Hematological indices of injury to lightly oiled birds from the Deepwater Horizon oil spill.

Avian mortality events are common following large-scale oil spills. However, the sublethal effects of oil on birds exposed to light external oiling are not clearly understood. We found that American oystercatchers (area of potential impact n = 42, reference n = 21), black skimmers (area of potential impact n = 121, reference n = 88), brown pelicans (area of potential impact n = 91, reference n = 48), and great egrets (area of potential impact n = 57, reference n = 47) captured between 20 June 2010 and 23 February 2011 following the Deepwater Horizon oil spill experienced oxidative injury to erythrocytes, had decreased volume of circulating erythrocytes, and showed evidence of a regenerative hematological response in the form of increased reticulocytes compared with reference populations. Erythrocytic inclusions consistent with Heinz bodies were present almost exclusively in birds from sites impacted with oil, a finding pathognomonic for oxidative injury to erythrocytes. Average packed cell volumes were 4 to 19% lower and average reticulocyte counts were 27 to 40% higher in birds with visible external oil than birds from reference sites. These findings provide evidence that small amounts of external oil exposure are associated with hemolytic anemia. Furthermore, we found that some birds captured from the area impacted by the spill but with no visible oiling also had erythrocytic inclusion bodies, increased reticulocytes, and reduced packed cell volumes when compared with birds from reference sites. Thus, birds suffered hematologic injury despite no visible oil at the time of capture. Together, these findings suggest that adverse effects of oil spills on birds may be more widespread than estimates based on avian mortality or severe visible oiling. Environ Toxicol Chem 2018;37:451-461. © 2017 SETAC.

Weathered MC252 crude oil-induced anemia and abnormal erythroid morphology in double-crested cormorants (Phalacrocorax auritus) with light microscopic and ultrastructural description of Heinz bodies.

Injury assessment of birds following the Deepwater Horizon (DWH) oil spill in 2010 was part of the Natural Resource Damage Assessment. One reported effect was hemolytic anemia with the presence of Heinz bodies (HB) in birds, however, the role of route and magnitude of exposure to oil is unknown. The purpose of the present study was to determine if double-crested cormorants (Phalacocorax auritis; DCCO) exposed orally and dermally to artificially weathered crude oil would develop hemolytic anemia including HB and reticulocytosis. In the oral experiment, sub-adult, mixed-sex DCCOs were fed control (n = 8) or oil-injected fish with a daily target dose of 5 (n = 9) or 10 (n = 9) ml oil/kg for 21 days. Then, subadult control (n = 12) and treated (n = 13) cormorant groups of similar sex-ratio were dermally treated with approximately 13ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages approximating 20% surface coverage. Collected whole blood samples were analyzed by light (new methylene blue) and transmission electron microscopy. Both oral and dermal treatment with weathered DWH MC252 crude oil induced regenerative, but inadequately compensated, anemia due to hemolysis and hematochezia as indicated by decreased packed cell volume, relative increase in reticulocytes with lack of difference in corrected reticulocyte count, and morphologic evidence of oxidant damage at the ultrastructural level. Hemoglobin precipitation, HB formation, degenerate organelles, and systemic oxidant damage were documented. Heinz bodies were typically <2µm in length and smaller than in mammals. These oblong cytoplasmic inclusions were difficult to see upon routine blood smear evaluation and lacked the classic button appearance found in mammalian red blood cells. They could be found as light, homogeneous blue inclusions upon new methylene blue staining. Ultrastructurally, HB appeared as homogeneous, electron-dense structures within the cytosol and lacked membranous structure. Oxidant damage in avian red blood cells results in degenerate organelles and precipitated hemoglobin or HB with different morphology than that found in mammalian red blood cells. Ultrastructural evaluation is needed to definitively identify HB and damaged organelles to confirm oxidant damage. The best field technique based on the data in this study is assessment of PCV with storage of blood in glutaraldehyde for possible TEM analysis.

Clinical oxidative stress during leprosy multidrug therapy: impact of dapsone oxidation.

This study aims to assess the oxidative stress in leprosy patients under multidrug therapy (MDT; dapsone, clofazimine and rifampicin), evaluating the nitric oxide (NO) concentration, catalase (CAT) and superoxide dismutase (SOD) activities, glutathione (GSH) levels, total antioxidant capacity, lipid peroxidation, and methemoglobin formation. For this, we analyzed 23 leprosy patients and 20 healthy individuals from the Amazon region, Brazil, aged between 20 and 45 years. Blood sampling enabled the evaluation of leprosy patients prior to starting multidrug therapy (called MDT 0) and until the third month of multidrug therapy (MDT 3). With regard to dapsone (DDS) plasma levels, we showed that there was no statistical difference in drug plasma levels between multibacillary (0.518±0.029 µg/mL) and paucibacillary (0.662±0.123 µg/mL) patients. The methemoglobin levels and numbers of Heinz bodies were significantly enhanced after the third MDT-supervised dose, but this treatment did not significantly change the lipid peroxidation and NO levels in these leprosy patients. In addition, CAT activity was significantly reduced in MDT-treated leprosy patients, while GSH content was increased in these patients. However, SOD and Trolox equivalent antioxidant capacity levels were similar in patients with and without treatment. These data suggest that MDT can reduce the activity of some antioxidant enzyme and influence ROS accumulation, which may induce hematological changes, such as methemoglobinemia in patients with leprosy. We also explored some redox mechanisms associated with DDS and its main oxidative metabolite DDS-NHOH and we explored the possible binding of DDS to the active site of CYP2C19 with the aid of molecular modeling software.

Effect of vitamin C, deferoxamine, quercetin and rutin against tert-butyl hydroperoxide oxidative damage in human erythrocytes.

The mature human erythrocyte, when submitted to oxidative stress, can demonstrate depletion of reduced glutathione, oxidation of the hemoglobin molecule and aggregation of complexes of iron close to the membrane. These can produce abnormalities in the erythrocyte membrane and hemolysis. The aim of this work was to study the antioxidative action of vitamin C (vit. C), deferroxamine (DFO) and the flavonoids quercetin and rutin in normal human erythrocytes, submitted to in vitro oxidative stress induced by tert-butylhydroperoxide ((t)BHP). Venous blood was collected in citrate-phosphate-dextrose (CPD) solution, as anticoagulant, from healthy adult individuals after informed consent. The erythrocytes were resuspended in PBS to obtain 35% globular volume, and then submitted to the oxidative action of (t)BHP for up to 30 min, with or without previous incubation for 60 min with vit. C, DFO, quercetin and rutin. Decrease in the GSH concentration, G6-PD and GR activities, and increase in the methemoglobin and Heinz bodies (HB) formation, occurred with the increase in (t)BHP concentration. (t)BHP did not effect on the membrane proteins detected by SDS-PAGE. Quercetin, partially prevented the GSH decrease and the formation of HB, but did not prevent MetHb formation from oxidative damage by (t)BHP. Rutin, after (t)BHP induction, prevented the GSH decrease and the formation of HB. Vit. C, had no influence on the depletion of GSH, inhibited partially the metHb formation, and it protected GR, but not G6-PD from oxidative damage by (t)BHP. DFO partially inhibited the metHb formation and GSH decrease, but it did not protect GR and G6-PD from oxidative damage by (t)BHP. The results obtained suggest that vit. C, DFO and the flavonoids quercetin and rutin contribute to the decrease in the oxidative stress caused by (t)BHP.

Inhibition of Heinz body induction in an in vitro model and total antioxidant activity of medicinal Thai plants.

Herbs have been used for medicinal purposes for centuries and known to possess antioxidant properties that may help to reduce the risk of chronic diseases, cardiovascular disease, and cancer. We screen aqueous extracts from 20 medicinal plants in Thailand that were believed to possess anti-tumor activity, help immune-stimulating property and maintain blood stasis. The antioxidant activities were investigated in two bioassays. Firstly, we demonstrated inhibition of Heinz bodies induction caused by oxidants under in vitro condition. The percentages of Heinz body inhibition activity in plant extracts from Terminalia citrina, Cassia timoriensis, and Derris elliptica were the highest followed by Anamirta cocculus, and Oroxylum indicum respectively. In addition, we investigated total antioxidant activity in plant extracts by improved ABTS radical cation decolorization assay. The total antioxidant activity of the extract from Terminalia citrina was also the highest activity followed by Ficus pubigera, Derris elliptica, Anamirta cocculus, Caesalpinia sappan, and Oroxylum indicum respectively. Our results suggest medicinal Thai plants as valuable sources of antioxidants, which may have a potential anti-carcinogenic activity.

Repetitive propofol administration in dogs and cats.

A bolus of propofol was administered to 10 dogs (6 mg/kg intravenously [IV]) and 10 cats (10 mg/kg IV) on three consecutive days. The occurrence of apnea, heart and respiratory rates, blood pressure, time to movement, and changes in a complete blood count and biochemical profile were recorded. Apnea was not seen in the dogs but was seen in three cats. Slight increases in the number of Heinz bodies were seen in six cats, but the increases were not considered clinically significant. No apparent cumulative adverse effects were seen from a bolus of bisulfite-containing propofol, administered on three consecutive days.

Isolation and identification of sodium 2-propenyl thiosulfate from boiled garlic (Allium sativum) that oxidizes canine erythrocytes.

Sodium 2-propenyl thiosulfate was identified in boiled garlic (Allium sativum). When canine erythrocytes were incubated with sodium 2-propenyl thiosulfate, the methemoglobin concentration and Heinz body percentage in erythrocytes were both increased, indicating that the compound induced oxidative damage in canine erythrocytes. It seems that this compound is one of the causative agents of garlic-induced hemolysis in dogs.

Comparative gavage subchronic toxicity studies of o-chloroaniline and m-chloroaniline in F344 rats and B6C3F1 mice.

ortho-Chloroaniline (o-CA) andmeta-chloroaniline (m-CA) are chemical intermediates for pigment production in the textile industry. Comparative subchronic gavage studies were conducted to determine the effect of structure on toxicity.o-CA orm-CA was administered to 10 animals/sex/species in deionized water at dosages of 0, 10, 20, 40, 80, and 160 mg/kg for 13 weeks. Blood samples for clinical pathology were collected after 3 and 23 days in rats and at study termination (Day 93) in rats and mice. No mortalities occurred that could be directly attributed to treatment. Transient clinical signs of toxicity observed after dosing included cyanosis in rats and ataxia and tremors in mice. Methemoglobin formation was directly related to dosage (rats and mice) and duration of treatment (rats). At study termination, Heinz body formation in erythrocytes in association with decreased hemoglobin, hematocrit, and red blood cell count was a prominent treatment-related effect. Enlarged spleens (gross necropsy observation) and increased spleen weight were treatment effects of each chemical in both species. Microscopic lesions typical of increased red blood cell production were found in hematopoietic tissues (bone marrow, spleen, and liver), while lesions due to increased red cell destruction were found in these tissues and also the kidneys (rats). Microscopic changes were more frequently seen and severe, and involved more body organs, in rats than mice, and in m-CA-treated animals thano-CA-treated animals. Sex differences in lesion incidence/severity were not evident.

Hematological effects in F344 rats and B6C3F1 mice during the 13-week gavage toxicity study of methylene blue trihydrate.

Methylene blue trihydrate is used widely as a dye and therapeutic agent. Methylene blue was administered by gavage to 30 animals/sex/dose group in a 0.5% aqueous methylcellulose suspension at doses of 0, 25, 50, 100, and 200 mg/kg. Blood samples from 10 animals/sex/dose group were collected at the end of study weeks 1, 6, and 13. Methylene blue treatment resulted in methemoglobin formation and oxidative damage to red blood cells, leading to a regenerative anemia and a variety of tissue and biochemical changes secondary to erythrocyte injury. An early change was a dose-related increase in methemoglobin, where the response of rats and mice was similar in magnitude. Mice appeared to be more sensitive than rats to the formation of Heinz bodies and the development of anemia that was characterized by a decrease in hemoglobin, hematocrit, and erythrocyte count. Splenomegaly was apparent in all treated mice and in the 100 mg/kg (males only) and 200 mg/kg rats at necropsy. There was a dose-related increase in absolute and relative spleen weight for both species. Microscopic examination revealed increased splenic hematopoiesis in all mice treatment groups and in rats at the 50 mg/kg dose level and above. Splenic congestion and bone marrow hyperplasia were also observed in these rat-dose groups. Mice at the higher doses showed hematopoiesis in the liver and accumulation of hemosiderin in Kupffer cells. These gross and microscopic findings are consistent with the development of hemolytic anemia. A dose-related increase in the reticulocyte count during study weeks 6 and 13 suggested a compensatory response to anemia.

Antioxidant prevention of Heinz body formation and oxidative injury in cats.

OBJECTIVE: To determine the effectiveness of 3 antioxidants in preventing Heinz body anemia in cats. DESIGN: Prospective study. ANIMALS: 44 specific-pathogen-free healthy cats. PROCEDURE: Cats were housed individually, divided randomly into 4 groups, and given the following orally every 12 hours: empty gelcaps (control cats), N-acetylcysteine (NAC, 100 mg/kg of body weight), vitamin E (d,l-alpha-tocopherol; 400 IU), or ascorbate (250 mg). After 2 weeks, Heinz bodies were induced by dietary onion powder (OP; 1% or 3% of dry matter) or propylene glycol (PG, 8% wt/vol in drinking water) for an additional 3 weeks. Intake of treated water or food was recorded daily. Body weight, PCV, Heinz body and reticulocyte percentages, reduced glutathione concentration, and total antioxidant status were measured twice weekly in all cats. RESULTS: Heinz body percentage and degree of anemia did not differ significantly among cats receiving antioxidants and control cats except in cats that ingested water containing PG, in which antioxidant supplementation was associated with a decrease in water intake. Of cats that were fed a diet that contained OP, cats that received NAC had significantly higher reduced glutathione concentrations, compared with other cats in the experiment. Total antioxidant status did not consistently correlate with antioxidant supplementation or type of oxidant administered (ie, OP or PG). CONCLUSIONS AND CLINICAL RELEVANCE: Although the effect of antioxidant supplementation on Heinz body anemia in cats was minimal, antioxidants may have subclinical biochemical effects such as GSH sparing that may be important against milder forms of oxidative stress.

Hematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs.

OBJECTIVE: To determine whether dogs given garlic extract developed hemolytic anemia and to establish the hematologic characteristics induced experimentally by intragastric administration of garlic extract. ANIMALS: 8 healthy adult mixed-breed dogs. PROCEDURE: 4 dogs were given 1.25 ml of garlic extract/kg of body weight (5 g of whole garlic/kg) intragastrically once a day for 7 days. The remaining 4 control dogs received water instead of garlic extract. Complete blood counts were performed, and methemoglobin and erythrocyte-reduced glutathione concentrations, percentage of erythrocytes with Heinz bodies, and percentage of eccentrocytes were determined before and for 30 days after administration of the first dose of garlic extract. Ultrastructural analysis of eccentrocytes was performed. RESULTS: Compared with initial values, erythrocyte count, Hct, and hemoglobin concentration decreased to a minimum value on days 9 to 11 in dogs given garlic extract. Heinz body formation, an increase in erythrocyte-reduced glutathione concentration, and eccentrocytes were also detected in these dogs. However, no dog developed hemolytic anemia. CONCLUSIONS AND CLINICAL RELEVANCE: The constituents of garlic have the potential to oxidize erythrocyte membranes and hemoglobin, inducing hemolysis associated with the appearance of eccentrocytes in dogs. Thus, foods containing garlic should not be fed to dogs. Eccentrocytosis appears to be a major diagnostic feature of garlic-induced hemolysis in dogs.

Effect of a bioflavonoid dietary supplement on acetaminophen-induced oxidative injury to feline erythrocytes.

OBJECTIVE: To determine the effect of a commercial bioflavonoid antioxidant on acetaminophen-induced oxidative injury to feline erythrocytes. DESIGN: Randomized controlled study. ANIMALS: 45 healthy age-matched cats. PROCEDURE: Cats were assigned to 3 experimental groups. Groups 1 and 3 received a bioflavonoid antioxidant (10 mg/d) orally for 2 weeks. Groups 2 and 3 received an oxidative challenge with acetaminophen (90 mg/kg [41 mg/lb] of body weight, PO) on day 7. Packed cell volume, percentage of erythrocytes with Heinz bodies, blood methemoglobin concentration, and blood reduced and oxidized glutathione concentrations were determined at various times during the 2-week study period. RESULTS: Adverse effects were not associated with bioflavonoid antioxidant administration alone. Acetaminophen administration resulted in a significant increase in methemoglobin concentration in groups 2 and 3; differences were not detected between these groups. Heinz body concentrations in groups 2 and 3 increased after acetaminophen administration; however, the increase in cats that received the antioxidant was significantly less than in group-2 cats. Total blood glutathione concentrations did not change significantly in groups 2 and 3 after acetaminophen administration; however, ratio of reduced to oxidized glutathione concentration increased significantly after administration in group-2 cats, compared with group-3 cats. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of bioflavonoid antioxidants to cats at risk for oxidative stress may have a beneficial effect on their ability to resist oxidative injury to erythrocytes.

Adaptation of pregnant ewes to an exclusive onion diet.

A diet consisting entirely of cull onions fed to pregnant ewes produced Heinz body hemolytic anemia in all sheep after 21 d. After 28 d of daily consumption of 20 kg of onions/ewe, the anemia stabilized, and for the remaining 74 d the packed cell volume increased in the majority of sheep, although it did not return to normal. Compared to control ewes fed an alfalfa and grain diet, the onion-fed ewes had comparable body condition scores and fleece weights. There was no significant difference (alpha = 0.05) in pregnancy or lambing rate, number of lambs born/ewe exposed, or number of lambs born/ewe lambing. Greater numbers of sulfate-reducing bacteria (Desulfovibrio spp) and more ruminal hydrogen sulfide were present in onion-fed sheep compared to controls. Although an average 27% reduction in packed cell volume and Heinz body anemia developed in the onion-fed ewes, on the basis of this study it appears that pregnant ewes may be fed a pure onion diet with minimal detrimental effects. This adaptation to a pure onion diet is in part likely due to the apparent ability of the sheep's rumen to quickly develop a population of sulfate-reducing bacteria that decrease the toxicity of onion disulfides.

Effects of butylated hydroxyanisole and dicoumarol on the toxicity of menadione to rats.

The enzyme DT-diaphorase catalyses the 2-electron reduction of quinones. This reaction may facilitate the detoxification of such compounds, since the hydroquinone so formed can be converted into non-toxic conjugates. There is evidence for the involvement of DT-diaphorase in the detoxification of menadione (2-methyl-1,4-naphthoquinone) in a wide range of cells and tissues in vitro, but no information is available on the possible influence of this enzyme on the harmful effects of menadione in vivo. In animals, menadione is selectively toxic to erythrocytes, causing haemolytic anaemia. In the present study, rats were treated with dicoumarol, an inhibitor of DT-diaphorase, or butylated hydroxyanisole (BHA), a substance that increases the activity of this enzyme in vivo. They were then challenged with a toxic dose of menadione. Dicoumarol increased the severity of menadione-induced haemolytic anaemia while BHA decreased it, consistent with a role for DT-diaphorase in the detoxification of menadione in vivo, as previously described in vitro.

Induction of onion-induced haemolytic anaemia in dogs with sodium n-propylthiosulphate.

The haemolytic effect of sodium n-propylthiosulphate, which had been isolated from boiled onions, was studied to determine whether it could be one of the agents responsible for induced haemolytic anaemia in dogs. The oral administration of 500 mumol/kg bodyweight of the compound to dogs resulted in a haemolytic anaemia associated with an increase of Heinz body formation in erythrocytes, which was more severe in dogs with the hereditary condition which results in erythrocytes with high concentrations of reduced glutathione and potassium than in normal dogs. In the affected dogs there was a 10-fold increase in the concentration of oxidised glutathione in their erythrocytes 12 hours after the administration of the compound, whereas in normal dogs there was almost no change.

Sequence of toxic events in arsine-induced hemolysis in vitro: implications for the mechanism of toxicity in human erythrocytes.

Arsine, the hydride of arsenic (AsH3), is the most acutely toxic form of arsenic, causing rapid and severe hemolysis upon exposure. The mechanism of action is not known, and there are few detailed investigations of the toxicity in a controlled system. To examine arsine hemolysis and understand the importance of various toxic responses, human erythrocytes were incubated with arsine in vitro, and markers of toxicity were determined as a function of time. The earliest indicators of damage were changes in sodium and potassium levels. Within 5 min incubation with 1 mm arsine, the cells lost volume control, manifested by leakage of potassium, influx of sodium, and increases in hematocrit. Arsine did not, however, significantly alter ATP levels nor inhibit ATPases. These changes were followed by profound disturbances in membrane ultrastructure (examined by light and electron microscopy). By 10 min, significant numbers of damaged cells formed, and their numbers increased over time. These events preceded hemolysis, which was not significant until 30 min. It has been proposed that arsine interacts with hemoglobin to form toxic hemoglobin oxidation products, and this was also investigated as a potential cause of hemolysis. Essentially on contact with arsine, methemoglobin was formed but only reached 2-3% of the total cellular hemoglobin and remained unchanged for up to 90 min. There was no evidence that further oxidation products (hemin and Heinz bodies) were formed in this system. Based on these observations, hemolysis appears to be dependent on membrane disruption by a mechanism other than hemoglobin oxidation.

In vitro effect of ketones and hyperglycemia on feline hemoglobin oxidation and D- and L-lactate production.

OBJECTIVES: To investigate in vitro effects of ketosis and hyperglycemia on feline erythrocyte Heinz body formation, reduced glutathione (GSH) concentration, and D- and L-lactate production, and to identify potential metabolic mechanisms of oxidative stress in diabetic cats. DESIGN: Washed feline erythrocytes suspended in buffers containing normal or high glucose concentration were incubated with various concentrations of ketone bodies and tested at defined time intervals for Heinz bodies, GSH concentration, and D- and L-lactate production. ANIMALS: Three healthy female domestic cats. PROCEDURE: Erythrocytes were washed, suspended in buffers containing 5 mM glucose (simulates euglycemia) or 25 mM glucose (simulates hyperglycemia), and incubated with acetone (5 and 10 mM, acetoacetate (5 and 10 mM), or beta-hydroxybutyrate (5 and 25 mM) for 24 hours at 37 C. Aliquots were stained with new methylene blue for Heinz bodies, and assayed spectrophotometrically for GSH and D- and L-lactate concentrations. Experiments were done in triplicate. Data were analyzed, using ANOVA with repeated measures. RESULTS: Neither high glucose concentration nor ketosis had direct effects on Heinz body formation or GSH values. Glutathione decreased to 89% of initial values over the 24-hour period in all samples. High glucose concentration also had no effect on erythrocyte D-lactate production; however, the rate of D-lactate production was slightly increased in samples containing 25 mM beta-hydroxybutyrate. Linear L-lactate production confirmed metabolic viability of the erythrocyte suspensions. Samples in high glucose concentration produced L-lactate at a slightly higher (1.2x) rate than did samples in normal glucose concentration. CONCLUSIONS: High glucose concentration and ketosis do not account directly for oxidative damage and glyoxalase induction in feline erythrocytes in vitro, although high concentrations of beta-hydroxybutyrate may stimulate D-lactate formation.

Comparative toxicity of 2-hydroxy-3-alkyl-1,4-naphthoquinones in rats.

2-Hydroxy-1,4-naphthoquinone has previously been shown to cause severe haemolytic anaemia and renal tubular necrosis in animals. In order to establish if such toxic effects are common to other 2-hydroxynaphthoquinone derivatives, the short-term toxicity of a number of 2-hydroxy-3-alkyl-1,4-naphthoquinones has been compared in rats. 2-Hydroxy-3-methyl, 2-hydroxy-3-ethyl- and 2-hydroxy-3-propyl-1,4-naphthoquinone were found to cause both haemolysis and renal damage, although the severity of the changes provoked by these substances was much lower than those induced by the parent compound at an equivalent dose-level. Furthermore, the toxicity of the hydroxy-alkylnaphthoquinones decreased with increasing size of the alkyl substituent and no toxic changes were recorded in animals dosed with 2-hydroxy-3-butyl- or 2-hydroxy-3-pentyl-1,4-naphthoquinone. The relationship between the in vivo effects of these substances and previously reported data on their in vitro cytotoxicity is discussed in relation to the mechanism of toxicity of these and other naphthoquinone derivatives.

The effects of consecutive day propofol anesthesia on feline red blood cells.

This study investigated the potential for multiple exposures of propofol to induce oxidative injury, in the form of Heinz body production, to feline red blood cells. Anesthesia was induced in six healthy cats with propofol (6 mg/kg, intravenous [IV]) and maintained for 30 minutes with a propofol infusion (0.20 to 0.30 mg/kg/min, IV). The initial protocol was designed for each cat to receive 10 consecutive days of propofol anesthesia. All cats spontaneously breathed room air. Heart rate, respiratory rate, and indirect blood pressure were measured and recorded before and during anesthesia. Time to complete recovery after each infusion was measured and recorded. Heinz body analysis was performed before and after each day of propofol anesthesia. Based on predetermined criteria for discontinuing daily infusions, the mean number of consecutive days of propofol anesthesia was six and propofol administration did not continue beyond 7 days in any cat. Heart rate, respiratory rate, and indirect blood pressure did not change significantly during propofol anesthesia compared with awake values. Following the third consecutive day of propofol anesthesia, there was a significant increase from baseline in the mean percentage of Heinz bodies. Hemolysis was not detected in any cat. Recovery time significantly increased after the second consecutive day of propofol anesthesia compared with the first day. Five of six cats developed generalized malaise, anorexia, and diarrhea on day 5, 6, or 7, and two cats developed facial edema.(ABSTRACT TRUNCATED AT 250 WORDS)