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improved outcomes in colon and rectal surgery 23. Lau WY,Chu KW,Poon GP,Ho KK.Prophylactic antibiotics in elective colorectal surgery. Br J Surg 1988; 75(8): 782–5. 24. Schoetz DJ Jr,Roberts PL,Murray JJ,Coller JA,Veidenheimer MC.Addition of parenteral cefoxitin to regimen of oral anti-biotics for elective colorectal operations.A randomized pro-spective study.Ann Surg 1990; 212(2): 209–12. 25. Stellato TA, Danziger LH, Gordon N. Antibiotics in elective colon surgery.A randomized trial of oral,systemic,and oral/ systemic antibiotics for prophylaxis. Am Surg 1990; 56(4): 251–4. 26. Hewitt J, Reeve J, Rigby J, Cox AG. Whole-gut irrigation in preparation for large-bowel surgery. Lancet 1973; 2(7825): 337–40. 27. Food and Drug Administration,HHS.Drug labeling;sodium labeling for over-the-counter drugs. Final rule. Fed Regist 2004; 69(228): 69278–80. 28. Zmora O, Mahajna A, Bar-Zakai B. Colon and rectal surgery without mechanical bowel preparation: a randomized pro-spective trial.Ann Surg 2003; 237(3): 363–7. 29. Beck DE, Fazio VW. Current preoperative bowel cleansing methods.Results of a survey.Dis Colon Rectum 1990; 33(1): 12–5. 30. Brownson P, Jenkins SA, Nott D, Ellenbogen S. Mechanical bowel preparation before colorectal surgery: results of a pro-spective randomized trial. Br J Surg 1992; 79: 461–2. 31. Burke P, Mealy K, Gillen P et al. Requirement for bowel preparation in colorectal surgery. Br J Surg 1994; 81(6): 907–10. 32. Santos JC Jr,Batista J,Sirimarco MT,Guimarães AS,Levy CE. Prospective randomized trial of mechanical bowel prepara-tion in patients undergoing elective colorectal surgery. Br J Surg 1994; 81(11): 1673–6. 33. Miettinen RP,Laitinen ST,Mäkelä JT,Pääkkönen ME.Bowel preparation with oral polyethylene glycol electrolyte solution vs. no preparation in elective open colorectal surgery: pro-spective, randomized study. Dis Colon Rectum 2000; 43(5): 669–75; discussion 675–7. 34. Zmora O,Mahajna A,Bar-Zakai B et al.Is mechanical bowel preparation mandatory for left-sided colonic anastomosis? Results of a prospective randomized trial. Tech Coloproctol 2006; 10(2): 131–5. 35. Fa-Si-Oen P,Roumen R,Buitenweg J et al.Mechanical bowel preparation or not? Outcome of a multicenter, randomized trial in elective open colon surgery. Dis Colon Rectum 2005; 48(8): 1509–16. 36. Bucher P,Gervaz P,Soravia C et al.Randomized clinical trial of mechanical bowel preparation vs. no preparation before elective left-sided colorectal surgery. Br J Surg 2005; 92(4): 409–14. Erratum in: Br J Surg 2005; 92(8): 1051. 37. Ram E,Sherman Y,Weil R,et al. Is mechanical bowel prepa-ration mandatory for elective colon surgery? A prospective randomized study.Arch Surg 2005; 140: 285–288. 38. Conrad JK, Ferry KM, Foreman ML et al.Changing manage-ment trends in penetrating colon trauma.Dis Colon Rectum 2000; 43(4): 466–71. 39. Guenaga KF, Matos D, Castro AA, Atallah AN, Wille-Jørgensen P. Mechanical bowel preparation for elective colorectal surgery. Cochrane Database Syst Rev. 2003; 2: CD001544. Review. Update in: Cochrane Database Syst Rev 2005; 1: CD001544. 40. Jung B, Påhlman L, Nyström PO, Nilsson E. Mechanical bowel preparation study group. Multicentre randomized clinical trial of mechanical bowel preparation in elective colonic resection. Br J Surg 2007; 94(6): 689–95.  3 Anesthesia and intraoperative positioning Lebron Cooper and Larry R Hutson chAllenging cAse A 47-year-old male is undergoing a transanal excision of a rectal villous adenoma under intravenous sedation and local infiltration of xylocaine.During the procedure the patient complains of light-headedness and numbness of the tongue. The anesthesiologist notices bradycardia and hypotension. cAse mAnAgement Xylocaine toxicity is suspected. The patient should be moved to the supine position and supported with supplemental oxygen via mask.The patient’s blood pressure is supported with intravenous fluid and epinephrine. introduction The American Society of Anesthesiologists (ASA) defines anesthe-siology as a discipline within the practice of medicine that special-izes in the (1) medical management of patients who are rendered unconsciousand/orinsensibletopainandemotionalstress during surgical,obstetric,and certain other medical procedures;(2) protec-tion of life functions and vital organs under the stress of anesthetic, surgical, and other medical procedures; and (3) management of problemsinpainrelief (1).Inthischapter,wewillbediscussingthe various kinds of anesthesia used in the operating room for colorec-tal surgery, including their relative benefits and risks.Additionally, we will be discussing new treatments for postoperative pain relief, as well as one of the more visible risks of anesthesia—awareness under anesthesia. We will also discuss the new Surgical Care Improvement Project (SCIP), including prophylactic antibiotic administration within 1 hour of surgical incision, and the proper positioning and padding of patients for colorectal surgery. AnesthesiA Local Anesthesia The earliest local anesthetic used was cocaine (prepared in weak solutions and injected in high volumes) for field block at the turn of the19thcentury.(2)However,thetoxicityof cocaine,itsirritant properties, and its strong potential for physical and psychological dependence led to the development ofalternative local anesthetics. Many of these—such as lidocaine—are still used today,as much as half a century after their introduction.(3) While there are relatively few instances in colorectal surgery where it is used as the sole anesthetic, local anesthesia still has a place. It requires, however, a cooperative patient who can remain immobile for both the infiltration of the local anesthetic, as well as for the actual procedure itself. It is important to be cognizant of the patient’s underlying health status and the position that the patient will be in for the procedure. A healthy patient in their mid-20s can tolerate the prone jack-knife position much better than an obese geriatric patient with a pulmonary history who uses supplemental oxy-gen. Bear in mind that while the patient may only be receiving local anesthesia in an office setting, the patient may be under self-administered mild sedation. Any degree of sedation blunts the body’s response to hypoxia and hypercarbia,and while a rest-less patient may simply be a restless patient, there is always the possibility that the patient is agitated due to relative hypoxia or hypercarbia. Onemustalwayskeepinmindthepossibilityof localanesthetic toxicity when using these drugs. The typical doses used for local infiltration in colorectal procedures are far below the threshold needed for systemic toxicity (Table 3.1).However,accidental intra-venous or intraarterial injection could result in systemic toxicity. As such, it is important to recognize the signs and symptoms of systemic toxicity when they first appear, as toxicity progresses in a dose-dependent fashion. At lower plasma concentrations, the patient begins to experi-ence central nervous system (CNS) toxicity characterized by light-headedness, tinnitus, and numbness of the tongue. As plasma concentrations increase, the patient begins to experience CNS excitation, resulting in seizures, followed by unconsciousness, coma, and respiratory arrest. At higher plasma concentrations, cardiovascular (CV) toxicity occurs, as the local anesthetic blocks sodium channels of the myocardium. Relative potency of the local anesthetic plays a role here. Lidocaine toxicity will result in bradycardia and hypoten-sion before cardiac arrest, while the longer acting, more potent bupivicaine often results in sudden cardiovascular collapse due to ventricular dysrhythmias. Maintenance of perfusion and venti-lation through prolonged cardiopulmonary resuscitation (CPR) is the key, as the patient will not convert into a life-sustaining cardiac rhythm until the local anesthetic has had a chance to completely dissociate from the sodium channels of the conduct-ing system of the heart. Cardiopulmonary bypass may even be considered. Dissociation of local anesthetic from sodium chan-nels has been shown to take a considerable length of time, and prolonged, intensive, and continuous support is warranted. Table 3.1 Local anesthetic drugs. maximum maximum dose Agent onset duration dose with epinephrine Tetracaine 30 seconds 30–60 minutes 400 mg Lidocaine 2–5 minutes 30–45 minutes 5 mg/kg 7 mg/kg Mepivacaine 7–15 minutes 2.5 hours 400 mg Prilocaine 2 minutes 2.5 hours 80 mg Bupivicaine 30 minutes 2 hours 2 mg/kg 4 mg/kg Procaine 5–10 minutes 15–30 minutes 10 mg/kg  improved outcomes in colon and rectal surgery Treatment of CNS toxicity, including the cessation of seizure activity,is with the use of benzodiazepines,propofol,or thiopental. Treatment of CV toxicity is supportive in nature, and may require electric cardioversion, epinephrine, and magnesium.(4) Systemic toxicity following local anesthetic administration is thankfully rare. More common, however, is inadequate analgesia followinglocalanestheticinfiltration.Thiscanbemultifactorialin nature.Inadequate analgesia resulting from insufficient quantities placed in the correct location is easily resolved with the addition of furtherlocalanestheticatthesite.Inadequateanalgesiacanalso result from tachyphylaxis to local anesthetics, which is defined as repeated injection of the same dose of local anesthetic leading to diminishing efficacy. Additionally, inadequate analgesia can be a consequence of the tissue pH into which the local anesthetic is injected. Local anesthetics exist in both an ionized and nonion-ized state; it is only in the nonionized state that local anesthetics can penetrate the nerve sheath, thus producing analgesia. In an acidic environment (i.e., an infected pilonidal cyst), more of the anesthetic is converted into the ionized state, leading to far less of the nonionized form available to produce analgesia. It is not uncommon for infected tissues to prove nearly impossible to be rendered totally insensitive despite more than adequate amounts of local anesthetic infiltration. A perianal block (Figure 3.1) can be performed with the patient in either the prone or lithotomy position and provides relaxation of the sphincter as well as anesthesia. The anesthetic solution of choice is infiltrated in a fan fashion from the lateral positions to superficially encompass the anal margin. Emphasis should be placed in the posterolateral positions where the greatest concentration of nerves is found. A finger or retractor is placed within the canal. At the anterior, posterior, and lateral positions anesthetic is injected submucosally or intramuscularly through the previously infiltrated tissue. The needle is held parallel to the finger, with care to avoid entering the canal. Monitored Anesthetic Care (MAC) MAC is defined by the ASA as “a procedure in which an anesthe-siologist is requested or required to provide anesthetic services,” and includes (1) the diagnosis and treatment of clinical problems during and immediately following the procedure;(2) the support of vital functions; (3) the administration of sedatives, analgesics, hypnotics, anesthetic drugs, or other medications necessary for patient safety; (4) physical and psychological comfort; and (5) the provision of other services as needed to complete the proce-dure safely (5).When it comes to the care of a patient undergoing MAC, all of the precautions and equipment needed to perform a safe general anesthetic must be present, as it is always possible that an escalation of care will be needed. While uncommon, it is possible that a patient cannot safely undergo a MAC for a specific procedure. Most commonly this is due to the inability to safely prevent a patient from moving in response to painful stimuli without producing oversedation and/or apnea. Some patients, when undergoing MAC,tend to have no middle ground between moving in response to stimuli and airway obstruction or com-plete apnea, requiring intervention by the anesthesiologist. The same limits of positioning and patient tolerance that were discussed with local anesthetics apply to procedures under MAC (a) (b) Figure 3.1 Technique for anal block. (A) perianal view of submucosal injection. (B) saggital view of injection of anal canal. as well. While most patients will be able to tolerate a lithotomy or prone position without problem, there are some patients who are unable to tolerate these positions without endotracheal intu-bation, positive pressure ventilation, and high oxygen concen-trations. Additionally, there are those patients who are unable to understandorcomplywiththerequirementthattheymustremain immobile. Young children, mentally challenged, or extremely ill patients are prime examples of poor candidates for MAC. There is an erroneous perception on the part of patients—and even physicians—that a patient undergoing MAC is at decreased  anesthesia and intraoperative positioning risk for serious anesthesia-related complications when compared to general anesthesia, that MAC is safer. This can best be appre-ciated by examining the ASA Closed Claims Project database. The ASA Closed Claims Project is a structured evaluation of all adverse anesthetic outcomes obtained from the closed claim files of 35 professional liability insurance companies in the United States. A 2006 review showed more than 40% of claims associ-ated with MAC involved death or permanent brain damage, which was similarto the percentage seen in claims associated with general anesthesia.Respiratory depression was the most common (21%) damaging mechanism,nearly half of which were judged to be preventable through better monitoring. Cardiovascular events comprised another 14% of the claims made in patients undergoing MAC,which was similar in frequency to that seen following general anesthesia. The average payment made to a plaintiff in these cases was $159,000 (U.S.).(6) So,while we would like to think that MAC is safer than a general anesthetic for patients, in fact the risk of significant injury and death are similar between the two anesthetic types. Regional Anesthesia Central Neuraxial Blockade Regional anesthesia encompasses a wide variety of peripheral and central neuraxial blocks, many of which do not pertain to color-ectal surgery. The most common regional anesthesia technique applied in colorectal surgery is the spinal, or intrathecal, block-ade. The spinal block is relatively easy to place, has a fast onset of sensory and motor blockade, and has a predictable length of efficacy.This is a very old technique,dating back to the late 1800s, when it was performed using cocaine as the anesthetic agent, to great amazement of surgeons of the day.(2) With the advent of newer local anesthetics, we can now tailor the duration of the spinal blockade to the projected length of the surgery by varying the type and amount of local anesthetic used. The goal is to provide adequate analgesia for the duration of the procedure,yet allowing safe ambulation and encouraging urination within a short time frame after cessation of surgery. There are three different densities of the medications used: hyperbaric, isobaric, and hypobaric. Hypobaric local anesthetics are less dense than normal cerebrospinal fluid (CSF),which allows these medications to rise in the CSF following injection. This is commonly used for perineal procedures that will be performed in the prone jack-knife position. The local anesthetic is injected into the intrathecal space, and the patient is immediately placed in the jack-knife position to allow the hypobaric solution to drift upward, or caudad. After approximately 5 minutes, the spinal anesthetic will have “set up”,meaning the uptake and distribution of the local anesthetic across nerve membranes has occurred. No further migration of the drug should occur at this point. By adding a small amount of glucose to the local anesthetic used, the solution will become hyperbaric.The density ofthe solution will cause it to sink in relation to the CSF.(7) An alternative approach to perineal analgesia performed in the prone jack-knife position is performing the intrathecal block using a hyperbaric solution, then keeping patients in the sitting position for 5 minutes to allow the spinal anesthetic to sink caudad, thus blocking the lumbosacral nerves. Once the block has “set up,” the patient is placed in the prone jack-knife position. These two techniques have allowed the use of significantly less local anesthetic for the spinal anesthesia, compared to isobaric solutions,which have the same density as CSF. Isobaric solutions require a higher dose of local anesthetic to evenly distribute throughout the CSF, resulting in a larger volume needed to achieve the same blockade of the lumbosacral nerves. The ben-efits related to reducing the total amount of local anesthetic injected are a decreased risk of toxicity, along with providing adequate analgesia,and allowing faster recovery of motor function. A caudal anesthetic is the placement of a local anesthetic and/ or narcotic into the epidural space from an approach through the sacral hiatus. This is typically performed in either the prone or lateral position. While uncommon in adults, this procedure is used frequently in children,where the caudal space is more easily accessible and a relatively safe and easy approach to infuse local anesthetic and/or narcotic for postoperative analgesia while still under general anesthesia. The third and final type of central neuraxial block is the epidural anesthetic.While epidural anesthesia can be used as the sole anesthetic for colorectal procedures, it is more common to place a catheter within the epidural space to provide analgesia during and after the procedure.The location of the block is deter-mined by the anesthesiologist based on several anatomic factors; however, a thoracic approach has been shown to be more effec-tive in reducing postoperative ileus and early return of bowel and bladder function than a lumbar approach.(8) Most commonly, patients will receive a postoperative continu-ousinfusionof alocalanestheticandnarcoticmixturethroughthe epidural catheter. In addition, they may be given the opportunity to provide themselves small amounts of analgesia through their epidural catheter on demand. This is termed patient-controlled epidural analgesia (PCEA), and it provides excellent pain control while minimizing the undesirable side effects typically seen with intravenousnarcotics.Providedthepatientdoesnotmanifestsigns of systemic infection,the epidural catheter can remain in place for several days following surgery if needed to control pain.This ben-efit must be weighed against the risk of withholding anticoagulant prophylaxis and a possible resultant thromboembolic event. While initial studies examining PCEA were performed using lumbar epidural,more recent studies have examined the impact of thoracic epidural analgesia on patients undergoing elective color-ectal surgery. In a study in 2001, Carli et al. reported 42 patients undergoing open large bowel resection, randomized to receive either an intravenous Patient Controlled Analgesia (ivPCA) mor-phine or a thoracic (T7-8) epidural with bupivicaine and fentanyl. Patients who received thoracic epidural had distinctly superior analgesia as compared to the ivPCA morphine group;time to first flatus and first bowel movement occurred, on average, 36 hours sooner in the epidural group, and time to readiness to discharge was the same in both groups.(8) In 2007,Taqi et al.examined tho-racic epidural analgesia compared to postoperative intravenous morphine for laparoscopic colectomy. Recovery from postopera-tiveileusoccurredsoonerintheepiduralgroupby1or2days,and a full diet was resumed earlier. The epidural group experienced significantly less pain at rest, with coughing, and with ambula-tion.(9) These studies demonstrate the effectiveness of thoracic epidural analgesia and its superiority in allowing early return of  improved outcomes in colon and rectal surgery bowel function,ability to resume a full diet,and early ambulation, as compared to intravenous narcotics. All three of these techniques—spinal, caudal, and epidural— have one thing in common: contraindications. Specifically, abso-lute contraindications to neuraxial techniques include patient refusal, infection at the planned site of needle puncture, elevated intracranial pressure,and bleeding diathesis.There are also several relative contraindications. Bacteremia raises the concern that the needlepuncturesiteof theneuraxialblockmightallowanepidural abscess or meningitis to develop; however, a clinical scenario may exist where the need to avoid a general anesthetic might outweigh the small risk of such occurring. While chronic back pain is not a contraindication to neuraxial techniques, patients with underlying neurological disease should be considered carefully, as neuraxial blockade might exacer-bate their condition, such as in multiple sclerosis. The presence of cardiac disease also indicates that caution should be applied, as patients who receive a neuraxial block typically experience a sudden decrease in lower extremity vascular tone, leading to rapid vasodilation and a significant decrease in systemic vascular resistance.The resultant precipitous drop in systolic and diastolic blood pressure can be extremely dangerous, or even deadly, in patients with severe coronary artery disease, aortic stenosis, and idiopathic hypertrophic subaortic stenosis (IHSS).It is still argu-able whether the presence of IHSS or aortic stenosis is an absolute contraindication to neuraxial blockade, and many centers avoid them in the presence of these coexisting morbidities. The final relative contraindication is abnormal coagulation sta-tus.Patientswithabnormalcoagulation—eitherduetoendogenous factors such as liver disease or thrombocytopenia, or due to the administration of anticoagulants—must be considered carefully. Additionally, patients who are receiving or will be receiving anti-coagulants postoperatively have different needs than patients who receive a general anesthetic alone.For spinal and caudal anesthesia, the greatest risk of spinal hematoma (a neurosurgical emergency) occurs at the time the block is placed. For epidural anesthesia, the risk of hematoma formation is just as great at the time of epidural catheterremovalasduringplacement.Asaresult,certainguidelines shouldbeinstitutedinordertoreducetheriskof spinalhematoma formation upon removal of the epidural catheter. Heparin is often administered perioperatively as prophylaxis against deep vein thrombosis formation. While the effect of intravenous heparin administration is immediate, subcutaneous administration requires 1–2 hours to effect a change on coagula-tion.Small doses of heparin administered before surgery for DVT prophylaxis are not a concern in terms of risk of spinal hematoma formation.(10) Postoperatively, subcutaneous DVT prophylaxis dosing twice daily of heparin while an epidural catheter is in place is acceptable. The catheter is removed 2 hours before the next heparin dosing to maximize safety. Therapeutic heparin, however, is a different matter. Ruff et al. demonstrated that neuraxial procedures performed <1 hour after heparin therapy is discontinued resulted in a 25-fold increase in spinal hematoma.(11) The effect is even more pronounced if the patient also received aspirin. Low-molecular weight heparin (LMWH) was introduced in 1993 as an alternative to heparin prophylaxis for prevention of DVT. There have been numerous reports of spinal hematoma in patients receiving LMWH with a neuraxial blockade.For patients receiving low-dose LMWH for thromboprophylaxis preopera-tively, it is recommended that neuraxial anesthesia occur at least 12 hours after the last dose. In patients who are receiving high-dose LMWH,neuraxial anesthesia should be delayed for 24 hours after the last dose.Postoperatively,the typical prophylactic twice-daily dosing of LMWH should only begin 24 hours after the neu-raxial block,and any epidural catheter should be removed before initiation of twice-daily dosing.Once-daily thromboprophylactic dosing, however, can safely occur with an epidural catheter in place, provided that the first dose occurs at least 8 hours follow-ing the initial blockade and that any epidural catheter is removed 12 hours after the last dose before its removal.(12) Warfarin therapy is another concern.Warfarin anticoagulation must be stopped 4–5 days before surgery,and the PT/INR assessed before surgery. Anticoagulation with warfarin can be used for thromboprophylaxis in patients with an indwelling epidural catheter,though the catheter should be removed while the INR is still <1.5. Typically, this is approximately 36 hours following the initial administration of warfarin. Neurologic and motor testing should be routinely performed on these patients.(12) All three of the neuraxial techniques have possible side effects. Patients can become hypotensive, as their systemic vascular resistance decreases. This is due to the sympathectomy caused by blockade of sympathetic fibers along the thoracic sympathetic chain.Rarely,patients can develop an unintentionally high spinal anesthetic, leading to bradycardia, apnea, and even loss of con-sciousness. This “high spinal” must be treated as a general anes-thetic, with immediate securing of the airway with endotracheal intubation and supportive therapy until the local anesthetic is metabolized. Some patients can experience mild back pain at the site of needle placement, especially when multiple attempts are needed to place the block. Post Dural Puncture Headache (PDPH) can occur, typically following inadvertent dural puncture with an epidural needle—a ‘wet tap’. These headaches are characterized by a slow leak of CSF from the puncture, leading to a headache that is strongest when standing and lessened when lying. They are often treated conservatively with oral fluid therapy, oral caf-feine, and remaining recumbent. Should there be no relief after a couple of days of conservative treatment,an epidural blood patch can be performed. 20 mL of sterile, autologous blood is injected into the epidural space, resulting in thrombus formation, sealing of the dura,and cessation of CSF leak.If the diagnosis of PDPH is correct,there is typically immediate relief of symptoms.Epidural abscess and meningitis are possible if proper sterile technique is not used, or if systemic infection is present.(7) Transversus Abdominis Plane (TAP) Block The TAP block is a relatively new procedure for blocking the abdominal wall afferent nerves by way of the lumber trian-gle of Petit. It can be performed using a landmark technique or under ultrasound guidance; 20 mL of 0.375% of bupivicaine or levobupivicaine is then injected into the transversus abdominis neurofascial plane.(13, 14, 15) In a prospective, randomized controlled trial, McDonnell et al. reported patients undergoing  ... - tailieumienphi.vn