Cardiopulmonary effects of phosphine poisoning: A preliminary evaluation of milrinone

Exposure to phosphine (PH₃) presents with a host of diverse, non-specific symptoms that span multiple organ systems and is characterized by a high mortality rate. While a comprehensive mechanism for PH₃ poisoning remains inconclusive, prior studies have implicated cardiac failure and circulatory compromise as potential pathways central to PH₃-induced mortality. In this study, milrinone (MLR), a phosphodiesterase-3 inhibitor used to treat cardiac failure, was investigated as a potential countermeasure for PH₃ poisoning. Lethality, physiological responses, and behavioral changes were evaluated in telemetrized female rats pretreated with water (sham) or one of three doses of MLR (40, 200, or 600 μg/kg) and exposed to PH₃ (660 ppm for 25-40 min; 16,500-26,400 ppm × min). Animals receiving prophylactic administration of 600 μg/kg of MLR had nominally improved survivability compared to sham animals, although median lethal concentration-time and time of death did not differ substantially between treatment groups. Changes in respiration and behavior induced by PH₃ appeared largely unaffected by MLR pretreatment, regardless of dose. Conversely, MLR pretreatment alleviated some aspects of PH₃-induced cardiac function impairment, with slight dose-dependent effects observed for cardiac contractility, mean arterial pressure, and QRS duration. Together, these results illustrate the importance of circulatory compromise in PH₃ poisoning and highlight the potential viability of MLR as a potential countermeasure option or part of a countermeasure regimen when administered prophylactically at 600 μg/kg.

Assessment of naloxone as a therapeutic for inhaled carfentanil in the ferret

Carfentanil is a powerful synthetic opioid that is approximately 100 times more potent than fentanyl and 10,000 times more potent than morphine. Carfentanil was originally intended to be used as a sedative for big game animals in a veterinary setting, but it is becoming increasingly recognized as a public health concern. We set out to investigate the effectiveness of naloxone against a potentially lethal dose of inhaled carfentanil in male ferrets. Ferrets were implanted with telemetry devices to study cardiac parameters and exposed to aerosolized carfentanil in a whole-body plethysmography chamber to record respiratory parameters. We observed profound respiratory depression in exposed animals, which led to apneic periods constituting 24-31 % of the exposure period. Concomitant with these apneic periods, we also observed cardiac abnormalities in the form of premature junctional contractions (PJCs). At our acute exposure dose, lethal in 3 % of our animals, naïve ferrets were unresponsive and incapacitated for a total of 126.1 ± 24.6 min. When administered intramuscularly at human equivalent doses (HEDs) of either 5 mg or 10 mg, naloxone significantly reduced the time that ferrets were incapacitated following exposure, although we observed no significant difference in the reduction of time that the animals were incapacitated between the treatment groups. Naloxone was able to quickly resolve the respiratory depression, significantly reducing the frequency of apneic periods in carfentanil-exposed ferrets. Our results suggest that naloxone, when administered via intramuscular injection following incapacitation, is a viable treatment against the effects of a potentially lethal dose of inhaled carfentanil.

Methylene blue and monosodium glutamate improve neurologic signs after fluoroacetate poisoning

Fluoroacetate (FA) is a tasteless, odorless, water-soluble metabolic poison with severe toxicological effects. Characterized in the mid-1900s, it has been used as a rodenticide but is comparably lethal to all mammals. Many countries have restricted its use, and modern-day accidental human exposures are rare, but recently, concerns have been raised about its application as a chemical weapon with no known antidote. A combined treatment of methylene blue (MB), an antioxidant, and monosodium glutamate (MSG), a precursor of the citric acid cycle substrate alpha-ketoglutarate, has been recommended as an effective countermeasure; however, no peer-reviewed articles documenting the efficacy of this therapy have been published. Using a rodent model, we assessed the effects of MB and MSG on the neurologic, cardiac, and pulmonary systems. Transcriptomic analysis was used to elucidate inflammatory pathway activation and guide bioassays, which revealed the advantages and disadvantages of these candidate countermeasures. Results show that MB and MSG can reduce neurologic signs observed in rats exposed to sodium FA and improve some effects of intoxication. However, while this strategy resolved some signs of intoxication, ultimately it was unable to significantly reduce lethality.

Meniscal allograft transplantation: a 1- to 5-year follow-up of 22 patients

SUMMARY

Between October 1991 and December 1995, a total of 22 patients (23 knees) underwent meniscal transplantation with nonirradiated, cryopreserved allografts. Implantation was arthroscopically assisted using bone plugs to prevent meniscal extrusion and maintain weight-bearing functional position. Patients were evaluated with an average follow-up of 40 months (range, 13 to 69 months) using the International Knee Documentation Committee, Lysholm, and Tegner scoring systems. The most significant finding was pain reduction after implantation. Lateral and standing anteroposterior radiographs were obtained on all patients at follow-up with an average joint space loss of 0.882 mm (range, 0 to 3 mm). Magnetic resonance imaging was preformed on both knees in 12 of the 22 patients at an average of 24.4 months postoperatively. On average, the allograft meniscus was 63% (range, 31% to 100%) the size of the normal meniscus. Clinical results showed improvement of preoperative pain in all patients. Although patients continue to have good pain relief following their meniscal allograft transplantation, the average shrinkage in the size of the meniscus as shown on magnetic resonance imaging is a concern.

Early season anterior cruciate ligament tears. A treatment dilemma

An anterior cruciate ligament tear before or early in an athlete's season presents a treatment dilemma: surgically repair the ligament and end the season, or use rehabilitative exercises and bracing to quickly return the athlete to play. We conducted a prospective study of 43 athletes (44 acute tears) over 44 months to determine criteria for early return to play and if an early return is safe. All patients had an acute injury in a previously normal knee, a positive Lachman test, and KT-1000 arthrometry indicating ligament abnormalities. Magnetic resonance imaging of each injured knee showed an interior cruciate ligament tear but no meniscal tear. Thirty patients (31 tears) returned to play with rehabilitation and a brace at an average of 5.7 weeks after injury: Only 12 patients returned to their sports without recurrent buckling of their injured knees; 18 patients (19 knees) had recurrent buckling during play. Thirteen patients could not return to play. Patients were observed until they 1) had ligament reconstruction (29 patients, 29 tears), 2) gave up their sports because of instability but did not elect surgery (3 patients), or 3) returned to play in a brace and declined surgery (11 patients, 12 tears). All who elected reconstruction experienced recurrent knee buckling. We found 23 meniscal tears (17 knees) in the 29 patients undergoing reconstruction.

Effect of topically applied anti-CD4 monoclonal antibodies on orthotopic corneal allografts in a rat model

PURPOSE

Monoclonal antibodies (mAb) have generated interest as therapeutic agents. Limited data are available on the treatment of corneal graft rejection. The purpose of this study was to assess the use of topically applied mAb on experimental corneal grafts.

METHODS

W 3/25, an IgG 1 mouse antirat mAb that recognizes a CD4+ cell subset, was used to treat Lewis recipient rats that received orthotopic corneal grafts of Wistar-Furth donors. Recipients were randomly assigned to receive topically applied drops of liposome-incorporated anti-CD4 mAb (LIP-anti-CD4 mAb), an equivalent amount of free anti-CD4 mAb, an isotype-matched control mAb encapsulated in liposomes (LIP-control mAb), or empty liposomes (emp-LIP) 5 times daily for 10 days. To investigate the immunologic effect of mAb treatment, flow cytometry of the targeted cells and cytotoxic activity of lymphocytes were analyzed.

RESULTS

Application of LIP-anti-CD4 mAb was effective in reducing the rejection rate (P < .05) and in prolonging the mean survival time of corneal grafts that underwent rejection (P < .05). In contrast, no significant effect on graft outcome was observed after the application of control agents. Flow cytometry analysis did not reveal systemic depletion of the targeted lymphocyte subset in any anti-CD4 mAb treated animals. Rejected grafts elicited a cellular cytotoxic immune response in a cell-mediated lymphocytotoxic assay independent of the treatment given.

CONCLUSION

The results suggest that treatment with topically applied LIP-anti-CD4 mAb prolongs graft survival in orthotopic corneal grafts in a rat model. The beneficial effect of LIP-anti-CD4 mAb, probably due to enhanced intraocular delivery, was achieved by using relatively low doses of mAb.

Prolongation of corneal allograft survival with liposome-encapsulated cyclosporine in the rat eye

PURPOSE

To study the effects of different formulations of topical cyclosporine (Cyclosporin A [CsA]) on corneal allograft rejection in a rat model.

METHODS

Female Lewis rats received penetrating keratoplasties from female Wistar-Furth donors. A total of 78 allogeneic grafts were performed. An additional 15 syngeneic grafts (Lewis) were used as technical controls. Two CsA preparations with equivalent drug concentrations (2.1 mg/ml) were applied as drops: CsA encapsulated in large unilamellar liposomes (CsA-LIP) and CsA dissolved in olive oil (CsA-DR). Allogeneic grafts were randomly assigned to receive CsA-LIP or CsA-DR beginning on the day of surgery five times daily for 10 days. Animals without any treatment or receiving empty liposomes (EM-LIP) were used as treatment controls. Grafts were graded three times weekly and a rejection index was generated based on graft clarity, neovascularization, and vessel size.

RESULTS

All syngeneic grafts remained clear over the observation period of 60 days. Rejected allogeneic grafts without any treatment and those receiving EM-LIP or CsA-DR showed a mean survival time (+/- standard deviation) of 14 +/- 4, 14 +/- 5, and 14 +/- 4 days, respectively. There was no significant difference in mean survival time between the grafts without any treatment and those in CsA-DR or EM-LIP treatment groups. The mean survival time of rejected grafts in animals receiving CsA-LIP was prolonged to 20 +/- 4 days. There was a significant difference in the mean survival time between the CsA-LIP treatment group and groups receiving CsA-DR, EM-LIP, or no treatment (P < or = 0.05). The Kaplan-Meier survival curve of the CsA-LIP treatment group was significantly different from the other experimental groups. The graft survival rate in the CsA-LIP group was 77%, whereas the rate was 37% in the non-treated group, 45% in the CsA-DR group, and 36% in the EM-LIP group.

CONCLUSION

Encapsulation of CsA in liposomes might be a promising formulation for use in the prevention of corneal graft rejection.