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Nasogastric and nasojejunal tubes are long fine-bore tubes with a large surface area for potential drug absorption and may block easily due to their small bore. Percutaneous endoscopic gastrostomy, and jejunostomy tubes are short tubes with a wider bore.
When administering medicines via a tube that ends in the jejunum, sterile water should be used because the acid barrier in the stomach is by-passed. Drug absorption may be unpredictable if the tube extends beyond the drug's main site of absorption (e.g. cefalexin, ketoconazole).137 There is a higher risk of diarrhoea with sorbitol-containing liquids and hypertonic solutions when administered directly into the jejunum as the buffering effect of the gastric contents is lost.26,155,245,593
The material from which the tube is made can have an effect on the frequency of tube occlusion. Polyurethane tubes have been found to be less likely than silicone tubes to cause clotting of the enteral feed solution.442
| French Size | Inner diameter (mm) |
|---|---|
| 5 | 1.10 |
| 6 | 1.37 |
| 8 | 1.96 |
| 10 | 2.54 |
| 12 | 2.67 |
Tube tips can easily become dislodged by movement. Tube tip position should be tested using pH indicator paper, or according to local guidelines. Blue litmus paper is no longer considered to be appropriate for use, as it may not distinguish between bronichial and gastric placement.118
Tube tip position is most accurately checked by radiography, but in order to minimise exposure to radiation and to reduce handling of the patient, pH testing is the preferred method for most patients (excepting neonates). pH indicator strips should have 0.5 gradations and a range including 1-6. It is particularly important to be able to distinguish at the pH 5-6 range.120
Tube tip position should be checked120 : -
Patients on antacids, H2 antagonists, or proton pump inhibitors may have gastric aspirates with pH of 6 or above. Seek advice and alternative methods of checking tube tip position in these patients if aspirate pH is high.120
An appropriate enteral syringe should be used for administration of medication. Intravenous syringes should NOT be used due to the risk of accidental parenteral administration. The use of intravenous syringes has led to fatalities when medications for enteral use have been accidentally given intravenously.
ISO 80369-3 enteral syringes have a substantial dead-space at the tip, which should not be allowed to fill with liquid medicine. If this space fills with liquid, and if the syringe is then connected to an enteral tube, there is a risk of overdosage and / or leakage (with resulting medicine waste and contamination of the area). The dead-space can be prevented from filling by the use of appropriate bottle adapters or medicine straws which are available from the syringe manufacturers.
ISO 80369-3 enteral syringes should generally not be used to administer liquid medicines orally. If it is necessary to use them orally (for instance whilst oral syringes are being obtained) it is essential to ensure that the dead-space does not fill with liquid medicine - this can be done by using the available bottle adapters or medicine straws. Enteral syringes should not be immersed ("dunked") in liquid medicine (the "cup-fill method") when doses are being drawn up.
Catheter-tipped syringes should not be used for measuring oral liquid medicines due to the large dead-space volume in the catheter tip. This can be up to 2mL in some cases, which can lead to doses in excess of those intended being administered to the patient.
Luer-tipped syringes should never be used to measure oral medicines, as this risks accidental connection of oral medication to intravenous catheters, and resulting intravenous administration and patient harm.
Dedicated oral syringes should be used to administer oral liquid medicines. The dead-space volume in these syringes is much smaller, but can still be significant for highly-concentrated drugs such as digoxin elixir when the dose volume is small. It is important to remember that the measured dose in these syringes is from the graduation mark to the base of the barrel - the tip of the syringe is designed to fill with liquid medicine, and should remain full after the dose has been given. This volume in the tip is in excess of the volume measured (i.e. it is not necessary to try and flush out the medicine which remains in the tip, and to do so would result in giving a dose in excess of what was intended).
Oral syringes are generally coloured to distinguish them from intravenous syringes. In centres where oral and enteral syringes are the same colour, the two should be stored separately and clearly labelled to avoid confusion. Oral syringes are not always sterile, and they may be re-used for the same patient. They should be clearly labelled with the patient details, washed in hot soapy water immediately after each use, and allowed to dry in air. Immunocompromised patients may require the use of sterile equipment to reduce infection risk.
Some enteral syringes are single-use only, and others can be re-used for the same patient. Immunocompromised patients and those with enteral feeding tubes which terminate in the jejunum should usually be managed with single-use, sterile syringes.
All equipment used for administering medicines must be cleaned in between each use to prevent cross-contamination of medicines. Particular care should be taken when handling drugs to which patients frequently suffer allergies, e.g. the penicillins.
For immunosuppressed patients, and all tubes which terminate in the jejunum, the tubes should be flushed with cooled freshly boiled water, or sterile water.697
Some medications may interact with ions in water, so where the monograph indicates, de-ionised water (e.g. water for injection, water for irrigation) should be used. A separate bottle should be used for each patient, and discarded at the end of 24 hours.
Enteral feed interactions with gastric acid have been associated with coagulation of the feed and tube occlusion. For this reason, it is recommended that if gastric contents are to be aspirated from an enteral feeding tube through which feed has previously been delivered, the tube should be flushed before and after aspiration.214 Some authors also recommend flushing the enteral feeding tube at the end of each period of feeding, as retrograde migration of gastric juices can occur, which may cause coagulation of any feed remaining in the tube.214
Some studies have shown that drug absorption is reduced when administered via enteral feeding tubes.555 Concommitant patient conditions (often those which may have resulted in the need for the enteral feeding tube in the first place) such as recent surgery, or acute illness, may also account for reduced absorption.
Some drugs have been used to try and aid gastric motility through their prokinetic side effects. Metoclopramide (10mg three times a day) and erythromycin (250mg two or three times a day, preferably by the intravenous route) are the most commonly used.90 Metoclopramide increases gastric emptying by contracting gastric smooth muscle.2
In patients with slow gastric emptying, it may be advisable to suspend nasogastric drainage / nasogastic suction following dosing for sufficient time to allow the dose to be absorbed.90
Medications should not be administered through enteral tubes on free-drainage.137
When a patient who was previously on oral medication has an enteral feeding tube fitted and is likely to have medication administered via this route, contact Pharmacy for advice.