Articles: anesthetics.
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Experiments were performed in a rat sciatic nerve preparation to determine the characteristics of nerve blocks produced by a combination of commercially available solutions of bupivacaine and chloroprocaine. A mixture of equal parts of commercially available chloroprocaine 2% and bupivacaine 0.5% resulted in a nerve blockade with characteristics of a chloroprocaine block. Changing the pH value of this mixture from 3.60 to 5.56 changed these characteristics to a blockade resembling that produced by bupivacaine. It is concluded that the nerve blockades obtained by mixing commercially available solutions of local anesthetics are unpredictable and may depend on a number of factors which include not only the types of drugs but the pH of the mixture.
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A 61-year-old woman experienced a cardiopulmonary arrest immediately after the retrobulbar injection of a mixture of 2 ml of 0.5% bupivacaine HCl, 2% mepivacaine HCl, and hyaluronidase. The patient was immediately resuscitated but remained unconscious for a total of 20 minutes. All neurologic deficits resolved completely over the two hours following the cardiopulmonary arrest and no adverse sequelae were noted. We assumed that this cardiopulmonary arrest was precipitated by the local anesthetic being transported via retrograde flow through the ophthalmic artery and then by antegrade flow through the internal carotid artery to the thalamus and other midbrain structures.
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Severe cyanosis resulting from acquired methemoglobinemia after application of a topical anesthetic, Cetacaine spray, occurred in a 37-year-old patient following bronchoscopy for postoperative atelectasis. Response to methylene blue therapy was dramatic and complete. Attention is drawn to a dangerous adverse effect of this commonly used topical anesthetic agent.