Estimation of rewarming time in transported extramural hypothermic neonates
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《美国医学杂志》
1 Departments of Pediatrics, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India
2 Departments of Biochemistry, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India
Abstract
Objectives: To evaluate the time taken for rewarming hypothermic neonates and to correlate the time taken for rewarming with severity of hypothermia (WHO classification), weight, gestational age and associated morbidity. Methods : 100 extramural neonates transported to the Referral neonatal unit of a teaching hospital, with weight more than 1000 grams and abdominal skin temperature less than 36.5 oC at admission were included in the study. Hypothermia was classified as per WHO recommendations. Clinical features including age, weight, gestational age, clinical diagnosis and vitals were recorded at the time of admission. Rewarming was done under a servo-controlled radiant warmer, in skin mode at set temperature of 37 oC. Skin and air temperatures measured by the thermistor probe were recorded at the time of admission and then at least every 15 minutes till skin temperature reached 36.5 oC. The neonates were monitored for oxygen saturation, blood glucose and capillary filling time, and stabilized promptly. Results : The mean abdominal skin temperature was 34.9 ± 1.4 oC. 72% of babies were moderately or severely hypothermic as per WHO classification. The duration of rewarming was 4.9 ± 0.8 min, 17.5 ± 9.5 min and 42±7.9 min for mild, moderate and severe hypothermia respectively (p=0.021). The difference in rate of rewarming between various grades of hypothermia was also significant. The duration of rewarming a baby did not differ significantly between the different weight and gestational age groups. When the rate of rewarming was expressed as rise in oC per Kg body weight per hour, it was higher in smaller and more premature babies. The rate of rewarming was slower in asphyxiated babies. Conclusions : The duration of rewarming depends on the severity of hypothermia. When rewarmed under radiant warmer using servo mode, the duration of rewarming a baby is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.
Keywords: Abdominal skin temperature; Hypothermic neonate; Rewarming time; Transported neonate.
Hypothermia is an important cause of death in the newborn.[1],[2],[3],[4],[5] Sick or low birth weight babies admitted to neonatal units with hypothermia are more likely to die than those admitted with normal temperatures.[4],[6] Information about the time taken for rewarming and the most effective method of rewarming cold infants is scanty[7],[8],[9] and no study has been undertaken in India. Very slow rewarming was tried earlier.[5],[10],[11],[12] Later studies rewarmed severely hypothermic neonates rapidly and found it to be more beneficial.[13],[14] Clear guidelines for duration of rewarming are not available. Devices used for rewarming have been variable in different studies.[13],[15],[16] Hypothermia is associated with marked physiological derangements like hypoxia and hypoglycemia.[17] These require prompt management in intensive care setting. However, most studies on rewarming of hypothermic neonates have not been conducted in an intensive care setting.
This prompted the authors to undertake the present study with the objective of evaluating the time taken for rewarming hypothermic neonates using skin probe and servo proportional warming under radiant warmer and, correlating the time taken for rewarming with the severity of hypothermia,[6]weight, gestational age and associated morbidity in intensive care setting.
Material and Methods
A total of 100 extramural hypothermic neonates transported to a tertiary neonatal intensive care unit constituted the study material. The study was conducted between March and December 2002 and was approved by the institutional research committee. Neonates with abdominal skin temperature less than 36.5 oC at admission were included in the study. Neonates weighing less than 1000 gm were excluded. Rewarming was done under a servo controlled radiant warmer with skin and air probe and temperature display facility. The wattage of the radiant warmer was 600 watts and the distance from the baby was 80 cms. Rewarming was done in skin mode by setting the temperature at 37 oC.[13] Skin and air temperatures measured by thermistor probes were recorded at the time of admission under the radiant warmer and then at least every 15 minutes till skin temperature reached 36.5 oC .[13] The skin probe was placed on the baby's anterior abdominal wall while the air probe was placed by the side of the baby. Rectal temperature was also documented at the time of admission in 70 neonates. This was done by inserting a thermometer into the rectum of the baby at an angle of 30 degrees backward, at a distance of 2 cm from the anal orifice in the case of a preterm baby and 3 cm in the case of a term baby. The thermometer was held for at least 3 minutes.[8] The ambient temperature in the baby care area was 28-32 oC using central air conditioning.
A baby with SPO2 of less than 90% was considered hypoxic. A baby with capillary filling time of more than 3 seconds with feeble peripheral pulses was considered to be in shock. Hypoglycemia was defined as blood glucose of less than 47mg%.[18] Babies who did not cry at birth/had a feeble cry at birth/were in hypoxic ischemic encephalopathy were defined as asphyxiated. The neonates were monitored for oxygen saturation, blood glucose and capillary filling time and stabilized promptly.
The continuous variables were analyzed using student 't' test and proportions by Chi Square test or Fischer test. Probability of 5%was considered significant.
Results
All neonates were monitored for hypoxia, shock and hypoglycemia. Hypoxia, shock and hypoglycemia were detected at admission in 47%, 15% and 35% respectively.
The mean baseline abdominal skin temperature at admission was 34.9 ± 1.4 oC in all hypothermic babies. 72% of babies were moderately or severely hypothermic as per WHO classification. 52% of neonates were delivered at home, while 48% were referred from other hospitals table1.
There was good correlation between rectal and abdominal skin temperatures with the rectal temperature being higher than the abdominal skin temperature by a mean of 0.2 oC and did not change with the severity classification of any baby.
35 babies were of gestational age less than 36 weeks table2. 54 babies weighed less than 2000 gm table3. 56% of babies were asphyxiated, 73% had sepsis, 19% had pneumonia, 17% had meconium aspiration syndrome, 6% had hyaline membrane disease and 14% had meningitis table4.
The duration of rewarming was 4.9± 0.8 min, 17.5±9.5 min and 42 ± 7.9 min for mild, moderate and severe hypothermia respectively (p=0.021). The difference in rate of rewarming (both oC/hour and oC/Kg/hour) between various grades of hypothermia was also significant. (p=0.022 and p=0.04 respectively) table5.
Rate of rewarming expressed as oC per kg body weight per hour (oC/Kg/h) was significantly faster among hypothermic babies of lower gestational age (p=0.028).
However, the difference in absolute time taken for rewarming the baby and rate of rewarming the baby (o C/h) in various gestational age groups was not statistically significant table6.
Rate of rewarming (expressed as rise in temperature per Kg body weight per hour or oC/Kg/h) was significantly faster in hypothermic babies having lower weight (p=0.023). However, the difference in time taken for rewarming and rate of rewarming the neonates expressed as oC/h in various weight groups was not statistically significant table7. The rate of rewarming (oC/Kg/h) was significantly lower in asphyxiated babies (p=0.022)table8.
95% of babies did not experience any problems during rewarming. Two babies had apnea during rewarming, which was attributed to coexisting pneumonia and meningitis. They responded to tactile stimulation. Three other babies developed shock during rewarming because of co-existing sepsis.
Discussion
According to WHO classification of hypothermia,[6] the newborn with a body temperature between 36 and 36.4 o C is under cold stress (mild hypothermia). A baby with temperature between 32 and 35.9oC has moderate hypothermia while a temperature below 32oC is considered to be severe hypothermia.
Kaplan et al[13] studied rewarming of 16 neonates using radiant warmer. The mean time taken for rewarming was 3.96 ± 2.37 hr. Rewarming is facilitated by prompt management of hypoxia and hypoperfusion in the hypothermic neonate. However, there was no mention of monitoring and management of associated morbidities and pathophysiological derangements, and the ambient temperature of the nursery was not stated. The present study has been conducted using radiant warmers with facility for digital display of set and actual temperatures at recommended room temperatures of the nursery in intensive care setting. Hence, it can serve as a guideline and benchmark for smaller community hospitals with less sophisticated radiant warmers and facilities.
In the present study, the mean duration of rewarming using radiant warmer in skin mode was 4.9 min, 17.5 min and 42 min for mild, moderate and severe hypothermia respectively. According to the concept of heat transfer in physics, rise of temperature (t) of a body gaining heat is directly proportional to heat energy provided (H) and inversely proportionate to the mass of the body (m) and its specific heat(s), a constant. It is calculated as follows: t=H/ms. The duration of rewarming a neonate did not differ significantly with varying weight and gestational age. This could be because of the fact that although the larger babies have larger mass to be rewarmed, they also have larger surface area receiving more radiant heat.
When the rate of rewarming was expressed as rise in oC per kg body weight per hour, it was higher in smaller and more premature babies. This is because they have larger surface area per Kg body weight leading to more rapid penetration of radiant heat to the body core .[13]
The rate of rewarming was slower in asphyxiated babies. Non-shivering thermogenesis is known to be impaired in infants following hypoxia or asphyxia. [19],[20]
In the present study, the body temperature was measured by abdominal skin temperature in all the neonates and by rectal temperature in 70 neonates. Good correlation was observed between rectal and abdominal skin temperature with rectal temperature being higher than the abdominal skin temperature by a mean of 0.2oC.
Tafari et al[15] have observed that the rate of rise of abdominal skin temperature and rectal temperature was 1.4oC per Kg per hour and 1.22oC per kg per hour respectively during rewarming of hypothermic neonates.
The abdominal skin temperature in a neonate has been shown to be representative of the core temperature and is reliable for the diagnosis of hypothermia.[21] As the abdominal skin does not vasconstrict, it can be used as an indicator of central temperature.[22] It is easier and safer than using the rectum[22] and has been used in earlier studies on hypothermic neonates.[13],[15],[21],[22],[23],[24]
To conclude, the duration of rewarming hypothermic neonates using radiant warmer in skin mode depends on the severity of hypothermia. It is 4.9±0.8 min, 17.5±9.5 min and 42±7.9 min for mild, moderate and severe hypothermia respectively in intensive care setting at recommended ambient room temperature with prompt management of associated morbidities. The duration of rewarming is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.
Conclusion
The duration of rewarming hypothermic neonates using radiant warmer in skin mode depends on the severity of hypothermia, and is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.
Contributors: NBM conceived and designed the study, analyzed the data, finalized the draft and shall be the guarantor of the paper. SK was involved in protocol preparations, collection of data and drafting the manuscript. TKM participated in protocol preparations, analysis of data and finalizing the manuscript.
Funding: None
Competing interests: None stated.
References
1. Karan S, Rao MN, Urmila S, Rajaji S. The incidence, clinical profile, morbidity and mortality of hypothermia in the newborn. Indian Pediatr 1975; 12: 1205-1210.
2. Day RL, Caliquiri L, Kamenski C, Ehlrich F. Body temperature and survival of premature infant. Pediatrics 1964; 34: 171-181.
3. Silverman WA, Fertig JW, Berger AP. The influence of thermal environment upon survival of newly born premature infants. Pediatrics 1958; 22: 876-886.
4. Daga AS, Daga SR, Patole SK. Determinants of death among admissions to intensive care units for newborns. J Trop Pediatr 1991; 37: 53-55.
5. Arneil GC, Kerr MM. Severe hypothermia in Glasgow infants in winter. Lancet 1963; 2 : 756-759.
6. Thermal Protection of the Newborn: A Practical Guide. WHO/RHT/MSM/97.2.1997; 17-22.
7. Chandra S, Baumgart S. Temperature regulation of the premature infant. In: Avery's diseases of the newborn. Taeusch HW, Ballard RA, Gleason CA. Philadelphia , Saunders, 8th Edition, 2005; 364-371.
8. Rutter N. Temperature control and its disorders. In Roberton NRC, eds. Textbook of Neonatology. London, Churchill Livingstone, 1986; 148-161.
9. Rutter N. Thermoregulation in the newborn. In Campbell AGM, McIntosh N. eds. Forfar and Arneil's Textbook of Pediatrics. London. Churchill Livingstone, 1998; 149-150.
10. Oliver TK. Temperature regulation and heat production in the newborn. Pediatr Clin North Am 1965; 12: 765-779.
11. Mann TP, Elliott RIK. Neonatal cold injury due to accidental exposure to cold. Lancet 1957; 2 : 229-234.
12. Daily WJR, Klaus M, Meyer HBP. Apnea in premature infants: Monitoring, incidence, heart changes and an effect of environmental temperature. Pediatrics 1969; 43 : 510- 518.
13. Kaplan M, Eidelman AI. Improved prognosis in severely hypothermic newborn infants treated by rapid rewarming. J Pediatr 1984; 105: 470-474.
14. Racine J, Jarjoui E. Severe hypothermia in infants. Helv Pediatr Acta 1982; 37 : 317-322.
15. Tafari N, Gentz J. Aspects on rewarming newborn infants with severe accidental hypothermia. Acta Pediatr Scand 1974; 63: 595-600.
16. Sarman I, Can G, Tunell R. Rewarming preterm infants on a heated, water filled mattress. Arch Dis Child 1989; 64: 687-692.
17. Yu JS, Jackson R.Neonatal hypothermia in Australia. Practitioner 1974; 213 : 790-794.
18. Hypoglycemia of the newborn. Review of the Literature . WHO/MSM/97.1.1997; 1-16
19. Bruck K, Adams FH, Bruck M. Temperature regulation in infants with chronic hypoxemia. Pediatrics 1962; 30: 350-360.
20. Scopes JW, Ahmed I. Minimal rates of oxygen consumption in sick and premature newborn infants. Arch Dis Child 1966; 41: 407-419.
21. Singh M, Rao G, Malhotra AK, Deorari AK. Assessment of newborn baby's temperature by human touch: a potentially useful primary care strategy. Indian Pediatr 1992; 29: 449-452.
22. Lyon AJ, Pikaar ME, Badger P, McIntosh N. Temperature control in very low birthweight infants during first five days of life. Arch Dis Child Fetal Neonatal Ed 1997; 76: F47-F50.
23. Gandy GM, Adamsons K, Cunningham N, Silverman WA, James LS. Thermal environment and acid base homeostasis in human infants during first few hours of life. J Clin Invest 1964; 43: 751-758.
24. Stephenson JM, Du JN, Oliver TK. The effect of cooling on blood gas tensions in newborn infants. J Pediatr 1970; 76: 848-852.(Mathur NB, Krishnamurthy )
2 Departments of Biochemistry, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India
Abstract
Objectives: To evaluate the time taken for rewarming hypothermic neonates and to correlate the time taken for rewarming with severity of hypothermia (WHO classification), weight, gestational age and associated morbidity. Methods : 100 extramural neonates transported to the Referral neonatal unit of a teaching hospital, with weight more than 1000 grams and abdominal skin temperature less than 36.5 oC at admission were included in the study. Hypothermia was classified as per WHO recommendations. Clinical features including age, weight, gestational age, clinical diagnosis and vitals were recorded at the time of admission. Rewarming was done under a servo-controlled radiant warmer, in skin mode at set temperature of 37 oC. Skin and air temperatures measured by the thermistor probe were recorded at the time of admission and then at least every 15 minutes till skin temperature reached 36.5 oC. The neonates were monitored for oxygen saturation, blood glucose and capillary filling time, and stabilized promptly. Results : The mean abdominal skin temperature was 34.9 ± 1.4 oC. 72% of babies were moderately or severely hypothermic as per WHO classification. The duration of rewarming was 4.9 ± 0.8 min, 17.5 ± 9.5 min and 42±7.9 min for mild, moderate and severe hypothermia respectively (p=0.021). The difference in rate of rewarming between various grades of hypothermia was also significant. The duration of rewarming a baby did not differ significantly between the different weight and gestational age groups. When the rate of rewarming was expressed as rise in oC per Kg body weight per hour, it was higher in smaller and more premature babies. The rate of rewarming was slower in asphyxiated babies. Conclusions : The duration of rewarming depends on the severity of hypothermia. When rewarmed under radiant warmer using servo mode, the duration of rewarming a baby is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.
Keywords: Abdominal skin temperature; Hypothermic neonate; Rewarming time; Transported neonate.
Hypothermia is an important cause of death in the newborn.[1],[2],[3],[4],[5] Sick or low birth weight babies admitted to neonatal units with hypothermia are more likely to die than those admitted with normal temperatures.[4],[6] Information about the time taken for rewarming and the most effective method of rewarming cold infants is scanty[7],[8],[9] and no study has been undertaken in India. Very slow rewarming was tried earlier.[5],[10],[11],[12] Later studies rewarmed severely hypothermic neonates rapidly and found it to be more beneficial.[13],[14] Clear guidelines for duration of rewarming are not available. Devices used for rewarming have been variable in different studies.[13],[15],[16] Hypothermia is associated with marked physiological derangements like hypoxia and hypoglycemia.[17] These require prompt management in intensive care setting. However, most studies on rewarming of hypothermic neonates have not been conducted in an intensive care setting.
This prompted the authors to undertake the present study with the objective of evaluating the time taken for rewarming hypothermic neonates using skin probe and servo proportional warming under radiant warmer and, correlating the time taken for rewarming with the severity of hypothermia,[6]weight, gestational age and associated morbidity in intensive care setting.
Material and Methods
A total of 100 extramural hypothermic neonates transported to a tertiary neonatal intensive care unit constituted the study material. The study was conducted between March and December 2002 and was approved by the institutional research committee. Neonates with abdominal skin temperature less than 36.5 oC at admission were included in the study. Neonates weighing less than 1000 gm were excluded. Rewarming was done under a servo controlled radiant warmer with skin and air probe and temperature display facility. The wattage of the radiant warmer was 600 watts and the distance from the baby was 80 cms. Rewarming was done in skin mode by setting the temperature at 37 oC.[13] Skin and air temperatures measured by thermistor probes were recorded at the time of admission under the radiant warmer and then at least every 15 minutes till skin temperature reached 36.5 oC .[13] The skin probe was placed on the baby's anterior abdominal wall while the air probe was placed by the side of the baby. Rectal temperature was also documented at the time of admission in 70 neonates. This was done by inserting a thermometer into the rectum of the baby at an angle of 30 degrees backward, at a distance of 2 cm from the anal orifice in the case of a preterm baby and 3 cm in the case of a term baby. The thermometer was held for at least 3 minutes.[8] The ambient temperature in the baby care area was 28-32 oC using central air conditioning.
A baby with SPO2 of less than 90% was considered hypoxic. A baby with capillary filling time of more than 3 seconds with feeble peripheral pulses was considered to be in shock. Hypoglycemia was defined as blood glucose of less than 47mg%.[18] Babies who did not cry at birth/had a feeble cry at birth/were in hypoxic ischemic encephalopathy were defined as asphyxiated. The neonates were monitored for oxygen saturation, blood glucose and capillary filling time and stabilized promptly.
The continuous variables were analyzed using student 't' test and proportions by Chi Square test or Fischer test. Probability of 5%was considered significant.
Results
All neonates were monitored for hypoxia, shock and hypoglycemia. Hypoxia, shock and hypoglycemia were detected at admission in 47%, 15% and 35% respectively.
The mean baseline abdominal skin temperature at admission was 34.9 ± 1.4 oC in all hypothermic babies. 72% of babies were moderately or severely hypothermic as per WHO classification. 52% of neonates were delivered at home, while 48% were referred from other hospitals table1.
There was good correlation between rectal and abdominal skin temperatures with the rectal temperature being higher than the abdominal skin temperature by a mean of 0.2 oC and did not change with the severity classification of any baby.
35 babies were of gestational age less than 36 weeks table2. 54 babies weighed less than 2000 gm table3. 56% of babies were asphyxiated, 73% had sepsis, 19% had pneumonia, 17% had meconium aspiration syndrome, 6% had hyaline membrane disease and 14% had meningitis table4.
The duration of rewarming was 4.9± 0.8 min, 17.5±9.5 min and 42 ± 7.9 min for mild, moderate and severe hypothermia respectively (p=0.021). The difference in rate of rewarming (both oC/hour and oC/Kg/hour) between various grades of hypothermia was also significant. (p=0.022 and p=0.04 respectively) table5.
Rate of rewarming expressed as oC per kg body weight per hour (oC/Kg/h) was significantly faster among hypothermic babies of lower gestational age (p=0.028).
However, the difference in absolute time taken for rewarming the baby and rate of rewarming the baby (o C/h) in various gestational age groups was not statistically significant table6.
Rate of rewarming (expressed as rise in temperature per Kg body weight per hour or oC/Kg/h) was significantly faster in hypothermic babies having lower weight (p=0.023). However, the difference in time taken for rewarming and rate of rewarming the neonates expressed as oC/h in various weight groups was not statistically significant table7. The rate of rewarming (oC/Kg/h) was significantly lower in asphyxiated babies (p=0.022)table8.
95% of babies did not experience any problems during rewarming. Two babies had apnea during rewarming, which was attributed to coexisting pneumonia and meningitis. They responded to tactile stimulation. Three other babies developed shock during rewarming because of co-existing sepsis.
Discussion
According to WHO classification of hypothermia,[6] the newborn with a body temperature between 36 and 36.4 o C is under cold stress (mild hypothermia). A baby with temperature between 32 and 35.9oC has moderate hypothermia while a temperature below 32oC is considered to be severe hypothermia.
Kaplan et al[13] studied rewarming of 16 neonates using radiant warmer. The mean time taken for rewarming was 3.96 ± 2.37 hr. Rewarming is facilitated by prompt management of hypoxia and hypoperfusion in the hypothermic neonate. However, there was no mention of monitoring and management of associated morbidities and pathophysiological derangements, and the ambient temperature of the nursery was not stated. The present study has been conducted using radiant warmers with facility for digital display of set and actual temperatures at recommended room temperatures of the nursery in intensive care setting. Hence, it can serve as a guideline and benchmark for smaller community hospitals with less sophisticated radiant warmers and facilities.
In the present study, the mean duration of rewarming using radiant warmer in skin mode was 4.9 min, 17.5 min and 42 min for mild, moderate and severe hypothermia respectively. According to the concept of heat transfer in physics, rise of temperature (t) of a body gaining heat is directly proportional to heat energy provided (H) and inversely proportionate to the mass of the body (m) and its specific heat(s), a constant. It is calculated as follows: t=H/ms. The duration of rewarming a neonate did not differ significantly with varying weight and gestational age. This could be because of the fact that although the larger babies have larger mass to be rewarmed, they also have larger surface area receiving more radiant heat.
When the rate of rewarming was expressed as rise in oC per kg body weight per hour, it was higher in smaller and more premature babies. This is because they have larger surface area per Kg body weight leading to more rapid penetration of radiant heat to the body core .[13]
The rate of rewarming was slower in asphyxiated babies. Non-shivering thermogenesis is known to be impaired in infants following hypoxia or asphyxia. [19],[20]
In the present study, the body temperature was measured by abdominal skin temperature in all the neonates and by rectal temperature in 70 neonates. Good correlation was observed between rectal and abdominal skin temperature with rectal temperature being higher than the abdominal skin temperature by a mean of 0.2oC.
Tafari et al[15] have observed that the rate of rise of abdominal skin temperature and rectal temperature was 1.4oC per Kg per hour and 1.22oC per kg per hour respectively during rewarming of hypothermic neonates.
The abdominal skin temperature in a neonate has been shown to be representative of the core temperature and is reliable for the diagnosis of hypothermia.[21] As the abdominal skin does not vasconstrict, it can be used as an indicator of central temperature.[22] It is easier and safer than using the rectum[22] and has been used in earlier studies on hypothermic neonates.[13],[15],[21],[22],[23],[24]
To conclude, the duration of rewarming hypothermic neonates using radiant warmer in skin mode depends on the severity of hypothermia. It is 4.9±0.8 min, 17.5±9.5 min and 42±7.9 min for mild, moderate and severe hypothermia respectively in intensive care setting at recommended ambient room temperature with prompt management of associated morbidities. The duration of rewarming is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.
Conclusion
The duration of rewarming hypothermic neonates using radiant warmer in skin mode depends on the severity of hypothermia, and is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.
Contributors: NBM conceived and designed the study, analyzed the data, finalized the draft and shall be the guarantor of the paper. SK was involved in protocol preparations, collection of data and drafting the manuscript. TKM participated in protocol preparations, analysis of data and finalizing the manuscript.
Funding: None
Competing interests: None stated.
References
1. Karan S, Rao MN, Urmila S, Rajaji S. The incidence, clinical profile, morbidity and mortality of hypothermia in the newborn. Indian Pediatr 1975; 12: 1205-1210.
2. Day RL, Caliquiri L, Kamenski C, Ehlrich F. Body temperature and survival of premature infant. Pediatrics 1964; 34: 171-181.
3. Silverman WA, Fertig JW, Berger AP. The influence of thermal environment upon survival of newly born premature infants. Pediatrics 1958; 22: 876-886.
4. Daga AS, Daga SR, Patole SK. Determinants of death among admissions to intensive care units for newborns. J Trop Pediatr 1991; 37: 53-55.
5. Arneil GC, Kerr MM. Severe hypothermia in Glasgow infants in winter. Lancet 1963; 2 : 756-759.
6. Thermal Protection of the Newborn: A Practical Guide. WHO/RHT/MSM/97.2.1997; 17-22.
7. Chandra S, Baumgart S. Temperature regulation of the premature infant. In: Avery's diseases of the newborn. Taeusch HW, Ballard RA, Gleason CA. Philadelphia , Saunders, 8th Edition, 2005; 364-371.
8. Rutter N. Temperature control and its disorders. In Roberton NRC, eds. Textbook of Neonatology. London, Churchill Livingstone, 1986; 148-161.
9. Rutter N. Thermoregulation in the newborn. In Campbell AGM, McIntosh N. eds. Forfar and Arneil's Textbook of Pediatrics. London. Churchill Livingstone, 1998; 149-150.
10. Oliver TK. Temperature regulation and heat production in the newborn. Pediatr Clin North Am 1965; 12: 765-779.
11. Mann TP, Elliott RIK. Neonatal cold injury due to accidental exposure to cold. Lancet 1957; 2 : 229-234.
12. Daily WJR, Klaus M, Meyer HBP. Apnea in premature infants: Monitoring, incidence, heart changes and an effect of environmental temperature. Pediatrics 1969; 43 : 510- 518.
13. Kaplan M, Eidelman AI. Improved prognosis in severely hypothermic newborn infants treated by rapid rewarming. J Pediatr 1984; 105: 470-474.
14. Racine J, Jarjoui E. Severe hypothermia in infants. Helv Pediatr Acta 1982; 37 : 317-322.
15. Tafari N, Gentz J. Aspects on rewarming newborn infants with severe accidental hypothermia. Acta Pediatr Scand 1974; 63: 595-600.
16. Sarman I, Can G, Tunell R. Rewarming preterm infants on a heated, water filled mattress. Arch Dis Child 1989; 64: 687-692.
17. Yu JS, Jackson R.Neonatal hypothermia in Australia. Practitioner 1974; 213 : 790-794.
18. Hypoglycemia of the newborn. Review of the Literature . WHO/MSM/97.1.1997; 1-16
19. Bruck K, Adams FH, Bruck M. Temperature regulation in infants with chronic hypoxemia. Pediatrics 1962; 30: 350-360.
20. Scopes JW, Ahmed I. Minimal rates of oxygen consumption in sick and premature newborn infants. Arch Dis Child 1966; 41: 407-419.
21. Singh M, Rao G, Malhotra AK, Deorari AK. Assessment of newborn baby's temperature by human touch: a potentially useful primary care strategy. Indian Pediatr 1992; 29: 449-452.
22. Lyon AJ, Pikaar ME, Badger P, McIntosh N. Temperature control in very low birthweight infants during first five days of life. Arch Dis Child Fetal Neonatal Ed 1997; 76: F47-F50.
23. Gandy GM, Adamsons K, Cunningham N, Silverman WA, James LS. Thermal environment and acid base homeostasis in human infants during first few hours of life. J Clin Invest 1964; 43: 751-758.
24. Stephenson JM, Du JN, Oliver TK. The effect of cooling on blood gas tensions in newborn infants. J Pediatr 1970; 76: 848-852.(Mathur NB, Krishnamurthy )