Patient Safety Tip
of the Week
January 23, 2018
Unintentional
Hypothermia Back in Focus
Our Patient Safety Tip of the Week for December 4, 2012 “Unintentional
Perioperative Hypothermia: A New Twist” discussed unintentional hypothermia
occurring during surgical procedures, primarily cesarean deliveries, performed
under spinal anesthesia using morphine. The “twist” was that some of these
patients had paradoxical sweating (or vasodilation or feeling “hot”) despite
profound hypothermia.
Three articles in the January 2018 issue of Anesthesia &
Analgesia discuss the issue of unintentional hypothermia in obstetrics. Using
an intestinal telemetric sensor, a rapid decrease in core temperature was
documented during cesarean delivery under spinal anesthesia (du
Toit 2018). Fifty percent of participants in this study became hypothermic.
Although the surgical procedure is typically of short duration, women
undergoing spinal anesthesia for cesarean delivery experience significant
hypothermic exposure and compromised
thermoregulation for several hours.
Participants reached their intestinal temperature nadir after
a median of 1 hour. The majority of participants
experienced a continued decrease in intestinal temperature after leaving the
operating room. Interestingly, despite the significant decrease in core
temperature, the median thermal comfort score remained zero (neutral) at all but
the late afternoon measurement time.
In another study, Munday and
colleagues found that a short period of preoperative warming is not effective
in preventing intraoperative temperature decline for women receiving
intrathecal morphine (Munday
2018). This was a prospective, single-blinded, randomized controlled
trial compared 20 minutes of forced air warming (plus intravenous fluid
warming) versus no active preoperative warming (plus intravenous fluid warming)
in 50 healthy American Society of Anesthesiologists graded II women receiving
intrathecal morphine as part of spinal anesthesia for elective cesarean
delivery.
Allen and Habib (Allen
2018), in their editorial accompanying the two new articles on
unintentional hypothermia, lament the relative lack of proven interventions to
prevent or treat hypothermia in obstetrical patients. They note that current core
temperature monitoring practices and temporary management guidelines will need
to be updated. They also emphasize the need to extend the duration of
temperature monitoring well beyond the early recovery period.
Interestingly, none of the 3 new articles even mentions the
phenomenon we highlighted in our Patient Safety Tip of the Week for December 4,
2012 “Unintentional
Perioperative Hypothermia: A New Twist”. 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 (Ryan 2012, Hess
2005). 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.
Hess et al had 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.
Another article (Giladi
2015) discussed the differential diagnosis of prolonged hypothermia
following cesarean delivery and concluded the patient likely had the syndrome
of hypothermia with paradoxical sweating induced by spinal anesthesia with
morphine.
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.
In at least 3 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. In another case profound hypothermia followed intrathecal
injection of an unintended high dose of morphine for a cesarean delivery (Kanazawa 2015).
Within 2 hours after completion of surgery, the patient’s axillary temperature
decreased to 35.0°C despite an ambient temperature of 25°C. Despite active
warming with a forced-air warming device, her temperature continued to drop to
34.0°C over the next 3 hours. The patient was not aware of hypothermia. In
fact, she felt hot and was perspiring profusely. After review of the anesthesia
record revealed that 1 mg of morphine had been injected intrathecally, 0.2 mg
of naloxone was administered intravenously over a 10-minute period. Soon after starting
the naloxone injection, the patient felt cold and demonstrated extensive
shivering, while her axillary temperature rapidly rose to 35.5°C over the next
hour. Nausea and respiratory depression also subsided thereafter.
Another article
demonstrated that atropine could stop the excessive sweating associated with
intrathecal morphine or fentanyl administration (Mazy
2016). Excessive sweating was observed in three cases among 217 consecutive
patients wo underwent lower limb orthopedic surgery
under spinal anesthesia using intrathecal morphine or fentanyl administration.
The sweating began about 3 hours after spinal injection. Atropine promptly
stopped the sweating in 3 cases, followed by slow rise in body temperature. The
Mazy article has an excellent discussion about the potential mechanisms. The delayed
onset was explained as the time elapsed until cephalad spread of morphine to
the hypothalamic opioid receptors involved in temperature regulation.
Admittedly, many of the patients in the 3 new articles were
said to have shivering, and sweating was not mentioned. Therefore, those
patients may have had different mechanisms responsible for the hypothermia than
the mechanism postulated in the Ryan and Hess articles. Nevertheless, it is
very important to recognize the hypothermia with paradoxical sweating
phenomenon since, as in the case described by Ryan, there may be prompt
resolution after a small sublingual
dose of lorazepam.
Perioperative
hypothermia can have serious adverse consequences, including increased risk of
surgical site infections, myocardial ischemia, prolongation of drug effects,
bleeding diatheses, shivering, pressure ulcers, poor patient satisfaction, and
increased economic effects due to things like increased length of stay (Hart 2011).
This excellent review of unintended perioperative hypothermia by Hart and
colleagues at the Ochsner Clinic does not mention the “hypothermia with
paradoxical sweating” phenomenon. Nor did it consider spinal anesthesia with
opioids as a risk factor for hypothermia.
Likewise, this
phenomenon also receives little or no attention in most of the major guidelines
and other resources on perioperative hypothermia (ASPAN
2010, PPSA 2008,
NICE 2008,
NICE
2017, AORN
2007, AORN
2013, AORN
2017).
But another study by Munday and colleagues (Munday 2017)
refutes the association between perioperative hypothermia and use of
intrathecal morphine. That study was a retrospective case controlled study of
patients undergoing spinal anesthesia for cesarean delivery, comparing 179 who received
intrathecal morphine and 179 without intrathecal morphine (control group). Administration
of intrathecal morphine (combined with intrathecal fentanyl and hyperbaric
bupivacaine) is standard care in their institution; therefore, the no morphine group
was selected first by identifying patients who, because of clinical reasons
such as allergy, did not receive intrathecal morphine. This group was then
matched with patients who did receive intrathecal morphine. There was no
significant difference in mean postoperative temperature for the morphine group
(mean postanesthesia care unit arrival temperature,
35.91°C) and the no morphine group (mean postanesthesia
care unit arrival temperature, 35.88°C). However, paradoxical sweating was
noted in only 3 patients in the morphine group and 1 in the no morphine group.
This study did show that there was a decline in core temperature in both groups
preoperatively to postoperatively that was statistically and clinically
significant. However, overall the fall in temperature was considerably less
than that described in the published cases of “unintentional hypothermia with
paradoxical sweating”.
Quite frankly, given
the difficulties maintaining normothermia in this patient population and given that
the timeframe and duration of hypothermia would be compatible with the
theoretical “resetting of the hypothalamic thermostat”, we are surprised
that no one seems to have tried either lorazepam or naloxone in those cases
even though they lacked paradoxical sweating.
Undoubtedly, there
would be concern about exposing a neonate to the effects of lorazepam or
naloxone or any other drug. However, since the hypothermia extends long after the
cesarean delivery, use of lorazepam to reverse hypothermia would be an option after
the delivery.
As we noted in our
original column, the importance of recognizing the “hypothermia with paradoxical
sweating” 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. 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.
Some of our previous
columns on maternal and ob/gyn
issues:
February 5, 2008 “Reducing
Errors in Obstetrical Care”
February 2010 “Joint
Commission Sentinel Event Alert on Maternal Deaths”
April 2010 “RCA:
Epidural Solution Infused Intravenously”
July 20, 2010 “More
on the Weekend Effect/After-Hours Effect”
August 2010 “Surgical
Case Listing Accuracy”
September 7, 2010 “Patient
Safety in Ob/Gyn Settings”
January 2011 “Surgical
Fires Not Just in High Risk Cases”
February 8, 2011 “Inducing Too Early”
April 2011 “Ob/Gyn Patient Safety Programs”
April 24, 2012 “Fire
Hazard of Skin Preps Oxygen”
July 2012 “WHO
Safe Childbirth Checklist”
December 4, 2012 “Unintentional
Perioperative Hypothermia: A New Twist”
September 2013 “Full-Time
Laborists Reduce C-Section Rates”
October 2013 “Challenging
the 39-Week Campaign”
November 2013 “The
Weekend Effect: Not One Simple Answer”
January 2014 “It
MEOWS But Doesn’t Purr”
May 13, 2014 “Perioperative
Sleep Apnea: Human and Financial Impact”
August 19, 2014 “Some
More Lessons Learned on Retained Surgical Items”
November 3, 2015 “Medication
Errors in the OR - Part 2”
February 7, 2017 “Maternal
Safety Bundles”
References:
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Anesthesia Using an Ingestible Telemetric Sensor. Anesthesia & Analgesia
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Munday J, Osborne S, Yates P, et
al. Preoperative Warming Versus no Preoperative Warming for Maintenance of
Normothermia in Women Receiving Intrathecal Morphine for Cesarean Delivery: A
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126(1): 183-189, January 2018
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Induced by Spinal Anesthesia for Cesarean Delivery Might Be More Significant
Than We Think: Are We Doing Enough to Warm Our Parturients?
Anesthesia & Analgesia 2018; 126(1): 7-9
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Munday J, Osborne S, Yates
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Cesarean delivery: A Retrospective Case-Control Study
Journal of PeriAnesthesia Nursing 2017; article
in press
http://www.jopan.org/article/S1089-9472(16)30251-9/abstract
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