By V. Marlo. Southwest Bible College and Seminary.
M ixed acid-base disorders are frequent- illustrated: the underlying pathophysiology discount malegra dxt 130mg amex, secondary ly observed in hospitalized patients order 130mg malegra dxt visa, especially in the critically ill buy cheap malegra dxt 130mg online. For each disorder the following are peutic principles buy malegra dxt 130mg without prescription. Respiratory Acidosis FIGURE 6-1 Arterial blood [H+], nEq/L Q uantitative aspects of adaptation to respiratory acidosis. H ypercapnia elic- 40 its adaptive increm ents in plasm a bicarbonate concentration that 50 should be viewed as an integral part of respiratory acidosis. An im m ediate increm ent in plasm a bicarbonate occurs in response to hypercapnia. This acute adaptation is com plete within 5 to 10 m in- 40 30 utes from the onset of hypercapnia and originates exclusively from acidic titration of the nonbicarbonate buffers of the body (hem o- globin, intracellular proteins and phosphates, and to a lesser extent 30 plasm a proteins). W hen hypercapnia is sustained, renal adjust- 20 Normal m ents m arkedly am plify the secondary increase in plasm a bicar- bonate, further am eliorating the resulting acidem ia. This chronic 20 adaptation requires 3 to 5 days for com pletion and reflects genera- 10 tion of new bicarbonate by the kidneys as a result of upregulation of renal acidification. Average increases in plasm a bicarbonate 10 and hydrogen ion concentrations per m m H g increase in PaCO 2 after com pletion of the acute or chronic adaptation to respiratory acidosis are shown. The black ellipse near the center of the figure indicates the norm al range for the Steady-state relationships in respiratory acidosis: acid-base param eters. N ote that for the sam e level of PaCO , average increase per mm Hg rise in PaCO 2 2 the degree of acidem ia is considerably lower in chronic respiratory [HCO–] mEq/L [H+] nEq/L acidosis than it is in acute respiratory acidosis. Acid-base values falling outside the areas in color denote the pres- ence of a m ixed acid-base disturbance. Conservation of these new bicarbonate ions is ensured by the gradual augmentation in the rate of renal bicar- bonate reabsorption, itself a reflection of the hypercapnia-induced increase in the hydrogen ion secretory rate. A new steady state emerges when two things occur: the augmented filtered load of bicar- bonate is precisely balanced by the accelerated rate of bicarbonate reabsorption and net acid excretion returns to the level required to offset daily endogenous acid production. The transient increase in net acid excretion is accompanied by a transient increase in chloride excretion. Thus, the resultant ammonium chloride (NH4Cl) loss gen- erates the hypochloremic hyperbicarbonatemia characteristic of chronic respiratory acidosis. Hypochloremia is sustained by the persistently depressed chloride reabsorption rate. The specific cellular mechanisms mediating the renal acidification response to chronic hypercapnia are under active investigation. Available evidence sup- ports a parallel increase in the rates of the luminal sodium ion– + + + - hydrogen ion (Na -H ) exchanger and the basolateral Na -3HCO3 cotransporter in the proximal tubule. However, the nature of these adaptations remains unknown. The quantity of the H+-adenosine triphosphatase (ATPase) pumps does not change in either cortex or medulla. However, hypercapnia induces exocytotic insertion of H+- 0 1 2 3 4 5 ATPase–containing subapical vesicles to the luminal membrane of Days proximal tubule cells as well as type A intercalated cells of the cortical and medullary collecting ducts. New H+-ATPase pumps thereby are FIGURE 6-2 recruited to the luminal membrane for augmented acidification [6,7]. Renal acidification response to chronic hypercapnia. Sustained hyper- Furthermore, chronic hypercapnia increases the steady-state abun- - capnia entails a persistent increase in the secretory rate of the renal dance of mRNA coding for the basolateral Cl— H CO3 exchanger tubule for hydrogen ions (H+) and a persistent decrease in the reab- (band 3 protein) of type A intercalated cells in rat renal cortex and sorption rate of chloride ions (Cl-). Consequently, net acid excretion medulla, likely indicating increased band 3 protein levels and there- (largely in the form of ammonium) transiently exceeds endogenous fore augmented basolateral anion exchanger activity. Progressive narcosis and coma may occur in patients receiving uncon- Central Nervous System Respiratory System Cardiovascular System trolled oxygen therapy in whom levels of Mild to moderate hypercapnia Breathlessness Mild to moderate hypercapnia arterial carbon dioxide tension (PaCO2) Cerebral vasodilation Central and peripheral cyanosis Warm and flushed skin may reach or exceed 100 mm Hg. The Increased intracranial pressure (especially when breathing Bounding pulse hemodynamic consequences of carbon Headache room air) Well maintained cardiac dioxide retention reflect several mecha- Confusion Pulmonary hypertension output and blood pressure nisms, including direct impairment of Combativeness Diaphoresis myocardial contractility, systemic vasodila- Hallucinations Severe hypercapnia Cor pulmonale tion caused by direct relaxation of vascular Transient psychosis Myoclonic jerks Decreased cardiac output smooth muscle, sympathetic stimulation, Flapping tremor Systemic hypotension and acidosis-induced blunting of receptor Severe hypercapnia Cardiac arrhythmias responsiveness to catecholamines. The net Manifestations of pseudotumor cerebri Prerenal azotemia effect is dilation of systemic vessels, includ- Stupor Peripheral edema ing the cerebral circulation; whereas vaso- Coma constriction might develop in the pul- Constricted pupils monary and renal circulations. Salt and Depressed tendon reflexes water retention commonly occur in chronic Extensor plantar response hypercapnia, especially in the presence of Seizures cor pulmonale.
Extracellular Fluid Volume Homeostasis in Chronic Renal Failure FIGURE 2-40 35 Relation between glom erular filtration rate (GFR) and fractional sodium (N a) excretion 30 (FEN a) purchase 130mg malegra dxt amex. Adaptations in chronic renal failure m aintain 25 urinary N a excretion equal to dietary intake until end-stage renal disease is reached buy cheap malegra dxt 130 mg line. To achieve this 130mg malegra dxt sale, the FEN a m ust increase as the GFR decreases order 130 mg malegra dxt fast delivery. Com pared with norm al M ild CRF 17 13 persons, patients with CRF have expanded ECF volum e at norm al Severe CRF 12 N a intake. Furtherm ore, the tim e necessary to return to neutral 16 balance on shifting from one to another level of N a intake is 11 increased. Thus, whereas urinary N a excretion equals dietary 10 intake of N a within 3 to 5 days in norm al persons, this process 15 9 m ay take up to 2 weeks in patients with CRF. This tim e delay 8 m eans that not only are these patients susceptible to volum e over- 14 load, but also to volum e depletion. This phenom enon can be m od- 7 eled sim ply by reducing the tim e constant (k) given in the equation 13 6 in Figure 2-2, and leaving the set point (A0) unchanged. W alser M : Phenom enological analysis of renal regulation of sodium 12. Briggs JP: W hys and the wherefores of juxtaglom erular apparatus and potassium balance. Sim pson FO : Sodium intake, body sodium , and sodium excretion. Barajas L: Architecture of the juxtaglom erular apparatus. H ypertension: Pathophysiology, D iagnosis and Treatm ent. Luft FC, W einberger M H , Grim CE: Sodium sensitivity and resistance Laragh JH , Brenner BM. Skott O , Briggs JP: Direct dem onstration of m acula densa m ediated 4. Guyton AC: Blood pressure control: special role of the kidneys and renin secretion. H all JE, Guyton AC: Changes in renal hem odynam ics and renin 5. Lassiter W E: Regulation of sodium chloride distribution within the release caused by increased plasm a oncotic pressure. In The Regulation of Sodium and Chloride 1976, 231:1550. Bachm ann S, Bosse H M , M undel P: Topography of nitric oxide syn- 1990:23–58. H all JE, Jackson TE: The basic kidney-blood volum e-pressure regula- tory system : the pressure diuresis and natriuresis phenom ena. Johnson RA, Freem an RH : Renin release in rats during blockade of Arterial Pressure and H ypertension. Gonzalez-Cam poy JM , Knox FG: Integrated responses of the kidney gene expression by nitric oxide is counteracted by tonic inhibition to alterations in extracellular fluid volum e. Funder JW : M ineralocorticoids, glucocorticoids, receptors and York: Raven Press; 1992:2041–2097. H all JE, Brands M W : The renin-angiotensin-aldosterone system s. N áray-Fejes-Tóth A, Fejes-Tóth G: Glucocorticoid receptors m ediate The Kidney: Physiology and Pathophysiology, edn 2. Edited by Seldin m ineralocorticoid-like effects in cultured collecting duct cells.
Fortunately buy generic malegra dxt 130 mg, data (also referred to as mendelian disorders) there is a simple generic malegra dxt 130 mg without prescription, and technologies provided by the U cheap 130mg malegra dxt amex. Human Genome direct relationship between variation in a single gene and Project (HGP) generic 130 mg malegra dxt visa, including provision of the complete se- the phenotype that results. Thus, all patients with a given quence of the human genome, will greatly facilitate identifi- mendelian disorder, such as cystic fibrosis, will carry abnor- cation of such genes (1,2). This chapter describes how tech- mal genotypes at a single disease locus. In contrast, the rela- nologic advances in genomics will shape the future of tionship between phenotype and genotype is not straightfor- psychiatric genetics and psychopharmacogenomics, fields ward for complex genetic traits. In this setting, multiple that may establish an objective basis for the restructuring different susceptibility genes and environmental factors in- of the nosology, diagnosis, and treatment of psychiatric dis- teract in varying combinations within individuals who ap- orders. The results of genetic studies of particular psychiatric pear to have clinically indistinguishable phenotypes. This disorders and of responses to specific drugs are considered means that in any given sample of patients diagnosed with in other parts of this book. Fortunately, there are strategies for finding genes contrib- L. Freimer: Department of Psychiatry and Neurogenetics Laboratory, University of California–San Francisco, San Fran- uting to complex traits that have been successfully applied cisco, California 94143. One approach is to try to reduce loci of interest, with the expectation that they will share genetic heterogeneity in the patient sample by studying ge- this information with the scientific community. For in- netically isolated populations or by narrowing the affected stance, SNP variants in the coding or regulatory regions phenotype under study based on criteria of severity or the of genes (cSNPs) may cause functional differences in gene presence of a biological marker for the disease. With such variants catalogued in advance, it will approach is to greatly expand the sample size and number be relatively straightforward to test multiple candidate genes of DNA markers used in genetic association studies to in- for association with a disease phenotype or a pharmacoge- crease the power to detect multiple possible genes contribut- netic effect. The enormous task of identifying and scoring ing to disease in subsets of the sample. In either case, both SNPs in large samples, or performing the projected high- pedigree and population-based genetic mapping studies are density genome screening studies, has necessitated the devel- expected to yield more promising results in the future due in opment of high-throughput technologies such as DNA part to the extensive characterization of the human genome chips (6), which are discussed elsewhere in this volume. The HGP, begun in 1990, is a joint effort coordinated by the U. Department of Energy and Principles of Genetic Mapping:The the National Institutes of Health, with the cooperation in Search for Identity by Descent recent years of international entities such as the Wellcome Trust in Great Britain (3). The next subsection describes how innovations in ge- disease gene under study. The principle behind this expecta- netic maps and the structure of genetic mapping studies tion is best illustrated by considering genetically isolated or may eventually lead us to identify the as yet elusive genes founder populations (7,8). A founder population descends for psychiatric disorders. The shared segment includes the markers that sand markers spaced at roughly 1 to 5 centimorgans (cM); flank the disease gene. These markers are said to be linked 1 cM is a unit of genetic distance equivalent to a recombina- to the gene since, because of their close physical proximity, tion frequency between two loci of 1%, i. Detection of linkage is the goal are under construction now, however, as part of the HGP. Alternatively, if alleles at In fact, a major goal of the HGP is to characterize the extent markers co-occur more frequently than expected given the of genetic variation that exists among humans in order to known allele frequencies and recombination fraction be- create a map of several hundred thousand markers to enable tween the markers, they are said to be in linkage disequilib- high-density genome screening studies of complex traits (4). Evidence of LD between markers also indicates Differences in single bases of DNA known as single nucleo- that they are probably close to each other. If LD is observed tide polymorphisms (SNPs) are thought to constitute between the same markers over a region greater than occurs roughly 90% of sequence variation in humans. Occurring at random in a sample of patients, it may indicate that they at an average spacing of 1 SNP per 1,000 base pairs (1 share this segment of DNA IBD and that it harbors a disease kilobase, kb), they will thus constitute the majority of the gene.
8 of 10 - Review by V. Marlo
Votes: 232 votes
Total customer reviews: 232