title: Air versus saline in the loss of resistance technique for identification of the epidural space.
abstract: BACKGROUND
  The success of epidural anaesthesia depends on correct identification of the epidural space. For several decades, the decision of whether to use air or physiological saline during the loss of resistance technique for identification of the epidural space has been governed by the personal experience of the anaesthesiologist. Epidural block remains one of the main regional anaesthesia techniques. It is used for surgical anaesthesia, obstetrical analgesia, postoperative analgesia and treatment of chronic pain and as a complement to general anaesthesia. The sensation felt by the anaesthesiologist from the syringe plunger with loss of resistance is different when air is compared with saline (fluid). Frequently fluid allows a rapid change from resistance to non-resistance and increased movement of the plunger. However, the ideal technique for identification of the epidural space remains unclear.
  
  
  OBJECTIVE
  • To evaluate the efficacy and safety of both air and saline in the loss of resistance technique for identification of the epidural space.• To evaluate complications related to the air or saline injected.
  
  
  METHODS
  We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 9), MEDLINE, EMBASE and the Latin American and Caribbean Health Science Information Database (LILACS) (from inception to September 2013). We applied no language restrictions. The date of the most recent search was 7 September 2013.
  
  
  METHODS
  We included randomized controlled trials (RCTs) and quasi-randomized controlled trials (quasi-RCTs) on air and saline in the loss of resistance technique for identification of the epidural space.
  
  
  METHODS
  Two review authors independently assessed trial quality and extracted data.
  
  
  RESULTS
  We included in the review seven studies with a total of 852 participants. The methodological quality of the included studies was generally ranked as showing low risk of bias in most domains, with the exception of one study, which did not mask participants. We were able to include data from 838 participants in the meta-analysis. We found no statistically significant differences between participants receiving air and those given saline in any of the outcomes evaluated: inability to locate the epidural space (three trials, 619 participants) (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.33 to 2.31, low-quality evidence); accidental intravascular catheter placement (two trials, 223 participants) (RR 0.90, 95% CI 0.33 to 2.45, low-quality evidence); accidental subarachnoid catheter placement (four trials, 682 participants) (RR 2.95, 95% CI 0.12 to 71.90, low-quality evidence); combined spinal epidural failure (two trials, 400 participants) (RR 0.98, 95% CI 0.44 to 2.18, low-quality evidence); unblocked segments (five studies, 423 participants) (RR 1.66, 95% CI 0.72 to 3.85); and pain measured by VAS (two studies, 395 participants) (mean difference (MD) -0.09, 95% CI -0.37 to 0.18). With regard to adverse effects, we found no statistically significant differences between participants receiving air and those given saline in the occurrence of paraesthesias (three trials, 572 participants) (RR 0.89, 95% CI 0.69 to 1.15); difficulty in advancing the catheter (two trials, 227 participants) (RR 0.91, 95% CI 0.32 to 2.56); catheter replacement (two trials, 501 participants) (RR 0.69, 95% CI 0.26 to 1.83); and postdural puncture headache (one trial, 110 participants) (RR 0.83, 95% CI 0.12 to 5.71).
  
  
  CONCLUSIONS
  Low-quality evidence shows that results do not differ between air and saline in terms of the loss of resistance technique for identification of the epidural space and reduction of complications. Applicability might be compromised, as most of the results described in this review were obtained from parturient patients. This review underlines the need to conduct well-designed trials in this field.
authors.affiliation: Department of Anaesthesiology, Hospital Sírio Libanês, São Paulo Serviços Médicos de Anestesia, Rua Moraes de Barros, 854 ap.41, São Paulo, São Paulo, Brazil, 04614-001.
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Antibas
authors.forename: Paulo
authors.initials: P
authors.lastname: do Nascimento Junior
authors.forename: Leandro G
authors.initials: LG
authors.lastname: Braz
authors.forename: João
authors.initials: J
authors.lastname: Vitor Pereira Doles
authors.forename: Norma S P
authors.initials: NS
authors.lastname: Módolo
authors.forename: Regina
authors.initials: R
authors.lastname: El Dib
mesh_terms: D000328:Adult; D000388:Air; D000767:Anesthesia, Epidural / Q000295:instrumentation / Q000379:methods*; D002404:Catheterization / Q000009:adverse effects / Q000295:instrumentation; D004548:Elasticity / Q000502:physiology; D004824:Epidural Space / Q000033:anatomy & histology*; D006801:Humans; D017843:Ligamentum Flavum / Q000502:physiology; D019300:Medical Errors / Q000706:statistics & numerical data; D010292:Paresthesia / Q000209:etiology; D051299:Post-Dural Puncture Headache / Q000209:etiology; D011312:Pressure; D016032:Randomized Controlled Trials as Topic; D012965:Sodium Chloride / Q000008:administration & dosage
chemical_list: D012965:Sodium Chloride