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The disease order cheap chloramphenicol on line xithrone antibiotic, glycogen storage disease) order chloramphenicol online antibiotics for urinary tract infection uk, and hypersplenic primary indication for splenectomy in this patient states (hemolytic anemias discount chloramphenicol 250mg on-line antimicrobial news, sickle cell diseases) is diagnostic, with a suspicion of hematologic Case 90B 405 malignancy. Secondary benefits are likely to include ease, refractory cytopenias, or bulk symptoms from relief of the abdominal discomfort and resolution of persistent splenomegaly, and patients with spleno- the thrombocytopenia. Splenectomy for lymphoma should be accom- Procedure-specific risks were discussed, including plished with minimal morbidity and mortality and postoperative hemorrhage, pancreatic or gastric in- an expected hospital stay of 3 to 4 days. Also discussed was the increased susceptibility to certain bacterial infections in the asplenic state and the use Presentation: Case 90B of prophylactic vaccinations. The hematology service refers a 74-year-old man with polycythemia vera, to be considered for ■ Surgical Approach splenectomy. He is in the “burnt out” phase of his disease and has had multiple admissions for transfu- An open approach to splenectomy was undertaken sion-dependent refractory anemia. Past medical his- due to splenic size and the potential malignant tory is notable for hypertension. A left subcostal incision was created and ab- tient developed symptoms of early satiety, weight dominal exploration revealed bulky splenomegaly loss, and exertional dyspnea. A mass reveals no jaundice or ascites, but a markedly en- was palpable within the spleen and corresponded to larged, nontender spleen. The lesser sac was entered below the gastroepiploic arcade to expose the pancreatic body. The splenic artery was identi- Differential Diagnosis fied at the superior border of the pancreas, encir- cled, and ligated without division. The gastrosplenic The differential diagnosis for symptomatic massive ligament was divided up to the short gastric vessels. The short gastric vessels were di- poiesis, infection, and hematologic malignancy vided. After specimen removal, the operative Discussion field was carefully inspected for hemostasis. This patient presents with refractory anemia and bulk symptoms related to massive splenomegaly. The latter include gastric compression with early Case Continued satiety and weight loss, and diaphragm displace- ment with exertional dyspnea. Anemia and high- The patient tolerated the procedure well, was trans- output congestive heart failure related to increased ferred to the floor postoperatively, and discharged flow through the splenic artery may also contribute in stable condition on postoperative day 4. With polycythemia tient follow-up was scheduled with the hematol- vera, the spleen may act as a site of extramedullary ogy/oncology service. The pathology report re- hematopoiesis, resulting in progressive splenic en- turned as non-Hodgkin B-cell lymphoma, follicular largement. This is the most likely scenario in this small cleaved cell type (grade 1) involving spleen case. Given the history of polycythemia vera, Discussion causes of splenomegaly other than hematologic dis- ease would be uncommon. Splenectomy should be There are many types of non-Hodgkin lymphoma considered to potentially decrease transfusion re- with numerous clinical presentations. Localized dis- may be obtained for further evaluation of the ease is sometimes treated with radiation alone. However, most lymphomas are systemic and require chemotherapy with or without radiation. Although splenomegaly is not uncommon in association with Recommendation lymphoma, most patients will not require splenec- tomy. The spleen infarct in the periphery of the spleen and associated weighed 1,739 g and measured 25 15 7. In the “burned out” phase of poly- ally reveals splenomegaly and often hepatomegaly. Characteristic laboratory findings include an ele- This, in combination with splenomegaly from ex- vated hematocrit, thrombocytosis, and leukocytosis. Patients with polycythemia have a predisposi- the patient has developed significant bulk symp- tion to myelofibrotic transformation over time and toms from the enlarged spleen. Splenectomy is of- may develop myelofibrosis with myeloid metaplasia, fered to relieve symptoms and reduce the transfu- or acute myeloid leukemia. Risks of surgery include thrombotic complications, hematologic malignancy, hemorrhage, infection, injury to adjacent organs, or infection. The patient should receive stan- botomy, hydroxyurea, busulfan, and antiplatelet dard splenectomy vaccines preoperatively. With appropriate perioperative manage- tiplatelet and/or low-dose heparin therapy may be ment, splenectomy can be safely performed. Published series report mortality of 8% ■ Surgical Approach to 9% and morbidity of 31% to 40%, with hemor- rhagic/thrombotic complications in about 17% of The size of the spleen necessitates open splenec- patients. Standard approaches include midline or left ting of anemia, improvement of anemia is seen in subcostal incision. This patient underwent splenectomy for poly- Midline incisions may be more appropriate in cythemia vera in “burnt out” phase with refractory younger patients to avoid abdominal wall weakness anemia, massive splenomegaly secondary to ex- or numbness. The subcostal approach facilitates tramedullary hematopoiesis, and significant com- splenectomy in obese patients and those with a pressive symptoms. After complete abdominal explo- candidates, splenic irradiation may be considered. The splenic ar- tery is encircled at the superior border of the Presentation: Case 90C pancreas and ligated without division. This maneu- ver quickly decreases the size of the spleen and re- A 53-year-old woman with a history of myelofibro- duces bleeding during mobilization. The gastros- sis and myeloid metaplasia is referred for splenec- plenic ligament is divided and the spleen and tomy. The short has had a chronically enlarged spleen and now pres- gastric vessels are controlled and divided. One month prior to sels in the splenic hilum are then controlled and di- her visit she was seen by her hematologist with vided with removal of the specimen. He is dis- this visit, at which time she continued to have 408 Case 90C massive splenomegaly with a hemoglobin of 8. At this visit, she notes left upper quadrant discomfort, ab- Case Continued dominal distention, and dyspnea on exertion. Phys- ical examination of the abdomen reveals a markedly The hospital course is unremarkable and the patient enlarged spleen extending across the midline and is discharged on postoperative day 4. She remains myelofibrosis and myeloid metaplasia secondary to clinically stable 1 year after surgery. Although absent in this patient, he- splenectomy in this patient included anemia and patomegaly is seen in about 50% of cases.
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Stratifed randomization seeks to ensure that the subjects with important covariates are rationally distributed amongst the groups— thereby reducing the possibility of baseline imbalance order chloramphenicol cheap antibiotic eye drops for cats. This can also Block Randomization be done for anticipated imbalance in the responses 500mg chloramphenicol visa antibiotics for sinus infections best ones. If your study is Block randomization is one of the most common methods of ran- on a wonder dose that controls blood sugar level for 1 month best 250 mg chloramphenicol drag virus, and if domization. This requires that subjects are divided into M blocks you know that the effect could be different in males of age <50 years of size 2n/M each, where n is the stipulated size of each of the two compared to females of age ≥50 years, you may want to divide the groups. In the case of more than two groups, the block size must be enrolled subjects as <50M, ≥50M, <50F, and ≥50F, so that each of a multiple of the number of groups. For two groups, the block size these strata is adequately represented, and then divide them equally can be 4 or 6 or 8, but not 5 or 7. If you have enrolled a total of 80 into group 1 receiving the test drug and group 2 receiving the control subjects, you can make 20 blocks of 4 subjects each. Such stratifcation is useful when the effect is expected to block, allocate two subjects at random to group 1 and the other two vary across strata and helps in better interpretation. This strat- ifcation will not only help to ensure an adequate number of subjects (1,1,2,2), (1,2,1,2), (1,2,2,1), (2,2,1,1), (2,1,1,2), (2,1,2,1). This conclusion will have as much reliability One of these blocks is chosen at random for the frst four subjects as afforded by the sample size in each stratum. Then proceed to Since many medical responses are sex specifc, sex-stratifed ran- the second block of four subjects, and so on until all subjects are domization is common. But the diffculty region controls better for batch effects in 450K methylation analysis is that you know that the fourth subject after the frst three going to in the United States. For this, Nonetheless, stratifed randomization is not practical if there are several random block sizes are advocated that are concealed from many relevant covariates even if a large sample is available. Cluster Randomization Minimization In place of randomization of individual subjects, it is sometimes Minimization uses a computer-based process to determine ran- convenient to randomize groups. This is also used when random- domized allocation to treatment groups in real time at the time of ization of individuals is not feasible. For example, you may want to randomization of each individual subject by considering baseline assign residents of an entire village to a particular mosquito con- characteristics of all previously randomized subjects and the one trol strategy for malaria and another village to another strategy. This process tends to allocate the subject to data are still collected at an individual level. This is called cluster the group that results in the best baseline equivalence between the randomization. Pure minimization is deterministic, response of an individual is independent of that of another indi- which can predict in advance the group to be allocated, but in the vidual, whether belonging to the same village, family, or any other method we are discussing, a chance element is introduced. For example, kidney transplant patients in a hospital may that generates this process can be quite complicated. For details, see be undergoing a similar preoperative and postoperative protocol, Saghaei [3]. Adaptive Randomization In this case, individual randomization will not work, and cluster randomization can provide more reliable results. However, cluster Adaptive randomization uses a similar computer-based randomiza- randomization does not have the same statistical effciency as indi- tion system as does minimization, but rather than just determin- vidual randomization has. It has low statistical power due to a clus- ing random allocation to treatment in order to maximize baseline tering effect. The sample size has to be larger to compensate for this equivalence or equality of size of treatment groups, it dynamically loss. This may not be a big problem, because chunks of subjects are adjusts the ratio of allocation to treatment groups in light of emerg- selected in each cluster so that a few clusters may give a big sam- ing effcacy results. The problem of statistical analysis of a cluster- reduce the number of subjects exposed to an ineffective treatment randomized trial is more challenging as this becomes complicated (such as placebo) should the emerging results show a large differ- because the clustering effect has to be eliminated. Thall and Nguyen [4] have discussed this In cluster randomization, generally, only a small number of clusters type of randomization for improving utility-based dose fnding with are randomized. This may still give a large number of individuals, but bivariate ordinal outcomes. It is now standard practice in clinics to assess obesity and give advice accordingly. Ideally, it should be assessed by the amount of In the case of self-reporting, it has been observed that people fat present in the body, but that is diffcult to determine. It is considered age-sex independent in adults, ( height in meters 2 and nearly the same thresholds can be used for females as for males without much error, although it tends to be slightly less in females. Individuals with a large body frame and muscle mass, such as athletes, may be wrongly classifed as obese. Besides the usual heart-related parameters, it has Belgian scientist Adolphe Quetelet, who frst suggested it in 1832 also been found to be negatively associated with ovarian cancer [3]. Indices of This means that there is an additional chance that some differences relative weight and obesity. Body mass index—A physics per- under tests of hypotheses (philosophy of), this is not a major limi- spective. Appropriate body-mass index for Asian would like to use a Bonferroni type of procedure to adjust the sig- populations and its implications for policy and intervention strategies. The exaggerated relations bootstrap procedure, see resampling between diet, body weight and mortality: The case for a categori- cal data approach. Body mass index in rela- tion to ovarian cancer: A multi-centre nested case–control study. Early As a part of exploratory data analysis, the box-and-whiskers plot growth and coronary heart disease in later life: Longitudinal study. The larger the height of this box, the greater offs to defne thinness in children and adolescents: International sur- the spread of the values. The minimum and maximum values used to draw whiskers exclude these mild and clear outliers. If each test is undertaken at, say, a 5% level of signifcance, the total probability of Type I 200 Max = 197. In other words, 190 the more such tests are done, the more likely thaThat least some will produce a signifcant result just by chance when no real effect 180 Q = 177. Many methods have been proposed to ensure that the probability of Type I error does not 150 Median = 149. If there are four groups and 100 all pair-wise comparisons are required, then H = 6. The values of median, Q1, and Q3 as well as the mini- required for each value of x. Indrayan [9] has provided full details of this method in a nonmathematical language. The /pubmed/16817681 application extends to any setup where centiles are estimated for 4.
The sig- include inadequate hemostasis purchase chloramphenicol paypal get smart antibiotic resistance questions and answers, underlying coag- nifcance of superfcial siderosis is that it may ulopathies purchase genuine chloramphenicol on-line antibiotics for acne vulgaris, and hypertension purchase genuine chloramphenicol online antibiotics for acne and rosacea. The study was images show an intrinsically T1 hyperintense and T2 obtained to evaluate for residual tumor following recent hypointense extradural collection (*) with blooming and meningioma resection. The patient underwent subtotal and susceptibility-weighted imaging (d) show interval resection of glioblastoma. Preoperative axial T1-weighted appearance of high T1 signal hemorrhage and extensive (a) and susceptibility-weighted imaging (b) show a large susceptibility effect within and adjacent to the residual mass (*) in the left frontal lobe with only a few foci of tumor (arrows) microhemorrhage. Nevertheless, in Many types of enhancing lesions can be encoun- some cases, biopsy or serial imaging can help elu- tered on imaging after surgery, as listed in Table 5. Indeed, several of these conditions can coex- bed on imaging exams, particularly with aggres- ist and make interpretation of the imaging a chal- sive neoplasms, such as glioblastoma, which can lenge. Differentiation of these conditions from undergo spread to remote parts of the brain, seed recurrent enhancing tumor is based on morphology the scalp and face soft tissues, and undergo cere- as well as timing. Since intensifes over the ensuing residual enhancing tumor can be obscured or confounded by weeks, and resolves over granulation tissue, baseline imaging is recommended within 3–5 months 48 h of surgery, before granulation tissue forms. Serial imaging can also help to differentiate granulation tissue from residual tumor in that tumor increases in size over time, while granulation tissue should remain stable and eventually resolves Perioperative 2 weeks after surgery Two-thirds of patients have focal infarcts around the resection ischemia cavity, and this can account for new post-op neurological defcits. Enhancement slowly resolves, leaving an area of encephalomalacia Postoperative 1–3 weeks after surgery Clinical deterioration and new enhancement 1–3 weeks after infection surgery should raise a question of infection. Focal infection may show restricted diffusion Pseudoprogression Within 3 months following Infammatory response to treatment. Wanes with time (scans are performed every month until change determines likely diagnosis). The patient has a history of corresponding hypermetabolism on the blood volume left frontal lobe glioblastoma that was resected and map (b). The two Focal brain necrosis due to chemotherapy primary means of delivering intrathecal chemo- extravasation secondary to Ommaya reservoir therapy are Ommaya reservoirs and repeat lum- catheter obstruction is rare, with an incidence bar puncture. This condition is caused by in the subcutaneous tissues of the scalp and con- displacement of the catheter tip into the brain tain a pump mechanism for drug delivery agents parenchyma. Imaging demonstrates circumfer- into the ventricular system through an intraven- ential areas of necrosis surrounding the retracted tricular catheter (Fig. Ommaya reservoirs Ommaya catheter, manifesting as patchy enhance- offer many advantages over repeat lumbar punc- ment, high T2 signal, and restricted diffusion, rep- tures, including greater patient comfort, dimin- resenting cytotoxic edema (Fig. A unique ished risk for patients with thrombocytopenia, and serious complication of methotrexate extrav- more consistent drug levels, and possibly greater asation is progressive leukoencephalopathy. Tumor cyst devices are similar entity involves the white matter diffusely and can to Ommaya shunts, but are used to inject chemo- be either hemorrhagic or nonhemorrhagic. Cerebrospinal fuid cysts can sometimes form Infection is a major complication of Ommaya around Ommaya catheters and may be caused catheter placement. The incidence of Ommaya- by distal shunt obstruction, although this com- associated infection is 15% within the frst year of plication can also occur when the catheter is placement (range 2–23%). Staphylococcus aureus appropriately positioned, with or without hydro- and Staphylococcus epidermidis are the most cephalus. Manifestations of perceptible walls or rim enhancement, but may catheter-associated infection range from menin- have surrounding edema. Although the cysts may gitis to abscess, for which imaging is useful for be asymptomatic, it is important to evaluate for identifying fuid collections surrounding the cath- predisposing factors that could be addressed, eter (Fig. Debris in the fuid and enhance- such as malpositioning of the Ommaya catheter ment helps differentiate infection from hygromas (Fig. The tip of the catheter lies within the has a history of leptomeningeal spread of breast cancer. Axial T1-weighted also hydrocephalus 5 Imaging the Intraoperative and Postoperative Brain 213 5. The wafers are biodegradable sheets of poly- also be useful for monitoring tumor response to mers that are impregnated with the chemotherapy chemotherapy wafers. On both T2-weighted (b) and T1-weighted and placement of I-125 interstitial radiation seeds. The catheter and its position mark- to administer intracranial brachytherapy for ers are also visible on both modalities. This produces the appearance and Epilepsy Surgery of band-like cavitary lesions in the frontal lobe white matter (Fig. The procedure essen- which correspond to residual Pantopaque used tially consists of ablating the frontal lobe white for visualization of the lobotomy plane during matter tracts using a probe-like device known the operation. The surgery consists of introducing probes via frontal burr holes for ablation of the posteroventral portion of the globus pallidus interna (Fig. The goal of the procedure is to interrupt excessive inhibitory output from the basal ganglia. Eventually, the lesion-edema complex evolves into a smaller focus of low T1 signal and high T2 signal. The patient has a history of Parkinson’s disease and underwent pallidotomy approxi- mately 1 year prior to imaging on the left side and several days earlier on the right side. The lesion on the right is more recent and slightly less hypoat- tenuating than the lesion on the left. Axial T2-weighted (b) and axial T1-weighted (c) images show subacute blood products within the right pallidotomy lesion surrounded by edema and fuid within the chronic left pallidotomy lesion 220 D. There can be T1 hyperintensity due to petechial hemorrhage, as well as T2 hyperin- 5. The procedure imaging is also useful for confrming interruption can be performed in a minimally invasive man- of the cingulum. This process results in region of the cingulotomy lesion is associated necrosis of the surrounding brain tissue, which with improved behavior. The patient has microelectrode insertion site in the bilateral anterior a history of medically intractable obsessive-compulsive cingulate gyri. Following subcaudate tractotomy for treating severe cases of obsessive-compulsive and limbic leucotomy, rostral atrophy can be disorder. In addition, the fber tracts between the orbitofrontal cortex diffusion tensor imaging can depict the absence and the thalamus, which are located approxi- of normal communicating white matter tracts mately 5 mm anterior to the sella, 15 mm from between the inferior frontal lobes. T2-weighted with acute lesions images (b) demonstrate concentric T2 hyperintense zones 5 Imaging the Intraoperative and Postoperative Brain 223 c d Fig. Lesions are visible on T2-weighted images already apparent immedi- ately after sonication and the lesions enhance- ment due to blood-brain barrier disruption. Over the course of a week after sonication, edema becomes more prominent, enhance, and become more distinct on T1-weighted images. For example, there is decreased fractional anisotropy in the ipsilateral pre- and postcentral subcortical white matter in the hand knob area; the region of the corticospinal tract in the cen- trum semiovale, in the posterior limb of the inter- nal capsule, and in the cerebral peduncle; the Fig. Although the elec- ble thalamic pain syndrome, among other condi- trodes are normally secured to the calvarium, tions. Other subthalamic nucleus depending on the underlying complications include electrode fracture, “twid- condition (Figs. Precise position- dler syndrome,” and hemorrhage along the elec- ing of the electrodes can be achieved by the use trode tract, which is actually more common after of intraoperative stereotactic guidance and physi- removal (13%) than during insertion (2%), and ologic localization. The patient has had multiple aneurysms clipped and suffers from a thalamic pain syndrome secondary to hemorrhage and infarction.
Some machines ing on the specifc equipment being used and the may come with both active and passive scavenger manufacturer’s recommendations buy chloramphenicol 250mg lowest price bacteria que causa la gastritis. Some anesthesia machines provide equipment can cause major morbidity or mortality effective 500mg chloramphenicol infection xbox. Tese system checks 14 before each use increases operator familiarity may include nitrous oxide delivery (hypoxic mixture and confrms proper functioning buy chloramphenicol no prescription bacteria arrangement. These recommendations are valid only for an anesthesia system that conforms to current and relevant standards and includes an ascending bellows ventilator and at least the following monitors: capnograph, pulse oximeter, oxygen analyzer, respiratory volume monitor (spirometer), and breathing-system pressure monitor with high- and low-pressure alarms. Users are encouraged to modify this guideline to accommodate differences in equipment design and variations in local clinical practice. Users should refer to the appropriate operator manuals for specific procedures and precautions. Check that breathing circuit is complete, connected and pipeline gauges read about 50 psig. Attempt to create a hypoxic O /N 2 2O mixture and appropriate tidal volume and that during verify correct changes in flow and/or alarm. With the O2 flush activated, allow scavenger reservoir of artificial lungs and appropriate feel of system bag to distend fully, and then verify that absorber resistance and compliance. Check final status of machine monitors: capnograph, pulse oximeter, O2 analyzer, a. Therefore, the size of the leak can be estimated by increasing fresh gas flows until there Detection of a Leak is no change in the height of the bellows from one expiration to the next. If the bellows collapse despite After induction of general anesthesia and intuba- a high rate of fresh gas inflow, a complete circuit dis- tion of a 70-kg man for elective surgery, a standing connection should be considered. The site of the bellows ventilator is set to deliver a tidal volume disconnection must be determined immediately of 500 mL at a rate of 10 breaths/min. Where are the most likely locations of a Why has the ventilator bellows fallen and the breathing-circuit disconnection or leak? Frank disconnections occur most frequently Fresh gas flow into the breathing circuit is inad- between the right-angle connector and the tra- equate to maintain the circuit volume required for cheal tube, whereas leaks are most commonly positive-pressure ventilation. In there is no fresh gas flow, the volume in the breath- the intubated patient, leaks often occur in the tra- ing circuit will slowly fall because of the constant chea around an uncuffed tracheal tube or an inad- uptake of oxygen by the patient (metabolic oxygen equately filled cuff. An sites of disconnection or leak within the anesthesia 2 absence of fresh gas flow could be due to exhaus- machine and the breathing circuit, however. Every tion of the hospital’s oxygen supply (remember the addition to the breathing circuit, such as a humidi- function of the fail-safe valve) or failure to turn on fier, increases the likelihood of a leak. Leaks are particularly Large leaks within the anesthesia machine are less important in closed-circuit anesthesia. When the fresh gas tubing is released, and Practice of Low Flow, Minimal Flow and Closed the floats should briskly rebound and settle at their System Anaesthesia, 2nd ed. Lippincott, Williams & Wilkins, Leaks within a breathing circuit not connected 2008. Somprakit P, Soontranan P: Low pressure leakage in anaesthetic machines: Evaluation by positive Any connection within the breathing circuit is a and negative pressure tests. Leaks can usually be identified audibly provides resources and a newsletter that discusses or by applying a soap solution to suspect connec- important safety issues in anesthesia. Pulse pressure is the diference specifc monitoring devices and techniques used between the systolic and diastolic pressures. In: Clinical Monitoring: Practical Applications in Anesthesia and Radial artery Critical Care Medicine. In contrast, Contraindications radial artery systolic pressures ofen underestimate Although some method of blood pressure measure- more “central” pressures following hypothermic ment is mandatory, techniques that rely on a blood cardiopulmonary bypass because of changes in pressure cuf are best avoided in extremities with hand vascular resistance. Vasodilating drugs may vascular abnormalities (eg, dialysis shunts) or with accentuate this discrepancy. Rarely, it may prove impossible to pling site relative to the heart afects the measure- monitor blood pressure in cases (eg, burns) in which ment of blood pressure because of the efect of there may be no accessible site from which the blood gravity (Figure 5–2). Noninvasive Arterial Blood underestimate systolic pressure, however, because of Pressure Monitoring the insensitivity of touch and the delay between fow under the cuf and distal pulsations. The equip- The use of any anesthetic, no matter how “trivial,” ment required is simple and inexpensive. Doppler Probe determination depend on the patient’s condition When a Doppler probe is substituted for the and the type of surgical procedure. The Doppler efect is the shif the probe directly above an artery is crucial, since the in the frequency of sound waves when their source beam must pass through the vessel wall. For example, the pitch from probe movement or electrocautery is an annoy- of a train’s whistle increases as a train approaches ing distraction. A Doppler probe transmits an ultra- electric crystal to detect lateral arterial wall move- sonic signal that is refected by underlying tissue. As ment to the intermittent opening and closing of red blood cells move through an artery, a Doppler vessels between systolic and diastolic pressure. The dif- instrument thus detects both systolic and diastolic ference between transmitted and received frequency pressures. The Doppler efect is routinely employed causes the characteristic swishing sound, which by perioperative echocardiographers to discern both indicates blood fow. When the cuf pressure decreases to systolic pressure, the pulsa- tions are transmitted to the entire cuf, and the oscillations markedly increase. Because some oscillations are present Radial artery above and below arterial blood pressure, a mer- cury or aneroid manometer provides an inaccurate and unreliable measurement. Automated blood Doppler probe pressure monitors electronically measure the pres- sures at which the oscillation amplitudes change (Figure 5–4). A microprocessor derives systolic, mean, and diastolic pressures using an algorithm. Nonetheless, the speed, accuracy, and versatility of oscillomet- ric devices have greatly improved, and they have within the heart and the movement of the heart’s become the preferred noninvasive blood pressure muscle tissue (tissue Doppler). Arterial Tonometry Infation of a blood pressure cuf to a pressure Arterial tonometry measures beat-to-beat arterial between systolic and diastolic pressures will par- blood pressure by sensing the pressure required to tially collapse an underlying artery, producing tur- partially fatten a superfcial artery that is supported bulent fow and the characteristic Korotkof sounds. A tonometer Tese sounds are audible through a stethoscope consisting of several independent pressure trans- placed under—or just distal to—the distal third of ducers is applied to the skin overlying the artery the blood pressure cuf. Continuous pulse recordings heard through part of the range from systolic to produce a tracing very similar to an invasive arterial diastolic pressure. Limitations to this tech- common in hypertensive patients and can lead nology include sensitivity to movement artifact and to an inaccurate diastolic pressure measurement. Korotkof sounds are ofen difcult to auscultate during episodes of hypotension or marked periph- eral vasoconstriction. In these situations, the sub- Clinical Considerations sonic frequencies associated with the sounds can be Adequate oxygen delivery to vital organs must detected by a microphone and amplifed to indicate be maintained during anesthesia. Motion artifact and instruments to monitor specifc organ perfusion electrocautery interference limit the usefulness of and oxygenation are complex, expensive, and ofen this method.
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