II.5. Control de Constitucionalidad
II.5.1. Difuso
2. Capacitive coupling
A. Results when energy bleeds rom a port sleeve or lapa-roscope into adjacent (but not touching) bowel
B. Is always recognized at the time o surgery
C. Can result in mal unction o the electrocardiogram monitor
D. Can result in inaccurate image transmission to the dig-ital monitor
Answer: A
o avoid thermal injury to adjacent structures, the laparo-scopic ield o view must include all uninsulated portions o the electrosurgical electrode. In addition, the integrity o the insulation must be maintained and assured. Capacitive cou-pling occurs when a plastic trocar insulates the abdominal wall rom the current; in turn the current is bled o a metal sleeve or laparoscope into the viscera (Fig. 14-1). his may result in thermal necrosis and a delayed ecal istula. Another potential mechanism or unrecognized visceral injury may occur with the direct coupling o current to the laparoscope and adjacent bowel. (See Schwartz 10th ed., Figure 14-7, pp. 427–428.)
1. T e most common arrhythmia seen during laparoscopy is A. Atrial brilation
B. Sinus tachycardia
C. Premature ventricular contractions D. Sinus bradycardia
Answer: D
he pressure e ects o the pneumoperitoneum on cardiovas-cular physiology also have been studied. In the hypovolemic individual, excessive pressure on the in erior vena cava and a reverse rendelenburg position with loss o lower extremity muscle tone may cause decreased venous return and cardiac output. his is not seen in the normovolemic patient. he most common arrhythmia created by laparoscopy is bradycar-dia. A rapid stretch o the peritoneal membrane o ten causes a vagovagal response with bradycardia and occasionally hypotension. he appropriate management o this event is desu lation o the abdomen, administration o vagolytic agents (eg, atropine), and adequate volume replacement. (See Schwartz 10th ed., p. 418.)
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4. Systemic e ects o CO2 rom pneumoperitoneum can cause all o the ollowing EXCEP
A. Hypercarbia
B. Increased myocardial oxygen demand C. Alterations in preload
D. Increased af er load
Answer: C
Alterations in preload are local e ects (pressure speci ic) o CO2 peritoneum.
he physiologic e ects o CO2 pneumoperitoneum can be divided into two areas (1) gas-speci ic e ects and (2) pressure-speci ic e ects (Fig. 14-2). CO2 is rapidly absorbed across the peritoneal membrane into the circulation. In the circula-tion, CO2 creates a respiratory acidosis by the generation o carbonic acid. Body bu ers, the largest reserve o which lies in bone, absorb CO2 (up to 120 L) and minimize the devel-opment o hypercarbia or respiratory acidosis during brie endoscopic procedures. Once the body bu ers are saturated, respiratory acidosis develops rapidly, and the respiratory sys-tem assumes the burden o keeping up with the absorption o CO2 and its release rom these bu ers.
In patients with normal respiratory unction, this is not di icult; the anesthesiologist increases the ventilatory rate or 3. Which o the ollowing are true regarding sa e
laparo-scopic surgery in pregnancy.
A. T e patient should be position in the lef lateral position.
B. Open abdominal access (Hasson) is recommended versus direct puncture laparoscopy (Veress neelde).
C. T e surgery should be per ormed during the second trimester i possible.
D. All o the above.
Answer: D
Concerns about the sa ety o laparoscopic cholecystectomy and appendectomy in the pregnant patient have been thor-oughly investigated and readily managed. Access to the abdo-men in the pregnant patient should take into consideration the height o the uterine undus, which reaches the umbilicus at 20 weeks. In order not to damage the uterus or tis blood supply, most surgeons eel that the open (Hasson) approach should be used in avor o direct puncture laparoscopy. he patient should be positioned slightly on the le t side to avoid compression o the vena cava by the uterus. Because the preg-nancy poses a risk or thromboembolism, sequential compres-sion devices are essential or all procedures. Surgery should be per ormed in the second trimester, i possible. Protection o the etus against intraoperative X-rays is imperative. (See Schwartz 10th ed., pp. 435–436.)
Ca pa citive couple d fa ult condition
Ca pa citive ly couple d e ne rgy to me ta l
ca nnula
Pla s tic colla r ove r me ta l troca r
FIG. 14-1. Capacitive coupling occurs as a result of high current density bleeding from a port sleeve or laparoscope into adjacent bowel. (Reproduced with permission from Odell RC. Laparoscopic electrosurgery, in Hunter JG, Sackier JM, eds. Minimally Invasive Surgery. New York: McGraw-Hill, 1993, p 33.)
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5. While per orming a laparoscopic Nissen undoplication during the transhiatal dissection the mediastinal pleura is compromised and a CO2 pneumothorax develops. What is the initial pre erred management o the pneumothorax?
A. Needle thoracostomy over the second intercostal space, mid-clavicular line.
B. Enlargement o the de ect and placement o an 18-French red rubber catheter across the de ect.
C. Abort the procedure and emergent tube thoracostomy with a 28-French chest tube.
D. No intervention is needed. Continue with the planned procedure.
Answer: B
When a pneumothorax occurs with laparoscopic Nissen un-doplication or Heller myotomy, it is pre erable to place an 18-French red rubber catheter with multiple holes cut out o the distal end across the de ect. At the end o the procedure, the distal end o the tube is pulled out a 10-mm port side (as the port is removed), and the pneumothorax is evacuated to a primitive water-seal using a bowl o sterile water or saline.
(See Schwartz 10th ed., p. 419.)
Loca l e ffe cts
FIG. 14-2. Carbon dioxide gas insufflated into the peritoneal cavity has both local and systemic effects that cause a complex set of hemodynamic and metabolic alterations. (Reproduced with permission from Hunter JG, ed. Baillière’s Clinical Gastroenterology:
Laparoscopic Surgery. London/Philadelphia: Baillière Tindall, 1993, p. 758. Copyright Elsevier.)
vital capacity on the ventilator. I the respiratory rate required exceeds 20 breaths per minute, there may be less e icient gas exchange and increasing hypercarbia. Conversely, i vital capacity is increased substantially, there is a greater opportu-nity or barotrauma and greater respiratory motion-induced disruption o the upper abdominal operative ield. In some situations, it is advisable to evacuate the pneumoperitoneum or reduce the intra-abdominal pressure to allow time or the anesthesiologist to adjust or hypercarbia. Although mild respiratory acidosis probably is an insigni icant problem, more severe respiratory acidosis leading to cardiac arrhyth-mias has been reported. Hypercarbia also causes tachycardia and increased systemic vascular resistance, which elevates blood pressure and increases myocardial oxygen demand.
(See Schwartz 10th ed., Figure 14-1, pp. 417–418.)
6. When compared to traditional laparoscopic surgery, the advantages o computer-enhanced surgery are
A. Natural wrist movements and improved manual dexterity
B. Ergonomically com ortable workstation with 3-D imaging wrist to laparoscopic surgery and improved manual dexterity by developing ergonomically com ortable workstation, with 3-D imaging, tremor elimination, and scaling o movements (eg, large, gross hand movements can be scaled down to allow suturing with microsurgical precision). he most recent itera-tion o the robotic plat orm eatures a second console slave enabling greater assisting and teaching opportunities. (See Schwartz 10th ed., p. 429.)
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7. A patient undergoing laparoscopic colon resection is noted to have decreased urine output during the last hour o the case. A bolus is given at the end o the case. One hour later, there is still very poor urine output. T e appropriate treatment is
A. Repeat bolus
B. Intravenous (IV) urosemide C. Check urine electrolytes
D. None o the above
Answer: D
Low urine output is a normal physiologic response to increased intra-abdominal pressure or up to 1 hour a ter sur-gery. Although the e ect o the pneumoperitoneum on renal blood low are immediately reversible, the hormonally medi-ated changes such as elevmedi-ated antidiuretic hormone levels decrease urine output or up to 1 hour a ter the procedure has ended. Intraoperative oliguria is common during laparoscopy, but the urine output is not a re lection o intravascular status;
intravenous (IV) luid administration during an uncompli-cated laparoscopic procedure should not be linked to urine output. (See Schwartz 10th ed., p. 418.)
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Answer: A
Four major steps in the control o eukaryotic gene expression (Fig. 15-1). ranscriptional and posttranscriptional control determine the level o messenger RNA (mRNA) that is avail-able to make a protein, while translational and posttrans-lational control determine the inal outcome o unctional proteins. Note that posttranscriptional and posttranslational controls consist o several steps. (See Schwartz 10th ed., Figure 16-6, p. 446.)