Single hemorrhage: a clinically relevant canine model of hemorrhagic shock.

Clinically encountered hemorrhagic shock is usually caused by a single, rapid hemorrhage secondary to trauma. Experimental models of shock, however, have utilized anesthetic agents and hemorrhage protocols which may compromise the clinical relevance of their findings. This report characterizes the response of conscious, splenectomized dogs to a single hemorrhage of varying rates and volumes, uncomplicated by the presence of anesthetic agents. The duration of a 40 ml kg-1 hemorrhage affected the magnitude of blood pressure recovery, but did not alter the decompensating drop in blood pressure. The shortest hemorrhage duration was chosen for further study, as the blood pressure profile for this hemorrhage duration demonstrated most clearly the recovery, plateau, and decompensation phases. Increasing the hemorrhage volume to 43 ml kg-1 caused a reproducible decrease in the magnitude of the blood pressure recovery, the time to decompensation, and the time to death. Splenectomized dogs, then, demonstrate a reproducible response to a fixed-volume hemorrhage, making chronically instrumented conscious dogs a good animal model with which to study the progression of hypovolemic shock.

Serum magnesium increases following severe hemorrhage in dogs blocked by verapamil treatment.

The opening of voltage sensitive calcium channels is an important event in the progression of irreversible shock, allowing the entry of toxic amounts of calcium (Ca2+) into the cells. Because intracellular magnesium (Mg2+) can efflux through these same channels, changes in serum Mg2+ may reflect the patency of these channels. In this study, electrolytes and selected serum enzymes were monitored in chronically instrumented conscious dogs to follow the progression of shock following a fixed volume hemorrhage. Plasma enzymes indicative of liver damage were elevated only in the terminal phase of hemorrhagic decompensation. A significant increase in serum Mg2+ was evident 60 min following hemorrhage, even though arterial pressure was still recovering. Serum Mg2+ continued to rise throughout the recovery and decompensating phases of shock. Verapamil treatment, which increased survival time and survival rate, significantly attenuated the changes in serum Mg2+ which normally followed hemorrhage. These results indicate that serum Mg2+ may be a useful indicator of the severity and the progression of hemorrhagic shock.

Prevention of "irreversible" hemorrhagic shock by the preservation of cellular integrity.

The clinically encountered state of hypovolemic shock results from a series of metabolic and cardiovascular responses to tissue hypoperfusion. Recent advances have increased our understanding of the consequences of tissue hypoxia, and identified at the cellular level those changes which cause the damage to be "irreversible", or refractory to treatment. To be successful, therapeutic interventions should be designed to 1) limit, if not reverse, the subcellular alterations in membrane stability and mitochondrial function which herald the transition from compensated to decompensated shock, and 2) re-hydrate the individual to restore normal circulatory dynamics and to prevent further cellular damage. It is proposed that calcium channel blocking agents and/or high energy phosphate compounds may delay the positive feedbacks which cause irreversible tissue damage, and thus may be useful initial interventions in the treatment of hypovolemic shock.

Microbiology of the canine nasal cavities.

The microbiota of both nasal cavities were investigated in 37 dogs by both aerobic and anaerobic techniques. The predominant microorganisms were composed of enterococci and staphylococci. A surprisingly high incidence (46%) of Gram-negative rods was noted from the inferior portion of the nose. Microorganisms from the superior region of the nose, as obtained with a surgical approach, differed both qualitatively and quantitatively from the respective transnasal cultures. Thus, it appears that different bacterial populations are present within various anatomic regions of the nose and a routine transnasal culture cannot accurately reflect the microbiology of the entire nasal cavity.

Upper digestive tract burns caused by Denalan denture cleanser powder.

Denture cleansers are ubiquitous compounds frequently found in the household. Severe oral cavity burns were clinically observed in a two-year-old female who accidentally ingested a denture cleanser powder, Denalan. Experimental studies were carried out to investigate the caustic, chemical and histopathological properties of this compound. Denalan was found to be a powerful alkali agent which caused severe upper digestive tract burns.

Haemobartonella canis infection in research dogs.

During 1970-1972 haemobartonellosis occurred in research canines at 2 widely separated institutions. Clinical anemia occurred in a splenectomized dog at a Maryland facility, and subsequent screening disclosed an infection rate of 65% in a group of 20 splenectomized subjects. Treatment was successful, and the animals were used in research. A research institution in Texas encountered a number of dogs with fever (to 106 degrees F) and eosinophilia (to 42%) following minor surgery. Blood from affected animals was injected iv into splenectomized dogs, and 3 of 6 recipients developed haemobartonellosis. Further study was conducted, with some success, to establish a relationship between fever and eosinophilia and Haemobartonella canis infection in nonsplenectomized subjects. Our experiences suggest that haemobartonellosis is a widespread, latent disease of dogs and that significant potential exists for the infection to adversely affect research results.

Persistent reduction of B virus (Herpesvirus simiae) seropositivity in rhesus macaques acquired for a study of renal allograft tolerance.

One hundred and two rhesus macaques were used in a study of renal allograft tolerance. Each animal was monitored serologically more than one time to determine its B virus (Herpesvirus simiae) antibody status. The follow-up period for some individuals was 3 years, extending from 1986 to 1989. The accumulated test results eventually provided an opportunity to retrospectively support a contention that a small research colony of rhesus macaques could become and remain B virus seronegative if the animals were housed individually, monitored periodically, acquired only if they were seronegative, and culled if they converted to positive status. It was also possible that the test results might disclose useful information about the influence of acute immunosuppression on the reliability of determining B virus antibody status by serologic methods, and help formulate guidelines for selecting donor-recipient pairs. A review of the serologic test results disclosed that antibody status before the initiation of experimental therapy, and subsequent seroreactivity, did not change throughout the experimental lifetime of 92 monkeys. The few exceptions were six juveniles that lost detectable antibody, and four other juveniles that converted to positive. Preliminary data suggested that total lymphoid irradiation (TLI) and splenectomy were associated with the loss of detectable antibody; however, further study is needed to establish the validity and significance of this association. No other unexpected or unexplained results were associated with concomitant periods of acute immunosuppression. The number of seropositive animals in the colony was reduced to three through attrition and culling by the end of 1989.(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogens and progesterone during gestation in Dolichotis patagona.

During pregnancy, a progesterone-binding plasma protein is present and is similar in several respects to the binding protein reported in other hystricomorphs. These findings establish estradiol-17 beta as the predominant estrogen of pregnancy and that progesterone rises during pregnancy and does not decline until after parturition. Gestation length is 96 days. This study establishes similarities between the mara and its closest relative, the guinea pig.

The role of potassium ion in muscle glycogenolysis and glycolysis.

We have presented evidence that in an in vitro system, glycogenolysis and glycolysis function normally at potassium levels far below those observed in muscle cell water of severely deficient dogs. We suggest that a functional impairment of glycogenolysis or glycolysis is unlikely to be a mechanism by which potassium deficiency leads to rhabdomyolysis.

Hemorrhagic shock treatment with hot intravenous fluid in dogs.

In hot climates, only high temperature fluids (are greater than 100 F) may be available for treatment of blood loss shock in combat casualties. Can the hot fluid be used safely and effectively? We compared hot Ringer's lactate (51.7% C/125 F) resuscitation (n=10) to body-temperature (100 F) fluid resuscitation (n=10) in a hemorrhagic shock dog model. One liter of 125 F fluid, as part of the resuscitation, did not cause hyperthermia, red blood cell hemolysis, or any significantly different response in the cardiovascular system when compared to body-temperature fluid. All animals in both groups survived. These findings suggest that battlefield use of hot fluids in controlled amounts can be safe and effective for treatment of blood loss shock in human combat casualties.

Thigh compartment syndrome without lower extremity trauma following application of pneumatic antishock trousers.

Reported are two cases of thigh compartment syndrome following application of a pneumatic antishock trouser suit. Both patients developed compartment syndromes after prolonged antishock suit use in the absence of any apparent leg trauma. We recommend that suit compartment pressures be no more than required to restore adequate blood pressure. The duration of application should be no longer than is clinically necessary. Patients with prolonged application (greater than 120 minutes) should be closely monitored for the development of compartment syndromes.

Verapamil treatment of canine hemorrhagic shock.

The entry of calcium (Ca++) into ischemic cells is the first of a series of steps leading to irreversible cellular damage. This study examined the ability of verapamil, which may delay or diminish the injury-induced influx of Ca++, to prolong survival in three groups of chronically instrumented dogs subjected to a single, rapid hemorrhage. In untreated animals (group 1, N = 6), hemorrhage decreased mean arterial blood pressure from 101 +/- 3 mm Hg to 23 +/- 2 mm Hg. Following hemorrhage, arterial pressure recovered to 61 +/- 5 mm Hg before the secondary fall (decompensation) occurred. As decompensation progressed, arterial pressure fell to 25 mm Hg, and the animals were euthanized. In group 2 (N = 6), verapamil treatment (2 mg bolus, 1 mg/hr infusion) was initiated 30 minutes before the hemorrhage. This treatment significantly increased both the time to decompensation (184 +/- 15 minutes vs 72 +/- 9 minutes) and survival time (262 +/- 20 minutes vs 128 +/- 8 minutes). Arterial pressure recovery during the first 60 minutes following hemorrhage, however, was not affected by the verapamil pretreatment. Verapamil treatment immediately after the hemorrhage (group 3, N = 4) increased the survival rate to 75% (three of four animals). These results indicate that calcium channel blockade may be a useful initial intervention in the treatment of hemorrhagic shock.

Topical morphine in a canine model: a pilot study.

OBJECTIVE: To determine if topical morphine can enter the synovial cavity and the effect of ultrasound on this process. DESIGN: A randomized control trial to investigate which body fluids morphine enters after topical application. SETTING: A university animal laboratory. SUBJECTS: Ten mongrel dogs raised by the Comparative Medicine Department. All animals were certified to be free of disease, all had received standard scheduled immunizations, and none had been used for any other research. INTERVENTION: Topical morphine and ultrasound or topical morphine and sham ultrasound was applied to the knees of the dogs. Samples were obtained afterward from synovial fluid, serum, and urine, and were analyzed for the presence of morphine. MAIN OUTCOME MEASURES: Blood samples were collected every 60 minutes for 240 minutes, urine samples were collected at 120 minutes and 240 minutes, and synovial joint fluid was collected at 120 minutes and 240 minutes. The process of collection and analysis was the same for dogs treated with topical morphine and ultrasound and those treated with topical morphine and sham ultrasound. Fisher's exact test was used to test for an association between the use of ultrasound and the presence of morphine in the synovial fluid, serum, or urine. Two-sample t tests were used to test for group differences in mean body weight. RESULTS: All samples (synovial fluid, serum, and urine) were negative at time zero. All of the subsequent serum samples were negative for morphine. Two or three of the dogs in each group of five (ultrasound or sham ultrasound) had positive urine and synovial fluid samples at 120 and 240 minutes. Ultrasound did not affect the results. Body weight of the dogs influenced the results, with lighter animals having a significantly larger percentage (p=.03) of synovial fluid samples positive for morphine. CONCLUSION: Ultrasound did not affect the absorption of topical morphine in this canine model. Body weight may have influenced the results. Dogs that tested positive for morphine in synovial fluid had a lower mean body weight than dogs that did not test positive (p=.03).