Cover of Prevention and management of hypothermia and shivering

Prevention and management of hypothermia and shivering

Caesarean birth

Evidence review C

NICE Guideline, No. 192

Authors

.

London: National Institute for Health and Care Excellence (NICE); .
ISBN-13: 978-1-4731-4052-3
Copyright © NICE 2021.

Hypothermia and shivering

Review question

What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

Introduction

Hypothermia and shivering may be seen in people undergoing surgery and may be due to physical causes, such as exposure of skin in a cool operating theatre, the effects of certain anaesthetic agents, and to the release of stress hormones such as adrenaline. Shivering increases oxygen consumption and therefore may increase the risk of cardiac complications, while hypothermia may adversely affect blood clotting and wound healing. In addition, shivering also has practical consequences, as it makes it difficult to monitor blood pressure using non-invasive methods such as oscillometric blood pressure monitors.

Complications due to hypothermia are more of a problem for the elderly, and people with pre-existing cardiac disease, while the majority of the population of women having a caesarean birth are young and healthy. There is little evidence of adverse morbidity for mothers and babies due to hypothermia and shivering, but it is known to be unpleasant and may reduce the quality of the birth experience.

The aim of this review is to identify what procedures can be used to prevent and manage hypothermia and shivering in women having a caesarean birth.

Summary of the protocol

Please see Table 1 for a summary of the Population, Intervention, Comparison and Outcome (PICO) characteristics of this review.

Table 1. Summary of the protocol (PICO table).

Table 1

Summary of the protocol (PICO table).

For further details, see the review protocol in appendix A.

Methods and process

This evidence review was developed using the methods and process described in Developing NICE guidelines: the manual (2014). Methods specific to this review question are described in the review protocol in appendix A.

Declarations of interest were recorded according to NICE’s 2014 conflicts of interest policy until 31 March 2018. From 1 April 2018, declarations of interest were recorded according to NICE’s 2018 conflicts of interest policy. Those interests declared until April 2018 were reclassified according to NICE’s 2018 conflicts of interest policy (see Register of Interests).

Clinical evidence
Included studies

Twenty-three studies were included in this review. Twenty-one studies were patient level RCTs, and 2 were cluster RCTs (Duryea 2016, Grant 2015). Cluster RCTs were downgraded once for imprecision as they provided insufficient information available for design effect adjustment. One study examined management of shivering (only intervening with women who were shivering, Casey 1988), and 22 studies assessed prevention of shivering, with measures administered before or during caesarean birth (CB), whether women were shivering or not.

Data were grouped by the comparison of interest, and the intervention type:

Image

Table

FAW: forced air warming; IV: intravenous

Studies were performed in women with a scheduled/elective/non-emergency caesarean birth, or included any caesarean birth:

See the literature search strategy in appendix B and study selection flow chart in appendix C.

Excluded studies

Studies not included in this review with reasons for their exclusions are provided in appendix K.

Summary of clinical studies included in the evidence review

A summary of the studies that were included in this review are presented in Table 2.

Table 2. Summary of included studies.

Table 2

Summary of included studies.

See the full evidence tables in appendix D and the forest plots in appendix E.

Quality assessment of clinical outcomes included in the evidence review

See the clinical evidence profiles (GRADE tables) in appendix F.

Economic evidence
Included studies

A systematic review of the economic literature was conducted but no economic studies were identified which were applicable to this review question.

See the literature search strategy in appendix B.

Economic model

No economic modelling was undertaken for this review because the committee agreed that other topics were higher priorities for economic evaluation.

Evidence statements

When subgroups have been assessed, these statements are presented as bullet points below the main comparison

Active warming measures versus control
Comparison 1. Warmed IV fluids versus control
Critical outcomes
Incidence of hypothermia
  • Very low quality evidence from 2 RCTs (n=216) shows no clinically important difference in the incidence of hypothermia between the group who received warmed IV fluids and the control group.
Incidence of shivering
  • Low quality evidence from 6 RCTs (n=369) shows a clinically important difference between groups, with a lower incidence of shivering in the group who received warmed IV fluids compared to the control group.
    Subgroup analysis:
    • Very low quality evidence from 3 RCTs (n=255) shows no clinically important difference in the incidence of shivering between the group who received warmed IV fluids (maintained fluid warming 37–42°C) and the control group.
    • Very low quality evidence from 1 RCT (n=30) shows a clinically important difference in the incidence of shivering between the groups, with a lower incidence of shivering in the group who received warmed IV fluids (pre-warmed fluids at 37–42°C) compared to the control group.
    • Low quality evidence from 1 RCT (n=44) shows a clinically important difference in the incidence of shivering between the groups, with a lower incidence of shivering in the group who received warmed IV fluids (pre-warmed fluids at 30–34°C) compared to the control group.
    • Very low quality evidence from 1 RCT (n=40) shows no clinically important difference in the incidence of shivering between groups who received warmed IV fluids (maintained fluid warming at 36.5°C) compared to control group.
Estimated blood loss
  • Low quality evidence from 4 RCTs (n=249) shows no clinically important difference in the volume of blood loss between the group who received warmed IV fluids compared to the control group.
    Subgroup analysis:
    • Low quality evidence from 1 RCT (n=149) shows no clinically important difference in estimated blood loss between the group who received warmed IV fluids (maintained fluid warming 37–42°C) compared to the control group.
    • Moderate quality evidence from 1 RCT (n=60) shows no clinically important difference in estimated blood loss between the group who received warmed IV fluids (pre-warmed fluids at 37–42°C) compared to the control group
    • Very low quality evidence from 1 RCT (n=40) shows no clinically important difference in estimated blood loss between the group who received warmed IV fluids (maintained fluid warming at 36.5°C) compared to control group
  • Very low quality evidence from 1 RCT (n=67) shows no clinically important difference in the need for blood products between the group who received warmed IV fluids compared to the control group.
Important outcomes
Maternal (core) temperature change
  • Low quality evidence from 2 RCTs (n=70) shows a clinically important difference in maternal temperature with less of a fall (change) in core temperature in the group who received warmed IV fluids compared to the control group.
Maternal temperature at different time points
  • Intra-operative: Very low quality evidence from 3 RCTs (n=246) shows a clinically important difference in intra-operative maternal temperature between groups, with a higher core temperature in the group who received warmed IV fluids compared to the control group.
  • Post-op, baseline, and 30 minutes later: Very low and low quality evidence from 2 RCTs (n=97) shows a clinically important difference in maternal temperature at these time points with a higher core temperature in the group who received warmed IV fluids compared to the control group.
  • Post-op, 45 minutes or later: Very low quality evidence from 3 RCTs (n=246) shows a clinically important difference in maternal temperature at these time points with a higher core temperature in the group who received warmed IV fluids compared to the control group.
  • Post-op, discharge/postpartum: Very low quality evidence from 2 RCTs (n=216) shows a clinically important difference in maternal temperature at these time points with a higher core temperature in the group who received warmed IV fluids compared to the control group.
Thermal comfort
  • Very low quality evidence from 1 RCT (n=30) shows no clinically important difference in thermal comfort between the group who received warmed IV fluids compared to the control group.
  • High quality evidence from 1 RCT (n=75) shows a clinically important difference in thermal comfort with a lower incidence of scoring low (<4) on thermal comfort in the group who received warmed IV fluids compared to the control group.
  • Low quality evidence from 1 RCT (n=75) shows no clinically important difference in thermal comfort (incidence of scoring high (>6) on thermal comfort) between the group who received warmed IV fluids compared to the control group.
Wound infection
  • No evidence was available for this outcome.
Comparison 2. Forced air warming versus control
Critical outcomes
Incidence of hypothermia
  • Very low quality evidence from 3 RCTs (n=157) shows no clinically important difference in the incidence of hypothermia between the group who received forced air warming compared to the control group, overall or for either subgroup (background of no additional warming or background of maintained warmed IV fluids).
Incidence of shivering
  • Low quality evidence from 6 RCTs (n=242) shows a clinically important difference in the incidence of shivering, with a lower incidence in the forced air warming group compared to the control group.
Estimated blood loss
  • Low quality evidence from 3 RCTs (N=147) shows no clinically important difference in estimated blood loss between the group who received forced air warming compared to the control group, overall or for either subgroup (background of no additional warming or background of maintained warmed IV fluids).
Important outcomes
Maternal temperature change
  • Peri-operative change: Very low quality evidence from 1 RCT (n=30) shows no clinically important difference in rate of change of temperature between the group who received forced air warming compared to the control group.
  • Intra-operative change: Very low quality evidence from 3 RCTs (n=142) shows no clinically important difference in rate of change of temperature between the group who received forced air warming compared to the control group.
Maternal temperature at different time points
  • Intra-operative, within 30 minutes: Very low quality evidence from 2 RCTs (n=127) shows no clinically important difference in maternal temperature at this time point between the group who received forced air warming compared to the control group.
  • Intra-operative, immediately post-delivery: Very low quality evidence from 1 RCT (n=40) shows no clinically important difference in maternal temperature at this time point between the group who received forced air warming compared to the control group.
  • Intra-operative, end of surgery: Very low quality evidence from 4 RCTs (n=219) shows a clinically important difference in maternal temperature at this time point between the groups, with a higher core temperature in the group who received forced air warming group compared to the control group.
  • Post-op, recovery room, within 15 minutes: Very low quality evidence from 1 RCT (n=87) shows a clinically important difference in maternal temperature at this time point between the groups, with a higher core temperature in the group who received forced air warming group compared to the control group.
Thermal comfort
  • Pre-operative: Very low quality evidence from 2 RCTs (n=70) shows a clinically important difference in thermal comfort between groups, with a higher level of thermal comfort in the group who received forced air warming compared to the control group.
  • Intra-operative, immediately post-delivery: Very low quality evidence from 1 RCT (n=40) shows a clinically important difference in thermal comfort between groups, with a higher level of thermal comfort in the group who received forced air warming compared to the control group.
  • Intra-operative, end of surgery: Low quality evidence from 1 RCT (n=40) shows a clinically important difference in thermal comfort between groups, with a higher level of thermal comfort in the group who received forced air warming compared to the control group.
  • Post-operative: Low quality evidence from 3 RCTs (N=110) shows no clinically important difference in thermal comfort between the group who received forced air warming compared to the control group, overall or for either subgroup (post-op discharge or peri-operative)
Wound infection
  • Very low quality evidence from 1 RCT (n=87) shows no clinically important difference in wound infection between the group who received forced air warming compared to the control group.
Comparison 3. Forced air warming + warmed IV fluid versus control
Critical outcomes
Incidence of hypothermia
  • Moderate quality evidence from 1 RCT (n=44) shows a clinically important difference in incidence of hypothermia between the groups, with a lower incidence of hypothermia in the in the group who received forced air warming and warmed IV fluid compared to the control group.
Incidence of shivering
  • Intra-operative: Moderate quality evidence from 1 RCT (n=44) shows no clinically important difference in shivering between group who received forced air warming and warmed IV fluid compared to the control group.
  • Post-operative: Low quality evidence from 1 RCT (n=44) shows no clinically important difference in shivering between group who received forced air warming and warmed IV fluid compared to the control group.
Estimated blood loss
  • Low quality evidence from 1 RCT (n=44) shows no clinically important difference in estimated blood loss between group who received forced air warming and warmed IV fluid compared to the control group, based on the wide inter-quartile range (IQR) in both groups.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • Intra-operative/recovery room, baseline: Moderate quality evidence from 1 RCT (n=44) shows a clinically important difference in maternal temperature at these time points between groups, with a higher core temperature in the group who received forced air warming and warmed IV fluid compared to the control group.
Thermal comfort
  • Post-op/recovery room, discharge: Low quality evidence from 1 RCT (n=44) shows no clinically important difference in thermal comfort between group who received forced air warming and warmed IV fluid compared to the control group, based on the wide IQR in both groups
Wound infection
  • No evidence was available for this outcome.
Comparison 4. Warmed mattress/under-body pad versus control
Critical outcomes
Incidence of hypothermia
  • Very low quality evidence from 3 RCTs (n=357) shows no clinically important difference in the incidence of hypothermia between the group who received a warmed mattress/under-body pad compared to the control group.
    Subgroup analysis:
    • Undefined time point: Low quality evidence from 2 RCTs (n=204) shows a clinically important difference in the incidence of hypothermia between groups, with a lower incidence of hypothermia in the group who received a warmed mattress/under-body pad compared to the control group.
    • Postpartum: Very low quality evidence from 1 RCT (n=153) shows no clinically important difference in the incidence of hypothermia between the group who received a warmed mattress/under-body pad compared to the control group.
Incidence of shivering
  • Very low quality evidence from 1 RCT (n=116) shows no clinically important difference in the incidence of shivering between the group who received a warmed mattress/under-body pad compared to the control group.
Estimated blood loss
  • Low quality evidence from 1 RCT (n=241) shows no clinically important difference in estimated blood loss between the group who received a warmed mattress/under-body pad compared to the control group.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome
Maternal temperature at different time points
  • Intra-operative: Very low quality evidence from 3 RCTs (n=357) shows a clinically important difference in maternal temperature between groups, with a higher core temperature in the group who received a warmed mattress/under-body pad compared to the control group.
    Subgroup analysis:
    • First 30 minutes: Moderate quality evidence from 2 RCTs (n=204) shows no clinically important difference in maternal temperature between the group who received a warmed mattress/under-body pad compared to the control group.
    • Anytime in operating room: Very low quality evidence from 1 RCT (n=153) shows a clinically important difference in maternal temperature between the groups, with a higher core temperature in the group who received a warmed mattress/under-body pad compared to the control group.
  • Intra-op, recovery room, baseline: very low quality evidence from 2 RCTs (n=204) shows no clinically important difference in maternal temperature between the group who received a warmed mattress/under-body pad compared to the control group.
  • Post-op, recovery room: Very low quality evidence from 2 RCTs (n=241) shows no clinically important difference in maternal temperature between the group who received a warmed mattress/under-body pad compared to the control group.
  • Post-op, postpartum: Low quality evidence from 1 RCT (n=153) shows a clinically important difference in maternal temperature between the groups, with a higher core temperature in the group who received a warmed mattress/under-body pad compared to the control group.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • Very low quality evidence from 1 RCT (n=88) shows no clinically important difference in wound infections between the group who received a warmed mattress/under-body pad compared to the control group.
Active warming measures versus other active warming
Comparison 5. Forced air warming versus warmed IV fluids
Critical outcomes
Incidence of hypothermia
  • No evidence was available for this outcome.
Incidence of shivering
  • Very low quality evidence from 1 RCT (n=30) shows no clinically important difference in the incidence of shivering between the group who received forced air warming compared to the group who received warmed IV fluids.
Estimated blood loss
  • Very low quality evidence from 1 RCT (n=30) shows no clinically important difference in estimated blood loss between the group who received forced air warming compared to the group who received warmed IV fluids.
Important outcomes
Maternal temperature change
  • Intra-operative, 45 minutes post-intervention: Very low quality evidence from 1 RCT (n=30) shows no clinically important difference in rate of change of temperature between the group who received forced air warming compared to the group who received warmed IV fluids.
Maternal temperature at different time points
  • No evidence was available for this outcome.
Thermal comfort
  • Very low quality evidence from 1 RCT (n=30) shows no clinically important difference in thermal comfort between the group who received forced air warming compared to the group who received warmed IV fluids.
Wound infection
  • No evidence was available for this outcome.
Comparison 6. Forced air warming versus mattress warming
Critical outcomes
Incidence of hypothermia
  • Very low quality evidence from 1 RCT (n=87) shows no clinically important difference in the incidence of hypothermia between the group who received forced air warming compared to the group who received mattress warming.
Incidence of shivering
  • No evidence was available for this outcome.
Estimated blood loss
  • Low quality evidence from 1 RCT (n=87) shows no clinically important difference in estimated blood loss between the group who received forced air warming compared to the group who received mattress warming.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • Pre-operative, 15 minutes post-anaesthetic: Low quality evidence from 1 RCT (n=87) shows no clinically important difference in maternal temperature between the group who received forced air warming compared to the group who received mattress warming.
  • Intra-operative, recovery room, baseline: Low quality evidence from 1 RCT (n=87) shows no clinically important difference in maternal temperature between the group who received forced air warming compared to the group who received mattress warming.
  • Post-operative, recovery room, after 15 minutes: Very low quality evidence from 1 RCT (n=87) shows a clinically important difference in maternal temperature between groups, with a higher core temperature in the group who received forced air warming compared to the group who received mattress warming.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • Very low quality evidence from 1 RCT (n=87) shows no clinically important difference in wound infections between the group who received forced air warming compared to the group who received mattress warming.
Comparison 7. Warmed mattress/under body pad versus other warming (not control/ usual care)
Critical outcomes
Incidence of hypothermia
  • Very low quality evidence from 1 RCT and 1 cluster RCT (n=412) shows a clinically important difference in incidence of hypothermia between groups, with a lower incidence of hypothermia in the warmed mattress group compared to other warming group.
    Subgroup analysis:
    • Very low quality evidence from 1 cluster RCT (n=262) shows a clinically important difference in the incidence of hypothermia between the groups, with a lower incidence of hypothermia in the warmed mattress group compared to other warming group, for the subgroup where the other warming group used warmed IV fluids, tinfoil hats, and warmed blankets.
    • Very low quality evidence from 1 RCT (n=150) shows no clinically important difference in the incidence of hypothermia between the groups, for the subgroup where the other warming group used warmed IV fluids only.
Incidence of shivering
  • No evidence was available for this outcome.
Estimated blood loss
  • Very low quality evidence from 1 RCT (n=150) shows no clinically important difference in estimated blood loss between the warmed mattress group compared to other warming group.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • Intra-operative: Very low quality evidence from 1 RCT and 1 cluster RCT (n=412) shows no clinically important difference in maternal temperature between the warmed mattress group compared to other warming group.
    Subgroup analysis:
    • Very low quality evidence from 1 cluster RCT (n=262) shows a clinically important difference in maternal temperature between the groups, with a higher core temperature in the warmed mattress group compared to other warming, for the subgroup where the other warming group used warmed IV fluids, tinfoil hats, and warmed blankets.
    • Low quality evidence from 1 RCT (n=150) shows no clinically important difference in maternal temperature between the warmed mattress group compared to other warming group, for the subgroup where the other warming group used warmed IV fluids only.
  • Post-operative, recovery room: very low quality evidence from 1 RCT and 1 cluster RCT (n=634) shows no clinically important difference in maternal temperature between the warmed mattress group compared to other warming group, overall or in either subgroup.
  • Post-operative, postpartum: Low quality evidence from 1 RCT (n=150) shows no clinically important difference in maternal temperature between the warmed mattress group compared to other warming group.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • Very low quality evidence from 1 cluster RCT (n=484) shows no clinically important difference in wound infection between the warmed mattress group compared to other warming group.
Thermal insulation measures
Comparison 8. Higher versus lower ambient temperature
Critical outcomes
Incidence of hypothermia
  • Very low quality evidence from 1 cluster RCT (n=791) shows no clinically important difference in the incidence of hypothermia between the higher ambient temperature group compared to the lower ambient temperature group.
Incidence of shivering
  • No evidence was available for this outcome.
Estimated blood loss
  • No evidence was available for this outcome.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • No evidence was available for this outcome.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • Very low quality evidence from 1 cluster RCT (n=791) shows no clinically important difference in wound infection between the higher ambient temperature group compared to the lower ambient temperature group.
Pharmacological therapy
Comparison 9. 5-HT3 antagonist versus control
Critical outcomes
Incidence of hypothermia
  • No evidence was available for this outcome.
Incidence of shivering
  • Very low quality evidence from 1 RCT (n=116) shows no clinically important difference in the incidence of shivering between the group receiving a 5-HT3 antagonist and the control group.
  • Very low quality evidence from 1 RCT (n=116) shows no clinically important difference in the incidence of shivering reaching a maximum value of 2–4 between the group receiving a 5-HT3 antagonist and the control group.
Estimated blood loss
  • No evidence was available for this outcome.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • No evidence was available for this outcome.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • No evidence was available for this outcome.
Comparison 10. Opioid-like analgesic (pethidine) versus other opioid (morphine)
Critical outcomes
Incidence of hypothermia
  • No evidence was available for this outcome.
Incidence of shivering
  • Very low quality evidence from 1 RCT (n=119) shows a clinically important difference in the incidence of shivering between the groups, with a lower incidence of shivering in the pethidine group compared to the morphine group.
    Subgroup analysis:
    • Very low quality evidence from 1 RCT (n=59) shows no clinically important difference in the incidence of shivering between pethidine group compared to the morphine group, for the subgroup who received 10mg pethidine compared to 0.1mg morphine
    • Very low quality evidence from 1 RCT (n=60) shows no clinically important in the incidence of shivering between pethidine group compared to the morphine group, for the subgroup who received 10mg pethidine compared to 0.2mg morphine
Estimated blood loss
  • No evidence was available for this outcome.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • No evidence was available for this outcome.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • No evidence was available for this outcome.
Comparison 11a. Opioid-like analgesic versus control for prevention
Critical outcomes
Incidence of hypothermia
  • No evidence was available for this outcome.
Incidence of shivering
  • Low quality evidence from 3 RCTs (n=313) shows a clinically important difference in the incidence of shivering between groups, with a lower incidence of shivering in the opioid-like analgesic group compared to the control group.
    Subgroup analysis:
    • Low quality evidence from 1 RCT (n=94) shows a clinically important difference in the incidence of shivering between groups, with a lower incidence of shivering in the opioid-like analgesic group compared to the control group, for the sub-group receiving 25mg pethidine.
    • Very low quality evidence from 1 RCT (n=60) shows no clinically important difference in the incidence of shivering in the opioid-like analgesic group compared to the control group, for the sub-group receiving 10mg pethidine.
    • Low quality evidence from 1 RCT (n=40) shows a clinically important difference in the incidence of shivering between groups, with a lower incidence of shivering in the opioid-like analgesic group compared to the control group, for the sub-group receiving 0.2mg/kg meperidine.
    • Very low quality evidence from 1 RCT (n=59) shows no clinically important difference in the incidence of shivering in the opioid-like analgesic group compared to the control group, for the sub-group receiving 0.1mg morphine.
    • Very low quality evidence from 1 RCT (N=60 shows no clinically important difference in the incidence of shivering in the opioid-like analgesic group compared to the control group, for the sub-group receiving 0.2mg morphine.
Estimated blood loss
  • No evidence was available for this outcome.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • No evidence was available for this outcome.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • No evidence was available for this outcome.
Comparison 11b. Opioid-like analgesic (meperidine) versus control for management
Critical outcomes
Incidence of hypothermia
  • No evidence was available for this outcome.
Incidence of shivering
  • At 2, 5, 15, 30, and 60 minutes post infusion: Low quality evidence from 1 RCT (n=40) shows a clinically important difference in the incidence of shivering at these time points between groups, with a lower incidence of shivering in the meperidine group compared to the control group.
Estimated blood loss
  • No evidence was available for this outcome.
Important outcomes
Rate of change of temperature (maternal temperature change)
  • No evidence was available for this outcome.
Maternal temperature at different time points
  • At 2 and 5 minutes post infusion: Very low quality evidence from 1 RCT (n=40) shows no clinically important difference in maternal temperature at these time points between the meperidine group and the control group.
  • At 15, 30, and 60 minutes post infusion: Low quality evidence from 1 RCT (n=40) shows a clinically important difference in maternal temperature at these time points between groups, with a higher core temperature in the control group compared to meperidine group.
Thermal comfort
  • No evidence was available for this outcome.
Wound infection
  • No evidence was available for this outcome.
Economic evidence statements

No economic evidence was identified which was applicable to this review question.

The committee’s discussion of the evidence
Interpreting the evidence
The outcomes that matter most

The incidence of hypothermia and shivering were considered to be the critical outcomes for this review as these were the symptoms of interest. Hypothermia may adversely affect clotting and so estimated blood loss was also considered to be critical outcome.

Hypothermia may also impair wound healing and so wound infection was an important outcome. Maternal temperature and rate of change of temperature were considered important as they would indicate if the prevention or management of hypothermia had been successful. Finally, as hypothermia and shivering are reported by women as impairing their experience of childbirth, thermal comfort was selected as an important outcome.

The quality of the evidence

The quality of evidence for this review was assessed using GRADE.

For active warming measures, the evidence was very low to moderate quality with only one outcome (from a small single study) in one comparison deemed high quality (thermal comfort score<4, n=75, comparison 1). The evidence for thermal insulation measures and pharmacological therapy was assessed as very low to low quality for all outcomes of interest.

Quality was largely downgraded for imprecision (wide confidence intervals), and unclear or high risk of bias across multiple domains (blinding of participants/personnel, and outcomes).

Benefits and harms

The committee discussed the potential causes of shivering and hypothermia during a caesarean birth, which may in part be due to the effects of the epidural or spinal anaesthesia. As the majority (up to 99% of elective and 97% of emergency caesarean births) are performed under regional anaesthesia, some complications such as shivering and thermal discomfort are evident in both the intra-operative and post-operative period. The committee noted that the incidence of hypothermia and shivering had decreased since the introduction of drapes which collected the amniotic fluid and so reduced the quantity of wet drapes that were in contact with the woman’s skin.

The committee noted that there were already existing NICE guidelines on Hypothermia: prevention and management in adults having surgery (NICE CG65, 2008), and that this guideline provides guidance on the importance of avoiding peri-operative hypothermia to reduce the risk of postoperative complications, such as increased perioperative blood loss, longer post-anaesthetic recovery, postoperative shivering, thermal discomfort, morbid cardiac events including arrhythmia, altered drug metabolism, increased risk of wound infection, reduced patient satisfaction with the surgical experience, and longer stay in hospital. The committee discussed the differences between caesarean birth and general surgery populations, and noted that the risk of some of these adverse effects was reduced in women undergoing caesarean birth as they were usually younger, fitter and healthier than the general surgical population. In particular, the committee noted that the incidence of wound infection was low after caesarean birth, and so it may be difficult to see a difference in wound infection rates due to interventions for shivering and hypothermia.

The committee then discussed the evidence regarding the efficacy of different approaches to prevent hypothermia and reduce the risk of complications in women having a caesarean birth.

The evidence showed that none of the interventions reduced estimated blood loss. However, the committee agreed that if major obstetric haemorrhage occurs, maternal hypothermia can be a factor in impairing the function of coagulation proteins. It is therefore useful to maintain core temperature in women undergoing caesarean birth (particularly those at increased risk of post-partum haemorrhage) to minimise the risk of coagulopathy.

Similarly, none of the warming methods reduced the incidence of wound infection. However, the committee noted that the incidence of wound infection in the studies was very low (1/791 in Duryea 2016 and 5/484 in Grant 2015) so the trials were unlikely to have been powered to detect a difference.

The committee noted that each method of active warming showed benefit compared to usual care (control) in the incidence of shivering and hypothermia, or in maternal temperature or thermal comfort. The comparisons of different active warming measures with each other showed that there were few significant differences between groups. Active warming measures showed benefit with regards to thermal comfort when they were applied intra-operatively, with fewer differences postoperatively when the active warming had been removed.

The committee noted that current NICE guideline for general surgical procedures recommend forced air warming measures when the procedure is longer than 30 minutes. The committee agreed that all caesarean births fulfil this criterion, and discussed that if they made recommendations consistent with general surgical guidelines, this would mean that all women undergoing caesarean birth would receive forced air warming. However, the committee again noted the physiological differences between women having a caesarean birth and the general surgical population – pregnant women retain heat more effectively, likely due to their comparatively young age and better health (for example, fewer comorbidities). Thus using additional warming before the woman experiences a drop in core temperature or initiation of shivering may not be necessary, and even though the majority of the evidence was for the prevention of hypothermia and shivering, not for management, the committee agreed that they would expect forced air warming methods to work well for management and so recommended its use for women who develop shivering or hypothermia. The committee agreed that a temperature of less than 36°C was an appropriate threshold used to define a patient who was hypothermic and at which there was an increased risk of adverse effects due to a reduced body temperature. This was also the threshold used in the NICE guideline for general surgical procedures and so the committee set this as the temperature threshold at which forced air warming should be commenced.

The use of warmed IV fluids alone or when in combination with another active warming measure (for example, forced air warming), was beneficial when compared to standard care/unwarmed fluids. Again, the committee noted that the current NICE guideline for general surgical procedures recommends warmed intravenous fluids and blood products if the volume is greater than 500 ml. The committee discussed the fact that women may receive small volume infusions (for example, antibiotics or analgesics) and these would not need warming, but agreed that all larger volumes could have a cooling effect if administered unwarmed. The committee noted that the studies included in the review used a variety of different methods to warm IV fluids – some used a warming cabinet, some used an in-line warmer, and 1 study used a combination of both. The committee therefore chose to not specify exactly which method should be used to warm IV fluids, and noted that this was the same as the recommendation in the NICE guideline for general surgical procedures which does not state the method to be used. The committee also noted that the studies warmed fluids to a variety of temperatures, but agreed that fluids should normally be warmed and administered at body temperature of 37°C. The committee discussed that there was no evidence from this review for the warming of irrigation fluids where used, but that this is considered best practice in all surgery, and is recommended in the NICE guideline for general surgical procedures. The committee therefore agreed to adopt the recommendation from this guideline for the prevention of shivering and hypothermia in women having a caesarean birth. The temperature range of 38°C to 40°C was also adopted from this guideline and the committee agreed that this was in accordance with their clinical experience, as irrigation fluids were warmed in a cabinet, and then removed for administration, so would cool down to 37°C by the time they were administered.

The committee discussed the availability of the various active warming measures assessed in the review and agreed that mattress warming/under-body pads were not widely used or available, would have to remain in the surgical suite, and had issues around cleaning and reusability. Forced air warming used disposable ‘blankets’ into which hot air could be blown, and could be utilised at multiple stages of the procedure, travelling with the woman into recovery and onto the ward if appropriate. The committee therefore recommended forced air warming and noted that this was in line with the recommendations in the current NICE guideline for general surgical procedures.

The evidence showed there was no benefit from the higher ambient temperature compared to the lower ambient temperature (thermal insulation) in the prevention of shivering and hypothermia, However, the committee agreed that the small (3°C) difference between 20°C and 23°C room temperature in the study was insufficient to make a difference to outcomes, and they routinely maintain temperatures above this during most surgical procedures already, and so did not make a recommendation.

The evidence for pharmacological interventions showed a benefit of opioids (pethidine/meperidine) to prevent and manage shivering, and this was the only comparison that looked specifically at the management of hypothermia and shivering as opposed to primary prevention. Intravenous pethidine (50 mg, immediately post-delivery) was used in women having a caesarean birth under epidural anaesthesia with lidocaine and adrenaline. This significantly reduced the incidence and severity of shivering without increasing the incidence of nausea or need for anti-emetics. The incidence of shivering in the control group was high (87%), which was attributed to the cold operating theatre and rapid infusion of cold solutions. The committee noted that there was a higher incidence of shivering but a lower incidence of hypothermia in the control group of women who were already shivering, but discussed that this may be due to the fact that the act of shivering raises core temperature, and so administering of the opioid reduced shivering but then led to a lower body temperature compared to the control group.

The committee considered the use of opioids as a second line treatment (following the implementation of active warming measures if this was ineffective). However, after further discussion they agreed that despite the evidence for opioids (pethidine) in both prevention and management of shivering and hypothermia, its use during a caesarean birth would negatively impact the woman’s ability to breastfeed in the hours after birth, and consequently they did not make a recommendation to use opioids. The committee also noted that although pethidine was the only intervention assessed for use in management once hypothermia and shivering occurs, this evidence was from one small study conducted in the 1980s.

The evidence for the 5-HT3 antagonist (ondansetron) showed no benefit in preventing shivering and the committee considered whether to make a recommendation highlighting the fact it should not be used for this purpose. However, the committee decided not to make a ‘do not use’ recommendation as ondansetron is used to prevent and treat nausea and vomiting, so having a recommendation that it should not be used could be confusing for healthcare professionals.

The committee agreed that one of the main benefits of measures to prevent and manage hypothermia and shivering, such as use of forced air warming, was that it made the woman more comfortable and improved their birth experience, and that this was important to take into account.

Cost effectiveness and resource use

The committee discussed the cost implications of hypothermia and shivering, and noted that current practice is to retain the woman in the recovery ward if she is still shivering or has a core temperature below 36°C (hypothermia), so effective prevention and management of hypothermia and shivering may allow women to return to the postnatal ward earlier which would reduce resource use.

The committee noted that the cost-benefit analysis in the NICE guideline for the general surgical population had found that the expenditure on devices that were proven to prevent hypothermia was cost effective due to the reduction in wound infections. However, as noted above the rate of wound infection after caesarean birth is low, and no reduction in wound infection had been seen in this population.

The committee discussed the cost of the forced air warming blankets which were approximately £15 to £25 each, and recognised that even if the blankets were only used in women who were shivering or hypothermic, and not as prevention, there may be some cost implications to the NHS, depending on local current practice. However, they also noted that the number of women who would require warming would be a relatively low proportion of those having a caesarean birth as the room temperature is kept warm and warmed IV and irrigations fluids are used.

The committee agreed that warming of IV fluids and blood during infusion and warming irrigation fluids in a warming cabinet prior to administration is already standard practice.

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Appendices

Appendix A. Review protocols

Review protocol for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

Table 3. Review protocol for hypothermia and shivering

Appendix B. Literature search strategies

Literature search strategies for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

Review question search strategies
Databases: Medline; Medline EPub Ahead of Print; and Medline In-Process & Other Non-Indexed Citations

Date last searched: 22/11/2019

Databases: Embase; and Embase Classic

Date last searched: 22/11/2019

Databases: Cochrane Central Register of Controlled Trials; and Cochrane Database of Systematic Reviews

Date last searched: 22/11/2019

Health economics search strategies
Databases: Medline; Medline EPub Ahead of Print; and Medline In-Process & Other Non-Indexed Citations

Date last searched: 22/11/2019

Databases: Embase; and Embase Classic

Date last searched: 22/11/2019

Database: Cochrane Central Register of Controlled Trials

Date last searched: 22/11/2019

Appendix C. Clinical evidence study selection

Clinical study selection for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

Figure 1. Study selection flow chart

Appendix D. Clinical evidence tables

Clinical evidence tables for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

Table 4. Clinical evidence tables for hypothermia and shivering (PDF, 995K)

Appendix E. Forest plots

Forest plots for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

This section includes forest plots only for outcomes that are meta-analysed. Outcomes from single studies are not presented here, but the quality assessment for these outcomes is provided in the GRADE profiles in appendix F.

Active warming measures versus control

Active warming measures versus other active warming

Comparison 7. Warmed mattress/under-body pad vs other warming

Pharmacological therapy

Comparison 10. Opioid-like analgesic (pethidine) vs other opioid (morphine)

Comparison 11a. Opioid-like analgesic vs control for prevention

Appendix G. Economic evidence study selection

Economic evidence study selection for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

No evidence was identified which was applicable to this review question.

Figure 2. Study selection flow chart

Appendix H. Economic evidence tables

Economic evidence tables for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

No evidence was identified which was applicable to this review question.

Appendix I. Economic evidence profiles

Economic evidence profiles for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

No evidence was identified which was applicable to this review question

Appendix J. Economic analysis

Economic evidence analysis for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

No economic analysis was conducted for this review question.

Appendix K. Excluded studies

Excluded studies for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

Economic studies

No economic evidence was identified for this review.

Appendix L. Research recommendations

Research recommendations for review question: What are the procedures to prevent and manage hypothermia and shivering in women having a caesarean birth in the pre-operative, peri-operative and post-operative periods?

No research recommendations were made for this review question.