Effects of body position on intracranial and cerebral  perfusion pressures in isoflurane-anesthetized horses

Inhalant anesthetics may interfere with normal cerebrovascular autoregulation. It was, therefore, hypothesized that intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in isoflurane-anesthetized horses would be especially sensitive to body and head position because of the potential for large hydrostatic gradients between the brain and heart in this species. Anesthesia was induced and maintained in six clinically healthy, unmedicated geldings with 1.57% isoflurane in O2; mechanical ventilation was used to maintain normocapnia. ICP was measured by using a subarachnoid strain-gauge transducer. Blood gases and carotid arterial, right atrial, and airway pressures were also measured. Five body positions were studied in semirandomized order: dorsal recumbency (DR) with head down (HD), DR with head level (HL), lateral recumbency (LR), sternal recumbency (SR) with HL, and SR with head up (HU). Data were analyzed by using paired t-tests. ICP and CPP values, respectively, are as follows (means ± SD): 36 ± 4 and 55 ± 18 mmHg (DR-HD); 34 ± 6 and 51 ± 32 mmHg (DR-HL); 24 ± 5 and 48 ± 4 mmHg (LR); 19 ± 11 and 87 ± 12 mmHg (SR-HL); and −14 ± 7 and 71 ± 10 mmHg (SR-HU). Significant differences were found among all positions, except for SR-HL vs. LR. Significant increases in CPP were observed only in sternal positions. In conclusion, ICP in isoflurane-anesthetized horses changes inversely with the brain-to-heart hydrostatic gradient. DR may also cause increases in ICP, irrespective of head position.

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Postural influence on intracranial and cerebral perfusion pressure in ambulatory neurosurgical patients

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00302.2015 ◽

2016 ◽

Vol 310 (1) ◽

pp. R100-R104 ◽

Cited By ~ 47

Author(s):

L. G. Petersen ◽

J. C. G. Petersen ◽

M. Andresen ◽

N. H. Secher ◽

M. Juhler

Keyword(s):

Cerebral Perfusion Pressure ◽

Cerebral Perfusion ◽

Perfusion Pressure ◽

Body Position ◽

Standing Position ◽

Brain Parenchyma ◽

Focal Lesions ◽

Neurosurgical Patients ◽

Standing Up ◽

The Brain

We evaluated postural effects on intracranial pressure (ICP) and cerebral perfusion pressure [CPP: mean arterial pressure (MAP) − ICP] in neurosurgical patients undergoing 24-h ICP monitoring as part of their diagnostic workup. We identified nine patients (5 women, age 44 ± 20 yr; means ± SD), who were “as normal as possible,” i.e., without indication for neurosurgical intervention (e.g., focal lesions, global edema, abnormalities in ICP-profile, or cerebrospinal fluid dynamics). ICP (tip-transducer probe; Raumedic) in the brain parenchyma ( n = 7) or in the lateral ventricles ( n = 2) and cardiovascular variables (Nexfin) were determined from 20° head-down tilt to standing up. Compared with the supine position, ICP increased during 10° and 20° of head-down tilt (from 9.4 ± 3.8 to 14.3 ± 4.7 and 19 ± 4.7 mmHg; P < 0.001). Conversely, 10° and 20° head-up tilt reduced ICP to 4.8 ± 3.6 and 1.3 ± 3.6 mmHg and ICP reached −2.4 ± 4.2 mmHg in the standing position ( P < 0.05). Concordant changes in MAP maintained CPP at 77 ± 7 mmHg regardless of body position ( P = 0.95). During head-down tilt, the increase in ICP corresponded to a hydrostatic pressure gradient with reference just below the heart, likely reflecting the venous hydrostatic indifference point. When upright, the decrease in ICP was attenuated, corresponding to formation of a separate hydrostatic gradient with reference to the base of the skull, likely reflecting the site of venous collapse. ICP therefore seems to be governed by pressure in the draining veins and collapse of neck veins may protect the brain from being exposed to a large negative pressure when upright. Despite positional changes in ICP, MAP keeps CPP tightly regulated.

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Platelet Hyperaggregability in Ischemic Cerebrovascular Disease and Effects of Aspirin

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657237 ◽

1982 ◽

Vol 48 (02) ◽

pp. 117-119 ◽

Cited By ~ 6

Author(s):

M Kusunoki ◽

K Kimura ◽

K Nagatsuka ◽

Y Isaka ◽

O Uyama ◽

...

Keyword(s):

Cerebrovascular Disease ◽

Venous Blood ◽

Second Phase ◽

Cerebral Angiogram ◽

Peripheral Venous Blood ◽

Chronic Stage ◽

Ischemic Cerebrovascular Disease ◽

Carotid Arterial ◽

Platelet Hyperaggregability ◽

The Brain

SummaryPlatelet aggregation was studied in 24 patients in the chronic stage of ischemic cerebrovascular disease (CVD), with cerebral affluent and effluent blood, i.e., carotid arterial and internal jugular venous blood, and also with peripheral venous blood. Aggregation tests were performed at various final concentrations of sodium arachidonate (A.A.) and ADP. In 17 patients, not taking aspirin, platelet aggregability in jugular venous blood was significantly accentuated compared with that in arterial and peripheral venous blood. This tendency was more marked in the patients with cerebral artery stenosis and/or occlusion than in those with normal cerebral angiogram. In 7 patients taking 500 mg or more oral aspirin, aggregation differences across the brain were not observed and A.A. aggregation and the second phase of ADP aggregation were completely suppressed. These results suggest that a prophylactic administration of aspirin may be beneficial for patients in chronic stage of CVD.

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Craniocerebral missile injuries in the monkey: an experimental physiological model

Journal of Neurosurgery ◽

10.3171/jns.1972.36.1.0043 ◽

1972 ◽

Vol 36 (1) ◽

pp. 43-49 ◽

Cited By ~ 17

Author(s):

Arthur M. Gerber ◽

Robert A. Moody

Keyword(s):

Rhesus Monkeys ◽

Common Factor ◽

Blood Gases ◽

Physiological Model ◽

Content Type ◽

Epidural Compression ◽

The Brain ◽

Strong Suspicion ◽

Fine Print ◽

Carotid Flow

✓ Experiments were carried out on rhesus monkeys to determine what physiological parameters were most closely correlated with death due to craniocerebral missile injuries. Observations of intracranial pressure, blood pressure, carotid flow, blood gases, respiratory rate, depth and volume, and electroencephalograms were made. These parameters were compared in survivors and nonsurvivors as were the pathological injuries. The most important single parameter that correlated with death was the drop in carotid flow. As this same correlation has been observed in epidural compression experiments in the monkey, there is a strong suspicion that reduced blood flow to the brain as measured by carotid flow is a common factor in craniocerebral missile injuries and epidural compression injuries.

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Unilateral Antegrade Cerebral Perfusion Through the Right Axillary Artery Provides Uniform Flow Distribution to Both Hemispheres of the Brain : A Magnetic Resonance and Histopathological Study in Pigs

Circulation ◽

10.1161/01.cir.100.suppl_2.ii-309 ◽

1999 ◽

Vol 100 (Supplement 2) ◽

pp. II-309-II-315 ◽

Cited By ~ 2

Author(s):

J. Ye ◽

G. Dai ◽

L. N. Ryner ◽

P. Kozlowski ◽

L. Yang ◽

...

Keyword(s):

Magnetic Resonance ◽

Cerebral Perfusion ◽

Axillary Artery ◽

Flow Distribution ◽

Uniform Flow ◽

Histopathological Study ◽

Uniform Flow Distribution ◽

The Right ◽

The Brain ◽

Antegrade Cerebral Perfusion

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Attenuation of Haemodynamic Response to Placement of Mayfield Skull Pin Head Holder - Comparison of Dexmedetomidine Versus Propofol Infusion - A Randomized Interventional Trial Done in a Tertiary Centre in Central Kerala

Journal of Evidence Based Medicine and Healthcare ◽

10.18410/jebmh/2021/486 ◽

2021 ◽

Vol 8 (29) ◽

pp. 2639-2643

Author(s):

Sruthy Unni ◽

Ranju Sebastian ◽

Elizabeth Joseph ◽

Remani Kelan Kamalakshi ◽

Jamsheena Muthira Parambath

Keyword(s):

Blood Pressure ◽

Nervous System ◽

Stress Response ◽

Intracranial Pressure ◽

Cerebral Perfusion ◽

Perfusion Pressure ◽

Neurosurgical Procedures ◽

Sympathetic Nervous ◽

The Brain ◽

Group 1

BACKGROUND Anaesthesia for neurosurgery requires special considerations. The brain is enclosed in a rigid cranium, so the rise in intracranial pressure (ICP) which impairs cerebral perfusion pressure (CPP), results in irrepairable damage to various vital areas in the brain. Stable head position is required in long neurosurgical procedures. This is obtained with the use of clamps which fix the head rigidly. This is done usually under general anaesthesia because it produces intense painful stimuli leading to stimulation of sympathetic nervous system which in turn causes release of vasoconstrictive agents. This can impair perfusion in all organ systems. The increase in blood pressure due to sympathetic nervous system causes increase in blood flow. This causes increases in intracranial pressure which result in reduction in cerebral perfusion pressure once the auto regulatory limits are exceeded. We compared the effects of dexmedetomidine 1 µgm/kg and propofol 100 µgm/kg given as infusion over a period of 10 minutes before the induction of anaesthesia and continued till 5 minutes after pinning to attenuate the stress response while cranial pinning. In this study, we wanted to compare the effects of dexmedetomidine and propofol as infusion to attenuate the stress response while cranial pinning in patients undergoing neurosurgical procedures. METHODS This is a randomized interventional trial. Patients were divided into 2 groups of 20 each. Group 1 receiving dexmedetomidine and group 2 receiving propofol, both drugs given as infusion. Haemodynamic variables were monitored before and after cranial pinning. Data was analysed using IBM statistical package for social sciences (SPSS) statistics. The parameters recorded were analysed with the help of a statistician. RESULTS The two groups were comparable in demographic data. Incidence of tachycardia between group 1 and 2 showed that tachycardia to pinning was better controlled with propofol than dexmedetomidine (P < 0.05) which is statistically significant. There is no statistically significant difference in blood pressure values between group 1 and 2 after pinning. CONCLUSIONS From our study, we came to a conclusion that propofol was superior to dexmedetomidine in attenuating the heart rate response to cranial pinning. The effect of propofol and dexmedetomidine was comparable in attenuating the blood pressure response to cranial pinning. KEYWORDS Cranial Pinning, Dexmedetomidine, Propofol

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Respiratory syncytial virus infection in anesthetized weanling rather than adult rats prolongs the apneic responses to right atrial injection of capsaicin

Journal of Applied Physiology ◽

10.1152/japplphysiol.01436.2006 ◽

2007 ◽

Vol 102 (6) ◽

pp. 2201-2206 ◽

Cited By ~ 12

Author(s):

Wenhong Peng ◽

Jianguo Zhuang ◽

Kevin S. Harrod ◽

Fadi Xu

Keyword(s):

Respiratory Syncytial Virus ◽

Blood Gases ◽

Respiratory Frequency ◽

Right Atrial ◽

Arterial Blood Gases ◽

Adult Rats ◽

Intranasal Inoculation ◽

Arterial Blood ◽

Rsv Infection ◽

Syncytial Virus

Apnea is a common complication in infants infected by respiratory syncytial virus (RSV). A recent study has shown that intranasal inoculation of RSV in conscious weanling rats strengthens the apneic responses to right atrial injection of capsaicin (CAP), leading to 66% mortality. The objectives of the present study were to determine 1) whether RSV infection changes baseline minute ventilation (V̇e) and arterial blood gases in anesthetized rats; 2) what the effects of RSV infection are on the respiratory responses to CAP; and 3) whether the RSV-strengthened apneic responses are age dependent. Our experiments were conducted in anesthetized and spontaneously breathing rats divided into four groups of weanling and adult rats that received either intranasal inoculation of RSV or virus-free medium. Two days after RSV infection (0.7 ml/kg), animal blood gases, baseline V̇e, and V̇e responses to right atrial injection of three doses of CAP (4, 16, and 64 μg/kg) were measured and compared among the four groups. Our results showed that RSV infection increased respiratory frequency (∼25%, P < 0.05) in weanling but not adult rats, with little effect on arterial blood gases. RSV infection amplified the apneic responses to CAP in weanling but not adult rats, characterized by increases in the initial (40%) and the longest apneic duration (650%), the number of apneic episodes (139%), and the total duration of apneas (60%). These amplifications led to 50% mortality ( P < 0.05). We conclude that RSV infection increases respiratory frequency and strengthens the apneic responses to CAP only in anesthetized weanling but not adult rats.

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Vestibular Signals in Self-Orientation and Eye Movement Control

Physiology ◽

10.1152/physiologyonline.2001.16.5.234 ◽

2001 ◽

Vol 16 (5) ◽

pp. 234-238 ◽

Cited By ~ 1

Author(s):

Bernhard J. M. Hess

Keyword(s):

Signal Processing ◽

Eye Movement ◽

Vestibular System ◽

Retinal Image ◽

Internal Model ◽

Movement Control ◽

Head Position ◽

Head Motion ◽

Afferent Information ◽

The Brain

The central vestibular system receives afferent information about head position as well as rotation and translation. This information is used to prevent blurring of the retinal image but also to control self-orientation and motion in space. Vestibular signal processing in the brain stem appears to be linked to an internal model of head motion in space.

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Retrograde Cerebral Perfusion with Hypothermic Blood Provides Efficient Protection of the Brain: A Neuropathological Study

Journal of Cardiac Surgery ◽

10.1111/j.1540-8191.1995.tb00619.x ◽

1995 ◽

Vol 10 (4) ◽

pp. 325-333 ◽

Cited By ~ 12

Author(s):

Mizuho Imamaki ◽

Hitoshi Koyanagi ◽

Akimasa Hashimoto ◽

Shigeyuki Aomi ◽

Mitsuhiro Hachida

Keyword(s):

Cerebral Perfusion ◽

Retrograde Cerebral Perfusion ◽

Efficient Protection ◽

The Brain

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Cardiovascular responses to insulin in the absence of hypoglycemia

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1962.202.2.249 ◽

1962 ◽

Vol 202 (2) ◽

pp. 249-252 ◽

Cited By ~ 57

Author(s):

Santiago A. Pereda ◽

John W. Eckstein ◽

François M. Abboud

Keyword(s):

Pressor Response ◽

Direct Action ◽

Cardiovascular Responses ◽

Blocking Agent ◽

Neuromuscular Blocking ◽

Right Atrial ◽

Systemic Vein ◽

Anesthetized Dogs ◽

Adrenergic Blocking ◽

The Brain

Cardiovascular responses to intravenous administration of insulin were studied in lightly anesthetized dogs treated with a neuromuscular blocking agent. An early transient pressor response was observed. This abrupt increase in arterial pressure appeared 2–9 min after insulin was given. It was accompanied by increases in cardiac output and right atrial pressure. It occurred in the presence of hyperglycemia and in the absence of hypoglycemia. It was not altered by glucagon but it could be antagonized by ganglionic and adrenergic blocking drugs and by pentobarbital. The response could be produced when insulin was given in the carotid artery in doses that caused no effect when injected in a systemic vein. The experiments suggest that insulin may have a direct action on the brain.

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