Examining the quality of work-life of paramedics in northern Ontario, Canada: A cross-sectional study.

BACKGROUND: Paramedics are exposed to multiple stressors in the workplace. They are more likely to develop occupational-related stress conditions compared to other occupations. This study focused on understanding the factors affecting QoWL of paramedics in northern Ontario, Canada; a particular focus was on understanding the personal and organizational factors, such as practicing community paramedicine (CP), which may be associated with Quality of Work Life (QoWL). METHODS: Paramedic QoWL was assessed using an online survey that was distributed to approximately 879 paramedics across northern Ontario. The survey included the 23-Item Work- Related Quality of Work Life Scale. Data analysis involved linear regressions with nine predictor variables deemed to be related to QoWL for paramedics with QoWL and its six subscales as dependent variables. Multiple linear regressions were used to assess the personal and organizational factors, such as practicing of CP, which predicted QoWL. RESULTS: One hundred and ninety-seven paramedics completed the questionnaire. Overall, the mean QoWL score of all paramedic participants was 73.99, and this average compared to relevant published norms for other occupations. Factors that were most associated with higher QoWL were, experience practicing CP (p < 0.05), number of sick days/year (p < 0.01), and higher self- rated mental health (p < 0.001). CONCLUSIONS: Higher paramedic QoWL appears to be associated with many factors such as number of sick days per year, self-rated mental health, and participation in CP. EMS organizations should consider establishing necessary workplace health promotion strategies that are targeted at improving QoWL for paramedics.

Adrenal medullary enkephalin-like peptides may mediate opioid stress analgesia.

Different patterns of fact shock activate opioid and nonopioid mechanisms of stress analgesia in the rat. Opioid, but not nonopioid, stress analgesia is reduced by adrenal demedullation and denervation and is potentiated by reserpine, a drug known to increase concentrations of adrenal medullary enkephalin-like peptides. It is suggested that adrenal enkephalins mediate opioid stress analgesia.

Morphine analgesia: enhancement by shock-associated cues.

Recent research has shown that rats exposed to repeated stress display enhanced morphine analgesia. This study examined the possible contribution of classically conditioned analgesia to this effect. First, drug-naive rats exposed to nine daily sessions of stress, each consisting of a single 45-s exposure to footshock, subsequently displayed enhanced analgesic responsiveness to morphine 1 and 10 days after stress (Experiments 1, 2, and 5). This enhancement was also observed in morphine-experienced rats 1 and 8 days after stress (Experiment 1). Second, the effect of footshock stress on morphine analgesia was found to be specific to the environment in which stress was administered (Experiments 2 and 3). Rats tested in the same distinctive environment in which stress was administered displayed enhanced morphine analgesia; rats shocked elsewhere did not differ from nonshocked controls (Experiment 2). Third, conditioned analgesia was found under the same conditions that yielded enhanced morphine analgesia (Experiments 2 and 4). Lastly, both this conditioned analgesia and the acute analgesia elicited by the footshock stressor were found to be attenuated by naloxone (Experiments 5 and 6). These data are consistent with the hypothesis that the enhanced morphine analgesia observed after repeated footshock stress reflects the contribution of an opioid mediated , conditioned analgesia elicited by cues formerly paired with the stressor.

Corticotropin-releasing factor modulates defensive-withdrawal and exploratory behavior in rats.

The role of corticotropin-releasing factor (CRF), an endogenous neuropeptide, in modulating species-typical responses was examined in an unfamiliar open field containing a small chamber. Rats placed in this small chamber spent most of their time withdrawn in it. However, rats given an intracerebroventricular injection (20 micrograms) of alpha-helical CRF(9-41), a CRF receptor antagonist, emerged from the chamber and explored the unfamiliar open field. Additional studies showed that after 1 exposure to the test environment, vehicle-treated rats increased their time spent in the open field and returned intermittently to the chamber. This result suggests that reexposure reduces the threatening impact of an unfamiliar open field. Importantly, CRF (300 ng) injected centrally, but not peripherally, before reexposure to the test environment significantly reduced exploration in the open field and increased a pattern of defensive-withdrawal into the chamber. Data suggest that whether defensive-withdrawal or exploratory behavior is exhibited may depend on CRF actions in brain systems that mediate the perception of threat in the environment.

Aversion instead of preference learning indicated by nicotine place conditioning in rats.

Although nicotine is a drug of abuse for millions of smokers, it has been difficult to demonstrate clearly the motivational properties of nicotine with rats using the conditioned place preference (CPP) paradigm. The first experiment attempted to replicate CPPs reported by other researchers using nicotine doses of 0.4, 0.8, and 1.2 mg/kg. There was a trend for all three doses to produce aversions, but it was significant only for the 0.8 mg/kg dose. Exposures to the CS alone extinguished aversions, but a "priming" dose (0.2 mg/kg) of nicotine given after extinction produced aversions only in animals exposed to 1.2 mg/kg. Experiment 2 tested whether preexposure to morphine or nicotine would sensitize animals to nicotine's reinforcing effects. In this experiment, rats were exposed to either six nicotine (0.6 mg/kg) or morphine (1.0 mg/kg) dosings prior to preference conditioning. Neither preferences nor aversions were observed in any group following subsequent conditioning with 0.6 mg/kg nicotine. The results suggest that previous observations of preference effects may have been due to specific procedural factors or may have depended on negative reinforcement due to stress reduction.

Chest wall stabilization using plate fixation.

Large defects of the chest wall require stabilization of the remaining thorax to prevent paradoxical movement. A technique of fixation using rib grafts and compression plates is presented.

Antagonism of endogenous CRH systems attenuates stress-induced freezing behavior in rats.

Three experiments were conducted to test the hypothesis that brain corticotropin-releasing hormone (CRH) systems mediate stress-induced freezing behavior, an index of a rat's level of fear. We administered i.c.v. 0-50 micrograms of alpha-helical CRH9-41 (a specific CRH antagonist) before foot shock and showed that this peptide had little effect on baseline preshock behavior but significantly attenuated the occurrence of shock-induced freezing. We concluded that this attenuation of freezing behavior was not related to the effects of alpha-helical CRH9-41 on the animals' sensitivity to pain, because no significant effects on latency to respond on a hot-plate test of pain sensitivity were found. We also showed that alpha-helical CRH9-41 has a relatively rapid time course of action when administered i.c.v., since it blocked shock-induced freezing when given 20 min but not 40 min before foot shock. Our findings suggest that endogenous CRH systems mediate stress-induced, fear-related behavior through mechanisms other than alteration of nociceptive systems.

Aversion to the reinforcer differentially affects conditioned reinforcement and instrumental responding.

Rats were trained to press a bar for sucrose solution delivered by a dipper; they then received pairings of sucrose and lithium chloride (LiCl) in the home cage and were tested for bar pressing. In the first and second experiments, the conditioned aversion to sucrose had no effect on unreinforced bar pressing in the test, but the aversion reduced bar pressing reinforced either by sucrose or by the operation of the empty dipper. In the third and fourth experiments, presses during training were reinforced by sucrose only in the presence of an audiovisual discriminative stimulus; in the test, the aversion to sucrose reduced pressing reinforced by the discriminative stimulus, but the aversion had no effect on unreinforced pressing in either the presence or the absence of the discriminative stimulus. Thus, pairings of sucrose and LiCl reduced the reinforcing value of sucrose and also of a stimulus previously paired with sucrose, but they had no effect of an instrumental response previously reinforced by sucrose or on the discriminative properties of a stimulus paired with sucrose.

The opioid/nonopioid nature of stress-induced analgesia and learned helplessness.

Exposure to a variety of stressors produces a subsequent analgesic reaction. This stress-induced analgesia (SIA) is sometimes opioid in nature (reversed by opiate antagonists and cross-tolerant with morphine) and sometimes nonopioid. Both 30 min of intermittent footshock and 60-80 five-sec tailshocks have been shown to produce opioid SIA, whereas 3 min of continuous footshock and 5-40 tailshocks produce nonopioid SIA. We report that both of the opioid SIA procedures produce a learned helplessness effect as assessed by shuttlebox escape acquisition and an analgesia that is reinstatable 24 hr. later. The nonopioid procedures produce neither a learned helplessness effect nor a reinstatable analgesia. It is argued that these data implicate the learning of uncontrollability in the activation of opioid systems.

Relation between self-reported affect and drug urges and cravings in continuing and withdrawing smokers.

In 2 experiments we investigated the effects of withdrawal and stress on the affective correlates of urges to smoke. In both, habitual cigarette smokers were divided into continuing and withdrawing smoker groups. In the 1st study, 44 adults reported current mood, urge, and expectations over a 24-hr period. In the 2nd, a controlled laboratory study, urge, affect, and physiological data were obtained from continuing and withdrawing groups (N = 64) exposed to high- or low-stress conditions. Urges among withdrawing smokers were positively associated with negative affect and negatively associated with positive affect; continuing smokers reported urges that were directly associated with positive affect and unrelated to negative affect. Stress and withdrawal produced urge self-reports that were related to negative affect. Moreover, subjects who smoked after exposure to withdrawal and stress reported greater pleasure and arousal than did other subjects.

ICV-CRH potently affects behavior without altering antinociceptive responding.

To explore the hypothesized integrative function of corticotropin releasing hormone (CRH) in the stress response, stress-related behaviors including antinociception were studied in rats after either intracerebroventricular (ICV) or peripheral administration of CRH. The effects of low-dose (0.3 microgram) and high-dose (3.0 micrograms) ICV-CRH were compared to those of vehicle, employing a within-S design. The two doses yielded comparable behavioral changes suggestive of increased arousal and stress. These changes were characterized by significant increases in grooming, walking, burrowing, self-gnawing, and pica, and decreases in rearing and sleeping. None of these effects of ICV-CRH were obtained with peripheral administration of the same doses. The hot-plate test of analgesia failed to show a significant effect of ICV-CRH or peripherally administered CRH. A between-S experiment incorporating both the tail-flick and the hot-plate tests of analgesia compared ICV-CRH (3.0 micrograms) with vehicle. ICV-CRH did not affect antinociceptive responding in either of these tests. In contrast, ICV morphine (10 micrograms) yielded potent analgesia in both tests. Thus, with doses of ICV-CRH yielding clear evidence of stress-related behavior, no evidence of analgesia was obtained. These findings question the possible role of central CRH systems in antinociceptive processes.

Hungry, but not thirsty, rats prefer flavors paired with ethanol.

The present experiments examined the reinforcing effects of an ethanol (EtOH) unconditioned stimulus (UCS) on conditioned flavor preferences in food-deprived rats and in water-deprived rats. In Experiment 1A food and water deprived animals received distinct conditioning treatments. One half of the animals were intragastrically intubated with EtOH (0.5 g/kg), and thereafter allowed 20 min free access to similar flavored drinking solutions. Remaining animals were intubated with distilled water. All animals received 15 presentations of an EtOH-paired flavor. A two-bottle preference test was subsequently used to evaluate preferences or aversions to flavors paired with EtOH in food-deprived and water-deprived animals. Results of Experiment 1A showed that food-deprived animals preferred the flavor associated with EtOH. Conversely, preferences for EtOH-paired flavors were not established in water-deprived animals. In Experiment 1B deprivational states of animals used in Experiment 1A were reversed without further drug training. Following a two week habituation period to deprivation state animals again received a two-bottle preference test to re-evaluate preferences or aversions to the EtOH-paired flavors. Results of those manipulations indicated that an ethanol aversion was established in the water-deprived animals. Those results indicated that water-deprived animals of Experiment 1B reversed their EtOH-paired flavor preference when the caloric need associated with food deprivation conditions was eliminated. Since deprivational state determined the development of EtOH preferences, the present results indicate that caloric need may play an initial role in establishing conditioned preferences for EtOH.

ICV-CRH alters stress-induced freezing behavior without affecting pain sensitivity.

Freezing is an adaptive response often induced by stressful, fear-eliciting stimuli. Three experiments with rats investigated the effects of intracerebroventricular (ICV) administration of corticotropin-releasing hormone (CRH) on freezing behavior and pain sensitivity. Experiments 1 and 3 demonstrated that ICV-CRH (300 ng) enhanced shock-elicited freezing. In Experiment 1, ICV-CRH also enhanced recovery from shock-elicited freezing, suggesting that the peptide has a biphasic effect. Experiments 2 and 3 established that CRH-induced freezing was not caused by heightened pain sensitivity. Interestingly, in Experiment 2, hot-plate exposure produced increased freezing that was attenuated by ICV-CRH. Thus, the direction of the ICV-CRH effect on freezing was found to depend on the nature of the stressor. These results suggest that endogenous CRH systems modulate stress-induced freezing.

The effects of ICV-CRH on novelty-induced behavior.

To assess whether centrally administered corticotropin-releasing hormone (CRH) modulates behavioral and antinociceptive effects of exposure to a novel environment, vehicle or 0.03, 0.3, or 3.0 micrograms of CRH was administered intracerebroventricularly (ICV) to rats, which were then tested under novel or familiar conditions. Novelty decreased sleeping and grooming and increased rearing, walking, and latency to respond on the hot-plate test of analgesia. CRH increased grooming and walking, decreased rearing and sleeping, and had no effect in the hot-plate test. The lowest dose was without effect on any measure; otherwise, CRH effects generally were dose-dependent. There was no evidence that CRH selectively enhanced or interfered with novelty-induced behavioral changes; it influenced behavior to the same degree in both test conditions. However, test condition selectively modulated the degree of peptide-induced self-gnawing and burrowing.

Prior hot plate exposure enhances morphine analgesia in tolerant and drug-naive rats.

The associative model of morphine tolerance predicts that established tolerance should be attenuated, i.e., extinguished, by placebo injections in the former morphine injection environment. The present study examined the effect of placebo sessions, with and without accompanying nociceptive stimulation, on the extinction of analgesic tolerance. In Experiment 1, rats rendered tolerant to morphine displayed recovery of morphine's analgesic action only following placebo sessions including exposure to a painful hot plate surface (52.5 degrees C); placebo sessions on a cool plate (23-24 degrees C) failed to attenuate tolerance even though these placebo sessions more closely matched the stimulus conditions of tolerance acquisition. In Experiment 2, repeated hot plate exposures were similarly found to enhance morphine analgesia in drug-naive rats. These results question an extinction account of the effect of hot plate placebo sessions observed in Experiment 1. Instead, they suggest that nociceptive hot plate exposures, per se, are sufficient to enhance subsequent morphine analgesia.

Temporal properties of the rewarding and aversive effects of amphetamine in rats.

To associate amphetamine with a location and a flavor, rats were given amphetamine injections and then confined for 20 min in one side of a shuttlebox with access to a flavored solution; on control trials with saline injections, they were confined for 20 min on the opposite side with a different flavor. Three groups of rats were placed in the shuttlebox either 5 min, 120 min, or 240 min after the injections. In subsequent choice tests, the 5 min and 120 min groups preferred the side and avoided the flavor associated with amphetamine; the 240 min group was indifferent between the sides and the flavors.

Rewarding and aversive effects of morphine: temporal and pharmacological properties.

To assess morphine-induced location preferences and flavor aversions, rats were administered morphine sulfate (10 mg/kg, IP) either immediately before (Experiment 1) or immediately after (Experiment 2) confinement for 20 min in one side of a shuttlebox with access to a flavored solution. On control trails the rats were administered saline and confined for 20 min on the opposite side with a differently flavored solution. In subsequent choice tests, it was found that morphine injections before confinement produced a preference for the side associated with morphine and indifference to the flavors, whereas morphine injections after confinement produced an aversion to the flavor paired with morphine and indifference to the sides. Experiments 3 and 4, using a procedure similar to that of Experiment 1, showed that naloxone (1 mg/kg, IP) blocked the morphine-induced side preference, although given alone it was without effect in this test.

1991 Volvo Award in experimental studies. Cauda equina syndrome: neurologic recovery following immediate, early, or late decompression.

An animal model of cauda equina syndrome was developed. Neurologic recovery was analyzed following immediate, early, and delayed decompression. Five experimental groups, each containing six dogs, were studied. Compression of the cauda equina was performed in all 30 dogs following an L6-7 laminectomy. The cauda equina was constricted by 75% in each group. The first group was constricted and immediately decompressed. The remaining groups were constricted for 1 hour, 6 hours, 24 hours, and 1 week, respectively, before being decompressed. Somatosensory evoked potentials were performed before and after surgery, before and immediately after decompression, and 6 weeks following decompression. Daily neurologic exams using the Tarlov grading scale were performed. At 6 weeks postdecompression, all dogs were killed, and the neural elements analyzed histologically. Following compression, all 30 dogs had significant lower extremity weakness, tail paralysis, and urinary incontinence. All dogs recovered significant motor function 6 weeks following decompression. The dogs with immediate decompression generally recovered neurologic function within 2-5 days. The dogs receiving 1-hour and 6-hour compression recovered within 5-7 days. The dogs receiving 24-hour compression remained paraparetic 5-7 days, with bladder dysfunction for 7-10 days and tail dysfunction persisting for 4 weeks. The dogs with compression for 1 week were paraparetic (Tarlov Grade 2 or 3) and incontinent during the duration of cauda equina compression. They recovered to walking by 1 week and Tarlov Grade 5 with bladder and tail control at the time of euthanasia. Immediately after compression, all five groups demonstrated at least 50% deterioration of the posterior tibial nerve evoked potential amplitudes.(ABSTRACT TRUNCATED AT 250 WORDS)

Spinal cord monitoring. Results of the Scoliosis Research Society and the European Spinal Deformity Society survey.

The Scoliosis Research Society (SRS) and the European Spinal Deformity Society (ESDS) membership was surveyed regarding the use of intraoperative monitoring of somatosensory evoked potentials in spinal surgery. A total of 242 people responded, with 188 using intraoperative monitoring. A second survey was distributed detailing the technical aspects of monitoring, of which 71 were returned. A total of 342 neurologic deficits were reported to have occurred with monitoring in place. Two hundred forty-six (72%) were accurately detected, and 96 (28%) were not detected by sensory cord evoked potentials (SCEP). There were 1,003 false-positive cases reported. The incidence of false-negative cases was related to those not monitoring both latency and amplitude, to using fewer recording electrodes, and with those surgeons doing more kyphosis corrections.

Subjective dimensions of heroin urges: influence of heroin-related and affectively negative stimuli.

Thirty-five male drug-free heroin addicts rated their affect, craving, and withdrawal in response to boring, anxiety-eliciting, and heroin stimuli. Results revealed that: (a) heroin cues were more effective than boring or anxiety-eliciting cues in prompting self-reports of craving or withdrawal; (b) heroin cues produced an affective state characterized by self-reported low-pleasure and high anxiety/tension; (c) craving was not correlated with any particular affective state, but rather was associated with a variety of negative affects--anxiety, depression, fatigue, anger; (d) the coherence (intercorrelations) of affective, craving, and withdrawal measures was greatest when addicts made their self-ratings immediately after exposure to drug stimuli; and (e) while addicts routinely reported craving without withdrawal sickness, they virtually never reported withdrawal sickness without reporting craving. These results suggested that the potential for negative reinforcement subserved stimulus elicited craving and that craving involved cognitive appraisal processes (attributions, expectations).