearm muscle activity did not show any significant differences among three tasks. All muscles showed reduced activity to about the baseline level within first 5min of the rest periods. Heart rate and blood pressure showed significant differences during tasks compared to baseline, and diastolic pressure was significantly higher in the subtraction than pacing task. The results suggest that cervical postural muscles had higher reactivity than forearm muscles to high mental workload tasks, and cervical muscles were also more reactive to tasks with high physical demand compared to high mental workload. Heart rate and blood pressure seemed to respond similarly to high physical and mental workloads.

Blood pressure measurement in the artery proximal and distal to an intra-arterial embolus during thrombolytic therapy

Background and aimWhen a cerebral embolism occurs, pressure gradients in the arteries between sites proximal and distal to the embolus exert hydromechanical forces that push the embolus distally, and potentially...

Hemodynamic Effects of Closure of Residual Arteriovenous Fistulae during in Situ Graft Procedures

The objective was to study the intraoperative hemodynamic effects of closure of residual arteriovenous fistulae during in situ saphenous vein graft procedures. Data on 60 residual arteriovenous fistulae in nine patients (five men) with a median age of 74 years (range 64-83 years) with critical lower limb ischemia were obtained. Direct measurements of proximal and distal blood pressures in the graft were taken and simultaneous determinations of volume blood flow proximally and distally in the graft with ultrasound transit time technique before and after closure of residual fistulae were made. Closure of a fistula with blood flow around or below 100 mL/min did not increase distal outflow, whereas closure of fistulae with higher blood flow resulted in unpredictable changes in distal outflow. Only fistulae with a blood flow above approximately 100 mL/min may be of hemodynamic significance.

Index of Suspicion in the Nursery

A male infant is born at term to a 34-year-old gravida 1 Middle Eastern woman. Prenatal laboratory evaluation documented blood type O-positive, antibody screen-negative, rapid plasma reagin-nonreactive, rubella-immune, human immunodeficiency virus-negative, and group B beta-hemolytic Streptococcus -negative. The woman had undergone in vitro fertilization for the pregnancy. The woman presented in labor with the fetus in breech presentation. During delivery by cesarean section, the infant was noted to be footling breech, and extraction was difficult. Resuscitation was minimal, with warming and drying only. Apgar scores were 9 at 1 and 5 minutes. Physical examination in the delivery room revealed no unusual findings, and the baby was sent to the well baby nursery. The birthweight was 4,062 g. Six hours after his birth, the nurse notes that the infant has bilateral swollen thighs, with the left significantly more swollen than the right. On further evaluation, the infant's right thigh is minimally swollen around an intramuscular injection site without any color change. However, his left thigh has circumferential swelling with mild ecchymosis, taut overlying skin, and edema extending distally past the knee to the lower leg. His temperature is 36.9°C, heart rate is 130 beats/min, respiratory rate is 56 breaths/min, and blood pressure is 73/42 mm Hg. Physical examination reveals a comfortably sleeping infant, who has …

Effect of different programs of hyperbaric oxygen preconditioning on spinal cord ischemia- reperfusion injury in rabbits

Objective To investigate the effect of different programs of preconditioning with hyperbaric oxygen (HBO) on spinal cord ischemia-reperfusion injury (I/R) in rabbits. Methods Forty-five New Zealand rabbits aged 4-5 months weighing 2.0-2.5 kg were randomly divided into 5 groups: group S, sham operation ( n = 5);group IR, spinal cord I/R injury (n = 10);group H_(1～3) , the animals were pretreated with 100% O_2 at 2.5 ATA 1 h/d for 5 (group H_1 ), 10 (group H_2 ) , or 20 (group H_3 ) consecutive days respectively 24 h before spinal cord I/R. The animals were anesthetized with iv pentobarbital sodium 30 mg/kg. The artery in the ear and left femoral artery were cannulated for proximal and distal mean blood pressure monitoring. Spinal cord ischemia was produced by cross-clamping of abdominal aorta distal to renal artery for 20 min. Hind-limb motor function was assessed at 48 h after reperfusion according to the modified criteria established by Tarlov (0 = no spontaneous movement, 4= normal motor function) . The animals were then killed and the L_5 segment of the spinal cord was removed for detection of neuronal survival (by HE staining), apoptosis (by TUNEL) and degeneration (by Fluoro-Jade B staining). Results Preconditioning with 5 or 10 d of HBO improved the hind-limb motor function and preserved more normal neurons in the spinal cord after I/R injury. Both apoptotic and degenerative cell death were attenuated in H_1 and H_2 groups. There was no significant difference in hind-limb motor dysfunction and the number of normal neurons in the lumbar spinal cord between H_3 group and I/R group. Conclusion Preconditioning with 5 d or 10 d HBO induces tolerance against spinal cord I/R injury, whereas preconditioning with 20 d of HBO fails to protect the spinal cord from I/R injury. Key words: Hyperbaric oxygenation; Ischemic preconditioning; Reperfusion injury; Spinal cord

Do short-stretch bandages affect distal blood pressure in patients with mixed aetiology leg ulcers?

Compression is considered inappropriate for patients with mixed aetiology leg ulcers. However, digital blood pressure measurements suggest that short-stretch bandages do not increase the risk of peripheral ischaemia in these patients.

Results of treatment in 118 foot necroses in relation to ankle blood pressure and diabetes. A one-year retrospective study of 108 patients

The healing-rate in 118 necrotic lesions of the forefoot was investigated in 108 patients. The global healing frequency after 9 months amounted to 28%. A linear increase in healing was observed during this period. Later, no further healing occurred despite continuation of local treatment of the necrosis. The healing-rate was directly related to the distal (ankle) systolic blood pressure. Blood pressures under 50 mm Hg made healing impossible, whereas pressures above led to a healing-rate up to 37%. Diabetes mellitus had no influence on the healing-rate. Three guiding principles can be brought forward for the treatment of necrotic lesions of the forefoot: 1. When no healing is attained after 9 months, continuation of the local therapy is no longer worthwhile. 2. There is no likelihood of healing when the distal systolic blood pressure (ankle) is below 50 mm Hg. 3. Before commencing treatment the distal systolic blood pressure should be known. When this is low, measures to open vessels should be considered (operative, catheter technique, lysis) in order to raise the blood pressure above 50 mm Hg and thereby improve the healing prospects.

Reference data for distal blood pressure in healthy elderly and middle‐aged individuals measured with the strain gauge technique. Part II: Distal blood pressure after exercise

Objective. Distal blood pressure (DBP) determination after an exercise test is used on suspicion of arterial peripheral vascular disease (apvd). In our department. the average age of these patients is about 60 years. The usual reference values for pressures after exercise were based on data collected in the early 1970s from healthy individuals in the age range 21–26 years. Our aims were to collect new reference data for DBP at ankle level after exercise based on older populations, and to compare between reference data for different age groups to find out whether the normal values are dependent on age. Material and methods. DBP after exercise was measured using the strain‐gauge technique on individuals in two groups: group I comprising 25 healthy persons aged between 61 and 82 years, and group II 14 healthy persons aged between 45 and 58 years. Strict rules of inclusion were followed. Results. Normal values are dependent on age. The average differences (ankle DBPafter−ankle DBPbefore) immediately after walking were 25 mmHg, 12 mmHg and −8 mmHg in group I, group II and the old data, respectively. Comparison among groups showed significant differences (p⩽0.01). Conclusion. Normal values for elderly and middle‐aged persons are presented. Use of normal values based on young people may result in underestimation of DBP response and hence underestimation of the degree of possible apvd, especially in elderly individuals.

Reference data for distal blood pressure in healthy elderly and middle‐aged individuals measured with the strain gauge technique. Part I: Resting distal blood pressure

Objective. Most patients referred to our department for distal blood pressure (DBP) determination on suspicion of arterial peripheral vascular disease (apvd) are more than 60 years of age, whereas the only available reference data for resting pressure are based on data from healthy individuals aged between 43 and 57 years. Our aim was to investigate whether newly collected reference data for DBP measured using the strain‐gauge technique in healthy subjects older than 60 years and in others between 45 and 58 years were significantly different from the old reference data used in daily practice. Material and methods. Group I comprised 31 healthy persons aged between 61 and 87 years and group II 14 healthy middle‐aged hospital staff members aged between 45 and 58 years. Strict rules of inclusion were followed. Results. For group I, significantly greater gradients (DBPtoe – systolic arm blood pressure and DBPtoe – DBPankle) were found in the new reference data compared to the old. No significant difference between the mean values of the gradient (DBPankle – systolic arm blood pressure) was found between the old and new reference data, although the variation was significantly wider in the new reference data; the lower level of normality was therefore −15 mmHg compared to 0 mmHg in the old reference data. For group II, no significant differences between the gradients were found comparing the new and old reference data. Conclusion. These new data indicate that reference data gathered from middle‐aged subjects should be changed when DBP measurements are used in patients older than 60 years of age.

Distally Based Anterolateral Thigh Flap: An Anatomic and Clinical Study

The distally based anterolateral thigh flap has been used for coverage of soft-tissue defects of the knee and upper third of the leg. This flap is based on the septocutaneous or musculocutaneous perforators derived from the lateral circumflex femoral system. The purpose of this study was to examine the results of anatomical variations of the descending branch of the lateral circumflex femoral artery and the retrograde blood pressure of the descending branch of the lateral circumflex femoral artery so that the surgical technique for raising and transferring a distally based anterolateral thigh flap to the knee region could be improved. The authors have actually used this flap in three cases. In 11 thighs of six cadavers, the descending branch of the lateral circumflex femoral artery had a rather consistent connection with the lateral superior genicular artery or profunda femoral artery in the knee region. The pivot point, located at the distal portion of the vastus lateralis muscle, ranges from 3 to 10 cm above the knee. In their three cases, the maximal flap size was 7.0 x 16.0 cm and was harvested safely, without marginal necrosis. The mean pedicle length was 15.2 +/- 0.7 cm (range, 14.5 to 16 cm). The average proximal and distal retrograde blood pressure of the descending branch of the lateral circumflex femoral artery was also studied in another 11 patients, and the anterolateral thigh flap being used for reconstruction of head and neck defects showed 58.3 and 77.7 percent of proximal antegrade blood pressure, respectively. The advantages of this flap include a long pedicle length, a sufficient tissue supply, possible combination with fascia lata for tendon reconstruction, and favorable donor-site selection, without sacrifice of major vessels or muscles.

Repair of the descending thoracic aorta: impact of open distal anastomosis technique on spinal cord perfusion, neurological outcome and spinal cord histopathology☆

We investigated the impact of equilibrating distal aortic pressure with atmospheric pressure (open distal anastomosis) on spinal cord perfusion, neurological outcome and spinal cord histopathology in a rat model of descending thoracic aortic surgery. Proximal thoracic aortic occlusion was obtained in Sprague-Dawley rats by inflating the balloon of a 2F Fogarty catheter introduced through the left femoral artery. Rats were separated into three groups: sham-operation (n = 5) without balloon inflation, control (n = 15) with inflation of the balloon, and open distal (n = 15) with inflation of the balloon combined with incision of the right femoral artery to allow free drainage of distal aortic blood. Balloon inflation was maintained for 15 min. Rectal temperature, arterial blood gases and pH, distal arterial blood pressure (DABP) and lumbar spinal cord blood flow (SCBFl) were recorded throughout the procedure. Neurobehavioral status was assessed daily using a 0-5 scale and rats were sacrificed after 48 h of reperfusion and their spinal cord harvested for histopathology and immunohistochemistry for microtubule-associated protein-2 (MAP-2). DABP and SCBFl values were lower during thoracic aortic occlusion in the open distal group, compared to the control group (P < 0.001). Paraplegia and mortality rates were dramatically increased in the open distal group (87.7 and 46.6%, respectively) compared to the control group (0 and 6.6%, respectively, (P < 0.001 and 0.02). Severe metabolic acidosis and bowel infarct were also more frequent in the open distal group (P < 0.001). Sham-operated and control rats had virtually normal spinal cords, whereas rats in the open distal group had severe ischemic injury throughout gray matter. Equilibrating distal arterial pressure with atmospheric pressure during thoracic aortic occlusion decreased spinal cord blood flow, increased mortality and worsened spinal cord injury in rats. These results suggest that the open distal anastomosis technique should be used with caution in patients undergoing repair of the descending thoracic or thoracoabdominal aorta.

Visceral and Renal Tissue Oxygenation During Supraceliac Aortic Crossclamping and Left Heart Bypass with Selective Organ Perfusion

Introduction. Left-heart bypass (LHB) and selective organ perfusion (SOP) are used during thoracoabdominal aortic surgery to prevent ischemic damage to the kidneys and visceral organs after supraceliac aortic crossclamping. We studied the hypothesis, in a porcine model, that despite LHB and maximal SOP, visceral and renal ischemia still occured during surgery.Material and methods. Eleven pigs (54–70 kg) were coupled to a non-pulsatile LHB with inflow and outflow at the lower thoracic and distal infrarenal aorta, respectively. After supracoeliac and infrarenal aortic crossclamping, SOP was started using perfusion catheters. The proximal and distal mean aortic blood pressures were kept above 70 and 50 mmHg, respectively, while the mean blood pressure within the SOP system was above 60 mmHg. The visceral and renal tissue oxygenation was measured by intermittent blood gas analysis, from the portal and both renal veins. The jejunal mucosal oxygenation was measured by tonometric measurement of the luminal pCO2.Results. Measured median blood blood flow through the LHB and the SOP system were 800 and 1140 ml/min, respectively. Median blood flow prior to, and during LHB and SOP through the celiac artery, superior mesenteric artery, and left renal artery were 300 and 240, 762 and 295, and 235 and 235 ml/min, respectively. During 3 h of LHB and SOP no significant changes in the renal tissue oxygenation were noted compared with the physiological situation prior to supracoeliac aortic crossclamping and cannulation. However, in the visceral vascular bed median mixed venous oxygen saturation dropped from 79 to 63% (p<0.001), and median oxygen extraction ratio increased from 26 to 41% (p<0.001). Median tonometric measured intraluminal jejunal pCO2 increased from 9.9 to 12.15kPa (p>0.05). During 3 h of LHB and SOP no hemolysis was detected, as there was no rise in serum LDH.Conclusion. LHB and SOP preserves renal but not visceral tissue oxygenation during supraceliac aortic crossclamping and does not induce hemolysis.

No Influence of Melatonin on Cerebral Blood Flow in Humans

Melatonin has been attributed a role in a number of physiological processes. Changes in distal skin temperature and blood pressure after intake of melatonin suggest that melatonin induces peripheral vasodilation. The effect on the cerebral blood flow is still unknown. We examined the effect of a single pulse of melatonin on cerebral and peripheral blood flow, using the latter as a positive control. Ten male healthy volunteers (mean age, 22 +/- 3.2 yr) participated in a double-blind, randomized, placebo-controlled, cross-over study. On one occasion 10 microg melatonin were infused i.v., and on the other occasion saline was infused as the matching placebo. Cerebral blood flow was measured using phase contrast magnetic resonance imaging. Peripheral blood flow was determined from changes in the distal to proximal skin temperature gradient and finger pulse volume. Serum melatonin concentration increased from 12 +/- 5 pg/ml at baseline to 487 +/- 377 pg/ml at 5 min and 156 +/- 68 pg/ml at 10 min after melatonin administration. There was no significantly different time course for cerebral blood flow and cerebrovascular resistance. Compared with placebo, melatonin significantly increased peripheral blood flow, as measured by distal to proximal skin temperature gradient and finger pulse volume. These data demonstrate that melatonin does not have an acute regulatory effect on cerebral blood flow in humans.

Endoluminal Aortic Shunting for Distal Perfusion during Thoracic Aortal Cross-Clamping in a Pig Model

Purpose of the study: To investigate the haemodynamic properties of a direct endovascular aortic shunt to maintain distal aortic perfusion as an alternative of a distal shunt (left-left-,Gott shunt) in thoracic aortic aneurysm repair. Methods: A shunt was developed and tested in an in vitro model which should be capable of transporting a flow of 3–4 L/min with a decrease in blood pressure &lt; 20 mmHg. Thereupon the shunt was tested in an in vivo experiment in six pigs to assess the possibility of its use with normal distal blood pressure. The shunt was inserted in the thoracic aorta and stayed in place for 1.5 h. Parameters were measured at six time intervals to assess organ perfusion, -function, cardiac output, proximal- and distal blood pressure and aortic- and shunt flow. Principle findings: The mean blood flow through the shunt was 2.5 L/min. The difference of the mean blood pressure over the shunt was on average 14.20 mmHg. Parameters for coagulation disturbance and organ ischaemia were tested. The decrease in mean trombocyt count was 299–158 ( p &lt; 0.02). The venous lactate and the venous mesenteric lactate as parameters for intestinal ischemia did not increase significantly. No significant changes occurred in angiotensin II levels. Pulsatile flow was maintained but significantly suppressed (60%) distal from the shunt. The clamp time needed to insert the shunt and the venous mesenteric lactate, as well as the venous lactate, showed high correlation, r s = 0.9 ( p &lt; 0.05) and r s = 0.94 ( p &lt; 0.01). This also accounted for the 2nd clamp time, both r s = 0.95 ( p &lt; 0.05). Conclusion: The shunt is capable of transporting a blood flow of 2–4 L/min with an acceptable decrease in distal blood pressure. However, the time, needed to insert the shunt, was significantly associated with parameters of organ ischaemia.

Association between coronary lesion severity and distal microvascular resistance in patients with coronary artery disease.

Homogeneity of microvascular resistance in different perfusion areas of the same heart is generally assumed. We investigated the effect of the severity of an epicardial stenosis on microvascular resistance in 27 patients with coronary artery disease and stable angina. All patients had an angiographically normal coronary artery, an artery with an intermediate lesion, and an artery with a severe lesion; the latter was treated with angioplasty. In each patient, distal blood flow velocity and pressure were measured during baseline and maximal hyperemia (induced by intracoronary adenosine) using a Doppler and pressure guide wire, respectively. The ratio of mean distal pressure to average peak blood flow velocity was used as an index for the microvascular resistance (MRv). Within patients, the hyperemic MRv was higher in arteries with more severe stenosis (P = 0.021). After percutaneous transluminal coronary angioplasty (PTCA), the hyperemic MRv decreased (pre-PTCA, 2.6 vs. post-PTCA, 1.9 mmHg.cm(-1)s(-1), P < 0.01) toward the value of the reference artery (1.7 mmHg.cm(-1)s(-1); P = 0.67). We conclude that there is a positive association between coronary lesion severity and variability of distal microvascular resistance that normalizes after angioplasty. This study challenges the concept of uniform distribution of hyperemic MRv that is relevant for the interpretation of both noninvasive and invasive diagnostic tests.

Endoluminal aortic shunting for distal perfusion during thoracic aortal cross-clamping in a pig model

Purpose of the study: To investigate the haemodynamic properties of a direct endovascular aortic shunt to maintain distal aortic perfusion as an alternative of a distal shunt (left-left-, Gott shunt) in thoracic aortic aneurysm repair. Methods: A shunt was developed and tested in an in vitro model which should be capable of transporting a flow of 3–4 L/min with a decrease in blood pressure < 20 mmHg. Thereupon the shunt was tested in an in vivo experiment in six pigs to assess the possibility of its use with normal distal blood pressure. The shunt was inserted in the thoracic aorta and stayed in place for 1.5 h. Parameters were measured at six time intervals to assess organ perfusion, -function, cardiac output, proximal- and distal blood pressure and aortic- and shunt flow. Principle findings: The mean blood flow through the shunt was 2.5 L/min. The difference of the mean blood pressure over the shunt was on average 14.20 mmHg. Parameters for coagulation disturbance and organ ischaemia were tested. The decrease in mean trombocyt count was 299–158 ( p<0.02). The venous lactate and the venous mesenteric lactate as parameters for intestinal ischemia did not increase significantly. No significant changes occurred in angiotensin II levels. Pulsatile flow was maintained but significantly suppressed (60%) distal from the shunt. The clamp time needed to insert the shunt and the venous mesenteric lactate, as well as the venous lactate, showed high correlation, r s = 0.9 ( p<0.05) and r s = 0.94 ( p<0.01). This also accounted for the 2nd clamp time, both r s = 0.95 ( p<0.05). Conclusion: The shunt is capable of transporting a blood flow of 2–4 L/min with an acceptable decrease in distal blood pressure. However, the time, needed to insert the shunt, was significantly associated with parameters of organ ischaemia.

Effect of total knee arthroplasty on blood flow to the lower limb: A prospective clinical study and review of literature

Ischemic complications after total knee arthroplasty (TKA) are rare. There is a reported association with chronic lower extremity ischemia (CLEI), however. This prospective study examined changes in blood pressure in the lower limb during the early postoperative period. Arterial blood pressure was assessed before and after TKA by the ankle brachial pressure index (ABPI) using Doppler ultrasonography. Seven patients with CLEI (ABPI <0.9) and 33 patients with normal vascular status (ABPI >0.9) were studied. An ABPI of 0.65, correction of minor knee deformity, and a tourniquet time of 2 hours did not alter arterial blood pressure. TKA does not affect the distal arterial blood pressure in the lower limb in normal and CLEI-affected limbs in the immediate postoperative period. Copyright 2002, Elsevier Science (USA). All rights reserved.

Experimental rupture of atherosclerotic lesions increases distal vascular resistance: a limiting factor to the success of infarct angioplasty.

Rupture of atherosclerotic lesions, resulting in localized thrombi and marked falls in distal blood flow, is a pivotal event in unstable coronary syndromes. We tested the hypothesis that after lesion rupture, vasoconstrictor mechanisms are major contributors to a marked rise in distal microvascular resistance, which is responsible for much of the interruption in blood flow. Cholesterol-fed rabbits underwent endothelial denudation of their left iliac arteries to induce angiographically severe, fatty, American Heart Association type IV-like atherosclerotic lesions. After lesion disruption with a stiff wire, we measured distal blood flow and pressure, capillary patency in the distal vascular bed, and the response to the vasodilators adenosine, nitroprusside, and glyceryl trinitrate. Morphology of the lesions and of the associated thrombi was also examined to assess lumen restriction at the site of rupture. Disruption of atherosclerotic lesions reduced mean flow from 5.04+/-1.21 to 1.23+/-0.37 mL/min (P<0.005), and calculated distal vascular resistance rose rapidly, from 17.5+/-2.9 to 37.9+/-6.4 mm Hg. min/mL (P<0.005). Lesion rupture did not significantly affect capillary patency in the distal muscle vascular bed, and although nonocclusive thrombi were present at the site of nearly all ruptured lesions, embolized thrombi were rare in capillaries (<1%). The early rise in distal microvascular resistance could be normalized with intra-arterially administered adenosine or the NO donor nitroprusside, but not glyceryl trinitrate, an organonitrate possessing large muscular artery-selective vasodilator characteristics. Thus, rupture of atherosclerotic lesions induces rapid and marked increases in distal vascular resistance, which is the consequence of severe microvascular vasoconstriction. Therapeutic targeting of the microvasculature should improve reperfusion in acute coronary syndromes.

Renal effects of dopamine and ANP in high volume expanded rats

Both dopamine (DA) and atrial natriuretic peptide (ANP) have been postulated to exert similar effects on the kidney, participating in the regulation of body fluid and sodium homeostasis. In the present study, experiments were performed in anesthetized and isotonic sodium chloride volume expanded rats. After acute volume expansion at 15 % of body weight during 30 min, glomerular filtration rate, urine output, sodium excretion, fractional sodium excretion, proximal and distal sodium excretion and blood pressure were measured. In additional groups we administered ANP or haloperidol or the combination of both to volume expanded animals. Blockade of DA receptors with haloperidol, attenuated diuretic and natriuretic responses to volume load. Proximal sodium excretion was not modified by haloperidol in all experimental groups of rats. Reduction in distal tubular excretion was induced by haloperidol in saline infusion expanded rat but not in ANP treated expanded animals. In conclusion, when exaggerated volume expansion is provoked, both DA and ANP exert renal tubular events, but ANP have a major central role in the regulation of renal sodium handling.

Spinal cord ischemia. Development of a model in the mouse.

Spinal cord ischemia with resulting paraplegia is a devastating complication of thoracoabdominal aortic surgery. Experimental models of spinal cord ischemia have been developed in primate, dog, pig, rabbit, and rat with variable reproducibility, but none has been developed in mouse. Because genetically engineered mice have become important to examine the impact of specific genes in ischemic pathophysiology, we sought to develop a reproducible mouse model of spinal cord ischemia. C57BL/6NCrlBR mice were subjected to cross-clamping of the aortic arch, left subclavian artery, and internal mammary artery for 9 minutes (group A; n=8) or 11 minutes (group B; n=29) followed by reperfusion for 24 or 48 hours. Mean distal arterial blood pressure (left femoral artery) and lumbar (L1) spinal cord blood flow (laser-Doppler flowmetry) were measured for the duration of the procedure. The arterial blood supply of the spinal cord was visualized by intravascular perfusion of carbon black ink. We evaluated motor function in the hind limbs at 0, 1, 3, 6, and 24 hours after reperfusion using a rating scale of 0 (normal function) to 6 (total absence of movement). Spinal cord histopathology was evaluated after 24 and 48 hours of reperfusion by Luxol fast blue-hematoxylin and eosin. The vascular anatomy of the mouse and human spinal cord appeared similar in that blood was supplied by 1 anterior and 2 posterior spinal arteries and heterosegmental radicular arteries. During combined occlusion of aortic arch and left subclavian artery, mean distal arterial blood pressure dropped to 10+/-5 mm Hg, and spinal cord blood flow at the L1 level decreased to 27+/-7% of baseline. All animals recovered from anesthesia with acute paraplegia. Animals in the 9-minute group (group A) showed steady recovery of hind limb function over the ensuing 24 hours, whereas the majority (80%) in the 11-minute group (group B) remained paralyzed with maximum deficit throughout the postoperative period. Mortality was 0% and 21% in groups A and B, respectively. Maximal ischemic damage was observed at the lower thoracic and higher lumbar spinal levels in both groups. In group A (9 minutes), tissue damage was mild, affecting predominantly dorsal horns and intermediate gray matter, whereas ventral horns were minimally involved. All mice in group B (11 minutes) showed extensive gray matter lesions particularly involving dorsal horns and intermediate areas; in ventral horns, >50% of motor neurons died. White matter lesions were present in the most severely damaged cords only. Spinal cord ischemia caused by aortic arch plus left subclavian artery cross-clamping provides a mouse model useful for the study of spinal cord injury and of potential relevance to the complications following thoracoabdominal aortic surgery in humans.