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Analytical Data Review of Neonatal Perioperative Care in a UK Neonatal Intensive Care Unit

Gauthamen Rajendran¹, Kokila Lakhoo², Arnwald Choi³, Frances O’Brien*

¹Department of Paediatrics, Bradford Royal Infirmary, Bradford, United Kingdom

²Department of Paediatric Surgery, John Radcliffe Site, Oxford University Hospitals, Oxford, United Kingdom

³Department of Anesthesiology, John Radcliffe Site, Oxford University Hospitals, Oxford, United Kingdom

*Department of Neonatal medicine, John Radcliffe Site, Oxford University Hospitals, Oxford, United Kingdom


Correspondence:

Gauthamen Rajendran

Department of Paediatrics, Bradford Royal Infirmary

Bradford, BD9 6RJ, United Kingdom

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract

Background: There is a paucity of data regarding the perioperative care in neonates.

Objective: To collect data relevant to perioperative care in a neonatal intensive care unit (NICU), with a focus on identifying key areas of clinical care around the time of surgery.

Methods: Perioperative data of neonates who underwent surgical intervention in 2013 within a UK NICU were collected retrospectively. Temperature, blood sugar levels, serum sodium levels, blood gas parameters, weight and fluids used in the perioperative period along with demographic details were collected. The data was analysed for the distribution and trend of temperature, blood sugar and parameters pertaining to fluid, electrolyte and acid-base balance in the perioperative period.

Results: Forty-eight neonatal surgical procedures in 45 neonates were studied. Median gestational age (IQR) at the time of surgery and weight before surgery were 37 (33 to 39) weeks and 2750 (1872 to 2942) grams. The number of surgical procedures for NEC, and abdominal wall defects were 14 and 11 respectively; 23 neonates had surgery for other reasons. Incidence of postoperative hypothermia was 15%. Hyperglycaemia and hypocapnia were more common post-operatively when compared to preoperative findings (63% vs 13% and 19% vs 0% respectively). Hyponatraemia was common preoperatively (42%) but the incidence remained static postoperatively. Hypernatremia was uncommon. A slow and sustained increase in blood sugar levels were noticed in preterm and NEC neonates. Statistically significant weight gain occurred in preterm neonates.

Conclusions: Pre-operative hyponatraemia and post-operative hyperglycemia and hypocapnia require attention. Preterm neonates and neonates with NEC and abdominal wall defects are the high risk groups.

Keywords: newborn, perioperative care, preterm infants, hypothermia, hyperglycemia

 

Introduction

Comprehensive neonatal perioperative care is a complex and rather unravelled topic. The key goal of perioperative care in a neonate is to sustain homeostasis at a time when normal physiological functions are altered by surgical stress, anaesthetic agents and underlying pathology. The management is often guided by local guidelines and practice. Even though it is now well accepted that neonates are not small adults, the paucity of data in the neonatal population often requires the teams involved to extrapolate data from studies involving older children and adults.

In this study we attempted to collect baseline data relevant to perioperative care in a tertiary care neonatal centre, with a focus on identifying areas of acceptable care, areas of specific problems, and areas for further study.

Methods

This is a retrospective analytical data review conducted in a neonatal tertiary care centre in the UK as a part of a quality improvement project. The centre delivers intensive care for extremely preterm neonates and is also the paediatric surgery referral centre in the region. Data from the year 2013 (January-December) were collected. The study population includes all neonates who required surgical management for various pathologies during their period of neonatal intensive care admission. Out of the total 150 paediatric surgical procedures sixty-eight were on neonates. Twenty neonates were transferred to a surgical ward after surgery and hence not included in the study. Data from the remaining 48 neonatal surgeries were collected. Three neonates underwent surgery twice during the period of NICU admission and hence 45 neonates are included in the study (Fig. 1).

Figure 1: Algorithm depicting the selection of neonates for the study.

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Demographic details and perioperative data were collected from clinical notes & nursing charts. Blood gas (capillary or arterial, whichever is available) parameters in the time frame of one hour before and after surgery were gathered. Blood glucose levels and serum sodium levels at 0, 2, 12, 24 hours preoperatively and postoperatively were collected. Temperature documented after the transferring the neonate from surgical theatre to the neonatal intensive care unit was noted. Weight just before surgery and 24 hours after surgery were collected. Details on the maintenance and additional fluid requirement were collected. Data was categorised on the basis of corrected gestational age at the time of surgery (preterm and term) and underlying pathology (Necrotising enterocolitis (NEC), abdominal wall defects and others) for analysis. Neonates with necrotising enterocolitis and spontaneous intestinal perforation were included in the group of “NEC” while neonates with gastroschisis and exomphalos were included in the group of “abdominal wall defects”. The various peri-operative events were defined as follows.

Hypothermia was defined as the axillary temperature recording less than 36.5◦C. Hypocapnia was defined as a pCO2 ≤ 4kPa while hypercapnia was defined as pCO2 > 6kPa during the first 7 days and pCO2 > 8kPa after 7 postnatal days (in preterm babies). Hypoglycaemia was defined as blood sugar level ≤2.6mmol/L and hyperglycaemia is blood sugar level ≥7mmol/L. Severe hyperglycaemia is blood sugar level ≥10mmol/L. Metabolic acidosis is pH less than 7.28 OR base excess >-5.0 OR bicarbonate level less than 18, with or without high lactate level (more than 2.5). Hyponatremia and hypernatremia are serum sodium levels <135mEq/L and >145mEq/L respectively.

Analysis was done using excel 2013. Unpaired student t test was used to evaluate the statistical significance of the variation between groups. P value less than 0.05 was considered statistically significant.

Results

Thirty-two neonates (71.1%) were male and 13 neonates (28.9%) were female. Twenty-three neonates (51.1%) were preterm while 22 neonates (48.9%) were full term at birth. Twenty-two neonates (45.8%) had a corrected gestational age (CGA) of < 37 weeks at the time of surgery and 26 neonates (53.2%) were ≥37 weeks at the time of surgery (Fig. 2). Only 9 of these procedures were after the first week of life while the remaining thirty nine were during the first week (≤ 7days) of life. Necrotising enterocolitis (NEC and spontaneous intestinal perforation) and abdominal wall defects (gastroschisis and exomphalos) were the leading causes of surgical intervention (Fig. 3). 

Figure 2: Distribution of corrected gestational age at the time of surgery

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Figure 3: Bar diagram and table showing the number of neonates who underwent surgery and reason for surgery.

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Post-operative temperature was recorded in 34 cases (71%). Median temperature in this group of neonates was 36.9◦C (Fig. 4) and five (15%) neonates had a temperature less than 36.5◦C (Fig. 5). All neonates were intubated and ventilated in the perioperative period (Fig. 6, 7, 8 and 9).

The range of pCO2 (difference between highest and the lowest values) was higher in the postoperative period overall as well as across individual subgroups (Fig. 7). The median postoperative pCO2 value was lower than the preoperative pCO2 value, overall and in the group of preterm, NEC and other procedures. Nine neonates developed hypocapnia in the postoperative phase compared to no hypocapnia in the preoperative phase (Fig. 5). The incidence of hypercapnia increased from 2 in the preoperative phase to 4 (all neonates with abdominal wall defect) in the postoperative phase. However no statistically significant difference in the median pCO2 values was noted (P value >0.05) when comparing the preoperative and postoperative values. Similarly even though the range of pH was higher in the postoperative period across all subgroups (Fig. 6), there was no statistically significant difference in the median pH values between preoperative and postoperative period.

Figure 4: Box and whisker chart showing the distribution of temperature in 34 cases post operatively.

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Figure 5: Comparison of incidence of hypoglycaemia, hyperglycemia, hypocapnia, hypercapnia, metabolic acidosis, hyponatremia and hypernatremia between the pre-operative (presurgery) and post-operative (post surgery) phases.

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Figure 6: Box and whisker chart showing the distribution of pH values across various subgroups and the comparison of preoperative values with the postoperative values.

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Figure 7: Box and whisker chart showing the distribution of pCO2 values across various subgroups and the comparison of preoperative values with the postoperative values.

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Overall the incidence of metabolic acidosis was higher in the postoperative period (Fig. 5). The range and interquartile range (IQR) of lactate in the postoperative period was lower than the preoperative period across all subgroups (Fig. 6, 8 and 9). Median lactate value increases in preterm and NEC group, postoperatively. The median and the range of distribution of pH in neonates with NEC shifts towards less acidotic values in the post-operative period while it shift towards more acidotic values in neonates with abdominal wall defects. None of these changes showed a statistically significant difference (P value>0.05). The incidence of hypoglycaemia decreased from 5 (10.4%) in the preoperative period to 3 (6.3%) in the postoperative period (Fig. 5). One neonate was hypoglycemic immediately after surgery. The incidence of hyperglycemia increased from 5 (12.8%) to 30 (63.8%) from the preoperative phase to postoperative phase (Fig. 5). Twelve neonates (25.5%) had a blood sugar value higher than 10 mmol/L in the postoperative period. Figure 10 shows the comparison of median blood sugar values at 0hour, 2hour, 12hour and 24hour preoperatively and postoperatively across the subgroups. The pattern observed was a sharp rise in the median blood sugar value soon after surgery which gradually decreased and normalised in the 24 hours of postoperative period. The increase in blood sugar value postoperatively was small, but sustained in preterm neonates. In neonates with NEC the median blood sugar value showed a slow and sustained increase during the first 12hours postoperative period followed by decrease in the blood sugar value.

Figure 8: Box and whisker chart showing the distribution of lactate values across various subgroups and the comparison of preoperative values with the postoperative values.

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Figure 9: Box and whisker chart showing the distribution of bicarbonate values across various subgroups and the comparison of preoperative values with the postoperative values.

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There was a statistically significant difference in the median blood sugar value between preoperative and postoperative period at 0hour, 2 hour and 12 hour. The statistically significant difference was observed across all subgroups except the neonates with NEC who have high blood glucose values preoperatively and postoperatively. The high incidence of hyperglycemia was noted despite a lower glucose infusion rate in the intraoperative period (Fig. 11).

Figure 10: Median blood glucose levels in the perioperative period across various subgroups.

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Figure 11: Glucose infusion rates during preoperative, intraoperative and postoperative periods.

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The incidence of hyponatremia and hypernatremia was the same in both the preoperative and postoperative period (Fig. 5). There was no statistically significant difference in the serum sodium levels in postoperative period across all subgroups. The volume of maintenance fluid used in the preoperative period was compared with that used in the intraoperative and postoperative period. The fluid volume used in the intraoperative period increased in 8 (17%), decreased in 12 (26%) and remained same in 27 (57%) neonates compared to preoperative period (Fig. 12). In the postoperative period the maintenance fluid volume was higher in 17 (37%), lower in 7 (15%) and same in 22 (48%) neonates (Fig. 13). During the intraoperative period fluid bolus and blood products were infused in 41 (85.4%) and 14 (29.2%) neonates respectively. Postoperative weight was measured in 42 neonates. Weight gain was noticed in 28 (60%) neonates while 14 (30%) neonates lost weight in the postoperative period. Figure 14 shows the box and whisker chart depicting the distribution of weight across various subgroups. Range of distribution of weight in the post-operative period increased in preterm neonates, neonates with NEC and abdominal wall defects. Even though the median value of weight increased in the postoperative period across all subgroups, it was statistically significant only in preterm neonates (P value=0.01).

Figure 12: Comparison of maintenance fluid volume used during the pre and intra-operative periods.

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Figure 13: Comparison of maintenance fluid volume used during the pre and post-operative periods.

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Figure 14: Box and whisker chart showing the distribution of weight in subgroups in the pre and post-operative period.

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Discussion

There is a paucity of data on the incidence of abnormalities of temperature and metabolic parameters in the perioperative period in neonates. The data from this service evaluation contributes baseline data regarding the perioperative care in a standard setting in a tertiary care centre. The low incidence of post-operative hypothermia and electrolyte abnormalities in the study population is reassuring. There is increased incidence of hypocapnia and hyperglycemia in the post-operative period. The increase in blood sugar levels in preterm neonates with NEC is slow and sustained unlike in term neonates.

Neonates are more susceptible than older children to perioperative hypothermia [1] due to the higher body surface area to body weight ratio, thin skin [2], and due to the inhibition of the thermoregulatory response by anaesthetic agents [3]. In contrary to most of the previous studies the neonates in the study population showed a lower incidence of hypothermia. Pearce et al. [4] reported a higher incidence of hypothermia in older children and in those undergoing longer, invasive procedures and was associated with greater blood loss and blood transfusion. Tander et al. [1] reported that greater decrease in core body temperature occur in neonates undergoing major surgery than an infant undergoing minor surgery.

All the neonates in our study underwent major surgery and the lower incidence of hypothermia in the study group despite these facts highlights the effective warming mechanisms in the operating theatre and the effectiveness of neonatal transport system in place. Active warming measures include using an under-body mattress, forced-air warming (Bair Hugger 3M) and fluid warming. Radiant overhead heater is often used in extremely premature neonates while carrying out anaesthetic procedures prior to surgery. Usage of cold fluids during surgery is avoided. There is lack of data in the literature relating to the prevalence of hypocapnia and hypercapnia during neonatal perioperative care. Hypocapnia is a potential risk factor for periventricular leukomalacia, cerebral palsy and neuro-cognitive deficits in preterm neonates [5,6,7]. In our analysis 6 term neonates (Tracheo-oesophageal fistula=3, lower GI obstruction=2, abdominal wall defect=1) and 3 preterm neonates had hypocapnia in the postoperative period. The higher incidence in term neonates could be due to the fact that all these neonates had normal respiratory function and were intubated and ventilated for the surgery. It is not clear whether the higher occurrence of hypocapnia in the postoperative period occurs during the transport of the neonate to the intensive care unit or during surgery. Data on the EtCO2 recordings and ventilation during the surgery need to be analysed with other intraoperative data to better elucidate this. Interpretation of the data of metabolic acidosis was complex and difficult due to the multifactorial events. The increase in the median post-operative value of lactate is comparable with the findings by Abubacker et al. [8].

The increased incidence of metabolic acidosis in the post-operative period in neonates with abdominal wall defects calls for a more liberal fluid administration in this subgroup of infants; furthermore this is the group in whom higher CO2 was observed post-operatively in comparison with preoperative values – this could be due to increased intra-abdominal pressure impeding ventilation and thus contributing a respiratory component to the acidosis.

The absence of any change in incidence of hyponatremia and hypernatremia between the preoperative and postoperative period was surprising and reassuring. Nkilly et al. [9] reports that the increased incidence of hyponatremia in the postoperative phase in neonates is associated with the use of hypotonic fluid and increased free water intake during the surgery. Even though hypotonic fluid in the form of 10% dextrose (with or without additives) was used during surgery, free water intake was always less than 6.5ml/kg/hr in all the neonates in the study group and all of them received sodium in the IV fluids in the postoperative period. Fluid of choice for bolus was Hartmann solution. Hartmann’s is one of the closest crystalloid to being isotonic and contains electrolytes in very similar concentrations to those in the extracellular fluid. The lactate present is metabolised to bicarbonate, and this is used in the body to overcome situations of metabolic acidosis, which may occur during surgery.

The higher incidence of hyperglycemia in the postoperative period is interesting. It is known that postoperative hyperglycaemia is a stress response to surgery [10] and that hyperglycaemia is encountered when post-operative pain management is inadequate [10]. The difference in the postoperative glucose “profile” of the different groups of babies could be because there are differences in the stress response of sick preterm neonates or differences in the GIR. The European consensus statement on the intraoperative fluid therapy in children in 2011 [11] recommends the use of a solution with 1% or 2.5% dextrose during the intraoperative period. Murat et al. [12] recommends a glucose infusion rate of 120mg/kg/hour (2mg/kg/min) during the intra/perioperative period to maintain the blood glucose level in the acceptable range and to prevent the lipid mobilisation. This is line with the findings from the studies by Sandstorm K et al, Nishina K et al. [13, 14]. Berleur et al. [15] suggests the use of polyionique B66 (balanced isotonic hydrating solution containing sodium chloride (NaCl) 120 mmol/L plus 0.9% dextrose) for maintenance fluid therapy and replacement of most third-space-compartment losses during surgery. 10% dextrose was the maintenance fluid of choice during surgery in our hospital and the glucose infusion rate ranged from 1.4 mg/kg/min to 9.4mg/kg/min.

The fact that most of the data are extrapolated from evidence in children and the lack of easy access to an appropriately balanced isotonic hydrating solution [16] need to be overcome. Being a retrospective observational study is a limitation of the study. Small sample size is another drawback. This study provides useful information about the trend of various metabolic parameters in the peri-operative period in neonates in a tertiary care setting.

 

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