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3. The Donabedian model of measuring quality identi-
CHAPTER 12
fies all of the following as main types of improvements
EXCEPT:
A. Changes to structure
B. Changes to process
C. Changes to culture
D. Changes to outcomes
Patient Safety
4. Surgical Care Improvement Project (SCIP) Measures
include:
A. Process of care performance measures and outcome
measures.
B. The training of surgeons and staff.
C. How surgeons document in operative reports.
D. Operating room turnover.
Answer: C
The Donabedian model of measuring quality identifies three
main types of improvements: changes to organizational structure, changes in organizational processes, and changes in
outcomes. Structure refers to the physical and organizational
tools, equipment, and policies that improve safety. Structural
measures ask, “Do the right tools, equipment, and policies
exist?” Process is the application of these tools, equipment, and
policies/procedures to patients (good practices and evidencebased medicine). Process measures ask, “Are the right tools,
policies, and equipment being used?” Outcome is the result
on patients. Outcome measures ask, “How often are patients
harmed?” In this model, structure (how care is organized)
plus process (what we do) influences patient outcomes (the
results achieved). (See Schwartz 11th ed., p. 399.)
Answer: A
SCIP has identified three broad areas within surgery where
potential complications have a high incidence and cost and
there is a significant opportunity for prevention: surgical site
infections (SSIs), venous thromboembolism, and adverse cardiac events. The SCIP measures aim to reduce the incidence
of these events during the perioperative period by advocating
the use of proven process and outcome measures. These process and outcome measures are detailed in Table 12-1. (See
Schwartz 11th ed., p. 407.)
TABLE 12-1 The Surgical Care Improvement Project
measures
Process of care performance measures
Infection
• Prophylactic antibiotic received within 1 h before surgical incision
• Prophylactic antibiotic selection for surgical patients
• Prophylactic antibiotics discontinued within 24 h after surgery end
time (48 h for cardiac patients)
• Cardiac surgery patients with controlled 6 a.m. postoperative serum
glucose
• Surgery patients with appropriate hair removal
• Colorectal surgery patients with immediate postoperative
normothermia
Venous thromboembolism
• Surgery patients with recommended venous thromboembolism
prophylaxis ordered
• Surgery patients who received appropriate venous thromboembolism
prophylaxis within 24 h before surgery to 24 h after surgery
Cardiac events
• Surgery patients on a β-blocker prior to arrival who received a β-blocker
during the perioperative period
Proposed outcome measures
Infection
• Postoperative wound infection diagnosed during index hospitalization
Venous thromboembolism
• Intra- or postoperative pulmonary embolism diagnosed during index
hospitalization and within 30 d of surgery
• Intra- or postoperative deep vein thrombosis diagnosed during index
hospitalization and within 30 d of surgery
Cardiac events
• Intra- or postoperative acute myocardial infarction diagnosed during
index hospitalization and within 30 d of surgery
Global measures
• Mortality within 30 d of surgery
• Readmission within 30 d of surgery
Data from The Joint Commission, 2012.
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5. National Surgical Quality Improvement Program:
A. Is essentially the same as Surgical Care Improvement
Project (SCIP).
B. Collects data on individual surgeon outcomes.
C. Was created by the Institute of Medicine.
D. Allows hospitals to compare their rates of postopera-
tive events and compare them to similar hospitals.
6. The root cause of the majority of wrong-site surgeries
results from:
A. Communication errors.
B. Emergency surgery.
C. Multiple procedures.
D. Multiple surgeons.
Answer: D
The National Surgical Quality Improvement Program
(NSQIP) is a measurement program that allows hospitals to
sample their rates of postoperative events and compare them
to similar hospitals. Created by the Veterans Health Administration (VA) in 1991, NSQIP has been credited with measuring and improving morbidity and mortality outcomes at
the VA, reducing 30-day mortality rate after major surgery by
31%, and 30-day postoperative morbidity by 45% in its first
decade. Beta testing at 18 non-VA sites from 2001 to 2004
demonstrated the feasibility and utility of the program in the
private sector. The program was subsequently expanded to
the private sector in 2004. (See Schwartz 11th ed., p. 407.)
Answer: A
The risk of performing wrong-site surgery increases when
there are multiple surgeons involved in the same operation
or multiple procedures are performed on the same patient,
especially if the procedures are scheduled or performed on
different areas of the body. Time pressure, emergency surgery, abnormal patient anatomy, and morbid obesity are also
thought to be risk factors. Communication errors are the root
cause in more than 70% of the wrong-site surgeries reported
to The Joint Commission. Other risk factors include receiving
an incomplete preoperative assessment; having inadequate
procedures in place to verify the correct surgical site; or having an organizational culture that lacks teamwork or reveres
the surgeon as someone whose judgment should never be
questioned. (See Schwartz 11th ed., p. 411.)
CHAPTER 12
Patient Safety
7. Retained surgical items:
A. Occur in approximately 1:1500 surgeries in the
United States.
B. Occur more frequently in elective procedures.
C. Are less likely to occur when multiple surgeons take
part in an operation.
D. Are most frequently surgical needles.
Answer: A
A retained surgical item refers to any surgical item found to
be inside a patient after he or she has left the operating room
(OR), thus requiring a second operation to remove the item.
Estimates of retained foreign bodies in surgical procedures
range from one case per 8000 to 18,000 operations, corresponding to one case or more each year for a typical large
hospital or approximately 1500 cases per year in the United
States. This estimate is based on an analysis of malpractice
claims and is likely to underestimate the true incidence. The
risk of having a retained surgical item increases during emergency surgery, when there are unplanned changes in procedure (due to new diagnoses encountered in the OR), and
in patients with higher body mass index (Table 12-2). (See
Schwartz 11th ed., p. 410.)
TABLE 12-2 Risk factors for retained surgical sponges
• Emergency surgery
• Unplanned changes in procedure
• Patient with higher body mass index
• Multiple surgeons involved in same operation
• Multiple procedures performed on same patient
• Involvement of multiple operating room nurses/staff members
• Case duration covers multiple nursing “shifts”
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8. Regarding complications of Central lines:
CHAPTER 12
A. Pneumothorax occurs in 10%.
B. Pneumothorax is eliminated using ultrasound when
placing the line.
C. Central line infections are associated with significant
mortality and increased hospital costs.
D. Frequent line changes are recommended to decrease
Patient Safety
9. Laryngoscopic findings after a superior laryngeal nerve
infection risk.
injury include:
A. Ipsilateral vocal cord in a paramedian position.
B. Ipsilateral vocal cord in a middling position.
C. Asymmetry of the glottic opening.
D. Normal examination.
Answer: C
Pneumothorax occurrence rates from both subclavian and
internal jugular vein approaches are 1% to 6%. Prevention
requires proper positioning of the patient and correct insertion technique. A postprocedure chest X-ray is recommended
to confirm the presence or absence of a pneumothorax,
regardless of whether a pneumothorax is suspected. Recent
reports have questioned whether a chest X-ray is required
when the line is placed and confirmed under ultrasound
guidance. Pneumothorax rates are higher among inexperienced providers and underweight patients but occur with
experienced operators as well.
The Centers for Disease Control and Prevention (CDC)
reports mortality rates of 12% to 25% when a central venous
line infection becomes systemic, with a cost of approximately
$25,000 per episode. The CDC does not recommend routine
central line changes, but when the clinical suspicion of infection is high, the site of venous access must be changed. (See
Schwartz 11th ed., p. 416.)
Answer: C
Superior laryngeal nerve injury is less debilitating, as the common symptom is loss of projection of the voice. The glottis
aperture is asymmetrical on direct laryngoscopy, and management is limited to clinical observation. (See Schwartz 11th ed.,
p. 419.)
10. Ventilator-associated pneumonia (VAP) in ventilated
ICU patients reaches a 70% probability at:
A. 5 days.
B. 15 days.
C. 30 days.
D. 45 days.
11. Included in the definition of acute respiratory distress
syndrome (ARDS) is:
A. Required increased positive end-expiratory pressure
(PEEP).
B. PaO2:FiO2 < 200 regardless of PEEP.
C. Cardiac failure.
D. Respiratory failure despite normal chest X-ray.
Answer: C
Pneumonia is the second most common nosocomial infection and is the most common infection in ventilated patients.
VAP occurs in 15% to 40% of ventilated ICU patients, with
a probability rate of 5% per day, up to 70% at 30 days. The
30-day mortality rate of nosocomial pneumonia can be as
high as 40% and depends on the microorganisms involved
and the timeliness of initiating appropriate antimicrobials
Protocol-driven approaches for prevention and treatment of
VAP are recognized as beneficial in managing these difficult
infectious complications. (See Schwartz 11th ed., p. 419.)
Answer: B
The Berlin definition of ARDS developed by the AmericanEuropean Consensus Conference of 2012 not only simplifies
the definition of ARDS but also eliminates the term Acute
Lung Injury (ALI) from critical care vernacular. ARDS is
now classified by partial pressure of oxygen in arterial blood
(PaO2)/fraction of inspired oxygen (Fio2) ratios as mild
(300–201 mmHg), moderate (200–101 mmHg), and severe
(<100 mmHg). Elements of modification of the definition
include the following: <7 days of onset; removal of pulmonary artery occlusion pressure; and clinical judgment for
characterizing hydrostatic pulmonary edema is acceptable,
unless risk factors for ARDS have been eliminated, in which
case objective analysis is necessary.
The definition of ARDS traditionally included five criteria (Table 12-3). The multicenter ARDS Research Network
(ARDSnet) research trial demonstrated improved clinical
outcomes for ARDS patients ventilated at tidal volumes of
only 5 to 7 mL/kg. This strategy is no longer prescribed solely
for patients with ARDS but is also recommended for patients
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12. Clinical signs of pulmonary embolism include:
A. Hypocarbia.
B. Hypoxemia.
C. Right heart strain on electrocardiogram (ECG).
D. All of the above.
13 Tracheostomy may facilitate weaning, and improve
patient comfort and pulmonary toilet. Tracheostomy
should be performed:
A. Open tracheostomy before the fifth day of ventilator
support.
B. Percutaneous tracheostomy before the 10th day of
ventilator support.
C. Before the 15th day of ventilator support.
D. There is no difference between early <3–7 days vs late
>14 days tracheostomy.
with normal pulmonary physiology who are intubated for
reasons other than acute respiratory failure. The beneficial
effects of PEEP for ARDS were confirmed in this study as
well. (See Schwartz 11th ed., p. 420.)
TABLE 12-3 Inclusion criteria for the acute respiratory
distress syndrome
• Acute onset
• Predisposing condition
• Pao2:Fio2 <200 (regardless of positive end-expiratory pressure)
• Bilateral infiltrates
• Pulmonary artery occlusion pressure <18 mm Hg
• No clinical evidence of right heart failure
Fio2 = fraction of inspired oxygen; Pao2 = partial pressure of arterial oxygen.
Answer: D
Clinical findings include elevated central venous pressure,
hypoxemia, shortness of breath, hypocarbia secondary to
tachypnea, and right heart strain on ECG. (See Schwartz
11th ed., p. 420.)
Answer: D
Tracheostomy facilitates weaning from a ventilator, may
decrease length of ICU or hospital stay, and improves pulmonary toilet. Tracheostomies are performed open, percutaneously, with or without bronchoscopy, and with or without
Doppler guidance. The advantages of percutaneous tracheostomy include efficiency and cost containment over open tracheostomy. A recent literature review examining early (<3–7 days)
vs late (>14 days) tracheostomy after endotracheal intubation
demonstrates little difference in outcomes but does demonstrate greater patient comfort in those patients with tracheostomy than those with an endotracheal tube. Complications
and outcomes between the two different methods remain
largely equivalent. (See Schwartz 11th ed., p. 417.)
CHAPTER 12
Patient Safety
14. Which of the following have been shown to decrease the
time of postoperative ileus?
A. Cyclooxygenase-1 inhibitors
B. Morphine patient-controlled analgesia
C. Nasogastric drainage until full return of bowel
function
D. Alvimopan, a μ -opioid receptor antagonist
Answer: D
Postoperative ileus is related to dysfunction of the neural reflex
axis of the intestine. Excessive narcotic use may delay return
of bowel function. Epidural anesthesia results in better pain
control, and there is an earlier return of bowel function and
a shorter length of hospital stay. The limited use of nasogastric tubes and the initiation of early postoperative feeding are
associated with an earlier return of bowel function. The use
of chewing gum and other oral stimulants to minimize ileus
remains controversial. Pharmacologic agents commonly used
to stimulate bowel function include metoclopramide and
erythromycin. Metoclopramide’s action is limited to the stomach and duodenum, and it may help primarily with gastroparesis. Erythromycin is a motilin agonist that works throughout
the stomach and bowel. Several studies demonstrate significant
benefit from the administration of erythromycin in those suffering from an ileus. Alvimopan, a newer agent and a μ-opioid
receptor antagonist, has shown some promise in many studies
for earlier return of gut function and subsequent reduction in
length of stay. Neostigmine has been used in refractory panileus patients (Ogilvie’s syndrome) with some degree of success.
It is recommended for patients receiving this type of therapy to
be in a monitored unit. (See Schwartz 11th ed., p. 421.)
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15. The treatment of choice for a biloma after laparoscopic
CHAPTER 12
cholecystectomy is:
A. Reoperation, closure of the leak, and drainage.
B. Percutaneous drainage.
C. Biliary stent.
D. Observation.
Patient Safety
Answer: C
Complications involving the hepatobiliary system are usually
due to technical errors. Laparoscopic cholecystectomy has
become the standard of care for cholecystectomy, but common bile duct injury remains a nemesis of this approach.
Intraoperative cholangiography has not been shown to
decrease the incidence of common bile duct injuries because
the injury to the bile duct usually occurs before the cholangiogram. Early recognition and immediate repair of an injury
are important because delayed bile duct leaks often require a
more complex repair.
Ischemic injury due to devascularization of the common
bile duct has a delayed presentation days to weeks after an
operation. Endoscopic retrograde cholangiopancreatography
(ERCP) demonstrates a stenotic, smooth common bile duct,
and liver function studies are elevated. The recommended
treatment is a Roux-en-Y hepaticojejunostomy.
A bile leak due to an unrecognized injury to the ducts may
present after cholecystectomy as a biloma. These patients
may present with abdominal pain and hyperbilirubinemia.
The diagnosis of a biliary leak can be confirmed by CT scan,
ERCP, or radionuclide scan. Once a leak is confirmed, a retrograde biliary stent and external drainage are the treatment
of choice. (See Schwartz 11th ed., p. 422.)
16. All of the following are TRUE statements regarding
wound infection EXCEPT:
A. Irrigation of the operative field and surgical wound
with antibiotic solution is not better than using saline
alone.
B. Prophylactic use of antibiotics continued beyond 48
hours is beneficial.
C. Irrigation with an antibiotic-based solution has not
been shown to be beneficial.
D. Antibacterial-impregnated polyvinyl placed over the
operative wound area for the duration of the surgical
procedure is not beneficial.
17. The most common cause of an empyema in the postoperative patient is:
A. Pneumonia.
B. Systemic sepsis.
C. Esophageal perforation.
D. Retained hemothorax.
Answer: B
No prospective, randomized, double-blind, controlled studies exist that demonstrate antibiotics used beyond 24 hours
in the perioperative period prevent infections. Prophylactic
use of antibiotics should simply not be continued beyond this
time. Irrigation of the operative field and the surgical wound
with saline solution has shown benefit in controlling wound
inoculum. Irrigation with an antibiotic-based solution has
not demonstrated significant benefit in controlling postoperative infection.
Antibacterial-impregnated polyvinyl placed over the operative wound area for the duration of the surgical procedure
has not been shown to decrease the rate of wound infection. Although skin preparation with 70% isopropyl alcohol
has the best bactericidal effect, it is flammable and could be
hazardous when electrocautery is used. The contemporary
formulas of chlorhexidine gluconate with isopropyl alcohol
remain more advantageous. (See Schwartz 11th ed., p. 424.)
Answer: A
One of the most debilitating infections is an empyema, or
infection of the pleural space. Frequently, an overwhelming pneumonia is the source of an empyema, but a retained
hemothorax, systemic sepsis, esophageal perforation from
any cause, and infections with a predilection for the lung
(eg, tuberculosis) are potential etiologies as well. The diagnosis is confirmed by chest X-ray or CT scan, followed by
aspiration of pleural fluid for bacteriologic analysis. Gram’s
stain, lactate dehydrogenase, protein, pH, and cell count
are obtained, and broad-spectrum antibiotics are initiated
while the laboratory studies are performed. Once the specific
organisms are confirmed, anti-infective agents are tailored
appropriately. Placement of a thoracostomy tube is needed to
evacuate and drain the infected pleural fluid, but depending
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18. The primary cause of hyperbilirubinemia in the surgical
patient is:
A. Sepsis.
B. Hematoma from trauma.
C. Cholestasis.
D. Increased unconjugated bilirubin due to hemolysis.
19. A patient after a laparotomy for a perforated viscus is
noted to develop abdominal distention, increased peak
airway pressure, oliguria. Bladder pressure is 23 mm Hg.
Appropriate next step is:
A. Reopen a laparotomy incision.
B. Diuresis.
C. Institute positive end-expiratory pressure (PEEP).
D. Rectal tube.
on the specific nidus of infection, video-assisted thoracoscopy may also be helpful for irrigation and drainage of the
infection. Refractory empyemas require specialized surgical
approaches. (See Schwartz 11th ed., p. 425.)
Answer: C
Hyperbilirubinemia in the surgical patient can be a complex
problem. Cholestasis makes up the majority of causes for
hyperbilirubinemia, but other mechanisms of hyperbilirubinemia include reabsorption of blood (eg, hematoma from
trauma), decreased bile excretion (eg, sepsis), increased
unconjugated bilirubin due to hemolysis, hyperthyroidism,
and impaired excretion due to congenital abnormalities
or acquired disease. Errors in surgery that cause hyperbilirubinemia largely involve missed or iatrogenic injuries.
(See Schwartz 11th ed., p. 422.)
Answer: A
The treatment of abdominal compartment syndrome (ACS) is
to open any recent abdominal incision to release the abdominal fascia or to open the fascia directly if no abdominal
incision is present. Immediate improvement in mechanical
ventilation pressures, intracranial pressures, and urine output is usually noted. When expectant management for ACS is
considered in the operating room (OR), the abdominal fascia
should be left open and covered under sterile conditions (eg,
a vacuum-assisted open abdominal wound closure system)
with plans made for a second-look operation and delayed
fascial closure. Patients with intra-abdominal hypertension
should be monitored closely with repeated examinations
and measurements of bladder pressure, so that any further
deterioration is detected and operative management can be
initiated. Left untreated, ACS may lead to multiple system
end-organ dysfunction or failure and has a high mortality.
(See Schwartz 11th ed., p. 423.)
CHAPTER 12
Patient Safety
20. Retained surgical items:
A. Occur in approximately 1:1500 surgeries in the
United States.
B. Occur more frequently in elective procedures.
C. Are less likely to occur when multiple surgeons take
part in an operation.
D. Are most frequently surgical needles.
Answer: A
A retained surgical item refers to any surgical item found to
be inside a patient after he or she has left the operating room
(OR), thus requiring a second operation to remove the item.
Estimates of retained foreign bodies in surgical procedures
range from one case per 8000 to 18,000 operations, corresponding to one case or more each year for a typical large hospital
or approximately 1500 cases per year in the United States.
This estimate is based on an analysis of malpractice claims
and is likely to underestimate the true incidence. The risk of
having a retained surgical item increases during emergency
surgery, when there are unplanned changes in procedure (due
to new diagnoses encountered in the OR), and in patients with
higher body mass index (Table 12-2). (See Schwartz 11th ed.,
p. 410.)
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CHAPTER 13
Oxygen utilization, VO
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Physiologic Monitoring of the Surgical Patient
1. Which of the following is NOT TRUE regarding VO2
(oxygen utilization) and DO2 (oxygen delivery)?
A. The region where the two lines intersect is DO
2crit
and
represents the transition from supply-independent
uptake to supply-dependent uptake.
B. At lower DO2, VO2 is dependent on DO2.
C. At higher DO2, VO2 is independent of DO2.
D. Below a critical threshold of oxygen delivery,
increased oxygen extraction can compensate for the
oxygen delivery deficit.
Answer: D
The relationship of VO2 to DO2 over a broad range of DO2
values is commonly represented as two intersecting straight
lines (Fig. 13-1). In the region of higher DO2 values, the slope
of the line is approximately equal to zero, indicating that VO2
is largely independent of DO2. In contrast, in the region of
low DO2 values, the slope of the line is nonzero and positive,
indicating that VO2 is supply-dependent. The region where
the two lines intersect is called the point of critical oxygen
delivery (DO
), and represents the transition from supply-
2crit
independent to supply-dependent oxygen uptake. Below
a critical threshold of oxygen delivery, increased oxygen
extraction cannot compensate for the delivery deficit; hence,
oxygen consumption begins to decrease. The slope of the
supply- dependent region of the plot reflects the maximal
oxygen extraction capability of the vascular bed being evaluated. (See Schwartz 11th ed., p. 440.)
Supply-dependent
oxygen consumption
2
Supply-independent
oxygen consumption
FIG. 13-1. Graphical representation of the relationship between
oxygen utilization (VO2) and oxygen delivery (DO2). Under most
normal physiologic conditions, oxygen utilization does not
depend on oxygen delivery, but below the critical value DO
oxygen utilization decreases linearly as a function of oxygen
delivery, rendering tissues susceptible to ischemic injury.
2crit
Tissue hypoxia
Oxygen delivery, DO
2crit
Tissue normoxia
DO
2
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2. Of the following parameters, which is the least influ-
CHAPTER 13
enced by an underdamped or overdamped intra-arterial
blood pressure monitoring system?
A. Systolic blood pressure
B. Mean arterial blood pressure
C. Diastolic blood pressure
D. Pulse pressure
Physiologic Monitoring of the Surgical Patient
3. Regarding electrocardiographic monitoring in the ICU:
A. A standard 3-lead electrocardiogram (ECG) will
detect 95% of ischemia, whereas a 12-lead ECG will
detect >98%.
B. Lead V4 is the most sensitive for detecting periopera-
tive ischemia.
C. A standard 3-lead ECG will detect ischemia at the
same rate as a 12-lead ECG, however it is inferior at
identifying dysrhythmias.
D. Lead V2 is the most sensitive for detecting periopera-
tive ischemia.
Answer: B
If the system is underdamped, then the inertia of the system,
which is a function of the mass of the fluid in the tubing and
the mass of the diaphragm, causes overshoot of the points
of maximum positive and negative displacement of the diaphragm during systole and diastole, respectively. Thus, in an
underdamped system, systolic pressure will be overestimated
and diastolic pressure will be underestimated. In an overdamped system, displacement of the diaphragm fails to track
the rapidly changing pressure waveform, and systolic pressure
will be underestimated and diastolic pressure will be overestimated. It is important to note that even in an underdamped
or overdamped system, mean pressure will be accurately
recorded, provided the system has been properly calibrated.
For these reasons, when using direct measurement of intraarterial pressure to monitor patients, clinicians should make
clinical decisions based primarily on the measured mean
arterial blood pressure. (See Schwartz 11th ed., p. 435.)
Answer: B
Continuous monitoring of the 12-lead ECG may be beneficial
in certain patient populations. In a study of 185 vascular surgical patients, continuous 12-lead ECG monitoring was able to
detect transient myocardial ischemic episodes in 20.5% of the
patients. This study demonstrated that the precordial lead V4,
which is not routinely monitored on a standard 3-lead ECG,
is the most sensitive for detecting perioperative ischemia and
infarction. To detect 95% of the ischemic episodes, two or
more precordial leads were necessary. Furthermore, in a prospective observational study, 51 peripheral artery vascular surgery patients underwent ambulatory continuous 12-lead ECG
monitoring in the postoperative setting. Ischemic load, defined
as the area under the curve defined by ischemic ST-segment
deviation and ischemic time, was shown to predict perioperative myocardial infarction with an area under the receiver
operating characteristics curve of 0.87. Notably, ischemia was
asymptomatic in 14 of the 17 identified patients, demonstrating value of this modality as a warning tool. Thus, continuous 12-lead ECG monitoring may provide greater sensitivity
than 3-lead ECG for the detection of perioperative myocardial
ischemia, and may become standard for monitoring high-risk
surgical patients. (See Schwartz 11th ed., p. 435-6.)
4. Regarding preload, which of the following is TRUE?
A. It is approximated by the systemic vascular resistance
which is calculated by dividing mean arterial pressure by cardiac output.
B. It is approximated by the right ventricular end-
diastolic pressure as estimated with pulmonary artery
occlusion pressure.
C. It is approximated by the right ventricular end-
diastolic pressure as estimated with central venous
pressure (CVP).
D. It is approximated by the left ventricular end-
diastolic pressure as estimated with pulmonary artery
occlusion pressure.
Answer: D
Strictly speaking, preload is determined by end-diastolic volume (EDV). In practice, EDV is challenging to measure precisely during the cardiac cycle, and so clinicians utilize the
end-diastolic pressure (EDP) as a reasonable surrogate. For
the right ventricle, CVP approximates right ventricular EDP.
For the left ventricle, pulmonary artery occlusion pressure
(PAOP), which is measured by transiently inflating a balloon
at the end of a pressure monitoring catheter positioned in a
small branch of the pulmonary artery, approximates left ventricular EDP. The presence of atrioventricular valvular stenosis may alter this relationship.
There are limits to the utilization of EDP as a surrogate for
EDV when evaluating preload. For example, EDP is determined not only by volume but also by the diastolic compliance of the ventricular chamber. Ventricular compliance is
altered by various pathologic conditions and pharmacologic
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agents. Furthermore, the relationship between EDP and true
preload is not linear, but rather is exponential (Fig. 13-2A,B).
This fact limits the utility of EDP as a surrogate marker at
extremes of EDV. (See Schwartz 11th ed., p. 436-7.)
Left ventricle pressure-volume loop
Elastance line
End-systolic
volume
Stroke volume
Left ventricular pressure (mm Hg)
ESPVR line
Left ventricular volume (mm Hg)
End-diastolic
volume
D
E
e
n
i
l
R
V
P
Left ventricular pressure (mm Hg)
FIG. 13-2 A-B. Left ventricular pressure-volume loops constructed for various clinically relevant
scenarios. For further information refer to the text. A. Standard left ventricular pressure-volume
loop, with stroke volume, end-systolic volume, and end-diastolic volume highlighted for reference.
Note the directionality of the pressure-volume loop, which is not annotated in the figure B for
clarity. B. Demonstration of the effect of changing preload.
Changing preload
(end-diastolic volume)
ESPVR line
Left ventricular volume (mm Hg)
e
n
i
l
R
V
P
D
E
CHAPTER 13
Physiologic Monitoring of the Surgical Patient
5. All of the following are TRUE EXCEPT:
A. The relationship between end-diastolic pressure
(EDP) and preload is linear.
B. EDP is determined by both volume and compliance
of the ventricle.
C. The relationship between EDP and end-diastolic
volume (EDV) can be changed with pharmacologic
agents.
D. EDP is often used as a surrogate for EDV because it is
easier to approximate in the clinical setting.
6. Which of the following does NOT reduce complications
associated with arterial lines?
A. Using a 20-guage or smaller catheter in the radial
artery
B. Ensuring good collateral flow in the distal vascu-
lar bed (ie, performing an Allen’s test) before line
placement
C. Routine exchange of catheters every 5 to 7 days to
prevent line-associated infections
D. Avoid flushing the arterial line when air is present in
the system, and only use a small volume (ie, <5 mL)
for flushing the line
Answer: A
Strictly speaking, preload is determined by EDV. In practice,
EDV is challenging to measure precisely during the cardiac
cycle, and so clinicians utilize the EDP as a reasonable surrogate. For the right ventricle, central venous pressure (CVP)
approximates right ventricular EDP. For the left ventricle,
pulmonary artery occlusion pressure (PAOP), which is measured by transiently inflating a balloon at the end of a pressure monitoring catheter positioned in a small branch of the
pulmonary artery, approximates left ventricular EDP. The
presence of atrioventricular valvular stenosis may alter this
relationship.
There are limits to the utilization of EDP as a surrogate for
EDV when evaluating preload. For example, EDP is determined not only by volume but also by the diastolic compliance of the ventricular chamber. Ventricular compliance is
altered by various pathologic conditions and pharmacologic
agents. Furthermore, the relationship between EDP and true
preload is not linear, but rather is exponential (Fig. 13-2A,B).
This fact limits the utility of EDP as a surrogate marker at
extremes of EDV. (See Schwartz 11th ed., p. 436-7.)
Answer: C
Distal ischemia is an uncommon complication of intra- arterial
catheterization. The incidence of thrombosis is increased
when larger-caliber catheters are employed and when catheters are left in place for an extended period of time. The incidence of thrombosis can be minimized by using a 20-gauge
(or smaller) catheter in the radial artery and removing the
catheter as soon as feasible. The risk of distal ischemic injury
can be reduced by ensuring that adequate collateral flow is
present prior to catheter insertion. At the wrist, adequate collateral flow can be documented by performing a modified
version of the Allen test, wherein the artery to be cannulated
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