Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1999
Comparative StudyThe effects of clonidine and dexmedetomidine on human neutrophil functions.
Neutrophil functions are inhibited by various anesthetics. Clonidine and dexmedetomidine, alpha2-agonists, are often used as adjuncts to anesthesia. Thus, we conducted the current study to determine the effect of clonidine, dexmedetomidine, and xylazine at clinically (or veterinary anesthetically) relevant concentrations (and 10 and 100 times these concentrations) on several aspects of human neutrophil functions using an in vitro system. The three alpha2-agonists had no effects on chemotaxis, phagocytosis, or superoxide anion (O2-) production of neutrophils, except that the highest concentration of clonidine inhibited chemotaxis. Increases in intracellular calcium concentrations in neutrophils stimulated by chemotaxin were not influenced by clonidine, dexmedetomidine, or xylazine. Unchanged calcium concentrations may contribute to failure to modulate the neutrophil functions. In addition, these drugs did not scavenge O2- generated by the cell-free (xanthine-xanthine oxidase) system. This is the first report concerning the effect of clonidine or dexmedetomidine on human neutrophil functions. Our findings suggest that we may not have to take extra precautions in using the alpha2-agonists in patients with infection, but that we cannot expect these drugs to be prophylaxis against autotissue injuries whose pathogenesis includes activation of neutrophils. ⋯ Neutrophils are involved in the antibacterial host defense system and autotissue injury. We found that clinically relevant concentrations of clonidine and dexmedetomidine do not affect chemotaxis, phagocytosis, or superoxide production by human neutrophils. These findings indicate that it may not be necessary to take special care in using alpha2-agonists in patients with infection, sepsis, or systemic inflammation.
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Anesthesia and analgesia · Feb 1999
Comparative StudyChanges in maternal middle cerebral artery blood flow velocity associated with general anesthesia in severe preeclampsia.
In women with severe preeclampsia, significant increases in mean arterial pressures (MAP) are common after rapid induction of general anesthesia (GA) and tracheal intubation. The objectives of this prospective study were to assess the effects of the rapid induction-intubation technique on middle cerebral artery (MCA) flow velocity in severe preeclampsia and to examine the correlation between mean MCA flow velocity (Vm) and MAP. Eight women with severe preeclampsia (study group) and six normotensive women at term (control group) scheduled to undergo cesarean section under GA were studied. Before induction, patients in the study group received i.v. labetalol in divided doses to lower diastolic pressures to <100 mm Hg. Anesthesia was induced with pentothal 4-5 mg/kg, followed by succinylcholine 1.5 mg/kg to facilitate tracheal intubation. A transcranial Doppler was used to measure Vm. Both Vm and MAP were recorded before induction and every minute for 6 min after intubation. In the study group, after the administration of labetalol, MAP decreased from 129 +/- 9 to 113 +/- 9 mm Hg (P < 0.05), and Vm decreased from 59 +/- 11 to 54 +/- 10 cm/s (P < 0.05). After intubation, MAP increased from 113 +/- 9 to 134 +/- 5 mm Hg (P < 0.001), and Vm increased from 54 +/- 10 to 70 +/- 10 cm/s (P < 0.001). In the control group, while MAP increased significantly from 89 +/- 6 to 96 +/- 4 mm Hg (P < 0.05) after intubation, the concurrent increase in Vm from 49 +/- 5 to 54 +/- 7 cm/s was not significant. There was a significant positive pooled correlation between Vm and MAP (r = 0.5, P < 0.0006) in the study group but not in the control group (r = 0.24). After induction and intubation, both Vm and MAP values were significantly increased in the study group patients at all observation points compared with the control group patients. The findings indicate that Vm increases significantly after rapid-sequence induction of GA and tracheal intubation in women with severe preeclampsia, and there seems to be a direct relationship between MAP and Vm. ⋯ In women with severe preeclampsia, rapid-sequence induction of general anesthesia and tracheal intubation can cause severe hypertension. Our results indicate that the increase in blood pressure is associated with a significant increase in maternal cerebral blood flow velocity and that there is a significant correlation between these two variables.
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Anesthesia and analgesia · Feb 1999
Comparative StudyCraniotomy procedures are associated with less analgesic requirements than other surgical procedures.
The conventional wisdom that neurosurgical patients experience minimal postoperative pain and require little analgesia has been challenged. To address this, we reviewed our anesthesia and postanesthesia care unit (PACU) records for 1995 and compared pain management in patients undergoing major intracranial and selected extracranial procedures. We recorded patient weight, operative time, time in the PACU, intraoperative and postoperative opioid use, PACU pain scores, and level of consciousness in patients who had undergone open fixation of mandible or maxilla (Group E), clipping of aneurysms or excision of tumors (Group I), or lumbar laminectomy (Group L). Group I (n = 78) patients received less fentanyl in the operating room (0.016 microg x kg(-1) x min(-1) versus 0.023 microg x kg(-1) x min(-1) for Group E [n = 134] and 0.023 microg x kg(-1) x min(-1) for Group L [n = 21]; P < 0.05), received less morphine in the PACU (0.0004 vs 0.0013 vs 0.0015 mg kg(-1) x min(-1); P < 0.005), reported lower pain scores (0.76 vs 2.5 vs 2.4; P < 0.05), and spent less time in the PACU (89.5 vs 109 vs 105 min; P < 0.05) than Group E or L patients. Our results were similar when only patients with Glasgow Coma Scale scores > or = 14 were used in a subset analysis. We conclude that patients suffer less pain and use fewer opioids in the PACU after intracranial surgery than after facial reconstruction or lumbar laminectomy. Our results confirm that the average craniotomy patient has less postoperative pain than patients who undergo other surgical procedures, although patients who undergo frontal craniotomy may require more aggressive pain management. ⋯ This study compares the pain report and analgesic use in patients after intracranial versus extracranial surgery. The results confirm the commonly held but recently challenged belief that neurosurgery patients suffer less pain postoperatively than other patients. In this study, we found that most patients report minimal pain after intracranial surgery but that a small subset of patients, many of whom have undergone frontal craniotomies, require aggressive treatment of postoperative pain.
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Anesthesia and analgesia · Feb 1999
Drug therapy before coronary artery surgery: nitrates are independent predictors of mortality and beta-adrenergic blockers predict survival.
We conducted this study to evaluate whether there is an association between preoperative drug therapy and in-hospital mortality in patients undergoing coronary artery graft surgery. We collected data on 1593 consecutive patients undergoing coronary artery surgery. The relative risk of in-hospital mortality was determined by logistic regression with in-hospital mortality as the dependent variable, and independent variables that included known risk factors and preoperative cardioactive or antithrombotic drug treatment, i.e., age; left ventricular function; left main coronary artery disease; urgent priority; gender; previous cardiac surgery; concurrent cardiovascular surgery; chronic lung disease; creatinine concentration; hemoglobin concentration; diabetes; hypertension; cerebrovascular disease; recent myocardial infarction; prior vascular surgery; number of arteries bypassed; and regular daily treatment with beta-blockers, aspirin within 5 days, calcium antagonists, angiotensin converting enzyme (ACE) inhibitors, digoxin, or warfarin. In-hospital mortality was 3.3%. The relative risk of in-hospital mortality (with 95% confidence intervals of the relative risk) associated with the following drug treatments was: nitrates 3.8 (1.5-9.6), beta-blockers 0.4 (0.2-0.8), aspirin within 5 days 1.0 (0.5-1.9), calcium antagonists 1.1 (0.6-2.1), ACE inhibitors 0.8 (0.4-1.5), digoxin 0.7 (0.2-1.8), and warfarin 0.3 (0.1-1.6). We conclude that in-hospital mortality is positively associated with preoperative nitrate therapy and negatively associated with beta-adrenergic blocker therapy. A significant association between in-hospital mortality and the preoperative use of calcium antagonists, ACE inhibitors, aspirin, digoxin, and warfarin was not confirmed. ⋯ We examined the association between common drug treatments for ischemic heart disease and short-term survival after cardiac surgery using a statistical method to adjust for patients' preoperative medical condition. Death after surgery was more likely after nitrate therapy and less likely after beta-blocker therapy.
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Anesthesia and analgesia · Feb 1999
No risk of metal toxicity in combined spinal-epidural anesthesia.
Using the single level needle-through-needle technique for combined spinal-epidural anesthesia (CSE) may introduce very fine metal particles abraded by the spinal needle from the inner ground edge of the Tuohy needle into the patient. Either the local anesthetic administered epidurally or the peridural catheter may also pass intrathecally through the hole in the dura made by the spinal needle. To examine these concerns, the needle-through-needle technique was simulated in an in vitro model (18-gauge Tuohy needle; 27- or 29-gauge Quincke needle). The presence of abraded metal particles was identified by atomic absorption spectrography (AAS). The needles were then examined under an electron microscope. Metal particles could not be identified by using AAS in the needle-through-needle technique after normal clinical use, nor could traces of use be revealed by using an electron microscope to examine the Tuohy needle. With intentionally rough handling and caudal orientation of the spinal needle tip, minimal scratches could be seen by using an electron microscope, but there were no metal particles detected by AAS. In an anatomical preparation, the possible passage of the epidural catheter anesthetic through the dural puncture hole into the cerebrospinal fluid compartment was investigated endoscopically. Neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy. We conclude that the needle-through-needle-technique is an acceptable way of performing CSE anesthesia. Endangering the patient by an unintentionally intrathecal misplacement of the epidural catheter seems to be very unlikely based on our in vitro model if small spinal needles (27- or 29-gauge) are used. ⋯ Atomic absorption spectrography shows no contamination of the intrathecal compartment by abraded metal particles from the Tuohy needle by combined spinal-epidural anesthesia with the needle-through-needle technique. In vitro, neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy.