Patricia S. Dixon

Hydroxocobalamin and sodium thiosulfate versus sodium nitrite and sodium thiosulfate in the treatment of acute cyanide toxicity in a swine (Sus scrofa) model.

STUDY OBJECTIVEnCyanide can cause severe hypotension with acute toxicity. To our knowledge, no study has directly compared hydroxocobalamin and sodium nitrite with sodium thiosulfate in an acute cyanide toxicity model. Our objective is to compare the return to baseline of mean arterial blood pressure between 2 groups of swine with acute cyanide toxicity and treated with hydroxocobalamin with sodium thiosulfate or sodium nitrite with sodium thiosulfate.nnnMETHODSnTwenty-four swine were intubated, anesthetized, and instrumented (continuous arterial and cardiac output monitoring) and then intoxicated with a continuous cyanide infusion until severe hypotension. The animals were divided into 2 arms of 12 each and then randomly assigned to intravenous hydroxocobalamin (150 mg/kg)+sodium thiosulfate (413 mg/kg) or sodium nitrite (10 mg/kg)+sodium thiosulfate (413 mg/kg) and monitored for 40 minutes after start of antidotal infusion. Twenty animals were needed for 80% power to detect a significant difference in outcomes (alpha 0.05). Repeated measures of analysis of covariance and post hoc t test were used for determining significance.nnnRESULTSnBaseline mean weights, time to hypotension (31 minutes 3 seconds versus 28 minutes 6 seconds), and cyanide dose at hypotension (5.6 versus 5.9 mg/kg) were similar. One animal in the hydroxocobalamin group and 2 animals in the sodium nitrite group died during antidote infusion and were excluded from analysis. Hydroxocobalamin resulted in a faster return to baseline mean arterial pressure, with improvement beginning at 5 minutes and lasting through the conclusion of the study (P<.05). No statistically significant difference was detected between groups for cardiac output, pulse rate, systemic vascular resistance, or mortality at 40 minutes post intoxication. Mean cyanide blood levels (4.03 versus 4.05 microg/mL) and lactate levels (peak 7.9 versus 8.1 mmol/L) at hypotension were similar. Lactate levels (5.1 versus 4.48 mmol/L), pH (7.40 versus 7.37), and base excess (-0.75 versus 1.27) at 40 minutes were also similar.nnnCONCLUSIONnHydroxocobalamin with sodium thiosulfate led to a faster return to baseline mean arterial pressure compared with sodium nitrite with sodium thiosulfate; however, there was no difference between the antidote combinations in mortality, serum acidosis, or serum lactate.

Interleukin-6 is released in the cutaneous response to allergen challenge in atopic individuals☆

The mechanisms responsible for cutaneous response to antigen are complex. Interleukin-1 (IL-1) and interleukin-6 (IL-6) are proinflammatory cytokines that share many properties. Previous studies with a blister-chamber model have demonstrated IL-1 to be produced in the cutaneous response to antigen. Since IL-2 production by activated T cells and IL-6 production by macrophages are both stimulated by IL-1, we hypothesized that IL-2 and IL-6 may be involved in the cutaneous late-phase response (LPR) to antigen. We examined antigen-challenged sites for IL-2 immunoreactivity (ELISA) but found no difference between antigen- and diluent-challenged skin sites (N = 4). Since IL-2 has been demonstrated to be produced in response to IL-1 and IL-1 activity has been demonstrated to be greatest between hours 10 and 12, we speculated that IL-2 might not be detected until after hour 12. We were unable to demonstrate any increase in IL-2 production, even by extending our studies to 24 hours in two subjects. Antigen-challenged, skin blister-chamber fluids from atopic subjects demonstrated the appearance of IL-6 (ELISA) in pooled samples representing hours 1 1/2, 3 1/2, 5 1/2, and 7, but not at diluent control sites (p less than 0.05; N = 6). IL-6 reached a median peak of 0.66 ng/ml at 3 1/2 hours. Median levels of IL-6 fell to baseline at 8 hours, followed by a second peak of 0.25 ng/ml at hour 10. Three distinct patterns of IL-6 release were noted: early release of IL-6 followed by a sustained slower rise that peaked at hour 9 before declining to baseline levels at 12 hours, early release of IL-6 followed by a fall to baseline levels at hours 7 to 9 with a second smaller peak at hours 9 to 11, and isolated early release of IL-6. Early IL-6 production correlated with late histamine production (R = 0.801; p = 0.06), and late IL-6 production correlated with eosinophil influx (R = 0.813; p = 0.05). The area of the LPR at skin test sites correlated with early IL-6 peak levels (R = 0.977; p = 0.004) and with total early IL-6 production (R = 0.885; p = 0.05), but not with late IL-6 production.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of Human Transitional Cell Carcinoma in Vitro Proliferation by Fluoroquinolone Antibiotics

PURPOSEnThe in vitro effects of the fluoroquinolone antibiotics ciprofloxacin and ofloxacin upon 3 human transitional cell carcinoma cell lines were investigated at concentrations that are attainable in the urine of patients taking these drugs orally.nnnMATERIALS AND METHODSnCell lines TCCSUP, T24, and J82 were exposed in culture to either ciprofloxacin or ofloxacin at concentrations ranging from 0 to 800 micrograms./ml. and at durations ranging from 24 to 120 hours. Inhibition of proliferation and DNA synthesis were assessed via MTT and tritiated thymidine assays, respectively.nnnRESULTSnFrom the MTT assay ciprofloxacin, at concentrations of 25 to 800 micrograms./ml., produced proliferation inhibition in the TCCSUP line ranging from 8.1% to 90.2% at 24 hours, 25.1% to 94.9% at 72 hours, and 53.8% to 96.9% at 120 hours. Inhibition of proliferation for the T24 line ranged from 8.0% to 85%, 31.5% to 96.5%, and 27.3% to 98.2%. Inhibition of proliferation of the J82 line ranged from 20.8% to 84.8%, 22.8% to 92.7%, and 37.4% to 97.1%. Inhibition of DNA synthesis (due to ciprofloxacin at the concentrations above) as measured by the tritiated thymidine assay was also significant for each of the 3 cell lines. Inhibition of proliferation and DNA synthesis due to ofloxacin was lower but not overall statistically different from that due to ciprofloxacin. In a separate experiment, enhanced cytotoxicity was observed at lower concentrations of ciprofloxacin when the initial media pH was approximated to 5.5.nnnCONCLUSIONSnCiprofloxacin and ofloxacin inhibit proliferation and DNA synthesis of these 3 human TCC lines in vitro. Inhibition occurred in a concentration- and time-dependent manner. The concentrations that were assessed are attainable in the urine of patients taking these agents orally.

Hydroxocobalamin Versus Sodium Thiosulfate for the Treatment of Acute Cyanide Toxicity in a Swine (Sus scrofa) Model

STUDY OBJECTIVEnWe compare the efficacy of hydroxocobalamin to sodium thiosulfate to reverse the depressive effects on mean arterial pressure in a swine model of acute cyanide toxicity and gain a better understanding of the mechanism of action of the hydroxocobalamin in reversal of the toxicity.nnnMETHODSnSwine were intubated, anesthetized, and instrumented with central arterial and venous lines and a pulmonary artery catheter. Animals (n=36) were randomly assigned to one of 3 groups: hydroxocobalamin alone (150 mg/kg), sodium thiosulfate alone (413 mg/kg), or hydroxocobalamin (150 mg/kg)+sodium thiosulfate (413 mg/kg) and monitored for 60 minutes after the start of antidotal infusion. Cyanide was infused until severe hypotension developed, defined as blood pressure 50% of baseline mean arterial pressure. Repeated-measures ANOVA was used to determine statistically significant changes between groups over time.nnnRESULTSnTime to hypotension (25, 28, and 33 minutes), cyanide dose at hypotension (4.7, 5.0, and 5.6 mg/kg), and mean cyanide blood levels (3.2, 3.7, and 3.8 μg/mL) and lactate levels (7, 8.2, 8.3 and mmol/L) were similar. All 12 animals in the sodium thiosulfate group died compared with 2 of 12 in the hydroxocobalamin/sodium thiosulfate group and 1 of 12 in hydroxocobalamin group. No statistically significant differences were detected between the hydroxocobalamin and hydroxocobalamin/sodium thiosulfate groups for carbon monoxide, mean arterial pressure, cyanide levels, or mortality at 60 minutes. Lactate level (2.6 versus 2.1 mmol/L), pH (7.44 versus 7.42), and bicarbonate level (25 versus 26 mEq/L) at 60 minutes were also similar between groups.nnnCONCLUSIONnSodium thiosulfate failed to reverse cyanide-induced shock in our swine model of severe cyanide toxicity. Further, sodium thiosulfate was not found to be effective when added to hydroxocobalamin in the treatment of cyanide-induced shock. Hydroxocobalamin alone was again found to be effective for severe cyanide toxicity.

Predicting Irreparable Renal Ischemic Injury Using a Real-Time Marker in the Porcine Model

PURPOSEnWe determined the maximal renal tolerance of warm ischemia using renal cortical interstitial metabolic changes to identify a potential real-time marker of irreparable renal function.nnnMATERIALS AND METHODSnUsing a single kidney model 3 groups of 5 pigs each underwent 120, 150 and 180 minutes of warm ischemia, respectively. Microdialysis samples were collected before, during and after ischemia. Renal function assessments consisting of serum creatinine and GFR measurements were performed before ischemia and on post-ischemia days 1, 5, 9, 14 and 28. Kidneys exposed and not exposed to ischemia were collected for histological study.nnnRESULTSnInterstitial glucose and pyruvate concentrations decreased, while lactate concentrations increased to stable levels during ischemia. Glutamate spiked at 30 minutes of ischemia and subsequently tapered, while glycerol increased throughout warm ischemia time. At post-ischemia day 28 renal function returned to pre-ischemia baseline levels in the group with 120 minutes of ischemia but did not recover to baseline in the 150 and 180-minute ischemic groups. Functional data correlated with histological findings. The 120-minute maximal renal tolerance of warm ischemia correlated with a mean +/- SD glycerol concentration of 167 +/- 24 micromol/l.nnnCONCLUSIONSnInterstitial glycerol is a real-time, renal unit specific, minimally invasive marker of renal function deterioration. Exposure of porcine kidneys to ischemic insults resulting in renal cortical interstitial glycerol concentrations higher than 167 micromol/l is associated with irreparable functional damage in this model.

Hydroxocobalamin and Epinephrine Both Improve Survival in a Swine Model of Cyanide-Induced Cardiac Arrest

STUDY OBJECTIVEnTo determine whether hydroxocobalamin will improve survival compared with epinephrine and saline solution controls in a model of cyanide-induced cardiac arrest.nnnMETHODSnForty-five swine (38 to 42 kg) were tracheally intubated, anesthetized, and central venous and arterial continuous cardiovascular monitoring catheters were inserted. Potassium cyanide was infused until cardiac arrest developed, defined as mean arterial pressure less than 30 mm Hg. Animals were treated with standardized mechanical chest compressions and were randomly assigned to receive one of 3 intravenous bolus therapies: hydroxocobalamin, epinephrine, or saline solution (control). All animals were monitored for 60 minutes after cardiac arrest. Additional epinephrine infusions were used in all arms of the study after return of spontaneous circulation for systolic blood pressure less than 90 mm Hg. A sample size of 15 animals per group was determined according to a power of 80%, a survival difference of 0.5, and an α of 0.05. Repeated-measure ANOVA was used to determine statistically significant changes between groups over time.nnnRESULTSnBaseline weight, time to arrest, and cyanide dose at cardiac arrest were similar in the 3 groups. Coronary perfusion pressures with chest compressions were greater than 15 mm Hg in both treatment groups indicating sufficient compression depth. Zero of 15 (95% confidence interval [CI] 0% to 25%) animals in the control group, 11 of 15 (73%; 95% CI 48% to 90%) in the hydroxocobalamin group, and 11 of 15 (73%; 95% CI 48% to 90%) in the epinephrine group survived to the conclusion of the study (P<.001). The proportion of animals with return of spontaneous circulation at 5 minutes was 4 of 15 (27%; 95% CI 10% to 52%), and that of return of spontaneous circulation at 10 minutes was 11 of 15 (73%; 95% CI 48% to 90%) in the 2 treatment groups. Additional epinephrine infusion after return of spontaneous circulation was administered for hypotension in 2 of 11 (18%; 95% CI 4% to 48%) hydroxocobalamin animals and in 11 of 11 (100%; 95% CI 70% to 100%) of the epinephrine animals (P<.001). At 60 minutes, serum lactate was significantly lower in the hydroxocobalamin group compared with the epinephrine group (4.9 [SD 2.2] versus 12.3 [SD 2.2] mmol/L), and the pH was significantly higher (7.34 [SD 0.03] versus 7.15 [SD 0.07]). Serial blood cyanide levels in the hydroxocobalamin group were also lower than that of the epinephrine group from cardiac arrest through the conclusion of the study.nnnCONCLUSIONnIntravenous hydroxocobalamin and epinephrine both independently improved survival compared with saline solution control in our swine model of cyanide-induced cardiac arrest. Hydroxocobalamin improved mean arterial pressure and pH, decreased blood lactate and cyanide levels, and decreased the use of rescue epinephrine therapy compared with that in the epinephrine group.