Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuroprotective agents may exert their effect by reducing cerebral oxygen demand (CMRO2), increasing cerebral oxygen delivery, or by altering ongoing pathological processes. Barbiturates provide neuroprotection by reducing the CMRO2 necessary for synaptic transmission while leaving the component necessary for cellular metabolism intact. Isoflurane may exert a neuroprotective effect by a similar mechanism but its efficacy is likely less than that of barbiturates due to adverse effects on cerebral blood flow. Lidocaine reduces CMRO2 by affecting both cellular metabolic processes and synaptic transmission and thus resembles hypothermia in its mechanism of action. Benzodiazepines reduce CMRO2 by reducing synaptic transmission and their use as neuroprotectants produces less haemodynamic compromise than barbiturates. The mechanism of protection by calcium entry blocking agents appears to be due to improved blood flow as opposed to altering abnormal Ca++ fluxes. In contrast, agents such as ketamine and MK-801 may prevent abnormal Ca++ fluxes through their competitive interaction with N-methyl-D-aspartate receptors. Phenytoin prevents K(+)-mediated ischaemic events from progressing. Agents worthy of further investigation include corticosteroids, free radical scavengers, prostaglandin inhibitors and iron chelators.
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PMID:Brain protection: physiological and pharmacological considerations. Part II: The pharmacology of brain protection. 222 93

The authors have studied the protection against ischemic damage to rabbit spinal cord by pretreatment with agents that block neuronal activity and directly or indirectly reduce tissue metabolism. Hypothermia, thiopental, magnesium, lidocaine, and naloxone were used to pretreat the spinal cord prior to ischemia. Hypothermia and thiopental provided comparable protection: they each increased the duration of ischemia required to produce neurological deficits in 50% of the animals from 26 to 41 minutes. They also increased from 10 to 30 minutes the time that the postsynaptic waves of the spinal somatosensory evoked potential (SSEP) could be absent and the animal still have neurological recovery. Hypothermia and thiopental, when used together, increased the duration of ischemia required to produce neurological deficits to 57 minutes in 50% of the animals. Naloxone increased the duration of ischemia required to produce neurological deficits to 36 minutes in 50% of the animals, and increased to 20 minutes the time that the postsynaptic waves of the SSEP could be absent and the animal still have neurological recovery. Magnesium pretreatment improved neurological outcome, possibly by improving collateral circulation as the SSEP did not fail completely during aortic occlusion in all animals. Lidocaine was not beneficial, perhaps because of the prolonged hypotension that resulted.
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PMID:Protection against experimental ischemic spinal cord injury. 395 Jul 46

Delivery of cardioplegic (CP) solutions to all regions of the myocardium is critical for optimal myocardial protection during cardiac surgery. However, there are little data regarding the effects of CP agents upon coronary vascular resistance (CVR) and CP delivery. Accordingly, we evaluated blood CP (Hct 30) delivery and CVR during 75 minutes of multi-dose hypothermic blood CP arrest in an in vivo isolated dog heart preparation. Three groups of dogs were studied: K(K+ = 30 mEq/L; n = 6), L (Lidocaine = 400 mg/L; K+ = 4 mEq/L; n = 6), and KL (K+ = 30 mEq/L, Lidocaine 400 mg/L; n = 6) during total cardiopulmonary bypass and moderate systemic hypothermia (28 C). Basal CVR was calculated by measuring total coronary flow (HR 120/min; mean aortic pressure = 80 mmHg) in the empty beating heart. After aortic cross-clamping, the blood CP solution was infused into the aortic root at a constant pressure (80 mmHg) and constant temperature (16 +/- 2 C) for 60 seconds at 15 minute intervals for a total arrest time of 75 min. Total CP flow, CVR, O2 consumption, lactate extraction/production, and K+ balance during 75 minutes of arrest and 30 minutes of reperfusion were determined. The distribution of the CP solution in the left ventricle was measured with radioactive microspheres (9 +/- 1 mu). Biopsy specimens were taken to measure wet to dry ratios. Values are mean +/- SEM. Data were analyzed by BMDP-P2V. During the first CP infusion, after aortic cross-clamping, no differences in CVR or CP distribution were found among the three groups. However, CVR was increased significantly in the K group during the second CP infusion (O': 0.98 +/- 0.20 mmHg/ml/min/100 g; 15': 2.66 +/- 0.82; p less than 0.001). The CVR remained high for the remainder of the arrest period. Moreover, total, epi- and endocardial flow decreased significantly (54%, p less than 0.001). In groups L and KL, no significant changes in CVR were seen. Groups K and KL showed a significant K+ extraction during the first CP infusion. During the early reperfusion period, K+ washout occurred in these two groups, which was not seen in the L group. There was no significant difference between the three groups in myocardial O2 consumption, lactate metabolism, and water content during the arrest and the reperfusion period. In conclusion, high concentrations of K+ (30 mEq/L) can markedly increase CVR and impair blood CP delivery and distribution. These effects can be prevented by lidocaine. These findings warrant reassessment of the various additives to CP solutions and their effects on CVR and CP distribution during multi-dose hypothermic CP arrest.
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PMID:Blood cardioplegia delivery. Deleterious effects of potassium versus lidocaine. 661 50

Two sets of experiments were performed to characterize the role of the Pre-Optic Area of the Anterior Hypothalamus (POAH) in the decrease in set point and hypothermia that follows severe hemorrhage. In the first set, lidocaine or artificial cerebrospinal fluid (ACSF) was microinjected into the POAH of rats at the time of hemorrhage. Lidocaine microinjection attenuated the hemorrhagic hypothermia by approximately 50%. The mean drop in core temperature (Tc) following hemorrhage was 1.5 degrees C with ACSF microinjection (N = 6), 0.70 degrees C (N = 6) with lidocaine, and 1.77 degrees C (N = 6) after sham microinjection. This partial attenuation of the hemorrhagic hypothermic response indicates that an intact POAH is necessary for at least some of the hypothermia following hemorrhage. In the second experimental set, hypothalamic tissue temperature (Thyp) was modulated in an attempt to alter the hemorrhagic hypothermic response. Bilateral closed-ended cannulas were inserted into the POAH. One cannula consisted of a water-perfused thermode to change local tissue temperature. The other housed a thermocouple to measure local temperature. The effectiveness of the thermode was first confirmed in conscious rats, evidenced by an inverse deflection in Tc upon Thyp modulation. Then, the POAH region was either heated, cooled, or sham perfused following hemorrhage. The mean drop in Tc following hemorrhage was 2.16 degrees C (N = 5) with hypothalamic heating, 1.35 degrees C (N = 5) with cooling, and 1.44 degrees C (N = 5) following the sham perfusion control. Heating of the POAH significantly exacerbated the hemorrhagic hypothermic response. These data further suggest that the POAH is at least partially responsible for mediating hemorrhagic hypothermia.
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PMID:The Pre-Optic Anterior Hypothalamus (POAH) partially mediates the hypothermic response to hemorrhage in rats. 1580 94

A 4-mo-old red fox (Vulpes vulpes) was found recumbent after a vehicular accident. Radiology revealed several limb fractures and the fox underwent surgery after 24 hr of initial stabilization. Premedication consisted of dexmedetomidine and morphine. Anesthesia was induced with ketamine and midazolam and maintained with isoflurane. Lidocaine, bupivacaine, and morphine were administered epidurally and further analgesia was provided with meloxicam. The heart rate and respiratory rate of the fox remained stable during surgery and, except for a mild hypothermia, the recovery from anesthesia was uneventful. The postoperative pain scores were low and the animal was transported to a rehabilitation facility and eventually released to the wild. The low pain scores postoperatively should be attributed to the successful application of epidural anesthesia and analgesia.
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PMID:Anesthetic management of a 4-month-old red fox (Vulpes vulpes) for orthopedic surgery. 2583 91