Physiology Flashcards
Define the following Stunned Hibernating re-reflow stone heart syndrome: massive muscular contraction of the whole myocardium that follows an end0stage massive reperfusion injury, no possible recuperation, very poor prognosis
Stunned: temporary akinesia of a myocardial territory after ischemia-reperfusion, reversible condition, excellent recovery
hibernating: akinetic territory that has the ability to recover contractile activity after angioplastic or surgical revascularization
no-reflow phenomenon: massive endovascular occlusion by neutrophil and platelet adhesion that follow a severe ischemia-reperfusion syndrome. poor recuperation and prognosis
stone heart syndrome:
What are potential negative effects of sodium bicarbonate administration during CPR
Hypernatremia
Hyperosmolarity
shifting oxyhemoglobin to the left (inhibiting the release of oxygen)
paradoxical acidosis from carbon dioxide formation
How much narrowing of the cross sectional area of a coronary must occur for there to be a reduction on coronary flow with exertion? at rest?
70% and 90%
List 3 acute coronary sydromes
Unstable Angina
Acute myocardial infarction
sudden ischemic death
coronary artery dissection
Name 3 physiologic components which contribute to coronary vascular resistance in the non-diseased heart
Viscous resistance
autoregulatory resistance
compressive resistance
List 4 factors that results in a shift to the right of the oxygen/hemoglobin dissociatiion curve
increased PCO2
increase in temperature
decrease in pH
increase in 2, 3 DPG
List the three basic categories of physiologicl derangements which can lead to tissue hypoxia and give one clinical example of each
Inadequate blood oxygenation cardiogenic/pulmonary edema ARDS acute lung injury inadequate delivery of oxygen to tissues low cardiac output Abnormal inability to extract from the blood sepsis
Pressure-volume loops and the End systolic pressure-volume relation slope is an indication of contractility
When an inotrope is administered, in which direction does the EPVR slope shift?
In heart with systolic failure in which direction does the ESPVR slope shift
Inotrope: upward and to the left
In failing heart– right and slightly down.
What is the equation for Laplace Law governing the wall stress of an arterial wall
Wall stress is proportional to (P x r) divided by (2 x wall thickness)
List 4 mechanisms responsible for the cellular damage produced during post-ischemic reperfusion injury
Release of free radical ( OH, O2, H2O2)
alteration of membrane phospholipid causing impairment of cellular tntegrity
Calcium-induced injury related to to increased Ca influsion
ATPase causing destruction of ATP intracellular storage
Leucocyte mediated injury
endothelial cell injury and no-reflow phenomenon``
What are determinants of oxygen delivery
cardiac output
hemoglobin
saturation of hemoglobin with oxygen saturation
dissolved oxygen measured by the partial pressure of oxygen
D = CO X 10 (HGB x 1.36 x O2sat) + PaO2 X 0.003
What is normal Coronary blood flow
8 -15 ml/100/min in a beating heart
1.5 ml/100gm/min in an arresting heart
List Endothelial vasodilators
Nitric Oxide
Endothelium Derived relaxing factor
Bradykinin
Prostayclin
List Endothelial vasoconstrictors
Angiotensin II
Thromboxane
Edothelin-1 (ET1)
What is normal range for mixed venous saturation
65-75%
What are reasons why the mixed venous saturation would be less than 60%
Reduced oxygen-carrying capacity Acidosis Cardiac decompensation cellular injury stress (? )
What are reasons why the mixed venous saturation would be very high
sepsis
hypothermic
wedged PA catheter
physiologic or anatomic shunting
List mechanisms of contractile dysfunction after myocardial stunning
generation of oxygen-derived free radicals
Calcium overload
Excitation-contraction uncoupling due to sarcoplasmic reticulum dysfunction
Insufficient energy production by mitochondria
Impaired energy use by myofibrils
Impaired sympathetic neural responsiveness
Damage to the extracellular collagen matrix
Decreased sensitivity of myofilaments to calcium
List mechanisms of ischemic reperfusion injury
Mitochondrial dysfunction
Calcium overload and cellular hypertracture
Oxygen and other free radical generation
Apoptosis
Intracellular calcium influx
Activation of leukocytes
Complement activation
List severe oxygen or free radicals that are generated with ischemia
superoxide anion
hydrogen peroxide
nitric oxide derived peroxynitrate
hydoxyl radical
How do neutrophils get activated during CPB
Activated by Kallikrein
contact system
complement system
Recruited by cytokines, complement, IL-1
Release cytokines, and phagocytose cells
Produce arachadonic acid metabolites and prostaglandins to mediate systemic inflammatory response syndrome
List fluid analysis of chlothorax
Odorless, milky white fluid High triglyceride content 1.1 mmol/L Specific gravity > 1.012 white count is lymphocytic 3000 to 20 000 cells/cc Albumin 1-g/dl
List the factors in Child-pugh classification of assessing liver cirrhosis
Bilirubin Albumin INR encepalopathy ascities <7 cardiac surgery mortality is not affected 7-9 cardiac mortality is 41 to 80% > 9 (1-3 month survival, cardiac surgery mortality is 100%)
How do you calculate shunt fraction for ASD
Qp/Qs
Sat (aortic) - Mixed venous sat (usually mix of IVC (2/3) and svc 1/3) DIVIDED by pulmonary venous sat - pulmonary artery sat
How do you calculate Pulmonary Vascular resistance (mmHg/L/min)
Mean pulmonary arterial pressure - pulmonary capillary wedge pressure/Cardiac outpult
to get Dynes.sec.cm-5 you just multiple by 80
What are PVR limitations for operating when it comes to ASD
If PVR above 8 you do not operate
If PVR is 6 to 8 check for vasodilatory challenge
if the PVR is less then 6 then it’s ok to operate
List advantages of LMWH
decreased heparin resistance decreased incidence of HIT (1 vs 5%) No need for monitoring Increased half life decreased risk of bleeding
How do you calculate mean pulmonary artery pressure
PASP -PADP/3 + PADP
this is the same as mean arterial pressure
Describe the phases of Cardiomyocyte action potential
Phase 0: influx of sodium ions causes membrane to become transiently positive
Phase 1: opening of the K challens to leave the cell (slowing makes it negative)
Phase 2: Opening of Ca allows the balance of exit of K cells to keep a plateu phase.
Phase 3: Closure of Ca channel (repolarization and -90m(
Phase 4: resting period occurs because as cell prepares for next excitation
What is Bohr effect
Factors such as acidosis, hypercapnia, increasing temp that cause a right shift of the oxygen dissociation curve, thereby encouraging oxygen release to the tissues
What are the wave forms of the Central line tracing
A wave = atrial contraction
x decent = atrial diastole
c wave = ventricular systole leading to AV closure
X prime decent = the remainder of x decent
v wave = atrial filling against a closed AV valve, ventricular systole
Y descent = ventricular diastole and opening of the AV valve
What happens in Cardiac tamponade
the waveform shows attenuated y descent (reduced atrial filling) with or without a prominent x descent
What happens to central line tracing in tricuspid regurgitation
Waveform shows large V waves
What happens to central line tracing with pacemaker syndrome
cannon a waves, due to atrial contraction against a closed tricuspid valve
What is the mechanism of action and the role of spinal cord stimulation in the treatment of angina
Simulate at level of T1-T2
Mechanism
- suppressing the capacity of intrinsic cardiac neurons to generate activity during myocardial ischemia
-reduces sympathetic activity by redistributing myocardial blood from nonishemic areas
List potential benefits of Pulsatile flow
Increase lymph flow, energy to microcirculation, oxygen consumption, cellular metabolism, tissue perfusion
Decrease: vasoconstrive effect, acidosis, neuroendo response, critical capillary closing pressure
What are lesions of Atherosclerosis
Fatty streak—Invasion of intima
Diffuse Intimal thickening–increased smooth muscle cells; increase connective tissue
Fibrous plaque–proliferation smooth muscle cells, fibrous cap, zone of necrotic tissue
Advanced lesion–calcification, hemorrhage, fissure and cracks in intima
What are the potential negative effects of Sodium Bicarbonate administration during CPB
Hypernatremia
HYperosmolarity
Shifting of oxyhemoglobin curve to the left (ihibiting release of oxygen)
paradoxical acidosis from CO2 formation
Name 3 physiologic components which contribute to coronary resistance in the non-diseased heart
Auroregulatory resistance
Compressive resistance
viscous resistance
4 factors that results in a shift to the right of oxygen/hemoglobin dissociation curve
increase temp
increased PCO2
decrease in pH
increase in 2, 3 DPG
When an inotrope is administered, in which direction does the ESPVR slope shift
upward, leftward, rises more rapidly
IN the heart with systolic failure, in which direction does the ESPVR slope shift
downward, rightward, diminished rate of rise
List 4 physiologic changes associated with pregnancy that can complicate pre-existing cardiac disease
increase in cardiac output
increase in circulating blood volume
inferior vena caval compression from a gravid uterus with abrupt decrease in cardiac preload
increase in circulating elastase which may weaken the aortic media
hypercoagulable state with decrease protein S stasis and venous HTN
