By R. Rendell. Long Island University.
The major effects are summarized this quaternary compound has little ef- in A (blue arrows) buy malegra dxt plus 160 mg cheap. Some of these effects fect on other organs because of its low have therapeutic applications buy malegra dxt plus 160 mg on line, as indi- rate of systemic absorption. Be- Substances acting antagonistically cause of its quaternary nitrogen, this at the M-cholinoceptor are designated drug does not enter the brain and re- parasympatholytics (prototype: the al- quires parenteral administration. Its kaloid atropine; actions shown in red in spasmolytic action is especially marked the panels). Therapeutic use of these because of additional ganglionic block- agents is complicated by their low organ ing and direct muscle-relaxant actions. Possibilities for a targeted Lowering of pupillary sphincter to- action include: nus and pupillary dilation by local ad- • local application ministration of homatropine or tropic- • selection of drugs with either good or amide (mydriatics) allows observation poor membrane penetrability as the of the ocular fundus. For diagnostic us- situation demands es, only short-term pupillary dilation is • administration of drugs possessing needed. Inhibition of exocrine glands AV-block, respectively, to raise heart Bronchial secretion. Premedication rate and to facilitate cardiac impulse with atropine before inhalation anes- conduction. As a quaternary substance, thesia prevents a possible hypersecre- it does not penetrate into the brain, tion of bronchial mucus, which cannot which greatly reduces the risk of CNS be expectorated by coughing during in- disturbances (see below). M1-receptors have also been demonstrated in the brain; how- ever, these cannot be reached by piren- zepine because its lipophilicity is too low to permit penetration of the blood- brain barrier. Pirenzepine was formerly used in the treatment of gastric and du- odenal ulcers (p. Effects of parasympathetic stimulation and blockade Lüllmann, Color Atlas of Pharmacology © 2000 Thieme All rights reserved. CNS-dampening effects exchange through increased cutaneous Scopolamine is effective in the prophy- blood flow. Decreased peristaltic activ- laxis of kinetosis (motion sickness, sea ity of the intestines leads to constipa- sickness, see p. Elderly subjects are more tion is present in the neutral, mem- sensitive to such central effects. Unlike atropine, scopol- pressants, neuroleptics, antihista- amine exerts a calming and amnesio- mines, antiarrhythmics, antiparkinso- genic action that can be used to advan- nian agents. Apart from symptomatic, general Symptomatic treatment in parkin- measures (gastric lavage, cooling with sonism for the purpose of restoring a ice water), therapy of severe atropine dopaminergic-cholinergic balance in intoxication includes the administra- the corpus striatum. Antiparkinsonian tion of the indirect parasympathomi- agents, such as benzatropine (p. The most readily penetrate the blood-brain barri- common instances of “atropine” intoxi- er. At centrally equi-effective dosage, cation are observed after ingestion of their peripheral effects are less marked the berry-like fruits of belladonna (chil- than are those of atropine. Prostatic hypertrophy with im- paired micturition: loss of parasympa- thetic control of the detrusor muscle ex- acerbates difficulties in voiding urine. Rarely life-threatening, poisoning with atropine is character- ized by the following peripheral and central effects: Peripheral: tachycardia; dry mouth; hyperthermia secondary to the inhibition of sweating. Although sweat glands are innervated by sympathetic fibers, these are cholinergic in nature. When sweat secretion is inhibited, the body loses the ability to dissipate meta- bolic heat by evaporation of sweat (p. There is a compensatory vasodila- tion in the skin allowing increased heat Lüllmann, Color Atlas of Pharmacology © 2000 Thieme All rights reserved. Parasympatholytics Lüllmann, Color Atlas of Pharmacology © 2000 Thieme All rights reserved. The point of contact (synapse) duplicate the time course of intrasynap- between the first and second neurons tic agonist concentration required for occurs mainly in ganglia; therefore, the appropriate high-frequency ganglionic first neuron is referred to as pregan- activation. The concentration of nico- glionic and efferents of the second as tine in the synaptic cleft can neither postganglionic. ACh stimulates receptors locat- The ganglionic effects of ACh can be ed on the subsynaptic membrane of the blocked by tetraethylammonium, hexa- second neuron. Activation of these re- methonium, and other substances (gan- ceptors causes the nonspecific cation glionic blockers). The resulting influx of trinsic activity, that is, they fail to stim- Na+ leads to a membrane depolariza- ulate ganglia even at low concentration; tion. Normally, not all preganglionic im- Certain sympathetic preganglionic pulses elicit a propagated response in neurons project without interruption to the second neuron. The ganglionic syn- the chromaffin cells of the adrenal me- apse acts like a frequency filter (A). The latter are embryologic homo- effect of ACh elicited at receptors on the logues of ganglionic sympathocytes. Ex- ganglionic neuronal membrane can be citation of preganglionic fibers leads to imitated by nicotine; i. If a with a release of epinephrine into the small dose of nicotine is given, the gan- blood (D). The ducing a partial depolarization of adre- membrane depolarizes partially, but nomedullary cells, are effective in liber- fails to reach the firing threshold. At a low concentration, nicotine acts as a gan- glionic stimulant; it alters the filter function of the ganglionic synapse, al- lowing action potential frequency in the second neuron to approach that of the first (B). Simultaneous activation of many nicotinic cholinoceptors depolarizes the ganglionic cell membrane to such an ex- tent that generation of action potentials Lüllmann, Color Atlas of Pharmacology © 2000 Thieme All rights reserved.
Doctors have identified Arnold-Chiari III and IV malformations buy 160mg malegra dxt plus mastercard, but they are very rare purchase 160 mg malegra dxt plus otc. IArnold-Chiari malformation Arnold-Chiari malformations may occur with other Definition conditions. There may be excessive fluid in the brain Arnold-Chiari malformation is a rare genetic disor- (hydrocephalus), opening in the spine (spina bifida), or der. In this syndrome, some parts of the brain are formed excessive fluid in the spinal cord (syringomyelia), but abnormally. Malformations may occur in the lower por- many people with Arnold-Chiari malformations do not tion of the brain (cerebellum) or in the brain stem. There has Cerebrospinal fluid—Fluid that circulates through- not yet been a study that shows whether or not this dis- out the cerebral ventricles and around the spinal order is inherited, but there are reports of several fami- cord within the spinal canal. One hypothesis is that the base of the Hydrocephalus—The excess accumulation of skull is too small, forcing the cerebellum downward. The overgrowth pushes the cerebellum downward Magnetic Resonance Imaging (MRI)—A technique into the spinal canal. As of 2001, Myelomeningocele—A sac that protrudes through there is no data that shows the incidence of Arnold-Chiari an abnormal opening in the spinal column. Arnold-Chiari malformations are the Posterior fossa—Area at the base of the skull most common type of malformation of the cervico- attached to the spinal cord. About one percent of live newborns have a mal- formation in the cervico-medullary junction. Signs and symptoms Some people with Arnold-Chiari I malformations have no symptoms. Typically, with an Arnold-Chiari I People with Arnold-Chiari malformations may have malformation symptoms appear as the person reaches the visual problems, including blurred vision, double vision, third or fourth decade of life. The symptoms may be vague or Diagnosis they may resemble symptoms of other medical problems, A Arnold-Chiari malformation is diagnosed with so diagnosis may be delayed. An MRI uses mag- One of the most common symptoms of Arnold- netism and radio waves to produce a picture of the brain Chiari malformations is a headache. The headache gen- and show the crowding of the space between the brain erally begins in the neck or base of the skull and may and spinal cord that occurs with Arnold-Chiari malfor- radiate through the back of the head. In addition to an MRI, patients will also have a or bending forward may bring on these headaches. Treatment and management There may be pain in the neck or upper arm with The recommended treatment for an Arnold-Chiari I Arnold-Chiari malformations. Patients often report more malformation is surgery to relieve the pressure on the pain on one side, rather than equal pain on both sides. During the surgery, the surgeon removes There may also be weakness in the arm or hand. This enlarges may also report tingling, burning, numbness, or pins and and decompresses the posterior fossa. If they find that brain tissue common complaint linked with Arnold-Chiari malforma- is blocking the flow of cerebrospinal fluid, they will tions is hoarseness. GALE ENCYCLOPEDIA OF GENETIC DISORDERS 103 Downward displacement and hypoplasia of cerebellum Obliteration of cisterna magna Normal Affected A characteristic change that occurs in patients with Arnnold-Chiari syndrome, type II, is the downward positioning of the cerebellum. Full recovery from surgery congenita may take several months, during that time, patients may Definition continue to experience some of the symptoms associated with Arnold-Chiari malformations. Prognosis for Arnold- Arthrogryposis multiplex congenita (AMC) is a term used to describe the presence of two or more (multiplex) Chiari II malformations depends on the severity of the joint contractures (arthrogryposis) present at birth (con- myelomeningocele and will be equivalent to that of spina genita). PO Box Four of these are syndromes that include AMC as a set of 8923, New Fairfield, CT 06812-8923. Arteriohepatic dysplasia (AHD) see Alagille • Type 2 DA: down slanting of the opening between the syndrome upper and lower eyelids (palpebral fissures), a small 104 GALE ENCYCLOPEDIA OF GENETIC DISORDERS mouth with pursed lips and malformations of the nose that cause a whistling appearance upon breathing, a cur- KEY TERMS vature of the spine (scoliosis), and some instances of mild developmental retardation. Type 2b DA, is charac- Amniotic fluid—The fluid which surrounds a terized by those characteristics of type 2 DA accompa- developing baby during pregnancy. Cell—The smallest living units of the body which • Type 5 DA: contractures of the arms and legs, limited group together to form tissues and help the body eye movement, deep set eyes, and abnormal coloring of perform specific functions. Contracture—A tightening of muscles that pre- vents normal movement of the associated limb or • Type 6 DA: camptodactyly, an abnormally small head other body part. Distal arthrogryposis—A disorder characterized by contractions of the muscles in the hands. Flexion creases—The lines present on the palms of the hands and the soles of the feet from normal • Type 8 DA: contractures of the wrist and/or ankles, bending of these body parts. Palpebral fissures—The opening between the The four syndromes that include arthrogryposis as a upper and lower eyelids. Cerebrooculofacioskeletal (COFS) syndrome is Talipes equinovarus—A type of clubfoot charac- characterized by an abnormally small head (micro- terized by a downward and inward pointing foot. Adducted thumb-clubfoot child is born with three copies of chromosome syndrome is characterized by clubfoot (equinovarus tal- number 18 and as a result is affected with multiple birth defects and mental retardation. Saethre-Chotzen syndrome is character- examines the tissue and bone structures of an indi- ized by flattened facial features, wide set eyes vidual or a developing baby. Type 8 DA may also be transmitted as a toes (syndactyly), congenital heart defects, and contrac- recessive or an X-linked disorder. Arthropathy-camptodactyly- linked to an autosomal dominant gene on the long arm of pericarditis syndrome is characterized by contractures of chromosome 5, localized to 5q23-q31. Adducted thumb-clubfoot syndrome The other forms of AMC include three relatively has DA that has not been localized to a particular chro- common forms: X-linked arthrogryposis, neurogenic mosome but it is transmitted through a recessive trait. Arthropathy-campto- and arthrogryposis in the lower limbs, and lethal congen- dactyly-pericarditis syndrome has been linked to an ital contracture syndrome. X-linked arthrogryposis is an X-linked trait caused Amyoplasia is the mildest form of arthrogryposis; it is by a mutation on a gene that has been localized to generally sporadic in appearance.
Feeding intolerance is characterized by vomiting 160mg malegra dxt plus visa, abdominal distention generic malegra dxt plus 160 mg with mastercard, diarrhea, or high gastric residual volumes. Complications of Enteral Nutrition Diarrhea: Diarrhea occurs in about 10–60% of patients receiving enteral feedings. The physician must be certain to evaluate the patient for other causes of diarrhea. Formula- related causes include contamination, excessively cold temperature, lactose intolerance, os- molality, and an incorrect method or route of delivery. Constipation: Although less common than diarrhea, constipation can occur in the enter- ally fed patient. Patients with ad- ditional requirements may benefit from water boluses or dilution of the enteral formulation. Aspiration: Aspiration is a serious complication of enteral feedings and is more likely to occur in the patient with diminished mental status. Further evaluate any patient who may have aspirated or who is assessed as being at increased risk for aspiration prior to instituting enteral feedings. Such patients may not be candidates for gastric feed- ings, and small-bowel feedings may be necessary. Drug Interactions: The vitamin K content of various enteral products varies from 22 to 156 mg/1000 Cal. This can significantly affect the anticoagulation profile of a patient re- ceiving warfarin therapy. Tetracycline products should not be administered 1 h before or 2 h 11 after enteral feedings to avoid the inhibition of absorption. Similarly, enteral feedings should be stopped 2 h before and after the administration of phenytoin. POSTOPERATIVE NUTRITIONAL SUPPORT Most patients can be started on oral feedings postoperatively, the question is when to begin them. Motility is delayed in patients un- dergoing laparotomy, whereas feedings begin fairly quickly for patients who undergo surgery on other parts of the body, once they recover consciousness sufficiently to protect their airway. Remember that the gut recovers motility as follows: The small intestine never loses motility (peristalsis is observed in the OR), the stomach regains motility about 24 h postoperatively, and the colon is the last to recover at 72–96 h postoperatively. Thus, by the time a patient reports flatus, one can assume that the entire gut has regained motility. Feed- ings then begin, depending on the exact operation performed and the resulting gastrointesti- nal anatomy. Patients who are to begin oral feedings are usually started on clear liquids (see Table 11–1). As long as the patient is willing to eat regular food, there is no reason not to progress to a regular diet rapidly (after one meal of clear liquids), and there is no need to step through a progression from clear liquids to full liquids to a regular diet. INFANT FORMULAS AND FEEDING Bottle feeding is often chosen by the mother and, in general, commercially available formu- las are recommended over homemade formulas because of their ease of preparation and their standardization of nutrients. Occasionally, special formulas are medically indicated and can only be supplied by commercially available formulas. Phytates can bind calcium and cause Nursoy (lactose-free) rickets Protein hydrosylate formulas Nutramigen Term infants: Gut sensitivity to proteins, multiple food allergies, persistent diarrhea, galac- tosemia. Pregestimil Preterm and term infants: disaccharidase defi- ciency, diarrhea, GI defects, cystic fibrosis, food allergy, celiac disease, transition from TPN to oral feeding Alimentum Term infants: protein sensitivity, pancreatic insuf- ficiency, diarrhea, allergies, colic, carbohydrate and fat malabsorption Special formulas Portagen Preterm and term infants: pancreatic or bile acid insufficiency, intestinal resection Similac PM 60/40 Preterm and term infants: problem feeders on standard formula; infants with renal, cardio- vascular, digestive diseases that require de- creased protein and mineral levels, breast- feeding supplement, initial feeding (continued) 11 Diets and Clinical Nutrition 225 TABLE 11–7 (Continued) Formula Indications* Premature formulas Low osmolality Similac Special Premature infants (<1800–2000 g) who are Care 20 growing rapidly. Vitamin and Preemie SMA 20 mineral concentrations are higher to meet the needs of growth. Isoosmolar Similac Special Same as for low-osmolality premature formulas Care 24 Enfamil Special Care 24 Preemie SMA 24 *Multivitamin supplementation such as Polyvisol (Mead Johnson) ¹ ₂ mL/d may be needed for commercial formulas if baby is taking <2 oz/d. Norwalk, CT, Appleton & Lange, 1999 Principles of Infant Feeding Criteria for Initiating Infant Feeding: Most normal full-term infants are fed within the first 4 h after birth. The examination should be normal with normal bowel sounds and a nondis- tended, soft abdomen. The infant should be tolerating extubation well and have little respiratory distress. Prematurity: Considerable controversy remains concerning the timing of initial enteral feeding for the preterm infant. For the stable larger (>1500 g) premature infant, the first feeding may be given within the first 24 h of life. Early feeding may allow the release of en- teric hormones that exert a trophic effect on the intestinal tract. No established policies are available, and delay and duration of delay in establishing feeding with those conditions varies for every institution. In general, enteral feeding is started in the first 3 d of life, with the objective of reaching full enteral feeding by 2–3 wk of life. Parenteral nutrition including amino acids and lipids should be started at the same time to provide for adequate caloric intake. Breast-feeding has many advantages: It is ideal for virtually all infants, produces fewer infantile allergies, is immunoprotective to the infant due to the presence of immunoglobulins, is convenient and economical, and offers several theo- retical psychologic benefits to both the mother and child. Occasionally, an infant cannot be breast-fed due to extreme prematurity or other problems such as a cleft palate. If commercial infant formula is chosen, no special considerations are needed for normal full-term newborns. The majority of infant formulas are isoosmolar (Similac 20, Enfamil 20, and SMA 20 with and without iron).
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