Anesthesia and analgesia
-
Anesthesia and analgesia · Nov 1996
Comparative StudyA comparison of the sensitivity of epidural and myogenic transcranial motor-evoked responses in the detection of acute spinal cord ischemia in the rabbit.
Monitoring motor-evoked responses to transcranial stimulation (tc-MERs) provides information about the functional status of the spinal cord during operations that pose the risk of spinal cord ischemia. Responses can be recorded from the epidural space (epidural tc-MERs) or from muscle (myogenic tc-MERs). In this study the relative sensitivity of epidural and myogenic tc-MERs to acute spinal cord ischemia was compared. ⋯ Lower extremity ischemia as a cause of changes in myogenic tc-MER amplitude was excluded by ligating the right femoral artery and demonstrating that myogenic responses were preserved for 30 min, before occluding the aorta. We conclude that myogenic responses are more sensitive to acute spinal cord ischemia than epidural responses. The rapid detection of spinal cord ischemia with transcranial myogenic motor-evoked responses could be of clinical use in assessing the adequacy of spinal cord blood flow during operations where the spinal cord is at risk.
-
Anesthesia and analgesia · Nov 1996
Orthostatic hypotension during postoperative continuous thoracic epidural bupivacaine-morphine in patients undergoing abdominal surgery.
Fifty patients undergoing colonic surgery received combined thoracic epidural and general anesthesia followed by continuous epidural bupivacaine 0.25% and morphine 0.05 mg/mL, 4 mL/h, for 96 h postoperatively plus oral tenoxicam 20 mg daily. Heart rate (HR) and arterial blood pressure (BP) were measured at supine rest, during orthostatic stress, and after walking prior to and 24, 48, and 72 h and 48 h postoperatively compared to preoperatively (P < or = 0.008); 16 vs 6 patients presented resting systolic BP values < 100 mm Hg (lower range, 70 mm Hg) post- versus preoperatively (P = 0.048). During orthostatic stress the decrease in systolic BP and concomitant increase in HR was similar post- versus preoperatively (BP, P > 0.3; HR, P > 0.34) and 12 vs 8 patient; (P = 0.45) experienced a systolic BP decrease > 20 mm Hg post- versus preoperatively. ⋯ Epidural infusion was discontinued in three patients due to either persisting resting or orthostatic hypotension. There was no correlation between ASA classification, intraoperative bleeding, or postoperative dizziness and incidence of orthostatic hypotension. The results suggest that patients undergoing abdominal surgery and treated with continuous small-dose thoracic epidural bupivacaine-morphine are subjected to a decrease of BP at rest and during mobilization, but not to an extent that seriously impairs ambulation in most patients.
-
Anesthesia and analgesia · Nov 1996
Nitric oxide synthase inhibition restores vasopressor effects of norepinephrine in ovine hyperdynamic sepsis.
To investigate the hypothesis that nitric oxide synthase (NOS) inhibition restores the vasopressor response to norepinephrine (NE) in ovine hyperdynamic sepsis, eight sheep were chronically instrumented. In the non-septic portion of the study, NE was titrated to achieve an increase in mean arterial pressure (MAP) by 15 mm Hg ("small dose"). Small-dose NE was repeated 1 h after administration of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME; bolus 5 mg/kg, followed by 1 mg.kg-1.h-1). ⋯ To increase MAP by 15 mm Hg, the NE dose had to be increased to 0.34 +/- 0.06 microgram.kg-1.min-1 (large dose). During L-NAME infusion, NE administration increased MAP by 16 +/- 2 mm Hg and 28 +/- 4 mm Hg (small and large dose, respectively). Thus, L-NAME restored the vasopressor response to NE in sepsis, and increased the vasopressor response to NE in a similar fashion in healthy and septic sheep.
-
Anesthesia and analgesia · Nov 1996
Thoracic epidural anesthesia improves functional recovery from myocardial stunning in conscious dogs.
The effects of thoracic epidural anesthesia (TEA) on the contractile performance of ischemic and postischemic myocardium have not been well investigated. The purpose of this investigation was to examine the effects of TEA on severity and duration of myocardial stunning in an experimental model for sublethal acute myocardial ischemia. Seven dogs were chronically instrumented for measurement of heart rate (HR), left atrial (LAP), aortic and left ventricular pressure (LVP), LV dP/dtmax' and myocardial wall-thickening fraction (WTF). ⋯ During ischemia neither the subendocardial/subepicardial nor the occluded/ normal zone blood flow was affected by TEA. TEA attenuates myocardial stunning in conscious dogs. This finding is consistent with data regarding a reduction of infarct size due to TEA.
-
Anesthesia and analgesia · Nov 1996
Editorial CommentRegional anesthesia in children: what have we learned?