Minocin
By H. Kasim. Creighton University. 2018.
Moreover effective 50mg minocin antibiotics for strep throat, normal blood pressures cheap minocin 50 mg online antimicrobial vs antiseptic, pain or anxiety may play a role symptoms such as headaches and sleep disturbances are in hypertension as can agitation from rapid weaning of often associated with hypertension and may improve sedation after prolonged intubation or other procedures. Sweating, Similarly, in the child hospitalized with severe reactive palpitations, and flushing are associated with states airway disease, frequent administration of beta-agonists of catecholamine excess such as that accompanies a may be problematic. Height, weight, and body mass index should be meas- Interventions in the neonatal period, such as placement ured to assess for poor growth or to document an over- of umbilical catheters, or periods of hypotension or weight state or frank obesity. As outlined earlier, the diminished effective volume, may lead to renal hypop- accurate measurement of blood pressure is an essen- erfusion and subsequent renal scarring. Upper urinary tial part of the physical assessment of the child with tract infections, and especially repeated episodes of suspected or confirmed hypertension. In children with pyelonephritis in the first few years of life, may pre- an unclear etiology to their hypertension, blood pres- dispose to renal parenchymal scars that lead to renin- sure should be measured in all four extremities. Blood pressure in the lower extremi- end-organ damage, such as left ventricular hypertrophy, ties that is not higher than measurements in the upper arteriolar narrowing and hyperreactivity, and structural extremity is suggestive of a coarctation or other nar- and functional measures of endothelial dysfunction rowing of the aorta and is often associated with dimin- such as elevated carotid intimal medial thickness and ished femoral pulses. Previous the physical exam should also include fundoscopic, studies have shown that children presenting with hyper- cardiovascular, pulmonary, and neurologic exams. Somers abdomen should be auscultated for abdominal bruits alocorticoid excess is suspected as plasma renin activ- that, although uncommon, can accompany renovascu- ity is typically suppressed. As these studies are typi- dence of a systemic disease that may explain the elevated cally sent out to reference laboratories, their values are blood pressure. Similarly, several genetic syndromes not helpful in the acute management of hypertension. These include neurofibromatosis (café-au-lait with the initial screening studies, prior to use of potent spots, axillary freckling, Lisch nodules), tuberous scle- vasodilatory antihypertensives. An ultrasound provides infor- stature, shield chest, upturned mouth, webbed neck), mation about differential renal size, hydronephrosis, and Williams syndrome (overfriendly personality, echotexture, and cystic change and, thus, is a good cognitive impairment, prominent ears). As the medical condition stabilizes, scarring needs to be confirmed or is highly suspected. A urinalysis should be performed Doppler study does not, however, rule out renal artery on a freshly voided urine sample and, if the dipstick is stenosis, especially stenosis in smaller segmental positive for blood or protein, should include microscopy arteries not appreciated well by Doppler. For example, tachy- careful ophthalmologic exam may also give information cardia in the absence of pain or agitation suggests as to the chronicity of the child’s hypertensive state. Plasma renin activity and aldosterone levels are In the child with sustained blood pressures exceeding the helpful only if their results are unequivocally low or 99th percentile, diagnostic evaluation and therapy need high. The tempo and urgency Chapter 12 Hypertension in the Pediatric Intensive Care Unit 177 Table 12. The blood pressure Sodium nitroprusside is a powerful arteriolar and should be lowered by 20–30% in the first 2–3 h. For decades, its rapid onset of action the blood pressure is in a range that is not acutely dan- with short half life has made it a first-line option for gerous for the patient, the blood pressure should be continuous antihypertensive infusion. Nitroprusside lowered more gradually to at least the 95th percentile acts as a donor of nitric oxide, which mediates its reference blood pressure over the next several days or potent vasodilatory characteristics. Patients with liver disease or reduced renal The choice of agent should focus on the presumed function should have cyanide levels followed. More underlying mechanism of the hypertension as well as specifically, thiocyanate levels should be monitored local custom and clinician’s familiarity with specific in patients on nitroprusside for more than 72h or in agents. Somers Additionally, nitroprusside may increase intracranial bypass surgery for congenital cardiac disease. Its toxicities are relatively limited but include reflex tachycardia and tachyphy- 12. This agent will likely and Esmolol find greater use given its therapeutic profile, espe- cially in children with hypertension who may also Labetalol may be used both via continuous infusion and benefit from increased renal perfusion. It is the only drug that is both limited clinician familiarity with its use may impact its an alpha- and beta-blocker. It should be used judiciously in children with other agents may be appropriate or effective. Hydralazine is a commonly used vasodilator with Esmolol is a selective beta-blocker used as a con- rapid onset that often can be titrated to achieve good tinuous infusion in children primarily in the setting of blood pressure control.
Amazon parrot (Amazona autum- plasia in the budgerigar (Melopsit- tumors in Japanese quail order minocin 50mg on line virus colorado. Avian Dis 30:241-244 minocin 50 mg discount antimicrobial 2013, the exocrine pancreas in pet, exotic, Am Vet Med Assoc 181:1396-1398, 6. Vet Rec 106:10-12, noma of the pharyngeal cavity in a erakis isolonche in the ceca of gallina- types of tumors in mammals and 1980. Bauck L: Pituitary neoplastic disease and cloacal prolapse in an orange- 35:321-327, 1991. Hochleithner M: Cystadenoma in an cell lines and transplantable tu- Pathol 13:98-103, 1976. Four cases of neoplasia in captive tomas in two domestic ducks (Anas undulatus): Clinical, pathomor- 18. Burstein H, et al: Viral aetiology of exercise: Abdominal mass in a male Neoplasia in free-flying ruffed grouse 93. Paul-Murphy J, et al: Malignant lym- of lipomatous growths in a hypothy- tologic study of avian osteopetrotic 1991, pp 583-596. J Am Vet Med Assoc neoplasms in non-domesticated Glioblastoma multiforme in a budg- 32:163-165, 1988. Spontaneous chromo- (Diagnosis: metastatic ovarian carci- the canary (Serinus canarius). Avian Dis 27:549-555, and a grey-cheeked parakeet (Broto- Med Assoc 191:451-452, 1987. However, the small size of the eye in C H A P T E R I companion birds and the striated sphincter muscle of the avian iris necessitate modified proce- dures to visualize the posterior segment of the eye. The key to effective evalu- ation is to develop a logical, consistent use of the 26 same pattern of examination for each eye. Before a bird is agitated by restraint, the eyes should be evaluated from a distance, noting whether the bird will fixate on moving objects, whether both pu- pils are the same size and whether there are any obvious abnormalities in the periorbital area (Figure 26. The detailed examination requires adequate restraint, and a darkened room will calm the bird and improve the illumination provided by a focal light source. Ocular discharge, conjunctival hyperemia or periorbital swelling can be an indication of a pri- mary ocular disorder or may occur secondary to si- David Williams nusitis or facial dermatitis (see Chapter 24). Some larger Psittaciformes may inflate a portion of their periorbital sinus as an aggressive gesture, creating a transient swelling in the periorbital region (Color 26. Collapse of the anterior chamber may occur in an otherwise normal eye following a period of head restraint or lateral recumbency during anes- thesia. Examination of the anterior segment can be per- formed with a bright pen light, a binocular loupe, an operating microscope, an ophthalmoscope set on +20 diopters or, ideally, a slit lamp (Figure 26. Key features to evaluate are the clarity of the cornea, the aqueous, the lens and the color and vascularization of the iris. Aqueous flare, as seen in uveitis, can be detected by looking for scattering of a slit light beam that is passing through the anterior chamber (Colors 26. A 28 diopter lens is particularly useful but results in an inverted image that requires some practice to interpret (courtesy of David Willaims). The most useful regime in raptors has been found to be vecuronium bromide solution (4 mg/ml) topically every five minutes for fifteen minutes (see Chapter 18). A 28 or 40 dioptre lens is useful to obtain a good field of view in the small avian eye. The lamp can also be used to facilitate evaluation slit-lamp provides excellent visualization of a large of oral and dermatologic lesions (courtesy of David Williams). Further testing can be used to confirm or refute the Retinal examination is difficult in many birds be- presence of suspicious lesions detected by gross ob- cause of the small size of the eye and the lack of servation. Corneal ulcerations can be detected by response of the avian iris to conventional parasym- staining with fluorescein dye. Mydriasis can be accom- Tests can be used on birds, although normal data for plished by intracemeral injection of d-tubocurarine psittacine birds have not been published. Conven- or by the frequent use of a freshly prepared topical 3 tional 6 mm-wide Schirmer tear test filter paper mg/ml solution of crystalline d-tubocurarine in strips have been found to be difficult to insert in the 0. The difference in tear production between species is presumably related to the size of the orbit and lacri- An understanding of the anatomy of the avian eye mal gland tissue.
Genetic predisposition cheap minocin 50 mg free shipping bacterial infection in stomach, emotional stress cheap 50 mg minocin with visa bacteria 600x, diet, hormones, and infection with yeast-like organisms have all been implicated. This recent observation has given increased credence to the infection theory of seborrheic dermatitis. Food Allergies Seborrheic dermatitis, although not primarily an allergic disease, has been associated with food allergies—67% of people with seborrheic dermatitis develop some form of allergy by 10 years of age. Since a large portion of the human biotin supply is provided by intestinal bacteria and since newborns have a sterile gastrointestinal tract, it has been postulated that the absence of normal intestinal flora may be responsible for biotin deficiency in infants. It must be used in combination with other B vitamins (pyridoxine, pantothenic acid, niacin, thiamine, etc. Nutritional Supplements Vitamin B6 Taking a drug that causes vitamin B6 deficiency (4-deoxypyridoxine) and placing rats on a vitamin B –deficient diet cause skin lesions indistinguishable from seborrheic dermatitis. Folic Acid and Vitamin B12 Oral treatment with folic acid has been only moderately successful; the best results are obtained with a special form, tetrahydrofolate. Botanical Medicines Aloe Vera Gel Aloe vera gel can be quite helpful when applied topically. In one double-blind trial involving people with seborrheic dermatitis, the application of a 30% crude aloe emulsion cream twice a day for four to six weeks produced improvements in scaling and itching in 62% of subjects, compared with improvements in only 25% of the placebo group. In a study of 126 patients, treatment with 5% tea tree oil shampoo produced a 41% improvement in severity vs. For adults, supplementing with large doses of vitamin B complex within a high- potency multiple vitamin is the key therapy. We also recommend optimal intake of essential fatty acids, using both flaxseed oil and fish oils. Otherwise, the recommendations in the chapter “A Health-Promoting Diet” should be followed. The most common predisposing factor in acute bacterial sinusitis is viral upper respiratory infection (the common cold). Nasal allergies and other factors that interfere with normal protective mechanisms may precede the viral infection and therefore are the more likely predisposing factors. The key point is that any factor that induces swelling or inflammation of the mucous membranes that line the nasal and sinus passages will predispose a person to bacterial sinusitis, as the environment that is produced serves as a suitable medium for bacterial overgrowth, with streptococci, pneumococci, staphylococci, and Haemophilus influenzae being the most commonly cultured bacteria. In chronic bacterial sinusitis an allergy is the most common cause; in 25% of cases there is an underlying dental infection. Therapeutic Considerations Although antibiotic therapy is the dominant treatment of acute and chronic bacterial sinusitis, it is of limited value. In a Cochrane review it was shown that although 80% of participants treated without antibiotics improve within two weeks, antibiotics have a small effect in patients with uncomplicated acute sinusitis who have symptoms for more than seven days. Studies indicate that among most patients with chronic sinusitis, perhaps as many as 84%, have allergies. Some particularly sensitive patients may need to have all pets removed, along with carpeting and featherbedding. Guaifenesin (also known as glycerol guiacolate) is a derivative of a compound originally isolated from beech wood that has expectorant and mucolytic properties and is available in many over-the-counter preparations. The goal with a mucolytic is to reduce the thickness and stickiness of the mucus to help promote effective clearance. Proteolytic (protein-digesting) enzymes may break down complex proteins at the site of inflammation, exert some antimicrobial effects, or act directly on mucus proteins. Trypsin, chymotrypsin, Serratia peptidase, and bromelain are the proteolytic enzymes that can break down mucus proteins and other proteins when they are administered topically. Of these enzymes, Serratia peptidase may be the most effective, while bromelain is probably the most popular and readily available. Serratia peptidase is an enzyme derived from bacteria that reside in the intestines of silkworms. It is also called “silkworm enzyme,” as it is the enzyme used to break down the cocoon of the silkworm. It is more powerful and has broader pH stability than the pancreatic enzymes chymotrypsin and trypsin.
Domestic turkey hens hen to enter the cock’s enclosure buy minocin 50 mg visa infection fighting foods, while preventing can be used to incubate the eggs of larger gallina- the cock from entering the hen’s area buy 50mg minocin with visa treatment for dogs dry eye. Small and fragile eggs should be placed effective method for breeding birds like the Common under Golden Pheasant hens, which are cautious Capercaillie. During the most attractive of several cocks and if only one cock last week of incubation, the eggs of tropical birds is available, breeding may not occur if the hen does being raised in dry climates should be moistened not like the cock. After hatching, the acoustic presence of other males is necessary to hen and chicks can be placed in a small enclosure stimulate display and mating behavior. Chicks are prone to chilling Most gallinaceous birds incubate eggs on the ground the first few days post-hatching and must have sup- and should be provided with flat trays containing plemental body heat from the attending hen. Tragopans, the Congo Peafowl, the Bronze-tailed Peacock Pheas- The disadvantages of foster parenting are: ant, the Crested Argus Pheasant, the Mikado Pheas- crushing of small fragile eggs by heavy or clumsy ant, the Salvadori’s Pheasant and the cracids nest in adults; trees. A box placed approximately 150 cm from the premature cessation of brooding if the natural ground and filled with hay and foliage can be used as incubation period of the foster hen is shorter than an artificial nest. Nests of ground- and tree-nesting birds should be inconspicuous to provide trauma or death of the chicks if the hen recognizes the pair with visual security but should be placed them to be strange (this is a particular problem such that the birds can easily look out. In one breeding season, an Australian by placing the eggs in an incubator for the last third Brush Turkey hen lays about 25 to 30 eggs. Generally, chicks that are to be released into Cracids the wild should be reared by a hen of the same Cracids are Central and South American species that species. Most nests are well For many pheasants, the percentage of carbon diox- hidden in a fork or branch of a tree, but some species ide in the incubator must be increased up to approxi- are ground-nesters. This is achieved by re- rough-shelled with wide pores and a uniform white ducing the intake of fresh air. Newly hatched chicks are immediately able to out of the incubator immediately after hatching. Behavior of ceous birds, owing to the uncommon brooding biology free-ranging birds is dramatically different from that of these birds. The brain volume of domes- parents but by solar heat, fermentation heat or geo- ticated turkeys is 35% smaller than that of their thermal energy. The eggs are thin-shelled and depression in the soil and may be padded with leaves, contain a large yolk that is rich in lipids. The chicks are able to fly at two weeks both sexes begin constructing an induction mound of age. Several hens, together with their offspring, out of foliage and earth when the air temperature typically associate in a flock in winter. The birds leave their mother before the next breeding hens lay their eggs every two to three days in pre- season. Eggs are deposited in a mound with New World Quail the pointed pole downwards, and they are not turned during incubation. Young birds are sexually mature by one year The birds may determine the temperature of the of age, in some species even earlier. Outside the mound, and perhaps other parameters, with the bill breeding season, the gregarious New World quail live or tongue. The incubation mound is ning of the breeding season, the older cocks become cooled when needed by scratching holes. The white Quail have become polygamous and it is possi- incubation period varies from 45 to 90 days, depend- ble to keep one cock with two hens, indicating the ing on the temperature in the mound. The chicks join their Hazelhen, Spruce Grouse and Blue Grouse are mo- brothers and sisters who have hatched at around the nogamous. Hens in cap- Marked Sexual Dimorphism28 tivity breed best when allowed to choose between two or more cocks. Genus Plumage Plumage Differences Identical Similar The cocks, which are housed in dif- ferent compartments of an aviary, Megapodiidae: may see and hear each other if there Alectura * Cocks have neck appendages are enough hiding places for the hens. The chicks of dif- Ortalis Voice of cock is deeper * ferent species can be distinguished by the varying color patterns on the Penelope * In some species iris colors differ head and back plumage. Most grouse Nothocrax In cocks the tracheal loop is palpable * are sexually mature at one year of age. Crossbreeding between differ- Pauxi * In hens, plumage is sometimes a red phase ent genera and species occurs in free- Phasianidae: ranging birds. Similarities in the ap- pearance and display behavior of Numidinae: hens seem to induce cocks to cross- (all genera) * Cock’s call has 3 syllables; hen’s call has 2 syllables breed.
Fertility rates of records concerning the parent’s reproductive and free-ranging birds may vary among species due to medical history and fate of any eggs or chicks purchase minocin 50mg without a prescription antibiotic alternatives. Fertility is normally oping an accurate and consistent record-keeping sys- reduced in older birds buy discount minocin 50mg line infection in the blood, in younger birds and at the tem and regularly scheduling on-site visits will help beginning and end of a breeding season. Infertility in identify factors that could explain incubation failures these cases may be a natural occurrence and not an (see Chapter 2). Reproductive information from each pair including Domestic poultry have been genetically selected to numbers of eggs per clutch, number of clutches per produce high fertility rates of approximately 95%. Hatchability Immaturity, pair incompatibility, normal species differences, normal rates can be calculated for individual pairs, separate occurrence as part of clutch, sexual inexperience, lack of early clutches, different species, eggs incubated naturally, learning, aviary disturbances, lack of social interaction, excess eggs incubated artificially and eggs that had various social interaction, homosexual pairs, lack of pair-bonding, asynchro- nous breeding condition, improper imprinting, infrequent matings. The more precise the Environmental: hatchability statistic, the more diagnostic the infor- Incorrect photoperiod, incorrect nest box design or nesting mate- rials, incorrect enclosure design, lack of visual barriers, excessive mation that is provided (Figure 29. In domestic fowl, the hatchability of naturally and artificially incubated fertile eggs approaches 85 to Medical: 90%. With companion and aviary birds, this figure Obesity, age (young or old breeders), inbreeding, vent feathers, drug therapy (causing vitamin deficiency or direct, decreased may be much lower, and ranges from 8% to 100% fertility), previous hormonal therapy (testosterone injections), have been discussed. The number of lethal or chromosomal abnormalities reported in companion bird species is low when com- The fertility rates of most free-ranging companion pared to domestic species. Evaluating fertility and birds have not been determined, although in some hatchability statistics from parents and sisters of species studies have indicated that fertility can be breeding males may help identify lethal or semi-le- quite high. Breeding tests may the potential for similar fertility rates but more commonly the rates are lower, probably due to a combina- tion of environmental and dietary factors. This cyclic produc- tion is probably related to environ- mental factors and not due to disease-related infertility. Avicultur- ists should establish their own fertil- ity rates and standardize data so that comparisons can be made among similar aviaries. Hatchability Hatchability rates are determined from eggs that were known to be fer- tile. The egg on the left was from a are calculated by finding the percent- normal unassisted hatch, and the chick from this egg was strong and developed normally post-hatching. Exposure to toxic compounds, either directly – Cooling after development has begun or in the food or water, should be considered. Behav- – Suffocation due to incorrect ventilation Inbreeding ioral problems including lack of pair-bonding, incon- Chromosome abnormalities sistent parental incubation and egg trauma in the Egg-transmitted infectious diseases nest may also cause hatchability problems. Total caloric intake and food selection – Riboflavin, vitamin B12, folic acid, biotin, manganese, behavior for each individual bird should be evalu- pyridoxine, pantothenic acid, phosphorous, boron, li- ated. Nutritionally deficient hens can produce eggs, noleic acid, vitamin K, vitamin D Secondary vitamin deficiencies but the low level of nutrients may prevent the eggs – Antibiotic therapy destroying vitamin-producing flora from hatching. The age of embryonic mortality will – Diet imbalances, inadequate food intake usually depend on the degree and type of deficiency Viral diseases Bacterial infections or toxicity. Fungal infections Egg jarring or shaking in the first trimester Severe hypovitaminosis A causes a complete cessa- Incubator faults tion of egg production. Vita- Malpositions min E deficiencies can cause lethal rings in which the – Inadequate or incorrect turning embryo is seen surrounded by a ring of separated – Abnormal egg size or shape – Incorrect incubator temperature tissue. Vitamin D3 deficiencies can cause small eggs Incubator faults with poorly calcified shells. Ultraviolet light expo- – Poor incubator ventilation sure may improve hatchability in these cases while – Egg cooling early in incubation – Inadequate or incorrect turning excess D3 may lead to a complete cessation of egg – Incorrect temperature production. Embryonic hemorrhage is common with – Incorrect humidity deficiencies in vitamins E and K. Vitamin K is also Incorrect hatcher temperature or humidity Long storage time pre-incubation involved with calcium transport, and vitamin K defi- Infectious disease ciencies can mimic the clinical signs associated with Nutritional deficiencies hypocalcemia. The calcium/manganese ratio regulates the rate of be required to establish whether such genes are sex- hatching, and imbalances of these minerals may linked or autosomal, dominant or recessive. Given the wide variabil- ity in the types of food (and thus the composition of Parental Factors these foods) consumed by free-ranging birds of differ- The medical history of each parent should be exam- ent species, it is not surprising that a single commer- ined to identify factors that may affect fertility and cially available diet cannot meet the needs of all hatchability. It is specu- eggs that are artificially incubated for the entire lated that breeding third and fourth generations of developmental period (Figure 29. The fact that companion bird species will result in higher fertility different hatchability rates exist between natural and hatchability rates in birds fed commonly avail- and artificially incubated eggs highlights the need able commercial diets (see Chapters 3 and 31).
The Netherlands Generally speaking discount minocin 50 mg without prescription antibiotics for uti for male, public health officers qualified in clinical forensic medicine minocin 50 mg free shipping antibiotics used to treat acne. Scotland In the larger centers, joint pediatric/police surgeon examinations are common. Serbia Physicians with forensic training are rarely involved in initial examination and assessment. Switzerland Younger than 16 yr: female gynecologist at University Children Hospital. Question I Who undertakes the forensic medical examination and assessment of alleged child victims of physical assault? The Netherlands Generally speaking, public health officers qualified in clinical forensic medicine. Scotland Mostly pediatricians but some evidence is based on findings of family physicians. Situation is somewhat improved, but still poor cooperation between clinicians and forensic doctors. Switzerland Younger than 16 yr: doctors at University Children Hospital (Trauma-X group). Older than 16 yr: doctors of Institute of Legal Medicine of University of Zurich (District Physician). Question J Is there a system in your country/state whereby individuals detained in police custody who appear to have (or do have) psychiatric disorder or mental health problems or learning disability may be assessed? They are likely to be referred to psychiatrists or, in the case of learning disability, to social workers and/or clinical psychologists. This may not be strictly observed until and unless there is a court order that may need to be obtained by relatives. Israel Yes Malaysia Yes The Netherlands Yes Nigeria Yes Scotland Variable picture. If suspect is detained on the order of the investigative judge, then may be examined by psychiatrist and/or psychologist when need. If mental health problems are apparent, case is remitted to a judge and detainee is examined by a forensic surgeon and a psychiatrist. Sweden It’s part of the “police doctors” duties, but many custodies do have access to psychiatric consultants. Switzerland Those who have known disorders are followed by a specialized forensic psychiatric/psychological service; others are reported by the guards. Question K In your country/state are there specialized units or locations where victims of sexual assault are examined or assessed? Response Australia Yes England and Wales Yes, but not full geographical coverage; tends to be in urban centers. Germany No Hong Kong There are purpose-built video interview and medical examination suites. India No Israel Yes Malaysia Some major hospitals have “one-stop centers” with protocols for managements, both short- and long-term. Serbia No South Africa Yes Spain Victims of sexual assault are examined in gynecology or pediatric units of large hospitals. Question L In cases of alleged assault by police, who examines the police personnel? Response Australia Forensic medical officers (report and documentation of injuries). The Netherlands Generally speaking, public health officers qualified in clinical forensic medicine. Spain A forensic surgeon as member of the Ministry of Justice (completely independent of the police). Switzerland Physicians of Institute of Legal Medicine, University of Zurich (District Physician). Response Australia Forensic medical officers (report and documentation of injuries). The Netherlands Generally speaking, public health officers qualified in clinical forensic medicine. Nigeria Medical officer in the local hospital; (if he is lucky to have the opportunity and guts to complain).
The fux is defned as the number of molecules that pass through a unit area in a unit time generic minocin 50 mg with visa fish antibiotics for human uti. Ordinary diffusion effec- tively scatters molecular species throughout the medium and is dependent on numerous factors including molecular size and properties of the solution discount minocin 50mg with amex antibiotics for uti and acne. Separation, however, is determined by the introduction of a further element such as a membrane or gel. These will affect diffusion coeffcients signifcantly, allowing molecular separation to occur, which in turn is limited by the available concentra- tion gradients. Forced diffusion describes the application of an external force which acts differently on the molecular species present facilitating separation. Thus in a 14 Type of Renal Replacement Therapy 177 dialysis machine separation is enhanced not only by the membrane but by concen- tration gradients (ordinary diffusion) but also by pressure changes through the application of blood pumps (forced diffusion). The rate at which molecular species cross the membrane depends on the membrane rejection coeffcient (σ) which is effectively zero for small species such as urea but approaches 1 for larger molecules such as albumin. The sieving coeffcient (Sc) is given by: Sc =−1 σ This can be determined by measuring the concentration of a given solute in the plasma water and the ultrafltrate. Thus a simple view of solute clearance (K) in convective treatments is the product of: K = Qf. Solute clearance using diffusion-based systems may be calculated from: K = QdoC× do /Cbi with Qdo and Cdo being the dialysate effuent fow and solute concentration in the effuent dialysate (that leaving the dialyser). In summary, diffusion provides the main basis for the separation of molecular species in dialysis aided by convection, whereas in fl- tration convection is aided by diffusion, and as such the two processes often act simultaneously with any division being somewhat artifcial. Forni 14 Type of Renal Replacement Therapy 179 Key Messages • Convection and diffusion are essential processes needed to drive molecular separation. In essence these can be simplisti- cally thought of as being continuous therapies, intermittent therapies and more recently hybrid technologies. Although each technique may have its proponents, there are advantages (and disadvantages! All extracorporeal tech- niques share many features including access to the circulation as well as an extra- corporeal circuit offering molecular separation the nature of which is technique dependent. There are many acronyms used when describing the various techniques to provide renal support. In intermittent haemodialysis, blood is pumped into a dialyser containing two fuid compartments with blood in the frst compartment being pumped along one side of a semipermeable membrane while a crystalloid solution (dialysate) is pumped along the other side in a contrafow fashion. As described, the concentration gradients of solute between blood and dialysate lead to the desired biochemical changes. In order to prevent fltration of the dialysate back into the bloodstream, this compart- ment is under negative pressure relative to the blood compartment. Forni Compared to continuous techniques, relatively high blood fows are used (200–400 mL/min) coupled with dialysate fow rates of 500–800 mL/min (see Fig. Such fows enable high solute clearance rates over a relatively short period of time which may be associated with complications in the critically ill patient. For example, rapid removal of urea during dialysis may be associated with the dialysis disequilibrium syndrome. This is a clinical phenomenon of acute central nervous sys- tem dysfunction attributed to cerebral oedema occurring during or just after renal replacement therapy. Although generally accepted that cerebral oedema plays a major role in the development of the dialysis disequilibrium syndrome, the defnitive patho- physiology is incompletely described [7, 8]. Of the mechanisms proposed, the increased urea removal from the plasma over that of the cerebrospinal fuid resulting in move- ment of water into the brain—the so-called reverse urea effect hypothesis—is probably the most universally accepted. Features of the dialysis disequilibrium syndrome include nausea, headache, vomiting, tremors and seizures [9]. There is no treatment as such for the dialysis disequilibrium syndrome, and despite a lack of evidence base, preventive measures include shorter session length, lower blood fow rates and use of smaller surface area flters. Perhaps, in critically ill patients, intermittent therapies result in higher rates of hypotension, which is signifcantly infuenced by the amount of fuid removal required during each dialysis session and often prevents achievement of desired fuid balance (Table 14. To minimize the adverse haemodynamic effects of inter- mittent therapies, several groups have described techniques whereby modifcations are made to avoid the dialysis disequilibrium syndrome as well as haemodynamic intolerance [10]. These include: • Limiting maximal blood fow at 150 mL/min with a minimal session duration of 4 h • Simultaneously connection of the circuit with a catheter primed with 0. Treatment of acute kidney injury in the renal unit, however, when present as single organ failure is almost exclusively delivered as intermittent therapies [11]. However, there continues to be a growing body of evidence which points to worse renal outcomes when intermittent therapies are employed in the critical care unit.
