The animal protocol begins with animal preparation and instrumentation. This is followed by the experimental portion of the protocol, see Figure 1. Here we commence hemorrhage, which is followed by a period of hemorrhagic shock, followed by full REBOA, then partial REBOA, then wean REBOA and continue resuscitation.
I. Animal Preparation and Instrumentation:
1. anesthetize the animal with telazol (5mg/kg) and xylazine (2mg/kg) at appropriate doses.
2. transport the animal to the procedure area.
3. place the animal under isoflurane targeting 1.0 MAC by facemask. Transition to generally 10 ccs/kg TV, RR of 12-14 initially but to target a pCO2 of 30-45 and an FiO2 of 40% but adjusted appropriately as needed.
4. place the animal in sternal recumbency and intubate the animal with a 7.0 endotracheal tube.
5. make the animal supine and restrain.
6. Place all venous and arterial catheters using US guidance, and place all monitoring devices.
-place an LV PV loop via a carotid or right brachial artery 7 fr sheath catheter.
-place a 7 fr sheath in either jugular down to the RA to be able to obtain central venous gases (and labs).
- place a 7 fr sheath in the other carotid or either brachial artery, and through this placean aortic pressure probe (which will remain proximal to the REBOA)
-place a 7 fr sheath in the right or left jugular for central venous pressure probe
-place an at least 7 fr sheath in either femoral vein through which we will hemorrhage and later resuscitate.
-place a 7 fr sheath in either femoral artery, though which place an aortic pressure probe (which will remain below the REBOA)
-place an at least 8 fr (ideally 9 fr sheath) in either femoral artery to hold the REBOA catheter from below
-also place EKG leads, oxygen saturation probe, rectal temperature probe and a bovie pad (after shaving).
7. Perform a lower abdominal laparotomy for cystostomy (place a foley catheter into the bladder) to facilitate bladder drainage.
8. Perform a left anterolateral thoracotomy. Place the 3 or 4mm flow probe around the coronary flow probe and add ultrasound jelly to the probe.
10. Perform a TIMEOUT. Confirm all line placements, confirm all sheaths work (drawback and flush), confirm fluids are ready, that the timer is ready and reset, that data is being transduced through LabChart through appropriately labeled channels and saved. Confirm ventilatory settings.
11. Confirm fluoroscopically that all catheters and devices are appropriately positioned.
II. Begin Baseline normalization period: (30 min)
1. At the start, give 1L of 0.9% NS and one 50ccs of D50.
2. Obtain VBG, ABG, Trop, Chem8, and 5 tubes of serum.
3. Throughout baseline and resuscitation use the following guidelines:
- Give one ampule of Calcium at start of resuscitation
- Treat glucose < 65 with D50
- for pH < 7.2 give on ampule of bicarbonate
- treat pCO2 as necessary with MV changes
- during resuscitation, treat sustained MAP < 65 after starting fluids with pressor, first line is norepinephrine.
- get baseline blood resistivity, enter value into the PV catheter system control.
1. Bleed at a rate of 50ccs/min from venous CVC to goal of 45 mmHg systolic BP.
IV. Shock: (15 min once bleed is complete) – maintain SPB 45-50 and bleed more if needed.
1. At end of shock obtain a VBG, and ABG if pO2 before was low or needed clinically
2. Obtain repeat blood resistivity and if needed then enter new value into PV catheter system.
V. REBOA Period: has two subperiods: Full REBOA and Partial REBOA periods, ending with REBOA wean and .
Va: Full REBOA (15 min)
- Ends with VBG, ABG
Vb: Partial REBOA (15min) and start resuscitation
1. Aim for 50% SPB differential between the above REBOA and below REBOA aortic pressure transducers; once there, allow to stablize for 15 minutes.
2. Begin fluid resuscitation. Start with return of all shed blood and one ampule of Calcium, then, as needed, in the remaining portion of the protocol we can give up to 3L of 0.9%NS total.
Vc: Full Deflation, transition to post REBOA ICU period.
VI: ICU Period: 30 mins
1. Obtain a VBG and ABG at the start of this period.
2. Confirm ventilatory stability.
3. Ends with chem8, VBB, ABG, and troponin. Obtain full thickness heart tissue and place in formalin. Obtain 5 tubes of blood, spin down and pipet off serum.
VII. Completion of trial.
1. Euthanize and dispose of animal.
2. Clean equipment.