Temperature management in cardiac surgery

Kidney protection during surgery on the thoracoabdominal aorta: a systematic review

OBJECTIVES

Acute kidney injury (AKI) is a common consequence of surgical repair of the thoraco-abdominal aorta (TAA). Perfusion techniques aim to facilitate renal protection through oxygenation or hypothermia. This systematic review assesses renal and mortality outcomes by perfusion techniques to evaluate their ability to provide effective kidney protection.

METHODS

PubMed, Web of Science, ClinicalTrials.gov and ClinicalTrialsRegister.EU were searched to identify relevant studies published from 1995 to 2024. Following quality assessment and data extraction, outcomes of the highest quality studies were used to synthesize a narrative discussion.

RESULTS

Thirty-eight studies were analysed, featuring three extracorporeal strategies: left heart bypass (LHB; n = 22), cardiopulmonary bypass with deep hypothermic circulatory arrest (DHCA; n = 11) and partial cardiopulmonary bypass (pCPB; n = 10). Three categories of selective renal perfusion (SRP) strategy were identified: warm blood, cold blood and cold crystalloid. Five studies of 'very high' and 'high' quality demonstrate a 0-13.6% incidence of post-operative dialysis and 5.0-13.3% risk of operative mortality following LHB with cold crystalloid SRP. No studies in support of DHCA or pCPB provided a high quality of evidence.

CONCLUSIONS

Left heart bypass with crystalloid SRP provides a benchmark for rates of dialysis and mortality following TAA repair. However, AKI remains significant, emphasizing the need for continued innovation in SRP, and a greater understanding of overlooked risk factors. DHCA and pCPB are supported by low-quality evidence, meaning that prospective research is necessary to enable fair comparison. Finally, consensus on data reporting is recommended to improve the quality of future studies in this area.

Diffuse Optical Monitoring of Cerebral Hemodynamics and Oxygen Metabolism during and after Cardiopulmonary Bypass: Hematocrit Correction and Neurological Vulnerability

Cardiopulmonary bypass (CPB) provides cerebral oxygenation and blood flow (CBF) during neonatal congenital heart surgery, but the impacts of CPB on brain oxygen supply and metabolic demands are generally unknown. To elucidate this physiology, we used diffuse correlation spectroscopy and frequency-domain diffuse optical spectroscopy to continuously measure CBF, oxygen extraction fraction (OEF), and oxygen metabolism (CMRO2) in 27 neonatal swine before, during, and up to 24 h after CPB. Concurrently, we sampled cerebral microdialysis biomarkers of metabolic distress (lactate-pyruvate ratio) and injury (glycerol). We applied a novel theoretical approach to correct for hematocrit variation during optical quantification of CBF in vivo. Without correction, a mean (95% CI) +53% (42, 63) increase in hematocrit resulted in a physiologically improbable +58% (27, 90) increase in CMRO2 relative to baseline at CPB initiation; following correction, CMRO2 did not differ from baseline at this timepoint. After CPB initiation, OEF increased but CBF and CMRO2 decreased with CPB time; these temporal trends persisted for 0-8 h following CPB and coincided with a 48% (7, 90) elevation of glycerol. The temporal trends and glycerol elevation resolved by 8-24 h. The hematocrit correction improved quantification of cerebral physiologic trends that precede and coincide with neurological injury following CPB.

Technical Tips for Performing Suprahepatic Vena Cava Tumor Thrombectomy in Renal Cell Carcinoma without Using Cardiopulmonary Bypass

Radical nephrectomy with tumor thrombectomy for advanced renal cell carcinoma is an oncologically relevant approach that can achieve long-term survival even in the presence of distant metastases. However, the surgical techniques pose significant challenges. The objective of this clinical review was to present technical recommendations for tumor thrombectomy in the vena cava to facilitate surgical treatment. Transesophageal echocardiography is required to prepare for this procedure. Cardiopulmonary bypass should be considered when the tumor thrombus has invaded the cardiac chamber and clamping is not feasible because of the inability to milk the intracardiac chamber thrombus in the caudal direction. Prior to performing a cavotomy, it is crucial to clamp the contralateral renal vein and infrarenal and suprahepatic inferior vena cava (IVC). If the suprahepatic IVC is separated from the surrounding tissue, it can be gently pulled down toward the patient's leg until the lower margin of the atrium becomes visible. Subsequently, the tumor thrombus should be carefully pulled downward to a position where it can be clamped. Implementing the Pringle maneuver to reduce blood flow from the hepatic veins to the IVC during IVC cavotomy is simpler than clamping the hepatic veins. Sequential clamping is a two-stage method of dividing thrombectomy by clamping the IVC twice, first suprahepatically and then midretrohepatically. This sequential clamping technique helps minimize hypotension status and the Pringle maneuver time compared to single clamping. Additionally, a spiral cavotomy can decrease the degree of primary closure narrowing. The oncological prognoses of patients can be improved by incorporating these technical recommendations.

Long-term ex situ normothermic perfusion of human split livers for more than 1 week

Current machine perfusion technology permits livers to be preserved ex situ for short periods to assess viability prior to transplant. Long-term normothermic perfusion of livers is an emerging field with tremendous potential for the assessment, recovery, and modification of organs. In this study, we aimed to develop a long-term model of ex situ perfusion including a surgical split and simultaneous perfusion of both partial organs. Human livers declined for transplantation were perfused using a red blood cell-based perfusate under normothermic conditions (36 °C) and then split and simultaneously perfused on separate machines. Ten human livers were split, resulting in 20 partial livers. The median ex situ viability was 125 h, and the median ex situ survival was 165 h. Long-term survival was demonstrated by lactate clearance, bile production, Factor-V production, and storage of adenosine triphosphate. Here, we report the long-term ex situ perfusion of human livers and demonstrate the ability to split and perfuse these organs using a standardised protocol.

Hypothermia is an independent risk factor for prolonged ICU stay in coronary artery bypass surgery: an observational study

Maintenance of normothermia is a critical perioperative issue. The warming process after hypothermia tends to increase oxygen demand, which may lead to myocardial ischemia. This study explored whether hypothermia was an independent risk factor for increased morbidity and mortality in patients receiving CABG. We conducted a retrospective observational study of CABG surgeries performed from January 2018 to June 2019. The outcomes of interest were mortality, surgical site infection rate, ventilator dependent time, intensive care unit (ICU) stay, and hospitalization duration. Data from 206 patients were analysed. Hypothermic patients were taller (p = 0.012), had lower left ventricular ejection fraction (p = 0.016), and had off-pump CABG more frequently (p = 0.04). Our analysis noted no incidence of mortality within 30 days. Hypothermia was not associated with higher surgical site infection rate or longer intubation time. After adjusting for sex, age, cardiopulmonary bypass duration, left ventricular ejection fraction, and EuroSCORE II, higher EuroSCORE II (p < 0.001; odds ratio 1.2) and hypothermia upon ICU admission (p = 0.04; odds ratio 3.8) were independent risk factors for prolonged ICU stay. In addition to EuroSCORE II, hypothermia upon ICU admission was an independent risk factor for prolonged ICU stay in patients receiving elective CABG.

Intraoperative blood collection without fluid replacement for cardiac surgery - A retrospective analysis

BACKGROUND

Transfusion rates in cardiac surgery are high.

AIM

To determine if intraoperative autologous blood removal without volume replacement is associated with fewer homologous blood transfusions without increasing acute kidney injury.

SETTING AND DESIGN

Retrospective, comparative study.

MATERIALS AND METHODS

Adult patients undergoing cardiac surgery, excluding those who underwent ventricular assist device surgery, heart transplants, or cardiac surgery without cardiopulmonary bypass were excluded, who had 1-3 units of intraoperative autologous blood removal were compared to patients without blood removal for determination of volume replacement, vasopressor support, acute kidney injury, and transfusions.

RESULTS

Autologous blood removal was associated with fewer patients receiving homologous transfusions: intraoperative red cell transfusions fell from 75% (Control) to 48% (1 unit removed), 40% (2 units), and 30% (3 units), P &lt; 0.001. Total intraoperative and postoperative homologous RBC units transfused were lower in the blood removal groups: median (interquartile range) 3 (1, 6) in Control patients and 0 (0, 2), 0 (0, 2) and 0 (0, 1) in the 1, 2, and 3 units removed groups, P &lt; 0.001. Similarly, plasma, platelet, and cryoprecipitate transfusions decreased. After adjustment for confounders, increased amounts of autologous blood removal were associated with increased intravenous fluids, only when 2 units were removed, and trivially increased vasopressor use. However, it was not associated with acidosis or acute kidney injury.

CONCLUSIONS

Intraoperative autologous blood removal without volume replacement of 1-3 units for later autologous transfusion is associated with decreased homologous transfusions without acidosis or acute kidney injury.

Therapeutic hypothermia for acute myocardial infarction: a narrative review of evidence from animal and clinical studies

Myocardial infarction (MI) is the leading cause of death from coronary heart disease and requires immediate reperfusion therapy with thrombolysis, primary percutaneous coronary intervention, or coronary artery bypass grafting. However, myocardial reperfusion therapy is often accompanied by cardiac ischemia/reperfusion (I/R) injury, which leads to myocardial injury with detrimental consequences. The causes of I/R injury are unclear, but are multifactorial, including free radicals, reactive oxygen species, calcium overload, mitochondria dysfunction, inflammation, and neutrophil-mediated vascular injury. Mild hypothermia has been introduced as one of the potential inhibitors of myocardial I/R injury. Although animal studies have demonstrated that mild hypothermia significantly reduces or delays I/R myocardium damage, human trials have not shown clinical benefits in acute MI (AMI). In addition, the practice of hypothermia treatment is increasing in various fields such as surgical anesthesia and intensive care units. Adequate sedation for anesthetic procedures and protection from body shivering has become essential during therapeutic hypothermia. Therefore, anesthesiologists should be aware of the effects of therapeutic hypothermia on the metabolism of anesthetic drugs. In this paper, we review the existing data on the use of therapeutic hypothermia for AMI in animal models and human clinical trials to better understand the discrepancy between perceived benefits in preclinical animal models and the absence thereof in clinical trials thus far.

Comparison of Perioperative Active or Routine Temperature Management on Postoperative Quality of Recovery in PACU in Patients Undergoing Thoracoscopic Lobectomy: A Randomized Controlled Study

BACKGROUND

Whether intraoperative temperature management can help patients recover quickly in the postanesthesia care unit (PACU) still remains to be investigated. This study aimed to investigate the effect of intraoperative temperature management on the quality of postoperative recovery of patients who underwent pulmonary lobectomy in the PACU.

METHODS

Totally, 98 patients aged 45-60 years with a body mass index of 20-25 kg/m² who underwent elective thoracoscopic lobectomy were enrolled. Patients were categorized into two groups using a random number table: the conventional group received routine intervention to maintain normothermia (Group C, n = 49) and the aggressive group received integrated interventions (Group A, n = 49). In Group C, normothermic fluid was infused intravenously, the heating blanket was turned on when the intraoperative temperature was <35.0 °C, and the warming was stopped when the temperature reached 36.5 °C. In Group A, the fluid heated to 37 °C was infused intravenously, and the heating blanket was used intraoperatively. When the body temperature was >37 °C, the heating blanket was turned off, and when the body temperature was <36.5 °C, the heating blanket was turned on to continue heating.

RESULTS

Steward awakening scores at 1 min and 5 min after extubation and PaO₂ levels at 15 min after extubation were higher in Group A than in Group C (P < 0.05); incidence of chills, nausea, and vomiting in the PACU was lower in Group A than in Group C (P < 0.05); and length of stay in the PACU was shorter in Group A than in Group C (P < 0.05).

CONCLUSION

Aggressive intraoperative temperature management of patients undergoing thoracoscopic lobectomy can improve the quality of postoperative recovery in the PACU through a safe and smooth transition compared with routine insulation measures.

Anesthesia for left ventricular assisted device insertion in a patient with multiple organ failure

Technological advances in mechanical circulatory support have enabled more patients with end-stage heart failure to benefit from left ventricular assist devices (LVAD). Indications for LVAD implantation have evolved to include patients who are deemed unsuitable for cardiac transplantation, otherwise known as destination therapy. This case report describes such patient with multi-organ failure who underwent LVAD insertion after nine days of extra-corporeal membrane oxygenation, intra-aortic balloon pump and maximal inotropic support. Strategies for perioperative management, as well as intra-operative monitoring and interventions are discussed.

Challenges in Patient Blood Management for Cardiac Surgery: A Narrative Review

About 15 years ago, Patient Blood Management (PBM) emerged as a new paradigm in perioperative medicine and rapidly found support of all major medical societies and government bodies. Blood products are precious, scarce and expensive and their use is frequently associated with adverse short- and long-term outcomes. Recommendations and guidelines on the topic are published in an increasing rate. The concept aims at using an evidence-based approach to rationalize transfusion practices by optimizing the patient's red blood cell mass in the pre-, intra- and postoperative periods. However, elegant as a concept, the implementation of a PBM program on an institutional level or even in a single surgical discipline like cardiac surgery, can be easier said than done. Many barriers, such as dogmatic ideas, logistics and lack of support from the medical and administrative departments need to be overcome and each center must find solutions to their specific problems. In this paper we present a narrative overview of the challenges and updated recommendations for the implementation of a PBM program in cardiac surgery.

The Impact of Accidental Hypothermia on Mortality in Trauma Patients Overall and Patients with Traumatic Brain Injury Specifically: A Systematic Review and Meta-Analysis

BACKGROUND

Accidental hypothermia is a known predictor for worse outcomes in trauma patients, but has not been comprehensively assessed in a meta-analysis so far. The aim of this systematic review and meta-analysis was to investigate the impact of accidental hypothermia on mortality in trauma patients overall and patients with traumatic brain injury (TBI) specifically.

METHODS

This is a systematic review and meta-analysis using the Ovid Medline/PubMed database. Scientific articles reporting accidental hypothermia and its impact on outcomes in trauma patients were included in qualitative synthesis. Studies that compared the effect of hypothermia vs. normothermia at hospital admission on in-hospital mortality were included in two meta-analyses on (1) trauma patients overall and (2) patients with TBI specifically. Meta-analysis was performed using a Mantel-Haenszel random-effects model.

RESULTS

Literature search revealed 264 articles. Of these, 14 studies published 1987-2018 were included in the qualitative synthesis. Seven studies qualified for meta-analysis on trauma patients overall and three studies for meta-analysis on patients with TBI specifically. Accidental hypothermia at admission was associated with significantly higher mortality both in trauma patients overall (OR 5.18 [95% CI 2.61-10.28]) and patients with TBI specifically (OR 2.38 [95% CI 1.53-3.69]).

CONCLUSIONS

In the current meta-analysis, accidental hypothermia was strongly associated with higher in-hospital mortality both in trauma patients overall and patients with TBI specifically. These findings underscore the importance of measures to avoid accidental hypothermia in the prehospital care of trauma patients.

Contactless Thermometry by MRI and MRS: Advanced Methods for Thermotherapy and Biomaterials

Control of temperature variation is of primordial importance in particular areas of biomedicine. In this context, medical treatments such as hyperthermia and cryotherapy, and also the development and use of hydrogel-based biomaterials, are of particular concern. To enable accurate temperature measurement without perturbing or even destroying the biological tissue or material to be monitored, contactless thermometry methods are preferred. Among these, the most suitable are based on magnetic resonance imaging and spectroscopy (MRI, MRS). Here, we address the latest developments in this field as well as their current and anticipated practical applications. We highlight recent progress aimed at rendering MR thermometry faster and more reproducible, versatile, and sophisticated and provide our perspective on how these new techniques broaden the range of applications in medical treatments and biomaterial development by enabling insight into finer details of thermal behavior. Thus, these methods facilitate optimization of clinical and industrial heating and cooling protocols.

Hypermetabolism in critically ill patients with COVID-19 and the effects of hypothermia: A case series

Background

We have observed that critically ill patients with COVID-19 are in an extreme hypermetabolic state. This may be a major contributing factor to the extraordinary ventilatory and oxygenation demands seen in these patients. We aimed to quantify the extent of the hypermetabolic state and report the clinical effect of the use of hypothermia to decrease the metabolic demand in these patients.

Methods

Mild hypothermia was applied on four critically ill patients with COVID-19 for 48 h. Metabolic rates, carbon dioxide production and oxygen consumption were measured by indirect calorimetry.

Results

The average resting energy expenditure (REE) was 299% of predicted. Mild hypothermia decreased the REE on average of 27.0% with resultant declines in CO₂ production (VCO₂) and oxygen consumption (VO₂) by 29.2% and 25.7%, respectively. This decrease in VCO₂ and VO₂ was clinically manifested as improvements in hypercapnia (average of 19.1% decrease in pCO₂ levels) and oxygenation (average of 50.4% increase in pO₂).

Conclusion

Our case series demonstrates the extent of hypermetabolism in COVID-19 critical illness and suggests that mild hypothermia reduces the metabolic rate, improves hypercapnia and hypoxia in critically ill patients with COVID-19.

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COVID-19 critical illness induces an extreme hypermetabolic state.

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Hypothermia attenuates the hypermetabolic response seen in patients with COVID-19.

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Hypothermia in patients with COVID-19 may improve carbon dioxide and oxygen levels.

Application of mild hypothermia successfully mitigates neural injury in a 3D in-vitro model of traumatic brain injury

Therapeutic hypothermia (TH) is an attractive target for mild traumatic brain injury (mTBI) treatment, yet significant gaps in our mechanistic understanding of TH, especially at the cellular level, remain and need to be addressed for significant forward progress to be made. Using a recently-established 3D in-vitro neural hydrogel model for mTBI we investigated the efficacy of TH after compressive impact injury and established critical treatment parameters including target cooling temperature, and time windows for application and maintenance of TH. Across four temperatures evaluated (31.5, 33, 35, and 37°C), 33°C was found to be most neuroprotective after 24 and 48 hours post-injury. Assessment of TH administration onset time and duration showed that TH should be administered within 4 hours post-injury and be maintained for at least 6 hours for achieving maximum viability. Cellular imaging showed TH reduced the percentage of cells positive for caspases 3/7 and increased the expression of calpastatin, an endogenous neuroprotectant. These findings provide significant new insight into the biological parameter space that renders TH effective in mitigating the deleterious effects of cellular mTBI and provides a quantitative foundation for the future development of animal and preclinical treatment protocols.

MR Thermometry in Cerebrovascular Disease: Physiologic Basis, Hemodynamic Dependence, and a New Frontier in Stroke Imaging

The remarkable temperature sensitivity of the brain is widely recognized and has been studied for its role in the potentiation of ischemic and other neurologic injuries. Pyrexia frequently complicates large-vessel acute ischemic stroke and develops commonly in critically ill neurologic patients; the profound sensitivity of the brain even to minor intraischemic temperature changes, together with the discovery of brain-to-systemic as well as intracerebral temperature gradients, has thus compelled the exploration of cerebral thermoregulation and uncovered its immutable dependence on cerebral blood flow. A lack of pragmatic and noninvasive tools for spatially and temporally resolved brain thermometry has historically restricted empiric study of cerebral temperature homeostasis; however, MR thermometry (MRT) leveraging temperature-sensitive nuclear magnetic resonance phenomena is well-suited to bridging this long-standing gap. This review aims to introduce the reader to the following: 1) fundamental aspects of cerebral thermoregulation, 2) the physical basis of noninvasive MRT, and 3) the physiologic interdependence of cerebral temperature, perfusion, metabolism, and viability.

Comparison of Body Temperature, Normothermia, and Extubation Times of Patients Heated with Forced Air Warming Method Based on Whether Patients Underwent On-Pump or Off-Pump Coronary Artery Bypass Graft

AIM

This study aimed to compare the body temperature, normothermia, and extubation times of patients heated with forced air warming method based on whether they underwent on-pump or off-pump coronary artery bypass graft.

METHOD

This quasi-experimental study comprised 109 patients who underwent coronary artery bypass graft operation in the cardiovascular surgery department of a university hospital and a private hospital in Afyonkarahisar. Patients were divided into the following two groups: group 1 comprised 65 patients who underwent on-pump coronary artery bypass graft and group 2 comprised 44 patients who underwent off-pump coronary artery bypass graft. All patients included in the study were heated with forced air warming method. Preoperative and postoperative data were collected using the Patient Identification Form and the Patient Tracking Form, consisting of 16 items in total. Data were analyzed using the Statistical Package for the Social Sciences 18.0 software.

RESULTS

Even though the preoperative body temperature, postoperative first body temperature, second hour body temperature, and extubation time did not exhibit a significant difference depending on the operating method, a significant difference was observed regarding the first, third, fourth, and fifth hour body temperatures and time to reach normothermia based on the operating method (p<0.05). Notably, the off-pump group's body temperatures in the first, third, fourth, and fifth hours were higher compared with the on-pump group. Furthermore, the off-pump group reached normothermia (145.22±72.54 minutes) earlier or faster compared with the on-pump group (206.84±89.30 minutes). The body temperatures, extubation times, and normothermia were not observed to exhibit significant differences based on the gender (p>0.05). A statistically significant relation was not observed between the patient's body temperature and their age (p>0.05). However, a low but positive and significant (p<0.05) correlation was observed between the extubation times (r=0.197) and age, as well as time to reach normothermia (r=0.237) and age.

CONCLUSION

This study concluded that forced air warming method is an effective technique to minimize the time to regain normothermia among patients who underwent the on- and off-pump coronary artery bypass graft.

Factors Affecting Cardiovascular Physiology in Cardiothoracic Surgery: Implications for Lumped-Parameter Modeling

Cardiothoracic surgeries are complex procedures during which the patient cardiovascular physiology is constantly changing due to various factors. Physiological changes begin with the induction of anesthesia, whose effects remain active into the postoperative period. Depending on the surgery, patients may require the use of cardiopulmonary bypass and cardioplegia, both of which affect postoperative physiology such as cardiac index and vascular resistance. Complications may arise due to adverse reactions to the surgery, causing hemodynamic instability. In response, fluid resuscitation and/or vasoactive agents with varying effects may be used in the intraoperative or postoperative periods to improve patient hemodynamics. These factors have important implications for lumped-parameter computational models which aim to assist surgical planning and medical device evaluation. Patient-specific models are typically tuned based on patient clinical data which may be asynchronously acquired through invasive techniques such as catheterization, during which the patient may be under the effects of drugs such as anesthesia. Due to the limited clinical data available and the inability to foresee short-term physiological regulation, models often retain preoperative parameters for postoperative predictions; however, without accounting for the physiologic changes that may occur during surgical procedures, the accuracy of these predictive models remains limited. Understanding and incorporating the effects of these factors in cardiovascular models will improve the model fidelity and predictive capabilities.

Dynamic Thermal Mapping of Localized Therapeutic Hypothermia in the Brain

Although whole body cooling is used widely to provide therapeutic hypothermia for the brain, there are undesirable clinical side effects. Selective brain cooling may allow for rapid and controllable neuroprotection while mitigating these undesirable side effects. We evaluated an innovative cerebrospinal fluid (CSF) cooling platform that utilizes chilled saline pumped through surgically implanted intraventricular catheters to induce hypothermia. Magnetic resonance thermal imaging of the healthy sheep brain (n = 4) at 7.0T provided dynamic temperature measurements from the whole brain. Global brain temperature was 38.5 ± 0.8°C at baseline (body temperature of 39.2 ± 0.4°C), and decreased by 3.1 ± 0.3°C over ∼30 min of cooling (p < 0.0001). Significant cooling was achieved in all defined regions across both the ipsilateral and contralateral hemispheres relative to catheter placement. On cooling cessation, global brain temperature increased by 3.1 ± 0.2°C over ∼20 min (p < 0.0001). Rapid and synchronized temperature fall/rise on cooling onset/offset was observed reproducibly with rates ranging from 0.06-0.21°C/min, where rewarming was faster than cooling (p < 0.0001) signifying the importance of thermoregulation in the brain. Although core regions (including the subcortex, midbrain, olfactory tract, temporal lobe, occipital lobe, and parahippocampal cortex) had slightly warmer (∼0.2°C) baseline temperatures, after cooling, temperatures reached the same level as the non-core regions (35.6 ± 0.2°C), indicating the cooling effectiveness of the CSF-based cooling device. In summary, CSF-based intraventricular cooling reliably reduces temperature in all identified brain regions to levels known to be neuroprotective, while maintaining overall systemic normothermia. Dynamic thermal mapping provides high spatiotemporal temperature measurements that can aid in optimizing selective neuroprotective protocols.

Endoscopic Management of Pediatric Cholesteatoma

Pediatric cholesteatoma occurs in one of two forms: congenital cholesteatoma, developing from embryonic epidermal cell rests or acquired cholesteatoma, associated with a focal defect in the tympanic membrane. This disease has been traditionally managed with the operating microscope, often requiring mastoidectomy for adequate visualization of and access to the middle ear and mastoid cavities. Recently, advances in endoscopic equipment have enabled otologists to manage most cases of pediatric cholesteatoma via a minimally-invasive, transcanal endoscopic approach. This review discusses the current literature relating to the etiopathogenesis, assessment and endoscopic management of pediatric cholesteatoma. Early outcomes of endoscopic treatment, emerging trends and technologies are also reviewed.

Lowering Perfusate Temperature From 37°C to 32°C Diminishes Function in a Porcine Model of Ex Vivo Kidney Perfusion

BACKGROUND

Ex vivo perfusion (EVP) is a novel method of preservation. However, optimal perfusion conditions remain undetermined. Reducing the temperature of the perfusate to subnormothermia may be beneficial during EVP and improve early graft function. The aim of this study was to investigate whether subnormothermia would influence the conditioning effect of EVP when compared with normothermic perfusion, and standard cold static storage (CS).

METHODS

Porcine kidneys underwent static CS for 23 hours followed by 1 hour of EVP using leukocyte-depleted blood at a mean temperature of 32°C or 37°C. After this, kidneys were reperfused with whole autologous blood at 37°C for 3 hours to assess renal function and injury. These were compared with a control group that underwent 24 hours CS.

RESULTS

During EVP, kidneys perfused at 37°C had a higher level of renal blood flow and oxygen consumption compared with EVP at 32°C (P = 0.001, 0.002). During reperfusion, 32°C EVP kidneys had lower creatinine clearance and urine output than control (P = 0.023, 0.011) and a higher fractional excretion of sodium, serum potassium, and serum aspartate transaminase than 37°C EVP kidneys (P = 0.01, 0.023, 0.009).

CONCLUSIONS

Tubular and renal functions were better preserved by a near-physiological temperature of 37°C during 1 hour of EVP, when compared to EVP at 32°C or cold storage.