AANA Journal Course 5

AANA Journal Course 5

Update for nurse anesthetists *6 CE Credits

Epidural analgesia using loss of resistance with air
versus saline: Does it make a difference? Should we
reevaluate our practice?

CDR David Norman, CRNA, MSN, NC, USN
Chesapeake, Virginia

The choice of using air or saline in epidural syringes during laboring parturients. Results are mixed. However, they seem
the loss-of-resistance technique, for identifying the epidural to indicate that the use of saline for the loss-of-resistance
space, has been based largely on personal preference of the may result in more rapid and satisfactory quality of pain relief
anesthesia provider. A survey of practice in the United King- in laboring parturients.
dom, thought to be similar to practice in the United States,
revealed that the majority of anesthesia providers use air. Current anesthesia literature suggests using saline with an
air bubble in the loss-of-resistance syringe. Many anesthesia
Case reports have appeared in the literature suggesting training programs continue to teach the use of air, saline, and
that air may be harmful to patients or, at the very least, saline with an air bubble. Further studies may help to deter-
impede the onset and quality of epidural analgesia. Two stud- mine whether there is a scientific or safety basis for using air
ies have evaluated air vs saline to determine whether one vs saline.
may lead to more rapid or better quality epidural analgesia in Key words: Air, analgesia, epidural, loss of resistance, saline.

Objectives LOR technique, 2 to 5 mL of air or saline is drawn into

At the completion of this course, the reader should be the syringe, and continuous or intermittent pressure
able to:
is applied to the plunger as the epidural needle is
1. Describe the 2 most common injected sub- advanced toward the epidural space.1 On entry into
stances used for the loss-of-resistance technique,
including their possible side effects. the epidural space, the syringe contents are injected

2. Identify the possible problems associated with due to a loss in resistance. Air and saline are the most
the use of air as the choice of injected substance.
widely used substances in the LOR technique
3. Identify the possible problems associated with syringe.1 Both are used commonly; the decision
the use of saline as the choice of injected sub- derives mostly from personal preference.1 The pur-
stance.
pose of this literature review is to examine our prac-
4. State why smaller volumes of the injected sub-
stance are preferable. tice and determine whether both air and saline are

5. Compare and contrast and choose the injected equally safe and efficacious or whether anesthesia
substance based on informed scientific rationale.
providers may need to consider changing the sub-
Introduction
stance used in their practice.
Epidural analgesia is a very popular method of pain
control for laboring parturients. The most common The incidence of backache (approximately 30%)
method for determining entry into the epidural space
is the loss-of-resistance (LOR) technique. During the and postdural puncture headaches (up to 50% in par-

turients experiencing an inadvertent dural puncture)

during an epidural insertion, are both considered
common.2,3 Such complications as permanent nerve

injury, systemic toxic effects of drugs, and spinal
hematomas, fortunately, are rare.2,3 However, addi-

* AANA Journal Course No. 23: The American Association of Nurse Anesthetists is accredited as a provider of continuing education in nursing by
the American Nurses Credentialing Center Commission on Accreditation. The AANA Journal course will consist of 6 successive articles, each with
objectives for the reader and sources for additional reading. At the conclusion of the 6-part series, a final examination will be printed in the AANA
Journal. Successful completion will yield the participant 6 CE credits (6 contact hours), code number: 25468, expiration date: July 31, 2004.

AANA Journal/December 2003/Vol. 71, No. 6 449

tional complications cited in the following case cesarean section after multiple attempts, and approxi-
reports are attributed by the authors to the use of air mately 20 mL of air were injected during these
injected during the LOR technique. attempts. After injection of 16 mL of 0.5% bupiva-
caine with 1:200,000 epinephrine, the patient’s respi-
In an early case report, the author attributed a uni- rations ceased, blood pressure dropped, and the
lateral epidural block in a 64-year-old man undergoing patient was intubated. The patient remained stu-
left-sided inguinal herniorrhaphy to 2 mL of air porous postoperatively. A CT scan revealed approxi-
injected during the LOR technique.4 In a second case, mately 25 mL of air in the parietofrontal cerebral cor-
using air in the LOR technique during the epidural tex. This appeared to resolve within 24 hours, and the
insertion in a laboring parturient resulted in inade- patient was discharged from the intensive care unit
quate analgesia and was cited by the author as a possi- within 72 hours.
ble explanation for the patient having unblocked seg-
ments. The presence of peridural air was confirmed by Another case report describes a 30-year-old par-
radiography during the postpartum period.5,6 turient at term desiring epidural analgesia.10 The LOR
technique with air was used during the insertion. The
Another case report describes a 58-year-old man insertion process, with the patient in the sitting posi-
with acute pancreatitis who was undergoing an tion, was described as uneventful with the “space
epidural block for pain control.7 The LOR technique entered easily.” Upon encountering the LOR, 5 mL of
was performed with air. Six attempts at 3 interverte- air was injected. The patient described an immediate
bral spaces were required before the successful identi- sense of severe back pain at the needle site that moved
fication of the epidural space and placement of the up the spine, resulting in a severe neck ache and,
catheter. Subcutaneous emphysema along the verte- finally, a severe bifrontal-temporal headache. The
bral column was confirmed by clinical assessment. A patient became very distressed (“became uncoopera-
computed tomography (CT) scan obtained 4 days tive and vociferously complaining that she was expe-
after the insertion confirmed the presence of peridural riencing the worst headache of her life”), and an
air bubbles. The authors stated that although there immediate CT scan was obtained to rule out cerebral
were no associated symptoms with the subcutaneous bleeding. The CT scan revealed approximately 5 mL
emphysema, it resolved slowly. of air in the intracranial subarachnoid space and basal
cisterns. Although no blood or cerebrospinal fluid was
One of two patient positions generally is selected encountered during the LOR technique, the symp-
for the insertion of an epidural. The decision to use toms described are classic responses to pneumoen-
the lateral, or sitting, position usually is based on cephalography air–related headaches. The patient was
provider preference. When the sitting position is returned to the labor suite, and her analgesic needs
selected, it must be noted that air injected into the were managed with intramuscular meperidine until
subarachnoid space will rise, resulting in a sudden her labor was deemed “failure to progress.” She then
and often severe headache. Before the invention of CT received a general anesthetic for a cesarean section.
scans, pneumoencephalograms were used for radi- Her surgical and anesthetic courses were uneventful.
ographic examination of the spine and ventricles of Her headache resolved fully within 24 hours.
the brain. During this procedure, air was injected
intentionally into the subarachnoid space at the lum- In a case describing the injection of an excessive
bar region, and radiographs were taken during the amount of air during the LOR technique, the author
ascent of the air into the cerebral ventricles. This cre- attributed the resulting transient paraplegia to the
ated a pneumocephalus, which resulted in a severe air.11 In this case, a 52-year-old woman with chronic
headache until the patient was positioned in a head- back pain was undergoing epidural analgesia. The
down position so the air would flow back through the insertion required 4 attempts, during which an esti-
subarachnoid space to the lumbar region, where it was mated 40 mL of air was injected. After the injection of
aspirated. 20 mL of 0.25% bupivacaine with 80 mg of methyl-
prednisolone plus 20 mL of normal saline, the needle
A case report of a 17-year-old parturient receiving was withdrawn. Eight hours after the injection, the
an epidural for labor, using the LOR technique with patient complained of persistent left leg numbness
air, describes inadvertent dural puncture with 4 mL of and weakness. A CT scan revealed a large amount of
air injected.8 The patient immediately reported a extradural air. Her symptoms resolved within 24
severe occipital headache. The epidural procedure was hours, and a CT scan 72 hours after the injection
repeated with an LOR using saline at the same inter- revealed that a substantial quantity of the extradural
space and was successful. It took 7 days for this air had been reabsorbed. The authors thought that her
patient’s headache to resolve. symptoms were a result of nerve root compression
due to the air. However, it should be noted that 20 mL
Pneumocephalus was described in a 25-year-old
parturient, “after many attempts” during an LOR tech-
nique using air.9 The epidural was placed for a

450 AANA Journal/December 2003/Vol. 71, No. 6

of the bupivacaine-methylprednisolone mixture also preceding case reports, she found that the incidence of
was injected into the same space. Since fluid is less paresthesias reduction was significant (from 49% to
compressible than air, might it also have contributed 29%) and that there were no complications.
to her symptoms?
One study found that the use of saline for the LOR
Nerve root compression also was described when technique resulted in the decrease of anesthetic
an epidural pump was used for the management of effect.16 This dilutional effect on the local anesthetic
cancer pain.12 This case is different from the preced- injected also resulted in increasing spread of the drug.
ing cases because the air was injected inadvertently
into the narcotic reservoir by the patient during self- Before the mid-to-late 1990s, many anesthesia text-
preparation. After a few days, the patient noted books described the use of “air or saline” during the
increasing back pain and bilateral hip flexor weak- LOR technique. Most did not cite a preference for one
ness. A CT scan revealed the presence of peridural air. or the other. However, since the late 1990s many of the
The air was aspirated, and the patient experienced leading authors describe the use of saline alone or
immediate relief. saline with an air bubble during the LOR technique.1-3
This transition likely is a result of the many case
Neurological damage was described in a case in reports cited in the literature.
which a patient received an epidural anesthetic for
extracorporeal shock wave lithotripsy.13 An LOR tech- Only a few studies have compared the use of air
nique with only 2 mL of air was used. Postoperatively, and saline during the LOR technique. One study with
the patient experienced severe pain in the lower back a sample of 142 parturients in labor, 71 in each of 2
and legs for 2 days that delayed her ambulation. She groups, sought to examine whether there was a differ-
also experienced tenderness along the lumbar spine ence between air and saline in the frequency of unac-
and bilateral limited leg mobility due to pain. A CT ceptable analgesia.1 The investigators found a lower
scan revealed air in the right lateral recesses of S1 and frequency of inadequate analgesia in the saline group
T12. Her pain and limited mobility improved during than in the air group.
the next 6 weeks. At 6 weeks she was able to return to
work but still experienced some backache and limited The aim of another study examining air vs saline for
motion. The authors felt that the gas gradient between the LOR technique was to determine whether there
the air bubbles and the tissue may impede or disturb was any difference in the onset, spread, or character of
the shock waves. They further recommend that air not the epidural analgesia in laboring parturients.17 The
be used during the LOR technique during epidural sample consisted of 50 parturients, 25 in the air group
insertion for extracorporeal shock wave lithotripsy. and 25 in the saline group. The air group experienced
an increased incidence of unblocked segments, but
An article reviewing the risks of air for the LOR there was no difference in the spread of analgesia.
technique describes one additional concern,14 the
occurrence of a venous air embolism. In addition to A third study examined air vs saline for the inci-
citing all of the aforementioned events (back pain, dence of paresthesias during epidural catheter inser-
headaches, paresthesias, and incomplete blocks) tion.18 The sample consisted of 67 parturients, 32 in
described in the case reports, the authors state that the air group and 35 in the saline group. The investi-
because the epidural anatomy is a rich plexus of veins, gators used 10 mL of air or saline during the LOR
the risk of injecting air intravascularly is present. technique. No significant difference was found
They cited 2 children and 1 man in whom air was between the groups in the incidence of paresthesias.
injected and rapid cardiac deterioration followed. The The authors stated that they found no significant dif-
authors stated that a patent foramen ovale may lead to ference in analgesia between groups and concluded
a potentially lethal outcome if a venous air embolism that the decision to use air or saline during the LOR
is produced from the injection of air during the LOR technique remains a personal choice.
technique.
Summary
Philip15 conducted a study in which she not only
used air during the LOR technique, but also then It is a conservative estimate that during the past 12 to
injected 10 mL of air after confirmation of entry to the 15 years, hundreds of thousands, if not more than a
epidural space. The purpose of this study was to million epidurals have been placed. With these num-
determine whether the injection of 10 mL of air before bers, the reported cases of complications attributed to
insertion of the epidural catheter might reduce the the injected substance are rare on a percentage basis.
incidence of paresthesias encountered during the In the majority of the case reports cited, the authors
insertion of the catheter. She used a sample of 132 attribute these side effects to air; the symptoms are
parturients, 63 who received 10 mL of air and 69 who transient and rarely life-threatening complications.
did not. In contrast with the events described in the The most current anesthesia literature seems to advo-
cate the use of saline rather than air.

Despite reluctance to change practice based on case

AANA Journal/December 2003/Vol. 71, No. 6 451

Table. Textbook chronology

Year Author Quote
1987 Shnider et al19
1988 Cousins and Bromage20 Loss-of-resistance technique with saline- (or air) filled syringe most commonly
1990 Brown21 used.

1992 Covino and Lambert22 We prefer the technique of loss of resistance, using an air-filled syringe.
1993 Shnider et al23
1994 Brown24 The preferred method of carrying out the loss-of-resistance technique includes
1996 Tetzlaff25 attaching a 3- to 5-mL glass syringe filled with 2 mL saline and a small (0.25
1997 Bernards26 mL) air bubble.
1998 Molnar and Pian-Smith27
1998 Cousins and Veering28 The most common method to identify the epidural space is the loss of
1999 Brown29 resistance technique…. Usually, a syringe containing saline or air is attached….
1999 Brown30
2000 Brown31 Loss-of-resistance technique with saline- (or air) filled syringe most commonly
used….
2001 Ellis32
2001 Bernards33 A 3 to 5 mL low resistance glass or plastic syringe is filled with a small (0.25
2002 Kleinman34 mL) air bubble.
2002 Rosen et al35
Whether to inject saline or air with the loss of resistance technique depends on
the preference of the practitioner.

A glass syringe filled with 2-3 mL saline and a small air bubble…

A glass or plastic loss-of-resistance syringe containing approximately 3 cc of
air or 3 cc of saline…

We prefer the technique of loss of resistance, using an air-filled syringe.

I prefer that the syringe contain both saline and a small (0.25 mL) compressible
bubble of air.

A 3-5 mL glass syringe is filled with 2 mL saline solution and a small (0.25 mL)
air bubble is added.

The preferred method of carrying out the loss-of-resistance technique includes
attaching a 3- to 5-mL glass syringe filled with 2 mL saline and a small (0.25
mL) air bubble.

The syringe is filled with 3 to 4 mL of air or 3 mL saline and 1 mL of air to
facilitate compression of the solution.

A glass syringe or a specially designed low resistance plastic syringe is filled
with 2-3 mL saline and a small (0.1-0.3 mL) air bubble.

A glass syringe filled with approximately 2 mL of fluid or air is attached to the
hub of the needle.

Loss-of-resistance technique with saline- (or air-) filled syringe most commonly
used.

reports, the case reports seem to share 3 common marily on case reports. Finally, the common theory
themes. The first is that the side effects reported seem behind the possibility of air as the cause of inadequate
to be related to the volume of air or saline injected. A or slow analgesia is that air actually impedes the
second is that air remains in the peridural area for not absorption of the local anesthesia molecules.1
just hours or a day or two as once thought; it often
remains for many days.7,11,13 This was confirmed by A literature review on this topic would be incom-
radiography. In light of this fact, relatively few studies plete without a review of what the leading anesthesia
have been conducted to effectively determine whether textbooks have taught during the past 10 to 15 years.
there really is an increased risk with air or whether A chronology with quotes from their description of
there exists a clinically significant scientific reason to the LOR technique is given in the Table.19-35
advocate the use of one substance over the other. Even
though there are just a few studies reported in the lit- Clearly, further studies may help determine
erature on this subject, it seems that multiple authors whether the use of air or saline leads to a more rapid
advocate the use of saline rather than air, based pri- onset and better quality of analgesia and a better
safety profile. Before making a premature conclusion
that air or saline is the cause of these complications, it

452 AANA Journal/December 2003/Vol. 71, No. 6

might also be helpful to examine the insertion skills of 20. Cousins M, Bromage PR. Epidural neural blockade. In: Cousins M,
the provider and the ease or difficulty of the insertion Bridenbaugh P, eds. Neural Blockade. 2nd ed. Philadelphia, Pa: JB
procedure.36 These 2 variables and others need to be Lippincott Co; 1988:324.
studied and excluded before we can be certain that the
injected substance is the cause of the aforementioned 21. Brown DL, Wedel, DJ. Introduction to regional anesthesia. In:
complications. Miller RD, ed. Anesthesia. 3rd ed. New York, NY: Churchill-Liv-
ingstone; 1990:1398.
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Reg Anesth. 1985;10:21-23. AUTHOR
CDR David Norman, CRNA, MSN, NC, USN, is on active duty in the
16. Iwama H. Injection volume of saline with loss of resistance Navy, assigned to the Naval School of Health Sciences at Portsmouth
method may affect the spread of epidural anesthesia [letter]. Anes- Naval Medical Center, Portsmouth, Va. He recently served as the clini-
thesiology. 1997;86:507-508. cal coordinator for the Navy Nurse Corps Anesthesia Program,
Portsmouth Va. Norman is a doctoral student at the Frances Payne
17. Valentine S, Jarvis A, Shutt L. Comparative study of the effects of Bolton School of Nursing, Case Western Reserve University, Cleveland,
air or saline to identify the extradural space. Br J Anaesth. 1991;66: Ohio.
224-227.
DISCLAIMER
18. Sarna M, Smith I, James J. Paraesthesia with lumbar epidural The material contained in this article and the views of this author in no
catheters. Anaesthesia. 1990;45:1077-1079. way represent the views of the US Naval Medical Center Portsmouth,
the US Navy, or the US Government.
19. Shidner SM, Levinson G, Ralston DH. Regional anesthesia for
labor and delivery. In: Shnider SM, Levinson G, eds. Anesthesia for
Obstetrics. 2nd ed. Baltimore, Md: Williams & Wilkins; 1987:114.

AANA Journal/December 2003/Vol. 71, No. 6 453