Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_891_Библиотеки_им_академика_М_И_Перельмана
.pdf
108
∫
−()
BI
VK KT T
https://t.me/medicina_free
CHAPTER 13
Physiologic Monitoring of the Surgical Patient
7. The thermodilution technique for determining cardiac
output:
A. Calculates QT with the Fick equation.
B. Underestimates cardiac output at low values.
C. Should be performed with a cold indicator liquid to
increase the signal-to-noise ratio.
D. Is influenced by respiratory cycle due to changes in
blood temperature and QT.
is digitally compressed while using a Doppler stethoscope to
listen for perfusion in the palmar arch vessels.
Another potential complication of intra-arterial monitoring is retrograde embolization of air bubbles or thrombi into
the intracranial circulation. In order to minimize this risk
care should be taken to avoid flushing arterial lines when
air is present in the system, and only small volumes of fluid
(<5 mL) should be employed for this purpose. Catheterrelated infections can occur with any intravascular monitoring device. However, catheter-related bloodstream infection
is a relatively uncommon complication of intra-arterial lines
used for monitoring, occurring in 0.4% to 0.7% of catheterizations. The incidence increases with longer duration of arterial catheterization. (See Schwartz 11th ed., p. 435.)
Answer: D
The relationship used for calculating QT is called the StewartHamilton equation:
12
=
Q
T
()d
Tt t
B
where V is the volume of the indicator injected, TB is the
temperature of blood (ie, core body temperature), TI is the
temperature of the indicator, K1 is a constant that is the function of the specific heats of blood and the indicator, K2 is an
empirically derived constant that accounts for several factors (the dead space volume of the catheter, heat lost from
the indicator as it traverses the catheter, and the injection
rate of the indicator), and ∫TB(t)dt is the area under the timetemperature curve. In clinical practice, the Stewart-Hamilton
equation is solved by a microprocessor.
Determination of cardiac output by the thermodilution
method is generally quite accurate, although it tends to systematically overestimate QT at low values. Changes in blood
temperature and QT during the respiratory cycle can influence the measurement. Therefore, results generally should be
recorded as the mean of two or three determinations obtained
at random points in the respiratory cycle. Using cold injectate widens the difference between TB and TI and thereby
increases signal-to-noise ratio. Nevertheless, most authorities
recommend using room temperature injectate (normal saline
or 5% dextrose in water) to minimize errors resulting from
warming of the fluid as it transferred from its reservoir to a
syringe for injection. (See Schwartz 11th ed., p. 439.)
8. Software creating integrated monitoring systems (such
as the Modified Early Warning Score [MEWS] or Rothman Index [RI] System) have been found to:
A. Alert teams to clinical deterioration preceding a car-
diac or pulmonary arrest.
B. Predict re-admission to the surgical intensive care
unit.
C. Predict whether the patient will survive or not sur-
vive a cardiac or pulmonary arrest.
D. Predict Rapid Response Team (RRT) activation.
Answer: C
The Rothman Index (RI) is a proprietary data analysis toolkit encompassing a total of 26 variables including vital signs,
nursing assessments, laboratory test values, and cardiac
rhythms and was developed to make use of the vast amount
of data input into the electronic medical record (EMR) on a
real-time basis to help provide a global assessment of patient
status. In the initial derivation, Rothman and colleagues
demonstrated concordance of the RI with the Modified Early
Warning Score (MEWS) system, which is designed to alert
medical teams to clinical deterioration that precedes cardiac
or pulmonary arrest events. Subsequent publications evaluated performance of the RI in predicting both readmission to
surgical ICUs in the postoperative setting as well as for rapid
109
https://t.me/medicina_free
9. Which of the following steps incorrectly describes a step
needed for placement of a pulmonary artery catheter?
A. Cannulation of the vein via percutaneous technique
B. Inflate the balloon once respiratory excursions are
observed on the monitor
C. With the balloon inflated, constant observation of
the pressure tracing in the right atrium, right ventricle, and pulmonary artery as the catheter is advanced
D. Leaving the balloon inflated in the pulmonary artery
for constant pulmonary capillary wedge pressure
measurement
response team activations. Although more work is required
to evaluate the broad applicability of the RI and similar
measures, the evidence to date is compelling. (See Schwartz
11th ed., p. 436.)
Answer: D
Cannulation of the vein is normally performed percutaneously,
using the Seldinger technique. A small-bore needle is inserted
through the skin and subcutaneous tissue into the vein. After
documenting return of venous blood, a guidewire with a flexible tip is inserted through the needle into the vein, and the
needle is withdrawn. A dilator/introducer sheath is passed
over the wire, and the wire and the dilator are removed. The
proximal terminus of the distal port of the pulmonary artery
catheter (PAC) is connected through low-compliance tubing
to a strain-gauge transducer, and the tubing-catheter system
is flushed with fluid. While constantly observing the pressure
tracing on a monitor screen, the PAC is advanced with the balloon deflated until respiratory excursions are observed. The balloon is then inflated, and the catheter advanced further, while
monitoring pressures sequentially in the right atrium and right
ventricle en route to the pulmonary artery. The pressure waveforms for the right atrium, right ventricle, and pulmonary artery
are each characteristic (Fig. 13-3). The catheter is advanced out
the pulmonary artery until a damped tracing indicative of the
“wedged” position is obtained. The balloon is then deflated, taking care to ensure that a normal pulmonary arterial tracing is
again observed on the monitor; leaving the balloon inflated can
increase the risk of pulmonary infarction or perforation of the
pulmonary artery. Unnecessary measurements of the pulmonary artery occlusion pressure are discouraged as rupture of the
pulmonary artery may occur. (See Schwartz 11th ed., pp. 437–8.)
CHAPTER 13
Physiologic Monitoring of the Surgical Patient
Balloon
inflated
Right atrium
Pressure (mm Hg)
FIG. 13-3. Representative pressure traces at different stages of insertion of the PAC. In the
central venous circulation, the pressure remains low, with characteristic waves from atrial filling
and tricuspid valve closing. Upon entry into the right ventricle, the pressure increases sharply,
with the broadest range between systole and diastole. When in the main pulmonary artery,
the systolic pressure remains elevated to the same degree, but the diastolic pressure is now
significantly elevated due to the closure of the pulmonic valve during the cardiac cycle. Upon
further advancement with the balloon inflated, the pressure differences become smaller and the
magnitude of the mean pressure drops, reflecting an estimate of the left atrial pressure.
Right ventricle
Pulmonary artery
Pulmonary artery occlusion
110
()
VO
T
https://t.me/medicina_free
10. Which of the following does NOT affect the fractional
CHAPTER 13
saturation of hemoglobin in venous blood (SvO2)?
A. Anemia
B. Fever
C. Age
D. Heart failure
Physiologic Monitoring of the Surgical Patient
11. Using pulse pressure variability (PPV) to determine preload responsiveness:
A. Is reliable for a patient in rate-controlled atrial fibril-
lation, but not for a patient in atrial flutter.
B. Is a better predictor of preload responsiveness than
central venous pressure (CVP).
C. Defines PPV as the difference between the maxi-
mal pulse pressure and the minimum pulse pressure
observed at different points in the respiratory cycle.
D. Is unreliable in mechanically ventilated patients due
to decreased venous return during inspiration.
Answer: C
Oxygen saturation can replace oxygen content, yielding the
final clinically valuable equation:
=−
SO SO
v2 a2
Q
2
Hgb1.36
××
where SVO2 is the fractional saturation of hemoglobin in mixed
venous blood, SaO2 is the fractional saturation of hemoglobin in arterial blood, and Hgb is the concentration of hemoglobin in blood. Thus, it can be seen that SVO2 is a function
of VO2 (ie, metabolic rate), QT, SaO2, and Hgb. Accordingly,
subnormal values of SVO2 can be caused by a decrease
in QT (due, eg, to heart failure or hypovolemia), a
decrease in SaO2 (due, eg, to intrinsic pulmonary disease),
a decrease in Hgb (ie, anemia), or an increase in metabolic rate
(due, eg, to seizures or fever). (See Schwartz 11th ed., p. 440.)
Answer: B
When intrathoracic pressure increases during the application of positive airway pressure in mechanically ventilated
patients, venous return decreases, and as a consequence, left
ventricular stroke volume (LVSV) also decreases. Therefore,
PPV during a positive pressure episode can be used to predict
the responsiveness of cardiac output to changes in preload.
PPV is defined as the difference between the maximal pulse
pressure and the minimum pulse pressure divided by the
average of these two pressures (Fig. 13-4). This approach has
validated this by comparing PPV, CVP, PAOP, and systolic
pressure variation as predictors of preload responsiveness in a
cohort of critically ill patients. Patients were classified as being
“preload responsive” if their cardiac index increased by at least
15% after rapid infusion of a standard volume of intravenous
fluid. Receiver-operating characteristic (ROC) curves demonstrated that PPV was the best predictor of preload responsiveness. Although atrial arrhythmias can interfere with the
usefulness of this technique, PPV remains a useful approach
for assessing preload responsiveness in most patients because
of its simplicity and reliability. (See Schwartz 11th ed., p. 444.)
Inspiration
PP
max
Arterial blood pressure (mm Hg)
FIG. 13-4. Calculation of pulse pressure variation as it would appear on bedside monitor. This
provides a helpful and rapid assessment of fluid responsiveness in the critically ill mechanically
ventilated patient.
Expiration Inspiration InspirationExpiration
PPV (%) =
Time
PP
PP
PP
min
max
max
– PP
+ PP
2
min
min
× 100
111
https://t.me/medicina_free
12. Which of the following does not affect SaO2 (oxygen saturation of hemoglobin in arterial blood) in mechanically
ventilated patients?
A. Mean airway pressure
B. FiO2 (fraction of inspired oxygen)
C. SvO2 (oxygen saturation of hemoglobin in venous
blood)
D. Respiratory rate
13. Which of the following regarding P
(peak airway pres-
peak
sure) is true?
A. P
B. To measure P
C. P
is measured at the end of inspiration.
peak
is independent of airway resistance, chest wall
peak
, the expiratory valve must be closed.
peak
compliance, and peak inspiratory flow.
D. P
is not routinely measured in mechanically venti-
peak
lated patients.
Answer: D
DO2 is dependent to a greater degree on the oxygen saturation of hemoglobin (Hgb) in arterial blood (SaO2) than on the
partial pressure of oxygen in arterial blood (PaO2). DO2 also
is dependent on QT and Hgb. As discussed earlier and illustrated mathematically by previous equations, the dissolved
oxygen in blood makes only a negligible contribution to DO2.
SaO2 in mechanically ventilated patients depends on the mean
airway pressure, the fraction of inspired oxygen (FiO2), and
SvO2. Thus, when SaO2 is low, the clinician has only a limited number of ways to improve this parameter. The clinician
can increase mean airway pressure by increasing positive-end
expiratory pressure (PEEP) or inspiratory time. FiO2 can be
increased to a maximum of 1.0 by decreasing the amount of
room air mixed with the oxygen supplied to the ventilator.
SvO2 can be increased by increasing Hgb or QT or decreasing oxygen utilization (eg, by administering a muscle relaxant
and sedation). (See Schwartz 11th ed., p. 445.)
Answer: A
Airway pressures are routinely monitored in mechanically
ventilated patients. The peak airway pressure measured at
the end of inspiration (P
) is a function of the tidal volume,
peak
the resistance of the airways, lung/chest wall compliance, and
peak inspiratory flow. The airway pressure measured at the
end of inspiration when the inhaled volume is held in the
lungs by briefly closing the expiratory valve is termed the pla-
teau airway pressure (P
). As a static parameter, plateau
plateau
airway pressure is independent of the airway resistance and
peak airway flow and is related to the lung/chest wall compliance and delivered tidal volume. Mechanical ventilators
monitor P
alarm if the P
with each breath and can be set to trigger an
peak
exceeds a predetermined threshold. P
peak
plateau
is not measured routinely with each delivered tidal volume
but rather is measured intermittently by setting the ventilator
to close the exhalation circuit briefly at the end of inspiration and record the airway pressure when airflow is zero. (See
Schwartz 11th ed., p. 446.)
CHAPTER 13
Physiologic Monitoring of the Surgical Patient
14. Causes of an increase in end-tidal-CO2 include:
A. Massive pulmonary embolism.
B. Reduced cardiac output.
C. Sustained hyperventilation.
D. Reduced minute ventilation.
Answer: D
Continuous monitoring with capnography has become
routine during surgery under general anesthesia and for
some intensive care patients. A number of situations can be
promptly detected with continuous capnography. A sudden
reduction in P2 suggests either obstruction of the sampling tubing with water or secretions, or a catastrophic event
such as loss of the airway, airway disconnection or obstruction, ventilator malfunction, or a marked decrease in QT. If
the airway is connected and patent and the ventilator is functioning properly, then a sudden decrease in P2 should
prompt efforts to rule out cardiac arrest, massive pulmonary
embolism, or cardiogenic shock. P2 can be persistently
low during hyperventilation or with an increase in dead space
such as occurs with pulmonary embolization (even in the
absence of a change in QT). Causes of an increase in P2
include reduced minute ventilation or increased metabolic
rate. (See Schwartz 11th ed., p. 447.)
112
https://t.me/medicina_free
15. Which of the following is NOT an indication for intra-
CHAPTER 13
cranial pressure monitoring?
A. Glasgow Coma Scale (GCS) ≤ 8 with an abnormal
computed tomography (CT) scan
B. Severe traumatic brain injury (TBI) in a patient with
age > 40 years and systolic blood pressure < 90 mm Hg
C. Intracranial hemorrhage without intraventricular
Physiologic Monitoring of the Surgical Patient
16. Currently accepted uses of transcranial Doppler (TCD)
blood
D. Fulminant hepatic failure with coma and cerebral
edema on CT
include all of the following EXCEPT:
A. Diagnosing vasospasm after subarachnoid
hemorrhage.
B. Estimating cerebral perfusion pressure.
C. Confirming brain death after clinical examination in
patients under the influence of central nervous sys-
tem (CNS) depressants.
D. Confirming brain death after clinical examination in
patients with metabolic encephalopathy.
Answer: C
Monitoring of intracranial pressure (ICP) is currently recommended in patients with severe TBI, defined as a GCS score
≤ 8 with an abnormal CT scan, and in patients with severe
TBI and a normal CT scan if two or more of the following
are present: age > 40 years, unilateral or bilateral motor posturing, or systolic blood pressure < 90 mm Hg. ICP monitoring also is indicated in patients with acute subarachnoid
hemorrhage with coma or neurologic deterioration, intracranial hemorrhage with intraventricular blood, ischemic middle cerebral artery stroke, fulminant hepatic failure with coma
and cerebral edema on CT scan, and global cerebral ischemia
or anoxia with cerebral edema on CT scan. The goal of ICP
monitoring is to ensure that cerebral perfusion pressure (CPP)
is adequate to support perfusion of the brain. CPP is equal to
the difference between MAP and ICP: CPP = MAP – ICP.
(See Schwartz 11th ed., pp. 447–8.)
Answer: B
TCD measurements of middle and anterior cerebral artery
blood flow velocity are useful for the diagnosis of cerebral
vasospasm after subarachnoid hemorrhage. Qureshi and
associates demonstrated that an increase in the middle cerebral artery mean flow velocity as assessed by TCD is an independent predictor of symptomatic vasospasm in a prospective
study of patients with aneurysmal subarachnoid hemorrhage.
In addition, while some have proposed using TCD to estimate intracranial pressure (ICP), studies have shown that
TCD is not a reliable method for estimating ICP and cerebral
perfusion pressure (CPP) and currently cannot be endorsed
for this purpose. TCD also is useful to confirm the clinical
examination for determining brain death in patients with
confounding factors such as the presence of CNS depressants
or metabolic encephalopathy. (See Schwartz 11th ed., p. 448.)
17. Excessive pressure on the lung parenchyma is known to
cause all of the following EXCEPT:
A. Diffuse alveolar damage similar to ARDS.
B. Impaired venous return.
C. Improved oxygenation.
D. Pneumothorax.
18. Which of the following does NOT support a diagnosis of
abdominal compartment syndrome (ACS)?
A. Oliguria
B. Elevated peak airway pressures
C. Intra-abdominal pressure (IAP) consistently > 20 mm
Hg, recorded by measurements 30 minutes apart
D. Intra-abdominal pressure (IAP) consistently > 20 mm
Hg, with measurements 1 to 2 hours apart
Answer: C
Ventilator-induced lung injury (VILI) is now an established
clinical entity of great relevance to the care of critically ill
patients. Excessive airway pressure and tidal volume adversely
affect pulmonary and possibly systemic responses to critical
illness. Subjecting the lung parenchyma to excessive pressure,
known as barotrauma, can result in parenchymal lung injury,
diffuse alveolar damage similar to ARDS, and pneumothorax,
and can impair venous return and therefore limit cardiac output. Lung-protective ventilation strategies have been developed to prevent the development of VILI and improve patient
outcomes. (See Schwartz 11th ed., p. 446.)
Answer: C
The triad of oliguria, elevated peak airway pressures, and elevated intra-abdominal pressure is known as abdominal compartment syndrome (ACS). This syndrome, first described in
patients after repair of ruptured abdominal aortic aneurysm,
is associated with interstitial edema of the abdominal organs,
resulting in elevated IAP. When IAP exceeds venous or capillary pressures, perfusion of the kidneys and other intraabdominal viscera is impaired. Oliguria is a cardinal sign.
While the diagnosis of ACS is a clinical one, measuring IAP
is useful to confirm the diagnosis. Ideally, a catheter inserted
113
https://t.me/medicina_free
into the peritoneal cavity could measure IAP to substantiate the diagnosis. In practice, transurethral bladder pressure
measurement reflects IAP and is most often used to confirm
the presence of ACS. After instilling 50 to 100 mL of sterile
saline into the bladder via a Foley catheter, the tubing is connected to a transducing system to measure bladder pressure
in the supine position at end-expiration.
Intra-abdominal hypertension is defined as an IAP ≥ 12 mm
Hg recorded on three standard measurements conducted 4 to
6 hours apart and is separated into several grades. The diagnosis of ACS is the presence of an IAP ≥ 20 mm Hg recorded
by three measurements 1 to 6 hours apart, along with new
onset of organ dysfunction (Table 13-1). Less commonly,
gastric or inferior vena cava pressures can be monitored with
appropriate catheters to detect elevated intra-abdominal
pressures. (See Schwartz 11th ed., p. 447.)
TABLE 13–1 Bladder pressure measurements in the
assessment of intra-abdominal hypertension
or abdominal compartment syndrome
Recorded Pressure (mm Hg) Grade of IAH or ACS
5–7 Normal
In the absence of organ dysfunction:
12–15 Grade I IAH
16–20 Grade II IAH
21–25 Grade III IAH
>25 Grade IV IAH
In the presence of new-onset organ dysfunction:
>20 ACS
Data from Kirkpatrick AW, Roberts DJ, De Waele J, et al: Intraabdominal hypertension
and the abdominal compartment syndrome: updated consensus definitions and clinical
practice guidelines from the World Society of the Abdominal Compartment Syndrome,
Intensive Care Med. 2013;39(7):1190-1206.
CHAPTER 13
Physiologic Monitoring of the Surgical Patient
This page intentionally left blank
https://t.me/medicina_free
CHAPTER 14
https://t.me/medicina_free
Minimally Invasive Surgery
1. The most common arrhythmia seen during laparoscopy is:
A. Atrial fibrillation.
B. Sinus tachycardia.
C. Premature ventricular contractions.
D. Sinus bradycardia.
2. A 23-year-old man presents to the emergency department with a 17-hour history of abdominal pain that
started in the periumbilical region, now located in the
RLQ, associated with fever, nausea, WBC 14,000, and
imaging consistent with acute appendicitis. You consent
the patient for a laparoscopic appendectomy. During initial insufflation of the abdomen the heart rate goes down
to 36 and the patient becomes hypotensive. What is the
best next step in the management of this patient?
A. Give 1L of crystalloids
B. Immediate IV atropine
C. Desufflation of the abdomen
D. Evaluate for hemorrhage
Answer: D
The pressure effects of the pneumoperitoneum on cardiovascular physiology also have been studied. In the hypovolemic
individual, excessive pressure on the inferior vena cava and a
reverse Trendelenburg position with loss of lower extremity
muscle tone may cause decreased venous return and decreased
cardiac output. This is not seen in the normovolemic patient.
The most common arrhythmia created by laparoscopy is bradycardia. A rapid stretch of the peritoneal membrane often
causes a vagovagal response with bradycardia and, occasionally, hypotension. The appropriate management of this event
is desufflation of the abdomen, administration of vagolytic
agents (eg, atropine), and adequate volume replacement. (See
Schwartz 11th ed., p. 455.)
Answer: C
The pressure effects of the pneumoperitoneum on cardiovascular physiology also have been studied. In the hypovolemic
individual, excessive pressure on the inferior vena cava and a
reverse Trendelenburg position with loss of lower extremity
muscle tone may cause decreased venous return and decreased
cardiac output. This is not seen in the normovolemic patient.
The most common arrhythmia created by laparoscopy is bradycardia. A rapid stretch of the peritoneal membrane often
causes a vasovagal response with bradycardia and, occasionally, hypotension. The appropriate management of this event
is desufflation of the abdomen, administration of vagolytic
agents (eg, atropine), and adequate volume replacement. (See
Schwartz 11th ed., p. 455.)
3. A patient undergoing laparoscopic colon resection is
noted to have decreased urine output during the last
hour of the case. A bolus is given at the end of the case.
One hour later, there is still low urine output. The appropriate treatment is:
A. Repeat bolus.
B. Intravenous (IV) furosemide.
C. Check urine electrolytes.
D. Observe.
Answer: D
Although the effects of the pneumoperitoneum on renal
blood flow are immediately reversible, the hormonally mediated changes such as elevated antidiuretic hormone levels
decrease urine output for up to 1 hour after the procedure has
ended. Intraoperative oliguria is common during laparoscopy,
but the urine output is not a reflection of intravascular volume status; IV fluid administration during an uncomplicated
laparoscopic procedure should not be linked to urine output.
115
116
https://t.me/medicina_free
CHAPTER 14
Minimally Invasive Surgery
4. While performing a laparoscopic Nissen fundoplication, during the transhiatal dissection the mediastinal
pleura is compromised and a CO2 pneumothorax develops. What is the initial preferred management of the
pneumothorax?
A. Needle thoracostomy over the second intercostal
space, mid-clavicular line.
B. Enlargement of the defect and placement of an
18-French red rubber catheter across the defect.
C. Abort the procedure and emergent tube thoracos-
tomy with a 28-French chest tube.
D. No intervention is needed. Continue with the planed
procedure.
5. During pneumoperitoneum, the increased intra-abdominal pressure directly and indirectly results in:
A. Increased renal blood flow.
B. Decreased urine output.
C. Decreased levels of renin.
D. Decreased sodium retention.
Because insensible fluid losses through the open abdomen are
eliminated with laparoscopy, the need for supplemental fluid
during a laparoscopic surgical procedure should only keep
up with venous pooling in the lower limbs, third-space losses
into the bowel, and blood loss, which is generally less than
occurs with an equivalent open operation. (See Schwartz 11th
ed., p. 456.)
Answer: B
When a pneumothorax occurs with laparoscopic Nissen fundoplication or Heller myotomy, it is preferable to place an
18-French red rubber catheter with multiple side holes cut
out of the distal end across the defect. At the end of the procedure, the distal end of the tube is pulled out a 10-mm port site
(as the port is removed), and the pneumothorax is evacuated
to a primitive water seal using a bowl of sterile water or saline.
During laparoscopic esophagectomy, it is preferable to leave
a standard chest tube, as residual intra-abdominal fluid will
tend to be siphoned through the defect postoperatively if the
tube is removed at the end of the case. (See Schwartz 11th ed.,
p. 456.)
Answer: B
Increased intra-abdominal pressure decreases renal blood
flow, glomerular filtration rate, and urine output. These
effects may be mediated by direct pressure on the kidney and
the renal vein. The secondary effect of decreased renal blood
flow is to increase plasma renin release, thereby increasing
sodium retention. (See Schwartz 11th ed., p. 456.)
6. Which type of radiofrequency electrosurgery mode has
the highest risk for thermal injury?
A. Bipolar coagulation
B. Monopolar coagulation
C. Monopolar cutting
D. Monopolar blended
7. Which of the following represents advantages from
robotic surgery compared to laparoscopic surgery?
A. Increased dexterity
B. Tremor elimination
C. Scaling movement
D. All of the above
Answer: B
A short-duration, high-voltage discharge of current (coagulation current) provides extremely rapid tissue heating. Lowervoltage, higher-wattage current (cutting current) is better
for tissue desiccation and vaporization. When the surgeon
desires tissue division with the least amount of thermal injury
and least coagulation necrosis, a cutting current is used.
With bipolar electrosurgery, the electrons flow between
two adjacent electrodes. The tissue between the two electrodes is heated and desiccated. There is little opportunity
for tissue cutting when bipolar current is used alone, but the
ability to coapt the electrodes across a vessel provides the best
method of small-vessel coagulation without thermal injury to
adjacent tissues. (See Schwartz 11th ed., p. 465.)
Answer: D
The major revolution in robotic surgery was the development of a master-slave surgical platform that returned the
wrist to laparoscopic surgery and improved manual dexterity by developing an ergonomically comfortable work station,
with 3-D imaging, tremor elimination, and scaling of movement (eg, large, gross hand movements can be scaled down to
allow suturing with microsurgical precision) (Fig. 14-1). (See
Schwartz 11th ed., p. 467.)
FIG. 14-1. Robotic instruments and hand controls. The
https://t.me/medicina_free
surgeon is in a sitting position, and the arms and wrists
are in an ergonomic and relaxed position.
117
CHAPTER 14
Minimally Invasive Surgery
8. To date, what is the only surgery that has demonstrated
better outcomes using robotic versus laparoscopic or
open techniques?
A. Nissen fundoplication
B. Cholecystectomy
C. Prostatectomy
D. Roux-en-Y gastric bypass
9. Which of the following are TRUE regarding safe laparoscopic surgery in pregnancy?
A. The patient should be positioned slightly on the left
lateral position.
B. Open abdominal access (Hasson) is recommended
versus direct puncture laparoscopy (Veress needle).
C. The surgery should be performed during the second
trimester if possible.
D. All of the above.
Answer: C
The tidal wave of enthusiasm for robotic surgery came
when most minimally invasive urologists declared robotic
prostatectomy to be preferable to laparoscopic and open
prostatectomy. The great advantage—it would appear—of
robotic prostatectomy is the ability to visualize and spare the
pelvic nerves responsible for erectile function. (See Schwartz
11th ed., p. 467.)
Answer: D
Concerns about the safety of laparoscopic cholecystectomy or
appendectomy in the pregnant patient have been thoroughly
investigated and are readily managed. Access to the abdomen in the pregnant patient should take into consideration
the height of the uterine fundus, which reaches the umbilicus
at 20 weeks. In order not to damage the uterus or its blood
supply, most surgeons feel that the open (Hasson) approach
should be used in favor of direct puncture laparoscopy. The
patient should be positioned slightly on the left side to avoid
compression of the vena cava by the uterus. Because pregnancy poses a risk for thromboembolism, sequential compression devices are essential for all procedures. Fetal acidosis
induced by maternal hypercarbia also has been raised as a
concern. (See Schwartz 11th ed., p. 473.)
Соседние файлы в папке Библиотека им академика М.И. Перельмана