Clinical evaluation of the sedative, antinociceptive and cardiorespiratory effects of intranasal dexmedetomidine combined with methadone in healthy dogs

In this prospective, randomised, blinded clinical study, we compared the sedative, antinociceptive and cardiorespiratory effects of intranasal (IN) dexmedetomidine at 5 μg/kg (diluted with 0.03 mL/kg NaCl 0.9%, DEX) with or without methadone (0.3 mg/kg; DEXMET), through a mucosal atomization device to one nostril in twenty healthy client-owned dogs. At 5-min intervals over 45 min, sedation score, onset, cardiopulmonary variables, mechanical nociceptive thresholds (MNTs) were assessed, also ease of administration, adverse effects, and response to IV catheterization. Statistical analysis employed t-test, the Mann-Whitney U, repeated measures ANOVA and Chi-square tests as appropriate (P < 0.05). Higher sedation ocurred in DEXMET (7 [5-10]) compared to DEX (5 [2-7]) from 15 to 30 min (P < 0.01, median [interquartile range]). Heart rate was lower in DEXMET (P < 0.01; 65% reduction vs. 41% in DEX, P = 0.001). The MNTs were higher in DEXMET than DEX from 15 to 45 min (P < 0.01), peaking at T30 (17.1 ± 3.8, DEXMET and 8.5 ± 5.4 N, DEX). No differences were observed in mean arterial blood pressure and respiratory rate. Intranasal administration was considered easy for 8 dogs per group. Reverse sneezing (8 dogs; P < 0.001), sialorrhea and retching (4 and 2 dogs, respectively) occurred in DEXMET. Response to catheterisation was lower in DEXMET than DEX (P = 0.039; 2 and 7 dogs, respectively). In conclusion, intranasal methadone (0.3 mg/kg) increased the sedative and antinociceptive effects produced by dexmedetomidine (5 μg/kg) in healthy dogs and resulted in lower heart rate.

Anaesthetic effects in the ferret of alfaxalone alone and in combination with medetomidine or tramadol: a pilot study

Alfaxalone is a neurosteroid with anaesthetic effects and it has been used successfully in several animal species. However, there are no data, to our knowledge, about its efficacy and safety in ferrets ( Mustela putorius furo). We evaluated a variety of anaesthetic regimens in ferrets, namely, alfaxalone at 20, 10 and 5 mg/kg ( n = 1, 10 and 9, respectively; intravenously); medetomidine at 20 µg/kg ( n = 3; intramuscularly); medetomidine (20 µg/kg, intramuscularly) plus alfaxalone (2.5 mg/kg, intravenously; n = 7); and tramadol (5 mg/kg, intramuscularly) plus alfaxalone (5 mg/kg, intravenously; n = 2). Two animals treated with alfaxalone at 10 mg/kg and 20 mg/kg, respectively, died. At 5 mg/kg alfaxalone produced anaesthesia with a similar onset but a shorter duration of anaesthesia and analgesia than alfaxalone at 10 mg/kg. The medetomidine–alfaxalone combination produced anaesthesia and analgesia of a longer duration than alfaxalone administered alone at 5 mg/kg ( P < 0.0001 and P < 0.001, respectively). Under this anaesthetic regimen, there was a progressive decrease in pulse rate during the first 30 min before the pulse rate stabilized. Respiratory parameters were maintained at acceptable levels. When tramadol was administered, all the animals exhibited a strong excitation reaction and in no case was the toe-pinch reflex clearly abolished. Thus, alfaxalone plus medetomidine provided safe and effective anaesthesia in ferrets. Alfaxalone, alone or in combination with tramadol, did not produce satisfactory results for use as an anaesthetic for this species.

Effects of fluid load on cardiovascular function during stepwise lung recruitment manoeuvre in healthy dogs

The aim of this study was to evaluate the effects of a stepwise lung recruitment manoeuvre (RM) on cardiac output (CO) in mechanically ventilated dogs, with or without a previous fluid load. Eight healthy adult Beagle dogs were enrolled in a prospective crossover study. Following sedation with dexmedetomidine and methadone, anaesthesia was induced with propofol and maintained with isoflurane. CO (thermodilution method) and direct arterial blood pressure were monitored. The dogs were mechanically ventilated in a volume-controlled mode (tidal volume, VT = 10 mL/kg; positive end-expiratory pressure [PEEP] = 0 cm H2O) until normocapnia was achieved (end tidal CO2 35-45 mmHg). The RM was then performed in a pressure-controlled mode, with progressive increases of the PEEP and end-inspiratory pressure of 5 cm H2O, until 15 cm H2O and 30 cm H2O were reached, respectively. After the RM, the ventilatory mode was returned to volume-control, and the PEEP was sequentially decreased to 10, 5 and 0 cm H2O. Baseline ventilation was maintained for 30 min. Next, 10 mL/kg of lactated Ringer's solution was administered within 10 min, prior to a second RM. The CO was determined before each RM (baseline) and at each pressure step. A repeated measures ANOVA test was used to compare data. Compared to baseline, CO decreased during the RM in both groups. However, there was a significantly higher CO during the second RM at the highest pressure step (P<0.05) and during all decreasing pressure steps (P<0.05). In conclusion, a previous crystalloid fluid load could reduce the impact of a RM on CO in healthy dogs.

Anaesthetic and cardiorespiratory effects of a constant-rate infusion of alfaxalone in desflurane-anaesthetised sheep

A prospective, randomised, blinded controlled study was performed to determine the anaesthetic and cardiorespiratory effects of a constant-rate infusion (CRI) of alfaxalone in 12 sheep anaesthetised with desflurane, and undergoing experimental orthopaedic surgery. Sheep were sedated with dexmedetomidine (4 μg/kg, intravenously) and butorphanol (0.3 mg/kg, intravenously). Anaesthesia was induced with alfaxalone (1 mg/kg/minute to effect, intravenously) and maintained with desflurane in oxygen and alfaxalone 0.07 mg/kg/minute or saline for 150 minutes (range 150-166 minutes). The anaesthetic induction dose of alfaxalone, the desflurane expiratory fraction required for anaesthetic maintenance, cardiorespiratory measurements and blood-gases were recorded at predetermined intervals. Quality of sedation, anaesthetic induction and recovery were assessed. The alfaxalone induction dose was 1.7 mg/kg (1.2 to 2.6 mg/kg). The desflurane expiratory fraction was lower (22 per cent) in sheep receiving alfaxalone CRI (P=0). Also, heart rate (P=0), cardiac index (P=0.002), stroke index (P=0) and contractility (P=0) were higher, and systemic vascular resistance (P=0.002) was lower. Although respiratory rate tended to be higher with alfaxalone, there was no difference in PCO2 between the groups. Recovery times were significantly longer in sheep given alfaxalone (25.4 v 9.5 minutes) but recovery quality was similar. Alfaxalone reduced requirements of desflurane and maintained similar cardiorespiratory function, but recovery time was more prolonged.

Gait analysis using 3D accelerometry in horses sedated with xylazine

The aim of the present study was to verify the efficacy and sensitivity of an accelerometric device in detecting and quantifying the degree of movement alteration produced in horses sedated with xylazine. Horses (n=6) were randomly administered either xylazine or a control by intravenous injection, with at least 1 week between each treatment. A triaxial accelerometric device was used for the accelerometric gait assessment 15 min before (baseline) and 5, 15, 30, 45, 60, 75, 90, 105 and 120 min after each treatment. Eight different accelerometric parameters were calculated, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsion power, mediolateral power and total power, with the force of acceleration and the dorsoventral, mediolateral and craniocaudal (propulsive) parts of the power then calculated. Administration of xylazine decreased many of the parameters investigated, with significant differences for speed, stride frequency, dorsoventral power, propulsion power and total power at 5, 15, 30 and 45 min after injection. There were no significant differences in stride length values at any time point. Decreases in regularity values were evident with significant differences at every time point from 5 to 120 min following xylazine injection. Force values were also significantly reduced from 5 to 30 min after treatment and a redistribution of the total power was observed 5 min after injection as the mediolateral power increased significantly, while the dorsoventral power decreased. Accelerometry offers a practical, accurate, easy to use, portable and low cost method of objectively monitoring gait abnormalities at the walk in horses after sedation with xylazine.

Determination of the minimum alveolar concentration for halothane, isoflurane and sevoflurane in the gerbil

The present work determined the minimum alveolar concentrations (MAC) of halothane, isoflurane and sevoflurane in adult female gerbils (n=24). Animals were placed in a chamber for anaesthetic induction before performing tracheal intubation. The tracheal tube was connected to a non-rebreathing circuit with minimal dead space. Body temperature, blood pressure, heart and respiratory rates and end-tidal volatile anaesthetic levels were measured continuously. MAC was determined using a standard noxious stimulus (tail-clamp). All experiments were performed at the same time of the day, body temperature was maintained constant and blood-gas analysis was performed to confirm that values were within normal limits. The mean+/-SD MAC values were 1.06+/-0.11% halothane (n=8), 1.55+/-0.08% isoflurane (n=8) and 2.90+/-0.12% sevoflurane (n=7). Cardiovascular parameters at 1xMAC did not differ significantly among anaesthetics but the respiratory rate was significantly higher in the halothane group than in the isoflurane and sevoflurane groups. The SpO2 values recorded throughout anaesthesia and the pH and partial oxygen pressure values determined at the end of the study did not differ among the studied anaesthetics at 1xMAC. These data suggest that the MAC for halogenated inhalant anaesthetics in gerbils is lower than the average MAC values obtained in rats and mice.

Direct activation of telomerase by GH via phosphatidylinositol 3'-kinase

Telomerase is a ribonucleoprotein DNA polymerase that has been associated with cell proliferation, cell survival and apoptosis inhibition. Telomerase is regulated by specific growth factors, cytokines and hormones. The present study examines the effect of GH on telomerase activity and identifies the signal transduction pathway involved in this process in Chinese hamster ovary (CHO)4 cells, which express rat GH receptor cDNA. Telomeric repeat amplification protocol assays demonstrated that treating CHO4 cells with increasingly high doses of GH up-regulated telomerase activity with the maximum activation at 24 h. Similarly, GH activated telomerase in another cell system, primary cultures of rat hepatocytes. The telomerase activation in CHO4 cells was produced with an increase in hamster telomerase catalytic subunit (hamTERT) mRNA expression. The telomerase activity induced by GH was specifically blocked by the phosphatidylinositol 3'-kinase (PI3-K) inhibitor, LY294002, but not by the MAP kinase kinase inhibitor, PD98059. These findings suggest that GH could activate telomerase through the direct activation of TERT transcription, as well as through the PI3-K signalling pathway.

Growth hormone effects in intestinal adaptation after massive bowel resection in the suckling rat

BACKGROUND

Massive small bowel resection provokes intestinal malabsorption that leads to diminished growth in the suckling rat. Growth hormone is one of the several factors that can enhance the adaptive response of the intestines in the adult rat; however, whether it also enhances postresection intestinal adaptation in the suckling rat, thus reducing the adverse effects of resection on growth, is still unclear.

METHODS

Seventy-four 30-day-old suckling Wistar rats underwent 80% midgut bowel resection, laparotomy (sham operation), or no surgery. They were treated with either growth hormone or saline for 15 days and studied 15 or 45 days after surgery. Body weight was monitored and samples of bone and intestinal mucosa were obtained at the end of the study period for analysis.

RESULTS

Resected rats lost body and bone weight regardless of growth hormone administration. Bowel resection provoked significant increases in the proliferation and size of the intestinal mucosa. Growth hormone significantly, but just barely, increased crypt height and mucosal mass at day 15 after surgery, but not at day 45. Lengthening of the intestines was the main effect of growth hormone.

CONCLUSIONS

The relatively small adaptive response of intestines to growth hormone is insufficient to promote body growth after intestinal resection in the suckling rat. This response is lower than that in older rats and may reflect an age-related differential response to growth hormone.

Somatostatin antagonism prevents elemental diet-induced intestinal atrophy in the rat

Somatostatin is a peptide with known antiproliferative effects on the intestine. The aim of the present work was to determine whether somatostatin (SST) antagonism reduces elemental diet-induced intestinal atrophy in the rat. Male Wistar rats were fed a standard diet and treated for seven days with either continuous infusion of saline or low and high doses of a putative somatostatin antagonist; another group was given a SST antagonist in a pulsatile high dose. All these groups received an elemental diet to induce gut mucosa atrophy. Rats were killed and samples were obtained for morphometric and proliferative measurements of the intestine and for SST and insulin-like growth factor-1 (IGF-1) level determination. The elemental diet decreased mucosal length and proliferation. Pulsatile administration of SST antagonist improved or prevented both effects, whereas continuous SST antagonist delivery prevented decreased crypt proliferation induced by the elemental diet. Somatostatin plasma levels were lowest in rats receiving pulsatile administration of SST antagonist. In conclusion, somatostatin antagonism increases proliferation in the intestinal mucosa, improving elemental diet-induced intestinal atrophy; however, morphological growth is not affected.

Somatostatin blockade improves the proliferative response but not intestinal morphological growth after small bowel resection in rats

OBJECTIVE

To find out whether or not blockade of somatostatin improves intestinal adaptation after small bowel resection.

DESIGN

Laboratory experiment.

SETTING

Teaching hospital, Spain.

SUBJECTS

Eighty adult Wistar rats.

INTERVENTIONS

Animals underwent intestinal resection or sham operation (n = 40 each) and were treated with a somatostatin antagonist either intermittently or continuously in three different doses (n = 8 each).

MAIN OUTCOME MEASURES

Bowel mucosal thickness, proliferation and concentrations of cAMP, somatostatin, insulin-like growth factor 1.

RESULTS

Intestinal resection induced a proliferative and morphometric increase of the mucosa; however, the antagonist increased proliferation only in those animals given the highest dose. Intermittent doses induced a proliferative effect that was stronger than that in the three continuous groups. There was no relationship between trophic stimulus and insulin-like growth factor 1 or cAMP, but somatostatin concentrations increased after the intermittent course.

CONCLUSIONS

Somatostatin receptor blockade with an antagonist does not cause in normal rats an intestinal morphological adaptation process or increase it after resection; however, it did promote a proliferative stimulus in the crypts.

Antinociceptive and motor-blocking action of epidurally administered IQB-9302 and bupivacaine in the dog

BACKGROUND AND OBJECTIVES

The aim of this study was to compare the antinociceptive and motor-blocking effects of epidurally administered IQB-9302 (C18H26N2O.HCl) and bupivacaine in the dog.

METHODS

Twelve adult female Beagle dogs were used. Each animal received 3 concentrations (0.25%, 0.50%, and 0.75%) of either IQB-9302 (n = 6) or bupivacaine (n = 6) by means of a chronic epidural catheter. The nocifensive and motor-blocking status were determined at regular intervals before (baseline) and after drug administration.

RESULTS

Epidurally administered IQB-9302 caused a more potent nocifensive and motor-blocking action than bupivacaine. The duration of complete nocifensive block was the longest with IQB-9302, whereas the duration of dermatome nocifensive block was similar for both drugs. The nocifensive to motor block ratio was significantly higher with IQB-9302.

CONCLUSIONS

IQB-9302 produced an anesthetic action similar to that of bupivacaine, although the former drug induced a slightly more potent nocifensive block. Nocifensive and motor block duration are very similar with IQB-9302, whereas bupivacaine induces a more prolonged motor block without nocifensive block.

Reduction of isoflurane MAC with buprenorphine and morphine in rats

Preoperative analgesics are being increasingly used to provide analgesia in the intraoperative and postoperative period. Opioids reduce anaesthetic requirements, although the effect varies with the different drug and species. The aim of this work was to determine whether buprenorphine reduces the minimum alveolar concentration (MAC) of isoflurane in a dose-related fashion, and whether this effect is similar to morphine when clinical doses of both drugs are used in the rat. Thirty-six male Wistar rats were anaesthetized with isoflurane, and MAC was determined before and after the administration of either buprenorphine or morphine. MAC of isoflurane was determined from alveolar gas samples when a standard noxious stimulus, in the form of a tail clamp, was applied. The duration and degree of reduction of the MAC of isoflurane were recorded. Basic cardiovascular and respiratory measurements were also recorded. Buprenorphine (10, 30 and 100 microg/kg) and morphine (1, 3 and 10 mg/kg) reduced in a dose-dependent fashion the MAC of isoflurane by 15%, 30% and 50%, respectively. Buprenorphine resulted in less cardiovascular and respiratory depression and had a longer-lasting action than morphine. In conclusion, buprenorphine has a dose-related isoflurane sparing effect in the rat similar to that caused by morphine at clinical doses of both drugs.

Effect of four enteral foods on the small bowel of undernourished rats after midgut resection

OBJECTIVE

To describe the effects of new enteral foods on the adaptation of the gut mucosa after massive intestinal resection in rats.

DESIGN

Laboratory experiment.

SETTING

Teaching hospital, Spain.

SUBJECTS

91 male Wistar rats, 69 of which were studied (5 were excluded and 17 died).

INTERVENTIONS

Previously undernourished rats were subjected to either massive bowel resection (n = 30) or laparotomy (n = 26) and fed four enteral hypocaloric diets for 7 days: Alitraq (n = 7 in each group), Impact (n = 8 and 7), Enrich (n = 8 and 6), and Elemental (n = 7 and 6). The remainder were not operated on and fed chow (n = 7) or a diet containing no protein (n = 6). Two diets were high in protein (Alitraq and Impact) and two contained normal amounts (Enrich and Elemental).

MAIN OUTCOME MEASURES

Bowel mucosal thickness and proliferation; disaccharidase activity; intestinal weight and length; body weight; and plasma somatostatin, IGF-1, and peptide YY concentrations.

RESULTS

Enriched diets provided a higher body and intestinal weight, and increased length of jejunal and ileal villous size. Peptide concentrations were modified by resection but not by the diet given. Concentrations of somatostatin and insulin-like growth factor were reduced in all groups with the exception of somatostatin in the two diets high in protein in the sham-operated rats.

CONCLUSIONS

Enriched diets all improve the intestinal adaptive response to massive bowel resection in rats, offering advantages over diets with normal amounts of protein.

Comparative effect of growth hormone and plerocercoid growth factor in the intestinal resection in rat

OBJECTIVE

After massive bowel resection, absorption depends on how fast the mucosal adaptation takes place. This work aims at assessing the trophic effect of growth hormone (GH) and its analogue, the plerocercoid growth factor (PGF), on the intestinal mucosa after 90% small bowel resection.

EXPERIMENTAL DESIGN

24 male Wistar rats were divided into four groups of 6: Control (laparotomy), 90% small bowel resection (RID), resection and treatment with GH during 14 days (RID + GH) and resection and PGF treatment (RID + PGF). Intestinal mucosal adaptation was assessed by measuring mucosal weight and height, and evaluating the regenerative activity by measuring proliferation cell nuclear antigen (PCNA) labelling index.

RESULTS

Bowel resection itself caused a significant increment of jejunal and ileal mucosal height in comparison with the control group. GH and PGF did not change this increase. Jejunal and ileal proliferation indexes were significantly higher than those in controls and they were significantly higher in both RID + GH and RID + PGF groups.

CONCLUSIONS

GH and PGF cause a proliferative effect on the intestinal mucosa, even in hyperproliferative states such as the small bowel resection. This finding might have a clinic application.

Epidural injection of ketamine for perineal analgesia in the horse

OBJECTIVE

To determine the analgesic, sedative, and cardiopulmonary effects of epidural ketamine in the horse.

ANIMAL POPULATION

Six healthy horses (three males and three females) weighing between 350 and 450 kg.

METHODS

Three doses of ketamine were selected (0.5, 1, 2 mg/kg). Two months before the beginning of experiments, the carotid artery was exteriorized, and 1 week before experiments began, an epidural catheter was placed percutaneously in all animals with the tip located 12 cm cranially in the midsacrum. One week later, either saline (control) or one of three doses of ketamine was injected epidurally. Each animal received each ketamine dose and saline in random order at 1-week intervals. Ketamine was diluted in saline 0.9% before the experiment, and the volume used was adjusted to horse size and correlated to clinically used volumes. All the animals received a standard noxious stimulus consisting of needle insertion into the skin and deep muscle using a 3-point scale for scoring the response. A second scale was used to score the degree of sedation. The response to a noxious stimulus, the degree of sedation, and arterial blood pressure were assessed at previously determined intervals: before drug and 2, 5, 10, and 15 minutes and every 15 minutes to 210 minutes after ketamine or saline administration. Arterial blood samples were drawn for blood gas analysis before drug and at 15, 30, 60, and 90 minutes.

RESULTS

All the tested doses of ketamine were effective in producing analgesia of the tail, perineum, and upper hindlimb. Total tail and perineal analgesia times were similar depending on dosage (30 minutes for 0.5 and 1.0 mg/kg and 75 minutes for 2.0 mg/kg). A sedative effect of ketamine was also observed in a dose-response manner with a peak effect between 15 and 30 minutes postadministration. No cardiopulmonary effects were observed with any dose of ketamine.

CONCLUSIONS

Results indicate that epidurally administered ketamine in the horse produces local spinal and central nervous system effects with analgesia and sedation but minimal cardiopulmonary effects.

CLINICAL RELEVANCE

Further studies are required to determine whether the analgesia is sufficient for surgery.

Growth hormone reduces bacterial translocation in radiation enteritis in the rat

BACKGROUND

Radiotherapy may be considered as one of the most effective treatments for digestive tumours. This procedure has major side effects, especially in fast growing tissues like intestinal mucosa. The administration of drugs that reduce or avoid radiation injury of the intestinal mucosa may be clinically advantageous. Growth hormone is a peptide suitable for this purpose by modifying cell proliferation within the intestinal crypt.

MATERIAL AND METHOD

Adult male Wistar rats were used in a model of abdominal irradiation. Each irradiated animal received 1200 cGy under anaesthesia and was sacrificed four and seven days later. The animals were treated with either saline or growth hormone (1 mg/kg/day) beginning immediately after the irradiation treatment. On the day of sacrifice, intestinal samples were taken for morphometric measurements and mesenteric lymph nodes for bacterial translocation.

RESULTS

Mortality was of 50% approximately and was not affected by growth hormone treatment in irradiated animals. Bacterial translocation increased (p < 0.05) in irradiated animals whereas no significant increase was observed in rats treated with growth hormone. Growth hormone promotes an earlier growth of intestinal villi in irradiated animals (p < 0.05).

CONCLUSIONS

Growth hormone promotes the morphologic adaptation of intestinal mucosa after abdominal irradiation, reducing bacterial translocation in rat.

Morphometric and proliferative effects of growth hormone on radiation enteritis in the rat

Radiation enteritis is a common occurrence after radiotherapy in patients with abdominal tumors. Growth hormone may modify the response of the intestinal mucosa to radiation through its effects on the cell cycle or by increasing cell mass. The aim of this study is to determine the effects of growth hormone in the radiation-induced morphoproliferative changes in the intestinal mucosa.

MATERIAL AND METHODS

An intestinal mucosal lesion was induced in adult male Wistar rats by means of abdominal irradiation with a lethal dose (LD50) of 1200 cGy. All animals received treatment with either saline or growth hormone for 7 days after irradiation. The animals were sacrificed on day 7. Body weight was determined the morphoproliferative status of the intestinal mucosa was assessed and the disaccharidase activity was measured.

RESULTS

Growth hormone reduced body weight loss and increased mucosal length in irradiated rats. Mucosal proliferation was incremented in both irradiated and nonirradiated growth hormone-treated rats. Disaccharidase activity levels were similar to or higher than control values in all treated groups.

CONCLUSION

Administration of growth hormone to irradiated rats reduces intestinal injury, probably as a consequence of an earlier recovery of intestinal morphology and functional status.

Anesthetic potency of desflurane in the horse: determination of the minimum alveolar concentration

OBJECTIVE

To determine the minimum alveolar concentration (MAC) of desflurane (DES) in the horse.

STUDY DESIGN

Prospective study.

ANIMALS

Six healthy adult horses (three males and three females) weighing 370 +/- 16 kg and aged 9 +/- 2 years old.

METHODS

Anesthesia was induced with DES vaporized in oxygen via a face mask connected to a large-animal, semiclosed anesthetic circle system. The horses were endotracheally intubated and positioned in right lateral recumbency. Inspired and end-tidal DES were monitored using a calibrated Ohmeda RGM 5250 multigas analyzer (Ohmeda-BOC, Spain). The MAC of desflurane that prevented gross purposeful movement in response to 60 seconds of noxious electrical stimulation of oral mucous membranes was determined.

RESULTS

The time from the start of DES administration to lateral recumbency was 6.1 +/- 0.9 min. The MAC of DES in these horses was 7.6 +/- 0.4%. Time required for the animal to regain sternal recumbency after 98 +/- 4 minutes of anesthesia was 6.6 +/- 0.5 minutes and the time to standing was 14.3 +/- 2.7 minutes.

CONCLUSIONS

The MAC of desflurane in these horses was 7.6 +/- 0.4%. DES provided a rapid induction to, and recovery from, anesthesia.

CLINICAL RELEVANCE

Desflurane offers the potential for more precise control during anesthesia, and may allow a faster and uneventful recovery. It is important to know the MAC of an inhalant to use it clinically.

Neurotensin increases intestinal adaptation and reduces enteroglucagon-like immunoreactivity after large bowel resection in rats

OBJECTIVE

To assess the effects of giving neurotensin on intestinal adaptation after colectomy and their relation to enteroglucagon-like immunoreactivity.

DESIGN

Laboratory experiment.

SETTING

Teaching hospital, Spain.

MATERIAL

55 Male Wistar rats.

INTERVENTIONS

All animals were anaesthetised before undergoing laparotomy; 24 animals had 75% of their colon resected. Half of the animals (12 in each group) were treated with neurotensin (600 micrograms/kg body wt/day) for 14 days.

MAIN OUTCOME MEASURES

Differences in the number of mitoses and in nuclear antigen staining of proliferating cells in the intestinal mucosal crypts; plasma enteroglucagon-like immunoreactivity.

RESULTS

After colon resection, the proliferative status, number of mitoses (p < 0.01), and nuclear antigen staining of proliferating cells (p < 0.001) increased significantly in the jejunum of animals treated with neurotensin (p < 0.05). Less pronounced effects were observed in colon and ileum. Plasma enteroglucagon-like immunoreactivity levels fell significantly in all animals given neurotensin (p < 0.05).

CONCLUSIONS

Neurotensin increases the adaptive intestinal process after colon resection and reduces plasma enteroglucagon-like immunoreactivity in rats.

Effects of exogenous neurotensin on intestinal postresectional growth in the suckling rat

BACKGROUND

In the suckling rat, massive bowel resection provokes intestinal malabsorption that leads to diminished growth. The object of this report was to test whether neurotensin, intestinal trophic peptide, enhances postresection intestinal adaptation, improving absorption and reducing the adverse effects of resection on growth.

METHODS

Fifty-seven 15-day-old suckling. Wistar rats were divided into four groups: 41 rats were subjected to resection of 90% of their small bowel, while the rest (n = 16) underwent laparotomy. Half of the animals, resected and laparotomized, were treated with neurotensin for 30 days. The body weight was monitored, and samples of bone and intestinal mucosa were obtained at the end of the study period for analysis. Blood was tested to determine iron, ferritin, folic acid, and vitamin B12 levels.

RESULTS

The resected animals lost body weight regardless of neurotensin administration. In the resected animals, femur weight increased significantly when they received neurotensin. Bowel resection provokes significant increases in the intestinal mucosa (crypts and villi), but after neurotensin administration, significant increases were detected only in the jejunum of the resected animals but not in the ileum of laparotomized rats. In the resected animals, significant decreases in iron, ferritin, folic acid, and vitamin B12 levels were observed. The postresection administration of neurotensin only produced a significant rise in the ferritin concentration.

CONCLUSIONS

In the suckling rat, neurotensin enhances the intestinal proliferative phenomenon but does not improve the course of medium-term postresection growth.

Actions of xylazine in young swine

OBJECTIVE

To determine sedative, analgesic, and basic cardiovascular effects of xylazine administered to pigs.

ANIMALS

6 two-month-old Landrace x Large White pigs.

PROCEDURE

Xylazine was administered i.v. at increasing dosages (1, 2, 4, 8, and 16 mg/kg of body weight) to otherwise unmedicated, conscious pigs, and the aforementioned effects were determined before xylazine administration and 2, 5, 10, and 15 minutes later. Then a higher xylazine dosage was given after the 15-minute measurements were taken.

RESULTS

None of the xylazine dosages induced sufficient analgesia to prevent painful response to tail clamping; considerable excitation with vocalization and without appreciable sedative effect was observed at all dosages. At lower dosages, cardiovascular effects were characterized by bradycardia and biphasic blood pressure response; initial hypertension was followed by hypotension. At higher dosages, severe hypotension with moderate bradycardia was followed by marked bradycardia and return to normal baseline values or slight increase in blood pressure.

CONCLUSION

Xylazine did not induce adequate sedative or analgesic effects in pigs at any dosage tested; however, cardiovascular effects were considerable. These effects of xylazine differ from those observed in other domestic species.

Bowel resection and neurotensin treatment. Histochemical study of neurotensin-like and somatostatin-like immunoreactivities and receptors

The influence of a bowel-trophic neurotensin (NT) treatment (13 days, 300 micrograms/kg/every 12 hrs.) on neurotensin-like immunopositive structures (neurons, fibres and epithelial-N-cells) and the neurotensin receptors (NTr) in the residual bowel after resection (90% small bowel or 75% colon) in the rat was studied using histochemical methods. Somatostatin-like (ST) immunopositive structures (neurons, fibres and epithelial-D-cells) and somatostatin receptors (STr) were also studied, comparatively. The results displayed a general increase of N-cells (11-17%) but not of D-cells, and a higher degree of variability section-to-section in the NT and ST immunopositive nervous structures (without increased density) after both resections, both with or without NT treatment. Receptors did not change after the small bowel resection but the colon resection and/or the NT treatment produced variations in the NT binding (from -24.3 to +16.85) in different intestinal regions. In a general sense, the variations among 1) the controls, 2) the resected animals, and 3) the resected and NT-treated animals, were of less extent (< or = 24%) than previously supposed for explaining the trophic effect of NT. Our results: a) confirm the autonomy, injury-resistance and tendency to maintain the physiological features of the bowel in very diverse situations; b) open new questions on both, the neurotensinergic changes after bowel resection and the mechanisms of the trophic effect of NT treatment, and c) suggest that, when neurotensin was applied as a trophic treatment in the cases of the need of a bowel resection, no important neurotensinergic or somatostatinergic side effects should be expected in the remaining bowel. However, the higher degree of variability section-to-section after surgery in the nervous structures was not modified by the NT treatment. This fact, and the different response of various intestinal regions to the NT treatment, suggest that functional problems in the remaining bowel could be maintained despite the growth of the mucosa induced by the NT treatment.

[Response of the intestinal mucosa to different enteral diets in situations of surgical stress and malnutrition]

INTRODUCTION AND OBJECTIVES

malnutrition and surgical stress is a relatively common association. At present, different enteral nutrition formulation are available, which are potentially applicable to different pathological conditions. The use of one diet or another may modify both the nutritional state as the intestinal structure and function. The objective of this study is to evaluate, in a malnutrition and surgical stress model in the rat, the effect of four enteral diets on the ponderal and structural evolution of the intestinal mucosa.

MATERIAL AND METHODS

adult Wistar rats weighing 230 g divided into four groups (n = 8/group), according to the enteral nutrition diet administered (elemental-elemental-028, polymeric with fiber-Enrich, peptidic with glutamine-Alltraq, and rich in arginine, fatty acids, and CO3 impact). All animals were subjected to an acute protein deficit for one week, and surgical stress consisting of the performance of a laparotomy. During another week the animals were fed with one of the four diets on a hypocaloric base of 195 kcal/week/rat, to maximize the effects of each diet, after which the animals were sacrificed. Determinations were made of body and intestinal weight variations, and samples were taken of the jejunum, ileum, and colon tissue. A histomorphometric study was conducted on these samples (crypt length and villosity).

RESULTS

all groups lost weight in a similar manner with respect to the initial weight, with the exception of the animals fed with the polymeric diet with fiber, whose weight loss was even more marked. The intestinal weight was greater in those animals who received an arginine rich diet. In the jejunum and ileum samples the villus length was greatest in the group receiving a glutamine rich diet, with the length being shortest when fed with the elemental diet. The crypt depth showed as similar variation. In the colon, the greatest crypt depth was seen in the animals who received a fiber rich diet.

DISCUSSION AND CONCLUSIONS

diets rich in glutamine and arginine, as well as the elemental diet, are more efficient when it comes to maintaining body weight, although the latter is the one which maintains the small intestine weight the least, without there being a direct relation between these two parameters. The enriched diets are the ones which give the best results when it comes to maintaining body weight and mucosal mass. In the colon, the fiber enriched diet stimulate the growth of colonic mucosa.

Comparative effects of growth hormone in large and small bowel resection in the rat

Our aim was to assess the proliferative effect of human growth hormone on ileal mucosa after two different adaptation models of massive small and massive large bowel resection. Male Wistar rats were assigned to control-laparotomy, 90% small bowel resection, or 75% large bowel resection and were treated with either saline or human growth hormone daily for 7 days (total six groups; n = 8/group). Ileal proliferative status was assessed by means of histomorphometry and proliferating cell nuclear antigen. Plasma somatostatin was quantitated. Growth hormone increased (P < 0.01) mucosal height in all groups with a more marked effect on the crypt than on villus height. Proliferating cell nuclear antigen-labeled cells increased similarly (P < 0.01). Small bowel resection appears to favor a more marked increment in villus height than large bowel resection. Compared to control saline-treated group, the remaining groups showed decreases in plasma somatostatin (P < 0.01). Human growth hormone has a marked trophic effect on intestinal mucosa, even in hyperproliferative states. Decreased plasma somatostatin associated with intestinal hyperplastic mucosa suggests a possible relationship with the adaptive process.

[Effects of neurotensin on the development of suckling rats with intestinal resection]

Massive intestinal resection produces malabsorption which, in the suckling rat, reduces growth. Our aim was to determine whether the proliferative action of neurotensin, can reduce the negative effects on growth induced by bowel resection. Fifteen days old suckling Wistar rats were used. Twenty rats underwent 90% midgut resection and twelve were used as controls. Half the animals were treated with neurotensin (600 micrograms/kg-day) until sacrifice 30 days later. Body and bone weight were measured and mucosal samples obtained. All resected animals lost body weight and bone weight. Neurotensin treatment reduced femur weight loss. After bowel resection, significant trophic effects were observed at mucosal level (crypt and villous size) but only in the jejunum of resected animals neurotensin treatment had a trophic effect. In conclusion, neurotensin favors intestinal adaptation after resection without improving mid-term growth in the suckling rat.

[Somatostatin and growth hormone in post-colectomy intestinal hyperplasia in rats]

AIM

Somatostatin exerts significant effects on gastrointestinal function that may include mucosal growth regulation, probably through its action on growth hormone release. The aim of this work was to correlate somatostatin and growth hormone plasma levels and the hyperproliferative status of intestinal mucosa after colectomy.

EXPERIMENTAL DESIGN

Adult Wistar rats were divided into two groups: control sham operated (n = 8) and large bowel resection (n = 8). Seven days post-colectomy, the animals were killed. Ileal mucosal samples were assayed for proliferative status (morphometry, and proliferating cell nuclear antigen labeling) and blood samples for plasmatic somatostatin and growth hormone measurement.

RESULTS

A hyperproliferative status was observed with significant increases in villous length and crypt proliferating cell nuclear antigen labeling. Plasma somatostatin showed a 95% significant decrease while growth hormone levels increased significantly.

CONCLUSION

The intestinal adaptation seen after colectomy is associated with lower somatostatin and higher growth hormone plasma level, possibly by regulating the intestinal adaptative process.

[Administration of growth hormone enhances the intestinal adaptive response after resection of small intestine in rats]

The aim of this study was to assess the proliferative effect of growth hormone (GH) on the remnant intestinal mucosa after small bowel resection in the rat. Three groups (n = 8/group) of adult Wistar rats were established as follows: 1) control, 2) 90% small bowel resection (SBR) and 3) 90% small bowel resection + GH 1 mg/kg-day (SBR+GH) during 7 days. Ileal samples were taken prior to resection (basal), and at sacrifice, for assessment of intestinal mucosal growth by means of morphometric (crypt and villous length) and proliferative (proliferating cell nuclear antigen, PCNA) techniques. GH administered to resected rats (SBR+GH) significantly increased the number of proliferating cells and crypt and villous length when compared to resected non-treated animals (SBR). In conclusion, in the rat, GH markedly increases the trophic action of intestinal mucosa in hyperproliferative states like massive bowel resection, enhancing remnant bowel morphologic and proliferative adaptation.

[Changes in plasma levels of intestinal regulatory peptides following colonic resection in the rat]

The colon is considered as an endocrine organ producing regulatory peptides. Colon resection exerts an influence on remnant bowel including proliferative adaptive phenomena. The aim of this work was to determine the modifications of several regulatory peptides after colectomy and its relation with the gastrointestinal proliferative changes. 75% proximal colectomy was performed in Wistar rats. Seven groups were used according to sacrifice times: 24 h, 48 h, 72 h, 7 days, 14 days, 21 days and control group without resection. Results show significant decreases in somatostatin, neurotensin and cholecystokinin plasma levels maintained up to 21 days postsurgery. Gastrin is elevated with a highest peak at 72 h achieving basal levels at 21 day. Peptide YY show significant high levels between 72 h and 7 days. Secretin plasma levels are increased 24 h post-surgery, decreasing significantly at day 14. It is suggested that maintained low plasmatic levels of somatostatin, a known mucosal growth inhibitor, after colectomy may help the proliferative adaptation.

Cardiopulmonary and analgesic effects of epidural lidocaine, alfentanil, and xylazine in pigs anesthetized with isoflurane

To determine cardiopulmonary and analgesic effects of lidocaine, alfentanil, and xylazine in pigs anesthetized with isoflurane, 18 healthy Landrace-Large White pigs were studied (six for each drug). General anesthesia was induced with isoflurane in O2 and maintained with 1% to 1.2% end-tidal ISO, ensuring presence of a pain response before epidural drug administration. Heart rate (HR), arterial blood pressures (AP), cardiac output (CO), pulmonary arterial pressure, pulmonary capillary wedge pressure (PCWP), central venous pressure, respiratory rate (RR), tidal volume (TV), minute volume (MV), arterial blood gas data, core temperature (CT), and analgesic effects (by picking the lumbar area and the abdominal wall) were determined at various times (2, 5, 15, 30, 45, 60, and 90 minutes) after epidural administration of lidocaine (5 mg/kg), alfentanil (5 micrograms/kg), or xylazine (0.2 mg/kg), all diluted in NaCl 0.9% to 0.5 mL/kg. Statistical analysis included two-way analysis of variance for repeated measures and the least significant difference test for determining differences among means. A probability level of P < .05 was used. The following results were statistically significant decreases in systolic AP, HR, TV, RR, MV, CT, pH, PaO2, and TCO2 and increases in PCWP, PaCO2, and HCO3 after LID. After ALF, only CT and HCO3 decreased. Core temperature and TV decreased after XYL. Lidocaine provided 45 to 60 minutes of analgesia. Alfentanil had no analgesic effects, and xylazine provided 90 minutes of analgesia. The authors conclude that xylazine, when injected epidurally, provides suitable analgesia in isoflurane-anesthetized pigs.

[Intestinal trophic effect of neurotensin after colectomy]

Neurotensin is a trophic peptide for the intestinal mucosa. Intestinal resection is a well known adaptive process of mucosal growth. Our aim was to determine the effect of exogenous neurotensin administration on intestinal mucosal growth after colectomy in the rat. Two groups: colon resection (n = 15) and colon resection plus neurotensin (n = 15, 600 micrograms/kg/day, 13 days post-surgery) were studied. Intestinal growth was assessed by means of the proliferating cell nuclear antigen (PCNA) technique on the intestinal crypt. Our results showed that neurotensin increased (p < 0.0001) epithelial cell growth when compared to non treated animals. Body weight loss was found in the non treated group but not in neurotensin treated animals. In conclusion, neurotensin increases cell growth in rats with colectomy, and maintains body weight. Neurotensin may have beneficial effects in colectomized patients.

Trophic effects of neurotensin in massive bowel resection in the rat

The trophic effect of the administration of exogenous neurotensin on the intestinal mucosa was studied in rats following an 80% bowel resection. Villus length and mucosal DNA content were assessed in the jejunal and ileal mucosa of the remnant intestine 14 days after resection. The data obtained in an 80% resected control group (80% group) and an experimental group receiving an infusion of neurotensin (300 micrograms/kg/day) for 14 days subcutaneously (80% + NT group) were compared. The results indicate that the administration of exogenous neurotensin (80% + NT) increases villus length (jejunum: 920 +/- 77 vs 861 +/- 25 microns and ileum length: 975 +/- 23 vs 875 +/- 99 microns) to an extent greater than that observed in the 80% resected group not receiving exogenous neurotensin. The levels of mucosal DNA per milligram of protein increased significantly in both groups but was paradoxically less in the 80% + NT group than in the 80% resection group (jejunum: 8.12 +/- 0.56 vs 10.18 +/- 0.80; ileum: 8.63 +/- 0.43 vs 10.05 +/- 0.46). These data suggest that the administration of exogenous neurotensin to the rat potentiates the growth of intestinal villi and accelerates the intestinal trophic response seen following massive bowel resection. The increase in circulating enteroglucagon levels noted after neurotensin administration (80% + NT: 547 +/- 48 pg/ml vs 80%: 341 +/- 41 pg/ml) suggests that some of the trophic effects of neurotensin may be mediated, at least in part, by enteroglucagon. These data also suggest a potential role for the use of neurotensin in the initial treatment of individuals with short bowel syndrome.

Plasma enteroglucagon levels in different models of intestinal resection in the rat

To assess the influence of the different intestinal segments on the plasma enteroglucagon level, three models of intestinal resection in the rat were studied (jejunal, ileal, 90%). The basal values for this peptide and those obtained after an infusion of intraduodenal glucose were compared. The results obtained in basal/post-glucose infusion were: 50% proximal (jejunum): 220/728 pg/ml; 50% distal (ileum): 10/233 pg/ml; and the middle 90%: 108/297 pg/ml. The glucose infusion produced a maximal response, permitting a better evaluation of the differences among the three resection models. The highest levels corresponded to the group in which the entire ileum was conserved.

[Importance of the colon in intestinal adaptation. Study with the proliferating cell nuclear antigen]

Proliferating cell nuclear antigen (PCNA) is an auxiliary protein to DNA polymerase delta necessary for tissue cellular proliferation. The colon releases several peptides or hormones which are probably related to intestinal proliferation. Colonic resection determines adaptive changes in the remnant bowel. In the present study, proliferative changes after colectomy were studied by means of the murine monoclonal PC10 antibody. A control group (n = 10 rats) and a 75% proximal colon resection group (n = 10 rats) were studied. 14 days after resection, jejunal, ileal and colon samples were taken and assayed for PCNA. Relationship between immunostained nuclei and the total number of nuclei was determined. The three intestinal segments showed statistically significant increases (p < 0.001) in the number of immunostained nuclei. PCNA proliferative index was greater in the remnant large bowel.

[The effects of a benzopyrone derivative in experimental brain edema due to cold in the rabbit]

On this study, parenchymal changes during a cerebral edema caused by thermic injury (cool) on the rabbit, are analyzed. The work was based on the ultrastructural findings obtained by transmission electronic microscopy and on the effects produced by a benzopironic derived (F-117 Hydrosmina). The injury was produced with solid CO2, previous a craniectomy, on the dura mater of the left hemisphere. Forty rabbits were included into the study, the animals were distributed into five groups (n = 8): a control group and 4 treatment groups. One of the groups received treatment without previous cerebral injury. The group of rabbits with doses of 50 mg/Kg of weight showed focal and diffuse areas of edema alternating with less damaged areas, the edema was evident on the white substance. This group also showed a dissociation of the myelinic fibers and an intracytoplasmatic tumefaction into the glial cells. These findings contrast with the histopathological findings obtained from the rabbits (V), the extracellular edema was poor, the myelinic fiber disorganization was minimal with no vacuolar degeneration and no structural mitochondrial changes had been showed. The discontinuance of the hematoencephalic barrier caused by the cool could be a possible mechanism that causes the opening of the endothelial unions from the capillary vessels, changing their membranes and resulting in a free penetration of the molecule into the cerebral parenchyma.(ABSTRACT TRUNCATED AT 250 WORDS)

[Trophic activity of neurotensin in massive intestinal resection]

Regulatory peptides are among the main factors affecting the proliferative adaptive process of the small bowel; its mechanisms of action remains unknown. An 80% small bowel resection was done in Wistar rats (250-300 g) randomly assigned to two groups: control and neurotensin (300 mu/kg). Jejunal and ileal samples were taken on day 14 post-resection and histomorphometric (villous length) and proliferative (DNA content) measures were obtained. Results show an increase in villous length in the neurotensin group but no changes in DNA content were observed. We conclude that neurotensin increases intestinal mucosal growth after massive intestinal resection in the rat.

[The effect of resection of the jejunum and ileum on intestinal mucosal trophism. An experimental study on the rat]

Intestinal resection leads to anatomo-physiological adaptive changes in the small bowel depending on its localization and extension. Two 50% resection models were done, jejunal resection (55 cm.) and ileal resection (55 cm.), in the attempt to determine the trophic response of the remnant bowel from jejunal and ileal samples. Significant increases were seen in mucosal villous length, jejunal values were greater than ileal and the greatest values were when the whole ileum was conserved. No significant changes were observed in DNA contents. These data suggest the importance of the ileal segment in the intestinal adaptive process, especially on the jejunal segment, as well as the apparent end of this response two weeks after resection.