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Cardiotocography
cardiotocography (CTG) is a technical means of recording (-graphy) the fetal heartbeat (cardio-) and
the uterine contractions (-toco-) during pregnancy, typically in the third trimester. The machine used to perform
the monitoring is called acardiotocograph, more commonly known as an electronic fetal monitor (EFM).
The invasive fetal monitoring was invented by Doctors Alan Bradfield, Orvan Hess andEdward Hon. A refined,
non-invasive, beat-to-beat) version was later developed for Hewlett Packard by Dr. Konrad Hammacher.
Schematic explanation of cardiotocography: heart rate (A) is calculated from fetal heart motion determined by
ultrasound, and uterine contractions are measured by a tocodynamometer (B). These numbers are represented
on a time scale with the help of a running piece of paper, producing a graphical representation.
Simultaneous recordings are performed by two separatetransducers, one for the measurement of
the fetal heart rateand a second one for the uterine contractions. Each of the transducers may be either
external or internal.
External measurement means taping or strapping the two sensors to the abdominal wall. The heart (cardio)
sensor is aultrasonic sensor, similar to a Doppler fetal monitor, that continuously emits ultrasound and detects
motion of the fetal heart by the characteristic of the reflected sound. The pressure-
sensitive contraction transducer, called atocodynamometer (toco) has a flat area that is fixated to the skin by a
band around the belly. The pressure required to flatten a section of the wall correlates with the internal
pressure, thereby providing an estimate of it.[1]
Internal measurement requires a certain degree of cervicaldilatation, as it involves inserting a pressure catheter
into the uterine cavity, as well as attaching a scalp electrode to the fetal head to adequately measure the
electric activity of the fetal heart. Internal measurement is more precise, and might be preferable when a
complicated childbirth is expected.
A typical CTG reading is printed on paper and/or stored on a computer for later reference. Use of CTG and a
computer network, allows continual remote surveillance: a single obstetrical nurse, midwife, or obstetrician can
watch the CTG traces of multiple patients simultaneously, via a computer station.
A typical CTG output for a woman not in labour. A: Fetal heartbeat; B: Indicator showing movements felt by
mother (caused by pressing a button); C: Fetal movement; D: Uterine contractions
Interpretation of a CTG tracing requires both qualitative and quantitative description of:
Uterine activity (contractions)
Baseline fetal heart rate (FHR)
Baseline FHR variability
Presence of accelerations
Periodic or episodic decelerations
Changes or trends of FHR patterns over time.
Uterine activity
There are several factors used in assessing uterine activity.
Frequency- the amount of time between the start of one contraction to the start of the next contraction.
Duration- the amount of time from the start of a contraction to the end of the same contraction.
Intensity- a measure of how strong a contraction is. With external monitoring, this necessitates the use of
palpation to determine relative strength. With an IUPC, this is determined by assessing actual pressures
as graphed on the paper.
Resting Tone- a measure of how relaxed the uterus is between contractions. With external monitoring, this
necessitates the use of palpation to determine relative strength. With an IUPC, this is determined by
assessing actual pressures as graphed on the paper
Interval- the amount of time between the end of one contraction to the beginning of the next contraction.
The NICHD nomenclature[2] defines uterine activity by quantifying the number of contractions present in a 10-
minute window, averaged over 30 minutes. Uterine activity may be defined as:
Normal- less than or equal to 5 contractions in 10 minutes, averaged over a 30-minute window
Tachysystole- more than 5 contractions in 10 minutes, averaged over a 30-minute window
Baseline fetal heart rate
The NICHD nomenclature[2] defines baseline fetal heart rate as: The baseline FHR is determined by
approximating the mean FHR rounded to increments of 5 beats per minute (bpm) during a 10-minute window,
excluding accelerations and decelerations and periods of marked FHR variability (greater than 25 bpm). There
must be at least 2 minutes of identifiable baseline segments (not necessarily contiguous) in any 10-minute
window, or the baseline for that period is indeterminate. In such cases, it may be necessary to refer to the
previous 10-minute window for determination of the baseline. Abnormal baseline is termed bradycardia when
the baseline FHR is less than 110 bpm; it is termed tachycardia when the baseline FHR is greater than160
bpm.
Baseline FHR variability
The NICHD nomenclature[2] defines baseline FHR variability as: Baseline FHR variability is determined in a 10-
minute window, excluding accelerations and decelerations. Baseline FHR variability is defined as fluctuations in
the baseline FHR that are irregular in amplitude and frequency. The fluctuations are visually quantitated as the
amplitude of the peak- to-trough in bpm. Using this definition, the baseline FHR variability is categorized by the
quantitated amplitude as:
Absent- undetectable
Minimal- greater than undetectable, but less than or equal to 5 bpm
Moderate- 6 bpm - 25 bpm
Marked- greater than 25 bpm
Accelerations
The NICHD nomenclature[2] defines an acceleration as a visually apparent abrupt increase in FHR. An abrupt
increase is defined as an increase from the onset of acceleration to the peak in less than or equal to 30
seconds. To be called an acceleration, the peak must be greater than or equal to 15 bpm, and the acceleration
must last greater than or equal to 15 seconds from the onset to return. Aprolonged acceleration is greater than
or equal to 2 minutes but less than 10 minutes in duration. An acceleration lasting greater than or equal to 10
minutes is defined as a baseline change. Before 32 weeks of gestation, accelerations are defined as having a
peak greater than or equal to 10 bpm and a duration of greater than or equal to 10 seconds.
Periodic or episodic decelerations
Periodic refers to decelerations that are associated with contractions; episodic refers to those not associated
with contractions. There are four types of decelerations as defined by the NICHD nomenclature.[2]
Early Deceleration: Visually apparent, usually symmetrical, gradual decrease and return of the FHR
associated with a uterine contraction. A gradual FHR decrease is defined as one from the onset to the
FHR nadir of greater than or equal to 30 seconds. The decrease in FHR is calculated from the onset to the
nadir of the deceleration. The nadir of the deceleration occurs at the same time as the peak of the
contraction. In most cases the onset, nadir, and recovery of the deceleration are coincident with the
beginning, peak, and ending of the contraction, respectively
Late Deceleration: Visually apparent usually symmetrical gradual decrease and return of the FHR
associated with a uterine contraction. A gradual FHR decrease is defined as from the onset to the FHR
nadir of greater than or equal to 30 seconds. The decrease in FHR is calculated from the onset to the nadir
of the deceleration. The deceleration is delayed in timing, with the nadir of the deceleration occurring after
the peak of the contraction. In most cases, the onset, nadir, and recovery of the deceleration occur after
the beginning, peak, and ending of the contraction, respectively.
Variable Deceleration: Visually apparent abrupt decrease in FHR. An abrupt FHR decrease is defined as
from the onset of the deceleration to the beginning of the FHR nadir of less than 30 seconds. The
decrease in FHR is calculated from the onset to the nadir of the deceleration. The decrease in FHR is
greater than or equal to 15 beats per minute, lasting greater than or equal to 15 seconds, and less than 2
minutes in duration. When variable decelerations are associated with uterine contractions, their onset,
depth, and duration commonly vary with successive uterine contractions.
Prolonged Deceleration: A prolonged deceleration is present when there is a visually apparent decrease
in FHR from the baseline that is greater than or equal to 15 bpm, lasting greater than or equal to 2
minutes, but less than 10 minutes. A deceleration that lasts greater than or equal to 10 minutes is a
baseline change
Additionally decelerations can be recurrent or intermittent based on their frequency (more or less than 50% of
the time) within a 20 min window.[2]
FHR pattern classification
The NICHD workgroup proposed terminology of a three-tiered system to replace the older undefined terms
"reassuring" and "nonreassuring".[2]
Category I (Normal): Tracings with all these findings present are strongly predictive of normal fetal acid-
base status at the time of observation and the fetus can be followed in a standard manner:
Baseline rate 110-160 bpm,
Moderate variability,
Absence of late, or variable decelerations,
Early decelerations and accelerations may or may not be present.
Category II (Indeterminate): Tracing is not predictive of abnormal fetal acid-base status, but evaluation
and continued surveillance and reevaluations are indicated.
Category III (Abnormal): Tracing is predictive of abnormal fetal acid-base status at the time of
observation; this requires prompt evaluation and management:
Absence of baseline variability with recurrent late or variable decelerations or bradycardia; or
Sinusoidal fetal heart rate.
PhototherapyPhototherapy for newborn jaundice.
Phototherapy is the use of light to treat newborn jaundice. Newborn jaundice is due to the presence of higher than normal level of bilirubin in blood.
Historically, in England some nurses reported that a new, well lit nursery had significantly lesser cases of newborn jaundice when compared to the hospital's older,
darker nursery. Also, some observant nurses from other parts of world reported that babies placed in cribs closer to the window had less jaundice than other babies in the ward. Such observations led to the discovery of the therapeutic effect of light in newborn jaundice.
How does phototherapy cure jaundice?
When baby is placed under a source of blue light (of wavelength 425 to 550 nm), light reacts with bilirubin in the blood flowing through the baby's skin. Bilirubin which is water insoluble is converted to substances like lumirubin which are water soluble and hence easily excreted through poo and urine. Formation of lumirubin is the most important way of excreting the excessive bilirubin. There are other less important ways by which phototherapy aids in excreting bilirubin which includes photo-oxidation and configurational isomerization.
How is phototherapy given?
Phototherapy is given in two ways:
Phototherapy unit: with fluorescent lights (daylight white, blue, green, blue-green), tungsten halogen or quartz halide spotlights, High intensity blue gallium nitride LEDs.
Bilirubin blanket (Bili-blanket) : Light from a high intensity lamp is delivered to a fibre optic blanket.
Tungsten halogen spot light has less spectral power. They are often used as a part of radiant warmer. High intensity Gallium Nitride diodes emit less UV and Infra red radiation and hence the amount light in blue green spectrum can be customised. They can also be brought very close to infants, unlike halogen spot lamps.Gallium nitride LEDs are considered more effective.
Bilirubin blankets are woven fibre optic pads. Halogen light beams from a source (light box) are transmitted though a cord of fibre optic filaments to a flexible pad which is placed beneath or wrapped around the baby. The blanket does not produce heat and delivers light in the 425 to 475 nm range. Generally, as the fibre optic pads cover a small surface of the baby's skin, bili blankets are considered less efficient than conventional phototherapy. They are often used in conjunction with a phototherapy unit. Bili blankets are portable, does not need use of eye pad (because light does not shine directly in to baby's eyes) ,offers chances for bonding and feeding without interrupting phototherapy and is hence preferred by parents. Bilirubin blankets are used for home phototherapy, when the level are in optional range, to prevent further increase in bilirubin level.
Contrary to the popular misconception, Ultra violet rays are not used in phototherapy. What little UV light that the light sources emit, are of longer wavelength than those
causing redness, and even such small amount of emitted UV rays are absorbed by the glass wall of the tubes.
When is phototherapy given?
Babies are treated with phototherapy when it is believed that their bilirubin levels could enter toxic range. Indication for commencing phototherapy depends on each hospital's nursery guidelines.(For example, according to AAP guidelines,healthy term babies at 72 hours of life are started on phototherapy when their bilirubin level reaches 18mg/dl). Sick babies and premature babies are put on a more conservative approach.
How fast does phototherapy act?
The rate at which bilirubin is reduced depends on many factors-
Blue green spectrum is more effective: Hence special LED or special blue tubes which has a maximum output in the blue green spectrum are used for intensive phototherapy.
Closer the infant is to the blue fluorescent tube, faster the clearance will be. It is desirable to place the infant within 10 to 15 cms of the source. However, halogen tubes may cause burns when placed too close and so manufacturer's guidance should strictly be followed in case of halogen tubes.
Area of the baby's body exposed: The baby is placed with only diaper and eye pads. The exposure can be intensified using double phototherapy (blue lights above and below the glass bassinet), or by lining the incubator or warmer bed with aluminium foil.
If there is ongoing production of bilirubin (as in some blood diseases like hemolytic anaemia) it is necessary to start phototherapy at lower levels.
The bilirubin level at diagnosis: For higher bilirubin levels, intensive phototherapy is given.
On an average, in term babies admitted for intensive phototherapy, there is a decline of 30 to 40% in the first 24 hours, the maximum decline being in the first 4 to 6 hours (as much as 0.5 to 1mg/dl per hour decline in the first 4 to 6 hours). With standard therapy there is a 6 to 20% decline in the first 24 hours.
Intermittent versus continuous phototherapy?
Studies have shown conflicting results about whether intermittent phototherapy is as effective as continuous phototherapy. As the most rapid breakdown of bilrubin takes place in the first few hours of commencing phototherapy, in most cases brief periods of interruption for holding and feeding the babies are allowed. But babies with severe jaundice need continuous, intensive phototherapy.
What is intensive phototherapy?
Intensive phototherapy is providing an irradiance in the 430 to 490 nm band (usually 30 µW/cm2per nm) to as much area of the baby's body as possible. This is given by using multiple phototherapy units or by combining phototherapy with fibre optic pads, in an uninterrupted manner. Double phototherapy is twice as effective in preterms and at least 50% more effective in term babies.
When is phototherapy stopped?
There are no specific end point for stopping phototherapy. Judgement depends on individual cases, depending on -weight of baby, if the baby is term or preterm and age of the baby. Generally in healthy term babies, phototherapy is discontinued when the bilirubin level falls to 13 to 15 mg/dl. Babies are followed up for rebound jaundice , where a repeat blood test may be necessary.
What is rebound jaundice?
Rebound jaundice is a surge in bilirubin levels soon after phototherapy is stopped. Rebound jaundice is significant in preemies, babies with positive direct coomb's test (indicating hemolysis) and in babies who have received less than 72 hours of phototherapy. In such cases, a repeat blood test 24 hours after discharge may be necessary.
When is phototherapy dangerous?
Phototherapy is usually a safe procedure.
In a rare genetic condition called, 'congenital porphyria', phototherapy is contraindicated as it causes severe blistering. In jaundice due to liver disease, phototherapy can lead to pigmentation of skin and urine called 'bronze baby syndrome' and in such cases alternative treatment like exchange transfusion is considered. Blistering can also occur in obstructive jaundice.
What are the complications of phototherapy?
Phototherapy has been in use for more than three decades and millions of babies have benefited from phototherapy. Serious side effects are rare and phototherapy is generally considered a simple, safe and cheap procedure. Minor side effects are
Frequent loose stools- green or watery poo is common. This along with increased insensible water loss can lead to dehydration. Frequent bowel movements help in excreting bilirubin and will stop when phototherapy is discontinued. Babies are required to be fed frequently. Dehydration may have to be corrected by supplementing with formula or fluid administration. Over-heating can also occur but is uncommon with LEDs that produce less heat and with fibre-optic blankets.
Baby's eyes are protected by soft eye patches. Although some animal models have shown to develop retinal degeneration on exposure to constant light, similar findings are not documented in humans. Nevertheless baby's eyes are covered with eye pads always.
Babies being kept in isolation and under bright light with eyes covered- there are concerns about this temporary interruption of visual-sensory stimulation (cuddling, being talked to etc) and doubtful alteration in circadian rhythm. Isolation and parental stress can interfere with early baby-parent bonding. These effects can be overcome by allowing the parents to cuddle and bond with baby during brief feeding sessions and alleviating parental anxiety by keeping them informed and reassured. Bilirubin blankets are popular with parents as they are portable and do not interfere with mother-baby bonding and hence are prescribed when clinical situation permits.
What can I do to help my baby who is on phototherapy?
conventional phototherapy
It is generally not necessary to interrupt breastfeeding. If baby has to be supplemented with formula or if breastfeeding has to be interrupted, seek consultation for pumping and maintaining breastfeeding. Make your feeding choices (breast or formula feeding) known to your doctors.
Use the feeding sessions to cuddle and bond with the baby with eye patches taken off (unless baby is on continuous, intensive photo therapy)
Do not apply any cream, lotion or vaseline on baby's skin.
Make sure that as much of baby's skin as possible is exposed to light. Babies are usually naked but for their eye patches and a small diaper. Change diapers whenever soiled.
Always cover the baby's eyes with pads when on phototherapy. Remember to put on the eye patches before switching on the lights,when you place the baby back in the incubator after feeding.Make sure that they are not too tight. Report if you see any redness or discharge in baby's eyes.
Explain to your visitors that your baby has to spend most of his/ her time under the phototherapy lights. They can talk and look at the baby when she is lying under the lights.
Baby's position may have to be changed to maximise exposure. Temperature is recorded frequently to keep the baby warm and avoid overheating.
If you have any questions or doubts, talk with your baby's nurse and doctor. Keep yourself informed and reassured. Stay calm, babies often seem to sense mother's anxiety.
Baby's skin appears bleached as bilirubin is broken down. It becomes impossible to assess jaundice by skin color after exposing to phototherapy
Fibre optic pads (Bili blankets):
Swaddle the baby in the blanket, covering both baby and the fibre-optic pad. Do not wrap the blanket too tight. Baby can also be dressed in a sleeper.
It is important to ensure that the lighted area on the pad is against your baby's skin at all times during treatment. The disposable cover should be the only material between baby's skin and the light emanating surface. Change the disposable cover when soiled. Baby's clothing can be worn over the pad.
When feeding or holding your baby, ensure that the tube is not pulled off and disconnected from the phototherapy unit or light box.
The pad can remain on the baby round the clock ,during feeding and when baby is sleeping. Switch off when you take the baby off for bathing.
Place the light source on a flat stable surface. Do not keep anything on top of the light source or the cable.
Eye patches need not be used as the light does not shine in to baby's eyes.
Call your doctor/nurse if you have any doubts about the use of bili blankets.
Can sunlight be used to treat baby's jaundice?
Although sunlight provides sufficientirradiance in the 425- to 475-nm band to provide phototherapy,AAP does not recommend using sunlight because of the practical difficulties involved in safely exposing a nakednewborn to the sun either inside or outside (and avoiding sunburn)
Barium Enema Introduction
A barium enema is a diagnostic test. During the test, the doctor puts a contrastmaterial called barium into the rectum. Enough barium is given to fill up the colon(large intestines). A plain x-ray of the abdomen is then taken.
By filling the entire cavity of the colon, the doctor can see the contour of the colon's lining. Polyps, diverticula (outpocketings), ulcers, fistula (openings), crypts (certain types of cavities), and inflammatory changes can be detected. Masses (such as tumors) are specifically of interest because this test is often used to screen forcolon cancer.
Primarily, barium enema is used to exclude diseases of the colon such ascolorectal cancer. Over the years, barium enema has been used to evaluate a wide range of other conditions such as these:
o Appendicitis
o Celiac sprue
o Colorectal adenoma (harmless tumors)
o Colonic diverticula (pouches or sacs in the colon)
o Colonic polyps
o Crohn disease
o Diarrhea
o Diverticulitis of the colon
o Chronic intestinal pseudo-obstruction
o Lower gastrointestinal bleeding
o Ulcerative colitis
Although the barium enema was originally intended as a way to diagnose disease, its role has changed. Doctors use the test as a screening tool for certain people who are at risk for colorectal cancer.
Also, a barium enema is used in some cases to treat a condition. The pressure exerted when the barium is put into the colon often results in resolving an intussusception (a telescoping effect in which the colon folds in on itself)—a condition seen in infants.
A modified test, the double-contrast barium enema, has been developed in order to see the mucous membrane in the colon better. This is achieved by using a fluoroscope (a machine for viewing the internal structure) and by manipulating the position of the person and the amount of barium and air that is introduced.
Risks
During the barium enema procedure, the contrast material may perforate the colon and spill into the abdominal cavity. The lining of theabdominal cavity may become infected (the condition is called chemical peritonitis). The colon may narrow and become blocked.
Because of these possible problems, certain people may not be good candidates for this procedure.
The bowel is prepared before the procedure. Anyone undergoing a barium enema must be monitored during the bowel preparation procedure.
Perforation rates among the different types of enemas are probably due more to perforations that occurred prior to the enema, and the pressure exerted within the colon, rather than from the contrast material used.
Barium Enema Preparation
To obtain an accurate x-ray image of the contours of the colon, fecal material must be cleared. This is achieved by a cleansing enema.
o Also, a laxative may be given orally to clear the colon of fecal material that may interfere with the
procedure and the test interpretation.
o Usually, you will not be allowed to take food or fluid after midnight the night before your procedure.
You may be given fluids by IV that contain dextrose(sugar) just prior to the test.
During the Procedure
Barium enema is performed at an outpatient x-ray center or in a major hospital. You usually go home the same day.
When you arrive, the staff will check the last time that you had food or fluids. They will also make sure that your bowel has been prepared adequately (by the cleansing enema or laxative or both).
You will remain awake throughout the barium enema procedure. The contrast material (barium) will be put into the rectum through a plastic tube. Aside from that discomfort, you may feel the pressure of the liquid that is being administered. Otherwise, pain should be minimal.
Several x-rays will be taken. The duration of the whole procedure depends on the speed of the barium to fill the necessary areas of interest, the number of images required to properly evaluate the colon, and whether additional barium or images are required.
After the Procedure
Most people have a short recovery time and go home after the procedure.
The images are read by a qualifiedradiologist who communicates the findings to your doctor who may opt to see the images too. Your doctor usually calls you within a week with the results.
If there are abnormal results such as irregularities in the contour of the colon suggesting abnormal masses, your doctor will discuss additional diagnostic and management plans, which may includebiopsy or surgery.
Next Steps
After you leave the hospital or surgical center, expect your next bowel movement to contain the contrast material.
You should watch for abdominal pain, cramping, or vomiting. Call your doctor or seek medical attention at the nearest medical facility if you have severe symptoms.
When to Seek Medical Care
Call your doctor if you have any of these problems:
o Moderate to severe abdominal pain
o Moderate to severe abdominal bloating
o Constipation
o Severe diarrhea
o Inability to take food or fluids
If you pass dark material or have fresh bleeding in your stools, go to a hospital'semergency department.
In addition, any severe abdominal pain, bloating, or cramping needs evaluation in a hospital.
Radiant warmers versus incubators for regulating body temperature in newborn infants
Infants nursed under radiant warmers have higher insensible water loss, but the limitations in the trials included in this review do not permit the use of this
conclusion as guidance for clinical practice. Where babies must be cared for under radiant warmers, it may be necessary to increase the calculated fluid requirement of treated infants.
RHL Commentary by Ogunlesi TA
1. INTRODUCTION
Hypothermia occurs commonly in newborn infants, primarily as a result of the physiological transition from the relatively warmer uterine environment to life outside the uterus. The incidence of hypothermia has been shown to be inversely related to the gestational age and body weight of the infant (1): the prevalence rises from 29% at the 10th minute of life to 83% at the 60th minute of life (2). One study in Uganda found that up to 85% of babies hospitalized in the country had hypothermia (3), which can cause morbidities like hypoglycaemia, acidosis and sclerema and can be a factor in specific disease conditions like asphyxia, septicaemia and intra-cranial haemorrhage. In addition, mortality among babies who were hypothermic at the point of admission to hospital was found in one study in Nigeria to be as high as 39.7% (4).It is vital to keep newborn babies warm and help them to achieve thermoregulation in order to prevent morbidities and minimize the morbidities and mortality associated with hypothermia. Radiant warmers and incubators are some of the heating devices used for this purpose. Apart from the issue of reduced access to the infant, on the one hand, and protection from excessive handling, on the other, there are other important considerations in the use of heating devices. These include possible alterations of the physical environment and the effects in infants with regards to metabolism, oxygen consumption, fluid and electrolyte balance and weight gain pattern (5). These effects have implications for the caloric, fluid and electrolyte requirements of babies nursed under these heating devices and must be taken into consideration in the management of such babies.The objective of the review was to compare the effects of radiant warmers and incubators on neonatal fluid and electrolyte balance, morbidity and mortality.2. METHODS OF THE REVIEW
The methods used to search for trials were comprehensive, covering all the relevant databases and using specific search terms, but with the restriction of studies published in English alone. The authors sought only randomized controlled trials and quasi-randomized trials. The exclusion criteria included non-availability of data in formats that could be examined by the reviewers.Overall, the methodology was sound, the statistical analysis was adequate and the data are presented in prose and tables with clarity.3. RESULTS OF THE REVIEW
Eight trials with 156 infants were included in the review. Although, most of the infants studied in this review were of very low birth weight, the age at entry into the
studies ranged from 4 hours to 35 days. Overall, the only statistically significant finding was increased insensible water loss [Weighted Mean Difference (WMD) 0.94g/kg/day; 95% confidence interval (CI) 0.47–1.41] among infants nursed under radiant warmers compared to infants nursed in incubators. This translates to a mean increase in insensible water loss among babies nursed under radiant warmers as 22.6 ml/kg/day. Similarly, there was higher oxygen consumption among infants nursed under radiant warmers compared with infants nursed in incubators, but the difference did not reach statistical significance (WMD 0.27ml/kg/min; 95% CI −0.09 to 0.63). In addition, there was no statistically significant difference in other short- and long-term neonatal outcomes such as metabolic rate, time to regain birth weight and diseases such as chronic lung disease, patent ductus arteriosus, infections, necrotizing enterocolitis and intraventricular haemorrhage.There were important shortcomings in the trials included in the review. The trials were heterogeneous in terms of infant characteristics such as age and weight as well as the duration of exposure to interventions. Indeed, six out of the eight reviewed trials adopted the cross-over design. In addition, there were variations in the kinds of cross-over intervention examined: three trials studied only radiant warmers and incubators, while the another three studied clothing, phototherapy and heat shields in addition to radiant warmers and incubators.4. DISCUSSION
4.1 Applicability of the results
Since the trials reviewed were conducted in both developed and developing parts of the world, the results would be applicable to under-resourced settings. The authors of the review concluded that infants nursed under radiant warmers had a significantly higher insensible water loss, but the small number of infants in the trials as well as the methodological problems in the trials would disallow the use of this conclusion as guidance for clinical practice. However, the implication of the findings of this review is that increased insensible water loss must be added to the calculated fluid requirements for infants nursed under radiant warmers. This may appear to give the use of incubators an advantage over radiant warmers since the fluid requirement does not have to be altered, but the restriction of access to the infant nursed inside an incubator is a major hindrance in present-day newborn care.4.2 Implementation of the intervention
Where babies must be cared for under radiant warmers, it may be necessary to increase the calculated fluid requirement of treated infants by 22 ml/kg/day, as suggested in the review. It is important to do this in order to reduce the risk of fluid and electrolytes imbalance in the infants. Additional fluids can be administered as intravenous infusion or as milk given via a nasogastric tube, in cases in which the intravenous route cannot be used. Health-care workers at the primary and secondary levels of care may need to be trained to adopt this practice. However,
the requirement of provision of additional fluids should be adapted (and included in the local guidelines) with regards to special situations, such as infants at risk of inappropriate anti-diuretic hormone secretion from perinatal asphyxia, or those with patent ductus arteriosus who really need fluid restriction as part of their management and yet also need to be nursed under a radiant warmer.4.3 Implications for research
The scope of new trials should be expanded to include extremely low-birth-weight infants and entry into the study should be at birth, but may extend till the end of the newborn period in order to incorporate all the likely physiological changes that need to be considered in the interpretation of the findings. The effects of the interventions on specific neonatal morbidities like metabolic rate, time to regain birth weight, oxygen consumption need to be studied in addition to staff and parents’ satisfaction. Given that most under-resourced settings of the world rely heavily on warm cots for the care of newborn infants, it may be more useful to study also warm cots versus radiant warmer or warm cots versus incubators, with emphasis on both short- and long-term neonatal outcomes.Sources of support: NoneAcknowledgement: Prof. O. F Njokanma of the Department of Paediatrics, Lagos State University College of Medicine, Ikeja, Lagos, Nigeria is appreciated for his useful comments.
Glucose Tests
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Definition
Glucose tests are used to determine the concentration of glucose inblood, urine,
cerebrospinal fluid, and other body fluids. These tests are used to detect an increased
blood glucose (hyperglycemia), a decreased blood glucose (hypoglycemia), increased
glucose in the urine (glycosuria), and a decrease in cerebrospinal, serous, and synovial
fluid glucose.
Purpose
Glucose tests are used in a variety of situations including:
Screening persons for diabetes mellitus. The American Diabetes Association (ADA)
recommends that a fasting plasma glucose (fasting blood sugar) be used to diagnose
diabetes. People without symptoms of diabetes should be tested when they are 45 years
old and again every three years. People in high-risk groups should be tested before the
age of 45 and tested more frequently. If the person already has symptoms of diabetes, a
blood glucose test without fasting, called a casual plasma glucose test, may be performed.
In difficult diagnostic cases, a glucose challenge test called a two-hour oral glucose
tolerance test is recommended. If the result of any of these three tests is abnormal, it must
be confirmed with a second test performed on another day. The same test or a different
test can be used, but the result of the second test must be abnormal as well in order to
establish a diagnosis of diabetes.
Screening for gestational diabetes. Diabetes that occurs duringpregnancy is called
gestational diabetes. This condition is associated with hypertension, increased birth
weight, and a higher risk for preeclampsia. Women who are at risk are screened when
they are 24-28 weeks pregnant. A woman is considered at risk if she is older than 25
years, is not at her normal body weight, has a parent or sibling with diabetes, or is in an
ethnic group that has a high rate of diabetes (Hispanic, Native American, Asian, African-
American).
Blood glucose monitoring. Daily measurement of whole blood glucose identifies diabetics
who require intervention to maintain their blood glucose within an acceptable range as
determined by their physician. The Diabetes Control and Complications Trial (DCCT)
demonstrated that persons with diabetes who maintained blood glucose and glycated
hemoglobin at or near normal decreased their risk of complications by 50-75%. Based on
results of this study, the American Diabetes Association (ADA) recommends routine
glycated hemoglobin testing to measure long-term control of blood sugar.
Glucose tolerance test (GTT). (Delmar Publishers, Inc. Reproduced by permission.)
Diagnosis and differentiation of hypoglycemia. Low blood glucose associated with
neuroglycopenia produces symptoms such as confusion, memory loss, and seizure.
Demonstration that such symptoms are the result of hypoglycemia requires evidence of a
low blood glucose at the time of symptoms and reversal of the symptoms by glucose. In
documented hypoglycemia, blood glucose tests are used along with measurements of
insulin and C-peptide (a fragment of proinsulin) to differentiate between fasting and post-
prandial causes.
Analysis of glucose in body fluids. High levels of glucose in body fluids reflect a
hyperglycemic state and is otherwise not clinically significant. However, low body fluid
glucose levels indicate increased glucose utilization which is often caused
by infection (e.g.,meningitis causes a low CSF glucose); inflammatory disease(e.g.,
rheumatoid arthritis causes a low pleural fluid glucose); or malignancy (e.g., a leukemia or
lymphoma such as Hodgkin's disease infiltrating the central nervous system or serous
cavity).
Precautions
Diabetes must be diagnosed as early as possible. If left untreated, it will result in
progressive vascular disease that may damage the blood vessels,
nerves, kidneys, heart, and other organs. Brain damage can occur from glucose levels
below 40 mg/dL and coma from levels above 450 mg/dL. For this reason, plasma
glucose levels below 40 mg/dL or above 450 mg/dL are commonly used as alert values.
Point-of-care and home glucose monitors measure glucose in whole blood rather than
plasma and are accurate generally within a range of glucose concentration between 40
and 450 mg/dL. In addition, whole blood glucose measurements are generally 10%
lower than serum or plasma glucose owing to the greater water content of the red blood
cells. Results are not definitive beyond the manufacturer's stated measuring range, and
should be repeated as soon as possible to avoid hypoglycemicshock, cardiac arrest,
coma, and other complications of an extremely abnormal glucose result.
Other endocrine disorders and several medications can cause both hyperglycemia and
hypoglycemia. For this reason, abnormal glucose test results must be interpreted by a
physician.
A nurse or phlebotomist who collects the sample for a plasma glucose test should follow
standard precautions for the prevention of transmission of bloodborne pathogens.
Glucose is a labile substance; therefore, plasma or serum must be separated from the
blood cells and refrigerated as soon as possible. Samples that must be transported
unrefrigerated to a distant site should be collected in a tube with an additive such as
sodium fluoride to inhibit glycolysis. Blood glucose methods are largely free of
interferences. However, hemolysis may increase the glucose result when measured by
the hexokinase method, and high levels of ascorbic acid may reduce the glucose result
when measured by the glucose oxidase method. Glycated hemoglobin measurements
may be affected by abnormal hemoglobin pigments, such as methemoglobin and
structural hemoglobin abnormalities such as hemoglobin S. Splenectomy can result in
an increase and hemolytic anemia a decrease in glycated hemoglobin.
Exercise, diet, anorexia, and smoking affect the results of the oral glucose tolerance
test. Drugs that decrease tolerance to glucose and affect the test include steroids, oral
contraceptives, estrogens, and thiazide diuretics.
Description
The body uses glucose to produce the majority of the energy it needs to function.
Glucose is absorbed from the gastrointestinal tract directly and is also derived from
digestion of other dietary carbohydrates. It is also produced inside cells by the
processes of glycogen breakdown (glycogenolysis) and reverse glycolysis (gluconeo-
genesis). Insulin is made by the pancreas and facilitates the movement of glucose from
the blood and extracellular fluids into the cells. Insulin also promotes cellular production
of lipids and glycogen and opposes the action of glucagon which increases the
formation of glucose by cells.
Diabetes may result from a lack of insulin or a subnormal response to insulin. There are
three forms of diabetes: Type I or insulin dependent (IDDM), type II or noninsulin
dependent (NIDDM), and gestational diabetes (GDM). Type I diabetes usually occurs in
childhood and is associated with low or absent blood insulin and production of ketones
even in the absence of stressed metabolic conditions. It is caused by autoantibodies to
the islet cells in the pancreas that produce insulin, and persons must be given insulin to
control blood glucose and prevent ketosis. Type II accounts for 85% or more of persons
with diabetes. It usually occurs after age 40, and is usually associated with obesity.
Persons who have a deficiency of insulin may require insulin to maintain glucose, but
those who have a poor response to insulin may not. Ketosis does not develop under
normal metabolic conditions but may occur withstress. Gestational diabetes is a form of
glucose intolerance that first appears during pregnancy. It abates after delivery, but over
a 10-year span approximately 30-40% of females with gestational diabetes go on to
develop noninsulin dependent diabetes.
There are a variety of ways to measure a person's blood glucose.
Whole blood glucose testsWhole blood glucose testing can be performed by a person in his or her home, or by a
member of the health care team outside the laboratory. The test is usually performed
using a drop of whole blood obtained by finger puncture. Care must be taken to wipe
away the first drop of blood because this is diluted with tissue fluid. The second drop is
applied to the dry reagent test strip or device. All whole blood glucose analyzers use the
glucose oxidase reaction to measure glucose concentration. In the home test kits, the
enzymes glucose oxidase and peroxidase, a buffer, and dye are immobilized on the
testing devise. When the blood contacts the reaction zone, it hydrates the reagents. The
glucose oxidase utilizes oxygen to oxidize the glucose forming gluconic acid and
hydrogen peroxide. The peroxidase enzyme catalyzes the oxidation of the dye by the
hydrogen peroxide producing a colored product. The test strip or device is inserted into
a portable analyzer that measures the amount of color produced. Concentration of
gluocse is determined by comparing the color intensity, called the reflectance density, to
that for a standard measured the same way. Point-of-care devices often utilize the same
method. However, some devices employ the polarographic glucose oxidase method. In
this procedure, the glucose oxidase is impregnated into a glucose permeable
membrane that covers an electrode. Peroxidase and dye are not required. Glucose from
the sample diffuses through the membrane and the glucose oxidase catalyzes the
formation of hydrogen peroxide inside the electrode. The peroxide is unstable and
reforms oxygen and water. The oxygen is reduced at the cathode of the electrode
producing a current that is proportional to glucose concentration.
Fasting plasma glucose testThe fasting plasma glucose test requires an eight-hour fast. The person must have
nothing to eat or drink except water. The person's blood is usually collected by a nurse
or phlebotomist via venipuncture. Either serum, the liquid portion of the blood after it
clots, or plasma may be used. Plasma is the liquid portion of unclotted blood that is
collected in an anticoagulant. The glucose is measured by an enzymatic glucose
method. The glucose oxidase-peroxidase or glucose oxidase-polarographic methods
may be used and are similar to those described above. Two additional methods used
are the hexokinase and glucose dehydrogenase methods. These methods both result in
the production of NADH (NADPH) in proportion to the glucose concentration in the
sample. The reaction is measured in an automated chemistry analyzer which measures
light absorption. The amount of light absorbed by the NADH at 340 nm is directly
proportional to the glucose in the sample. Enzymatic methods measure no sugar other
than glucose, and the same normal range can be used. The ADA recommends a
normal range for fasting plasma glucose of 55-109 mg/dL. A glucose level equal to
greater than 126 mg/dL is indicative
Normal findings for glucose tolerance test (GTT, oral glucose tolerance test [OGTT])
SOURCE: Pagana, K.D. and T.J. Pagana. Mosby's Diagnostic and Laboratory Test Reference. 3rd ed. St. Louis: Mosby, 1997.
Blood test
Fasting 7015 mg/dl (<6.4 mmol/L)
Normal findings for glucose tolerance test (GTT, oral glucose tolerance test [OGTT])
30 minutes <200 mg/dl (<11.1 mmol/L)
1 hour <200 mg/dl (<11.1 mmol/L)
2 hours <140 mg/dl (<7.8 mmol/L)
3 hours 7015 mg/dl (<6.4 mmol/L)
4 hours 7015 mg/dl (<6.4 mmol/L)
Urine test Negative
of diabetes. A fasting plasma glucose level of 110-125 gm/dL is referred to as "impaired
fasting glucose."
Oral glucose tolerance test (OGTT)The oral glucose tolerance test is done to see how well the body handles a standard
amount of glucose. There are many variations of this test. A two-hour OGTT as
recommended by the ADA is described below. The person must have at least 150
grams of carbohydrate each day, for at least three days before this test. The person
must take nothing but water and abstain from exercise for 12 hours before the glucose
is given. At 12 hours after the start of the fast, the person is given 75 grams of glucose
to ingest in the form of a drink or standardized jelly beans. A health care provider draws
a sample of venous blood two hours following the dose of glucose. The serum or
plasma glucose is measured by an enzymatic method. A glucose concentration equal to
or greater than 200 mg/dL is indicative of diabetes. A level below 140 mg/dL is
considered normal. A level of 140-199 mg/dL is termed "impaired glucose tolerance."
Testing for gestational diabetes
The screening test for gestational diabetes is performed between 24 and 28 weeks of
pregnancy. No special preparation or fasting is required. The patient is given an oral
dose of 50 grams of glucose and blood is drawn one hour later. A plasma or serum
glucose less than 140 mg/dL is normal and requires no follow-up. If the glucose is 140
mg/dL or higher, a three-hour oral glucose tolerance test is performed. The same
pretest preparation is followed as for the two-hour OGTT described earlier except that
100 grams of glucose is given orally. Blood is drawn at the end of the fast and at one,
two, and three hours after the glucose is ingested. Gestational diabetes is diagnosed if
two or more of the following results are obtained:fasting plasma glucose greater than
105 mg/dL
one-hour plasma glucose greater than 190 mg/dL
two-hour plasma glucose greater than 165 mg/dL
three-hour plasma glucose greater than 145 mg/dL
Glycated hemoglobin blood glucose test (G-Hgb)The glycated (glycosylated) hemoglobin test is used to monitor the effectiveness of
diabetes treatment. Glycated hemoglobin is a test that indicates how much glucose was
in a person's blood during a two-to three-month window beginning about four weeks
prior to sampling. The N-terminal valine of the beta globin chain of hemoglobin forms
are irreversible amide bond with glucose and other carbohydrates. The additional
carbohydrate increases the negative charge of the hemoglobin molecule. When the
various hemoglobins are separated by chromatography the hemoglobin bound to
glucose is located in the fastest fraction called HbA1c. Since the glucose inside the red
cells is in equilibrium with the plasma glucose, a spurious increase in the plasma level
will increase the percentage of glycated hemoglobin. The test is a measure of the time-
averaged blood glucose over the 120-day life span of the red blood cells. The normal
range for glycated hemoglobin measured as HbA1c is 3-6%. Values above 8% indicate
that a hyperglycemic episode occurred sometime during the window monitored by the
test (two to three months beginning four weeks prior to the time of blood collection). The
following formula estimates the average blood glucose during this window: (% G-Hgb x
33.3 mg/dL) - 86 = average blood glucose. Methods available to measure glycated
hemoglobin include column and high performance liquid chromatography,
electrophoresis, and ion capture. The first three are based upon the fact that glycated
hemoglobin has a greater negative charge than nonglycated hemoglobin. Ion capture is
a novel method based upon the ability of glycated hemoglobin to suppress the
fluorescence of a dye.
The ADA recommends that glycated hemoglobin testing be performed during a person's
first diabetes evaluation, again after treatment is begun and glucose levels are
stabilized, then repeated semiannually. If the person does not meet treatment goals, the
test should be repeated quarterly.
A related blood test, fructosamine assay, measures the amount of albumin in the
plasma that is bound to glucose. Albumin has a shorter half-life than red blood cells,
and this test reflects the time-averaged blood glucose over a period of two to three
weeks prior to sample collection.
Preparation
Blood glucose tests require either whole blood, serum or plasma collected by
venipuncture or finger puncture. No special preparation is required for a casual blood
glucose test. An eight-hour fast is required for the fasting plasma or whole blood
glucose test. A 12-hour fast is required for the two-hour OGTT and three-hour OGTT
tests. In addition, the person must abstain from exercise in the 12-hour fasting period.
Medications known to affect carbohydrate metabolism should be discontinued three
days prior to an OGTT test if possible, and the person must maintain a diet of at least
150 grams of carbohydrate per day for at least three days prior to the fast.
Aftercare
After the test or series of tests is completed (and with the approval of his or her doctor),
the person should eat, drink, and take any medications that were stopped for the test.
The patient may feel discomfort when blood is drawn from a vein. Bruising may occur at
the puncture site or the person may feel dizzy or faint. Pressure should be applied to the
puncture site until the bleeding stops to reduce bruising. Warm packs can also be
placed over the puncture site to relieve discomfort.
Complications
The patient may experience weakness, fainting, sweating, or other reactions while
fasting or during the test. If this occurs, he or she should immediately inform their
physician or nurse.
Results
Normal values listed below are for children and adults. Results may vary slightly from
one laboratory to another depending upon the method of analysis used.
fasting plasma glucose test: 55-109 mg/dL
oral glucose tolerance test at two hours: less than 140 mg/dL.
glycated hemoglobin: 3-6%
fructosamine: 1.6-2.7 mmol/L for adults (5% lower for children)
gestational diabetes screening test: less than 140 mg/dL
cerebrospinal glucose: 40-80 mg/dL
serous fluid glucose: equal to plasma glucose
Blood glucose test (blood sugar, fasting blood sugar [FBS])
SOURCE: Pagana, K.D. and T.J. Pagana. Mosby's Diagnostic and Laboratory Test Reference. 3rd ed. St. Louis: Mosby, 1997.
Normal findingsPossible critical values
Cord 456 mg/dl (2.5.3 mmol/L)
Premature infant 200 mg/dl (1.1.3 mmol/L)
Newborn 300 mg/dl (1.7.3 mmol/L) <30and>300 mg/dl
Infant 400 mg/dl (2.2.0 mmol/L) <40 mg/dl
Blood glucose test (blood sugar, fasting blood sugar [FBS])
Child <2 years 6000 mg/dl (3.3.5 mmol/L)
Child>2 years to adult
7005 mg/dl (3.9.8 mmol/L)
Male:<50and>400 mg/dlFemale:<40and>400 mg/dl
Elderlyincrease in normal range after age 50 years
synovial fluid glucose: within 10 mg/dL of the plasma glucose
urine glucose (random semiquantitative): negative
For the diabetic person, the ADA recommends an ongoing blood glucose goal of less
than or equal to 120 mg/dL.
The following results are suggestive of diabetes mellitus, and must be confirmed with
repeat testing:
fasting plasma glucose test: greater than or equal to 126 mg/dL
oral glucose tolerance test at two hours: equal to or greater than 200 mg/dL
casual plasma glucose test (nonfasting, with symptoms): equal to or greater than 200
mg/dL
gestational diabetes three-hour oral glucose tolerance test: two or more of the limits below
are exceeded
fasting plasma glucose: greater than 105 mg/dL
one-hour plasma glucose greater than 190 mg/dL
two-hour plasma glucose greater than 165 mg/dL
three-hour plasma glucose greater than 145 mg/dL
Health care team roles
Prior to the test the health care professional administering an OGGT should describe
the symptoms of hypoglycemia to the patient and tell the patient to alert a health care
worker should he or she experience any of those symptoms. A phlebotomist, or
sometimes a nurse, collects the blood, and a clinical laboratory scientist,
CLS(NCA)/medical technologist, MT(ASCP) or clinical laboratory technician
CLT(NCA)/medical laboratory
technician MLT(ASCP) performs the testing. Results are interpreted by a physician.
Critically high or low glucose levels should be immediately called to the attention of the
patient's nurse or doctor. Physicians and nurses are responsible for educating patients
about how to best manage their diabetes.
KEY TERMS
Diabetes mellitus disease in which a person cannot effectively use glucose to meet the
needs of the body. It is caused by a lack of the hormone insulin.
Glucosehe main form of sugar (chemical formula C6H12O6) used by the body for
energy. Glycated hemoglobin test that measures the amount of hemoglobin bound to
glucose. It is a measure of how much glucose has been in the blood during a 2-3 month
period beginning approximately one month prior to sample collection.
