Part Three: Gastric Decompression
Last week we covered IV fluid resuscitation and pain relief. This week we will go into more detail about gastric decompression. There are two ways that gastric decompression can be achieved:
2) Stomach tube (orogastric tube) placement
The decision on which method to use depends on many factors: personal preferences, past experiences and clinical protocols to name a few.
So, which one is the best? A recent retrospective analysis of 116 gastric dilatation and volvulus (GDV) patients by Goodrich et al. (2013) found that both methods of gastric decompression had low complication and high success rates and that either technique is acceptable. If one method failed to achieve gastric decompression, the other can be attempted.
Personally, I use either or sometimes both. Which one I choose first depends on the situation. My decision-making process goes something like this:
Not clinically obvious or mild gastric dilation and volvulus:
These are often diagnosed based on supportive radiographic findings as history and presenting clinical signs made me suspicious of a GDV.
I would always attempt to pass a stomach tube in these patients first as the tube is more easily passed when the gastric distention is milder.
Although this procedure generally requires prior opioid analgesia administration to help reduce the stress, it can achieve rapid and lasting decompression of the stomach. I often leave the tube in throughout stabilisation, just prior to induction of anaesthesia for surgical correction of the torsion. The tube allows continual release of gastric gases which can reaccumulate rapidly if the tube is removed prior to surgery.
Obvious or severe gastric dilation and volvulus:
The abdomen in these animals is often distended and tympanic. I will perform trocarisation in these cases first as passing a stomach tube in these patients is often unsuccessful. It allows rapid gastric decompression which is particularly important in cases with evidence of respiratory compromise. After the trocar is no longer releasing gas, then I will pass a stomach tube. At this stage it is often easier to pass the stomach tube once the gastric pressure has been reduced. Once again, I often leave the tube in during stabilisation.
How to perform them:
– The main risk is hitting the spleen while attempting trocarisation. To avoid this, identify the most tympanic site by palpation or alternatively, use the ultrasound to confirm the absence of the spleen prior to trocarisation.
– A 3 inch 14g catheter is usually sufficient
– Clip and surgically prep a 10cm x 10cm area where you intend to place the catheter
– Insert the catheter to the hub and remove the stylet.
– Although local anaesthetic in the area is ideal, you will not have time to do this in most cases, especially the very unstable ones. Also, since I administer pure opioid agonist intravenously to most confirmed GDV cases on presentation, local anaesthetic is not required.
– Remove the stylet and gas should come blowing out under pressure
– Once the gas flow starts to slow down, gently applying inward pressure or pressure on the dilated stomach can help ensure that the stylet does not fall out of the stomach and as much of the gas is removed as possible.
– The main risk here is rupture of the oesophagus or the gastric wall
– Pre-measure and mark the tube from the mouth to the level of the last rib
– Use a roll of adhesive bandaging material as the mouth gag. I prefer to use Elastoplast as it has an incompressible plastic core, and that the diameter is just large enough to fit our largest diameter stomach tube.
– Unwrap approximately 30 cm of an Elastopast before placing the roll of tape inside the mouth.
– Wrap the tape snugly around the muzzle to prevent the dog from opening its mouth and dislodging the roll
– Lubricate the tube with lubricants to reduce frictional trauma to the oesophagus
– Pass the stomach tube through the core of roll and down into the mouth, you will feel a dead end at the level of the lower oesophageal sphincter where the volvulus has torsed close the oesophagus
– Apply gentle constant pressure and the vast majority of the times the tube will pass through into the stomach. Sometime there is a puff of gas that can be heard and felt from the aboral end of the tube when it enters into the stomach. The tube can also be palpated when the stomach is decompressed.
– The tube is taped to the muzzle to prevent dislodgement and the aboral end placed in a bucket to allow fluid to exit via gravity and siphon
– If it does not pass then reassess to see if trocarisation is required to relieve some pressure in the stomach
As mentioned above, I generally leave the stomach tube in while we continue to stabilise the patient and prepare for surgery. Gas can rapidly accumulate in the stomach and cause rapid deterioration if the tube is not left in. The tube is removed just prior to induction of anaesthesia.
Next week I will discuss surgery tips.
Goodrich ZJ, Powell LL, Hulting KJ. Assessment of two methods of gastric decompression for the initial management of gastric dilatation-volvulus. J Small Anim Pract. 2013;54(2):75–79.