Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2001
The effects of endogenous and exogenous vasopressin during experimental cardiopulmonary resuscitation.
Exogenous vasopressin is a promising vasopressor when blood pressure is critically threatened, but the role of endogenous vasopressin during cardiopulmonary resuscitation (CPR) is unknown. We assessed the role of endogenous versus exogenous vasopressin in a porcine open chest CPR model. Seven minutes before induction of cardiac arrest, seven pigs received 10 microg/kg of a selective vasopressin V(1)-receptor-antagonist (Blocked Vasopressin group); another 12 pigs in two groups received saline administration only. ⋯ In conclusion, pigs with blocked endogenous vasopressin had poor coronary perfusion pressure and left ventricular myocardial blood flow during open chest CPR, and could not be successfully resuscitated. All pigs with effective endogenous vasopressin or pigs with effective endogenous vasopressin and additional exogenous vasopressin had good left ventricular myocardial blood flow during experimental CPR, and survived the 1-h postresuscitation phase. We conclude that endogenous vasopressin is an adjunct vasopressor to epinephrine and may serve as a back-up regulator to maintain cardiocirculatory homeostasis.
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Anesthesia and analgesia · Jun 2001
Comparative Studyalpha-1 and alpha-2 Adrenergic antagonists relieve thermal hyperalgesia in experimental mononeuropathy from chronic constriction injury.
Phentolamine, a nonspecific alpha 1- and alpha 2-adrenergic antagonist, relieves pain in patients with reflex sympathetic dystrophy. We sought to determine whether phentolamine, prazosin (alpha 1 antagonist), or SKF86466 (alpha 2 antagonist) relieve thermal hyperalgesia in rats with neuropathic pain. Four days after producing a chronic constriction injury (CCI), thermal hyperalgesia was tested by measuring paw withdrawal latency (PWL). ⋯ PWL did not return to baseline levels after 1 or 2 mg/kg of prazosin or SKF86466 but did so after 35 min after phentolamine 2 mg/kg. After 5 mg/kg, PWL returned to preoperative values between 5 and 50 min for phentolamine, at 35 and 65 min for prazosin, and at 50 min for SKF86466. We conclude that both alpha1 and alpha2 peripheral receptors of the sympathetic nervous system are involved in the thermal hyperalgesia caused by CCI and that thermal hyperalgesia can be reversed by both alpha1 and alpha2 antagonists in a dose-dependent manner.
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Anesthesia and analgesia · Jun 2001
Modulations of spinal serotonin activity affect the development of morphine tolerance.
To test whether modulations of spinal serotonin (5-HT) levels would affect the development of morphine tolerance, we treated rats with either intrathecal 5-HT or 5,7-dihydroxytryptamine (5,7-DHT; a 5-HT neurotoxin) in addition to systemic infusion with morphine (2 mg x kg(-1) x h(-1)). Continuous infusion of 5-HT (10 microg x 6 microL(-1) x h(-1)) into the lumbar subarachnoid space of rats for 9 h accelerated the development of morphine tolerance. The area under the curve for the tail-flick latency test was 454.1 +/- 35.1 in the Sham Control group vs 327.6 +/- 41.0 in the 5-HT-Infused group. mu-opioid receptor binding in the lumbar spinal cord showed a decrease in the Bmax (maximal binding -46.5%), but not the binding affinity (Kd), in 5-HT-infused rats. ⋯ The binding study indicated that the affinity of lumbar micro-opioid receptors decreased 196% in 5-HT-depleted rats, whereas there was no effect on apparent binding. The infusion of 5-HT (10 microg x 6 microL(-1) x h(-1)) was not analgesic and the 5,7-DHT-induced lesion did not affect acute morphine-induced analgesia. We conclude that activity of spinal 5-HT-containing neurons plays a crucial role during the development of morphine tolerance.
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Anesthesia and analgesia · Jun 2001
Dose-response characteristics of midazolam for reducing diaphragmatic contractility.
A sedative dose of midazolam decreases contractility of the diaphragm, but no data are available concerning the relationship between dose and diaphragmatic contractility. We studied the dose-response characteristics of midazolam for reducing the diaphragmatic contractility in dogs. Animals were divided into three groups of eight each: Group 1 received no study drug, Group 2 was infused with a sedative dose of midazolam (0.1 mg/kg initial dose plus 0.1 mg x kg(-1) x h(-1) maintenance dose), and Group 3 was infused with an anesthetic dose of midazolam (0.1 mg/kg initial dose plus 0.5 mg x kg(-1) x h(-1) maintenance dose). ⋯ Compared with Group 1, Pdi and Edi for each stimulus decreased during midazolam infusion in Groups 2 and 3 (P < 0.05). The decrease in Pdi and Edi was more in Group 3 than in Group 2 (P < 0.05). We conclude that midazolam decreases, in a dose-dependent manner, contractility of the diaphragm in dogs.