Peri-operative Active Warming Versus no Peri-operative Active Warming During Caesarean Section for Preventing Neonatal Hypothermia in Women Performing Skin-to-skin Care: A Randomized Controlled Trial

Peri-operative active warming is the practice of warming patients who undergo an operation with the use of one or more warming devices. Active warming can be initiated before, during and/or after an operation and its main purpose is to prevent and/or manage hypothermia in patients. Commonly used warming devices include: forced-air warming, fluid warmers, heating gel pads, water mattresses and electric blankets.

Peri-operative active warming has been researched over the past 30 years, with more sophisticated methods of active warming being introduced in recent years. Regardless of their complexity, these devices are used in order to prevent inadvertent perioperative hypothermia (IPH) and its complications in patients who undergo an operation. Complications of IPH include: thermal discomfort (including shivering), increased intra-operative blood loss, increased risk of wound infection, cardiac morbid events and increased length of stay in recovery room and in the hospital.

Although peri-operative warming is well established for general operations, there is a dearth of literature regarding active warming of pregnant women undergoing caesarean section (CS). The National Institute of Health and Care Excellence (NICE) developed guidelines for managing IPH for adults undertaking various general operations, however pregnant women and children/infants were excluded from these guidelines due to lack of evidence supporting or rejecting the use of peri-operative active warming for this population. The two active warming methods recommended by NICE include the use of forced-air warming and fluid warmers. Specifically all patients should be actively warmed with a forced-air warming device before/during their operation if their temperature is below 36°C and every patient should receive warmed IV fluids (via an IV fluid warmer) for volumes ≥500 mls of IV fluids. The patient's temperatures should be measured every 30 minutes from the time of their anaesthesia until their discharge to the ward.

An additional factor that complicates the decision of applying, or not, an active warming to pregnant women during a CS is the effect of active warming on new-borns during/after birth. This factor becomes even more relevant when skin-to-skin contact (SSC), between mothers and their new-borns, is initiated immediately after a CS. Specifically, there is a lack of research evidence on the effect, if any, of active warming on the new-born's temperature and general wellbeing. Three unpublished audits undertaken in the theatre department of a large maternity hospital in Dublin (between 2012 and 2014), have shown an increased number of hypothermic mothers and new-borns during and after CS. The hospital has a general practice of not actively warming pregnant women before/during their CS, and women at low risk for complications, usually perform SSC with their infants within minutes of birth. The more recent of these three audits (2014) showed that 86% (n=33) of women became hypothermic peri-operatively (defined as a core temperature below 36°C, while 35% (n=14) of the new-borns became mildly hypothermic after birth (defined as a core temperature below 36.5°C, after undergoing SSC, despite complying with the hospital guidelines.

SSC is a widely researched technique, in which a naked new-born (wearing only a nappy and a hat) is positioned on its mother's bare chest, covered with warm towels and a blanket. SSC has multiple advantages for both mothers and their new-borns. SSC is a usual practice within Rotunda Hospital, for babies born either vaginally or via CS. Although this technique is well established after vaginal birth, there is a great demand and attempts to establish it in mother-infant dyads after birth by a CS. A potential concern arising from this practice, however, is that new-borns, born by a CS, are more prone to losing their temperature and become hypothermic after a CS, compared with those born via normal birth. A risk factor is that if the mothers core temperature drops during the CS, leading to an even lower skin temperature, then the risk of a drop in the temperature of the new-born (via conduction) is increased by placing the naked baby for SSC on a mother whose temperature is suboptimal.