Enemas volume

At least 12 cases of perforation of the colon by barium enema, with four deaths, were reported in a series of publications (SED-12,1165) (6-8). The incidence of perforation was about 1 in 6000 examinations. Even sterile barium sulfate can cause marked peritoneal irritation, with considerable fluid loss into the peritoneal cavity, but in practice it is usually a mixture of barium and feces that escapes and this, not surprisingly, produces severe peritonitis and dense adhesions. Mortality has been reported to be 58% with conservative treatment, and as high as 47% with surgical intervention (9). Early operation is indicated, and large volumes of intravenous fluids improve the prognosis. Patients who recover can... 

Administration of hypertonic saline can result in hypernatremia and an expanded ECF volume. This is typically iatrogenic, and may follow administration of sodium bicarbonate, use of hypertonic saline enemas, or intrauterine injection of hypertonic saline. Rarely, patients with hyperaldosteronism spontaneously present with an expanded ECF and mild hypernatremia. ... 

To date the most effective therapeutic method is the use of high volume enema, as this ensures com-... 

A contrast medium like barium sulphate may be given as a suspension by a large volume enema for colon diagnostics. 

Rectal absorption depends on solubility and lipophilicity of the active substance (see further Sect. 16.1.5), and is influenced therefore by volume, pH, and buffering capacity of the enema (see Sects. 11.3 and 16.2.4). 

Formulation, volume and packaging should make an enema suitable for rectal use. As with suppositories, the form of the active substance, ionised or not, is primarily chosen with regard to optimal effectiveness. Figure 11.1 presents an overview of the choices to be made. 

The volume of enemas may vary from a few millilitres (micro-enema) to more than 100 mL, mainly depending on the intended effect systemic or local. For large-volume enemas water is commonly used and a water-soluble form of the active substance is preferred. The solubility may be increased by addition of co-solvents, to be applied in small volume enemas. If a soluble active substance or an adequate co-solvent cannot be found, a suspension may be prepared. If this is also not an option, a lipophilic vehicle may be chosen. Choice of pH depends on the chosen form of the active substance and is important for the absorption. Excipients may be added to correct the osmotic value, to increase the viscosity, to prevent oxidation or for preservation. 

In all enemas having a volume of more than 20 mL, water is used as the single vehicle. These enemas are intended for a local effect. The volume of these enemas usually exceeds 40 mL, see Sect. 11.9.3. 

Two vehicles have been proposed for diazepam enemas. Both are mixtures of water and co-solvents propylene glycol - ethanol 96 % - water (4+1+5, parts by volume, pH 4.8) and glycofurol - ethanol 96 % - water (5 + 1+4, parts by volume, pH 3.6). No significant difference in irritation score was observed with healthy volunteers [52]. 

Rectal irritation was studied also for various volumes of both mixtures 2.5 mL, 5 ttiL and 10 mL. Only a light irritation was observed in the first 5-10 min after administration, lasting longer at the largest volume. As a control water was administered in the same volumes all volumes were equally well tolerated. Choosing the smallest volume for enemas with these co-solvents seems best but may be insufficient for dissolution of the active substance. Regarding dissolution and irritation the optimal volume has to be chosen [52]. 

For a baby of 2 months a volume of 5 mL is very suitable for systemic action. For the volume of an enema for local action, e.g., a 0.9 % NaCl solution as a laxative the general rule applies [6] neonates <1 kg rectally 5 mL, and neonates >1 kg rectally 10 mL. 

In practice, if a systemic effect is intended, usually a solution enema with a small volume is applied. The lower limit is 3 mL, necessary for a correct administration without unacceptable loss. The upper limit is 20 mL, but usually a volume of 10 mL is not exceeded. Between 3 and 10 mL (eventually 20 mL) the volume is determined by the solubility of the active substance. 

The volume of enemas ranges from 3 to 100 mL. The volume is chosen on therapeutic, biopharmaceutical and... 

When administering an enema, it is almost impossible to transfer all liquid to the rectum. A small amount will always remain in the bottle or giving tube. Small enema bottles are therefore filled with an excess of liquid. The required excess depends on the model of the micro-enema bottle and on the physical properties of the micro-enema liquid, in particular the viscosity. The residual volume, and thus the required excess, can be determined by weighing a bottle, filling it and emptying it by squeezing, after which it is reweighed. 

In enemas for a local effect, usually having a higher volume, the residual volume is neglected. 

After preparation and packaging, enemas have to be checked for appearance, labelling and packaging. The final volume or the final weight must also be checked. Solutions must be clear and visually free from particles. For a suspension enema the resuspendability must be evaluated, which may be done following the method for oral suspensions, see Sect. 32.7.2. For other quality requirements see Table 32.2. 

The rectum is the lowest part of the large intestine. It is 15-20 cm long with a diameter of about 5 cm. In the rectum 1-5 mL of viscous fluid with a pH between 6.4 and 7.4 and a small buffer capacity is present. The temperature (under physiological conditions) is 36.2—37.6 °C. The rectum is a flat tube, because of the pressure of the bowels. After administration of a fluid into the rectum the Uquid will spread due to this pressure. Larger volumes (enemas) are spread into the colon as well. A defecation reflex will occur when volumes exceeding 100 mL are applied, which limits the volume of enemas. 

Rectal solutions have water or oil as a vehicle. If necessary to enhance the solubility of poorly soluble active substances, aqueous rectal solutirms may contain cosolvents, such as ethanol and propylene glycol. However, cosolvents and surfactants should only be used in limited amounts because of the potential irritation and the defecation reflex they may cause. For the rectal absorption of active substances from enemas the same mechanisms as for suppositories apply. A major advantage of a rectal solution over a suppository may be the fact that the active substance is already in a dissolved state which may increase the absorption rate. Increasing the volume of a rectal solution to dissolve a poorly water-soluble active substance will enhance the dissolution rate and thereby increase the absorption rate. Because of the higher volume more active substance will be dissolved and the membrane surface over which absorption occurs, is increased as well. 

Containers for liquid rectal preparations range in volume from several millilitres to approximately 100 mL. The container must be equipped with a rectal cannula to administer the enema. Enemas can be packaged in enema bags (see Sect. 24.4.13.2). These have a longer cannula with which the enema can be administered deeper into the rectum. Another possibility is to package an enema in a syringe on which a rectal cannula is placed (see Sect. 24.4.16). 

The microenema bottle (see Fig. 24.9) is meant for single-dose enemas with a volume of 3-10 mL. The bottle has a bellows design and is made from low-density polyethylene. 

When emptying the micro enema bottle some liquid remains in the bottle. Independent of the fill volume this loss is approximately 1.5 mL of aqueous solutions. When filling the bottle an excess volume is therefore required. When using a more viscous solution the loss in the single dose enema bottle will be greater. 

Table 24.8 Filling volume, delivered volume and dose in enema bottle 10 mL, for Chloral hydrate enema 50 mg/mL and 150 mg/mL FNA (see Table 11.15)...

The nominal content is 100 mL, the maximal fill volume 130 mL. Graduation indicates 50 mL, 75 mL and 1(X) mL. The closure consists of 4 parts a strong screw cap, a flexible cannula, a rubber one-way check valve in the screw cap and a cap. The cannula is usually lubricated with vaseline. The length of the cannula is 52 mm and the top is rounded. Due to the bellows design of the shoulder the bottle can bend which makes administration easier. Water loss by evaporation is relatively small in relation to the fill volume. After administration a small volume (<2 mL with a 100 mL enema) remains in the bottle. The enema bottle provides little protection against the influence of light, so the bottle should be wrapped in aluminium foil or packaged in a secOTidary container if necessary. 

In addition to being packaged in bottles, enemas can also be packaged in enema bags. Enema bags can contain a volume... 

For rectal administration of enemas the syringe is equipped with a rectal cannula. In this way a single strength solution can be administered in varying volumes. 

The basic equipment required for the CT colonography examination is little more than a red rubber catheter with a hand held insufflation bulb similar to that used for barium enema examinations. There are a variety of rectal catheters available of varying size, typically 5-15 mm in diameter. Although we routinely use a balloon-tipped enema catheter, many researchers now avoid balloon insufflation. Traditionally room air has been the gas of choice for colonic insufflation at CT colonography due to its availability and lack of additional expense. However, there is a growing body of evidence advocating the use of carbon dioxide (COj) which is associated with less abdominal cramps and is more rapidly reabsorbed (Yee and Galindo 2002). COj is supplied from a refillable cylinder via a disposable administration set which allows constant gas pressure influx with the facility to record both gas pressures and the volume of COj administered. 

A standard enema bag filled with approximately 31 of gas is an alternative to the plastic bulb insufflator (Fig. 5.4), and has the additional advantage of permitting manual insufflation of carbon dioxide. The bag (filled with air or carbon dioxide via a gas cylinder) is sealed with a plastic clip and attached to a rectal catheter via a connecting tube. Once the rectal catheter is in-situ, the clip is released and the bag is gently compressed over 2-3 min, insufflating the colon. Gentle insufflation improves patient tolerance and ultimately allows greater volumes of gas to be administered. If the bag is empty and more gas required, then the plastic seal can be opened and room air introduced. 

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