title: Spinal chloroprocaine solutions: density at 37 degrees C and pH titration.
abstract: The density and pH of a local anesthetic are important characteristics in its use as an intrathecal drug. Preservative- and antioxidant-free formulations of chloroprocaine are available and are being investigated for short-duration spinal anesthesia. In this study, we evaluated the pH and density (to 5 significant digits in g/mL, at 37.0 degrees C) of these new chloroprocaine formulations. In addition to plain 2% and 3% chloroprocaine and 2% lidocaine, mixed solutions of 2% chloroprocaine with epinephrine or with bicarbonate were evaluated. Density was also measured after water dilution and after increasing amounts of added dextrose. Chloroprocaine, 2% or 3%, is hyperbaric relative to cerebrospinal fluid (CSF) before any addition of dextrose (density 1.00123 g/mL and 1.00257 g/mL, respectively). When diluted with water, all the solutions are hypobaric relative to CSF (density <1.00028 g/mL). Plain 2% lidocaine is the only dextrose-free solution measured to be hypobaric (density 1.00004 g/mL). Bisulfite-free 2-chloroprocaine remains very acidic (pH <4.0), but the pH can be increased to more than 7.0 with a small amount of bicarbonate (0.25-0.33 mL/10 mL). The increased density of plain chloroprocaine makes it a useful hyperbaric spinal drug without the addition of dextrose.
  
  
  CONCLUSIONS
  Dextrose-free 2-chloroprocaine is hyperbaric relative to cerebrospinal fluid at 37 degrees C, and therefore can be used for spinal anesthesia without dextrose. Bisulfite-free 2-chloroprocaine remains very acidic (pH <4.0). The pH can be increased to more than 7.0 with a small amount of bicarbonate (0.25-0.33 mL/10 mL).
authors.affiliation: From the Department of Anesthesiology, Virginia Mason Medical Center, Seattle, Washington.
authors.forename: Kimberly B
authors.initials: KB
authors.lastname: Na
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Kopacz
mesh_terms: D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000737:chemistry*; D004355:Drug Stability; D004837:Epinephrine / Q000737:chemistry; D005947:Glucose / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D019999:Pharmaceutical Solutions; D011343:Procaine / Q000031:analogs & derivatives* / Q000737:chemistry*; D017693:Sodium Bicarbonate / Q000737:chemistry; D013696:Temperature
chemical_list: D000779:Anesthetics, Local; D019999:Pharmaceutical Solutions; D011343:Procaine; C004616:chloroprocaine; D017693:Sodium Bicarbonate; D005947:Glucose; D004837:Epinephrine