Cardiovascular Effects of Epinephrine During Experimental Hypothermia (32°C) With Spontaneous Circulation in an Intact Porcine Model

Aims: Rewarming from accidental hypothermia and therapeutic temperature management could be complicated by cardiac dysfunction. Although pharmacologic support is often applied when rewarming these patients, updated treatment recommendations are lacking. There is an underlying deficiency of clinical and experimental data to support such interventions and this prevents the development of clinical guidelines. Accordingly, we explored the clinical effects of epinephrine during hypothermic conditions.Materials and methods: Anesthetized pigs were immersion cooled to 32°C. Predetermined variables were compared at temperature/time-point baseline, after receiving 30 ng/kg/min and 90 ng/kg/min epinephrine infusions: (1) before and during hypothermia at 32°C, and after rewarming to 38°C (n = 7) and (2) a time-matched (5 h) normothermic control group (n = 5).Results: At 32°C, both stroke volume and cardiac output were elevated after 30 ng/kg/min administration, while systemic vascular resistance was reduced after 90 ng/kg/min. Epinephrine infusion did not alter blood flow in observed organs, except small intestine flow, and global O2 extraction rate was significantly reduced in response to 90 ng/kg/min infusion. Electrocardiographic measurements were unaffected by epinephrine infusion.Conclusion: Administration of both 30 ng/kg/min and 90 ng/kg/min at 32°C had a positive inotropic effect and reduced afterload. We found no evidence of increased pro-arrhythmic activity after epinephrine infusion in hypothermic pigs. Our experiment therefore suggests that β₁-receptor stimulation with epinephrine could be a favorable strategy for providing cardiovascular support in hypothermic patients, at core temperatures >32°C.

Nearly Fatal Hydroxychloroquine Overdose Successfully Treated with Midazolam, Propofol, Sodium Bicarbonate, Norepinephrine, and Intravenous Lipid Emulsion

Background. In the context of the current COVID-19 pandemic, there has been renewed interest in the drug hydroxychloroquine. However, clinicians should be aware of the dangers of hydroxychloroquine intoxication, an insufficiently studied condition. Case Report. We present a case of autointoxication with 20 g hydroxychloroquine in a 35-year-old woman. Cardiac monitoring showed ventricular arrhythmias for which high-dose midazolam and propofol were initiated, resulting in a brief normalization of the cardiac rhythm. Because of the reoccurrence of these arrhythmias, intravenous lipid emulsion was administered with fast cardiac stabilization. Treatment with continuous norepinephrine, potassium chloride/phosphate, and sodium bicarbonate was initiated. On day 6, she was extubated and after 11 days, she was discharged from the hospital without complications. Conclusion. Since high-quality scientific evidence is lacking, treatment options are based on experience in chloroquine toxicity. Activated charcoal is advised if the patient presents early. Sedation with diazepam, early ventilation, and continuous epinephrine infusion are considered effective in treating severe intoxication. Caution is advised when substituting potassium. Despite the lack of formal evidence, sodium bicarbonate appears to be useful and safe in case of QRS widening. Intravenous lipid emulsion, with or without hemodialysis, remains controversial but appears to be safe. As a last resort, extracorporeal life support might be considered in case of persisting hemodynamic instability.

Efficacy of Low-Dose Epinephrine Continuous Infusion in Neonatal Intensive Care Unit Patients

OBJECTIVES Although epinephrine is used in the neonatal intensive care unit, few data exist on efficacy of doses <0.05 mcg/kg/min. This study evaluates the efficacy and safety of low-dose epinephrine continuous infusion at doses <0.05 mcg/kg/min in infants. METHODS Single-center, retrospective review of hypotensive infants from 2011–2018. Charts were reviewed for initial and maximum epinephrine doses, additional vasoactive agents, short-term efficacy, and adverse effects. The primary outcome was percentage of patients initiated on low-dose epinephrine whose dose did not require titration to ≥0.05 mcg/kg/min. RESULTS A total of 115 patients met study criteria with 131 distinct occurrences of low-dose epinephrine initiation. Most patients were unresponsive to other vasopressors at the time of epinephrine initiation. The median (IQR) starting dose of low-dose epinephrine was 0.01 (0.01–0.04) mcg/kg/min and median (IQR) maximum dose was 0.04 (0.02–0.08) mcg/kg/min. Fifty-five percent were responders. Patients in this cohort demonstrated significant improvement of blood pressure and urine output (p < 0.001) without adverse effects. CONCLUSIONS Low-dose epinephrine infusion may be considered as an alternative treatment to standard starting doses in hypotensive neonatal intensive care unit patients.

Adipocyte lipolysis drives acute stress-induced insulin resistance

Stress hyperglycemia and insulin resistance are evolutionarily conserved metabolic adaptations to severe injury including major trauma, burns, or hemorrhagic shock (HS). In response to injury, the neuroendocrine system increases secretion of counterregulatory hormones that promote rapid mobilization of nutrient stores, impair insulin action, and ultimately cause hyperglycemia, a condition known to impair recovery from injury in the clinical setting. We investigated the contributions of adipocyte lipolysis to the metabolic response to acute stress. Both surgical injury with HS and counterregulatory hormone (epinephrine) infusion profoundly stimulated adipocyte lipolysis and simultaneously triggered insulin resistance and hyperglycemia. When lipolysis was inhibited, the stress-induced insulin resistance and hyperglycemia were largely abolished demonstrating an essential requirement for adipocyte lipolysis in promoting stress-induced insulin resistance. Interestingly, circulating non-esterified fatty acid levels did not increase with lipolysis or correlate with insulin resistance during acute stress. Instead, we show that impaired insulin sensitivity correlated with circulating levels of the adipokine resistin in a lipolysis-dependent manner. Our findings demonstrate the central importance of adipocyte lipolysis in the metabolic response to injury. This insight suggests new approaches to prevent insulin resistance and stress hyperglycemia in trauma and surgery patients and thereby improve outcomes.

Plasma Epinephrine Contributes to the Development of Experimental Hypoglycemia-Associated Autonomic Failure

Background Recurrent hypoglycemia blunts counter-regulatory responses to subsequent hypoglycemic episodes, a syndrome known as hypoglycemia-associated autonomic failure (HAAF). Since adrenergic receptor blockade has been reported to prevent HAAF, we investigated whether the hypoglycemia-associated rise in plasma epinephrine contributes to pathophysiology and reported interindividual differences in susceptibility to HAAF. Methods To assess the role of hypoglycemia-associated epinephrine responses in the susceptibility to HAAF, 24 adult nondiabetic subjects underwent two 2-hour hyperinsulinemic hypoglycemic clamp studies (nadir 54 mg/dL; 0-2 hours and 4-6 hours) on Day 1, followed by a third identical clamp on Day 2. We challenged an additional 7 subjects with two 2-hour infusions of epinephrine (0.03 μg/kg/min; 0-2 hours and 4-6 hours) vs saline on Day 1 followed by a 200-minute stepped hypoglycemic clamp (90, 80, 70, and 60 mg/dL) on Day 2. Results Thirteen out of 24 subjects developed HAAF, defined by ≥20% reduction in average epinephrine levels during the final 30 minutes of the third compared with the first hypoglycemic episode (P < 0.001). Average epinephrine levels during the final 30 minutes of the first hypoglycemic episode were 2.3 times higher in subjects who developed HAAF compared with those who did not (P = 0.006). Compared to saline, epinephrine infusion on Day 1 reduced the epinephrine responses by 27% at the 70 and 60 mg/dL glucose steps combined (P = 0.04), with a parallel reduction in hypoglycemic symptoms (P = 0.03) on Day 2. Conclusions Increases in plasma epinephrine reproduce key features of HAAF in nondiabetic subjects. Marked interindividual variability in epinephrine responses to hypoglycemia may explain an individual’s susceptibility to developing HAAF.

A Case Report of Angioedema and Anaphylactic Shock Induced by Ingestion of Polyethylene Glycol

Introduction: We report one of few documented cases of a severe anaphylactic reaction with angioedema to polyethylene glycol (PEG). Case Report: The patient presented 30 minutes after onset of his symptoms and quickly developed hypoxia and hypotension refractory to intramuscular epinephrine, intravenous fluids, methylprednisolone, and supplemental oxygen via non-rebreather mask. He ultimately required intubation, an epinephrine infusion, and admission to the medical intensive care unit. Discussion: This case depicts a clinical reaction to PEG, a medication rarely implicated in severe anaphylaxis or angioedema. Conclusion: The allergenic potential of PEG-containing products should be raised, and providers should have a heightened awareness of these potential side effects.

Refractory Unforeseen Anaphylaxis Case in a Rural OR Unit

A 35-year-old female patient with no previously documented allergies who was admitted for elective gynaecological surgery, developed rapid onset, severe anaphylaxis, with dyspnea and cardiovascular collapse, in the operating theatre after receiving routine IV cefazolin prior to induction of anesthesia. She failed to improve with two doses of intramuscular epinephrine followed by two boluses of intravenous epinephrine, but responded to an epinephrine infusion. She was assessed by Internal Medicine and discharged home the following day. This event demonstrates the speed, severity, and profound hypotension in an allergic reaction from intravenous medication, challenges in managing anaphylaxis, and importance of prompt administration of epinephrine via IM route, followed by IV if necessary, in the OR. The case highlighted the inability to ascertain the causative agent through typical allergy testing.

VWF Exocytosis and Biogenesis of Weibel Palade Bodies in Endothelial Cells Are Differentially Controlled By Interactions between Bloc-2 and the Exocyst Complex

von Willebrand factor (vWF) is an essential plasma hemostatic factor that also participates in pathophysiologic processes such as thrombosis, angiogenesis and tumor metastasis. vWF is synthesized in endothelial cells and stored in specialized granules, Weibel-Palade bodies (WPBs), which exhibit characteristics of secretory granules termed lysosomal-related organelles (LROs). Understanding the mechanisms underlying WPB biogenesis and vWF exocytosis could enable therapeutic modulation of endogenous vWF; however, fundamental aspects of vWF trafficking mechanisms remain unknown. Since biogenesis of lysosomal related organelle 2 (BLOC-2), a complex of HPS3, HPS5 and HPS6 proteins, functions in biogenesis of other LROs such as platelet dense granules and melanosomes, we hypothesized that BLOC-2-dependent endolysosomal trafficking was essential for WPB biogenesis. BLOC-2 was depleted in human umbilical vein endothelial cells (HUVECs) by transduction of cells with lentiviral particles containing HPS6 shRNA. Evaluation of WPBs using multicolor immunofluorescence microscopy showed that the WPBs were immature, granular and abnormally localized to the perinuclear space, as compared to mature, linear-shaped WPBs, distributed peripherally in control cells (number of WPBs > 1.5 µm per cell, HPS6 3±2 vs. control 16±6). Immature WPBs in BLOC-2-depleted HUVECs lacked expression of endosome-derived cargo CD63, but not P-selectin, a synthetic cargo that enters WPBs at the trans-Golgi network. Live cell imaging showed that when BLOC-2 was depleted from HUVECs expressing CD63-GFP, CD63-GFP no longer trafficked to WPBs. Instead, endosome-derived transport tubules were mistargeted to the core of the cell. In comparison, CD63-GFP labeled WPBs intensely in control cells, where direct interaction between endosome-derived transport tubules and WPBs was evident. To identify binding partners of BLOC-2 that facilitate targeting of endosome-derived transport tubules to maturing WPBs, we performed immunoprecipitation of endogenous BLOC-2 in HUVEC lysates and evaluated the captured proteins using mass spectrometry. Several components of the exocyst complex, namely EXOC2, EXOC4 and EXO70, were enriched in BLOC-2 immunoprecipitates. This interaction was confirmed by reciprocal co-immunoprecipitation experiments with HPS6 and EXOC4. Evaluation by immunogold electron microscopy showed that EXOC4 colocalized with HPS6 in HUVECs. EXOC4 depletion using targeted siRNA resulted in WPBs that were immature, granular-appearing and perinuclearly localized, similar to BLOC-2-depleted HUVECs (number of WPBs > 1.5 µm per cell, EXOC4 3±2.5 vs. control 16±5). Overall, these observations indicate that both BLOC-2 and the exocyst complex are critical for endolysosomal trafficking involved in WPB maturation. We next evaluated the roles of BLOC-2 and the exocyst complex in vWF exocytosis. Depletion of BLOC-2 from HUVECs resulted in a 63±3% decrease in thrombin-induced vWF exocytosis and a 41±4% decrease in constitutive vWF exocytosis. Multimer analysis showed loss of high-molecular weight vWF multimers. In vivo studies showed that vWF exocytosis following systemic epinephrine infusion was 158±12% of basal levels in WT mice compared 100±20% in HPS6-/-mice, indicating lack of agonist-induced vWF release in BLOC-2 depleted mice. To evaluate the role of the exocyst complex in vWF release, both EXOC4 and EXO70 were depleted from HUVECS using siRNA. Unexpectedly, depletion of either exocyst complex component augmented thrombin-induced vWF exocytosis (EXOC4 105±21%; EXO70 99±22%). Similarly, endosidin 2, a small molecule inhibitor of EXO70, also augmented vWF exocytosis by 122±26%. These studies demonstrate that both BLOC-2 and the exocyst complex contribute to WPB biogenesis, perhaps working together based on their binding and colocalization on WBPs. However, these two complexes have opposing effects on vWF secretion. While BLOC-2 is necessary for vWF secretion, the exocyst suppresses release. Disclosures Italiano: Platelet Biogenesis: Employment, Equity Ownership; Ionis Research Funding: Research Funding. Flaumenhaft:PlateletDiagnostics: Consultancy, Other: Founder; Relay Therapeutics: Consultancy.