Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Clinical TrialThe clinical relevance of embolic events detected by transesophageal echocardiography during cemented total hip arthroplasty: a randomized clinical trial.
The first aim of this prospective clinical study was to characterize the relationship between embolic events observed during cemented total hip arthroplasty using transesophageal echocardiography (TEE), and changes in cardiopulmonary function. The second aim was to assess the efficiency of a modified cementing technique that was developed to reduce the risk of embolism. The modification consists in a vacuum drainage placed in the proximal femur to reduce the increase of intramedullary pressure during insertion of the prosthesis. One hundred twenty patients were randomized into two groups. Group 1 received a total hip arthroplasty cemented conventionally, whereas Group 2 was cemented with the modified technique. Continuous TEE, hemodynamic monitoring, and blood gas analysis were done during the perioperative period. Severe embolic events were imaged during the insertion of the femoral component and the reduction of the hip joint. Embolism occurred in 93.3% of patients operated on with the conventional cementing technique, compared with 13.3% of patients operated on with the modified technique (P < 0.05). Intraoperative shunt values during insertion of the femoral component increased from 8.2% to 10.3% (P < 0.05) in Group 1 patients, whereas there was no significant change in Group 2 patients. We observed no clinical signs of fat embolism syndrome in any study patient. The results of the study indicate that embolic events observed using TEE can cause increased pulmonary shunt values during hip arthroplasty, especially in patients with systemic disease (ASA physical status III). The modified surgical technique effectively reduced the incidence of embolization during cemented hip arthroplasty. ⋯ Use of conventional cementing techniques is associated with echocardiographic evidence of embolism in 93% of patients and with a significant increase in pulmonary shunting. The incidence of embolism and change in shunting are reduced with a modified cementing technique that limits increases in intramedullary pressure.
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Anesthesia and analgesia · Jan 2001
Comparative StudyCardiac resuscitation after incremental overdosage with lidocaine, bupivacaine, levobupivacaine, and ropivacaine in anesthetized dogs.
There is no information comparing the ability to reverse the cardiotoxic effects associated with incremental overdosage of bupivacaine (BUP) to levobupivacaine (LBUP), ropivacaine (ROP), or lidocaine (LIDO). Open-chest dogs were randomized to receive incremental escalating infusions of BUP, LBUP, ROP, and LIDO to the point of cardiovascular collapse (mean arterial pressure [MAP] < or = 45 mm Hg). Hypotension and arrhythmias were treated with epinephrine, open-chest massage, and advanced cardiac life support protocols, respectively. Outcomes were defined as the following: successful (stable rhythm and MAP > or = 55 mm Hg for 20 min), successful with continued therapy (stable rhythm and MAP <55 mm Hg after 20 min), or death. Continued therapy was required in 86% of LIDO dogs compared with only 10%-30% of the other dogs (P < 0.002). Mortality from BUP, LBUP, ROP, and LIDO was 50%, 30%, 10%, and 0%, respectively. Myocardial depression was primarily responsible for the profound hypotension, as the occurrence of lethal arrhythmias preceding resuscitation was not different among local anesthetics. Epinephrine-induced ventricular fibrillation occurred more frequently in BUP-intoxicated dogs than in dogs given LIDO or ROP (P < 0.05). The unbound plasma concentrations at collapse were larger for ROP, 19.8 microg/mL (10-39 microg/mL), compared with BUP, 5.7 microg/mL (3-11 microg/mL); whereas the concentrations of LBUP, 9.4 microg/mL (5-18 microg/mL) and BUP were not significantly different from each other. ⋯ There were consistent differences among the local anesthetics, the sum of which suggests that larger doses and blood concentrations of ropivacaine (ROP) and lidocaine will be tolerated as compared with bupivacaine (BUP) and levobupivacaine (LBUP). Lidocaine intoxication results in myocardial depression from which resuscitation is consistently successful but will require continuing drug support. After BUP, LBUP, or ROP, resuscitation is not always successful, and the administration of epinephrine may lead to severe arrhythmias. The unbound plasma concentrations at collapse were larger for ROP compared with BUP, whereas the concentrations of LBUP and BUP were not significantly different from each other. Furthermore, larger plasma concentrations of ROP than BUP are present after resuscitation, suggesting a wider margin of safety when large volumes and large concentrations are used to establish upper or lower extremity nerve blocks for surgical anesthesia and during long-term infusions for pain management.
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Anesthesia and analgesia · Jan 2001
Clinical TrialJejunal mucosal perfusion is well maintained during mild hypothermic cardiopulmonary bypass in humans.
In the present study, the effects of mild hypothermic (34 degrees C) cardiopulmonary bypass (CPB) on jejunal mucosal perfusion (JMP), gastric tonometry, splanchnic lactate, and oxygen extraction were studied in low-risk cardiac surgical patients (n = 10), anesthetized and managed according to clinical routine. JMP was assessed by endoluminal laser Doppler flowmetry. Patients were studied during seven 10-min measurement periods before, during, and 1 h after the end of CPB. Splanchnic oxygen extraction increased during hypothermia and particularly during rewarming and warm CPB. JMP increased during hypothermia (26%), rewarming (31%), and warm CPB (38%) and was higher 1 h after CPB (42%), compared with pre-CPB control. The gastric-arterial PCO(2) difference was slightly increased (range 0.04-2.26 kPa) during rewarming and warm CPB as well as 1 h after CPB, indicating a mismatch between gastric mucosal oxygen delivery and demand. None of the patients produced lactate during CPB. We conclude that jejunal mucosal perfusion appears well preserved during CPB and moderate (34 degrees C) hypothermia; this finding is in contrast to previous studies showing gastric mucosal hypoperfusion during CPB. ⋯ Jejunal mucosal perfusion increases during mild hypothermic cardiopulmonary bypass (CPB). Intestinal laser Doppler flowmetry, gastric tonometry, and measurements of splanchnic lactate extraction could not reveal a local or global splanchnic ischemia during or after CPB. A mismatch between splanchnic oxygen delivery and demand was seen, particularly during rewarming and warm CPB.
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Anesthesia and analgesia · Jan 2001
Clinical TrialIntramuscular versus surface electromyography of the diaphragm for determining neuromuscular blockade.
We determined the neuromuscular blockade of 0.2 mg. kg(-1) mivacurium at the diaphragm by using two new methods of electromyographic (EMG) monitoring and compared it with acceleromyography of the orbicularis oculi (OO) and the corrugator supercilii (CS) muscle. After the induction of anesthesia in 15 patients undergoing gynecologic laparoscopic surgery, evoked EMG responses at the diaphragm were obtained by using skin electrodes at the back of the patient, placed lateral to T12/L1 or L1/L2, and a laparoscopically applied wire electrode inserted into the dorsolateral portion of the diaphragm. Acceleromyography at the right OO and the left CS was performed. ⋯ We showed a shorter onset and clinical duration at the diaphragm in comparison with CS and OO. Two methods of EMG of the diaphragm correlated well and showed good comparability. The novel method of surface diaphragmatic EMG at the patient's back may be useful during routine clinical anesthesia.
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Anesthesia and analgesia · Jan 2001
Clinical TrialAn evaluation of the brachial plexus block at the humeral canal using a neurostimulator (1417 patients): the efficacy, safety, and predictive criteria of failure.
To evaluate the efficacy and safety of the multiple peripheral nerve block technique at the humeral canal (humeral block) with the use of a neurostimulator, we prospectively studied 1417 patients undergoing upper limb surgery with a brachial plexus block at the humeral canal (1468 blocks). The success rate (defined as sensory block [in all nerve distributions] and/or the absence of another anesthetic technique required to allow surgery) was 95%. The threshold of minimal stimulation used to locate each nerve before injecting the anesthetic solution was the unique predictive factor for identified failure. For the median nerve, the threshold was 0.8 mA with a relative risk of failure (RRf: relative risk evaluated by series of Taylor with a 95% confidence interval) = 1.49 (P = 0.04), for the radial nerve the threshold was 0.6 mA (RRf 1.3, P = 0.02), and 0.7 mA for the ulnar nerve (RRf 1.36, P = 0.04). For any equal or higher stimulation level, the risk of failure of the humeral block increased. For the musculocutaneous nerve, we did not observe a significant stimulation threshold for the risk of failure; although beyond 0.7 mA, the RRf was always more than 1.3. Adverse events occurred in 7% of all cases and were usually minor (nausea/vomiting, anxiety, local pain). Our study provides supplementary information on the efficacy and safety of this technique. Stimulation thresholds are clinically identified for the first time as the main factor linked to the failure of a technique using a neurostimulator. We conclude that the humeral block is a reliable peripheral block allowing good success rates results with minor complications, which can be used as an alternative to the axillary block. ⋯ We prospectively evaluated the feasibility and the factors causing failure of a peripheral nerve block technique (humeral block) using neurostimulation in a large number of patients. The importance of the level of stimulation for the success of the block was evaluated for the first time.