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No clear association has been shown between the Parkinson Disease Parkinson disease is a degenerative disorder of the basal ganglia characterized by failure of dopamine secretion that results in diminished inhibition of the extrapyramidal motor system hypertension treatment guidelines jnc 7 order 25mg dipyridamole mastercard. Autonomic dysfunction with orthostatic hypotension arrhythmia yahoo order generic dipyridamole online, excessive salivation blood pressure stroke range generic 25mg dipyridamole visa, and impaired thermoregulation may also occur blood pressure chart bpm generic 100mg dipyridamole with visa. Patients are at risk of pulmonary complications resulting from difficulty swallowing, altered mental status, increased aspiration risk, and ventilatory muscle dysfunction. Standard treatments include levodopa (often combined with carbidopa), anticholinergic agents, bromocriptine, amantadine, and selefiline. Some individuals also undergo implantation of deep brain stimulators to manage their symptoms. Preoperative evaluation focuses on the pulmonary system, signs of dysphagia, and degree of disability. Evidence of significant pulmonary symptoms or possible infection requires chest radiography, pulmonary consultation, and possible delay of the Chapter 38: Preoperative Evaluation 1129 procedure for improvement. Individuals with deep brain stimulators require deactivation of the devices before any procedures in which electrocautery will be used. Abrupt withdrawal of levodopa may exacerbate symptoms (especially dysphagia and chest wall rigidity) or precipitate neuroleptic malignant syndrome. The latter disorder is characterized by autonomic instability, altered mental status, rigidity, and fever. Some medications encountered in the perioperative setting, such as metoclopramide and phenothiazines, may exacerbate symptoms of Parkinson disease by interfering with dopamine. Neuromuscular Junction Disorders Myasthenia gravis is an autoimmune disorder of skeletal muscle neuromuscular junctions that is caused by antibodies against nicotinic acetylcholine receptors (see also Chapter 42). Box 38-15 presents a classification system for myasthenia gravis with increasing numeric classes indicating increasing levels of involvement and debilitation. Patients with myasthenia gravis commonly have other autoimmune diseases, such as rheumatoid arthritis, polymyositis, and thyroid disorders. Because the thymus is located in the anterior mediastinum, thymic enlargement has implications for anesthesia care. Cranial nerve and bulbar involvement are common, with an associated increase in aspiration risk resulting from pharyngeal and laryngeal muscle weakness. Patients are usually treated with thymectomy, anticholinesterase, and immunosuppressant medications. A short-acting anticholinesterase (edrophonium) can help distinguish the two states. Plasmapheresis and intravenous immunoglobulins have been used to treat myasthenic crises and prepare patients for surgery, but they require several days to weeks to produce signs of improvement. Documentation of medication dosages and continuation of medications until the surgical procedure are paramount. Patients treated with steroids need glucose measurement, as well as steroid supplementation in the perioperative period. These tests may also be helpful if patients are being considered for ambulatory surgery, especially in freestanding surgical centers. Even though anticholinesterases may cause bradycardia, salivation, and altered effects of neuromuscular blocking drugs, these agents must be continued in the perioperative period. Lambert-Eaton syndrome is similar to myasthenia gravis, with muscle weakness including oculobulbar involvement and dysautonomia. It is caused by antibodies against voltage-gated calcium channels that result in a decrease in acetylcholine release. Lambert-Eaton syndrome is not associated with thymic abnormalities, but it commonly occurs in patients with malignant diseases, especially small cell lung cancer and gastrointestinal tumors. The other distinguishing feature of this disorder is that the muscle weakness classically improves with activity and is worse after inactivity. Therapies for Lambert-Eaton syndrome are similar to those used for myasthenia gravis. In addition, a selective potassium channel blocker, namely 3,4-diaminopyridine, is used and should be continued perioperatively. Preoperative evaluation and management are similar to those for myasthenia gravis. Muscular Dystrophies and Myopathies Muscular dystrophies and myopathies are inherited disorders that affect the neuromuscular junction. The hallmark of these disorders is progressive skeletal muscle weakness that commonly leads to respiratory failure. Duchenne and Becker muscular dystrophies are X-linked recessive disorders that occur primarily in male patients. Male patients with a family history of either Duchenne or Becker muscular dystrophy should be considered at risk (even when they have not been formally tested), and they require precautions similar to those in patients with diagnosed disease. Female carriers of the abnormal gene may have dilated cardiomyopathy despite having no other manifestations of the disease. The focus of the preoperative history is on eliciting details pertaining to palpitations, dyspnea, chest pain, syncope, orthopnea, dependent edema, aspiration, and pneumonia. Facioscapulohumeral muscular dystrophy (also known as faciohumeroscapular or Landouzy-Dejerine muscular dystrophy) is an autosomal dominant disorder that affects both sexes and causes a slow, progressive weakness of muscles in the shoulders and face. Cardiomyopathy occurs much less frequently than in other dystrophies, but arrhythmias have been reported. Limb-girdle dystrophies have a variable genetic inheritance pattern and primarily affect the muscles of the shoulders and pelvis. Conduction abnormalities are present in some patients, although frank cardiomyopathies are less frequent. The preoperative evaluation is largely similar to that described previously for Duchenne muscular dystrophy.

Blanchard C blood pressure medication used for sleep dipyridamole 25mg free shipping, Mathonnet M arteria apendicular 100 mg dipyridamole sale, Sebag F blood pressure medication side effects dipyridamole 25 mg generic, et al: Surgery for "asymptomatic" mild primary hyperparathyroidism improves some clinical symptoms postoperatively heart attack photo cheap dipyridamole line, Eur J Endocrinol 169:665-672, 2013. Prys-Roberts C: Phaeochromocytoma: recent progress in its management, Br J Anaesth 85:44-57, 2000. Zakowski M, Kaufman B, Berguson P, et al: Esmolol use during resection of pheochromocytoma: report of three cases, Anesthesiology 70:875, 1989. Weksler N, Klein M, Szendro G, et al: the dilemma of immediate preoperative hypertension: to treat and operate, or to postpone surgery Aronson S, Boisvert D, Lapp W: Isolated systolic hypertension is associated with adverse outcomes from coronary artery bypass grafting surgery, Anesth Analg 94:1079-1084, 2002. I: cardiovascular responses of treated and untreated patients, Br J Anaesth 43:122, 1971. Coriat P, Richer C, Douraki T, et al: Influence of chronic angiotensin-converting enzyme inhibition in anesthetic induction, Anesthesiology 81:299, 1994. Turan A, You J, Shiba A, et al: Angiotensin converting enzyme inhibitors are not associated with respiratory complications or mortality after noncardiac surgery, Anesth Analg 114:552-560, 2012. Five-year survival according to age and clinical cardiac status, Cleve Clin Q 53:133-143, 1986. Five-year survival according to sex, hypertension, and diabetes, Cleve Clin Q 54:15-23, 1987. Godet G, Riou B, Bertrand M, et al: Does preoperative coronary angioplasty improve perioperative cardiac outcome Leibowitz D, Cohen M, Planer D, et al: Comparison of cardiovascular risk of noncardiac surgery following coronary angioplasty with versus without stenting, Am J Cardiol 97:1188-1191, 2006. Nasser M, Kapeliovich M, Markiewicz W: Late thrombosis of sirolimus-eluting stents following noncardiac surgery, Catheter Cardiovasc Interv 65:516-519, 2005. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines: endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons, Circulation 118:887-889, 2008. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Patients with Valvular Heart Disease), Circulation 98:1949-1984, 1998. Developed in collaboration with the Society of Cardiovascular Anesthesiologists: endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons Circulation 114:e84-e231, 2006. Augmentation of systolic blood pressure during carotid endarterectomy: effects of phenylephrine versus light anesthesia and of isoflurane versus halothane on the incidence of myocardial ischemia, Anesthesiology 69:846, 1988. Erikssen G, Thaulow E, Sandvik L, et al: Haematocrit: a predictor of cardiovascular mortality Lette J, Waters D, Lapointe J, et al: Usefulness of the severity and extent of reversible perfusion defects during thallium-dipyridamole imaging for cardiac risk assessment before noncardiac surgery, Am J Cardiol 64:276, 1989. American Society of Anesthesiologists Task Force on Pulmonary Artery Catheterization: Practice guidelines for pulmonary catheterization: a report by the American Society of Anesthesiologists Task Force on Pulmonary Artery Catheterization, Anesthesiology 78:380, 1993. International Multicentre Trial: Prevention of fatal postoperative pulmonary embolism by low doses of heparin, Lancet 2:45, 1975. Collins R, Scrimgeour A, Yusuf S, Peto R: Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin, N Engl J Med 318:1162, 1988. Gallus A, Raman K, Darby T: Venous thrombosis after elective hip replacement: the influence of preventive intermittent calf compression and on surgical technique, Br J Surg 70:17, 1983. Rock P, Passannante A: Preoperative assessment: pulmonary, Anesthesiol Clin North Am 22:77-91, 2004. Qaseem A, Snow V, Fitterman N, et al: Risk assessment for and strategies to reduce perioperative pulmonary complications for patients undergoing noncardiothoracic surgery: a guideline from the American College of Physicians, Ann Intern Med 144:575-580, 2006. A retrospective study of patients admitted to hospital with a first episode of myocardial infarction or unstable angina, Br Heart J 62:16, 1989. Ernst E, Matrai A: Abstention from chronic cigarette smoking normalizes blood rheology, Atherosclerosis 64:75, 1987. Nakagawa M, Tanaka H, Tsukuma H, Kishi Y: Relationship between the duration of the preoperative smoke-free period and the incidence of postoperative pulmonary complications after pulmonary surgery, Chest 120:705-710, 2001. Lieberman P: Anaphylactic reactions during surgical and medical procedures, J Allergy Clin Immunol 110(Suppl):S64-S69, 2002. Roberts R: Differential diagnosis of sleep disorders, non-epileptic attacks and epileptic attacks, Curr Opin Neurol 11:135-139, 1998. Skoog I, Nilsson J, Palmertz B, et al: A population-based study of dementia in 85-year-olds, N Engl J Med 328:153, 1993. Lyager S, Wernberg M, Rajani N, et al: Can postoperative pulmonary conditions be improved by treatment with the BartlettEdwards incentive spirometer after upper abdominal surgery Mittman C: Assessment of operative risk in thoracic surgery, Am Rev Respir Dis 84:197, 1961. Subtypes, familial occurrence and cross reactivity with tartrazine, J Allergy Clin Immunol 56:215, 1975. Centers for Disease Control and Prevention: Cancer statistics for the United States. Aisner J: Extensive-disease small-cell lung cancer: the thrill of victory the agony of defeat, J Clin Oncol 14:658, 1996. Wei H, Liang G, Wang Q, et al: the common inhalational anesthetic isoflurane induces apoptosis via activation of inositol 1,4,5-trisphosphate receptors, Anesthesiology 108:251-260, 2008. Zhang B, Dong Y, Zhang G, et al: the inhalation anesthetic desflurane induces caspase activation and increases amyloid beta-protein levels under hypoxic conditions, J Biol Chem 283:11866-11875, 2008.

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In the group studied arteria tibialis posterior effective dipyridamole 100 mg, 268 patients had major complications blood pressure 7050 cheap dipyridamole 25mg without prescription, 67 patients died blood pressure chart graph purchase dipyridamole 100mg free shipping, and 16 patients suffered persistent coma blood pressure chart numbers purchase 100mg dipyridamole with visa. Death was solely related to anesthesia in 1 in 13,207 procedures and partially related in 1 in 3810 (Table 37-5). A key finding of the French survey was that postanesthesia respiratory depression was the leading principal cause among cases of death and coma that were solely attributable to anesthesia. Moreover, almost all the patients who had had respiratory depression leading to a major complication had received narcotics, as well as neuromuscular blocking drugs, but they had not received anticholinesterase medications for reversal of the agents. Despite these observations, the low rates of anesthesia-attributable mortality documented in the French study offered compelling evidence of improvements in anesthesia safety. Such findings were reinforced by the work of Tikkanen and Hovi-Viander,44 who studied deaths associated with anesthesia and surgery in Finland and compared the results in 1986 with those collected in 1975. Mortality related to anesthesia decreased during the 9-year period; the incidence of anesthesiarelated mortality was 0. The next major step forward in efforts to understand the risks of anesthesia came through the pioneering work of Lunn45 in the United Kingdom. Reporting on 197 fatalities occurring within 6 days after anesthesia during 1981, Lunn found 43% of the deaths to have been unrelated to anesthesia, 41% to be partly attributable to anesthesia, and 16% to be totally attributable to anesthesia. Unique to this study was the establishment of "crown privilege" by the government to protect data submitted to the enquiry from further subpoena. Anesthesia was considered the sole cause of death in only three individuals, for a rate of 1 in 185,000 cases, and anesthesia was contributory in 410 deaths, for a rate of 7 in 10,000 cases (Table 37-6). Notably, of the 410 perioperative deaths, gastric aspiration was identified in 9 cases and cardiac arrest in 18 cases. The surgeon was a consultant in only 19% of the orthopedic cases, as compared with 47% overall. Contributing factors for anesthesiologists and surgeons tended to be failure to act appropriately with existing knowledge (rather than a lack of knowledge), equipment malfunction, fatigue, and inadequate supervision of trainees, particularly in off-hours shifts (Table 37-8). Pedersen and colleagues46 performed a series of studies in the late 1980s in Denmark to examine anesthesia-related factors contributing to serious morbidity or mortality. Complications in the 43 patients, in order of incidence, included cardiovascular collapse in 16 (37%), severe postoperative headache after regional anesthesia in 9 (21%), and awareness under anesthesia in 8 (19%). In particular, the authors found anesthesia to be the underlying cause of death in 34 patients each year in the United States and a contributing factor in another 281 deaths annually, resulting in a 97% decrease in anesthesia-related death rates since the 1940s. More recent studies conducted on the local and national level have sought to emphasize room for improvement in anesthesia-related mortality. Chapter 37: Risk of Anesthesia 1063 contributed) occurred in 1 in every 12,641 procedures in the suburban setting and in 1 in 13,322 procedures in the urban setting. In reviewing data over the previous decade, Lagasse estimated that anesthesia-related mortality had remained stable at approximately 1 death per 13,000 procedures. Notably, the authors identified important gaps in the perioperative management of these patients. A minority of the high-risk patients were monitored using an arterial line, a central line, or cardiac output monitoring; still more concerning was their observation that 48% of all high-risk patients who died were never admitted to a critical care unit for postoperative management. Similar findings were obtained in another study of surgical outcomes conducted across 28 European countries between April 4 and April 11, 2011. Such patterns, which the authors describe as a "systematic failure in the process of allocation of critical care resources" in Europe, highlight the potential importance of "rescue"-the prevention of mortality among patients who experience postoperative complications8-in determining the outcomes of surgical care. Further, to the extent that critical care use among patients who die after surgery is higher in the United States than in the United Kingdom,51 such differences may offer insight into potential reasons for earlier observations of lower risk-adjusted postoperative mortality among American versus British surgical patients. Finally, more recent work has sought to go beyond efforts to quantify the contribution of anesthesia per se to overall operative risk to explore how anesthesia providers might be able to improve outcomes among high-risk patients; in essence asking not "how safe is anesthesia In contrast to efforts to estimate the mortality attributable to anesthesia per se, studies of intraoperative cardiac arrest may offer a broader picture of the potential hazards of anesthesia by examining an adverse outcome that is far more common than mortality yet remains highly consequential for long-term outcomes. A review of the published literature and analysis of current original data, Anesthesiology 97:1609, 2002. These studies offer a range of perspectives on the incidence of intraoperative cardiac arrest and the causes of such events. For example, Keenan and Boyan53 studied the incidence and causes of cardiac arrest related to anesthesia at the Medical College of Virginia between 1969 and 1983. A total of 27 cardiac arrests occurred during 163,240 procedures, for an incidence of 1. Pediatric patients had a threefold higher risk of arrest than did adults, and emergency cases had a sixfold greater risk. Importantly, specific errors in anesthesia management could be identified in 75% of the cases; most common among these were inadequate ventilation and overdose of an inhaled anesthetic. Notably, the investigators identified progressive bradycardia preceding all but 1 arrest, suggesting that early identification and treatment may prevent complications. Similar findings were reported by Olsson and Hallen54 who studied the incidence of intraoperative cardiac arrest at the Karolinska Hospital in Stockholm, Sweden, from 1967 to 1984. The most common causes of anesthesia-related cardiac arrest were inadequate ventilation (27 patients), asystole after succinylcholine (23 patients), and postinduction hypotension (14 patients). Also of note is the finding that the incidence of cardiac arrest decreased over the study period. Eleven cardiac arrests related to anesthesia were identified in 101,769 anesthesia procedures (1.

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Dextrose and sterile water are commonly added to render local anesthetic solutions either hyperbaric or hypobaric hypertension blood pressure dipyridamole 100 mg online, respectively blood pressure medication compliance generic 25 mg dipyridamole amex. The clinical importance of baricity is the ability to influence the distribution of local anesthetic spread based on gravity blood pressure higher in right arm buy dipyridamole australia. Hyperbaric solutions will preferentially spread to the dependent regions of the spinal canal blood pressure zinc order discount dipyridamole online, whereas hypobaric solutions will spread to nondependent regions. For example, the administration of hyperbaric local anesthetic to patients in the lateral decubitus position will result in a preferential anesthetic effect on the dependent side, whereas the opposite is true for the administration of a hypobaric solution. A thoughtful understanding of the natural curvatures of the vertebral column can help predict local anesthetic spread in patients placed in the horizontal supine position immediately after intrathecal administration. Hyperbaric local anesthetics injected, while sitting, at the L3-4 or L4-5 interspace will spread with gravity from the height of the lumbar lordosis down toward the trough of the thoracic kyphosis in the horizontal supine position, resulting in a higher level of anesthetic effect than isobaric or hypobaric solutions. Nevertheless, increasing temperature decreases density of a solution and warming of local anesthetic solution to body temperature, therefore making it more hypobaric, increases the block height in patients who remain seated for several minutes after injection. The choice of local anesthetic itself does not influence spread if all other factors are controlled. However, opioids do seem to increase mean spread,91,99 possibly as a result of pharmacologic enhancement at the extremes of the spread where the local anesthetic block alone would have been subclinical. Within the range of "normal-sized" adults, patient height does not seem to affect the spread of spinal anesthesia. This is likely because the length of the lower limb bones rather than the vertebral column contributes most to adult height. A correlation has been found between the vertebral column length and local anesthetic spread102 and, at extremes of height, consideration should be given to altering the dose accordingly. This has indeed been demonstrated using hypobaric solutions,103,104 which are characterized by more variable spread anyway, but not hyperbaric solutions103,105 (see Chapter 71). Although this may affect relative baricity of local anesthetics, the clinical variation in spread is probably unimportant. Further, the nerve roots appear more sensitive to local anesthetic in the aged population. In the lateral position, the broader shoulders of males relative to their hips make the lateral position slightly more head-up. The reverse is true in females who have a slightly headdown tilt in the lateral position compared with males. Despite this, there is little objective data that males have a slightly less cephalad spread than females in the lateral position. Scoliosis, although it possibly makes insertion of the needle more difficult, will have little effect on local anesthetic spread if the patient is turned supine. Kyphosis, however, in a supine patient may affect the spread of a hyperbaric solution. Procedure Factors Patient position, needle type and alignment, and the level of injection are each procedure-related factors that can affect block height. Combined with the baricity and local anesthetic dose, patient position is the most important factor in determining the block height. When larger hyperbaric doses are administered, however, the block can still extend cephalad despite maintaining the sitting position for a prolonged period of time. With hypobaric solutions, cephalad alignment of the orifice of Whitacre, but not Sprotte, needles produces greater spread. When directing the needle orifice to one side (and using hyperbaric anesthetic), a more marked unilateral block is achieved again when using a Whitacre, rather than a Quincke, needle. Most studies have demonstrated that, even when the difference is only one interspace more cephalad, the block height is greater119-122 when using isobaric bupivacaine. The level of injection does not appear to influence the spread of hyperbaric solutions. Other maneuvers that do not appear to affect block height are coughing and straining after local anesthetic injection. For example, the duration of surgical anesthesia is less than the time for complete block resolution. In addition, surgical anesthesia depends on the surgical site because anesthesia is more prolonged at the lower lumbar and sacral levels than at those more cephalad from where the block regresses first. Duration is affected primarily by the dose,97,125 the intrinsic properties of the local anesthetic (which affect elimination from the subarachnoid space), and the use of additives (if applicable). However, it is not commonly used because of a more frequent failure rate than lidocaine, significantly more nausea, and a slower time to recovery. Its initial popularity stemmed from its rapid metabolism by pseudocholinesterase, which translated into minimal systemic or fetal effects in the setting of epidural labor analgesia. However, its reputation as a spinal anesthetic has been tarnished because of reports of neurologic injury associated with the preservative once used in older preparations of the drug136-139 (see Complications, discussed later). Recently, interest in chloroprocaine has increased for use in spinal anesthesia for ambulatory surgery (see Chapter 89). Modern, preservative-free preparations of chloroprocaine administered in small doses (30 to 60 mg) produce reliable, short-duration spinal anesthesia,126 with a faster recovery time than procaine, lidocaine, and bupivacaine. Articaine is a relatively novel amide local anesthetic that also has an ester linkage. It has been widely used since 1973 for dental nerve blocks with a good safety profile.

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The spinal cord ends at the level of L1-L2 and so needle insertion above this level should be avoided lowering blood pressure without medication quickly dipyridamole 25 mg overnight delivery. The intercristal line is the line drawn between the two iliac crests and traditionally corresponds to the level of the L4 vertebral body or the L4-L5 interspace blood pressure medication sore joints discount dipyridamole 25mg with visa, but the reliability of this landmark is questionable as demonstrated by recent ultrasonography studies blood pressure medication and coenzyme q10 cheap dipyridamole 25 mg with mastercard. The needle prehypertension eyes 25 mg dipyridamole amex, with its bevel parallel to the midline, is advanced slowly to heighten the sense of tissue planes traversed and to prevent skewing of nerve roots, until the characteristic change in resistance is noted as the needle passes through the ligamentum flavum and dura. The paramedian approach exploits the larger "subarachnoid target" that exists if a needle is inserted slightly lateral to the midline. The paramedian approach may be especially useful in the setting of diffuse calcification of the interspinous ligament. The most common error when using the paramedian technique is that the needle entry site is placed too far off midline, which makes the vertebral laminae barriers to insertion of the needle. In the paramedian approach, a skin wheal is raised 1 cm lateral and 1 cm caudad to the corresponding spinous process. The spinal introducer and needle are next inserted 10 to 15 degrees off the sagittal plane in a cephalomedial plane. Similar to the midline approach, the most common error is to angle the needle too far cephalad on initial insertion. Nevertheless, if the needle contacts bone, it is redirected slightly in a cephalad direction. If bone is again contacted, but at a deeper level, the slight cephalad angulation is continued because it is likely that Chapter 56: Spinal, Epidural, and Caudal Anesthesia 1701 A B Figure 56-5. A, the palpating fingers are "rolled" in a side-to-side and a cephalad-to-caudad direction to identify the interspinous space. B, During needle insertion, the needle should be stabilized in a tripod fashion while placed in the hand, similar to a dart being thrown. Vertebral anatomy of the midline and paramedian approaches to centroneuraxis blocks. The midline approach highlighted in the inset requires anatomic projection in only two planes: sagittal and horizontal. The paramedian approach shown in the inset and in the posterior view requires an additional oblique plane to be considered, although the technique may be easier in patients who are unable to cooperate in minimizing their lumbar lordosis. The paramedian needle is inserted 1 cm lateral and 1 cm caudad to the caudad edge of the more superior vertebral spinous process. The paramedian needle is inserted approximately 15 degrees off the sagittal plane, as shown in the inset. As in the midline approach, the characteristic feel of the ligaments and dura is possible, but only once the ligamentum flavum is reached because the needle is this time not passing through the supraspinous and interspinous ligaments. In obstetrics, it may also be used in patients with morbid obesity and where previous spinal surgery may hinder epidural spread. A midline or paramedian approach may be used, with some experts suggesting that use of the paramedian approach facilitates insertion of the catheter. The catheter must never be withdrawn back into the needle shaft in case a piece of the catheter is sheared off and left in the subarachnoid space. Care must also be taken to ensure that the catheter is not inserted more deeply into the subarachnoid space when the needle is withdrawn over the catheter. Spinal microcatheters exist, but these have been associated with cauda equina syndrome,5 probably because of lumbosacral pooling of local anesthetic. Unilateral Spinal Anesthesia and Selective Spinal Anesthesia the terms unilateral spinal anesthesia and selective spinal anesthesia overlap slightly, but both refer to small-dose techniques that capitalize on baricity and patient positioning to hasten recovery. A recent systematic review found that a dose of 4 to 5 mg of hyperbaric bupivacaine with unilateral positioning was adequate for knee arthroscopy. In selective spinal anesthesia, minimal local anesthetic doses are used with the goal of anesthetizing only the sensory fibers to a specific area. There are many methods of assessing sensory block, but cold sensation and pinprick representing C- and A-delta fibers, respectively, are used more Figure 56-7. Examples of continuous spinal needles, including a disposable, 18-G Hustead (A) and a 17-G Tuohy (B) needle. Both have distal tips designed to direct the catheters inserted through the needles along the course of the bevel opening; 20-G epidural catheters are used with these particular needle sizes. A B Chapter 56: Spinal, Epidural, and Caudal Anesthesia 1703 often than mechanical stimuli such as touch, pressure, and von Frey hairs, which reflect the A-beta nerves. Loss of sensation to cold usually occurs first, verified using an ethyl chloride spray, ice, or alcohol, followed by the loss of sensation to pinprick, verified using a needle that does not pierce the skin. Dermatomal block height also varies with the method of assessment, but in general, peak height is measured most cephalad using loss of cold, and is measured lower with pinprick, and lowest with touch. The modified Bromage scale (Box 56-1) is most commonly used, although this represents only lumbosacral motor fibers. In practice, the combination of sympathetic block with an adequate sensory level and motor block (inability to straight-leg raise ensures at least that lumbar nerves are blocked) are used to confirm spinal efficacy. Ensuring that the level of block using cold or pinprick is two to three segments above the expected level of surgical stimulus is commonly considered adequate. As a general principle, 1 to 2 mL of solution should be injected per segment to be blocked. Although additives such as bicarbonate, epinephrine, and opioids influence onset, quality, and duration of analgesia and anesthesia, these do not affect spread. As with spinal anesthesia, it appears that only the extremes of patient height influence local anesthetic spread in the epidural space. Weight is not well correlated with block height in the settings of either lumbar or thoracic epidural anesthesia.

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