The O2-sensitive brain stem, hyperoxic hyperventilation, and CNS oxygen toxicity.

Central nervous system oxygen toxicity (CNS-OT) is a complex disorder that presents, initially, as a sequence of cardio-respiratory abnormalities and nonconvulsive signs and symptoms (S/Sx) of brain stem origin that culminate in generalized seizures, loss of consciousness, and postictal cardiogenic pulmonary edema. The risk of CNS-OT and its antecedent "early toxic indications" are what limits the use of hyperbaric oxygen (HBO2) in hyperbaric and undersea medicine. The purpose of this review is to illustrate, based on animal research, how the temporal pattern of abnormal brain stem responses that precedes an "oxtox hit" provides researchers a window into the early neurological events underlying seizure genesis. Specifically, we focus on the phenomenon of hyperoxic hyperventilation, and the medullary neurons presumed to contribute in large part to this paradoxical respiratory response; neurons in the caudal Solitary complex (cSC) of the dorsomedial medulla, including putative CO2 chemoreceptor neurons. The electrophysiological and redox properties of O2-/CO2-sensitive cSC neurons identified in rat brain slice experiments are summarized. Additionally, evidence is summarized that supports the working hypothesis that seizure genesis originates in subcortical areas and involves cardio-respiratory centers and cranial nerve nuclei in the hind brain (brainstem and cerebellum) based on, respectively, the complex temporal pattern of abnormal cardio-respiratory responses and various nonconvulsive S/Sx that precede seizures during exposure to HBO2.

Exogenous ketone ester delays CNS oxygen toxicity without impairing cognitive and motor performance in male Sprague-Dawley rats.

Hyperbaric oxygen (HBO2) is breathing >1 atmosphere absolute (ATA; 101.3 kPa) O2 and is used in HBO2 therapy and undersea medicine. What limits the use of HBO2 is the risk of developing central nervous system (CNS) oxygen toxicity (CNS-OT). A promising therapy for delaying CNS-OT is ketone metabolic therapy either through diet or exogenous ketone ester (KE) supplement. Previous studies indicate that KE induces ketosis and delays the onset of CNS-OT; however, the effects of exogeneous KE on cognition and performance are understudied. Accordingly, we tested the hypothesis that oral gavage with 7.5 g/kg induces ketosis and increases the latency time to seizure (LSz) without impairing cognition and performance. A single oral dose of 7.5 g/kg KE increases systemic ß-hydroxybutyrate (BHB) levels within 0.5 h and remains elevated for 4 h. Male rats were separated into three groups: control (no gavage), water-gavage, or KE-gavage, and were subjected to behavioral testing while breathing 1 ATA (101.3 kPa) of air. Testing included the following: DigiGait (DG), light/dark (LD), open field (OF), and novel object recognition (NOR). There were no adverse effects of KE on gait or motor performance (DG), cognition (NOR), and anxiety (LD, OF). In fact, KE had an anxiolytic effect (OF, LD). The LSz during exposure to 5 ATA (506.6 kPa) O2 (≤90 min) increased 307% in KE-treated rats compared with control rats. In addition, KE prevented seizures in some animals. We conclude that 7.5 g/kg is an optimal dose of KE in the male Sprague-Dawley rat model of CNS-OT.

Seizures Caused by Exposure to Hyperbaric Oxygen in Rats Can Be Predicted by Early Changes in Electrodermal Activity.

Hyperbaric oxygen (HBO2) is breathed during undersea operations and in hyperbaric medicine. However, breathing HBO2 by divers and patients increases the risk of central nervous system oxygen toxicity (CNS-OT), which ultimately manifests as sympathetic stimulation producing tachycardia and hypertension, hyperventilation, and ultimately generalized seizures and cardiogenic pulmonary edema. In this study, we have tested the hypothesis that changes in electrodermal activity (EDA), a measure of sympathetic nervous system activation, precedes seizures in rats breathing 5 atmospheres absolute (ATA) HBO2. Radio telemetry and a rodent tether apparatus were adapted for use inside a sealed hyperbaric chamber. The tethered rat was free to move inside a ventilated animal chamber that was flushed with air or 100% O2. The animal chamber and hyperbaric chamber (air) were pressurized in parallel at ~1 atmosphere/min. EDA activity was recorded simultaneously with cortical electroencephalogram (EEG) activity, core body temperature, and ambient pressure. We have captured the dynamics of EDA using time-varying spectral analysis of raw EDA (TVSymp), previously developed as a tool for sympathetic tone assessment in humans, adjusted to detect the dynamic changes of EDA in rats that occur prior to onset of CNS-OT seizures. The results show that a significant increase in the amplitude of TVSymp values derived from EDA recordings occurs on average (±SD) 1.9 ± 1.6 min before HBO2-induced seizures. These results, if corroborated in humans, support the use of changes in TVSymp activity as an early "physio-marker" of impending and potentially fatal seizures in divers and patients.

CNS function and dysfunction during exposure to hyperbaric oxygen in operational and clinical settings.

Hyperbaric oxygen (HBO2) is breathed during hyperbaric oxygen therapy and during certain undersea pursuits in diving and submarine operations. What limits exposure to HBO2 in these situations is the acute onset of central nervous system oxygen toxicity (CNS-OT) following a latent period of safe oxygen breathing. CNS-OT presents as various non-convulsive signs and symptoms, many of which appear to be of brainstem origin involving cranial nerve nuclei and autonomic and cardiorespiratory centers, which ultimately spread to higher cortical centers and terminate as generalized tonic-clonic seizures. The initial safe latent period makes the use of HBO2 practical in hyperbaric and undersea medicine; however, the latent period is highly variable between individuals and within the same individual on different days, making it difficult to predict onset of toxic indications. Consequently, currently accepted guidelines for safe HBO2 exposure are highly conservative. This review examines the disorder of CNS-OT and summarizes current ideas on its underlying pathophysiology, including specific areas of the CNS and fundamental neural and redox signaling mechanisms that are thought to be involved in seizure genesis and propagation. In addition, conditions that accelerate the onset of seizures are discussed, as are current mitigation strategies under investigation for neuroprotection against redox stress while breathing HBO2 that extend the latent period, thus enabling safer and longer exposures for diving and medical therapies.

A Prospective Cohort Study Comparing Colorimetric and Fluorescent Imaging for Sentinel Lymph Node Mapping in Endometrial Cancer.

BACKGROUND: This prospective cohort study aimed to assess sentinel lymph node (SLN) mapping using isosulfan blue (ISB) compared with ISB plus indocyanine green (ICG) and near-infrared imaging (NIR) for patients with endometrial cancer. METHODS: In this study, 200 patients with endometrial cancer underwent SLN assessments and were randomized to ISB + ICG (n = 180) or ISB alone (n = 20). Blue dye determinations were recorded for all 200 cases followed by NIR imaging of ICG for 180 randomized subjects. All the patients underwent robotically assisted hysterectomy with pelvic ± aortic lymphadenectomy. RESULTS: The mean age of the patients was 64.5 ± 8.4 years, and the mean body mass index (BMI) was 33 ± 7.6 kg/m2. The histologies were endometrioid G1 (43%), G2 (30%), G3 (7%), and type 2 (20%). The mean time from dye injection to initiation of mapping was 13.4 ± 6.2 min, and the time to removal of SLN was 17.4 ± 11.2 min. Detection of SLN for the 20 ISB control cases did not differ from that for the 180 ISB + ICG cases (p > 0.05). The rates of SLN detection for ISB + ICG/NIR (n = 180) versus ISB (n = 200) were as follows: bilateral (83.9 vs. 40%), unilateral (12.2 vs. 36%), and none (3.9 vs. 24%) (p < 0.001). The median SLN per case was 2 (range 0-4). Positive SLNs were found in 21.1% (n = 38) of the ISB + ICG cases compared with 13.5% (n = 27) of the ISB cases (p = 0.056). The false-negative rate for SLN biopsy was 2.5% (95% confidence interval, 0.1-14.7%). In 61% (25/41) of the node-positive cases, SLN was the only positive lymph node (LN). Isolated tumor cells were found in 39.5% (15/38) of the SLN metastasis cases compared with 26.7% (4/15) of the non-SLN metastasis cases (p = 0.528). CONCLUSIONS: In this prospective study, ISB + ICG and NIR detected more SLNs and more LN metastases than ISB alone. Assessment of SLN with ICG + ISB/NIR imaging had excellent sensitivity for detection of metastasis and no safety issues.

Prognostic Significance of the Standardized Uptake Value of Pretherapeutic 18F-Labeled 2-Fluoro-2-Deoxyglucose Positron Emission Tomography/Computed Tomography in Patients With Locally Advanced Cervical Cancer.

OBJECTIVES: To determine the prognostic significance of the pretreatment and posttreatment maximum standardized uptake value (SUVmax) of F-labeled 2-fluoro-2-deoxyglucose positron emission tomography (PET)/computed tomography imaging in patients with stage IB2-IVA cervical cancer. METHODS: This was a retrospective review of cervical cancer patients with International Federation of Gynecology and Obstetrics stages IB2-IVA, from March 2008 to April 2014. All patients had pretreatment and posttreatment PET imaging and received primary whole pelvic radiation therapy with concurrent radiosensitizing chemotherapy, followed by intracavitary brachytherapy. Of the 58 patients who met the inclusion criteria, 31 patients (group A) showed no evidence of disease at last follow-up, and 27 patients (group B) presented with recurrence/persistence of disease. RESULTS: The mean pretreatment SUVmax in group A was 17.65 ± 7.82 versus 18.8 ± 7.77 in group B (P = 0.577). The mean posttreatment SUVmax between the groups was 0.85 ± 1.83 versus 6.05 ± 3.01 (P < 0.001), respectively. The mean difference between pretreatment and posttreatment SUVmax was 17.73 ± 7.50 in group A versus 13.29 ± 7.15 in group B (P = 0.045). In group A, 80.7% of patients demonstrated no posttreatment hypermetabolic activity on PET imaging versus 11.1% in group B. Of the patients who experienced treatment failure, the site of failure was pelvic in 25.9%, distant in 44.4%, and both pelvic and distant in 29.6%. CONCLUSIONS: No threshold was identified for the pretreatment SUVmax relative to the risk of recurrence. However, distinct correlations were found between the risk of recurrence, percent reduction in SUVmax, and the observation of residual hypermetabolic activity. This finding may help identify candidates for sequential chemotherapy.

Sentinel lymph node mapping with staging lymphadenectomy for patients with endometrial cancer increases the detection of metastasis.

OBJECTIVES: To compare the performance of sentinel lymph node (SLN) mapping with staging lymphadenectomy versus staging lymphadenectomy alone for the detection of metastasis and the use of adjuvant therapies in patients with endometrial cancer. METHODS: All patients with apparent early-stage endometrial cancer (n=780) who underwent robotic-assisted hysterectomy with pelvic±aortic lymphadenectomy from July-2006 to June-2013 were compared [pelvic±aortic lymphadenectomy (n=661) versus SLN-mapped cases with pelvic±aortic lymphadenectomy (n=119)]. Isosulfan-blue and indocyanine-green with near-infrared imaging were used for SLN mapping. Clinico-pathological data, FIGO stage, GOG risk category, and adjuvant therapies were compared. RESULTS: Non-mapped and mapped cases were comparable with respect to BMI, histology, depth-of-invasion, and lympho-vascular space invasion. The mapped group had more pelvic lymph node (LN) harvested compared to non-mapped group (26.4±10.5 vs. 18.8±8.5, p<0.001). Aortic LN yields were identical for both groups (9.0±5.6 vs. 9.0±6.0). The mapped group had more LN metastasis detected (30.3% vs. 14.7%, p<0.001), more stage IIIC (30.2% vs. 14.5%, p<0.001), more GOG high-risk cases (32.8% vs. 21.8%, p=0.013), and received more chemotherapy+radiation (28.6% vs. 16.3%, p<0.003). The SLN was the only metastasis in 18 (50%) mapped cases with positive nodes. The SLN false negative rate was 1/36 (2.8%). Micrometastases or isolated tumor cells were identified in 22/35 (62.9%) SLN metastases. Multivariate analysis demonstrated that SLN mapping imparted a significant effect on the detection of metastatic disease [adjusted OR=3.29, p<0.001]. CONCLUSIONS: The performance of SLN mapping with staging lymphadenectomy increased the detection of lymph node metastasis and was associated with more use of adjuvant therapies.

Cellular therapy in combination with cytokines improves survival in a xenograft mouse model of ovarian cancer.

Studies have shown enhanced survival of ovarian cancer patients in which the tumors are infiltrated with tumor infiltrating lymphocytes and natural killer cells showing the importance of immune surveillance and recognition in ovarian cancer. Therefore, in this study, we tested cellular immunotherapy and varying combinations of cytokines (IL-2 and/or pegylated-IFNα-2b) in a xenograft mouse model of ovarian cancer. SKOV3-AF2 ovarian cancer cells were injected intra-peritoneally (IP) into athymic nude mice. On day 7 post-tumor cell injection, mice were injected IP with peripheral blood mononuclear cells (PBMC; 5 × 10(6) PBMC) and cytokine combinations [IL-2 ± pegylated-IFNα-2b (IFN)]. Cytokine injections were continued weekly for IFN (12,000 U/injection) and thrice weekly for IL-2 (4000 U/injection). Mice were euthanized when they became moribund due to tumor burden at which time tumor and ascitic fluid were measured and collected. Treatment efficacy was measured by improved survival at 8 weeks and overall survival by Kaplan-Meier analysis. We observed that the mice tolerated all treatment combinations without significant weight loss or other apparent illness. Mice receiving PBMC plus IL-2 showed improved median survival (7.3 weeks) compared to mice with no treatment (4.2 weeks), IL-2 (3.5 weeks), PBMC (4.0 weeks), or PBMC plus IL-2 and IFN (4.3 weeks), although PBMC plus IL-2 was not statistically different than PBMC plus IFN (5.5 weeks, p > 0.05). We demonstrate that cytokine-stimulated cellular immune therapy with PBMC and IL-2 was well tolerated and resulted in survival advantage compared to untreated controls and other cytokine combinations in the nude-mouse model.

Robotic transperitoneal infra-renal aortic lymphadenectomy in early-stage endometrial cancer.

OBJECTIVES: To assess the clinical performance of robotic-assisted infra-renal aortic lymphadenectomy (IRL) using a single center-docked approach for patients with endometrial cancer. METHODS: Robotic-assisted hysterectomy with pelvic and aortic lymphadenectomy was performed in 97 clinical stage I endometrial cancer (EC) patients with the intent to remove infra-renal aortic lymph nodes. Peri-operative data was contemporaneously accessioned and a retrospective database analysis was performed to examine clinical outcomes. RESULTS: IRL versus infra-mesenteric artery (IMA) dissections were accomplished in 88 (90.7%) and nine (9.3%) cases, respectively. There were no laparotomy conversions. Histology included 20.6% G1, 41.2% G2, and 38.1% G3 (endometrioid and Type II histologies). Forty-four (45.4%) cases had >50% depth-of-invasion and 43 (44.3%) cases had lymphovascular space invasion. Lymph node metastases were detected in 39 (40.2%) cases [37 (38.1%) pelvic, 16 (16.5%) pelvic+aortic, two (2.1%) isolated aortic lymph nodes]. Aortic metastasis was identified in 16/37 (43.2%) pelvic node positive cases, and 6/34 (17.7%) IRL cases with positive pelvic nodes had infra-renal metastasis, yet normal aortic nodes below the IMA. Harvested aortic lymph nodes for IRL exceeded IMA cases (15.9±6.3 vs. 8.9±4.6; p<0.01). Mean BMI for IMA cases exceeded IRL cases (37.4±3.3 vs. 31.4±7.1kg/m(2); p<0.001). Twenty-five (81%) patients with BMI >35kg/m(2) underwent successful IRL (range 36-47kg/m(2)) compared to 95% of cases <35kg/m(2) (p=0.03). CONCLUSIONS: IRL was accomplished in 95% of EC patients with BMI <35kg/m(2) and 81% with BMI >35kg/m(2) using a single center-docked approach. A strict 35kg/m(2) BMI cut-off for avoiding IRL is therefore not advised.