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Biomedical subjects

M P Crawford

Publications and source records attributed to M P Crawford.

18 recordsLinked to original sources
PubMed1998

Sedative and analgesic effects of medetomidine in beagle dogs infected and uninfected with heartworm.

The sedative and analgesic effects of medetomidine were evaluated in heartworm-infected (HW+) and uninfected (HW-) beagle dogs by intravenous (IV) and intramuscular (IM) administration of 30 micrograms/kg and 40 micrograms/kg doses, respectively. Posture, response to noise and the pedal reflex were monitored. A procedure for mock radiographic positioning was performed to evaluate its overall clinical use. Observation times were 0, 15, 30, 60, 90, 120 and 180 min. In addition, the times from injection until the dog could not stand on its feet (down time), from lateral to sternal recumbency (sternal recumbency time), and from sternal recumbency to rising again (rising time) were also noted. Medetomidine produced rapid sedation and analgesia by both routes. Down times for the IM and IV routes were similar, which verified the manufacturer's recommended doses. The HW+ dogs had shorter down times, probably owing to increased blood flow to the brain caused by adrenergic alpha-2 activity. Sternal recumbency and rising times did not differ between the groups, suggesting a similar metabolism. Sedation and analgesia were adequate for performing the procedure in all dogs. HW- dogs showed less resistance to handling during the procedure than HW+ dogs. Overall, medetomidine seems to be a suitable agent for short-term chemical restraint in dogs, even with subclinical heartworm infestation.

Acoustic Stimulation↗
PubMed1998

Intra-articular pressure, elastance and range of motion in healthy and injured racehorse metacarpophalangeal joints.

The objective of this study was to determine if intraarticular pressure, elastance of the soft tissue forming the dorsal pouch, and range of motion in flexion measurements are significantly different in Thoroughbred metacarpophalangeal joints with clinical evidence of idiopathic synovitis, primary synovitis, synovitis/capsulitis, or osteoarthritis relative to clinically normal joints. Forty-two metacarpophalangeal joints, in 25 active or retired Thoroughbred racehorses, were categorised by palpation and visual inspection of the palmar pouch into one of 4 increasing grades of distention. Intra-articular pressures were then measured using 2 pressure transducers attached to 22-gauge needles from both the dorsal and palmar pouches simultaneously while the horses stood squarely under mild sedation. After obtaining baseline pressure measurements, a third needle was inserted into the dorsal pouch, and 0.5 ml increments of saline solution were added every 10 s to perform a pressure/volume (elastance) study of the dorsal pouch. The elastance study for each joint ended when leakage into the palmar pouch was detected by the pressure transducer placed in that region. A lateral radiographic view was taken of each metacarpophalangeal joint in maximal flexion. The maximum angle of flexion was measured from the radiograph, and this angle was subtracted from 180 degrees to acquire the range of motion in flexion. In this study, all Thoroughbreds with clinical evidence of lameness and/or sensitivity to flexion, referable to the metacarpophalangeal joint region, had fluid distention of the palmar pouch (grade 2 or 3 distention). The 16 metacarpophalangeal joints with no clinical abnormalities had a mean palmar pouch pressure of -1.25 mmHg. Joints afflicted with synovitis/capsulitis had the highest intraarticular pressures (mean +51.00 mmHg); however, joints with idiopathic synovitis (mean +15.71 mmHg), primary synovitis (mean +28.33 mmHg) and osteoarthritis (mean +26.20 mmHg) also had significantly elevated intraarticular pressures relative to the clinically normal group. Thoroughbred metacarpophalangeal joints diagnosed with synovitis/capsulitis, or osteoarthritis, had significantly increased elastance (stiffness) of the soft tissue forming the dorsal pouch relative to the normal group and, probably, as a result significantly decreased range of motion in flexion. The presence of primary synovitis alone did not have a significant immediate effect on elastance of the dorsal pouch and range of motion in flexion. The 16 Thoroughbred metacarpophalangeal joints assessed as having no clinical abnormalities had a mean range of motion in flexion of 60.81 degrees. The mean range of motion in flexion of Thoroughbred metacarpophalangeal joints with a clinical diagnosis of primary synovitis was 53.67 degrees; idiopathic synovitis 52.14 degrees; synovitis/capsulitis 44.20 degrees; and those with radiographic evidence of moderate to marked osteoarthritis 30.80 degrees. This study demonstrated that, as the severity of the clinical evidence of metacarpophalangeal joint injury/disease increased, the range of motion in flexion decreased.

Analysis of Variance↗
PubMed1995

Intra-articular pressure, elastance, and range of motion in flexion of the equine metacarpophalangeal joint.

A study was done to determine whether intra-articular pressure is increased in equine metacarpophalangeal joints with increasing degrees of synovial distention, and to correlate elastance of the soft tissue forming the dorsal pouch of the metacarpophalangeal joint to maximal range of motion in flexion. Sixty seven metacarpophalangeal joints in 36 horses were categorized by palpation and visual inspection of the palmar pouch into 1 of 4 increasing grades of distention. Intra-articular pressures were then measured, using 2 pressure transducers attached to 22 gauge needles, from the dorsal and palmar pouches simultaneously while horses stood squarely under mild sedation. Intra-articular pressure ranged from -13 to +78 mm of Hg. Mean (+/- SEM) palmar pouch pressure was subatmospheric (-2.53 +/- 2.78 mm of Hg) in joints in which the palmar pouch was not discernible (grade 0), and was markedly increased (+37.13 +/- 2.775 mm of Hg) in joints in which the palmar pouch was distended laterally beyond the lateral branch of the suspensory ligament (grade 3). Grade of distention was positively correlated with intra articular pressure (r = 0.758; P < 0.001). Significant compartmentation (P < 0.002) was observed between the dorsal and palmar pouches in all horses. In 25 of the aforementioned horses, (42 joints), which were active or retired Thoroughbred racehorses with variable degree of metacarpophalangeal joint injury/disease, a third needle was inserted into the dorsal pouch, and 0.5-ml increments of saline solution were added every 10 seconds to perform a pressure/volume (elastance) study of the dorsal pouch. The elastance study for each joint ended when leakage into the palmar pouch was detected by the pressure transducer placed in that region. A flexed lateral radio graphic view was taken of each metacarpophalangeal joint in maximal flexion. The maximal angle of flexion was measured from the radiograph, and this angle was subtracted from 180 degrees to acquire the range of motion in flexion. Range of motion in flexion has strong negative correlation (r= -0.68; P < 0.0001) with elastance (stiffness) of the dorsal pouch, and moderate pouches (r= -0.48; P < 0.0001). To adjust for the possible correlations resulting from repeated measures on limbs within horses, a normal linear mixed model was used to assess the effect of limb (right vs left), range of motion in flexion, and volume of saline solution added on the dependent variable (delta mm of Hg) in the elastance study. There was no significant limb effect, but a highly significant effect regarding volume of saline solution added (P < 0.00001) and range of motion in flexion (P < 0.00001). Loss of range of motion in flexion of this joint is associated with shortening or loss of the initial low elastance (flat) phase of the elastance profile. Measuring the elastance of the dorsal pouch or measuring maximal range of motion in flexion provides an objective measure of the degree of metacarpophalangeal joint stiffness secondary to joint disease.

Animals↗
PubMed1994

Tension development and duty cycle affect Qpeak and VO2peak in contracting muscle.

Ten canine gastrocnemius-plantaris muscle preparations were stimulated in situ to determine the interaction between tension development and the duty cycle in determining Qpeak and VO2peak. The muscle was stimulated with supramaximal voltage using four different stimulation protocols: 1) 5 twitches.s-1 (Tw), 2) 1 train.s-1-200 ms (1-200), 3) 1 train.s-1-300 ms (1-300), and 4) 2 trains.s-1-100 ms (2-100). Arterial and venous blood were sampled and Qpeak measured for determination of VO2peak. The total tension developed per second was integrated and averaged over 1 s (TDa) and used as an index of work of the muscle for each condition. The Qpeak and VO2peak were greater (P < 0.05) in the 1-200 condition compared to all other conditions. Further, Qpeak and VO2peak were greater (P < 0.05) in both the 1-300 and 2-100 conditions than during Tw: Qpeak (ml.kg-1.min-1) (mean +/- SE) for (Tw) = 928 +/- 65; (1-200) = 1368 +/- 102; (1-300) = 1150 +/- 96; (2-100) = 1189 +/- 89; VO2peak (ml.kg-1.min-1) for (Tw) = 108 +/- 8; (1-200) = 159 +/- 9; (1-300) = 135 +/- 11; (2-100) = 137 +/- 8. The TDa was significantly different among all conditions: TDa (N.kg-1) for (Tw) = 443 +/- 56; (1-200) = 606 +/- 81; (1-300) = 722 +/- 79; (2-100) = 522 +/- 41. We interpret these findings as an indication that the interaction of the duty cycle and tension development is a prime determinant of blood flow during muscle contractions.

Animals↗
PubMed1994

Cardiopulmonary effects of medetomidine in heartworm-infected and noninfected dogs.

Medetomidine, an investigational drug indicated for clinical use as a short-term chemical restraint in dogs, was evaluated for its cardiopulmonary effects, in 10 naturally heartworm-infected (HW+) and 10 noninfected (HW-) Beagles. The drug was randomly administered i.v. (30 micrograms/kg of body weight) and i.m. (40 micrograms/kg) in single injections to all dogs. Heart rate, respiratory rate, ECG, blood gas tensions, blood pH, central venous and arterial pressures were measured at 0, 15, 30, 60, 90, 120, and 180 minutes. Medetomidine induced an immediate significant (P < or = 0.001) increase in mean arterial blood pressure followed by decreased blood pressure that remained below normal throughout the study in both groups, irrespective of route of administration. Medetomidine increased central venous pressure, over time, for both groups and both routes of administration. Heart and respiratory rates were significantly (P < or = 0.001) decreased after medetomidine administration and remained reduced for the duration of the study in all dogs. The ECG variables were not significantly different between groups or between routes of administration. The HW+ dogs tended to have higher mean PaO2 than did HW- dogs at several postinjection determination times, particularly when the drug was administered i.m. The PaO2 decreased during the first 30 minutes in both groups and tended to increase gradually thereafter. The pH decreased over time for both groups and both routes. A significant (P < or = 0.05) decrease in pH was seen in the HW- dogs, compared with HW+ dogs at each measuring time for both routes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effects of reduced O2 delivery with anemia, hypoxia, or ischemia on peak VO2 and force in skeletal muscle.

This investigation was designed to describe alterations in O2 uptake (VO2) and tension development in a contracting in situ gastrocnemious-plantaris muscle preparation during three conditions of reduced O2 delivery [arterial O2 concentration X blood flow (Q)]. The three conditions, hypoxemia (H), ischemia (I), and anemia (A), were matched for O2 delivery. A normoxic normal flow condition was also utilized for comparison. H was produced by respiring the animals with 9% O2 in N2; I was produced by lowering Q, and A was produced by hemodilution with 6% dextran. The stimulation pattern for the isometric tetanic contractions used was 1 train/s, and each train was 200 ms, 70 Hz, and 6 V. The muscle was maximally contracted during each of the experimental conditions, and the conditions were administered in random order. In each bout the contractions continued for 5 min with 30 min of rest between bouts. Samples of arterial and muscle venous blood were obtained during the last 30 s of each bout. VO2 during I (125 ml.kg-1.min-1) was less than during N (145 ml.kg-1.min-1; P < 0.05) and greater than during H or A (104 and 101 ml.kg-1.min-1, respectively; P < 0.05). Venous PO2 (PVO2) was significantly lower during H (17.1 Torr) compared with the other conditions; no differences existed between N, I, and A (26.8, 26.0, and 28.1 Torr, respectively). Tension development was reduced by the reduction of O2 delivery during I, H, and A compared with N. Tension developed among the reduced O2 delivery groups was not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1986

In vitro responses of bronchial spirals and parenchymal strips from healthy and heartworm-infected dogs.

Bronchial spirals and pulmonary parenchymal strips from control (noninfected) and Dirofilaria immitis-infected dogs were tested for isometric contractile response to histamine and carbamylcholine. Responses of bronchial spirals from control dogs and from D immitis-positive groups did not differ in responses to histamine or carbamylcholine. Parenchymal strips from D immitis-positive dogs showed greater response to histamine than did those from controls; responses to carbamylcholine did not differ.

Animals↗
PubMed1985

Contractile responses to histamine of isolated pulmonary artery strips from healthy and heartworm-infected dogs.

Pulmonary artery strips from control and Dirofilaria immitis-infected dogs were tested for isometric contractile response to histamine, carbamylcholine, and norepinephrine. The strips from D immitis-positive dogs showed diminished response to histamine; a smaller percentage of the strips contracted, and the magnitude of the contraction was less than the response of the control strips to the highest concentration used. Carbamylcholine caused virtually no contractile effect in either group. Norepinephrine contracted all strips, even those not responding to histamine. A role for histamine in the pathogenesis of the pulmonary arterial lesions associated with dirofilariasis is presented.

Animals↗
PubMed1980

An assessment of the potential use of anionic dextrans as a plasma substitute.

Several problems exist when dextrans are used as plasma substitutes. High molecular weight dextrans can cause red cell aggregation and increased blood viscosity. Low molecular weight dextrans, although shown to improve circulation and promote flow, are removed rather rapidly from the circulation due to high premeation rates across capillary walls. In the present study, a small anionic charge is introduced onto the dextran to make it electrostatically negative. Since capillary walls have been shown to retain negatively charged solutes in preference to neutral solutes, the anionic dextran should retain its effectiveness for longer periods of time compared to similar sized neutral dextran. Studies were done on eight unanaesthetized dogs to compare the relative disappearance rates of dextran and anionic dextran (carboxymethyl dextran) from the circulation. It was shown that anionic dextrans do remain in the circulation over a longer period of time compared to neutral dextrans.

Animals↗
PubMedDate not supplied

The effect of epidural and general anesthesia on the healing of colonic anastomoses.

Colonic anastomoses were performed on two groups of 13 dogs each. Epidural anesthesia and general anesthesia were performed in one group and general anesthesia only in the other. Intraoperatively, the epidural-general anesthesia dogs tended to bleed less, making the anastomosis less difficult. Histologic comparisons showed healing to be more advanced in the epidural-general anesthesia dogs compared to the general anesthesia dogs 24 hours and 7 days postoperatively. Differences were not noticed 14 and 28 days postoperatively. Bursting pressures were determined 24 hours after surgery. Differences between the groups were not noticed. Leakage occurred at 72% of the pressure determined to cause leakage in normal colons.

Anastomosis, Surgical↗
PubMedDate not supplied

Esophagotomy closure in the dog. A comparison of a double-layer appositional and two single-layer appositional techniques.

Esophagotomies were performed on 36 dogs and closed with 3-0 polydioxanone in double-layer simple interrupted, single-layer simple interrupted, or single-layer simple continuous patterns. The operative time was shortest for single-layer simple continuous closure, followed by single-layer simple interrupted and double-layer simple interrupted, respectively. Three dogs with each suture pattern were euthanatized at hours 0 and 1, and days 4 and 28 after surgery. The esophagotomy incisions were subjected to bursting strength testing and examined microscopically. The bursting wall tension was higher for all three suture pattern groups at 28 days than at 0 and 1 hour. The double-layer closure had higher bursting wall tension than the single-layer closures at 0 hour and 4 days. Single-layer simple continuous closure had the lowest bursting wall tension for each time period. Single-layer simple interrupted closure had the highest bursting wall tension at 28 days. Microscopic examination revealed close approximation of tissue planes for the double-layer closure and mucosal eversion for the simple interrupted and simple continuous single-layer closures. Healing was superior histologically with the double-layer closure.

Animals↗