A propensity score–matched comparison of deep versus mild hypothermia during thoracoabdominal aortic surgery

Cool-Shot Technique to Protect Spinal Cord during Thoracoabdominal Aortic Replacement

Deep hypothermia helps protect the spinal cord, but is invasive. Here, we present a method to avoid reperfusion injury by selectively circulating cold blood under high pressure to the intercostal artery during reperfusion after intercostal artery reconstruction. Of the 23 patients who underwent thoracoabdominal aortic aneurysm open repair, one died. The motor evoked potential disappeared during aortic clamping in nine patients. Six patients recovered completely from aortic clamping release, two showed recovery >50% and one achieved full recovery 3 months later. Permanent motor impairment did not occur. This method could prevent reperfusion injury and paraplegia following thoracoabdominal aortic aneurysm surgery.

Spinal cord protection in open and endovascular approaches to thoracoabdominal aortic aneurysms

Despite advancements in surgical and postoperative management, spinal cord injury has been a persistent complication of both open and endovascular repair of thoracoabdominal and descending thoracic aortic aneurysm. Spinal cord injury can be explained with an ischemia-infarction model which results in local edema of the spinal cord, damaging its structure and leading to reversible or irreversible loss of its function. Perfusion of the spinal cord during aortic procedures can be enhanced by several adjuncts which have been described with a broad variety of evidence in their support. These adjuncts include systemic hypothermia, cerebrospinal fluid drainage, extracorporeal circulation and distal aortic perfusion, segmental arteries reimplantation, left subclavian artery revascularization, and staged aortic repair. The Authors here reviewed and discussed the role of such adjuncts in preventing spinal cord injury from occurring, pinpointing current evidence and outlining future perspectives.

Open surgical replacement of the descending aorta: single-center experience

Background

This study presents a single center's experience and analyzes clinical outcomes following elective open surgical descending aortic replacement.

Methods

Between January 2000 and August 2019, 96 patients with mean age 64 years (range, 49.5-71 years) (62.5% (n=60) male) underwent elective descending aortic replacement due to aneurysm (n=60) or chronic dissection (n=36). Marfan syndrome was present in 12 patients (12.5%).

Results

In-hospital mortality rate was 3.1% (n= 3. 2 in the aneurysm group, 1 in the dissection group). New-onset renal insufficiency postoperatively with (creatinine ≥ 2.5 mg/dl) manifested in 10 patients (10.8%). One patient (1%) suffered from stroke, and paraplegia developed in 1 pts (1%). The median follow-up time was 7 years (IQR: 2.5-13 years). The 5- and 10-year survival rates were 70.8% and 50.7% respectively. We did not observe any early or late prosthetic graft infection. The Cox proportional hazards regression analysis identified age (HR: 1.044, 95% CI: 1.009-1.080, p-value: 0.014), diabetes (HR: 2.544, 95% CI: 1.009-6.413, p-value: 0.048), and chronic obstructive pulmonary disease (COPD) (HR: 2.259, 95% CI: 1.044-4.890, p-value: 0.039) as risk factors for late mortality.

Conclusions

This study showed that the elective open surgical replacement of the descending aorta can be achieved with excellent outcomes in terms of perioperative mortality and morbidity. Prosthetic graft is not a problem with open surgical descending aortic replacement, even in the long term.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12055-022-01443-x.

Rewarming With Closed Thoracic Lavage Following 3-h CPR at 27°C Failed to Reestablish a Perfusing Rhythm

Introduction: Previously, we showed that the cardiopulmonary resuscitation (CPR) for hypothermic cardiac arrest (HCA) maintained cardiac output (CO) and mean arterial pressure (MAP) to the same reduced level during normothermia (38°C) vs. hypothermia (27°C). In addition, at 27°C, the CPR for 3-h provided global O₂ delivery (DO₂) to support aerobic metabolism. The present study investigated if rewarming with closed thoracic lavage induces a perfusing rhythm after 3-h continuous CPR at 27°C.

Materials and Methods: Eight male pigs were anesthetized, and immersion-cooled. At 27°C, HCA was electrically induced, CPR was started and continued for a 3-h period. Thereafter, the animals were rewarmed by combining closed thoracic lavage and continued CPR. Organ blood flow was measured using microspheres.

Results: After cooling with spontaneous circulation to 27°C, MAP and CO were initially reduced by 37 and 58% from baseline, respectively. By 15 min after the onset of CPR, MAP, and CO were further reduced by 58 and 77% from baseline, respectively, which remained unchanged throughout the rest of the 3-h period of CPR. During CPR at 27°C, DO₂ and O₂ extraction rate (VO₂) fell to critically low levels, but the simultaneous small increase in lactate and a modest reduction in pH, indicated the presence of maintained aerobic metabolism. During rewarming with closed thoracic lavage, all animals displayed ventricular fibrillation, but only one animal could be electro-converted to restore a short-lived perfusing rhythm. Rewarming ended in circulatory collapse in all the animals at 38°C.

Conclusion: The CPR for 3-h at 27°C managed to sustain lower levels of CO and MAP sufficient to support global DO₂. Rewarming accidental hypothermia patients following prolonged CPR for HCA with closed thoracic lavage is not an alternative to rewarming by extra-corporeal life support as these patients are often in need of massive cardio-pulmonary support during as well as after rewarming.

Splanchnic occlusive disease predicts for spinal cord injury after open descending thoracic and thoracoabdominal aneurysm repair

OBJECTIVE

In the present study, we sought to discern the effects of splanchnic occlusive disease (SOD; renal, superior mesenteric, and/or celiac axis arteries) on spinal cord injury (SCI; paraparesis or paraplegia) and major adverse events (MAE) after descending thoracic aneurysm (DTA) and thoracoabdominal aortic aneurysm (TAAA) open repair.

METHODS

Patients who had undergone DTA/TAAA repair at our institution were dichotomized according to the presence of SOD, which was investigated as a predictive factor of our primary (SCI) and secondary (operative mortality, myocardial infarction, stroke, tracheostomy, de novo dialysis, MAE, survival) endpoints. Risk adjustment used both propensity score matching and multivariable logistic regression.

RESULTS

From July 1997 to October 2019, 888 patients had undergone DTA/TAAA repair, of whom 19 were excluded from our analysis for missing data. SOD was absent in 712 patients and present in 157 patients. The patients with SOD had presented with a greater incidence of preoperative renal impairment (61 [38.9%] vs 175 [24.6%]; P < .01) and peripheral arterial disease (60 [38.2%] vs 162 [22.8%]; P < .01] and decreased left ventricular ejection fraction (45%; interquartile range, 10%; vs 50%; interquartile range, 4%; P < .01). The etiology of aortic disease was more frequently dissection in the SOD group (56.1% vs 43.7%) and more frequently nondissecting aneurysm in the non-SOD group (56.3% vs 43.9%; P < .01). Patients without SOD had presented with aneurysms more cranially located (DTA, 34.0% vs 7.6%; extent I TAAA, 44.0% vs 7.6%). In contrast, patients with SOD had presented with aneurysms more caudally located (extent II TAAA, 36.9% vs 8.6%; extent III TAAA, 30.6% vs 11.0%; extent IV TAAA, 17.2% vs 2.5%; P < .01). Propensity score matching led to 144 pairs, with SOD significantly associated with SCI (10 [6.9%] vs 2 [1.4%]; P = .03) and MAE (47 [32.6%] vs 26 [15%]; P < .01). Ten-year survival was reduced in those with SOD (31.5% vs 45.2%; P < .01). Conditional multivariable regression confirmed SOD to be a predictor of SCI in the matched sample (odds ratio, 6.60; P = .02).

CONCLUSIONS

Our results have shown that SOD is a significant predictor of SCI in patients undergoing open DTA/TAAA repair. The investigation of measures to prolong neuronal ischemia tolerance (eg, hypothermia) is warranted for such patients.

Estimation Model for Hypothermic Circulatory Arrest Time to Predict Risk in Total Arch Replacement

BACKGROUND

We created an estimation model for hypothermic circulatory arrest time and analyzed the risk factors for major adverse outcomes in total arch replacement.

METHODS

This study involved 272 patients who underwent total arch replacement. The estimation model for hypothermic circulatory arrest time was established using multiple linear regression analysis, and the predicted hypothermic circulatory arrest time from this model was analyzed to detect risk factors.

RESULTS

Atrial fibrillation, rupture, malperfusion, saccular aneurysm, cardiopulmonary bypass time, and hypothermic circulatory arrest time were identified as independent risk factors associated with major adverse outcomes. The estimation model for hypothermic circulatory arrest time was established as follows: hypothermic circulatory arrest time = 99.3 - 0.19 × age + 0.65 × body mass index + 6.19 × previous cardiac operation + 11.7 × acute dissection + 8.9 × rupture + 0.19 × aortic angulation + 0.15 × length to the distal anastomosis site - 6.17 × total arch replacement surgeon case volume - 3.06 × surgery year. The predicted hypothermic circulatory arrest time calculated by this estimation model was evaluated using multivariate logistic analysis, which identified atrial fibrillation, rupture, malperfusion, saccular aneurysm, and predicted hypothermic circulatory arrest time as risk factors.

CONCLUSIONS

As with the actual hypothermic circulatory arrest time, the predicted hypothermic circulatory arrest time using our model detected significant factors associated with major adverse outcomes. These results indicated that this prediction model for hypothermic circulatory arrest time may be effective.

Staged total arch replacement, followed by fenestrated-branched endovascular aortic repair, for patients with mega aortic syndrome

OBJECTIVE

The aim of the present study was to review the clinical outcomes of a staged approach using total arch replacement (TAR) with an elephant trunk or a frozen elephant trunk, followed by fenestrated-branched endovascular aortic repair (F-BEVAR) for patients with mega aortic syndrome.

METHODS

We reviewed the clinical data and outcomes of 11 consecutive patients (8 men; mean age, 71 ± 7 years) treated by staged TAR and F-BEVAR from January 2014 to December 2018. The F-BEVAR procedures were performed under a prospective, nonrandomized, physician-sponsored investigational device exemption protocol. All patients had had mega aortic syndrome, defined by an ascending aorta, arch, and extent I-II thoracoabdominal aortic aneurysm. The endpoints were 30-day mortality, major adverse events (MAE), patient survival, freedom from reintervention, and freedom from target vessel instability.

RESULTS

Of the 11 patients, 6 had developed chronic postdissection aneurysms after previous Stanford A (three A₁₁, two A₁₀, one A₉) dissection repair and 5 had had degenerative aneurysms with no suitable landing zone in the aortic arch. The thoracoabdominal aortic aneurysms were classified as extent I in four patients and extent II in seven. One patient had died within 30 days after TAR (9.0%). However, none of the remaining 10 patients who had undergone F-BEVAR had died. First-stage TAR resulted in MAE in three patients (27%), including one spinal cord injury. The mean length of stay was 12 ± 6 days. The mean interval between TAR and F-BEVAR was 245 ± 138 days with no aneurysm rupture during the interval. Second-stage F-BEVAR was associated with MAE in two patients (20%), including spinal cord injury in one patient from spinal hematoma due to placement of a cerebrospinal fluid drain. The mean follow-up period was 14 ± 10 months. At 2 years postoperatively, patient survival, primary patency, secondary patency, and freedom from renal-mesenteric target vessel instability was 80% ± 9%, 94% ± 6%, 100%, and 86% ± 8%, respectively. No aortic-related deaths occurred during the follow-up period. Four patients had required reintervention, all performed using an endovascular approach.

CONCLUSIONS

A staged approach to treatment of mega aortic syndrome using TAR and F-BEVAR is a feasible alternative for selected high-risk patients. Larger clinical experience and longer follow-up are needed.

Review: perspectives on renal and visceral protection during thoracoabdominal aortic aneurysm repair

Open repair of a thoracoabdominal aortic aneurysm (TAAA) is an extensive operation and associated with significant perioperative morbidities and mortality, in large part due to distal aortic ischemia secondary to aortic cross-clamping that is necessitated during repair. Distal aortic ischemia may manifest as complications of the kidneys and viscera. Postoperative renal complications range from temporarily elevated levels of creatinine resulting from impaired kidney function to acute renal failure necessitating dialysis that may persist after hospital discharge. Continued advances in the management and adjuncts associated with TAAA repair since the groundbreaking era of E.S. Crawford have led to improved postoperative outcomes following surgery, but the dramatic improvements seen in reducing rates of spinal cord deficits, mesenteric ischemia and other serious postoperative complications have not been seen in contemporary rates of postoperative renal failure. We provide an overview of the various surgical techniques and adjuncts as they relate to the management of visceral and renal ischemia.

State-of the-art review on the renal and visceral protection during open thoracoabdominal aortic aneurysm repair

During open thoracoabdominal aortic aneurysm repair (OTAAAR), there is an inevitable organ ischemic period that occurs when the abdominal arteries are being reattached to the aortic graft. Despite various protective techniques, the incidence of renal and visceral complications remains substantial. This state-of-the-art review gives an overview of the current and most evidence-based organ protection methods during OTAAAR, based on the most recent publications and personal experience. An electronic search was performed in four medical databases, using the following MeSH terms: thoracoabdominal aneurysm, TAAAR, visceral protection, renal protection, kidney, perfusion, and intestines. Every publication type was considered. The literature search was ended on August 31st, 2017. The left heart bypass (LHB) is currently the most frequent adjunct to provide distal aortic perfusion (DAP) during aortic clamping. Together with systemic hypothermia, it forms the cornerstone in organ protection during aortic clamping. Further renal protection can be obtained by selective renal perfusion (SRP) with cold blood or cold crystalloid solution, the latter enriched with mannitol. The perfusion should be administered in a volume- and pressure-controlled way and, if possible, by use of a pulsatile pump. Selective visceral perfusion (SVP) is not routinely used, as it does not provide adequate blood flow for visceral protection. The best way to protect the intestines is by minimizing the ischemic time. The preservation of renal and visceral function after OTAAAR can only be obtained with specific strategies before, during, and after the operation. This involves a series of measures, including selective digestive decontamination (SDD), avoidance of nephrotoxic drugs, minimizing the renal and intestinal ischemic time, systemic cooling, avoidance of hemodynamic instability, and regional protective perfusion of the kidneys. Future innovations in catheters, cardiac bypass flow types, mechanical components, hybrid vascular grafts, and pharmaceutical protection measures will hopefully further reduce organ complications.

Midterm Outcomes of Open Descending Thoracic Aortic Repair in More Than 5,000 Medicare Patients

BACKGROUND

Diseases involving the descending thoracic aorta (DTA) represent a heterogeneous substrate with a variety of therapeutic options. Although thoracic endovascular aortic repair has been increasingly applied to DTA disease, open surgical repair is ostensibly more durable.

METHODS

A total of 5,578 patients who underwent open DTA repair (Current Procedural Terminology code 33875) from 1999 to 2010 were identified from the Medicare database; 5,489 patients had complete data. Survival was assessed with Kaplan-Meier analysis. Cox regression determined predictors of death. Hospital and surgeon volume and variability were modeled, and their association with survival assessed.

RESULTS

Median survival after open DTA repair was only 4.3 years (95% confidence interval: 4.0 to 4.6). The likelihood of death varied significantly by certain aortic diseases: aortic rupture and acute aortic dissection patients had the highest early mortality. Survival beyond 180 days was best for patients with acute aortic dissection and isolated thoracic aortic aneurysm, and lowest for patients with thoracoabdominal aneurysm and aortic rupture. Hospital and surgeon volume, as well as interhospital and intersurgeon variability, had associations with overall survival.

CONCLUSIONS

Open DTA repair has treated a spectrum of aortic diseases in Medicare beneficiaries. Overall mortality was high, predominately confined to the initial postoperative hazard phase. Independent hospital and surgeon effects, hospital and surgeon volume, and a more recent date of surgery correlated with improved survival, while increased operative urgency and complexity correlated with worse outcomes. These observations argue for regionalization of DTA treatment for Medicare patients in specialized centers to concentrate expertise, which should translate into better outcomes.

Robust control of burst suppression for medical coma

OBJECTIVE

Medical coma is an anesthetic-induced state of brain inactivation, manifest in the electroencephalogram by burst suppression. Feedback control can be used to regulate burst suppression, however, previous designs have not been robust. Robust control design is critical under real-world operating conditions, subject to substantial pharmacokinetic and pharmacodynamic parameter uncertainty and unpredictable external disturbances. We sought to develop a robust closed-loop anesthesia delivery (CLAD) system to control medical coma.

APPROACH

We developed a robust CLAD system to control the burst suppression probability (BSP). We developed a novel BSP tracking algorithm based on realistic models of propofol pharmacokinetics and pharmacodynamics. We also developed a practical method for estimating patient-specific pharmacodynamics parameters. Finally, we synthesized a robust proportional integral controller. Using a factorial design spanning patient age, mass, height, and gender, we tested whether the system performed within clinically acceptable limits. Throughout all experiments we subjected the system to disturbances, simulating treatment of refractory status epilepticus in a real-world intensive care unit environment.

MAIN RESULTS

In 5400 simulations, CLAD behavior remained within specifications. Transient behavior after a step in target BSP from 0.2 to 0.8 exhibited a rise time (the median (min, max)) of 1.4 [1.1, 1.9] min; settling time, 7.8 [4.2, 9.0] min; and percent overshoot of 9.6 [2.3, 10.8]%. Under steady state conditions the CLAD system exhibited a median error of 0.1 [-0.5, 0.9]%; inaccuracy of 1.8 [0.9, 3.4]%; oscillation index of 1.8 [0.9, 3.4]%; and maximum instantaneous propofol dose of 4.3 [2.1, 10.5] mg kg(-1). The maximum hourly propofol dose was 4.3 [2.1, 10.3] mg kg(-1) h(-1). Performance fell within clinically acceptable limits for all measures.

SIGNIFICANCE

A CLAD system designed using robust control theory achieves clinically acceptable performance in the presence of realistic unmodeled disturbances and in spite of realistic model uncertainty, while maintaining infusion rates within acceptable safety limits.

The human burst suppression electroencephalogram of deep hypothermia

OBJECTIVE

Deep hypothermia induces 'burst suppression' (BS), an electroencephalogram pattern with low-voltage 'suppressions' alternating with high-voltage 'bursts'. Current understanding of BS comes mainly from anesthesia studies, while hypothermia-induced BS has received little study. We set out to investigate the electroencephalogram changes induced by cooling the human brain through increasing depths of BS through isoelectricity.

METHODS

We recorded scalp electroencephalograms from eleven patients undergoing deep hypothermia during cardiac surgery with complete circulatory arrest, and analyzed these using methods of spectral analysis.

RESULTS

Within patients, the depth of BS systematically depends on the depth of hypothermia, though responses vary between patients except at temperature extremes. With decreasing temperature, burst lengths increase, and burst amplitudes and lengths decrease, while the spectral content of bursts remains constant.

CONCLUSIONS

These findings support an existing theoretical model in which the common mechanism of burst suppression across diverse etiologies is the cyclical diffuse depletion of metabolic resources, and suggest the new hypothesis of local micro-network dropout to explain decreasing burst amplitudes at lower temperatures.

SIGNIFICANCE

These results pave the way for accurate noninvasive tracking of brain metabolic state during surgical procedures under deep hypothermia, and suggest new testable predictions about the network mechanisms underlying burst suppression.

Outcomes of open surgical repair of descending thoracic aortic disease

Background

To determine the predictors of clinical outcomes following surgical descending thoracic aortic (DTA) repair.

Methods

We identified 103 patients (23 females; mean age, 64.1±12.3 years) who underwent DTA replacement from 1999 to 2011 using either deep hypothermic circulatory arrest (44%) or partial cardiopulmonary bypass (CPB, 56%).

Results

The early mortality rate was 4.9% (n=5). Early major complications occurred in 21 patients (20.3%), which included newly required hemodialysis (9.7%), low cardiac output syndrome (6.8%), pneumonia (7.8%), stroke (6.8%), and multi-organ failure (3.9%). None experienced paraplegia. During a median follow-up of 56.3 months (inter-quartile range, 23.1 to 85.1 months), there were 17 late deaths and one aortic reoperation. Overall survival at 5 and 10 years was 80.9%±4.3% and 71.7%±5.9%, respectively. Reoperation-free survival at 5 and 10 years was 77.3%±4.8% and 70.2%±5.8%. Multivariable analysis revealed that age (hazard ratio [HR], 1.10; 95% confidence interval [CI], 1.05 to 1.15; p<0.001) and left ventricle (LV) function (HR, 0.88; 95% CI, 0.82 to 0.96; p<0.003) were significant and independent predictors of long-term mortality. CPB strategy, however, was not significantly related to mortality (p=0.49).

Conclusion

Surgical DTA repair was practicable in terms of acceptable perioperative mortality/morbidity as well as favorable long-term survival. Age and LV function were risk factors for long-term mortality, irrespective of the CPB strategy.

Surgical repair of descending thoracic and thoracoabdominal aortic aneurysm involving the distal arch: open proximal anastomosis under deep hypothermia versus arch clamping technique

BACKGROUND

Surgical repair of a descending thoracic and thoracoabdominal aortic aneurysm (DTA/TAAA) involving the distal arch is challenging and requires either deep hypothermic circulatory arrest (DHCA) or crossclamping of the distal arch. The aim of this study was to compare these 2 techniques in the treatment of DTA/TAAA involving the distal arch.

METHODS

From 1994 to 2012, 298 patients underwent open repair of DTA/TAAA through a left thoracotomy. One hundred seventy-four patients with distal arch involvement who were suitable for either DHCA (n=81) or arch clamping (AC; n=93), were analyzed. In-hospital outcomes were compared using propensity scores and inverse-probability-of-treatment weighting adjustment to reduce treatment selection bias.

RESULTS

Early mortality was 11.1% in the DHCA group and 8.6% in the AC group (P=.58). Major adverse outcomes included stroke in 16 patients (9.2%), low cardiac output syndrome in 15 (8.6%), paraplegia in 10 (5.7%), and multiorgan failure in 10 (5.7%). After adjustment, patients who underwent DHCA were at similar risk of death (odds ratio [OR], 1.14; P=.80) and permanent neurologic injury (OR, 0.95; P=.92) to those who underwent AC. Although prolonged ventilator support (>24 hours) was more frequent with DHCA than with AC (OR, 2.60; P=.003), DHCA showed a tendency to lower the risk of paraplegia (OR, 0.15; P=.057).

CONCLUSIONS

Compared with AC, DHCA did not increase postoperative mortality and morbidity, except for prolonged ventilator support. However, DHCA may offer superior spinal cord protection to AC during repair of DTA/TAAA involving the distal arch.

Marfan Syndrome

Marfan syndrome is a multisystem connective tissue disorder, with primary involvement of the cardiovascular, ocular, and skeletal systems. This autosomal heritable disease is mainly attributable to a defect in the FBN1 gene. Clinical diagnosis of Marfan syndrome has been based on the Ghent criteria since 1996. In 2010, these criteria were updated, and the revised guidelines place more emphasis on aortic root dilation, ectopia lentis, and FBN1 mutation testing in the diagnostic assessment of Marfan syndrome. Among its many different clinical manifestations, cardiovascular involvement deserves special consideration, owing to its impact on prognosis. Recent molecular, surgical, and clinical research has yielded profound new insights into the pathological mechanisms that ultimately lead to tissue degradation and weakening of the aortic wall, which has led to exciting new treatment strategies. Furthermore, with the increasing life expectancy of patients with Marfan syndrome, there has been a subtle shift in the spectrum of medical problems. Consequently, this article focuses on recent advances to highlight their potential impact on future concepts of patient care from a clinical, surgical, and anesthetic perspective.

Hypothermia for aortic surgery

Hypothermic circulatory arrest has been used during aortic arch repairs with acceptable neurologic outcomes. Through the years, we have studied the effects of deep hypothermia on brain metabolism and perfusion both in a pig model and in surgical patients. Hypothermic circulatory arrest has also been used as a method of organ protection in the repair of thoracoabdominal aortic aneurysms. We summarize the clinical and laboratory studies to support the routine use of hypothermic circulatory arrest in clinical practice.

Predictors of electrocerebral inactivity with deep hypothermia

OBJECTIVE

Cooling to electrocerebral inactivity (ECI) by electroencephalography (EEG) remains the gold standard to maximize cerebral and systemic organ protection during deep hypothermic circulatory arrest (DHCA). We sought to determine predictors of ECI to help guide cooling protocols when EEG monitoring is unavailable.

METHODS

Between July 2005 and July 2011, 396 patients underwent thoracic aortic operation with DHCA; EEG monitoring was used in 325 (82%) of these patients to guide the cooling strategy, and constituted the study cohort. Electroencephalographic monitoring was used for all elective cases and, when available, for nonelective cases. Multivariable linear regression was used to assess predictors of the nasopharyngeal temperature and cooling time required to achieve ECI.

RESULTS

Cooling to a nasopharyngeal temperature of 12.7°C or for a duration of 97 minutes was required to achieve ECI in >95% of patients. Only 7% and 11% of patients achieved ECI by 18°C or 50 minutes of cooling, respectively. No independent predictors of nasopharyngeal temperature at ECI were identified. Independent predictors of cooling time included body surface area (18 minutes/m(2)), white race (7 minutes), and starting nasopharyngeal temperature (3 minutes/°C). Low complication rates were observed (ischemic stroke, 1.5%; permanent paraparesis/paraplegia, 1.5%; new-onset dialysis, 2.2%; and 30-day/in-hospital mortality, 4.3%).

CONCLUSIONS

Cooling to a nasopharyngeal temperature of 12.7°C or for a duration of 97 minutes achieved ECI in >95% of patients in our study population. However, patient-specific factors were poorly predictive of the temperature or cooling time required to achieve ECI, necessitating EEG monitoring for precise ECI detection.