Questions on cardiac anesthesia (powered by I. Bulatov)

[Igor Bulatov]

Which statement about inhaled anesthetics versus intravenous anesthetics as primary agents in fast-track cardiac anesthesia is MOST likely true?


A. Inhaled agents increase hospital length of stay.
B. Inhaled agents decrease intensive care unit (ICU) length of stay.
C. Intravenous agents decrease the length of postoperative ventilation.
D. Intravenous agents decrease the incidence of serious myocardial damage
=============================================

Which statement about postoperative shivering is MOST likely true?


A. Pharmacologic prophylaxis should be considered in patients with cardiovascular disease.
B. Postoperative shivering only occurs in hypothermic patients.
C. Clonidine is significantly more effective than meperidine at preventing postoperative shivering.
D. Pharmacologic prophylaxis of postoperative shivering is not effective.
================================================
Which statement about cellular physiology of the adrenergic receptor is MOST likely true?


A. The adrenergic receptor is a phospholipid.
B. All adrenergic receptor subtypes are components of the cell membrane.
C. The primary adrenergic messengers are phospholipids.
D. Alpha-adrenergic receptors are not found in the normal heart.
==============================================

Which statement about the perioperative adrenergic response is MOST likely true?


A. Release of inflammatory cytokines does not cause cardiovascular complications.
B. Perioperative use of oral clonidine, an alpha2-adrenergic agonist, has been shown to reduce the incidence of perioperative cardiac ischemic events.
C. In randomized controlled trials (RCTs), beta-adrenergic antagonists have not been shown to reduce the incidence of adverse perioperative cardiac events.
D. Beta-adrenergic antagonists primarily exert protective cardiovascular effects by decreasing centrally mediated sympathetic activity.
===============================================
Which statement about the role of autonomic nervous system modulation by regional anesthesia is MOST likely true?


A. Randomized clinical trials (RCTs) have shown that the incidence of adverse cardiac events is lower with regional anesthesia than with general anesthesia.
B. Cardiac arrest under spinal anesthesia is thought to occur due to sympatho-vagal imbalance.
C. Thoracic epidural anesthesia is associated with postoperative bowel dysfunction.
D. Hypotension during spinal anesthesia is primarily due to a decrease in systemic vascular resistance.
===============================================
Which statement about the occurrence of brain injury following adult cardiac surgery with cardiopulmonary bypass (CPB) is MOST likely true?


A. Stoke can cause a 10-fold increase in in-hospital mortality
B. Neuropsychological decline observed one week after the surgery is not predictive of the decline observed five years later.
C. Brain-specific creatine phosphokinase is useful for assessing the prognosis of brain injury.
D. Computed tomography (CT) scanning is more sensitive than magnetic resonance imaging (MRI) in diagnosing cerebral edema.
==============================================
Which statement about cerebral retrograde air embolization (CRAE) in adult patients from flushing arterial catheters is MOST likely true?


A. CRAE is a frequent event in hemodynamically stable adults.
B. Patients in shock are less likely to experience CRAE than stable patients.
C. Patients in a sitting position are less likely to experience CRAE than supine patients.
D. Patients with right radial arterial catheters are more likely to experience CRAE than patients with left radial arterial lines.

[Евгений Хоменко]

Which statement about inhaled anesthetics versus intravenous anesthetics as primary agents in fast-track cardiac anesthesia is MOST likely true?


A. Inhaled agents increase hospital length of stay.
B. Inhaled agents decrease intensive care unit (ICU) length of stay.
C. Intravenous agents decrease the length of postoperative ventilation.
D. Intravenous agents decrease the incidence of serious myocardial damage

B. Inhaled anesthetics decrease ICU length of stay, as well as length of postoperative ventilation and incidence of myocardial damage, but when comparing with etomidate propofol and remifentanyl answer B. is not quite suitable and С. could be the truth, I feel.
We use mainly Iso+fentanyl.

Which statement about postoperative shivering is MOST likely true?

A. Pharmacologic prophylaxis should be considered in patients with cardiovascular disease.
B. Postoperative shivering only occurs in hypothermic patients.
C. Clonidine is significantly more effective than meperidine at preventing postoperative shivering.
D. Pharmacologic prophylaxis of postoperative shivering is not effective.

I hesitate and in doubt between A. & B. D. is controversial because prophilaxis is somewhat not in use in comparison with treatment. Shivering IMO can occur not only in hypothermic patients, but they are the primary cohort.
So I would answer A.

Which statement about cellular physiology of the adrenergic receptor is MOST likely true?

A. The adrenergic receptor is a phospholipid.
B. All adrenergic receptor subtypes are components of the cell membrane.
C. The primary adrenergic messengers are phospholipids.
D. Alpha-adrenergic receptors are not found in the normal heart.

B. With no comments

Which statement about the perioperative adrenergic response is MOST likely true?

A. Release of inflammatory cytokines does not cause cardiovascular complications.
B. Perioperative use of oral clonidine, an alpha2-adrenergic agonist, has been shown to reduce the incidence of perioperative cardiac ischemic events.
C. In randomized controlled trials (RCTs), beta-adrenergic antagonists have not been shown to reduce the incidence of adverse perioperative cardiac events.
D. Beta-adrenergic antagonists primarily exert protective cardiovascular effects by decreasing centrally mediated sympathetic activity.

Surely B.

Which statement about the role of autonomic nervous system modulation by regional anesthesia is MOST likely true?

A. Randomized clinical trials (RCTs) have shown that the incidence of adverse cardiac events is lower with regional anesthesia than with general anesthesia.
B. Cardiac arrest under spinal anesthesia is thought to occur due to sympatho-vagal imbalance.
C. Thoracic epidural anesthesia is associated with postoperative bowel dysfunction.
D. Hypotension during spinal anesthesia is primarily due to a decrease in systemic vascular resistance.

May be D.

Which statement about the occurrence of brain injury following adult cardiac surgery with cardiopulmonary bypass (CPB) is MOST likely true?

A. Stoke can cause a 10-fold increase in in-hospital mortality
B. Neuropsychological decline observed one week after the surgery is not predictive of the decline observed five years later.
C. Brain-specific creatine phosphokinase is useful for assessing the prognosis of brain injury.
D. Computed tomography (CT) scanning is more sensitive than magnetic resonance imaging (MRI) in diagnosing cerebral edema.

Not sure for A. C. & D. bullshit. B. my second choice, but very very vague.

Which statement about cerebral retrograde air embolization (CRAE) in adult patients from flushing arterial catheters is MOST likely true?

A. CRAE is a frequent event in hemodynamically stable adults.
B. Patients in shock are less likely to experience CRAE than stable patients.
C. Patients in a sitting position are less likely to experience CRAE than supine patients.
D. Patients with right radial arterial catheters are more likely to experience CRAE than patients with left radial arterial lines.

D.

[Igor Bulatov]

Question 1


Compared to high-dose opioid techniques for coronary revascularization surgery, fast-track techniques are MOST likely to result in


A. worse respiratory outcomes.
B. increased length of hospital stay.
C. decreased duration of tracheal intubation.
D. increased intensive care unit (ICU) length of stay.




C is the best answer.




Discussion


It has been shown in the past decade that fast-track anesthesia techniques in patients undergoing coronary revascularization surgery can lower the use of resources by decreasing the length of intensive care unit (ICU) and hospital stays. This can be done without adversely affecting morbidity and mortality.

Fast-track techniques have also been shown to result in equivalent or better respiratory outcomes than high-dose opioid techniques, in part due to decreased duration of tracheal intubation. In the past, most of the anesthetic regimens for fast-track anesthesia consisted primarily of intravenous anesthetics with volatile agent supplementation. Although recent experimental data have shown that volatile agents may have cardioprotective effects due to myocardial preconditioning, these drugs have not been used as the main agent in most fast-track regimens. This is because of the clinical significance of reduction in myocardial contractility due to inhaled anesthetics in patients with impaired left ventricular function.


Reference


De Hert SG, Van der Linden PJ, Cromheecke S, et al. Choice of primary anesthetic regimen can influence intensive care unit length of stay after coronary surgery with cardiopulmonary bypass. Anesthesiology. 2004; 101:9-20.
Kaplan JA, Reich DL, Konstadt SN. Cardiac Anesthesia. 4th ed. Philadelphia: WB Saunders; 1999:705-708.

[Igor Bulatov]

Which statement about postoperative shivering is MOST likely true?


A. Pharmacologic prophylaxis should be considered in patients with cardiovascular disease.
B. Postoperative shivering only occurs in hypothermic patients.
C. Clonidine is significantly more effective than meperidine at preventing postoperative shivering.
D. Pharmacologic prophylaxis of postoperative shivering is not effective.




A is the best answer.




Discussion


Postoperative shivering is a frequent and potentially serious complication of anesthesia. Interestingly, this phenomenon occurs in normothermic as well as hypothermic patients. Shivering may increase oxygen consumption, intraocular and intracranial pressures, and incisional pain. Therefore, strategies aimed at preventing postoperative shivering and treating established shivering should be incorporated into an anesthetic plan. Although the etiology of this phenomenon remains to be elucidated, multiple nonpharmacologic and pharmacologic therapies focused at preventing and treating postoperative shivering have been developed. Unfortunately, the efficacy of these interventions is widely variable and the mechanisms of action poorly understood.

A recent systemic review of randomized controlled trials investigated the efficacy of prophylactic, single-dose, parenteral pharmacologic interventions aimed at preventing postoperative shivering compared to placebo or no treatment. Between 1980 and 2002, 27 randomized controlled trials met the inclusion criteria set forth by the investigators. In these trials, 1,348 patients received prophylactic pharmacologic interventions designed to prevent postoperative shivering (experimental group) and 931 patients received placebo or no treatment (control group). The median group size per trial was 30 patients (range 10-140). The average overall rate of shivering in the control group was 52%.

Clonidine was evaluated in 14 of the 27 trials and was administered to a total of 978 patients. The relative benefit for preventing shivering when compared to the control group was 1.58 and the number needed to treat (NNT) was 3.7. (Relative benefit is defined as the risk of not shivering with the active drug divided by the risk of not shivering with placebo or no treatment. The NNT is obtained by taking the inverse of the risk difference.) Meperidine was evaluated in five of 27 trials and included a total of 250 patients. The relative benefit was 1.67 and the NNT was 3.0 in order to preventing shivering compared to the control group. Tramadol was evaluated in three trials in a total of 250 patients. The relative benefit was 1.93 and the NNT was 2.2 compared to the control group.

Although data from these trials suggest extraordinary efficacy in preventing postoperative shivering with various single-dose pharmacologic interventions, the investigators advise us to use caution when interpreting the results of their review since the absolute measurement of treatment efficacy overestimates an intervention's usefulness when the event rate is high in the control group. Additional limitations of this investigation were related to the quality of the original trials (ie, size, methodology, etc).

Both pharmacologic prophylaxis of postoperative shivering and pharmacologic management of established postoperative shivering are effective. In fact, the NNT for established shivering with meperidine is less than that required for prophylaxis. The investigators do not advocate the use of prophylactic pharmacologic therapy to prevent postoperative shivering except in special circumstances (eg, patients with cardiovascular disease), citing that pharmacologic prophylaxis of postoperative shivering will expose patients to drugs unnecessarily as well as the adverse side effects that may accompany the administration of a particular agent.





Reference


Kranke P, Eberhart LH, Roewer N, et al. Single-dose parenteral pharmacological interventions for the prevention of postoperative shivering: A quantitative systemic review of randomized controlled trials. Anesth Analg. 2004; 99:718-727.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005: 391-392, 1582-1583.

[Igor Bulatov]

Which statement about cellular physiology of the adrenergic receptor is MOST likely true?


A. The adrenergic receptor is a phospholipid.
B. All adrenergic receptor subtypes are components of the cell membrane.
C. The primary adrenergic messengers are phospholipids.
D. Alpha-adrenergic receptors are not found in the normal heart.




B is the best answer.




Discussion


The autonomic nervous system exerts effects on all organ systems by central and peripheral actions. Alpha-adrenergic receptors are found in both the normal and diseased heart. Although positive and negative inotropic effects are associated with alpha-adrenergic receptor subtypes, especially in heart failure and cardiomyopathy, their functional role in the normal heart is not well defined. During the perioperative period, many homeostatic mechanisms rely on sympathetic reflex activity, and many anesthetic agents exert effects on the adrenergic system. Highlights of the adrenergic system include the following.

The regulation of contractile force (inotropy), heart rate, and vascular tone (blood supply) is controlled by a three-tier system:
rapid response of cardiac tissue to the mechanical load
regulation by humoral and cellular signal systems
long-term adaptation by changes in gene expression
There are nine human adrenergic receptor subtypes: alpha1A, alpha1B, alpha1D, alpha2A, alpha2B, alpha2C, beta1, beta2, and beta3.
These cell membrane receptors are single polypeptide chains (approximately 500 amino acids in length) and possess an extracellular component, a transmembrane component, and an intracellular component · All of them interact with guanine nucleotide-binding G-proteins and are therefore also referred to as G-protein–coupled receptors (GPCRs).
The cellular mechanisms by which adrenergic-receptor-induced signaling brings about the observed clinical effects are quite complicated, but many details have been elaborated in recent years. The following cascade of events is an extremely truncated summary of the many processes involved in adrenergic control and signaling.


Catecholamines are the primary adrenergic messengers. They bind to one or more of the nine adrenergic receptor subtypes (all of which are GPCRs).
Many subtypes of receptor-coupled G-proteins exist. Each subtype may interact with one or more adrenergic receptor subtype.
G-proteins activate enzymes such as adenylyl cyclase, phospholipase-C, nitric oxide synthase, guanylyl cyclase, and phosphoinositol-3-kinase.
Each of these enzymes can generate secondary messengers such as cyclic-AMP (by adenylyl cyclase), inositol triphosphate (by phospholipase-C), diacyl glycerol (also by phospholipase-C), reactive nitric oxide species (by nitric oxide synthase), cyclic-GMP (by guanylyl cyclase), and phosphoinositol-dependent-kinase-1 (by phosphoinositol-3-kinase).
Secondary messengers act via serine- and threonine-specific protein kinases to cause inotropic, lusitropic, hypertrophic, and other changes.

Moreover, adrenergic signaling systems interact with two other signaling systems: the global signaling system (involving cytokines and growth factors) and the calcium-signaling pathway (involving calmodulin, dihydropyridine receptors, ryanodine-binding receptors, calcium-binding inhibitory troponin, among others). Such overlaps allow redundancy and the ability to fine tune the necessary clinical control responses necessary for homeostasis. It is important for anesthesiologists to become familiar with the many advances being made in understanding the mechanisms by which adrenergic receptors exert their clinical effects.


Reference


Zaugg M, Schulz C, Wacker J, et al. Sympatho-modulatory therapies in perioperative medicine. Br J Anaesth. 2004; 93:53-62.
Zaugg M, Schaub MC. Cellular mechanisms in sympatho-modulation of the heart. Br J Anaesth. 2004; 93:34-52.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005:617-677.

[Igor Bulatov]

Which statement about the perioperative adrenergic response is MOST likely true?


A. Release of inflammatory cytokines does not cause cardiovascular complications.
B. Perioperative use of oral clonidine, an alpha2-adrenergic agonist, has been shown to reduce the incidence of perioperative cardiac ischemic events.
C. In randomized controlled trials (RCTs), beta-adrenergic antagonists have not been shown to reduce the incidence of adverse perioperative cardiac events.
D. Beta-adrenergic antagonists primarily exert protective cardiovascular effects by decreasing centrally mediated sympathetic activity.




B is the best answer.




Discussion


The sympathetic nervous system plays an important role in the adaptation to stress-many components of the "fright, fight, and flight" phenomenon involve the sympathetic nervous system. Recently, there is a growing appreciation that this response may also have adverse consequences, especially in individuals with ischemic heart disease.

During the perioperative period, clinicians can control the sympathetic nervous system to take advantage of the life-saving cardiovascular homeostatic processes while at the same time blunting the potentially harmful release of excess catecholamines and inflammatory mediators. While some change in sympathetic nervous system activity is essential in maintaining homeostasis, undue liberation of excitotoxic substances such as catecholamines and inflammatory cytokines can contribute to adverse cardiovascular events in the perioperative period. The benefits of beta-adrenergic blockade during the perioperative period have been described.

Acting indirectly, alpha2 agonists decrease catecholamine release and thus stress-induced tachycardia. They cause hypotension by lowering central sympathetic tone through activation of prejunctional alpha2A- adrenergic receptors. They can also produce analgesia, sedation, and anxiolysis. Postjunctional alpha2B-adrenergic receptors mediate the transient hypertensive response via Ca2+ channels in resistance vessels. A recent meta-analysis suggests that oral (but not intravenous) clonidine, an alpha2-agonist, successfully prevented perioperative myocardial ischemic events without increasing the risk of bradycardia. The study population had, or were at high risk of having, coronary disease. The procedures included cardiac and noncardiac surgeries. Another meta-analysis showed decreased cardiac morbidity when alpha2-agonists were administered to high-risk patients undergoing vascular and major surgery. Apart from these effects, alpha2-agonists also possess analgesic, antishivering, and sedative effects.

Unlike alpha2-agonists, beta-adrenergic antagonists mediate cardioprotective effects directly at the end-organ level. Protection is extended by five different mechanisms:

Decreasing stress-induced tachycardia
Lowering metabolic oxygen consumption by generating ATP from free fatty acids rather than glucose
Antidysrhythmic effects
Inhibition of beta-adrenergic-agonist–mediated cytotoxicity (altered gene expression, cell necrosis, apoptosis, and mechanical unloading)
Decreased protein phosphorylation, with resultant decreases in Ca2+ release during diastole
Selective inhibition of beta1-adrenergic receptors permits advantageous effects of unaltered beta2-adrenergic receptor stimulation, often resulting in improved hemodynamics. Specifically, such use has been shown to improve the inotropic response to beta2-adrenergic receptor stimulation. The selection of one specific beta-adrenergic antagonist over another depends on the clinical effects desired. An effect that beta-adrenergic antagonists share with clonidine is a reduction in baroreflex sensitivity in older hypertensive patients, resulting in more stable perioperative hemodynamics. Based on the evidence presented in two recent randomized controlled trials, the perioperative use of beta-adrenergic antagonists reduces cardiac morbidity and mortality. Conversely, beta-adrenergic antagonists are of limited use in patients with congestive heart failure with concurrent atrial fibrillation. Another consideration is that the localization of perioperative myocardial infarction is correlated to the site of coronary obstruction only in 50% of cases. Thus, preoperative invasive interventions (angioplasty, stenting, or revascularization) would not replace but rather complement perioperative beta-adrenergic antagonists. Whether or not statins could enhance the protection offered by perioperative beta-adrenergic antagonists is not known and requires additional investigation


Reference


Zaugg M, Schulz C, Wacker J, et al. Sympatho-modulatory therapies in perioperative medicine. Br J Anaesth. 2004; 93:53-62.
Zaugg M, Schaub MC. Cellular mechanisms in sympatho-modulation of the heart. Br J Anaesth. 2004; 93:34-52.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005:617-677.

[Igor Bulatov]

Which statement about the role of autonomic nervous system modulation by regional anesthesia is MOST likely true?


A. Randomized clinical trials (RCTs) have shown that the incidence of adverse cardiac events is lower with regional anesthesia than with general anesthesia.
B. Cardiac arrest under spinal anesthesia is thought to occur due to sympatho-vagal imbalance.
C. Thoracic epidural anesthesia is associated with postoperative bowel dysfunction.
D. Hypotension during spinal anesthesia is primarily due to a decrease in systemic vascular resistance.




B is the best answer.




Discussion


Although some meta-analyses claim that regional anesthesia is superior to general anesthesia with regard to cardiovascular and other major complications, most randomized controlled trials have not been able to validate these claims. Sympathetic blockade from neuraxial anesthesia differs from that obtained by pharmacological means in several ways. Levels above T1 decrease venous return and heart rate since the cardiac sympathetic drive is completely abolished. Hypotension is primarily a result of diminished venous return followed by a decreased cardiac output (-20%), and stroke volume (-25%). Systemic vascular resistance remains minimally affected (-5%). Although hypotension is less likely to occur when only lower spinal sympathetic segments are blocked, reflex compensatory mechanisms may decrease coronary blood flow and also result in wall motion abnormalities in susceptible patients. Selective blockade of thoracic spinal segments can increase the diameter of stenotic coronary arteries and even cause a redistribution of blood flow from epicardial to endocardial regions. It has also been shown to decrease ST-segment changes and the size of infarcted myocardium after coronary occlusion. Finally, thoracic sympathectomy has been shown to improve postischemic functional recovery, otherwise called myocardial stunning. Sympathetic block due to thoracic epidural anesthesia has been shown to help prevent bowel dysfunction and improve gastrointestinal recovery.

The incidence of cardiac arrest during spinal anesthesia is estimated to be 1:10,000. Risk factors include:

male sex
heart rate less than 60 beats/min
ASA physical status I
use of beta-adrenergic antagonists
age less than 50 years
sensory level above T6
Cardiac arrest is thought to occur mostly as a consequence of sympatho-vagal imbalance. Marked hypotension occurs in 30% of patients, and bradycardia is present in 15%. These cardiovascular effects may occur at any time during spinal anesthesia and may even develop several hours postoperatively.


Reference


Zaugg M, Schulz C, Wacker J, et al. Sympatho-modulatory therapies in perioperative medicine. Br J Anaesth. 2004; 93:53-62.
Zaugg M, Schaub MC. Cellular mechanisms in sympatho-modulation of the heart. Br J Anaesth. 2004; 93:34-52.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005:617-677.

[Igor Bulatov]

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Which statement about adult cardiac surgery using cardiopulmonary bypass is MOST likely true?


A. The incidence of stroke is less than 1% in patients over 75 years of age.
B. Hypertension is not an independent risk factor for new neurologic deficits.
C. Patients with internal carotid artery stenosis of greater than 50% account for 30% of the perioperative strokes.
D. Cognitive decline has been reported in 10% of patients one week after cardiac surgery.




C is the best answer.




Discussion


The incidence of postoperative neurological abnormality ranges from 0.4% to almost 80% depending on the study inclusion criteria. Complications are more common in the elderly, possibly because of the higher incidence of atherosclerosis and comorbid conditions. After coronary artery bypass graft (CABG) surgery using cardiopulmonary bypass, the incidence of stroke is less than 1% in patients 64 years old or younger, 5% in patients 65-74 years old, and 7%-9% in patients 75 years and older. Combined procedures (CABG and carotid) are associated with a higher incidence of stroke. The incidence of stroke after aortic arch surgery with deep hypothermic circulatory arrest is 1% for patients 60 years or younger and 21% for patients older than 60 years. In adult patients after deep hypothermic circulatory arrest, temporary neurological dysfunction may occur in 15%-19% of cases and permanent neurological injury in 9%.


Based on the clinical presentation, there are two types of postoperative brain injury after adult surgery:

Type 1 deficits or major neurologic change usually are identified on a routine physical exam (eg, stupor, coma, and focal neurological abnormalities)
Type 2 deficits or minor neurological or psychological change often requires specialized neuropsychological testing to define (eg, seizures without evidence of focal injury, deterioration of intellectual function or memory, confusion, or agitation)

The reported incidence of type 2 deficits is much higher than type 1 deficits. Accordingly, delirium or delayed awakening from surgery (with impairment of orientation, memory, intellectual function, and judgment) and emotional lability potentially lasting until the end of the first postoperative week have been reported in 13%-30% of cardiac cases. Cognitive decline consisting of deterioration of memory, attention, and motor speed has been reported in up to 60% of patients one week after undergoing cardiac operations, improving to 25%-30% of patients studied two months to one year after the procedure. In comparison, cognitive dysfunction has been reported in 10% of elderly patients three months after noncardiac surgery.


Independent risk factors for type 1 and type 2 deficits include advanced age (especially over 70 years) and presence or history of hypertension.


The strongest predictor of a type 1 deficit (most commonly stroke) is the presence of proximal aortic atherosclerosis. It is recommended that appropriate surgical technique modifications be implemented, Epi-aortic or transesophageal echocardiography is the most sensitive method to detect atheromatous disease of the ascending aorta. It also reduces the risk of emboli from aortic manipulation. When planning cardiopulmonary bypass in the presence of significant atherosclerosis (thickness of the ascending aortic wall greater than 3 mm), strategies should be used to avoid the plaques and prevent mobilization of atheromas including:

alternate cannulation sites such as subclavian or femoral
single cross clamp techniques
fibrillatory arrest without cross clamp
cardiac surgery on a beating heart
modification of the technique used to place the proximal anastomosis in the coronary artery bypass grafts
complete avoidance of proximal anastomosis with the use of all-arterial graft
replacement of the ascending aorta

Internal carotid artery stenosis of greater than 50% accounts for 30% of the perioperative strokes occurring a few days after cardiac surgery. Even asymptomatic carotid stenosis of 75% or more has been found to be an independent predictor of stroke. Preoperative screening may be justified for high-risk patients. Risk factors for stroke also include age greater than 65 years, previous transient ischemic attack or stroke, history of smoking, left main coronary artery disease, peripheral vascular disease, and female sex. Embolic stroke may occur when there is a preexisting intracardiac thrombus.


Other predictors of type 1 deficits include history of prior neurological disease, diabetes, use of intraaortic balloon pump, history of hypertension, history of unstable angina, and increasing age. Prior neurological disease and diabetes increase the incidence of type 1 brain injury following cardiac surgery; suggested mechanisms include metabolic changes, altered central nervous system autoregulation, and diffuse atherosclerosis. Use of an intraaortic balloon pump and intraoperative ventricular venting are also weakly associated with type 1 deficits.


Predictors of type 2 deficits include alcohol consumption, perioperative dysrhythmias, perioperative hypotension, prior CABG surgery, and coexisting peripheral vascular disease and/or congestive heart failure. This type 2 injury is believed to be from diffuse microemboli; consequently, aortic atherosclerosis does not seem to be a predictive factor. Type 2 deficits occur more often after periods of hypoperfusion or hypotension. Hyperglycemia and hypoglycemia may aggravate brain injury. It is not clear whether increased brain temperature, which can occur during aggressive rewarming, contributes to neuropsychological dysfunction.





Reference


Ahonen J, Salmenperä M. Brain injury after adult cardiac surgery. Acta Anaesthesiol Scand. 2004; 48:4-19.
Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: A report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery) American College of Cardiology Web Site. Available at: http://www.acc.org/clinical/guidelines/cabg/index.pdf. Accessed November 2005.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005:1158, 1061, 1941-2004.

[Igor Bulatov]

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Which statement about the occurrence of brain injury following adult cardiac surgery with cardiopulmonary bypass (CPB) is MOST likely true?


A. Stoke can cause a 10-fold increase in in-hospital mortality
B. Neuropsychological decline observed one week after the surgery is not predictive of the decline observed five years later.
C. Brain-specific creatine phosphokinase is useful for assessing the prognosis of brain injury.
D. Computed tomography (CT) scanning is more sensitive than magnetic resonance imaging (MRI) in diagnosing cerebral edema.




A is the best answer.




Discussion


The devastation and financial implications of a major postoperative brain injury may overshadow the cardiac results of any cardiac surgery. For example, a stroke can increase

in-hospital mortality 10-fold
length of hospital stay two- to threefold
likelihood of discharge to a nursing home sixfold
A perioperative stroke decreases one- and five-year survival rates after cardiac surgery by approximately 28% and 45%, respectively, when compared to patients who do not have a perioperative stroke. In addition, 70% of the stroke survivors suffer from moderate to severe long-term disability. Neuropsychological decline observed one week after the surgery is predictive of the decline observed five years later.

Neuropsychological tests are used for the diagnosis, evaluation, and follow-up of patients with cognitive changes after cardiac surgery. These tests include measures of motor and psychomotor speed, memory, attention, and visuo-constructional ability (ability to manipulate objects in space).
Several neurobiochemical markers are useful in diagnosing the extent and prognosis of brain injury. They include neuron-specific enolase, astroglial protein S100beta, brain-specific creatine phosphokinase, adenylate kinase, lactate dehydrogenase, glutamate, interleukin-6, and several adhesion molecules; all have been shown to be released from brain tissue and blood cells during injury. These markers are less sensitive in the setting of CPB because of confounding factors associated with surgery (eg, cardiotomy and tissue damage).

Magnetic resonance imaging (MRI) and computed tomography (CT) scans are also used in the diagnosis and follow-up of patients with brain injury. MRI is more sensitive than CT scan in the detection of ischemic lesions in the brain. Diffusion-weighted MRI can be used to differentiate old from recent ischemic areas. A brain MRI in patients immediately after heart surgery with CPB typically shows brain swelling that resolves within a few days after surgery while a brain MRI of cardiac surgery patients without CPB does not show brain swelling. The significance of this is unknown. Brain MRI scans after CPB may show spotty lesions that are believed to represent fat microemboli with associated edema and hemorrhage.





Reference


Ahonen J, Salmenperä M. Brain injury after adult cardiac surgery. Acta Anaesthesiol Scand. 2004; 48:4-19.
Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: A report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery) American College of Cardiology Web Site. Available at: http://www.acc.org/clinical/guidelines/cabg/index.pdf. Accessed November 2005.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005:1158, 1061, 1941-2004.

[Tsiklinskiy]

Игорь.
Во-первых, спасибо за информацию о результатах исследований, касающихся стентирования.
Во-вторых, если можно, опубликовывать ответы и комментарии не так быстро.
Ждём новых вопросов.
С уважением, Святослав.

[Igor Bulatov]

Which of the following preventative actions is LEAST effective in decreasing the incidence of ventilator-associated pneumonia?


A. Changing ventilator circuits every five days.
B. Use of noninvasive ventilation techniques rather than intubation.
C. Keeping the head of the patient's bed elevated to 45 degrees.
D. Appropriate nurse/patient ratio.
================================================
Which statement about postoperative atrial fibrillation after cardiac surgery is MOST likely true?


A. Advanced age is the most consistent predictor of postoperative atrial fibrillation.
B. Perioperative treatment with angiotensin-converting enzyme (ACE) inhibitors does not prevent postoperative atrial fibrillation.
C. Atrial fibrillation most commonly occurs on the fourth postoperative day.
D. Patients who experience postoperative atrial fibrillation are less likely to have recurrent episodes if they also have left ventricular hypertrophy.
=============================================
Which statement about fentanyl pharmacokinetics in patients undergoing coronary revascularization with cardiopulmonary bypass (CPB) is MOST likely true?


A. Separation from CPB results in no immediate change in plasma fentanyl concentration.
B. A simple three-compartment model cannot adequately describe plasma fentanyl concentration when CPB is used.
C. Plasma fentanyl concentration at the conclusion of surgery is not significantly affected by the use of CPB.
D. There is a small tissue reservoir for fentanyl.

[Евгений Хоменко]

Which of the following preventative actions is LEAST effective in decreasing the incidence of ventilator-associated pneumonia?

A. Changing ventilator circuits every five days.
B. Use of noninvasive ventilation techniques rather than intubation.
C. Keeping the head of the patient's bed elevated to 45 degrees.
D. Appropriate nurse/patient ratio.

C. Keeping head of the patients bed elevated doesn't always mean keeping the patients head elevated, especially when the patient/nurse ratio counts 4/1

Which statement about postoperative atrial fibrillation after cardiac surgery is MOST likely true?

A. Advanced age is the most consistent predictor of postoperative atrial fibrillation.
B. Perioperative treatment with angiotensin-converting enzyme (ACE) inhibitors does not prevent postoperative atrial fibrillation.
C. Atrial fibrillation most commonly occurs on the fourth postoperative day.
D. Patients who experience postoperative atrial fibrillation are less likely to have recurrent episodes if they also have left ventricular hypertrophy.

A. ACE inhibitors could probably influence the incidence of postoperative atrial fibrillation because of the remodeling of the myocardium. Atrial fib occurs on the any postoperative day. D. is anecdote.

Which statement about fentanyl pharmacokinetics in patients undergoing coronary revascularization with cardiopulmonary bypass (CPB) is MOST likely true?

A. Separation from CPB results in no immediate change in plasma fentanyl concentration.
B. A simple three-compartment model cannot adequately describe plasma fentanyl concentration when CPB is used.
C. Plasma fentanyl concentration at the conclusion of surgery is not significantly affected by the use of CPB.
D. There is a small tissue reservoir for fentanyl.

B. Separation from CPB results in acute rise in FEN concentration due to FEN released from pulmonary circulation, where it was stored during CPB. Consequently, FEN concentration after CPB would be probably higher at the conclusion of the surgery versus the FEN concentration after surgery off pump. Tissue reservoir for FEN is quite large due to its lipophilic structure.

[Tsiklinskiy]

1. Сохранение головной части кровоти приподнятой на 45 гр. - профилактирует возникновение пневмоний, связанных с вентиляцией. Поэтому я за "А".
В остальном согласен с комментариями Евгения: 2. "А" и 3. "В"

[Igor Bulatov]

Which statement about postoperative atrial fibrillation after cardiac surgery is MOST likely true?


A. Advanced age is the most consistent predictor of postoperative atrial fibrillation.
B. Perioperative treatment with angiotensin-converting enzyme (ACE) inhibitors does not prevent postoperative atrial fibrillation.
C. Atrial fibrillation most commonly occurs on the fourth postoperative day.
D. Patients who experience postoperative atrial fibrillation are less likely to have recurrent episodes if they also have left ventricular hypertrophy.




A is the best answer.




Discussion


Postoperative atrial fibrillation is a well-recognized complication after cardiac surgery, with a reported incidence of 27%-40%. The Ischemia Research and Education Foundation and the Multicenter Study of Perioperative Ischemia Research Group recently published a large (5,436 patients), multicenter (70 hospitals in 17 countries), prospective longitudinal study of patients undergoing coronary artery bypass (CABG) surgery with or without valve replacement/repair using cardiopulmonary bypass. This study reported an incidence of postoperative atrial fibrillation of 32.3%. The initial occurrence was most commonly on postoperative day two and most recurrent episodes occurred on postoperative day three (Table 1).

Table 1. Demographic characteristics. Used with permission, from Mathew JP, Fontes ML, Tudor IC, et al. A multicenter risk index for atrial fibrillation after cardiac surgery. JAMA. 2004; 291:1720-1729.



Postoperative atrial fibrillation was associated with cognitive changes, renal dysfunction, increased infection rate, and increased length of stay in both the intensive care unit (ICU) and the hospital. Once discharged from the ICU, patients with atrial fibrillation were more likely to return to the ICU. Patients with atrial fibrillation experienced a greater level of radiologic and ultrasound testing and were also more likely to be discharged to an extended care facility than patients without atrial fibrillation were.

Advanced age was the most consistent predictor of postoperative atrial fibrillation and any patient over the age of 70 was considered to be at high risk. Other factors associated with postoperative atrial fibrillation were prior history of atrial fibrillation or chronic obstructive pulmonary disease, valve surgery, and postoperative withdrawal of either beta-blocker or angiotensin-converting enzyme (ACE) inhibitor therapy. Conversely, reduced risk of atrial fibrillation was associated with postoperative administration of beta-blockers, potassium supplementation, and nonsteroidal antiinflammatory drugs as well as pre- and postoperative ACE inhibitor therapy.

Forty-three percent of patients who experienced postoperative atrial fibrillation had more than one episode. Predictors of recurrent atrial fibrillation included older age, history of congestive heart failure, left ventricular hypertrophy, aortic atherosclerosis, bicaval cannulation, withdrawal of beta-blocker or ACE inhibitor therapy, and use of amiodarone or digoxin.






Reference


Mathew JP, Fontes ML, Tudor IC, et al. A multicenter risk index for atrial fibrillation after cardiac surgery. JAMA. 2004; 291:1720-1729.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005:1993.

[Igor Bulatov]

Which statement about fentanyl pharmacokinetics in patients undergoing coronary revascularization with cardiopulmonary bypass (CPB) is MOST likely true?


A. Separation from CPB results in no immediate change in plasma fentanyl concentration.
B. A simple three-compartment model cannot adequately describe plasma fentanyl concentration when CPB is used.
C. Plasma fentanyl concentration at the conclusion of surgery is not significantly affected by the use of CPB.
D. There is a small tissue reservoir for fentanyl.




C is the best answer.




Discussion


In recent years, there has been a trend towards early postoperative tracheal extubation in patients undergoing cardiac surgery. This is particularly a consideration in patients undergoing minimally invasive cardiac procedures. In order to extubate these patients successfully, it is important to achieve suitable plasma concentrations of short-acting opioids commonly administered during cardiac surgery. Determining the magnitude of pharmacokinetic changes brought about by cardiopulmonary bypass (CPB) would be very useful in achieving this goal.

Recently, the authors of a study of plasma concentrations of fentanyl before, during, and after CPB in patients undergoing coronary revascularization sought to determine whether or not CPB affected the pharmacokinetics of fentanyl. The investigators measured total fentanyl concentrations and did not assess changes in bound and free fractions.

During the investigation, using data from patients undergoing coronary revascularization with CPB, the authors compared a simple three-compartment model with models adjusted for covariates (gender, weight, and premedication) and also with 18 models adjusted for CPB. They found that their simple three-compartment model was as good or better at predicting plasma fentanyl concentration than covariate-adjusted or bypass-adjusted models. Later in the study, these authors prospectively evaluated the predictive ability of this simple model in estimating plasma fentanyl concentration before, during, and after CPB. They found a 25% decrease in plasma fentanyl concentration five minutes after onset of CPB. This is believed to occur as a result of dilution by the priming solution. Interestingly, the investigators observed a 25% increase in plasma fentanyl concentration just after separation from CPB. This is believed to be mostly a result of release of the drug from pulmonary sequestration prior to bypass. At the conclusion of surgery, plasma concentrations of fentanyl were within 7% of target levels. The authors concluded that the overall effect of CPB on fentanyl concentrations was not significant. The large capacity of tissues to take up fentanyl, a highly lipophilic drug, creates an extensive reservoir that resists significant changes in plasma concentration when surgery is completed.

In summary, although initiation of CPB results in a decrease in plasma fentanyl concentration and separation from CPB results in an increase in plasma fentanyl concentration, these changes are brief and clinically insignificant by the time surgery is concluded.





Reference


Hudson RJ, Thomson IR, Jassal R, et al. Cardiopulmonary bypass has minimal effects on the pharmacokinetics of fentanyl in adults. Anesthesiology. 2003; 99:847-854.
Hudson RJ, Thomson IR, Henderson BT, et al. Validation of fentanyl pharmacokinetics in patients undergoing coronary artery bypass grafting. Can J Anaesth. 2002; 49:388-392.
Miller RD. Miller's Anesthesia. 6th ed. Philadelphia: Elsevier Churchill Livingstone; 2005: 408-409, 439-480.