ACMT Toxicology Visual Pearl: The Bark with Some Bite
Which medication can be derived from the bark of the pictured tree?
- Aspirin
- Atropine
- Colchicine
- Quinine
Which medication can be derived from the bark of the pictured tree?
A heavy alcohol drinker, who is well known to your Emergency Department, presents with altered mental status, except that he looks different this time. He looks really bad, stating that he has been vomiting blood. He is hypotensive. He then vomits a copious amount of blood right in front of you. You intubate the patient and initiate the massive transfusion protocol, but everything you pour into him seemingly comes right back out. The gastroenterologist on-call states that he is too unstable for endoscopy. It is time for a balloon tamponade device. You’ve trained for this and set up everything. You call the respiratory therapists (RT) for this mystical “manometer” that you have seen in instructional videos, except that they look puzzled by your request. It is time to MacGyver a method that allows you to know the esophageal balloon pressure that you are generating to avoid an esophageal rupture.
There are 2 commonly used devices for tamponading the esophagus during a variceal bleed, the Sengstaken-Blakemore (SB) tube and the Minnesota tube. There is also the Linton-Nachlas tube, but that only has a gastric balloon. The SB tube was created in 1950 in order to help tamponade variceal bleeds [1]. It is a 3-lumen device that has ports to inflate the gastric balloon, aspirate gastric contents, and inflate an esophageal balloon. The Minnesota tube was developed later as a variation to the SB tube and contains an additional port and lumen for aspirating esophageal contents [2]. Another minor difference is that the gastric balloon in the Minnesota tube holds 450-500 ccs of air, while the SB gastric balloon holds 250 ccs of air [2].
Indication: The uncontrolled hemorrhage from esophageal or gastric variceal bleeding after medical or endoscopic treatment fails, is not available, or is not technically possible [3, 4].
Contraindications [4]:
Esophageal balloon tamponade devices achieve hemostasis in 60-90% of cases; however, they are only a temporary measure of hemorrhage control because over 50% of variceal bleeds rebleed after deflation [5].
The following instructions are for inserting a Sengstaken-Blakemore (SB) tube [3, 6]:
The manometer referenced in numerous videos [6, 8] is actually a cuff manometer, or pressure gauge, to measure endotracheal cuff pressures. Hence, the RT’s are supposed to have them. In our emergency department, the RTs do not spend a lot of time going around measuring cuff pressures and usually save that until the patient reaches the ICU. It is convenient to use for the inflation of the esophageal balloon because it can inflate and measure pressure at the same time.
Pearl 1: Check the units of pressure being used. Manometers often use cmH2O, while esophageal balloons use mmHg.
Pearl 2: While the gastric balloon sets a target VOLUME, the esophageal balloon sets a target PRESSURE.
Once the inflated gastric balloon is confirmed to be in place, it is time to inflate the esophageal balloon. A manual blood pressure instrument can be repurposed to inflate and measure the esophageal balloon pressure.
Ever finally step away from a busy resuscitation and someone stops you for peripheral IV access? You set up everything, have the patient positioned, and then notice there is no sterile ultrasound gel. No gel? No problem. The trick is to eliminate anything of poor acoustic impedance between the ultrasound probe and the patient’s skin.
Instead of using gel, we squeeze alcohol pads to create a thin alcohol layer and place a transparent adhesive cover, such as Tegaderm ©. The thin alcohol layer serves to eliminate any air bubbles under the adhesive cover as well as minimizes residual adhesive material sticking to the probe when removing the cover. The adhesive cover itself serves as a sterile barrier and a slick surface to improve probe maneuverability. Note that some ultrasound manufacturers do not recommend the use of isopropyl alcohol on their transducers. Therefore check your specific ultrasound’s recommendations before trying [1, 2].
Squirt normal saline flush on the patient’s skin to create a coupling medium between the probe and the patient.
Why it works:
Ultrasound procedures use a range of frequencies (1.5-20 MHz) to visualize internal structures and require a medium to replace air, which has a poor acoustic impedance for the ultrasound waves [3]. Acoustic impedance is defined as the resistance of the propagation of ultrasound waves through tissues and is the product of the density and speed of sound in the tissue [4]. Ultrasound gel has an acoustic impedance that is similar to soft tissue and is therefore considered the ideal medium [3]. Because most soft tissue is comprised of water, the acoustic impedance of water, and therefore 0.9% saline, is actually pretty similar [5], as demonstrated by water bath techniques for ultrasounding distal extremity injuries [6].
We find great visual clarity for performing ultrasound-guided peripheral IVs using this trick, as shown in Figure 1.
Read other Tricks of the Trade articles.