Keywords
thoracoabdominal aortic aneurysm - cool-shot technique - spinal cord protection -
reperfusion injury
Introduction
Spinal cord injury is one of the complications that surgeons must seriously avoid
in patients undergoing thoracic and abdominal aortic aneurysm repair, causing permanent
paralysis at a rate of 2.0 to 10.8%.[1]
[2]
[3]
[4]
We have used cold blood reperfusion as a method of protection against spinal cord
ischemia to prevent spinal cord nerve tissue reperfusion injury. We have found this
technique to be particularly useful when intraoperative motor evoked potential (MEP)
monitoring showed a weak response and spinal cord perfusion failure was strongly suspected.
Herein we present a case series wherein this technique was performed.
Patients and Methods
We performed open aortic surgery with intercostal artery (ICA) reconstruction in 23
patients at our hospital from January 2016 to December 2022. All patients underwent
preoperative multislice computed tomography scan angiography of the Adamkiewicz artery
(AKA).[5]
We inserted a cerebrospinal fluid drainage (CSFD) catheter between the lumbar vertebral
bodies one day preoperatively. Muscle MEPs (using an MEE-2000; Nihon Kohden, Tokyo,
Japan) were recorded intraoperatively. Muscle MEPs were obtained in the abductor pollicis
brevis and abductor hallucis muscles of the feet using subcutaneous needle electrodes.
A 50% decrease in MEP amplitude from the baseline amplitude obtained immediately before
the interventions was considered a significant change; MEP amplitude loss was deemed
an alarm signal for spinal ischemic changes.[6] No neuromuscular blocking agents were administered during MEP monitoring.
We conducted partial cardiopulmonary bypass through cannulation of the left femoral
artery and femoral vein ([Fig. 1A]). We routinely used mild-to-moderate hypothermia (32–34°C, rectal temperature).
Circulating flow during cardiopulmonary bypass was slowly titrated up to 3.5 L/min
and maintained after aortic clamping. Subsequently, we used segmental-staged aortic
clamping to execute cross-clamping, first clamping the proximal side of the left subclavian
artery and middle descending aorta. The abdominal aorta was clamped above the celiac
artery branches. We measured MEPs 5 minutes after aortic clamping. Of these, the ICA
between Th8 and Th12 was selected for reimplantation based on preoperative diagnosis.
We adopted the following strategies:
-
Upper body circulation was maintained at 80 to 100 mmHg at radial artery pressure
with autologous cardiac output, while lower body circulation was maintained at hypothermic
blood flow (1.0–1.5 L/min) with cardiopulmonary bypass circulation.
-
We re-perfused the AKA from a 9-mm branch of an artificial graft with a blood temperature
of 20°C and perfusion pressure of 80 to 100 mmHg. We raised blood temperature to 34°C
within approximately 15 minutes (cool-shot technique) ([Fig. 1A]).
-
Mean blood pressure of 100 mmHg was enforced if MEPs weakened or disappeared during
clamping ([Fig. 1B]).
Fig. 1 Mechanical cardiopulmonary support during surgery for thoracoabdominal aortic aneurysm.
(A) Modification of the cardiopulmonary bypass during surgery for thoracoabdominal aortic
aneurysm. (B) The end-to-side anastomosis is created between the Bentall graft and abdominal Y-shaped
graft. Reperfusion methods after Adamkiewicz artery reconstruction are as follows.
Blood cooled to 20°C is perfused from the artificial vascular side branch before releasing
the proximal aortic clamp following intercostal artery reconstruction. The distal
anastomosis or abdominal organ branches are reconstructed during 15 to 20 minutes
of rewarming, and the proximal clamping is subsequently released. Red, black, yellow,
and blue arrows indicate the proximal aortic clamping, distal aortic clamping, site
of intercostal artery reconstruction, and abdominal vessel branching, respectively.
White and purple arrows indicate the site of blood delivery and direction of cooled
blood delivery to the intercostal artery, respectively.
CSFD was continued for 24 hours postoperatively.
[Table 1] presents patient characteristics. One patient (4.5%) died postoperatively due to
pneumonia caused by multidrug-resistant Pseudomonas aeruginosa.
Table 1
Preoperative baseline characteristics
|
Age (year)
|
59.7 ± 12.6 (28–74)
|
|
Male sex
|
20 (86.9%)
|
|
Heritable thoracic aortic disease: Marfan syndrome
|
3 (13.6%)
|
|
Hypertension
|
20 (90.9%)
|
|
Dyslipidemia
|
12 (54.5%)
|
|
Diabetes mellitus
|
3 (13.6%)
|
|
Estimated glomerular filtration rate (mL/min/1.73 m2)
|
71.9 ± 20.6
|
|
Prior cerebrovascular accident
|
2 (9.1%)
|
|
Left ventricular ejection fraction (%)
|
69.5 ± 4.7
|
|
EuroSCORE II
|
5.4 ± 4.8
|
|
Type of aortic disease
|
|
True aortic aneurysm
|
6 (27.3%)
|
|
Aortic dissection type I
|
8 (45.5%)
|
|
Aortic dissection type IIIb
|
6 (27.3%)
|
|
Type of Crawford classification I
|
4 (18.2%)
|
|
II
|
10 (45.5%)
|
|
III
|
7 (31.8%)
|
|
IV
|
1 (4.5%)
|
|
Adamkiewicz artery branches at
|
|
|
Th 7–9
|
3
|
|
Th 10–12
|
16
|
|
L1–2
|
3
|
|
Reattachment of intercostal arteries
|
22 (100%)
|
|
6th to 12th intercostal arteries
|
3 (13.6%)
|
|
8th to 12th intercostal arteries
|
8 (36.4%)
|
|
9th to 12th intercostal arteries
|
2 (9.1%)
|
|
10th to 12th intercostal arteries (plus first lumbar artery)
|
4 (18.2%)
|
|
11th to 12th intercostal arteries
|
2 (9.1%)
|
|
12th intercostal artery to second lumbar arteries
|
3 (21.1%)
|
|
Operative time (minutes)
|
539 ± 114
|
|
Cardiopulmonary bypass time (minutes)
|
176 ± 58
|
|
Aortic clamp time (minutes)
|
120 ± 44
|
|
minimum rectal temperature
|
35.1 ± 0.6
|
|
Operative death
|
1 (4.5%)
|
|
Cerebrovascular accident
|
4 (18.2%)
|
|
Acute renal failure
|
2 (9.1%)
|
|
Cardiac complication
|
0
|
|
Pulmonary complication
|
3 (13.6%)
|
|
Infection
|
3 (13.6%)
|
|
Bleeding requiring reoperation
|
0
|
|
Spinal cord injury
|
1 (4.5%)
|
|
Persistent paraparesis or paraplegia
|
0
|
|
Transient paraparesis
|
1 (4.5%)
|
|
Length of hospital stay (days)
|
25.8 ± 19.4
|
Abbreviation: EuroSCORE II, European System for Cardiac Operative Risk Evaluation.
During ICA reconstruction, MEP was attenuated or absent in nine patients. However,
MEP improved in all but one case (case 1: [Fig. 2A–D]). Although MEP did not improve in one patient intraoperatively, it improved 1 month
later. This patient underwent coronary artery bypass surgery via the left internal
thoracic artery, aortic arch replacement, and Y-grafting for an abdominal aortic aneurysm
(case 2: [Fig. 3A–D]). Moreover, the patient experienced severe hypotension due to a postoperative blood
transfusion allergy and difficulty maintaining blood pressure. Nevertheless, motor
palsy improved after 1 month, with a slight depth perception abnormality remaining.
We attributed the leading cause of spinal cord failure paralysis to the lack of collateral
blood flow during aortic clamping and failure to maintain blood pressure after reconstruction.
Fig. 2 Case 1: a 72-year-old man presenting with a chronic type IIIb dissecting aortic aneurysm
(Crawford type II). (A) Preoperative findings (Crawford type II). The thoracic descending aorta has a maximum
diameter of 63 mm, while the abdominal aorta shows a diameter of 48 mm. The Adamkiewicz
artery branches off the descending aorta at the 11th–12th thoracic vertebral level
(black arrow). (B) First postoperative three-dimensional (3D) CT. We opt for descending aortic replacement
as our first procedure (light blue line coverage). (C) 3DCT following the final surgery. We perform artificial vascular replacement for
the thoracoabdominal aortic aneurysm in the second surgery (yellow-green line). The
intercostal artery is reconstructed as an island between the 8th and 12th thoracic
vertebrae. The black arrows indicate the reconstructed Adamkiewicz artery. (D) Alteration in motor response evoked potential (MEP): MEP in the right leg is lost
during reconstruction of the intercostal artery (red arrow), but recovered after revascularization
(blue arrow). CT, computed tomography.
Fig. 3 Case 2: a 73-year-old man with Behçet's disease and multiple aortic saccular aneurysms.
(A) Preoperative findings. The coronary arteries show 90% stenosis in the left anterior
descending branch and an aneurysm in the left subclavian artery. The Adamkiewicz artery
is branched from the 10th to 11th intercostal artery (black arrow). The patient also
undergoes artificial vascular replacement (Y-graft) for an abdominal aortic aneurysm.
(B) First postoperative three-dimensional CT. We initially perform total arch aortic
replacement and coronary artery bypass (left internal thoracic artery–left anterior
descending branch: light blue arrow). (C) 3DCT following the final surgery. Artificial vessel replacement is performed for
the thoracoabdominal aortic aneurysm in the second surgery (yellow-green line). The
intercostal artery is reconstructed as an island between the 9th and 12th thoracic
vertebrae. Black arrows indicate the reconstructed Adamkiewicz artery. (D) Alterations in motor response evoked potentials (MEPs): MEPs in the left leg disappear
during intercostal artery reconstruction (red arrow) and, unfortunately, they do not
recover after revascularization (blue arrows).
Although we used the CSFD during surgery, we were unable to prove its efficacy in
this study because we were not able to use it in all patients based on the established
criteria; it was only used according to the protocol after surgery.
Discussion
Excellent results were achieved with this technique; there were no instances of post-discharge
paraplegia, despite momentary MEP loss in some patients. Although hypothermia is helpful
for spinal cord protection, whole-body hypothermia during thoracoabdominal aortic
aneurysm surgery is invasive. Hence, we employed the cool-shot technique for local
cooling of the spinal nerves.
The degree of hypothermia employed may be mild (30–34°C) or severe (15–20°C) depending
on the institution. Deep hypothermic circulatory arrest (DHCA) is typically reserved
for complex thoracic aortic procedures. In large centers where DHCA is routinely performed,
patient outcomes are comparable to those of endovascular repair.[7]
[8]
[9] However, adapting DHCA in older patients is challenging and may increase blood loss.
Therefore, we devised a method in which surgery is performed under mild hypothermia,
with only the spinal cord under deep hypothermia.
Although epidural cooling to prevent reperfusion injury is effective, it is invasive
and complex.[10] Hence, we investigated a strategy commencing with local cooling perfusion after
ICA reconstruction and gradually raising spinal cord blood delivery temperature.
This study has certain limitations. First, the sample size was small. Second, only
results in cases of reconstructed ICAs were reported; the extent of spinal cord cooling
using the cool-shot technique after reconstruction remains unknown.
Conclusion
We devised a regional spinal-cord cooling technique using the spinal cool-shot technique
following ICA reconstruction that is effective in additional spinal-cord protection.
This technique may prevent reperfusion injury, and early and delayed postoperative
paralysis in patients with intraoperative MEP loss during thoracoabdominal aortic
aneurysm surgery.
