University of Delaware.
Urinary protein excretions greater than ing nephrons and increases in glomerular fltra- 150 mg/d are signifcant order silagra with mastercard otc erectile dysfunction pills that work. It is therefore important to look for in the urine are seen with biliary obstruction generic silagra 50 mg fast delivery vacuum pump for erectile dysfunction in pakistan. White cells and Ketamine pharmacokinetics are minimally altered bacteria are generally associated with infection cheap silagra line erectile dysfunction occurs at what age. Some active hepatic metabolites Disease processes at the level of the nephron pro- are dependent on renal excretion and can potentially duce tubular casts. Benzodiazepines Benzodiazepines undergo hepatic metabolism and conjugation prior to elimination in urine. Because Altered Renal Function most are highly protein bound, increased sensitiv- ity may be seen in patients with hypoalbuminemia. In Opioids the presence of renal impairment, dosage modif- Most opioids currently in use in anesthetic man- cations may be required to prevent accumulation agement (morphine, meperidine, fentanyl, sufent- of the drug or its active metabolites. Remifentanil pharmacokinetics are unaf- latter observation may be the result of decreased fected by renal function due to rapid ester hydro- protein binding of the drug, greater brain penetra- lysis in blood. With the exception of morphine tion due to some breach of the blood–brain barrier, and meperidine, signifcant accumulation of or a synergistic efect with the toxins retained in active metabolites generally does not occur with kidney failure. The phar- date are minimally afected by impaired renal func- macokinetics of the most commonly used opioid tion. Decreased protein binding of etomidate in agonist–antagonists (butorphanol, nalbuphine, patients with hypoalbuminemia may enhance its and buprenorphine) are unafected by kidney pharmacological efects. Barbiturates Anticholinergic Agents Patients with kidney disease ofen exhibit increased In doses used for premedication, atropine and glyco- sensitivity to barbiturates during induction, even pyrrolate can generally be used safely in patients with though pharmacokinetic profles appear to be renal impairment. The mechanism appears to be an and their active metabolites are normally excreted increase in free circulating barbiturate as a result of in urine, however, the potential for accumulation decreased protein binding. Scopolamine is less a more rapid entry of these agents into the brain by dependent on renal excretion, but its central ner- increasing the nonionized fraction of the drug (see vous system efects can be enhanced by the physi- Chapter 26 ). When the serum renal excretion, and their dose must be reduced potassium is known to be increased or is in doubt, for patients with renal insufciency. Proton pump a nondepolarizing muscle relaxant should be sub- inhibitor dosage does not need to be reduced for stituted. Metoclopramide is levels have been reported in uremic patients follow- partly excreted unchanged in urine and will accu- ing dialysis, signifcant prolongation of neuromus- mulate in kidney failure. Cisatracurium & Atracurium Cisatracurium and atracurium are degraded by plasma ester hydrolysis and nonenzymatic Hofmann elimination. Although patients with mild to moderate renal The elimination of vecuronium is primarily hepatic, impairment do not exhibit altered uptake or distri- but up to 20% of the drug is eliminated in urine. The bution, accelerated induction and emergence may efects of large doses of vecuronium (>0. Rocuronium primarily undergoes tion may be explained by a decrease in the blood:gas hepatic elimination, but prolongation in patients partition coefcient or by a decrease in minimum with severe kidney disease has been reported. Some clinicians avoid sevo- general, with appropriate neuromuscular monitor- furane (with <2 L/min gas fows) for patients with ing, these two agents can be used with few problems kidney disease who undergo lengthy procedures in patients with severe kidney disease. Curare (d-Tubocurarine) Nitrous Oxide Elimination of d-tubocurarine is dependent on Some clinicians omit entirely or limit the use of both renal and biliary excretion; 40–60% of a dose nitrous oxide to 50% concentration in severely anemic of curare is normally excreted in urine. Increasingly patients with end-stage renal disease in an attempt to prolonged efects are observed following repeated increase arterial oxygen content. In the days before intermediate acting neuro- • Search for and correct prerenal and postrenal causes muscular blockers, curare was the nondepolarizing • Review medications and patient-administered paralytic of choice for patients with kidney disease. Although pancuronium is metabo- • Search for and treat acute complications (hyperkalemia, lized by the liver into less active intermediates, its hyponatremia, acidosis, hyperphosphatemia, pulmonary elimination half-life is still primarily dependent on edema) • Search for and aggressively treat infections and sepsis renal excretion (60–80%). Neuromuscular function • Provide early nutritional support should be closely monitored if these agents are used • Provide expert supportive care (management of catheter in patients with abnormal renal function. Reversal Agents 1Reproduced, with permission, from Lameire N, Van Biesen W, Vanholder R: Acute renal failure. Renal excretion is the principal route of elimina- tion for edrophonium, neostigmine, and pyridostig- perfusion; intrinsic kidney failure is usually due to mine. The half-lives of these agents in patients with underlying renal disease, renal ischemia, or nephro- renal impairment are therefore prolonged at least as much as any of the above relaxants, and problems toxins; and postrenal failure is the result of urinary tract obstruction or disruption. Both prerenal and with inadequate reversal of neuromuscular blockade postrenal forms of kidney failure are readily revers- are usually related to other factors (see Chapter 11). Tis diuretic function that results in retention of nitrogenous phase ofen results in very large urinary outputs waste products (azotemia). Kidney failure can be classifed as prerenal, renal, and postrenal, depending on its cause(s), and End-Stage Renal Disease the initial therapeutic approach varies accordingly The most common causes of end-stage renal dis- (see Figure 30–1 and Table 30–3). Neurological Metabolic Neurological Peripheral neuropathy Metabolic acidosis Disequilibrium syndrome Autonomic neuropathy Hyperkalemia Dementia Muscle twitching Hyponatremia Cardiovascular Encephalopathy Hypermagnesemia Intravascular volume depletion Asterixis Hyperphosphatemia Hypotension Myoclonus Hypocalcemia Arrhythmia Lethargy Hyperuricemia Confusion Hypoalbuminemia Pulmonary Seizures Hypoxemia Hematological Coma Anemia Gastrointestinal Cardiovascular Platelet dysfunction Ascites Fluid overload Leukocyte dysfunction Hematological Congestive heart failure Endocrine Anemia Hypertension Glucose intolerance Transient neutropenia Pericarditis Secondary Residual anticoagulation Arrhythmia hyperparathyroidism Hypocomplementemia Conduction blocks Hypertriglyceridemia Metabolic Vascular calcification Hypokalemia Accelerated Skeletal Osteodystrophy Large protein losses atherosclerosis Periarticular calcification Skeletal Pulmonary Osteomalacia Hyperventilation Skin Hyperpigmentation Arthropathy Interstitial edema Myopathy Alveolar edema Ecchymosis Pleural effusion Pruritus Infectious Peritonitis Gastrointestinal Transfusion-related hepatitis Anorexia Nausea and vomiting Delayed gastric emptying Hyperacidity contributing to hypotension during dialysis include Mucosal ulcerations the vasodilating efects of acetate dialysate solutions, Hemorrhage autonomic neuropathy, and rapid removal of fuid. Adynamic ileus The interaction of white cells with cellophane-derived dialysis membranes can result in neutropenia and leukocyte-mediated pulmonary dysfunction leading polycystic kidney disease. The majority of patients who do kalemia, hyperphosphatemia, hypocalcemia, hyper- not undergo renal transplantation receive hemodialy- magnesemia, hyperuricemia, and hypoalbuminemia, sis three times per week, and there are complications typically develop in patients with kidney failure. Water and sodium retention can result in worsen- Hypotension, neutropenia, hypoxemia, and the dis- ing hyponatremia and extracellular fuid overload, equilibrium syndrome are generally transient and respectively. Hypernatremia and hypokalemia are activity as well as decreased platelet adhesiveness uncommon complications. Patients who have recently under- Hyperkalemia is a potentially lethal conse- gone hemodialysis may also have residual antico- quence of kidney failure (see Chapter 49). Cardiovascular less than 5 mL/min, but it can also develop rapidly Cardiac output increases in kidney failure to main- in patients with higher clearances in the setting of tain oxygen delivery due to decreased blood large potassium loads (eg, trauma, hemolysis, infec- oxygen-carrying capacity. Symptoms of hypocalcemia of the alveolar–capillary membrane may also be a rarely develop unless patients are also alkalotic. Arrhythmias, includ- tissue protein and readily develop hypoalbumin- ing conduction blocks, are common, and may be emia. Anorexia, protein restriction, and dialysis are related to metabolic abnormalities and to deposi- contributory. Hematological pericarditis may develop in some patients, who may Anemia is nearly always present when the creatinine be asymptomatic, may present with chest pain, or clearance is below 30 mL/min. Hypovolemia may occur secondary to ofen difcult to maintain hemoglobin concentra- excessive fuid removal during dialysis. Secondary hyperpara- Fluid overload thyroidism in patients with chronic kidney failure Hyperkalemia can produce metabolic bone disease, with osteope- Severe acidosis nia predisposing to fractures. Abnormalities in lipid Metabolic encephalopathy metabolism frequently lead to hypertriglyceride- Pericarditis Coagulopathy mia and contribute to accelerated atherosclerosis. Refractory gastrointestinal symptoms Increased circulating levels of proteins and polypep- Drug toxicity tides normally degraded by the kidneys are ofen present, including parathyroid hormone, insulin, glucagon, growth hormone, luteinizing hormone, ofen used when patients are too hemodynami- and prolactin. Gastrointestinal Patients with chronic kidney failure commonly Anorexia, nausea, vomiting, and adynamic ileus are present to the operating room for creation or revi- commonly associated with uremia. Hypersecretion sion of an arteriovenous dialysis fstula under local of gastric acid increases the incidence of peptic or regional anesthesia. However, regardless of the ulceration and gastrointestinal hemorrhage, which intended procedure or the anesthetic employed, one occurs in 10–30% of patients.
The voice quality is not important silagra 50 mg mastercard erectile dysfunction drugs forum, and the patient has tumor is limited to one vocal fold; there is neither a T1 or T2 lesion that does not involve the anterior mobility impairment nor infiltration of the supra- or commissure 100mg silagra with visa effective erectile dysfunction drugs, transoral laser excision is a good op- subglottis purchase silagra 100 mg online erectile dysfunction hypothyroidism. However, voice quality after transoral laser resent the most important pretreatment assessments excision is directly related to the extent of resec- of early glottic cancer. For example, involvement of the laser transoral excision functional results are simi- paraglottic space, the anterior commissure, or the sub- lar. Open partial laryngectomy has slightly poorer glottis correlates with a higher local recurrence rate in functional results than either laser excision or ra- glottic carcinoma treated with radiotherapy. T1 glottic carcinoma treated with radiotherapy, tumor Long-term follow-up is necessary to detect re- volume is correlated with local control. Indeed, surgical salvage was considered to be possible only with total laryn- gectomy, but partial laryngectomy as salvage sur- ■ Approach gery for radiation failures is possible, essentially in T1 lesions. In the Mendenhall series, 19 of the 291 Because of his occupation, the patient attached patients treated for a T1 lesion experienced local great importance to functional results; therefore, ra- recurrence; seven patients underwent salvage hemi- diotherapy would be the preferred modality. In the Discussion Rodriguez-Cuevas series, recurrences were salvaged The goal of the treatment is to cure with the best with partial laryngectomy in half of the patients achievable functional result and with no serious with acceptable functional results. The selection of a complications, so the technique must be adapted to salvage surgical procedure after radiotherapy (total each patient. Arytenoid fixation, subglottic infiltration, and can be treated with equal success with open interarytenoid invasion, pre-epiglottic space inva- partial laryngectomy, transoral laser excision, or ra- sion, or extralaryngeal spread remain contraindica- diotherapy. Open partial laryngectomy produces tions to partial laryngectomy; patients must have cure rates ranging from 90% to 95% for T1 glottic limited comorbidities and good pulmonary func- carcinoma and 70% to 90% for T2 glottic carci- tion. Transoral laser excision is a safe and effective be done with minimal morbidity and a short hospi- method. Local control rates range from 80% to 90% tal stay, whereas more extended procedures, such as for T1 lesions and 70% to 85% for T2 lesions. As for radiotherapy, T1 and T2 lesions with anterior commissure involvement have low Case Continued rates of local control. After radiotherapy, local con- trol is around 90% for T1 lesions and 80% for T2 le- The patient tolerates radiation well except for sions. Several factors correlate with lower local con- complaining of dry mouth and hoarseness of voice trol: T stage, prolonged overall treatment time, initially. Repeat endoscopy at 3 months shows no anterior commissure involvement, poor histologic evidence of disease. In the series for local recurrence and for a new upper aerodiges- by Reddy and colleagues, local control was 88% tive tract primary cancer. Predicting the local outcome of glottic cell carcinoma after definitive radia- The risk of new primary cancer related to tobacco is tion therapy: value of computed tomography determined tumor parameters. T1-T2 squamous small tumors, where the risk of a new primary ex- cell carcinoma of the glottic larynx treated with radiation ceeds the risk of recurrence. Management in patients who continue smoking, compared with of T1-T2 glottic carcinomas. A high importance must be local control and survival of patients with T1 glottic cancer. Partial laryngec- tomy as salvage surgery for radiation failures in T1-T2 laryn- geal cancer. Radiotherapy for patients with laryngeal cancers (T1-T2 N0): surgery or irradiation? Examination reveals good denture status, and flexible nasopharyngoscopic examination demonstrates an ulcerative and infiltrative lesion about 1. The apex of the pyriform sinus as well as the posterior part of the aryepiglottic fold are free of tumor. Because the apex is free, partial laryn- gopharyngectomy is feasible; in addition, only the very upper part of the medial wall of the pyriform sinus is involved, allowing a supraglottic resection sparing the arytenoid. Partial salvage surgery is less frequently fea- fold and reaching the thyrohyoid membrane with- sible for hypopharyngeal than for laryngeal tumors out extending through it. The inferior part of the pyriform ation failure (infiltrative and ulcerative tumor), due sinus is free and the larynx is mobile. There are no to the inferior extension of the tumor and its close suspicious enlarged cervical lymph nodes. For this patient, the chances of locore- gional cure are high, and the main risk is the Actually, there are very few differential diagnoses in appearance of a second primary tumor that often such a situation. An exclusive a tuberculosis ulcer, but these lesions are most often surgical treatment would keep open any other localized on the posterior part of the pharyngolar- option for the treatment of a second head and neck ynx. Laser endoscopic surgery is another surgical option, though in this case the endoscopic accessi- bility of the tumor was not sufficiently satisfactory Case Continued to facilitate such an approach. The panendoscopy begins with a complete explo- ration of the esophagus and of the trachea and main ■ Surgical Approach bronchi. The pharyngolar- A tracheotomy is performed, and a feeding tube is ynx is explored directly and with rigid 30 degree and placed through the nasal cavity. A supraglottic hemipharyngolaryngectomy diameter, of the upper part of the pyriform sinus is performed, removing half the hyoid bone, the growing down, but without extension to, the apex. Macroscopic evaluation of the specimen reveals satisfactory margins and no metastases to No postoperative irradiation or chemotherapy is the lymph nodes, to be confirmed by the pathology necessary. Psychological support for quitting tobac- examination before deciding on an adjuvant co and alcohol consumption should be provided. Supraglottic hemilaryn- Case Continued gopharyngectomy plus radiation for the treatment of early At the conclusion of the procedure, the patient is lateral margin and pyriform sinus carcinoma. Pharyngeal walls, specimen contained 23 lymph nodes, all free of hypopharynx and larynx. She has smoked 20 cigarettes per day for more than 20 years, but had ceased in the 3 months prior to her presentation. She denies any throat pain, dysphagia, bleeding, or weight loss and has noticed no recent voice change. Physical examination reveals a mass at least 3 cm in diameter, deep to the anterior border of the sternomastoid muscle with no additional evidence of adenopathy. Inspection of the oral cavity and oropharynx and flexible nasopharyngoscopy reveal no obvious abnormality. Differential Diagnosis A lateral neck mass presenting in an older patient, particularly one who smokes, should be considered metastatic carcinoma in a cervical lymph node Figure 6. Other metastatic tumors would include poorly differenti- ated or undifferentiated carcinomas, adenocarci- noma from head and neck or infraclavicular pri- maries, thyroid carcinoma, and melanoma or other cutaneous malignancies. Less commonly, a lateral neck mass may be a primary tumor of the salivary gland or thyroid, or a primary lymphoid tumor. Rarely, this may be the presentation of a primary or metastatic bone or soft tissue sarcoma. A finding of adenocarcinoma would prompt further imaging of the thyroid, breast, and gastroin- Case Continued testinal tract. Biopsies should be directed by clinical and imaging Recommendation findings and by the nature and location of the The patient is advised to have examination under metastasis in the neck. In at least one series, 10% of these tonsil tumors were found in the tonsil contralateral to the presenting neck mass; ■ Approach therefore, bilateral tonsillectomy has been recom- mended.
Hepatic function is appraised simply by routine allowed only small (3 cm) lesions to be ablated order silagra line erectile dysfunction free treatment. The logic behind regional because of proximity to hilar vasculature or biliary chemotherapy is that anticancer drugs may be deliv- structures obviating adequate resection margins buy generic silagra pills erectile dysfunction vasectomy, ered directly to the tumor at high concentrations cheap silagra 100mg otc erectile dysfunction specialists, because of multifocal liver involvement, or because while minimizing systemic toxicity. There is no ies have demonstrated that two thirds or more of the Case 44 191 blood supply to hepatic metastases is from the findings on palpation and visual inspection. It However, other trials have not achieved as promis- is difficult to ensure adequate ablation, even with ing results, and meta-analysis suggests that the sur- multiple passes, for larger lesions. If carcinomatosis is encountered, the operation is terminated before proceeding further. In the absence of palpable disease outside the liver, the Case Continued incision is extended to a bilateral subcostal incision The patient undergoes exploration via a subcostal with a vertical extension in the midline to the ster- chevron incision. The hepato- gastric and hepatoduodenal ligaments are inspected for the presence of accessory/replaced left or right hepatic arteries. Laparoscopy in conjunction with laparoscopic ultrasound offers an alternative to open exploration. In some cases, laparoscopic staging may be limited by adhesions or less complete access to the liver. However, given the much-reduced morbidity, laparoscopy is an attractive alternative in patients with questionably resectable disease or who are poor operative candidates. This was bases analysis of the total fraction of the genome felt to be consistent with another metastatic deposit. Hepatic insufficiency, the most ominous complication, occurs in 1% to 5% of cases. Discussion Other serious complications include hemorrhage (1% Recent series of metastasectomy for hepatic liver to 3%), biliary leak or fistula (3% to 4%), and peri- metastases report 5-year survival rates of 30% to hepatic abscess (1% to 9%). Several investigators have sought to define plications, including myocardial infarction, pleural prognostic indicators that would allow selection of effusion requiring thoracostomy, pneumonia, and patients who are most likely to benefit from resec- pulmonary embolism, occur in 5% to 10% of cases. The most powerful clinical predictors of out- Unfortunately, cancer recurs in approximately come are consistently found to be the number of 50% to 75% of patients after liver resection. Half of metastases and the presence of a positive surgical those recurrences are in the liver. Additional factors predictive of recurrence patients may be candidates for repeat hepatectomy are the presence of extrahepatic disease, a node- following recurrence. The clinical evaluation and positive primary tumor, a short ( 12 months) eligibility for re-resection are essentially the same as interval between the primary tumor and the for initial hepatectomy. Several centers have reported Case 44 193 5-year survival following re-resection that approxi- Suggested Readings mates survival after the initial liver resection. Recurrence and outcomes dependent on whether the patient is potentially a following hepatic resection, radiofrequency ablation, and candidate for re-resection. If so, liver function tests, combined resection/ablation for colorectal liver metastases. Patients who hepatic resection is superior to wedge resection as an onco- are not candidates for further surgery undergo fur- logic operation for colorectal liver metastases. Clinical score for predicting In the last 5 years, medical therapy for advanced recurrence after hepatic resection for metastatic colorectal colorectal cancer has changed dramatically. A systematic review of hepatic artery patients who benefit from aggressive surgical inter- chemotherapy after hepatic resection of colorectal cancer vention. Survival after resec- may ultimately benefit from resection of hepatic tion of multiple hepatic colorectal metastases. Physical examination is unremarkable; the patient was in a good condition with normal blood pressure and stools. Differential Diagnosis Differential diagnoses for intrahepatic tumors in- clude hemangiomas, hepatocarcinomas, metastases of thyroid and kidney cancers, multiple nodular hy- perplasias, and polyadenomas, even when there is Figure 45. There are sev- eral ileal and lymphatic foci in the right iliac region; There is increased uptake of radionucleotide by the multiple foci are identified in the liver. Carcinoid syndrome can be Diagnosis treated with somatostatin, which can be effective in 50% to 80% of cases and may also stabilize the dis- The diagnosis is carcinoid tumor with lymphatic ease. Pretreatment with somatostatin is also effec- metastases in the ileocecal region and liver carcinoid tive in avoiding carcinoid crisis that can be induced tumor metastases. Generally, the goal of treatment in patients ■ Approach with metastatic carcinoid syndrome is palliation. Carcinoid tumors are notable for an indolent For healthy patients, an aggressive surgical ap- course, and therefore surgery is the most important proach that includes resection or ablation of the aspect in achieving palliation even with advanced hepatic metastases is appropriate. Palliation can and metastatic disease where there is no hope for also be achieved with hepatic artery chemoem- cure. Case 45 197 evaluate the liver with ultrasound, which also guides the resection and ablative therapy. Recommendation The primary tumor is resected, and 25 carcinoid Surgical resection of the primary lesions and the he- liver metastases are treated (14 lesions are removed patic metastases is proposed. The first step of the proce- mary tumor was located in the deep layer of the mu- dure is to remove the tumor located at the ileocecal cosa and submucosa. The other macroscopic lesions junction with the adjacent mesentry to eliminate exhibited characteristic features of metastases. The majority of midgut carcinoid tumors found outside the appendix arise in the ileum or cecum, Discussion and remain clinically silent until the development Carcinoid tumors arise from enterochromaffin cells of carcinoid syndrome and/or hepatic metastases. Thus, it is one of the most all 5-year survival rate of those with liver metastases common neuroendocrine tumors of the gut. Hepatic resection and left, liver transplantation can be proposed for multi- transplantation for primary carcinoid tumors of the liver. One of our patients, a 28-year-old woman with liver Schillaci O, Spanu A, Scopinaro F, et al. Somatostatin receptor scintigraphy in liver metastasis detection from gastroen- metastases of a midgut carcinoid tumor, received a teropancreatic neuroendocrine tumors. Management of neuroen- resections, there is a real risk of postoperative liver docrine liver metastases. Radiofrequency can be combined case 46 of the gallbladder, which does not involve the liver. A 66-year-old woman with no significant past med- ical history presents with a 3-day history of right upper quadrant pain. Physical examination reveals no Cholangiogram jaundice, anemia, lymphadenopathy, or specific ab- dominal findings. It does not involve the extrahepatic maximum diameter are very likely to be malignant. The shape of the lesion is another useful hint when discriminating benign from malignant lesions.
Anticholinergic agents produce bronchodila- Bitolterol (Tornalate) + ++++ tion through their antimuscarinic action and may Epinephrine ++++ ++ block refex bronchoconstriction buy silagra 100 mg with visa best rated erectile dysfunction pills. Ipratropium buy cheap silagra 50mg online erectile dysfunction medication online, a congener of atropine that can be given by a metered- Fenoterol (Berotec) + +++ dose inhaler or aerosol buy silagra master card erectile dysfunction age 70, is a moderately efective Formaterol (Foradil) + ++++ bronchodilator without appreciable systemic anti- cholinergic efects. Isoetharine (Bronkosol) ++ +++ Isoproterenol (Isuprel) ++++ — Anesthetic Considerations Metaproterenol (Alupent) A. Preoperative Management Pirbuterol (Maxair) + ++++ The emphasis in evaluating patients with asthma should be on determining the recent course of the Salmeterol (Serevent) + ++++ disease and whether the patient has ever been hospi- Terbutaline (Brethaire) talized for an acute asthma attack, as well as on + +++ ascertaining that the patient is in optimal condition. Patients with poorly controlled asthma or wheezing at the time of anesthesia induction have a higher risk cardiac efects, but are ofen not particularly selec- of perioperative complications. A thorough history and physical examination esterase, the enzyme responsible for the breakdown are of critical importance. Com- complex and include catecholamine release, block- plete resolution of recent exacerbations should be ade of histamine release, and diaphragmatic stimu- confrmed by chest auscultation. Oral long-acting theophylline preparations quent or chronic bronchospasm should be placed on are used for patients with nocturnal symptoms. A chest radio- Unfortunately, theophylline has a narrow therapeu- graph identifes air trapping; hyperinfation results tic range; therapeutic blood levels are considered to in a fattened diaphragm, a small-appearing heart, be 10–20 mcg/mL. Arterial blood gases may be useful in man- should be avoided or given very slowly when used. Hypoxemia and hypercapnia are The goal of any general anesthetic is a smooth induc- typical of moderate and severe disease; even slight tion and emergence, with anesthetic depth adjusted hypercapnia is indicative of severe air trapping and to stimulation. The choice of induction agent is less important, Some degree of preoperative sedation may be if adequate depth of anesthesia is achieved before desirable in asthmatic patients presenting for elec- intubation or surgical stimulation. Tiopental may tive surgery—particularly in patients whose disease occasionally induce bronchospasm as a result of has an emotional component. Propofol and etomi- epines are the most satisfactory agents for premedi- date are suitable induction agents; propofol may cation. Ketamine has bron- given unless very copious secretions are present or chodilating properties and is a good choice for if ketamine is to be used for induction of anesthesia. Ketamine should probably not be used in not efective in preventing refex bronchospasm fol- patients with high theophylline levels, as the com- lowing intubation. The use of an H - blocking2 agent bined actions of the two drugs can precipitate seizure (such as cimetidine, ranitidine, or famotidine) is the- activity. Halothane and sevofurane usually provide oretically detrimental, since H -receptor 2 activation the smoothest inhalation induction with bronchodi- normally produces bronchodilation; in the event of lation in asthmatic children. Isofurane and desfu- histamine release, unopposed H1 activation with H2 rane can provide equal bronchodilation, but are not blockade may accentuate bronchoconstriction. Desfurane Bronchodilators should be continued up to is the most pungent of the volatile agents and may the time of surgery; in order of efectiveness, they result in cough, laryngospasm, and bronchospasm. Note that intra- severity of the illness and complexity of the surgical tracheal lidocaine itself can initiate bronchospasm procedure. Supplemental doses should be tapered to if an inadequate dose of induction agent has been baseline within 1–2 days. Administration of an anticholinergic agent may block refex bronchospasm, but causes exces- B. Although succinylcholine may on The most critical time for asthmatic patients under- occasion induce marked histamine release, it can going anesthesia is during instrumentation of the generally be safely used in most asthmatic patients. General anesthesia by mask or regional In the absence of capnography, confrmation of cor- anesthesia will circumvent this problem, but nei- rect tracheal placement by chest auscultation can be ther eliminates the possibility of bronchospasm. Ventilation (T1–T4) and allowing unopposed parasympathetic should incorporate warmed humidifed gases activity. Airfow obstruction during ing light general anesthesia can precipitate bron- expiration is apparent on capnography as a delayed chospasm. Deep extu- bation (before airway refexes return) reduces bronchospasm on emergence. The disorder is strongly associated with cigarette smoking and has a male severity of obstruction is generally inversely related predominance. Severe broncho- 5 2 disease state characterized by airfow limita- spasm is manifested by rising peak inspiratory pres- tion that is not fully reversible. Tidal volumes of limitation of this disease is due to a mixture of small 6–8 mL/kg, with prolongation of the expiratory and large airway disease (chronic bronchitis/bron- time, may allow more uniform distribution of gas chiolitis) and parenchymal destruction (emphy- fow to both lungs and may help avoid air trapping. In many patients, the 3 fested as wheezing, increasing peak airway obstruction has an element of reversibility, presum- pressures (plateau pressure may remain unchanged), ably from bronchospasm (as shown by improvement decreasing exhaled tidal volumes, or a slowly rising in response to administration of a bronchodilator). Other causes With advancing disease, maldistribution of both 4 can simulate bronchospasm: obstruction of ventilation and pulmonary blood fow results in the tracheal tube from kinking, secretions, or an · · areas of low (V/Q) ratios (intrapulmonary shunt), overinfated balloon; bronchial intubation; active · · as well as areas of high (V/Q) ratios (dead space). Chronic Bronchitis should be treated by increasing the concentration of The clinical diagnosis of chronic bronchitis is the volatile agent and administering an aerosolized defned by the presence of a productive cough bronchodilator. Infusion of low dose epinephrine on most days of 3 consecutive months for at least may be needed if bronchospasm is refractory to 2 consecutive years. Emphysema may exist in a centrilobular or Chest radiograph Increased lung Hyperinflation markings panlobular form. The centrilobular (or centriaci- nar) form results from dilatation or destruction of Elastic recoil Normal Decreased the respiratory bronchioles, is more closely associ- Airway resistance Increased Normal to slightly ated with tobacco smoking, and has predominantly increased an upper lobe distribution. The panlobular (or pan- acinar) form results in a more even dilatation and Cor pulmonale Early Late destruction of the entire acinus, is associated with α1-antitrypsin defciency, and has predominantly a bronchitis” may be used when bronchospasm is lower lobe distribution. Recurrent pulmonary infections Loss of the elastic recoil that normally supports (viral and bacterial) are common and ofen associ- small airways by radial traction allows premature ated with bronchospasm. Intrapulmonary shunting is promi- fow limitation with air trapping and hyperinfa- nent, and hypoxemia is common. Signifcant alveolar septa leads to the development of pul- emphysema is more frequently related to cigarette monary hypertension. When dyspneic, patients with emphysema ofen Anesthetic Considerations purse their lips to delay closure of the small airways, which accounts for the term “pink pufers” that is A. Inhaled β -adrenergic2 ago- surements, if available, should be reviewed carefully. Many patients have concomitant the management of these patients than in patients cardiac disease and should also receive a careful car- with asthma. Treatment with systemic corticosteroids short period of intensive preoperative preparation. Patients at greatest risk of complica- frequent treatment with broad-spectrum antibiotics tions are those with preoperative pulmonary func- may be necessary. Patients with possibility that postoperative ventilation may be chronic hypoxemia (Pao2 <55 mm Hg) and pulmo- necessary in high-risk patients should be discussed nary hypertension require low-fow oxygen therapy with both the patient and the surgeon. Both gaseous and particulate When cor pulmonale is present, diuretics are phases of cigarette smoke can deplete glutathione used to control peripheral edema; benefcial efects and vitamin C and may promote oxidative injury to from vasodilators are inconsistent. Cessation of smoking for as little as 24 hr has bilitation may improve the functional status of the theoretical benefcial efects on the oxygen-carrying patient by improving physical symptoms and exer- capacity of hemoglobin; acute inhalation of cigarette cise capacity. A pneumothorax may and nitrogen dioxide, which can lead to formation manifest as hypoxemia, increased peak airway of methemoglobin. Nitrous oxide should be avoided in patients Preoperative chest physiotherapy and lung with bullae and pulmonary hypertension.