Patient Safety Tip
of the Week
December 4, 2012
Unintentional
Perioperative Hypothermia: A New Twist
When we came across
one of the Pennsylvania Patient Safety Authority’s excellent articles a few
years ago on unintentional perioperative hypothermia (PPSA
2008) we debated whether to do a column on it. Yes we know that avoidance
of hypothermia is a SCIP measure and it is important. But it just didn’t sound
like a topic we thought the majority of our readers would be interested in.
But we’ve
subsequently seen a few cases of unintentional perioperative hypothermia with a
new twist and there just happened to be a new article on this unusual
phenomenon (Ryan
2012). Specifically, there appears to be a syndrome related to cases (most
often obstetrical) in which spinal anesthesia with morphine is used and
patients develop hypothermia with paradoxical sweating. Though most
cases in the literature have followed cesarean sections, the case described by
Ryan et al. was in a patient who underwent a knee arthroplasty. Spinal
anesthesia was used with 11 mg of isobaric 0.5% bupivacaine, 15 micrograms of
fentanyl, and 150 micrograms of morphine. The patient’s temperature reached a
low point of 33.6 degrees C four hours after surgery, though at times her
temperature could not be recorded by any route. Despite the hypothermia she
felt hot and was diaphoretic without shivering. Warming efforts using forced
air warming blankets, infusion of warmed intravenous fluids, and hourly bladder
irrigation with warm saline were not successful in elevating her temperature.
But a quick literature search by the authors showed the syndrome often
responds to benzodiazepines and their patient rapidly became normothermic
after receiving a small sublingual dose (0.5 mg) of lorazepam. The authors go
on to discuss the cases in the literature and the current theory of the pathogenesis
of this syndrome. The theory is that enough of the morphine ascends in the
subarachnoid space to reach the hypothalamus where it interacts with receptors
important in thermoregulation. Essentially this leads to alteration of the
hypothalamic thermoregulatory set point causing the body to feel hot and
sweat in attempt to adapt to heat. Benzodiazepine receptors are also found in
the hypothalamus and are probably also involved in thermoregulation.
In at least 2 cases
hypothermia after intrathecal morphine has improved promptly after
administration of naloxone. In one case (Sayyid
2003) the patient’s temperature had dropped to 33.6 degrees C after a
cesarean section and the patient was sweating excessively despite the
hypothermia. She also had nausea, vomiting, pruritis and some sedation.
Following naloxone administration all the above symptoms disappeared and she
developed shivering and cessation of sweating concomitant with rising body
temperature.
In the other case (Mangus 2011) a
patient developed hypothermia unresponsive to usual warming measures several
hours after a cesarean section in which she received intrathecal morphine.
Severe pruritis and lethargy were also present. Naloxone was administered
intravenously in incremental doses and her temperature began to rise within 5
minutes. The pruritis and lethargy also improved and her pain control was never
compromised.
Hess et al reported
on 14 patients who developed hypothermia following cesarean sections in which
they had received spinal anesthesia with bupivacaine, morphine and fentanyl (Hess
2005). All had diaphoresis and felt hot. Four of the 14 were given
lorazepam and had prompt resolution of symptoms and rapid increase in
temperature. The remainder, who received conventional management of
hypothermia, were hypothermic and symptomatic for 6 hours on average. The
authors subsequently observed 100 consecutive patients and found 6% developed
symptomatic hypothermia lasting for several hours.
There is some evidence suggesting that this phenomenon might be dose-related. In a randomized controlled trial Hui and colleagues randomized patients undergoing elective cesarean section to receive either 150 micrograms of morphine or normal saline along with the bupivacaine in their spinal anesthesia (Hui 2006). They found that both groups developed hypothermia but that the maximum decrease in temperature was greater in the morphine group and of longer duration. This suggests that even a low dose of morphine may intensify the hypothermic effect of spinal anesthesia. However, they point out that many of the cases in the literature had much higher doses of morphine. In fact, they note that larger doses are avoided because they are often associated with nausea, vomiting, pruritis and shivering. Note that nausea, vomiting and pruritis were prominent in the cases described by Mangus and Sayyid.
Interestingly, this
phenomenon receives little or no attention in most of the major guidelines on
perioperative hypothermia (ASPAN
2010, PPSA
2007, NICE
2008, AORN
2007 and AORN
2013) though the NICE guideline specifically excludes pregnant women.
The importance of these
cases is twofold. First, you may want to limit the dose of intrathecal morphine
used. Second, you need to amend your hypothermia management protocols to take
this phenomenon into account. Specifically there should be a prompt to
consider the phenomenon if the expected improvement in hypothermia is not
occurring within a reasonable amount of time after conventional warming
procedures have been instituted. Perhaps even a prompt at the beginning of your
protocol to look for signs you would not expect with hypothermia (i.e.
sweating, hot feeling, vasodilation) might suggest this unusual etiology for
the hypothermia. The presence of nausea and pruritis might be an additional
clue. In either case the prompt should remind you to consider a trial of either
low dose benzodiazepine or naloxone.
You probably should
have a formal protocol you follow for prevention and management of
perioperative hypothermia. Use one of the above mentioned guidelines to start
with. Another recent article (Ford
2012) provides some good case scenarios to help you choose when and how you
might intervene. But make sure that whatever protocol you choose you add that
prompt we noted above to at least consider the possibility of the
morphine-induced syndrome because its management requires additional
considerations.
Update: See
our January 23, 2018 Patient Safety Tip of the Week “Unintentional
Hypothermia Back in Focus”
References:
PPSA (Pennsylvania
Patient Safety Authority). Prevention of Inadvertent Perioperative Hypothermia.
Pa Patient Saf Advis 2008; 5(2): 44-52
http://patientsafetyauthority.org/ADVISORIES/AdvisoryLibrary/2008/Jun5(2)/Pages/44.aspx
Ryan KF, Price JW, Warriner
CB, Choi PT. Persistent hypothermia after intrathecal morphine: case report and
literature review. Can J Anesth 2012; 59: 384-388
http://www.springerlink.com/content/w05129787067346h/
Mangus DB, Neumann
M, Patchin R. Naloxone reversal of hypothermia following intrathecal morphine
for cesarean delivery, a case report. Society for Obstetric Anesthesia and
Perinatology 2011; SOAP 2011 Abstract
#201
http://soap.org/display_2011_abstract.php?id=201
Sayyid SS, Jabbour
DG, Baraka AS. Hypothermia and Excessive Sweating Following Intrathecal
Morphine in a Parturient Undergoing Cesarean Delivery. Reg Anesth Pain Med
2003; 28(2): 140-143
Hess PE, Snowman CE,
Wang J. Hypothermia after cesarean delivery and its reversal with lorazepam.
Int J Obstet Anesth 2005; 14(4): 279-283
http://www.obstetanesthesia.com/article/S0959-289X%2805%2900033-6/abstract
Hui C-K, Huang C-H,
Lin C-J, et al. A randomised double-blind controlled study evaluating the
hypothermic effect of 150 μg morphine during spinal anaesthesia for Caesarean section. Anesthesia 2006; 61(1): 29-31
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2044.2005.04466.x/full
Hopper VD, et al.
ASPAN’s Evidence-Based Clinical Practice Guideline for the Promotion of
Perioperative Normothermia: Second Edition. Journal of PeriAnesthesia Nursing
2010; 25(6): 346-365
AORN Recommended
Practices Committee. Recommended practices for the prevention of unplanned
perioperative hypothermia. AORN J 2007; 85(5): 972-988
http://www.aornjournal.org/article/S0001-2092%2807%2900048-8/fulltext
AORN. Prevention of
Hypothermia. In: Perioperative Standards and Recommended Practices. Denver, CO:
AORN, Inc; 2013
NICE. Perioperative hypothermia (inadvertent): the management of inadvertent
perioperative hypothermia in adults. NICE Clinical Guideline 29. London:
National Institute for Health and Clinical Excellence, 2008
http://guidance.nice.org.uk/CG65/NICEGuidance/pdf/English
Quick reference
guide
http://guidance.nice.org.uk/CG65/QuickRefGuide/pdf/English
Ford D. How Would
You Warm This Patient? Use these 6 case scenarios to determine which warming
methods you'd choose. Outpatient Surgery Magazine 2012; November 2012
http://www.outpatientsurgery.net/issues/2012/11/how-would-you-warm-this-patient
Print PDF
version
http://www.patientsafetysolutions.com/