Dehydrating agent and industrial dehydrating agent are commonly used in medicine or nursing.
(1) Hypertonic dehydrating agents can improveosmotic pressure, so that it is higher than the brain tissue, causing the osmotic pressure gradient between plasma and brain tissue, and water will move against the osmotic pressure gradient, and move from brain tissue to plasma, dehydrating brain tissue,Decreased intracranial pressure。Such drugs mainly include 20%mannitol, 30% sorbitol, urea, hypertonic glucose, etc.20% mannitol and 50% glucose are commonly used clinically.However, because the metabolic product of mannitol in the body can be converted into glucose, so for diabetes mellitusCerebral vascular diseaseShould be used with caution.
(2)diureticIt dehydrates the body mainly through diuresis, thus indirectly dehydrating brain tissue.At the same time, it can also inhibit the entry of Na+into normal and injured brain tissue andcerebrospinal fluid, reduce the formation rate of cerebrospinal fluidCerebral edema。Diuretics includeFurosemide, sodium diurate,Dihydrochlorothiazide，Aminopteridine, AcetazolamideFurosemide and Dihydrochlorothiazide are commonly used.
(3)steroidThe drug has good antidiuretic effect, and the effect is mild and lasting.Especially suitable for the whole bodystressLow function or accompanied byshockPatients with symptoms.Common drugs includedexamethasoneAnd hydrocortisone.But because dexamethasone can causeblood sugarIncrease andGastrointestinal bleeding, so, yesCerebral vascular diseasePatients with diabetes should also use it with caution.[1]
Common types
Announce
edit
There are many kinds, such as ethanol,acetone，glycerol，N-butanolAnd tert butyl alcohol, etc.The most commonly used is ethanol（alcohol）Glycerol is commonly used in fungi and algae.
alcohol
There are 95% and 100% (pure alcohol) alcohol sold in the market.High concentration of alcohol (more than 95%) has strong shrinkage and embrittlement defects on tissues, so the materials cannot be put into high concentration of alcohol immediately after washing.In order to avoid shrinking and rigidity of materials, they should be gradually dehydrated in different concentrations of alcohol.General organization (exceptNervous tissueIt can be dehydrated gradually from 70% alcohol to 80%, 95% and 100% alcohol.For some soft tissues, such as embryonic tissue, lowinvertebrateThe tissue should start from 50% or 30% or 20% below 70% alcohol, otherwise the tissue will shrink greatly.The above concentrations are often added with 95% alcoholdistilled waterIt is diluted instead of pure alcohol, because its price is too expensive.
stayalcoholAmong dehydrating agents, anhydrous alcohol is the highest concentration dehydrating agent. The biological laboratory of middle school usually uses the following method to produce anhydrous alcohol from 95~96% alcohol.Take the blue crystalline copper sulfate powder and bake it in the oven until the blue powder is dehydrated and turns bluish white.Put the bluish white copper sulfate powder into the alcohol (it turns blue when it meets water) until the added copper sulfate is not blue, indicating that the alcohol is anhydrous, and then bottle it for sealing.
Recovered alcohol
Alcohol for dehydration should be collected according to different concentrations after use.After receiving a certain amount, filter it and use alcoholHydrometerDetermine the concentration, and then use it to prepare all levels of low alcohol.If usedAlcohol concentrationLow, it should be used after distillation.
There are many chemical synthetic dehydrating agents in industry, such aspolyacrylamideEtc.[1]
Flame retardant
Announce
edit
Dehydrating agent is taken away during combustionIntumescent flame retardantThe moisture of the carbon forming agent in the can be reused during dehydration, so it can also be called the dehydration carbon forming catalyst.[2]
PAM
Announce
edit
Polyacrylamide (PAM) is water-solublePolymer, insoluble in most organic solvents, with goodflocculationIt can reduce the friction resistance between liquids. According to ionic characteristics, it can be divided into four types: non-ionic, anionic, cationic and amphoteric.
2. Adhesion:It can play the role of adhesion through mechanical, physical and chemical actions.
3. Resistance reduction:PAM can effectively reduce theFrictional resistanceThe resistance can be reduced by 50-80% by adding a small amount of PAM to the water.
4. Thickening property: PAM has thickening effect under neutral and acid conditions. When the PH value is above 10, PAM is easy tohydrolysis。In case of semi reticular structure, thickening will be more obvious.[1]
Technical process of PAM precipitation
Precipitation is a substance that is insoluble in the solution of reactants when a chemical reaction occurs.Literally, it means precipitation and removal under the action of gravity.SewageSuspended matterIt can be a physical process, which is easy to operate and has good effect. It is one of the important technologies for sewage treatment.
According to the nature and concentration of suspended substances and the coagulability of flocculating polyacrylamide, precipitation can be divided into:Natural precipitation，flocculent settling , regional sedimentation.The concentration of suspended particles precipitated in the domain is high (more than 5000mg/L), the sedimentation of particles is affected by other particles around, the relative position between particles remains unchanged, forming a whole common subsidence, and there is a clear muddy water interface with clarified water.Secondary sedimentation tankAndSludge concentrationRegional sedimentation occurs in the tank.
In waste waterSuspended solidsThe concentration is not high, and it does not have the ability of agglomeration. In the precipitation process, the solid particles do not change their shape, nor do they adhere to each other. They complete the precipitation process independently.（Grit chamberandPrimary sedimentation tankInitial sedimentation)Compression sedimentationIt occurs in the sedimentation process of high concentration suspended particles. Due to the high concentration of suspended particles, the particles have been squeezed into a block structure, contacted and supported each other. The water between the lower particles is squeezed out under the gravity of the upper particles, so that the sludge is concentrated.Secondary sedimentation tankIn sludge hopperpolyacrylamideCompression sedimentation exists in the thickening process and the sludge thickening process in the thickening tank.Free precipitationIt occurs when the concentration of suspended solids in the water is not high, and suspended solids do not interfere with each other during the sedimentation process. The particles are precipitated separately, and the sedimentation track of particles is straight.During the whole precipitation process, the physical properties of particles, such as shape, size and specific gravity, do not change.This particleGrit chamberThe precipitation in is free precipitation.
flocculent settling It refers to the process of flocculating and settling particles in water.After coagulant is added to waterSuspended solidsColloids and dispersed particles ofMolecular forceFlocs are formed under the interaction of,Settling velocityIncreasing.The removal rate of suspended solids depends not only on the sedimentation rate, but also on the sedimentation depth.Formed after adding coagulant to surface waterAlum flower，domestic sewageOrganic suspended solids in,activated sludgeFlocculation and sedimentation will occur in the sedimentation process.[1]
Sludge dewatering process
Domestic sewage is used for desliming according to different treatment methodsflocculant It is different.
Dewatering Agents
If the process subject adopts biochemical method, that isexcess sludge Dehydration (may contain some primary sludge) requires only cationic PAM as sludge dehydrating agent.
If the main body of the process adopts physical and chemical methods, such as primary strengthening, loading magnetic separation and other processes, generally PAC is added first for conditioning, and then anions are addedflocculant , add at the endCationic flocculantDehydration.The specific dosage shall be determined according to the quality of sewage.
When PAM is used as sludge dehydrating agent, the ratio between PAM and water should be between 0.1% and 0.2%.After dissolving into glue like liquid, it is added to sludge for mixing treatment.
The ratio to sludge is generally 5% - 10%, and some are lower. This should be determined according to the sludge concentration. It is better to determine the optimal dosage and use model through on-site beaker test.Different sludge, different agents, different equipment and different management levels have different treatment effects.[1]
Water treatment application
The application of PAM in water treatment industry mainly includes raw water treatment, sewage treatment and industrial water treatment.In raw water treatment, PAM can be used together with activated carbon to coagulate and clarify suspended particles in living water;In sewage treatment.PAM can be used forSludge dewatering；In industrial water treatment, PAM is mainly used as a prescription agent.In raw water treatmentOrganic flocculantPAM insteadinorganic flocculants Even if the sedimentation tank is not modified, the water purification capacity can be increased by more than 20%.Therefore, many large and medium-sized cities use PAM as a supplement when the water supply is tight or the water quality is poor.Industrial wastewater treatment, especially for suspended particles, coarse particles, high concentrations, particles with positive chargesPH valueNeutral or alkaline sewage, steel plant wastewater,Electroplating factoryWastewater, metallurgical wastewater,Coal washing wastewaterAnd other sewage treatment, with the best effect.In sewage treatment, PAM can increase the utilization rate of water recycling.[1]
Clinical application of dehydrating agent in cerebrovascular disease
Announce
edit
Dehydrating agents were mostly used in patients with cerebral hemorrhage before 1980s, but less used in patients with cerebral infarction. Dehydrating agents have become hemorrhagic orIschemic cerebrovascular diseaseRoutine medication.And some scholars believe that the excessive dosage of dehydrating agent applied in the acute stage of cerebral hemorrhage reduces the mechanical pressure of edema tissue on the bleeding focus after massive dehydration of brain tissue, which can aggravate bleeding.Recently, some scholars believe that although there are different degrees ofIntracranial hypertensionPhenomenon, but most of them are relatively light, which can be balanced through self metabolism of the body.If the intracranial pressure is not high or light, the use of large doses of dehydrating agent will seriously interfere with the balance of normal intracranial pressure, bringing immeasurable consequences for rehabilitation.The main reason of acute stage of cerebral infarction patients is ischemia and hypoxia of brain tissue and insufficient blood supply to the brain, so it should be used appropriately to get twice the result with half the effort.[3]
Function of dehydrating agent
1. Dehydration agent is valuable for controlling cerebral hernia. It can help more than half of cerebrovascular patients overcome the threat of cerebral hernia and prolong the survival time of patients with cerebral hemorrhage.
2. The function of dehydrating agent is to help the body stop or reverse the development of brain hernia or reset the early brain hernia when the body can not transfer the intracranial pressure to regain balance through its own compensatory mechanism and the process of brain hernia development occurs.
3. Dehydration agent has no obvious effect on some patients with severe cerebral hernia, large amount of bleeding and rapid disease development.
4. Dehydration agent is powerless for the dehydration agent that has deep bleeding site, damaged the neural structure of the midline, and has been in a coma for a long time, combined with pulmonary infection.
5. Mannitol plays a better role in dehydrating agentCerebral vascular diseaseThe first choice in acute phase.[3]
Indications for application of dehydrating agent
To reasonably master the use of dehydrating agent, it is necessary to correctly judgeIntracranial hypertensionThe acute stage of cerebral hemorrhage can be distinguished as follows:
① Hemiplegia or hemiparesis, clear mind, headache and vomiting are not severe, although lumbar puncture shows bloodyCTIt is reported that the amount of bleeding is not large, and the intracranial pressure is not too high (below about 200 mmHg), indicating that the amount of bleeding is not large. In this case, the body of the patient is likely to compensate itself. You can give some 10% glucose instead of dehydrating agent, but you should closely observe the changes in the condition. If the intracranial pressure is not too high or within the normal range, if you give a strong dehydrating agent at this time, it will backfire,The balance of intracranial pressure was artificially disturbed, which reduced the normal intracranial pressure and increased the complexity of future treatment.
② If the headache and vomiting are severe or the condition gradually worsens during the observation, paralysis is complete or lethargy occurs, a half dose of 125ML dehydrating agent can be given,
③ When the patient came to the clinic, he or she became conscious or unconscious during the observation. CT showed that the midline structure was affected. At this time, the patient's coma was due to the relationship between brain edema and midline structure. A powerful dehydrating agent such as mannitol should be given.
④ After administration of dehydrating agent, the condition must be closely observed and compared with the condition before administration within 1-2 hours after the strongest dehydration effect, so as to make appropriate decisions on the evolution of pathological changes.As the basis for gradually reducing the number and dosage of medication.
⑤ Within 5-6 hours after administration, the patient's condition is stable and the signs are not increasing or decreasing, which indicates that the progress of the focus is not obvious. In combination with other prevention and treatment measures, the drug should be administered every 6 hours and closely observed for 24 hours. This scheme is a routine use for patients with cerebral hemorrhage.Generally, within 3 days of bleeding, even if the focus does not expand, edema around the focus exists to varying degrees or gradually worsens. At this time, careful observation for 24 hours. During this process, no evidence of focus expansion is found, which can indicate that the condition is stable. Dehydration drugs should be maintained for 72 hours, and then gradually stop using.However, in the process of drug withdrawal, when it is observed that there is rebound of dehydrating drugs, it is reasonable to extend the interval of administration and slowly stop using.In this case, with complications such as lung infection and symptoms such as deepening of consciousness disturbance, the application time of dehydrating drugs should be appropriately extended.
⑥ When the patient comes to the clinic, the condition worsens rapidly, and can be observed within 1-2 hours. At this time, the dehydration agent should be used again for observation. If the process of disease deterioration cannot be controlled after two times of continuous use of sufficient amount of dehydration agent, it means that the dehydration agent cannot effectively relieve oppression, and other measures should be considered for rescue.
⑦ If the aggravation process of the disease occurs slowly and only shows up after 5-6 hours, the dosage of dehydrating agent can be increased, or the intermittent period of administration can be shorteneddexamethasoneTry other methods, but be prepared for surgical treatment, so as to remove the hematoma before the brain hernia develops when the dehydration agent still cannot control the deterioration.
⑧ The Tathagata was in the pre hernias or hadTentorial notch hernia, push quietly immediatelymannitolSuch strong dehydrating agent, if the effect is reversed or the brain hernia recovers, continue to use the dehydrating agent once every 4 hours. If the symptoms do not improve or although they have improvedCerebral herniaThere are many patients of this kind who are in serious condition and have poor prognosis when they are given dehydrating agent again and prepared for surgery.[3]
