By E. Peratur. Western Maryland College.
Figure 13–12 demonstrates some common upper extremity Basilic Cephalic vein vein Basilic Cephalic vein vein Accessory cephalic vein Median cubital vein 13 Cephalic Basilic vein vein FIGURE 13–12 Principle veins of the arm used to place IV access and in venipuncture buy 0.18mg alesse, the pattern can be highly variable generic alesse 0.18mg on-line. Also avoid the leg because the inci- dence of thrombophlebitis is high with IVs placed there purchase alesse 0.18 mg overnight delivery. Use the techniques described in the sec- tion on venipuncture to help expose the vein (page 309) purchase alesse 0.18mg online. If a large-bore IV is to be used (16 or 14) generic 0.18mg alesse with visa, local anesthesia (1idocaine injected with a 25-gauge needle) is helpful. Using the catheter-over- needle assembly (Intracath or Angiocath), either enter the vein directly or enter the skin alongside the vein first and then stick the vein along the side at about a 20-degree angle. Direct entry and side entry IV techniques are illustrated in Figures 13–13 and 13–14. Once the vein is punctured, blood should appear in the “flash chamber” of a catheter-over- needle assembly. Advance a few more millimeters to be sure thatboththe needleandthe tip of the catheter have entered the vein. Never withdraw the catheter over the needle be- cause this procedure can shear off the plastic tip and cause a catheter embolus. Blood loss can be minimized by compressing the vein with the thumb just proximal to the catheter. With the IV fluid running, observe the site for signs of induration or swelling that indi- cate improper placement or damage to the vein. Tape the IV securely in place, apply a drop of povidone–iodine or antibiotic ointment and sterile dressing. Ideally, the dressing should be changed every 24–48 h to help re- duce infections. It is very useful in infants, who often have poor peripheral veins but prominent scalp veins, children, and in adults who have small, fragile veins. Troubleshooting difficult IV placement 13 • If the veins are deep and difficult to locate, a small 3–5-mL syringe can be mounted on the catheter assembly. If blood specimens are needed on a patient who also needs an IV, this technique can be used to start the IV and to collect samples at the same time. Spend about 1 min using both hands to “milk” blood from the arm toward the forearm. While holding the arm compressed with both hands, place a tourniquet above the elbow. LUMBAR PUNCTURE Indications • Diagnostic purposes:Analysis of CSF for conditions such as meningitis, encephali- tis, Guillain-Barré syndrome, staging work-up for lymphoma, others • Measurement of CSF pressure or its changes with various maneuvers (Valsalva, etc) • Injection of various agents: Contrast media for myelography, antitumor drugs, analgesics, antibiotics 13 Bedside Procedures 281 Angiocath Vein Vein Needle 13 Catheter Needle Catheter Vein FIGURE 13–13 To insert a catheter-over-needle assembly into a vein, stabilize the skin and vein with gentle traction. Specifi- cally, during an LP the fluid is obtained from the lumbar cistern, the volume of CSF lo- cated between the termination of the spinal cord (the conus medullaris) and the termination of the dura mater at the coccygeal ligament. Located within the cistern are the filum terminale and the nerve roots of the cauda equina. When an LP is done, the main body of the spinal cord is avoided and the nerve roots of the cauda are simply pushed out of the way by the needle. The termination of the spinal cord in the adult is usually between L1 and L2, and in the pediatric patient between L2 and L3. The safest site for an LP is the interspace between L4 13 Bedside Procedures 283 and L5. An imaginary line drawn between the iliac crests (the supracristal plane) intersects the spine at either the L4 spinous process or the L4–L5 interspace. A spinal needle introduced between the spinous processes of L4 and L5 penetrates the layers in the following order: skin, supraspinous ligament, interspinous ligament, ligamen- tum flava, epidural space (contains loose areolar tissue, fat, and blood vessels), dura, “po- tential space,” subarachnoid membrane, subarachnoid space (lumbar cistern) (Fig. Body Spinal Pedicle canal Transverse process Lamina Spinous process Spinal canal 13 Ligamentum flavum Intervertebral Interspinal disk ligaments Spinous Vertebral process body Supraspinous ligament FIGURE 13–15 Basic anatomy for a lumbar puncture. Examine the fundus for evidence of papilledema, and review the CT or MRF of the head if available. Discuss the relative safety and lack of discomfort to the patient to dis- pel any myths.
Higher rates of consanguinity may also be responsible for other birth defects seen infre- are often seen in rare autosomal recessive disorders alesse 0.18mg mastercard. Other diseases resulting in similar intestinal National Foundation for Jewish Genetic Diseases buy 0.18 mg alesse with amex, Inc alesse 0.18 mg mastercard. As of 2000 0.18 mg alesse free shipping, there was no direct test of National Organization for Rare Disorders (NORD) cheap alesse 0.18 mg on-line. Reduced triglyceride content in the diet is suggested if intestinal Acanthocytosis see Abetalipoproteinemia symptoms require it. Large supplemental doses of vita- min E (tocopherol) have been shown to lessen or even reverse the neurological, muscular, and retinal symptoms in many cases. Definition Occupational and physical therapy can assist with any muscular and skeletal problems that arise. Physicians Acardia is a very rare, serious malformation that that specialize in orthopedics, digestive disorders, and occurs almost exclusively in monozygous twins (twins eye disease should be involved. This condition results cialty clinics for individuals with multisystem disorders from artery to artery connections in the placenta causing a physically normal fetus to circulate blood for both itself such as ABL are available in nearly all metropolitan and a severely malformed fetus whose heart regresses or areas. Prognosis Description ABL is rare, which means there have been few indi- Acardia was first described in the sixteenth century. The Early references refer to acardia as chorioangiopagus effectiveness of vitamin supplementation and diet restric- parasiticus. It is now also called twin reversed arterial tions will vary from person to person and family to fam- perfusion sequence, or TRAP sequence. Life span may be near normal with mild to moderate disability in some, but others may have more serious and Mechanism even life-threatening complications. Arriving at the cor- Acardia is the most extreme form of twin-twin trans- rect diagnosis as early as possible is important. Twin-twin transfusion syndrome is a this is often difficult in rare conditions such as ABL. This abnormal connection MTP gene may lead to the availability of accurate carrier can cause serious complications including loss of the testing and prenatal diagnosis for some families. GALE ENCYCLOPEDIA OF GENETIC DISORDERS 7 Acardius amorphus appears as a disorganized mass KEY TERMS of tissues containing skin, bone, cartilage, muscle, fat, and blood vessels. This type of acardiac twin is not rec- Amniocentesis—A procedure performed at 16-18 ognizable as a human fetus and contains no recognizable weeks of pregnancy in which a needle is inserted human organs. Either the fluid itself or cells from oped head with brain tissues and facial structures. This the fluid can be used for a variety of tests to obtain type of acardiac twin is associated with a high risk for information about genetic disorders and other complications in the normal twin. Dizygotic—From two zygotes, as in non-identical, This type of acardiac twin presents as an isolated head or fraternal twins. Fetus—The term used to describe a developing Genetic profile human infant from approximately the third month of pregnancy until delivery. The zygote is the first cell formed by the ences are believed to be due to abnormal blood circulation. Aneuploidy, or an abnormal number of chromo- somes, has been seen in several acardiac twins, but is rare in the normal twins. Trisomy 2, the presence of three In acardiac twin pregnancies, blood vessels abnor- copies of human chromosome 2 instead of the normal mally connect between the twins in the placenta. The pla- two copies, has been reported in the abnormal twin of centa is the important interface of blood vessels between two pregnancies complicated by TRAP sequence in dif- a mother and baby through which babies receive nutri- ferent women. Since monozy- twin with stronger blood flow to pump blood for both, gotic twins are formed from a single zygote, scientists straining the heart of this “pump” twin. This abnormal theorize that an error occurs early in cell division in only connection causes the malformed twin to receive blood one of the two groups of cells formed during this process. Acardia is believed to complicate 1% of monozygotic twin preg- The acardiac twin nancies. Monozygotic twin- The acardiac twin is severely malformed and may be ning in higher order pregnancies are more common in incorrectly referred to as a tumor. In 1902, a physician pregnancies conceived with in vitro fertilization (IVF), named Das established four categories of acardiac twins hence increased risk for TRAP sequence is also associ- based on their physical appearance.
The class of variable order alesse 0.18 mg on-line, kinetic or kinematic variable generic alesse 0.18mg overnight delivery, and the coordinate frame for movement control are hypothetically independent generic alesse 0.18mg with amex. There is compelling evidence from the psychophysical literature that movement is indeed planned in terms of extrinsic coordinates buy generic alesse 0.18 mg online,27–30 although there are other views purchase 0.18 mg alesse free shipping. Of course, the executive motor system, and particularly the motor cortex, is under no obligation to operate directly on the information in this vector format, although, again, it may be the most parsimonious approach. The most compelling evidence in favor of the kinematic control of movement comes not from the psychophysical literature, but from direct neural recording in Copyright © 2005 CRC Press LLC FIGURE 5. As mentioned above, there is a large body of work demonstrating that cells in the motor cortex relate strongly to the direction of arm movement in space. Alexander and Crutcher40,41 dissociated the direction of arm movement from the muscles used in a visually controlled task by applying loads to a one- dimensional manipulandum. Approximately one third of cells in the monkey motor cortex were related to muscle activation during the execution of movement41 and an even smaller proportion during a preparatory period before movement began. They found that about 25% Copyright © 2005 CRC Press LLC A Mid Sup Up: E R F Up+Rt: Rt: U E R Dn+Rt: Dn: F U E Dn+Lf: Lf: R F U Up+Lf: B Up: E R F Up+Rt: Rt: U E R Dn+Rt: Dn: F U E Dn+Lf: Lf: R F U Up+Lf: C Up: E R F Up+Rt: Rt: U E R Dn+Rt: Dn: F U E Dn+Lf: Lf: R F U Up+Lf: −500 500 −500 500 −500 500 FIGURE 5. The tuning of cell B does not change across the different postures; therefore, it can be categorized as “extrinsic. The motor cortex not only seems to encode relatively static kinematic parameters such as direction during point-to-point movements, but can also reﬂect parameters that change continuously during straight movements such as position, velocity, and acceleration. The radial histograms show the averaged neural activity during center-out reaching movements in the respective directions. The tick marks under each histogram represent 440 msec (the average response time plus movement time) and indicate the portion used, through averaging across the 8 directions, to generate the center-left waveform (nondirectional neural proﬁle). There is remarkable con- cordance between the nondirectional proﬁle (left, center) and the average speed of the move- ments (right, center). Fitting neural activity to other time-varying movement parameters like EMG or joint-angle velocity resulted in a much less accurate model of the data than that obtained for the trajectory of the hand. Muscles and their output, force, are the obvious control variable for cells in motor cortex. Evarts4,5 was the ﬁrst to show a relation between motor cortex activity and the force generated by the muscles. Since then, a large number of studies have shown relations between motor cortex and the magnitude, direction, and rate Copyright © 2005 CRC Press LLC of change in force. In addition, other work has demonstrated that the location of the hand, and hence the conﬁguration of the arm, may have a systematic effect on the direction tuning of cell activity during an isometric ramp and hold task,53 in which no actual movements were produced. Despite the inﬂuence of arm posture on the activity of single cells in the motor cortex, the direction of the population vector, based on the activity of these cells, has been relatively resistent to changes in arm posture. It is obvious that arm kinematics alone cannot account for the changes in neural activity that have been observed. However, such a conclusion is quite different from stating that the motor cortex codes primarily for the kinetics of motor output. As discussed above, there is clear evidence that movement is ﬁrst speciﬁed in terms of kinematics, but the actual movement is ultimately produced by a weighted activation of groups of muscles (kinetics). The hypothesis underlying successive coordinate transformations is that different motor areas, including several sub-areas of parietal cortex, participate in the various stages of this transformation from kinematics to kinetics. The common wisdom is that the motor cortex would either be involved in the ﬁnal stage of the kinematic to kinetic transformation or would implement the kinetics on instructions from a “higher” motor area such as the lateral premotor cortex or the supplementary motor area. There is more evidence in favor of the Copyright © 2005 CRC Press LLC motor cortex being instrumental in some kind of kinematic to kinetic transformation, though the form of such a transformation is not at all clear. In other words, the motor cortex primarily codes for the most relevant spatial aspects of motor output, both in the case of movement and during behaviors that are purely isometric. Let us imagine that one is required to make force pulses in different target directions in the presence of opposing forces. The muscle forces exerted will not be in the direction of the targets, because one has to neutralize the opposing forces. Will the activity of motor cortex cells reﬂect the actual forces produced by the muscle or the resultant force (a combination of the muscle force and the opposing force), which is inevitably in the direction of the target? Using this behavioral paradigm in the monkey, it was shown that both the single cell and population activity in the motor cortex related to the resultant force, which was the most relevant spatial variable, and not to the forces produced by the muscles.
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