Michael A. Tall, MD

• Chief, Magnetic Resonance Imaging
• Wilford Hall Medical Center
• Lackland AFB, Texas

One option is to open the serosa hair loss treatment reviews dutasteride 0.5 mg buy low cost, evacuate the haematoma without violation of the mucosa hair loss in men xmas buy generic dutasteride 0.5 mg online, and carefully repair the wall of the bowel hair loss 45 women dutasteride 0.5 mg buy. The concern is that this may convert a partial tear to a full-thickness tear of the duodenal wall hair loss 5 alpha reductase buy dutasteride with amex. Another option is to carefully explore the duodenum to exclude a perforation hair loss protocol scam alert purchase dutasteride 0.5 mg otc, leaving the intramural haematoma intact and planning nasogastric decompression postoperatively. These injuries are related to associated pancreatic injury, blunt or missile injury, involvement of more than 75 per cent of the duodenal wall, injury of the first or second part of the duodenum, a time interval of more than 24 hours between injury and repair, and associated common bile duct injury. In these high-risk injuries, several adjunctive operative procedures have been proposed in an attempt to reduce the incidence of dehiscence of the duodenal suture line. The closure should be oriented transversely, if possible, to avoid luminal compromise. Longitudinal duodenotomies can usually be closed transversely if the length of the duodenal injury is less than 50 per cent of the circumference of the duodenum. If primary closure would compromise the lumen of the duodenum, several alternatives have been recommended. A pedicled mucosal graft, as a method of closing large duodenal defects, has been suggested, using a segment of jejunum or a gastric island flap from the body of the stomach. An alternative to that is the use of a jejunal serosal patch to close the duodenal defect. Although encouraging in experimental studies, the clinical application of both methods has been limited, and suture line leaks have been reported. When such injury occurs distal to the ampulla of Vater, closure of the distal duodenum and roux-en-Y duodenojejunal anastomosis is appropriate. A direct anastomosis to a roux-en-Y loop sutured over the duodenal defect in an end-to-side fashion is the procedure of choice. This also can be applied as an alternative method of operative management of extensive defects to the other parts of the duodenum when primary anastomosis is not feasible. External drainage should be provided in all duodenal injuries because it affords early detection and control of the duodenal fistula. The drain is preferably a simple, soft silicone rubber, closed system placed adjacent to the repair. In order to protect the duodenal repair, the gastrointestinal contents ­ with their proteolytic enzymes ­ can be diverted, a practice that would also make the management of a potential duodenal fistula easier. This is frequently the case with injuries of the first, third or fourth part of the duodenum, where mobilization is technically not difficult. The disadvantage of duodenal diverticulation is that it is an extensive procedure totally inappropriate for the haemodynamically unstable trauma patient, or the patient with multiple injuries. Resection of a normal distal stomach cannot be beneficial to the patient, and should not be considered unless there is a large amount of destruction and tissue loss and no other course is possible. It was first described in 1954 as a method of management of a precarious closure of the duodenal stump after a gastrectomy. The initial favourable reports on the efficacy of this technique to decrease the incidence of dehiscence of the duodenorrhaphy have, however, not been supported by more recent reports. The fashioning of a feeding jejunostomy at the initial laparotomy in patients with duodenal injury and extensive abdominal trauma (Abdominal Trauma Index score >25) is highly recommended. After primary repair of the duodenum, a gastrotomy is made at the antrum along the greater curvature. The pyloric ring is grasped and invaginated outside the stomach through the gastrotomy and is closed with a large running suture or stapled. The closure of the pylorus breaks down after several weeks, and the gastrointestinal continuity is re-established. This occurs regardless of whether the pylorus was closed with absorbable sutures, non-absorbable sutures or staples. Pyloric exclusion is a technically easier, less radical and quicker operation than diverticulation of the duodenum, and appears to be equally effective in the protection of the duodenal repair. Damage control with control of bleeding and of bowel contamination, and ligation of the common bile and pancreatic ducts, should be the rule. Simple combined injuries of the pancreas and duodenum should be managed separately. Extensive local damage of the intraduodenal or intrapancreatic bile duct injuries frequently necessitates a staged pancreaticoduodenectomy. Less extensive local injuries can be managed by intraluminal stenting, sphincteroplasty or reimplantation of the ampulla of Vater. If the surgeon opens the abdomen and there is extensive retroperitoneal bleeding centrally, there are two options: If the bleeding is primarily venous in nature, the right colon should be mobilized to the midline, including the duodenum and head of the pancreas. This includes taking down the left colon and mobilizing the pancreas and spleen to the midline. By approaching the aorta from the left lateral position, it is possible to identify the plane of Leriche more rapidly than it is by approaching it through the lesser sac. The problem is the coeliac and superior mesenteric ganglion, which can be quite dense and hinder dissection around the origins of the coeliac and superior mesenteric artery. Additional exposure can be obtained simply by dividing the left crus of the diaphragm. This will allow proximal control of the abdominal aorta until complete dissection of the visceral vessels can be accomplished. The exception is in the area of the coeliac ganglion, which can contain aortic haemorrhage from significant injuries, and which may require short segmental graft replacement. Extensive lacerations are not compatible with survival, and it is uncommon to require graft material to repair the aorta. Caval injuries below the renal veins, if extensive, can be ligated, although lateral repair is preferred. Injuries above the renal veins in the cava should be repaired if at all possible, including onlay graft of autogenous tissue. Consideration of both the possible injuries and the surgical approach to manage them is crucial. It is helpful to have available all the apparatus for massive transfusion, with adequate warming of all intravenous fluids. Major vessel injuries within the abdominal cavity primarily present as haemorrhagic shock that does not respond to resuscitation; thus, immediate surgery becomes a part of the resuscitative effort. In penetrating injury, this may necessitate an emergency department thoracotomy and aortic cross-clamping. However, the emergency department thoracotomy is not indicated in the severely shocked patient with blunt abdominal trauma, as the survival rate is close to zero. Injuries above the pelvic brim can be approached from the right side if the injury is thought to be below the renal artery, and from the left side for injuries between the renal artery and the hiatus. Vascular injuries in the pelvis following blunt trauma are best managed with an arteriogram. This will determine whether a direct operative approach or interventional radiology is appropriate. The the abdomen 131 lienorenal and lienophrenic ligaments are divided, followed by an incision down the left paracolic gutter, and a blunt dissection to free the organs from the retroperitoneum towards the centre of the abdomen. An extended reflection of the abdominal structures from the left to the right will reflect the spleen, colon, tail of pancreas and fundus of the stomach towards the midline. This provides access to the aorta, the coeliac axis, the superior mesenteric artery, the splenic artery and vein, and the left renal artery and vein. In order to reach the posterior wall of the aorta, the kidney should be mobilized as well and rotated medially on its pedicle, taking great care not to cause further injury. There is recent literature to support extraperitoneal pelvic packing as the most efficient damage control technique to control this type of bleeding. Renal injuries can generally be managed non-operatively including the use of selective embolization. However, with penetrating injury, because of the risk of damage to adjacent structures such as the ureter, it is safer to explore lateral haematomas, even if they are not expanding. The surgeon must also be confident that there is no perforation of the posterior part of the colon in the paracolic gutters on either side. In this case, it may be more appropriate to transfer the patient for immediate embolization. This surgery is fraught with hazard, and exploration of such haematomas should be a last resort. Wherever possible, angiographic visualization and embolization of any arterial bleeding must be tried before surgery is commenced, if the patient is sufficiently stable. However, rapidly expanding or pulsating haematomas in this region may need exploration. Stabilization of the pelvis using external fixators or a C-clamp in the emergency situation can be considered, but this does not always provide adequate posterior fixation, and may interfere with subsequent visualization of vessels for embolization. If the patient is too unstable for angiography, damage control surgery with packing of the pelvis should provide initial control. The peritoneum is incised over the distal aorta or the iliac vessels, in order to control the arterial inflow, before attention is directed to the actual injury. However, it is best to Control of the aorta can be achieved at several different levels depending on the site of injury. The supracoeliac aorta can be exposed by incising the gastrohepatic ligament, and retracting the left lobe of the liver superiorly and the stomach inferiorly. A window is then made in the lesser omentum, and the peritoneum overlying the crura of the diaphragm is divided. The oesophagus is then mobilized to the left in order to reach the abdominal aorta at the diaphragmatic hiatus. Exposure of the suprarenal aorta is not ideal with this anterior approach, and better exposure can be obtained by performing a left medial visceral rotation procedure. This entails mobilization of the splenorenal ligament and incision of the peritoneal reflection in the left paracolic gutter, down to the level of the sigmoid colon. The left-sided viscera are then bluntly dissected free of the retroperitoneum, and mobilized to the right. The entire abdominal aorta and the origins of its branches are exposed by this technique. This includes the coeliac axis, the origin of the superior mesenteric artery, the iliac vessels and the left renal pedicle. The common hepatic artery can be safely tied provided that the injury is proximal to the gastroduodenal artery. The distal aorta can be approached transperitoneally by retracting the small bowel to the right, the transverse colon superiorly, and the descending colon to the left. The aorta below the left renal vein can be accessed by incising the peritoneum over it and mobilizing the third and fourth parts of the duodenum superiorly. The ureters should be identified and carefully preserved, especially in the region of the bifurcation of the iliac vessels. Proximally, the artery is accessible from the aorta at the level of the renal arteries, and is best approached with a left medial visceral rotation. If a period of ischaemia has elapsed, or the surgery is part of a damage control procedure, the artery should be shunted, using a plastic vascular shunt. The graft must be tailored so that there is no tension, and the aortic suture line must be covered to prevent an aortoenteric fistula. The survival rate with penetrating injuries of the superior mesenteric artery is approximately 58 per cent, falling to 22 per cent if a complex repair is required. Injuries to this area are commonly missed, particularly in patients with stab wounds. Major vascular injury is particularly likely if there is a central retroperitoneal haematoma. In this situation, proximal vascular control prior to entering the haematoma is essential, either locally or via a left lateral thoracotomy. Division of the left triangular ligament and mobilization of the lateral segment of the left lobe of the liver is also helpful. The artery can be tied off, provided that the tie is proximal to its main branches and the superior mesenteric artery is intact. Injuries to the inferior mesenteric artery are uncommon, and the artery can generally be tied off. The abdomen 133 the colon should be checked before closure, with planned reoperation to evaluate viability of the colon. However, the kidney tolerates warm ischaemia poorly, and its viability after 45 minutes is in doubt. Therefore, if there has been complete transection of the artery, and the kidney is of doubtful viability, preservation may not be in the best interest of the patient. If more exposure is required, the root of the mesentery can be mobilized by dividing the inferior mesenteric vein. Performance of a Kocher manoeuvre and medial mobilization of the duodenum and head of the pancreas will reveal the segment of vena cava immediately below the liver, and also provide excellent exposure of the right renovascular 7. Not all non-bleeding posteflexure and incising the peritoneal reflection down the rior wounds require repair. The colon is then Proximal and distal control may be required, and distal control via a separate groin incision should be considered. The iliac vessels are exposed by lifting the small bowel upwards, out of the pelvis. On the left, the sigmoid colon and its mesentery can be mobilized, and on the right, division of the peritoneal attachments over the caecum and mobilization of the caecum to the midline will aid exposure of the vessels. The common iliac veins are often adherent to the back wall of the common iliac artery, and attempts to mobilize the veins for control may result in torrential bleeding. A vascular clamp, applied proximally from above to the hypogastric and iliac veins, may be preferable to direct control. If the injury is more proximal, it may artery be necessary to reflect the duodenum medially, or divide the pancreas.

Therefore hair loss cure japanese buy discount dutasteride on line, sodium lauryl sulfate is commonly used in dissolution testing to achieve this effect endometriosis hair loss cure cheap dutasteride 0.5 mg otc. In the fed state hair loss journey buy dutasteride once a day, the conditions of the stomach are highly dependent on the type and quantity of meal ingested hair loss cure in 2016 generic 0.5 mg dutasteride amex. Pancreatin may also be added if a more biorelevant form of the medium is required hair loss in men zip up hoodies buy dutasteride 0.5 mg mastercard. Pancreatin is a mixture of the fat-dissolving enzyme lipase, the proteindegrading enzymes called proteases, and those that break down carbohydrates, like amylase. Other considerations are the volume of the contents in the stomach or intestinal segment and the duration of the test as it related to residence time in the stomach or intestinal segment. Biorelevant Media Based on all of the previous considerations, biorelevant media have been proposed. The rationale for proposing the various components was provided in the previous comments. Because of the significant difference between the stomach and the intestine, media representative of the gastric and intestinal environments is commonly used. The major differences between gastric and intestinal media are the pH and presence of bile. Another important consideration is the absence or presence of food in the stomach. Similar dissolution characteristics for different batches of the same drug product imply similar performance of the product in humans. Although there are many customized and original dissolution testing devices reported in the literature, the purpose of this section is to introduce the basic apparatus used in compendial testing of immediate- and modified-release oral dosage forms. In practice, a rotating basket or paddle provides a steady stirring motion in a large vessel with 500 to 1000 mL of fluid that is immersed in a temperature-controlled water bath. Types of dissolution apparatus include (a) a stationary basket-rotating paddle for immediate-release oral solid dosage forms, (b) a modified stationary basket rotating paddle for suppositories, (c) a rotating dialysis cell, and (d) a rotating paddle­rotating basket. The temperature of the medium is usually maintained at body temperature (37 C) for dissolution testing. In the following examples, a variety of conditions are used that result in significantly different dissolution profiles, suggesting that the appropriate selection of dissolution conditions must be made. An example of an acceptable dissolution profile is seen when the dissolution medium is 0. This example shows that this is not always the case; this example is consistent with the report of a workshop published in 1996,41 where it was recognized that discrepancies between dissolution and bioavailability occur because the gel that comprises soft and hard gelatin capsules becomes cross-linked. The highest dissolution rates were observed in the media with enzymes present, and for pepsin, an increase in dissolution was observed with increasing pepsin activity, showing the role of the soft gelatin capsule dosage form in hindering the release of theophylline. Inclusion of the appropriate enzymes in the dissolution medium has been from Crison. Directing the fluid through a porous glass plate or a bed of beads produces a dispersed flow of medium. As with Apparatus 3, the medium can be changed to provide a pH gradient, surfactants, and other medium components. Examples include patients who now have to take only one tablet daily instead of one tablet three times daily because they are taking the osmotic pump form of the medication. Not only does drug delivery improve convenience for patients but it also improves compliance as they adhere to treatment regimens that may have been too complex. At this point the student should understand these concepts and understand the differences among immediate-, modified-, delayed-, extended-, and controlled-release delivery systems. You should also be able to differentiate between zero-order and first-order release kinetics as well as understand intrinsic dissolution rate and the driving force for dissolution. Understanding the effect of surface area and sink conditions on dissolution rate is critical and helps explain why drugs are so well absorbed after oral administration. Finally, the student should have an appreciation for the different roles that dissolution testing plays in the pharmaceutical sciences (a quality control versus predictive role) and understand how media properties such as viscosity, pH, lipids, and surfactants can affect dissolution. These tablets are orally delivered osmotic pumps that release drug through a laser-drilled orifice. Regulatory guidances recommend four dissolution apparatuses for modified-release dosage forms. Although the existing apparatuses are adequate for the intended purpose, equipment may require either modifications or completely new designs to accommodate these new release mechanisms. In contrast, disintegrating or eroding delivery systems pose the challenge of transferring the dosage form to different media without losing any of the pieces. In general, methods of agitation, changing the medium, and holding the dosage form in the medium without obstructing the release mechanism are relevant to drug testing. A challenging component of a dissolution test for a modified-release delivery system is changing the media to obtain a pH gradient or to simulate fed and fasted conditions. The ability to easily change the medium is the focus of commercially available dissolution equipment targeted for modified-release delivery systems, and several equipment designs are available. The cylinders can also be transferred to different media at specified times, automatically. Carstensen, Dissolution Technology, Academy of Pharmaceutical Sciences, Washington, D. Crison, Developing Dissolution Tests for Modified Release Dosage Forms: General Considerations. Understand Michaelis­Menten (nonlinear) kinetic behavior and linearization techniques. Understand the basis for transition-state theory and its application to chemical kinetics. The purpose of stability testing is to provide evidence on how the quality of a drug substance or drug product varies with time under the influence of a variety of environmental factors, such as temperature, humidity, and light, and to establish a retest period for the drug substance or a shelf life for the drug product and recommended storage conditions. Although the pharmaceutical scientist plays a critical role in determining the stability of pharmaceuticals, practicing pharmacists should be able to interpret this information for their patients. Pharmaceutical manufacturers routinely utilize the principles covered in this chapter; however, with the resurgence of pharmaceutical compounding, it is essential for practicing pharmacists to understand drug product stability as well. If a community pharmacist is asked to compound a prescription product, there are many factors that he or she must consider. The pharmacist must recognize that alterations in stability may occur when a drug is combined with other ingredients. For example, if thiamine hydrochloride, which is most stable at a pH of 2 to 3 and is unstable above pH 6, is combined with a buffered vehicle of, say, pH 8 or 9, the vitamin is rapidly inactivated. Even though pharmaceutical manufacturers label prescription and over-the-counter drug products with expiration dating to guide the patient/consumer in these matters, patients may store these products in a bathroom medicine cabinet where the humidity and temperature are higher than the typical storage place for medications. A community pharmacy practitioner should be able to understand this and advise patients on these matters. The experimental investigation of the possible breakdown of new drugs is not a simple matter. Applications of chemical kinetics in pharmacy result in the production of more stable drug preparations, the dosage and rationale of which may be established on sound scientific principles. Thus, as a result of current research involving the kinetics of drug systems, the pharmacist is able to assist the physician and patient regarding the proper storage and use of medicinal agents. This chapter brings out a number of factors that bear on the formulation, stabilization, and administration of drugs. Concentration, temperature, light, pH, and catalysts are important in relation to the speed and the mechanism of reactions and will be discussed in turn. According to the law of mass action, the rate of a chemical reaction is proportional to the product of the molar concentration of the reactants each raised to a power usually equal to the number of molecules, a and b, of the substances A and B, respectively, undergoing reaction. In the reaction aA + bB + = Products the rate of the reaction is 1 d[A] Rate = a dt 1 d[B] = = k[A]a [B]b b dt where k is the rate constant. The order with respect to one of the reactants, A or B, is the exponent a or b of that particular concentration term. Suppose that in this reaction, sodium hydroxide as well as water was in great excess and ethyl acetate was in a relatively low concentration. Each of the elementary reactions has a stoichiometry giving the number of molecules taking part in that step. Because the order of an elementary reaction gives the number of molecules coming together to react in the step, it is common to refer to this order as the molecularity of the elementary reaction. If, on the other hand, a reaction proceeds through several stages, the term molecularity is not used in reference to the observed rate law: One step may involve two molecules, a second step only one molecule, and a subsequent step one or two molecules. Hence, order and molecularity are ordinarily identical only for elementary reactions. In simple terms, molecularity is the number of molecules, atoms, or ions reacting in an elementary process. In the reaction Br2 2Br the process is unimolecular because the single molecule, Br2, decomposes to form two bromine atoms. Termolecular reactions, that is, processes in which three molecules must come together simultaneously, are rare. Chemical reactions that proceed through more than one step are known as complex reactions. The overall order determined kinetically may not be identical with the molecularity because the reaction consists of several steps, each with its own molecularity. The reaction is then said to be a pseudo­ first-order reaction because it depends only on the first power (a = 1) of the concentration of ethyl acetate. In general, when one of the reactants is present in such great excess that its concentration may be considered constant or nearly so, the reaction is said to be of pseudo-order. If the alcohol, which serves here as the solvent for acetic anhydride, is in large excess such that a small amount of ethyl alcohol is used up in the reaction, write the rate equation for the process and state the order. Answer: the reaction appears to be first order with respect to acetic anhydride, second order with respect to ethyl alcohol, and the order has been found experimentally to be 2. Any change in the conditions of the reaction, for example, in temperature or solvent, or a slight change in one of the reacting species, will lead to a rate law having a different value for the specific rate constant. Experimentally, a change of specific rate constant corresponds simply to a change in the slope of the line given by the rate equation. Variations in the specific rate constant are of great physical significance because a change in this constant necessarily represents a change at the molecular level as a result of a variation in the reaction conditions. Rate constants derived from reactions consisting of a number of steps of different molecularity are functions of the specific rate constants for the various steps. Any change in the nature of a step due to a modification in the reaction conditions or in the properties of the molecules taking part in this step could lead to a change in the value of the overall rate constant. At times, variations in an overall rate constant can be used to provide useful information about a reaction, but quite commonly, anything that affects one specific rate constant will affect another; hence, it is quite difficult to attach significance to variations in the overall rate constant for these reactions. Units of the Basic Rate Constants To arrive at units for the rate constants appearing in zero-, first-, and second-order rate laws, the equation expressing the law is rearranged to have the constant expressed in terms of the variables of the equation. Zero-Order Reactions Garrett and Carper3 found that the loss in color of a multisulfa product (as measured by the decrease of spectrophotometric absorbance at a wavelength of 500 nm) followed a zero-order rate. The rate expression for the change of absorbance, A, with time is therefore dA = k0 (14­7) - dt where the minus sign signifies that the absorbance is decreasing. The velocity of fading is seen to be constant and independent of the concentration of the colorant used. The rate equation can be integrated between the initial absorbance, A0, corresponding to the original color of the preparation at t = 0, and At, the absorbance after t hours: At A0 dA = -k0 0 t dt for a first-order reaction, k=- dA 1 moles/liter = dt A second-moles/liter 1 = second-1 = second or At - A0 = -k0 t At = A0 - k0 t (14­8) the initial concentration corresponding to A0 is ordinarily written as a and the concentration remaining at time t as c. For example, many hydrolysis decomposition reactions of drug molecules are second order. Usually the amount of water present is in excess of what is needed for the reaction to proceed. In other words, the concentration of water is essentially constant throughout the reaction. In this case, the second-order reaction behaves like a first-order reaction and is called an apparent or pseudo­firstorder reaction. Because the half-life is the time required for one-half of the material to disappear, in the present case A0 = 0. Determine the shelf life, t90, for the liquid prescription, assuming that the product is satisfactory until the time at which it has decomposed to 90% of its original concentration. As the drug decomposes in solution, more drug is released from the suspended particles so that the concentration remains constant. The important point is that the amount of drug in solution remains constant despite its decomposition with time. The equation for an ordinary solution, with no reservoir of drug to replace that depleted, is the first-order expression, equation (14­11): -d[A] = k[A] dt where [A] is the concentration of drug remaining undecomposed at time t, and k is known as a first-order rate constant. When the concentration [A] is rendered constant, as in the case of a suspension, we can write k[A] = k0 so that the first-order rate law (14­11) becomes - d[A] = k0 dt (14­10) (14­9) = 4. Although two molecules of hydrogen peroxide appear in the stoichiometric equation as just written, the reaction was found to be first order. The rate equation is written as - dc = kc dt (14­11) Equation (14­10) obviously is a zero-order equation. It is referred to as an apparent zero-order equation, being zero order only because of the suspended drug reservoir, which ensures constant concentration. Once all the suspended particles have been converted in to drug in solution, the system changes to a first-order reaction. Expiration date is the date placed on the container label of a drug product designating the time prior to which a batch of the product is expected to remain within the approved shelf-life specification if stored under defined conditions and after which it must not be used. The specific reaction rates listed in Table 14­1 were calculated by using equation (14­17). The linear expression in equation (14­13) shows that the slope of the line is ­k/2. Once the rate constant is known, the concentration of reactant remaining at a definite time can be computed as demonstrated in the following examples.

The AngioJet catheter is activated in a slow advancement mode along the entire length of the target thrombus in an antegrade and retrograde fashion hair loss cure enzyme buy dutasteride once a day. It can be combined with direct pharmacolytic therapy in activation mode using the "pulsed spray technique hair loss workup buy cheap dutasteride online. In the presence of a large thrombus burden or resistant clot hair loss cure two years trusted dutasteride 0.5 mg, the administration of lytics selectively in to the target vessel in conjunction with the AngioJet has been studied hair loss gene therapy 0.5 mg dutasteride order otc. It safely ablates underlying atherosclerotic plaque and facilitates subsequent stent placement hair loss cure 6 sterile best purchase dutasteride. This device promotes rapid thrombus clearance and suppresses platelet aggregation. Patient Preparation Routine patient preparation and anticoagulation for percutaneous intervention are required. The latest laser catheters have improved fiber array with concentric or eccentric tip configuration. The eccentric catheters are reserved for circumferential debulking in in-stent stenosis lesions for markedly eccentric lesions. The computer lasing program within the laser console limits each lasing train to 5 seconds, except for 10 seconds with the X-80 0. The patient and the catheterization laboratory staff should wear special protective goggles. Results Laser angioplasty has been studied in acute coronary and peripheral ischemic syndromes for thrombus-laden lesions, in-stent restenosis, and chronic total occlusions. This includes interventions in native coronary vessels; saphenous vein grafts; calcified, nondilatable lesions; and chronic total occlusions. In the era of drug-eluting stents, these devices are frequently used as part of a prestenting strategy. Practical Pearls the catheterization laboratory staff should be familiar with preparation of the relevant niche devices. An Amplatz left guide catheter is useful for technically demanding left coronary interventions. For intervention in an anatomically challenging right coronary artery, both Amplatz right or Amplatz left shapes can provide adequate support. This will significantly enhance subsequent device delivery and improve its utilization. Current role of emboli protection devices in percutaneous coronary and vascular interventions. An evidence-based approach to the use of rotational and directional coronary atherectomy in the era of drug-eluting stents: when does it make sense Adjunctive mechanical devices to prevent distal embolization in patients undergoing mechanical revascularization for acute myocardial infarction: a metaanalysis of randomized trials. Novel simultaneous combination chemical thrombolysis/rheolytic thrombectomy therapy for acute critical limb ischemia: the power-pulse spray technique. Rheolytic thrombectomy with percutaneous coronary intervention for infarct size reduction in acute myocardial infarction: 30-day results from a multicenter randomized study. Aspirating and filtering atherothrombotic debris during percutaneous coronary intervention. Early and long-term clinical results of AngioJet rheolytic thrombectomy in patients with acute pulmonary embolism. Alteration of platelet aggregation kinetics with ultraviolet laser emission: the stunned platelet phenomenon. Predictors for stent loss were lesion calcification and significant proximal angulation. The balloon is inflated distal to the stent (B) and withdrawn along with the stent in to the guide catheter. Recovering the stent requires advancing a loop over the stent then retracting the wire to trap the stent between the wire and guide catheter. Complete recovery with externalization of the stent is accomplished by applying continuous traction to the wire to prevent loss of the stent while removing the guide. Special Issues If the stent is lost in the peripheral vasculature, the aforementioned techniques can be used for recovery, but a few other tools are also available that can be useful. This complication was seen more often with devices intended to remove or ablate tissue (atherectomy, laser) and was more prevalent in the elderly and female populations. Although this type of perforation can be treated with techniques already described, other unique modalities also are described here. If the perforation has occurred at the distal tips of the epicardial vessels, microcoil embolization can be performed. Type 1 (top) perforations are described as an extraluminal crater without extravasation of dye. These lesions are quite difficult to identify on angiography and are often mistaken for dissections. Type 2 (middle) perforations produce myocardial or pericardial blush with frank contrast jet extravasation. These can be treated with prolonged balloon inflation, usually producing a reasonable angiographic result. Reversal of heparin with protamine is often not performed with this type of perforation. There is a possibility of developing late tamponade (up to 24 hours) with these patients, so that observation in a critical care setting may be appropriate. Type 3 (bottom) perforations produce a contrast jet with t1 mm diameter size opening and are associated with a high incidence of major adverse events (death, emergency coronary artery bypass graft surgery, tamponade). Cessation of all antiplatelet agents and reversal of heparin with protamine should also be performed emergently. Coronary artery dissection and perforation complicating percutaneous coronary intervention. The incidence of bleeding complication/hematoma formation is quite low in current practice (<1%). Management the most common presentation of bleeding is an external groin hematoma. If compression is unsuccessful, surgical cutdown under local anesthesia can be performed to acquire hemostasis. If the puncture site is below the inguinal ligament, an endovascular approach should be avoided because stent placement in this region is associated with multiple problems. Volume resuscitation is often adequate for this situation, but with refractory hypotension, an endovascular approach, described in Table 9. When an endovascular approach is not possible, these patients may need surgery to control the bleeding. With care, the first guide is slightly withdrawn to allow engagement of the coronary artery with the second guide. Arteriovenous fistula should be suspected in patients with a bruit present over the femoral artery after an intervention. Management Management of this complication depends on the overall size of the fistula. If the fistula is small and does not involve the common femoral artery, an endovascular delivery of microcoils to close off the communication may be sufficient. As expected, the judicious use of antithrombotics/antiplatelet agents reduces bleeding complications. The sequela of this tends not to be significant, with few problems reported in the literature. If spasm is not recognized, introduction of interventional wires and catheters can produce further injury, including perforation and dissection of the upper extremity arterial system. In addition, spasm can make removal of the arterial sheath difficult, and can result in avulsion of the radial artery. When bleeding is identified, hemostasis can be achieved with an Ace bandage or a blood pressure sphygmomanometer. In select cases, the interventional guiding catheter can be placed across the perforation and will produce effective hemostasis. Failure to recognize the complication and deal with it early in its course may lead to major problems, including fatality. Incidence, retrieval methods, and outcomes of stent loss during percutaneous coronary intervention: a large single-center experience. Intracoronary loss of balloon-mounted stents: Successful retrieval with a 2 mm-"Microsnare"-device. Successful retrieval of a lost coronary stent from the descending aorta using a loop basket intravascular retriever set. Management and outcomes of coronary artery perforation during percutaneous coronary intervention. Successful treatment of distal coronary guidewire-induced perforation with balloon catheter delivery of intracoronary thrombin. Risk predictors of retroperitoneal hemorrhage following percutaneous coronary intervention. Vascular complications after percutaneous coronary interventions following hemostasis with manual compression versus arteriotomy closure devices. Arterial puncture closing devices compared with standard manual compression after cardiac catheterization: systematic review and meta-analysis. Adverse impact of bleeding on prognosis in patients with acute coronary syndromes. Periprocedural bleeding and 1-year outcome after percutaneous coronary interventions: appropriateness of including bleeding as a component of a quadruple end point. Retrieval of undeployed stents from the right coronary artery: report of two cases. Incidence, predictors, and prognostic implications of bleeding and blood transfusion following percutaneous coronary interventions. Radial versus femoral approach for percutaneous coronary diagnostic and interventional procedures: systematic overview and meta-analysis of randomized trials. Problems and complications of the transradial approach for coronary interventions: a review. Chapter 10 Optimal Long-term Therapy of the Patient after Percutaneous Coronary Intervention Dharam J. Clopidogrel Clopidogrel is a prodrug, and it is converted to its active metabolite in the liver. However, it results in more rapid, higher, and more consistent levels of platelet inhibition than does clopidogrel, with significantly less variation in individual response. Antiplatelet Drug Resistance Antiplatelet drug resistance refers to the development of a thrombotic event while on antiplatelet agents due to ineffective or incomplete platelet inhibition. Low levels of platelet inhibition have also been associated with an elevated risk of ischemic events. Although not currently recommended for routine use, a number of platelet function tests are being evaluated,18,19 and some assays have demonstrated exciting initial clinical results. Factors include incomplete/nonendothelialization of the stent, the inflammatory milieu associated with surgery, and premature cessation of dual antiplatelet therapy. Aspirin and thienopyridines need to be discontinued for at least 5­7 days prior to surgery to restore normal hemostasis. A number of strategies to minimize the risk of perioperative stent thrombosis are outlined in the Practical Pearls section. Some other more invasive procedures can be similarly safely conducted with the patient on low-dose aspirin. Dual antiplatelet therapy should be resumed as soon as 24 hours or the next day after most surgeries, if possible. Some authorities recommend reloading with 600 mg of clopidogrel in patients with such interruptions in antiplatelet therapy, although this approach has not been validated in clinical studies. Only patients with unstable coronary syndromes or high-risk features should be considered for revascularization. Percutaneous coronary intervention with stents can be performed after surgery if indicated. Late stent thrombosis with drug-eluting stents: the price to pay to prevent restenosis Appropriate use of drug-eluting stents: balancing the reduction in restenosis with the concern of late thrombosis. A double-blind, randomized study on platelet aggregation in patients treated with a daily dose of 150 or 75 mg of clopidogrel for 30 days. A high maintenance dose of clopidogrel improves short-term clinical outcomes in patients with acute coronary syndrome undergoing drug-eluting stent implantation. Loading with 600 mg clopidogrel in patients with coronary artery disease with and without chronic clopidogrel therapy. Prasugrel compared with high loadingand maintenance-dose clopidogrel in patients with planned percutaneous coronary intervention: the Prasugrel in Comparison to Clopidogrel for Inhibition of Platelet Activation and Aggregation-Thrombolysis in Myocardial Infarction 44 trial. Prognostic significance of postclopidogrel platelet reactivity assessed by a point-of-care assay on thrombotic events after drug-eluting stent implantation. What makes platelets angry: diabetes, fibrinogen, obesity, and impaired response to antiplatelet therapy Systematic review and meta-analysis of randomized clinical trials appraising the impact of cilostazol after percutaneous coronary intervention. Completed studies comparing medical therapy to balloon angioplasty for treatment of hypertension7 allowed a large proportion of the patients who failed medical therapy to cross over to the angioplasty treatment. Other randomized investigations of stenting versus medical therapy8 included lesions of less than 70%, failed to stent a large number of those patients who were randomized to stenting,8,9 or set arbitrary resistive renal indices to determine procedural success. Technical Aspects of Renal Percutaneous Transluminal Angioplasty Vascular access can be obtained by a femoral, brachial, or radial approach. A protection protocol for contrast-induced nephropathy using acetylcysteine (Mucomyst) 1,200 mg b. Other useful guiding catheters include renal curve, multipurpose (mainly for brachial approach), Simmons Sidewinder, Sos Omni, Cobra, and Judkins right coronary. The guiding catheter is flushed frequently to avoid accumulation of any atherosclerotic or thrombotic material. Then the ostium of the renal artery is gently engaged and an adequate pressure wave form should be verified. A cross-lesion gradient can be recorded either by a pull-back technique with the guide catheter or with insertion of a pressure wire.

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