Circulatory arrest under moderate systemic hypothermia and cold retrograde cerebral perfusion

Safety of retrograde cerebral perfusion under moderate hypothermia for hemiarch replacement

OBJECTIVES

Aortic surgeries performed under moderate hypothermia require antegrade cerebral perfusion. The influence of retrograde cerebral perfusion under moderate hypothermic circulatory arrest remains unknown. To clarify this effect, this study aimed to compare the early outcomes of retrograde versus antegrade cerebral perfusion under moderate hypothermia for hemiarch replacement.

METHODS

Between March 2009 and April 2020, 391 hemiarch replacements under moderate hypothermic circulatory arrest via median sternotomy were performed at our institution. Of these, 70 involved retrograde perfusion and 162 involved antegrade perfusion. Propensity score matching was used to compare 61 pairs of retrograde and antegrade cases.

RESULTS

Retrograde and antegrade strategy under moderate hypothermia resulted in comparable operative mortality (3.3% vs. 1.6%, P > 0.99), permanent neurological deficits (8.5% vs. 6.6%, P > 0.99), and temporary neurological deficits (24.6% vs. 39.3%, P = 0.33). Retrograde surgery was associated with shorter circulatory arrest times (31.4 ± 8.2 min vs. 37.4 ± 12.2 min, P = 0.005) and fewer red blood cell transfusions (4.6 ± 3.9 units vs. 8.2 ± 5.1 units, P < 0.001) than those with antegrade surgery.

CONCLUSIONS

Retrograde cerebral perfusion under moderate hypothermia for hemiarch replacement yields excellent operative outcomes, equivalent to those achieved using an antegrade strategy.

Successful use of mild therapeutic hypothermia as compassionate treatment for severe refractory hypoxemia in COVID-19

BACKGROUND

COVID-19 is a disease associated with an intense systemic inflammation that could induce severe acute respiratory distress syndrome (ARDS), with life-threatening hypoxia and hypercapnia. We present a case where mild therapeutic hypothermia was associated with improved gas exchange, facing other therapies' unavailability due to the pandemic.

CASE REPORT

A healthy 38-year-old male admitted for COVID-19 pneumonia developed extreme hypoxia (PaO₂/FiO₂ ratio 42 mmHg), respiratory acidosis, and hyperthermia, refractory to usual treatment (mechanical ventilation, neuromuscular blockade, and prone position), and advanced therapies were not available. Mild therapeutic hypothermia management (target 33-34 °C) was maintained for five days, with progressive gas exchange improvement, which allowed his recovery over the following weeks. He was discharged home after 68 days without significant ICU associated morbidity.

CONCLUSIONS

Mild hypothermia is a widely available therapy, that given some specific characteristics of COVID-19, may be explored as adjunctive therapy for life-threatening ARDS, especially during a shortage of other rescue therapies.

Mild hypothermia increases pulmonary anti-inflammatory response during protective mechanical ventilation in a piglet model of acute lung injury

BACKGROUND

The effects of mild hypothermia (HT) on acute lung injury (ALI) are unknown in species with metabolic rate similar to that of humans, receiving protective mechanical ventilation (MV). We hypothesized that mild hypothermia would attenuate pulmonary and systemic inflammatory responses in piglets with ALI managed with a protective MV.

METHODS

Acute lung injury (ALI) was induced with surfactant deactivation in 38 piglets. The animals were then ventilated with low tidal volume, moderate positive end-expiratory pressure (PEEP), and permissive hypercapnia throughout the experiment. Subjects were randomized to HT (33.5°C) or normothermia (37°C) groups over 4 h. Plasma and tissue cytokines, tissue apoptosis, lung mechanics, pulmonary vascular permeability, hemodynamic, and coagulation were evaluated.

RESULTS

Lung interleukin-10 concentrations were higher in subjects that underwent HT after ALI induction than in those that maintained normothermia. No difference was found in other systemic and tissue cytokines. HT did not induce lung or kidney tissue apoptosis or influence lung mechanics or markers of pulmonary vascular permeability. Heart rate, cardiac output, oxygen uptake, and delivery were significantly lower in subjects that underwent HT, but no difference in arterial lactate, central venous oxygen saturation, and coagulation test was observed.

CONCLUSIONS

Mild hypothermia induced a local anti-inflammatory response in the lungs, without affecting lung function or coagulation, in this piglet model of ALI. The HT group had lower cardiac output without signs of global dysoxia, suggesting an adaptation to the decrease in oxygen uptake and delivery. Studies are needed to determine the therapeutic role of HT in ALI.

Central Nervous System Protection in Cardiac Surgery

Neurological dysfunction and stroke following cardiac surgery and thoracic surgery requiring hypothermic circulatory arrest is a well-defined problem. The original studies in CABG patients identified risk factors, such as prior stroke and lower educational level. There is older evidence suggesting that higher perfusion pressures during cardiopulmonary bypass are helpful. Hyperthermia during rewarming on cardiopulmonary bypass and postoperative hyperthermia have been associated with adverse cognitive outcomes. Glucose management intraoperatively remains controversial, but most now advocate for moderate glucose control using insulin, if required. The subset of patients having thoracic aortic surgery requiring periods of aortic discontinuity are particularly problematic. A cerebral protection strategy should be determined, and this may include hypothermic circulatory arrest, selective cerebral perfusion, or retrograde cerebral perfusion. All of these techniques have been associated with good surgical outcomes, but there is little information on cognitive outcomes of thoracic aortic surgery.

Induced hypothermia as a new approach to lung rest for the acutely injured lung*

OBJECTIVE

To investigate whether low-frequency ventilation during hypothermia could attenuate lung injury associated with endotoxin and mechanical ventilation.

DESIGN

: Experimental animal study.

SETTING

University-affiliated animal laboratory.

SUBJECTS

Forty-eight Sprague-Dawley rats.

INTERVENTIONS

: Lipopolysaccharide was administered to rats intratracheally to induce acute lung injury. After 1 hr of this treatment, animals were assigned to normothermia-only (NO, rectal temperature 37 degrees C, ventilatory frequency 90/min), normothermia-lung rest (NR, 37 degrees C, 45/min), hypothermia-only (HO, 27 degrees C, 90/min), or hypothermia-lung rest (HR, 27 degrees C, 45/min). After 1 hr of injurious ventilation, the lungs of the rats were removed for bronchoalveolar lavage and histologic examination.

MEASUREMENTS AND MAIN RESULTS

Compared with the normothermia groups (NO, NR), the neutrophil counts (per milliliter) (NO, 7708 +/- 5704; NR, 10,479 +/- 11,152; HO, 1638 +/- 955; HR, 805 +/- 591) and interleukin-1beta levels (pg/mL) (1180 +/- 439, 1081 +/- 652, 620 +/- 426, 420 +/- 182, respectively) in the bronchoalveolar lavage fluid, the wet-to-dry lung weight ratios (6.0 +/- 0.4, 5.7 +/- 0.4, 5.6 +/- 0.2, 5.2 +/- 0.2, respectively), and histologic acute lung injury scores (8.3 +/- 2.7, 10.4 +/- 3.1, 3.5 +/- 2.1, 3.1 +/- 2.2, respectively) of the hypothermia groups (HO, HR) were lower (all p < .001). Compared with the HO group, the neutrophil counts and protein content (HO, 1367 +/- 490 mug/mL vs. HR, 831 +/- 369 mug/mL) in the bronchoalveolar lavage fluid, the serum lactate dehydrogenase levels (units/mL) (9.1 +/- 3.6 vs. 5.3 +/- 1.5), and the wet-to-dry lung weight ratios of the HR group were lower (all p < .05).

CONCLUSIONS

Reduction of ventilatory frequency in conjunction with hypothermia attenuated many variables of acute lung injury in rats. Use of hypothermia could be exploited as a new approach to lung rest for the ventilatory management of the acutely injured lung.

Stroke in thoracic aortic surgery: outcome and risk factors

The risk factors and the outcome of stroke in thoracic aortic surgery were studied in 127 patients (86 males, 41 females), aged 18 to 84 years (mean, 64 years), operated on between September 1994 and December 2000. There were 29 operations on the ascending aorta, 63 arch, 29 descending, 5 thoracoabdominal, and 1 extraanatomical bypass. Perioperative stroke occurred in 15 patients (12%). The risk factors for stroke were identified as preexisting chronic renal failure and femoral arterial cannulation. Hospital death occurred in 4 of the 15 cases (27%) of stroke and 7 of the 112 cases (6%) without stroke (p < 0.05). There were 18 late deaths during a mean follow-up period of 3.2 years (range, 1 month to 7.2 years). The 3-year survival rates were 43 +/- 14% in the stroke patients and 85 +/- 4% in the other patients. Actuarial survival, including during hospitalization, was lower in the stroke patients than in the other patients not only among those 70 years or older but also among all the patients (both p < 0.0001). Stroke occurring in thoracic aortic surgery is thus an important risk factor for early and late mortality, particularly in patients 70 years or older.

Influence of retrograde cerebral perfusion during aortic arch procedures

BACKGROUND

Recent reports suggest dramatic improvement in outcome using retrograde cerebral perfusion (RCP) during operations on the arch; however, most investigators have compared contemporary results with historic controls. The purpose of this study was to determine the impact of RCP within the same patient population and time period.

METHODS

From 1996 to 2000, 72 consecutive patients underwent an aortic arch procedure using hypothermic circulatory arrest (HCA) (31 acute dissection or rupture, 41 chronic dissection or aneurysm). Supplemental RCP was used in 36 patients, whereas 36 patients had HCA alone. The groups were similar in age, emergent status, and cardiopulmonary bypass time (p > 0.08), but HCA time was higher with RCP (40 +/- 15 minutes versus 29 +/- 14 minutes; p < 0.001).

RESULTS

Operative mortality was 10% +/- 4% (+/- 70% confidence limit), and adverse outcomes (death or cerebrovascular accident) occurred in 14% +/- 4%, but there was no difference between HCA alone (8% +/- 5%, 14% +/- 6%) and HCA with RCP (11% +/- 5%, 14% +/- 6%) (p > 0.73). The incidence of transient neurologic dysfunction was also similar (HCA alone, 11% +/- 5%; HCA with RCP, 17% +/- 6%; p > 0.73). Multivariate risk factors for mortality included emergency operation and HCA time (p < 0.02). Risk factors for adverse outcome included emergency operation and atheromatous ascending aorta (p < 0.03). Risk factors for transient neurologic dysfunction included preexisting cerebrovascular disease and rewarming retrograde (femoral) rather than antegrade (through the graft) (p < 0.03).

CONCLUSIONS

Supplemental RCP during HCA did not decrease mortality or neurologic complications. Retrograde rewarming through the femoral artery after completion of the distal anastomosis increased transient neurologic dysfunction. Therefore, RCP remains optional, but reperfusion should be antegrade to improve neurologic recovery.

Reoperations on the aortic valve combined with replacement of the ascending aorta

OBJECTIVE

To review the experience with reoperations on the aortic valve combined with replacement of the ascending aorta.

PATIENTS AND METHODS

From 1991 to 2000, 237 patients underwent reoperations on the aortic valve combined with replacement of the ascending aorta. The study consisted of 188 men and 49 women, with a mean age of 51 years. The operation was urgent or emergent in 44% of cases. Many patients (42%) were in New York Heart Association Class IV, and 24 had active infective endocarditis. The ascending aorta was replaced previously in 46 patients, while the remaining patients had aneurismal dilation. An aortic valve sparing operation was performed in 14 patients and aortic valve replacement in 223. The ascending aorta was replaced in all patients as follows: as a composite graft in 166 and supracoronary in 71. Mechanical valves were used in 145 (61%) patients.

RESULTS

The operative mortality was 9%. Postoperative complications were common and 30% of patients suffered an adverse event (death or complication). No independent predictor of operative mortality could be identified but urgent/emergent surgery, advanced functional class, infective endocarditis, coronary artery disease, and replacement of the transverse aortic arch were associated with higher operative mortality by chi-square analysis. The survival at 5 years was 74%+/-4% for patients who had composite replacement of the aortic valve and ascending aorta.

CONCLUSIONS

Reoperations on the aortic valve combined with replacement of the ascending aorta can be performed with acceptable operative risk and good mid-term survival.

Cerebral Protection During Surgery of the Aortic Arch

The most significant challenge in surgical repair of the aortic arch (transverse thoracic aorta) is to protect the brain from ischemic injury. During the portion of the procedure when the brachiocephalic vessels are at tached to a graft, there is an obligatory interruption in the normal path of circulation to the brain. Various strategies are used to overcome the potential for brain injury during discontinuity between the aorta and the cerebral circulation. These include deep hypothermic circulatory arrest, retrograde cerebral perfusion, and selective anterograde cerebral perfusion. Pharmaco logic adjuncts to these procedures are also used to further enhance brain protection. This review ad dresses the relative merits of these techniques as means of cerebral protection.

Retrograde cerebral perfusion as a method of neuroprotection during thoracic aortic surgery

Retrograde cerebral perfusion is commonly used as an adjunct to hypothermic circulatory arrest to enhance cerebral protection during thoracic aortic surgery. This review summarizes a large number of studies that demonstrate a spectrum of beneficial, neutral, and detrimental effects of retrograde cerebral perfusion in humans and experimental animal models. It remains unclear whether retrograde cerebral perfusion provides effective cerebral perfusion, metabolic support, washout of embolic material, and improved neurological and neuropsychological outcome.

A huge frontal meningioma associated with intraoperative massive bleeding and severe brain swelling--case report

A 58 year old female presented with progressive memory disturbance and personality change. Magnetic resonance (MR) imaging disclosed a huge mass lesion accompanied by prominent oedema in the right frontal lobe. Cerebral angiogram demonstrated a vascular-rich tumour and a major drainer through diploic vein. A right frontotemporal craniotomy was performed. We encountered massive bleeding from diploic vein and dura mater immediately at the craniotomy. We were also faced with severe brain swelling at the dural incision. The tumour was solid, highly vascularised, and fairly well demarcated. We performed total removal of the tumour as quickly as possible in order to reduce the intracranial hypertension and avoid the impending brain herniation. The patient had an uneventful recovery and was asymptomatic at 10 months follow-up.

Redo aortic root replacement: experience with 31 patients

BACKGROUND

Aortic root re-replacement is being performed with increased frequency. Limited information is available regarding the surgical approaches and clinical outcomes of this reoperation.

METHODS

Between May 1980 and May 1999, 31 patients (mean age, 45 +/- 15 years) underwent redo composite replacement of the aortic valve and ascending aorta. Indications for reoperation were prosthetic valve endocarditis in 12 patients (39%), failed biological valve in 17 (55%), and false aneurysm in 2 (6%). At reoperation, mechanical valves were implanted in 24 patients and biologic valves in 7. All patients with endocarditis had annular abscess and required reconstruction of the left ventricular outflow tract before implantation of a new valved conduit. Mechanical valves were used in 24 patients, aortic homograft in 4, and bioprosthetic valves in 3. The coronary button technique was used to reimplant the coronary arteries whenever possible. Extension of one or both coronary arteries with a short segment of saphenous vein or a synthetic graft was used in 16 patients (52%). The aortic arch was replaced in 7 patients (23%).

RESULTS

There was one operative death (3%) because of rupture of an abdominal aortic aneurysm. The mean follow-up was 47 +/- 46 months and was 100% complete. There were five late deaths (16%), three of which were cardiac related. The actuarial survival was 71% +/- 12% at 5 years. Three patients experienced recurrent prosthetic valve endocarditis 4 months to 8 years after operation. The 8-year freedom from endocarditis for patients operated on for endocarditis was 82% +/- 11% compared with 100% for those operated on for other reasons (p = 0.1). At the last follow-up, 21 of 25 survivors (84%) were in New York Heart Association functional classes I or II, and 4 were in class III.

CONCLUSIONS

Redo aortic root replacement can be performed with good early and late results. Patients operated on for prosthetic root endocarditis may have an increased risk of recurrent late endocarditis.

Predictors of adverse outcome and transient neurological dysfunction after ascending aorta/hemiarch replacement

BACKGROUND

This study was undertaken to determine predictors of adverse outcome and transient neurological dysfunction after replacement of the ascending aorta with an open distal anastomosis.

METHODS

All 443 patients (300 male, median age 63) undergoing replacement of the ascending aorta with an open distal anastomosis between 1986 and 1998 were included in the analysis. The ascending aorta alone was replaced in 190 (42.9%); 253 (57.1%) also had proximal arch replacement. Median hypothermic circulatory arrest (HCA) time was 25 minutes (range 12 to 68). Either death or permanent neurological dysfunction were considered adverse outcome (AO).

RESULTS

Adverse outcome occurred in 11.5% (51 of 443) of patients overall: in 7.4% of elective (20 of 269) or urgent (4 of 54) operations, but in 17% (19 of 113) of emergencies. Multivariate analysis of the group as a whole revealed that significant (p < 0.05) independent preoperative predictors of AO were age greater than 60 [odds ratio (OR) 2.2], hemodynamic instability (OR 2.7), and dissection (OR 1.9). For the 435 operative survivors, procedural variables predictive of AO were contained rupture (OR 2.8) and HCA time (OR 1.03/min). When only the 271 elective patients were analyzed separately, the need for a concomitant procedure (p = 0.009, OR 3.6) and HCA time (p = 0.002, OR 1.06/min) were the only predictors of AO in multivariate analysis. Transient neurological dysfunction (TND) occurred in 86 of 392 patients (22%). Significant predictors of TND for all patients without AO were age (OR 1.06/y), HCA time (OR 1.04/min), coronary artery disease (OR 2.2), hemodynamic instability (OR 3.4), and acute operation (OR 2.2). Survival of discharged patients was 93% at 1 year and 83% at 5 years.

CONCLUSIONS

Early elective operation and shorter HCA time during ascending aorta/hemiarch surgery will reduce both AO and TND.

Simultaneous carotid endarterectomy and coronary revascularization

BACKGROUND

Combined cardiac operation and carotid endarterectomy using our technique is an acceptable approach to simultaneous correction of both carotid and cardiac disease.

METHODS

From August 1989 to March 1998, 121 consecutive patients underwent combined operations. Of these patients, 112 had coronary artery bypass grafting and carotid endarterectomy, and 9 had coronary artery bypass grafting, carotid endarterectomy, and valve repair or replacement. All patients had a critical stenosis of 85% or more of the carotid artery. Mean age of the patients was 69.2 years; 80 patients were 65 years old or older. There were 88 men and 33 women. Notable risk factors included chronic obstructive pulmonary disease (19.8%), congestive heart failure (28%), preoperative myocardial infarction and unstable angina (66.9%). Of the patients, 20.7% had a stenosis of greater than 50% of the left main coronary artery. The technique used was correction of both the carotid and coronary lesions during a single aortic cross-clamp period using retrograde continuous blood cardioplegia for myocardial protection. Systemic hypothermia to 25 degrees C was used for cerebral protection.

RESULTS

Mean cross-clamp time was 118 minutes. Seven patients (5.8%) sustained perioperative cerebrovascular accidents. Two patients had transient ischemic attacks. The procedure-related mortality rate was 5.8%.

CONCLUSIONS

The described technique is a good method for simultaneous repair of coronary and carotid lesions in a high-risk group of patients with concomitant disease. We will continue to use it.

Cold retrograde cerebral perfusion improves cerebral protection during moderate hypothermic circulatory arrest: A long-term study in a porcine model

BACKGROUND

Deep hypothermic circulatory arrest is an effective method of cerebral protection, but it is associated with long cardiopulmonary bypass times and coagulation disturbances. Previous studies have shown that retrograde cerebral perfusion can improve neurologic outcomes after prolonged hypothermic circulatory arrest. We tested the hypothesis that deep hypothermic retrograde cerebral perfusion could improve cerebral outcome during moderate hypothermic circulatory arrest.

METHODS

Twelve pigs (23-29 kg) were randomly assigned to undergo either retrograde cerebral perfusion (15 degrees C) at 25 degrees C or hypothermic circulatory arrest with the head packed in ice at 25 degrees C for 45 minutes. Flow was adjusted to maintain superior vena cava pressure at 20 mm Hg throughout retrograde cerebral perfusion. Hemodynamic, electrophysiologic, metabolic, and temperature monitoring were carried out until 4 hours after the start of rewarming. Daily behavioral assessment was performed until elective death on day 7. A postmortem histologic analysis of the brain was carried out on all animals.

RESULTS

In the retrograde cerebral perfusion group, 5 (83%) of 6 animals survived 7 days compared with 2 (33%) of 6 in the hypothermic circulatory arrest group. Complete behavioral recovery was seen in 4 (67%) animals after retrograde cerebral perfusion but only in 1 (17%) animal after hypothermic circulatory arrest. Postoperative levels of serum lactate were higher, and blood pH was lower in the hypothermic circulatory arrest group. There were no significant hemodynamic differences between the study groups.

CONCLUSIONS

Cold hypothermic retrograde cerebral perfusion during moderate hypothermic circulatory arrest seems to improve neurologic outcome compared with moderate hypothermic circulatory arrest with the head packed in ice.

Surgical techniques. Aortic arch and deep hypothermic circulatory arrest: real-life suspended animation

Surgical reconstruction of the aortic arch is a complex procedure requiring careful preoperative analysis of the pathology and forethought toward surgical approach. Development of surgical techniques has brought dramatic improvement survival and reduction of neurological events associated with these procedures, yet significant morbidity is still encountered. New approaches to the patient with these pathologies include antegrade and retrograde perfusions to the brain. Continued research into physiology of hypothermic circulatory arrest offers the promise of pharmacological protection of the brain during aortic reconstruction and potentially development of therapeutic modalities to treat and limit ischemic brain damage.

Surgery for acute type A aortic dissection

BACKGROUND

Several innovative approaches have been introduced in the surgical treatment of acute type A aortic dissection. This study examines the effects of these new techniques on the early and late outcomes of patients with this disease.

METHODS

The records of patients who had surgery for acute type A aortic dissection during an 18 year interval were reviewed. There were 109 patients: 81 men and 28 women, with a mean age of 57 years, range 23 to 80. Most patients were acutely ill and 15 were in shock at the time of surgery. Operations were performed under cardiopulmonary bypass with femoral artery and right atrial cannulation. In 55 patients, the aorta was clamped and retrograde femoral perfusion was used throughout the procedure (group I). In 54 patients, no clamp was used; under circulatory arrest the primary tear was resected whether in the ascending aorta or transverse arch, and antegrade cardiopulmonary bypass was started after completion of the distal anastomosis (group II). Postoperative computed tomographic or magnetic resonance scans were completed annually.

RESULTS

There were 16 operative deaths (15%): 11 (20%) in group I, and 5 (9.2%) in group II (p = 0.10). There were 10 strokes: 8 (14.5%) in group I and 2 (3.7%) in group II (p = 0.05). After a mean follow-up time of 59 +/- 45 months for group I, 31 (56%) patients were alive, and after a mean follow-up time of 45 +/- 26 months for group II, 44 (81%) patients were alive. The actuarial survival of group II was higher than group I, but the difference was not significant (p = 0.09). Postoperatively, a patent false lumen was found in 91% of group I patients and in 59% of group II (p = 0.01).

CONCLUSIONS

This study suggests that avoidance of aortic clamping, resection of the primary tear in the ascending aorta or transverse arch, and antegrade perfusion after completion of the distal anastomosis improve the early and late outcomes of surgery for acute type A aortic dissection.