This device features in Question 30 from the first paper of 2013, as well as in Question 18.3 from the first paper of 2008 and Question 30 from the second paper of 2015.
To the left one may see the grainy black and white photograph of the very first rubber gastro-oesophageal tamponade tube which was discussed in Sengstaken and Blakemore's original paper from 1950. Well, that is not completely correct- Karl Friedrich Otto Westphal had used a gastric tamponade balloon in 1930, but for some reason the name "SB tube" became a household name instead of "Westphal's Kompressionsbehandlungsonde". In any case, the major criticism of this device was its tendency to cause life threatening aspiration or airway obstruction.Subsequent modifications of the technique made attempts to protect the patient from the risk of airway-obstructing tube dislodgement and oesophageal content aspiration.
The picture of the person in the football helmet is a (shamelessly stolen) diagram from Bauer Kreel and Kark (1974), depicting the position of an SB tube in an awake extubated patient. After tension is applied, the tube is affixed to the face guard of a football helmet instead of hanging from the end of the bed (this was easier to manage from a nursing viewpoint). Because this product was not supplied with an oesophageal aspiration port, the patient has a nasogastric tube suspended in mid-oesophagus. This port was under intermittent suction and free drainage, to act as a vent for swallowed secretions. The authors also recommended that this port be "gently irrigated", which sounds like a recipe for disaster in a patient with an unprotected airway.
Interestingly, the college always seem say that to describe their obviously three-lumen tube as a Minnesota tube is "acceptable". But... in fact the two are quite distinct, and if one were to dig in even the dustiest corners of the most backward endoscopy suite, one would not find even one classical SB tube. This is because the Minnesota tube is actually a modified version of the original Sengstaken-Blakemore device. The modification is an oesophageal suction port, which prevents the pooling of filth in the upper oesophagus.
You can tell them apart instantly - the Minnesota tube has four ports at the end, whereas the SB tube has only three. One can also have a Linton-Nachlas tube, which only has two ports, and a single 600ml gastric balloon. The distinction between tubes is important; the Minnesota tube's modification aims to defeat the risk of aspiration, which is a major limitation to the use of such tubes in non-intubated patients.Thus, the device in my picture is properly called a Sengstaken-Blakemore tube, and to call it a Minnesota tube would just be plain wrong. Overall, the general trend in the development of these devices has been characterised by the uncontrolled proliferation of aspiration ports, manometry lines, suction orifices, pressure-indicator balloons and other such inflatable decorations. One may follow this pattern of behaviour as it extends into the absurd.
Which eponymous tube is which?
- The SB tube has three ports- NG suction, oesophageal balloon and gastric balloon.
- The Minnesota tube has four ports at the end (one extra port for aspirating stuff from above the oesophageal balloon)
- The Linton-Nachlas tube has only has only two ports, and a single 500-600ml gastric balloon.
Anatomy of the Sengstaken-Blakemore tube
This offers a vrief "portology" of the device. Obviously, when one is shoving it in, one is in some hurry (the placement of any rescue therapy device is rarely a carefully controlled and deliberate elective procedure). One should have some minimum of knowledge beforehand.
In case one is interested, the total length of the tube is usually 85cm, and it comes in a series of sizes ranging from 14Fr to 21Fr. A manufacturer brochure which answers all your questions about their specific product is available, and I plagiarise from it liberally. The unfair focus on this product is due to the fact that the local facility has recently purchased a whole bunch of them, and should not be viewed as an endorsement of this specific product (as such equipment is usually purchased according to the lowest contract bid).
The procedure of inserting a gastro-oesophageal tamponade balloon
The college asked for this in Question 30 from the second paper of 2015. They gave us a suggested technique in their "model answer" which I have modified with some of the suggestions made at the LITFL page for this procedure, and the Nepean ICU protocol for handling this device.
- Protect the airway.
Ideally, the patient should be intubated.
This prevents you from inserting the tube into the trachea accidentally, and prevents aspiration of pooling oesophageal blood or displaced gastric content.
- Inspect the tube and check the balloons for leaks.
LITFL also recommend to calculate the compliance of the balloon "by inflating the balloon with incremental 100ml aliquots of air to maximal recommended volume (usually 250 -300ml for SBT, 450-500ml for Minnesota) and note the corresponding balloon pressure at each step". This is highly appealing to any person who enjoys graphs.
- Lubricate the tube.
- Position the patient sitting up to 45°
This protects them from aspiration
- Insert the tube into the mouth or nose.
The college answer offers the nares as an option, but realistically everybody always uses the orogastric route because these patients are always coagulopathic and thrombocytopenic from their chronic liver disease. Moreover, the tube is huge and thick, with big balloons- they will shred the nasal mucosa on the way in regardless of how much lube you cake them in. The insertion should ideally be performed under direct laryngoscopy so that you can be sure you are in the oesophagus.
- The tube should be advanced to 50cm.
The college answer prescribes a depth of 50cm, which is consistent with the classical technique for insertion (Bauer et al, 1974). The alternative is to measure from mouth to angle of the jaw, then suprasternal notch and xiphisternum. LITFL authors recommend the latter method, acknowledging that humans vary in the length of their oesophagus.
- Inflate the gastric balloon. Check position with a chest Xray.
There seems to be some disagreement as to how much one might inflate. The college recommend 250ml; LITFL mention that the Minnesota tube should take 450-500ml. Locally, we are more cautions: we inflate with about 100ml and then check position with an AXR. If one has produced a compliance curve for their balloon, one may check the balloon pressure against their curve to see whether it has been inflated in the oesophagus (LITFL offer a 15mmHg increase in pressure as a rough guide: if the post-insertion pressure for a given volume is more than 15mmHg higher than the pre-insertion pressure, then the balloon needs to be repositioned as it is likely in the oesophagus. )
- Withdraw the tube until resistance is felt (at 30-35cm)
This is usually the depth to the gastro-oesophageal junction. Tension develops, which gives one the impression that the balloon is up against an obstacle of some sort. If one has not inflated with enough air there will be no resistance, and the balloon will come out of the mouth to the embarrassment of the operator.
- Aspirate the gastric and oesophageal ports.
If there was vigorous bleeding, it should have stopped by balloon tension.
- Decide whether or not to inflate the oesophageal balloon.
If you already know where the varices are on the basis of a gastroscopy result, you may use your judgment (i.e. there is no point of inflating the oesophageal balloon for gastric varices). Otherwise, one is guided by blood loss. If bleeding from oesophageal and gastric ports has ceased, then you may leave oesophageal balloon deflated. Bauer et al (1974) recommend to irrigate the suction ports with warm saline, to assure oneself that the aspirate returns clear and that there is no new bleeding.
- If appropriate, inflate the oesophageal balloon to 25-30 mmHg pressure.
The maximum oesophageal pressure is 40mmHg. If the bleeding in the oesophagus has stopped, one should deflate the oesophageal balloon by 10mmHg every 2 hours.
- Apply traction to the tubing
The precise amount of traction is uncertain. Some centres specify 1kg, others 2kg. The college answer calls for a 500ml bag of fluid, suspended over a pulley.
Weaning of gastro-oesophageal tamponade
How do you remove thins thing? Abruptly? Perhaps. No specific literature exists to guide practice here. Generally speaking, one should only consider it if the bleeding has stopped. Locally, we manage this in steps:
- Deflate the oesophageal balloon. Watch for bleeding for a few hours (4-6).
- Remove the tension (and keep the balloon inflated). Watch for bleeding.
- Deflate the gastric balloon (keeping the tube in situ). Again, watch for bleeding. Ensure gastric aspirates (or lavage samples) remain unbloodied.
- Remove the tube and ignore the haemoglobin (just kidding: watch for bleeding).
Confirming the position of the gastric balloon
The balloon labelled "A" is the gastric ballon. It inflates to a considerable diameter, and so it is fairly important that you do not inflate it in the oesophagus. Hence the anxiety regarding its position.
One can do this in a number of ways.
- One can inflate it with a safe 80-100mls of air, and look for its position on AXR.
- One can inflate it with radio-opaque contrast, and look for its position on AXR
- One can position it under direct vision during gastroscopy
- One can compare the balloon pressure pre and post insertion (as suggested by the college), observing a change of 15mmHg as a sign that it is in the oesophagus.
- Some go so far as to actually plot a compliance curve for the balloon, inflating it with progressively larger volumes of air and observing the change in pressure. The argument for doing this is that the stomach has much greater compliance than the oesophagus, and the compliance curve of the stomach will be much more linear, whereas in the oseophagus the increase in pressure per unit volume will be rapid and steep.
Indications for the use of the SB tube
Classically, this thing has been used for the tamponade of bleeding from a gastric or oesophageal source. It was particularly popular before the advent of easily available endoscopy; Sengstaken and Blakemore published their seminal paper in 1950 (though similar devices had been described even earlier).These days wherever varices are managed with banding and sclerotherapy this device has become less popular. Thus, the indications are:
- Tamponade of acute gastric or oesophageal variceal haemorrhage in patients for which which neither band ligation nor sclerotherapy is technically possible, readily available, or has failed.
In addition to this classical indication, the SB tube appears to have a million uses, not limited to tamponade of bleeding in hollow spaces. For example:
However, these are not what you might call "exam answers". Please don't mention them in the written paper.
Contraindications for the use of the SB tube
- Unprotected airway
- Oesophageal rupture (eg. Boerhaave syndrome)
- Oesophageal stricture
- Uncertainty regarding the source of bleeding (how do you know it is not duodenal?)
- Well-controlled variceal bleeding