This document discusses cardiovascular physiology including the structure and function of the heart, regulation of the cardiovascular system, blood flow through the pulmonary and systemic circulations, factors that influence cardiac output and stroke volume, and regulation of the systemic vasculature. Key points include:
- The cardiovascular system consists of the heart, blood vessels, and mechanisms that regulate blood circulation and pressure.
- Cardiac output is determined by stroke volume and heart rate. Stroke volume depends on preload, afterload, and contractility.
- The pulmonary circulation has low pressure and resistance while the systemic circulation has higher pressure and resistance.
- Autonomic nervous system and chemical factors regulate heart rate and contractility. Venous return and vascular
Neuromuscular monitoring, also known as train of four monitoring, is a technique used during recovery from the application of general anesthesia to objectively determine how well a patient's muscles are able to function. It involves the application of electrical stimulation to nerves and recording of muscle response using, for example, an acceleromyograph. Neuromuscular monitoring is typically used when neuromuscular-blocking drugs have been part of the general anesthesia and the doctor wishes to avoid postoperative residual curarization (PORC) in the patient, that is, the residual paralysis of muscles stemming from these drugs.
Intro to Hypoxic pulmonary vasoconstriction Arun Shetty
Hypoxic pulmonary vasoconstriction, a seldom heard phenomenon but very effective physiologic property which helps lungs utilise ventilation to the maximum
Neuromuscular monitoring, also known as train of four monitoring, is a technique used during recovery from the application of general anesthesia to objectively determine how well a patient's muscles are able to function. It involves the application of electrical stimulation to nerves and recording of muscle response using, for example, an acceleromyograph. Neuromuscular monitoring is typically used when neuromuscular-blocking drugs have been part of the general anesthesia and the doctor wishes to avoid postoperative residual curarization (PORC) in the patient, that is, the residual paralysis of muscles stemming from these drugs.
Intro to Hypoxic pulmonary vasoconstriction Arun Shetty
Hypoxic pulmonary vasoconstriction, a seldom heard phenomenon but very effective physiologic property which helps lungs utilise ventilation to the maximum
A patient with pacemaker presents a complex challenge to the attending anaesthesiologist. The mode of management will be according to the type of pacemaker implanted. This presentation discusses in brief the peri-operative consideration in a patient with pacemaker.
Scalp block is simple and easy to perform. It has the advantages of minimizing cardiovascular effects and decreasing intraoperative analgesia requirements.
New GCS, the GCS-P was adopted in 2018 by the same person who proposed GCS. It gives better prognosticate outcomes compared to GCS.
A patient with pacemaker presents a complex challenge to the attending anaesthesiologist. The mode of management will be according to the type of pacemaker implanted. This presentation discusses in brief the peri-operative consideration in a patient with pacemaker.
Scalp block is simple and easy to perform. It has the advantages of minimizing cardiovascular effects and decreasing intraoperative analgesia requirements.
New GCS, the GCS-P was adopted in 2018 by the same person who proposed GCS. It gives better prognosticate outcomes compared to GCS.
A general overview, and sometimes incomplete outline, of the things I know about hearts. This is how I structure info in my brain, and I thought it might be useful to other folks.
Cardiovascular physiology. Cardiac enzymes and their effects in the body system. Cardiac output and effects increasing and decreasing it. Calculations if Ejected fraction and other cardiac parameters.
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Anti ulcer drugs and their Advance pharmacology ||
Anti-ulcer drugs are medications used to prevent and treat ulcers in the stomach and upper part of the small intestine (duodenal ulcers). These ulcers are often caused by an imbalance between stomach acid and the mucosal lining, which protects the stomach lining.
||Scope: Overview of various classes of anti-ulcer drugs, their mechanisms of action, indications, side effects, and clinical considerations.
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
Atrioventricular conduction blocks ( AV blocks ) are classified into 3 types.
This document describes the acute management of AV block.
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
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7. Extrinsic Innervationof the Heart
• Heart is stimulated by
the sympathetic
cardioacceleratorycardi
oacceleratorycenter
center
• Heart is inhibited by
the parasympathetic
cardioinhibitorycardioi
nhibitorycentercenter
8.
9.
10.
11. Cardiac Output is the product of Stroke Volume
(SV) and Heart Rate (HR).
Stroke volume is determined by three factors:
preload, afterload and contractility
12. Normal Cardiac Output
•Normal resting cardiac output:
- Stroke volume of 70 ml
- Heart rate of 72 beats/minute
- Cardiac output ~ 5 litres/minute
•During exercise, cardiac output may increase
to > 20 liters/minutes
•You should be able to get stroke volume and
heart rate from volume-‐pressure curves and
ECG recordings, respectively
13. What are the Main Determinants of
Cardiac Performance?
• Preload
• Afterload
• Contractility
• Heart Rate
• Synergy of Contraction
14. Preload
• The force which fills the heart
• The extent of filling of the
heart
• Different definitions exist
– End-diastolic pressure
– End-diastolic volume
– Wall stress in diastole
Preload is the initial fibre length.
Preload is the load on myocardial
fibers just prior to contraction.
Therefore volume and
pressure are used as
surrogate markers of
preload.
15.
16. The Frank Starling Curve
• preload → stroke
volume (SV)
• Only occurs up to a
certain point, then SV
and CO (cardiac
output) falls
From Ashley & Niebauer. Cardiology Explained
17. Afterload
• The forces needed to push blood
forward
• The pressure the ventricle ejects
against
• Definitions
– Wall stress in systole
– End-systolic pressure
• ↑afterload → ↓SV
Afterload is the tension which needs to be
generated in cardiac muscle before
shortening will occur In its simplest terms
afterload is thought of as
the impedence to flow from the ventricle
during systole. As such mean arterial
pressure may be used as an estimate.
More accurate still it to consider the
relationship
between mean pressure and mean flow
represented by systemic vascular
resistance (or PVR on the right).
18.
19. Contractility
• The ability of the heart to contract with a given force
and rate
– Represented by dP/dV (or elastance, E)
– Independent of afterload and preload
Determined by
conditions within
the myocyte
Degree of binding
between actin and
myosin
Calcium is critical
is defined as the intrinsic ability of the
myocardial bre to shorten independent of
preload and
afterload. The intracellular mechanism that is
responsible for all factors which increase
contractility is increased intracellular calcium.
Measurement of contractility is difficult.
dp/dtmax refers the the maximum rate of
change in pressure in the left ventricle during
isovolumetric contraction. A more forceful
contraction would be associated with a
greater rise in pressure and for this reason
this is often used as a marker of contractility.
20. • Sympathetic stimulation
– Release norepinephrine from symp. postganglionic fiber
– Also, EP and NE from adrenal medulla
– Have positive ionotropic effect
– Ventricles contract more forcefully, increasing SV, increasing
ejection fraction and decreasing ESV
• Parasympathetic stimulation via Vagus Nerve -CNX
– Releases ACh
– Has a negative inotropic effect
• Hyperpolarization and inhibition
– Force of contractions is reduced, ejection fraction decreased
Effects of Autonomic Activity on
Contractility
21. Extrinsic Control of Contractility
• Contractility:
– Strength of contraction at
any given fiber length.
• Sympathoadrenal
system:
– NE and Epi produce an
increase in contractile
strength.
• + inotropic effect:
– More Ca2+ available
to sarcomeres.
• Parasympathetic
stimulation:
– Does not directly
influence contraction
strength.
Figure 14.2
22. Heart Rate and Stroke Volume
• HR influences SV
– ↑ HR leads to ↓ SV
– ↑ HR decreases
diastolic filling time
• ↓ Preload
• ↓ EDV
CO = HR × SV
23. Heart Rate and Cardiac Output
• Increasing HR only
increases CO to a
certain point
• Increasing HR also
increases force of
contraction slightly
Normal intrinsic heart rate = 118 beats/min
− (0.57 × age)
24. Synergy of Contraction
• AV synchrony
– Requires functional AV
node and His-Purkinje
– Atrial kick contributes up
to 20% of CO
• Intra- (or inter-)
ventricular synergy
– Requires functional
bundle branches (Purkinje
fibers)
– Bundle branch block
– Ectopic beats
25. Extrinsic Factors Influencing Stroke
Volume
• Contractility is the increase in contractile strength, independent of stretch
and EDV
• Referred to as extrinsic since the influencing factor is from some external
source
• Increase in contractility comes from:
– Increased sympathetic stimuli
– Certain hormones
– Ca2+ and some drugs
• Agents/factors that decrease contractility include:
– Acidosis
– Increased extracellular K+
– Calcium channel blockers
26. Normal Volume of Blood in Ventricles
•After atrial contraction, 110-120 ml in each
ventricle (end-diastolic volume)
•Contraction ejects ~70 ml (stroke volume
output)
•Thus, 40-50 ml remain in each ventricle (End‐
systolic volume)
•The fraction ejected is then ~60% (ejection
fraction)
27. Cardiac Output and Venous Return
•Cardiac output is the quantity of blood
pumped into the aorta each minute.
Cardiac output = stroke volume x heart rate
•Venous return is the quantity of blood flowing
from the veins to the right atrium.
•Except for temporary moments, the cardiac
output should equal the venous return
28. Cardiac Output
• Stroke Volume = the vol of blood pumped by
either the right or left ventricle during 1
ventricular contraction.
SV = EDV – ESV
70 = 125 – 55
CO = SV x HR
5,250 = 70 ml/beat x 75 beats/min
CO = 5.25 L/min
29. Cardiac Output
• Other chemicals can affect contractility:
- Positive inotropic agents: glucagon, epinephrine,
thyroxine, digitalis.
- Negative inotropic agents: acidoses, rising K+, Ca2+
channel blockers.
Afterload: Back pressure exerted by arterial blood.
Regulation of Heart Rate
• Autonomic nervous system
• Chemical Regulation: Hormones (e.g., epinephrine, thyroxine)
and ions.
30. Regulation of Stroke Volume
• SV: volume of blood pumped by a ventricle per beat
SV= end diastolic volume (EDV) minus end systolic volume
(ESV); SV = EDV - ESV
• EDV = end diastolic volume
– amount of blood in a ventricle at end of diastole
• ESV = end systolic volume
– amount of blood remaining in a ventricle after contraction
• Ejection Fraction - % of EDV that is pumped by the
ventricle; important clinical parameter
– Ejection fraction should be about 55-60% or higher
31. Factors Affecting Stroke Volume
• EDV - affected by
– Venous return - vol. of blood returning to heart
– Preload – amount ventricles are stretched by
blood (=EDV)
• ESV - affected by
– Contractility – myocardial contractile force due
to factors other than EDV
– Afterload – back pressure exerted by blood in
the large arteries leaving the heart
32. Wall Motion Abnormalities
Regional wall motion abnormalities cause a breakdown of the analogy between the
intact heart and skeletal muscle preparations.
Such abnormalities may be due to ischemia, scarring, hypertrophy, or altered
conduction.
When the ventricular cavity does not collapse symmetrically or fully, emptying
becomes impaired.
• Hypokinesis (decreased contraction),
• akinesis (failure to contract), and
• dyskinesis (paradoxic bulging) during systole reflect increasing degrees of
contraction abnormalities.
Although contractility may be normal or even enhanced in some areas,
abnormalities
in other areas of the ventricle can impair emptying and reduce stroke volume.
The severity of the impairment depends on the size and number of abnormally
contracting areas.
33. Valvular Dysfunction
Valvular dysfunction can involve any one of the four valves in the heart and can
include stenosis, regurgitation (incompetence), or both. Stenosis of an AV valve
(tricuspid or mitral) reduces stroke Volume primarily by decreasing ventricular
preload, whereas stenosis of a semilunar valve (pulmonary or aortic) reduces stroke
volume primarily by increasing ventricular afterload.
In contrast, valvular regurgitation can reduce stroke volume without changes in
preload, afterload, or contractility and without wall motion abnormalities.
The eff ective stroke volume is reduced by the regurgitant volume with every
contraction.
When an AV valve is incompetent, a significant part of the ventricular end-diastolic
volume can fl ow backward into the atrium during systole; the stroke volume is
reduced by the regurgitant volume.
Similarly, when a semilunar valve is incompetent, a fraction of end-diastolic volume
arises from backward flow into the ventricle during diastole.
35. ASSESSMENT OF
VENTRICULAR FUNCTION
1. Ventricular Function Curves
2. Assessment of Systolic Function:
Ejection Fraction
3. Assessment of Diastolic Function
36. Plotting cardiac output or
stroke volume against
preload (End-diastolic
pressure)is useful in evaluating
pathological states and
understanding drug therapy.
A curve that show
the contractility change in an
intact heart.
Ventricular pressure–volume diagrams are
useful because they dissociate contractility
from both preload and afterload.
It depends on the Starling’s law
A shift to the left in a ventricular function
curve usually signifies an enhancement of
contractility, whereas a shift to the right
usually indicates an impairment of
contractility, and a consequent tendency
toward cardiac failure.
. Ventricular Function Curves
37. Assessment of Systolic Function
The change in ventricular pressure over time during systole (
dP/dt ) is defined by the first derivative of the ventricular
pressure curve and is often used as a measure of contractility.
Contractility is directly proportional to dP/dt
It can be measured by:
-echocardiography
- the initial rate of rise in arterial pressure (rough estimation)
The usefulness of dP/dt is also limited in that it may be affected
by preload, afterload, and heart rate.
38. Ejection Fraction
What? The ventricular ejection
fraction (EF), the
fraction of the end-diastolic ventricular
volume
Ejected.
the most commonly used clinical measurement
of systolic function.
Normal EF is approximately 0.67±8
EDV is left ventricular diastolic
volume and ESV is end-systolic
volume.
Measurements can be made preoperatively from
•cardiac catheterization,
•radionucleotide studies, or
• transthoracic (TTE)
•or transesophageal echocardiography (TEE).
Pulmonary artery catheters with
fast-response thermistors allow
measurement of the right
ventricular EF.
39. Assessment of Diastolic Function
Left ventricular diastolic function can be assessed clinically by Doppler
echocardiography on a transthoracic or transesophageal.
Tissue Doppler is frequently used to distinguish “pseudonormal” from normal
diastolic function.
Tissue Doppler is also an excellent way to detect “conventional” diastolic
dysfunction.
40. Systemic Circulation
The systemic vasculature can be divided
Functionally into arteries, arterioles, capillaries,
and veins.
Arteries are the high-pressure conduits that
Supply the various organs.
Arterioles are the small vessels that directly
feed and control blood flow through each
capillary bed.
Capillaries are thin-walled vessels that allow the
exchange of nutrients between blood and
tissues.
Veins return blood from capillary beds to
the heart.
most of the blood volume is in the systemic
circulation—specifi cally, within systemic veins.
Changes in systemic venous tone allow these
vessels to function as a reservoir for blood.
41. Following significant blood or fluid losses,
a sympathetically mediated increase in venous
tone reduces the caliber of these vessels and shifts
Blood into other parts of the vascular system.
Conversely, venodilation allows these vessels to
accommodate increases in blood volume.
Sympathetic control of venous tone is an important
determinant of venous return to the heart.
Reduced venous tone following induction of anesthesia
frequently results in venous pooling of blood and
contributes to hypotension.
42. AUTOREGULATION
Most tissue beds regulate their own blood flow
(autoregulation).
Arterioles generally dilate in response to reduced
perfusion pressure or increased tissue demand.
Conversely, arterioles constrict in response to increased
pressure or reduced tissue demand.
These phenomena are likely due to both an intrinsic
response of vascular smooth muscle to stretch and the
accumulation of vasodilatory metabolic by-products.
The latter may include K + , H + , CO 2 , adenosine, and
lactate.
43. ENDOTHELIUM-DERIVED FACTORS
The vascular endothelium is metabolically active in elaborating or modifying
substances that directly or indirectly play a major role in controlling blood pressure and
flow.
These include:
vasodilators (eg, nitric oxide, prostacyclin [PGI 2 ]),
Vasoconstrictors (eg, endothelins, thromboxane A 2 ),
Anticoagulants (eg, thrombomodulin, protein C),
fibrinolytics (eg, tissue plasminogen activator), and
factors that inhibit platelet aggregation (eg, nitric oxide and PGI 2 ).
Nitric oxide is synthesized from arginine by nitric oxide synthetase. This substance has a
number of functions In the circulation, it is a potent vasodilator. It binds guanylate cyclase,
increasing cGMP levels and producing vasodilation.
Endothelially derived vasoconstrictors (endothelins) are released in response to
thrombin and epinephrine.
44. AUTONOMIC CONTROL OF
THE SYSTEMIC VASCULATURE
Autonomic control of the vasculature is primarily sympathetic
Sympathetic fibers innervate all parts of the vasculature
except for capillaries. Their principal function is to regulate
vascular tone.
Variations of arterial vascular tone serve to regulate blood
pressure and the distribution of blood flow to the various
organs, whereas variations in venous tone alter vascular
capacity, venous pooling, and venous return to the heart.
Vascular tone and autonomic influences on the heart are
controlled by vasomotor centers in the reticular formation of
the medulla and lower pons.
The sympathetic system normally maintains some tonic vasoconstriction
on the vascular tree. Loss of this tone following induction of anesthesia or
sympathectomy frequently contributes to perioperative hypotension.
45. ARTERIAL BLOOD PRESSURE
Systemic blood flow is pulsatile in large arteries because of
the heart’s cyclic activity; by the time blood reaches the
systemic capillaries, flow is continuous(laminar).
The mean pressure falls to less than 20 mm Hg in the large
systemic veins that return blood to the heart. The largest
pressure drop, nearly 50%, is across the arterioles, and the
arterioles account for the majority of SVR.
MAP is proportionate to the product of
SVR . CO. This relationship is based on an
analogy to Ohm’s law, as applied to the
circulation:
Because CVP is normally very small compared with MAP, the former can usually be
ignored.
From this relationship, it is readily apparent that hypotension is the result of a
decrease in SVR, CO, or both: To maintain arterial blood pressure, a decrease
in either SVR or CO must be compensated by an increase in the other.
46. MAP can be measured as the integrated mean of the arterial pressure waveform.
Alternatively, MAP may be estimated by the following
formula:
pulse pressure is the difference between systolic and diastolic
blood pressure.
Arterial pulse pressure is directly related to stroke volume, but is
inversely proportional to the compliance of the arterial tree.
Thus, decreases in pulse pressure may be due to a decrease in
stroke volume, an increase in SVR, or both.
Increased pulse pressure increases shear stress on vessel walls,
potentially leading to atherosclerotic plaque rupture and
thrombosis or rupture of aneurysms.
Increased pulse pressure in patients undergoing cardiac surgery
has been associated with adverse renal and neurological
outcomes.
47. Control of Arterial Blood Pressure
A. Immediate Control
B. Intermediate Control
C. Long-Term Control
48. Immediate Control
Minute-to-minute control of blood pressure is primarily the
function of autonomic nervous system reflexes.
Changes in blood pressure are sensed both
centrally (in hypothalamic and brainstem areas)and
peripherally by specialized sensors (baroreceptors).
Decreases in arterial blood pressure result in increased sympathetic tone,
increased adrenal secretion of epinephrine, and reduce vagal activity. The
resulting systemic vasoconstriction, increased heart rate, and enhanced
cardiac contractility serve to increase blood pressure .
Peripheral baroreceptors are located at the bifurcation of the common carotid
arteries and the aortic arch. Elevations in blood pressure increase baroreceptor discharge,
inhibiting systemic vasoconstriction and enhancing vagal tone (baroreceptor reflex) .
Reductions in blood pressure decrease baroreceptor discharge, allowing vasoconstriction and
reduction of vagal tone.
Carotid baroreceptors send afferent signals to circulatory brainstem centers via Hering’s nerve
(a branch of the glossopharyngeal nerve), whereas aortic baroreceptor afferent signals travel
along the vagus nerve.
49. Of the two peripheral sensors, the carotid baroreceptor is physiologically
more important and is primarily responsible for minimizing changes in blood
pressure that are caused by acute events, such as a change in posture.
Carotid baroreceptors sense MAP most effectively between pressures of 80
and 160 mm Hg. Adaptation to acute changes in blood pressure occurs over
the course of 1–2 days, rendering this reflex ineffective for longer term blood
pressure control.
All volatile anesthetics depress the normal baroreceptor response, but
isoflurane and desflurane seem to have less effect.
Cardiopulmonary stretch receptors located in the atria, left ventricle, and
Pulmonary circulation can cause a similar effect.
50. B. Intermediate Control
In the course of a few minutes, sustained decreases in arterial pressure, together with enhanced
sympathetic outflow, activate the renin–angiotensin–aldosterone system, increase secretion of
arginine vasopressin (AVP), and alter normal capillary fluid exchange.
Both angiotensin II and AVP are potent arteriolar vasoconstrictors. Their immediate action is to
increase SVR.
Sustained changes in arterial blood pressure can also alter fluid exchange in tissues by their
Secondary effects on capillary pressures.
Hypertension increases interstitial movement of intravascular fluid, whereas hypotension
increases reabsorption of interstitial fluid. Such compensatory changes in intravascular volume
can reduce fluctuations in blood pressure, particularly in the absence of adequate renal function
51. C. Long-Term Control
The effects of slower renal mechanisms become apparent
within hours of sustained changes in arterial pressure.
As a result, the kidneys alter total body sodium and water
balance to restore blood pressure to normal.
Hypotension results in sodium (and water)retention,
whereas hypertension generally increases sodium
excretion in normal individuals.
52. ANATOMY & PHYSIOLOGY OF
THE CORONARY CIRCULATION
1. Anatomy
2. Determinants of Coronary Perfusion
3. Myocardial Oxygen Balance
4.EFFECTS OF ANESTHETIC AGENTS
53. 1. Anatomy
The right and left coronary arteries.
Blood flows from epicardial to endocardial vessels.
After perfusing the myocardium, blood returns to the right
atrium via the coronary sinus and the anterior cardiac veins.
A small amount of blood returns directly into the chambers of
the heart by way of the thebesian veins.
The right coronary artery (RCA) normally supplies the right atrium,
most of the right ventricle, and a variable portion of the left
ventricle (inferior wall).
The left coronary artery normally supplies the left atrium and most of
the interventricular septum and left ventricle (septal, anterior, and
lateral walls).
After a short course, the left main coronary artery bifurcates into the
left anterior descending artery (LAD) and the circumfl ex artery (CX);
the LAD supplies the septum and anterior wall and the CX supplies the
lateral wall.
54. Intermittent rather than continuous
The force of left ventricular contraction almost
completely occludes the intramyocardial part of the
coronary arteries.
coronary perfusion pressure is usually determined by the
difference between aortic pressure and ventricular
pressure .
the left ventricle is perfused almost entirely during
diastole.
In contrast, the right ventricle is perfused during both systole
and diastole
2. Determinants of Coronary Perfusion
55. Decreases in aortic pressure or increases in ventricular
end-diastolic pressure can reduce coronary perfusion
pressure.
Increases in heart rate also decrease coronary perfusion
because of the disproportionately greater reduction in
diastolic time as heart rate increases .
Because it is subjected to the greatest intramural
pressures during systole, the endocardium tends to be
most vulnerable to ischemia during decreases in
coronary perfusion pressure.
57. In the average adult man,coronary blood flow is approximately 250 mL/min at rest.
Th e myocardium regulates its own blood flow closely between perfusion pressures of 50
and 120 mm Hg.
Beyond this range, blood flow becomes increasingly pressure dependent.
Under normal conditions, changes in blood flow are entirely due to variations in coronary
arterial tone (resistance) in response to metabolic demand.
Hypoxia—either directly, or indirectly through the release of adenosine—causes coronary
vasodilation.
Autonomic influences are generally weak. Both α 1 - and β 2 -adrenergic receptors are
present in the coronary arteries. The α 1 –receptors are primarily located on larger
epicardial vessels, whereas the β 2 -receptors are mainly found on the smaller
intramuscular and subendocardial vessels.
Sympathetic stimulation generally increases myocardial blood flow because of an increase
in metabolic demand and a predominance of β 2 –receptor activation.
Parasympathetic effects on the coronary vasculature are generally minor and weakly
vasodilatory.
58. 3. Myocardial Oxygen Balance
Myocardial oxygen demand is usually the most
important determinant of myocardial blood flow.
Relative contributions to oxygen requirements
include basal requirements (20%), electrical activity
(1%), volume work (15%), and pressure work(64%).
Th e myocardium usually extracts 65% of
the oxygen in arterial blood, compared with 25%
in most other tissues.
Coronary sinus oxygen saturation is usually 30%.
Therefore, the myocardium (unlike other tissues) cannot
compensate for reductions in blood fl ow by extracting more
oxygen from hemoglobin.
Any increases in myocardial metabolic
demand must be met by an increase in coronary
blood fl ow.
in myocardial oxygen demand and supply. Note
that the heart rate and, to a lesser extent, ventricularend-
diastolic pressure are important determinants
of both supply and demand.
59. EFFECTS OF ANESTHETIC
AGENTS
Most volatile anesthetic agents are coronary vasodilators.
Their effect on coronary blood flow is variable because of their direct vasodilating
properties, reduction of myocardial metabolic requirements (and secondary decrease
due to autoregulation), and effects on arterial blood pressure.
The mechanism is not clear, and these effects are unlikely to have any clinical
importance.
Halothane and isoflurane seem to have the greatest effect; the former primarily
affects large coronary vessels, whereas the latter affects mostly smaller vessels.
Vasodilation due to desflurane seems to be primarily autonomically mediated,
whereas sevoflurane seems to lack coronary vasodilating properties. Dose-
dependent
abolition of autoregulation may be greatest with isoflurane.
and afterload.
60. Volatile agents exert beneficial effects in experimental myocardial
ischemia and infarction.
They reduce myocardial oxygen requirements and protect against
reperfusion injury; these effects are mediated by activation of ATP-
sensitive K+ (K ATP ) channels.
Some evidence also suggests that volatile anesthetics enhance
recovery of the “stunned” myocardium (hypocontractile,
but recoverable, myocardium aft erischemia).
Moreover, although volatile anesthetics decrease myocardial
contractility, they can be potentially beneficial in patients with heart
failure because most of them decrease preload