Introduction

Inguinal hernia repair in small infants forms a considerable part of the workload in any specialist paediatric surgical unit. Repair of a large hernia in a preterm infant can be a very difficult operation. Many of these babies will pose considerable anaesthetic challenges not only because of airway and respiratory problems but also because of difficult venous access after weeks of neonatal intensive care. Careful and sometimes intensive peri-operative nursing may be required with such infants being at risk of postoperative apnoea or even requiring postoperative ventilation.

Health resource allocation in the UK is often based on an assessment of workload using classifications such as the International Classification of Diseases (ICD) or Health Care Resource Groups (HRGs). Such coding systems will not identify specific high cost groups and it was the author’s suspicion that neonatal hernia operations would be such a high cost item. Data will be available for the duration of hospital stay for such cases, but the resources required for the actual surgery have not been assessed. The current retrospective study was undertaken to assess the operative and anaesthetic workload produced by such babies and to compare this with standard day-case hernia surgery in older children.

Materials and methods

The retrospective study period was the 3-year period 01 April 1996 to 31 March 1999. Patient details were retrieved from the Neonatal Surgical Unit database of admissions. Only male patients less than 44 weeks post-conceptual age at surgery were included in the study. Gestational age, post-conceptual age, postnatal age, birth weight, admission weight and length of stay were recorded.

The computerised operating theatre records were used to determine the following information:

  1. 1.

    Time of entry into theatre reception

  2. 2.

    Time of entry into anaesthetic room

  3. 3.

    Time of entry into operating theatre

  4. 4.

    Time of entry into theatre recovery area

From this information the duration of time in each area was calculated as well as the combined anaesthetic and operating time and the total time in the theatre complex. The total annual time was calculated to enable assessment of the theatre sessions required each year for neonatal hernia surgery. All patients had correction of a reduced hernia. None were still incarcerated at surgery. It was not possible to assess which patients had been admitted as an emergency. For comparison, the same information was obtained in all children undergoing day-case unilateral hernia repair during the same 3-year period. Operations and anaesthetics in both groups were performed by both consultants and trainees under supervision. It was not possible to analyse the results with respect to seniority of anaesthetist or operating surgeon.

Results

There were 94 neonatal patients in the study period, 68 with unilateral and 26 with bilateral hernias. Demographic data is shown in Table 1. Data is shown for all patients in Table 2, and for unilateral (Table 3) and bilateral (Table 4) hernia repairs. The median anaesthetic time, operating time and combined time for all cases was 20, 50 and 70 min respectively. The same figures for unilateral repair were 20, 45 and 65 min and for bilateral repair 20, 64 and 80 min. There was no significant variation in these times for several categories: <37 weeks gestation at birth, <33 weeks gestation at birth, <37 weeks post-conceptual age at operation, birth weight <1,500 g or operation weight <2,500 g. All 5 cases that had an anaesthetic time >1 h had BW <1,500 g but so did 23 others with shorter times. The same was true for the 6 cases with combined times >2 h. The average annual combined anaesthetic and operating time for all neonatal hernias was 2,469 min which equates to nearly 12 operating sessions of 3.5 h per year.

Table 1 Demographic data on 94 male neonates with inguinal hernia
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Table 2 Operating suite time (minutes) in all cases (n=94)
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Table 3 Operating suite time (minutes) for unilateral hernia repair (n=68)
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Table 4 Operating suite time (minutes) for bilateral hernia repair (n=26)
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During the same 3-year period there were 297 unilateral day-case hernia repairs and data for these patients is shown in Table 5. Median times for this group were 13, 30 and 45 min respectively. Table 6 shows the 95% confidence limits for theatre times for unilateral hernia repairs in neonates and day-cases. Comparing all unilateral neonates with day-cases the anaesthetic takes 54% longer in neonates, the operation 50% longer and the combined time is 55% longer. The range of times shows that some operations can take considerable time. There was a maximum anaesthetic time of 3hr 5 min, a maximum operating time of 2 h 50 min and a maximum combined time of 3 h 30 min.

Table 5 Operating suite time (minutes) for unilateral day-case hernia repair (n=297)
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Table 6 The 95% confidence limits for theatre times (minutes) for unilateral hernia repairs in neonates and day cases
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Bilateral neonatal hernias took the same anaesthetic time but on average took 20 min longer in theatre than unilateral repairs.

Discussion

Paediatric surgeons know that neonatal inguinal hernia repair can be a difficult operation. Many of the babies are preterm infants who have undergone an extensive period of intensive care and have developed a large hernia which may contain lots of intestine. Hernia repair in such babies carries particular risks. Not only can repair compromise ventilation by returning the gut to the abdomen but the risks of postoperative apnoea are well described [1]. Considerable time may be needed to obtain venous access in infants whose veins have already been affected by weeks of intensive care. Once surgery is commenced, repair of a large, thin-walled hernial sac can be extremely difficult and challenging. To the uninformed, particularly those in the health professions who do not have clinical training and may be responsible for resource allocation and funding, there may be no concept that hernia repair in one group of children might be different to another.

Only one study has addressed this issue before in infants [2]. This study looked at the time taken for bilateral inguinal hernia repair in preterm infants with respect to body weight, and whether surgery was carried out within two weeks of diagnosis or later than this. They found that in the early repair group, surgery took a median of 50 min compared to 65 min when surgery took place later. From the results shown in their paper it would appear that the surgical time ranged from 40–220 min.

The current study was undertaken to try to quantify the resources needed to provide a service for neonatal hernia repair. The data shows that for a moderate-sized regional service (annual regional birth rate ~ 30,000) approximately one operating list per month is required for neonatal hernia surgery. On average unilateral hernia repair requires 50% more time than hernia repair in older children. Although some neonatal repairs may only require an anaesthetic and operating time of 30 min others can be highly challenging both for the anaesthetist and for the surgeon, and occasional cases can take up to 3.5 h – a whole operating list!

It does not seem possible to predict which cases will prove most difficult. There was no correlation between anaesthetic or operating time with gestation at birth, post-conceptual age at surgery, birth weight or weight at surgery. Unfortunately, we were unable to assess other factors such as duration of ventilation during neonatal intensive care which might be predictive. Such information could be obtained from a prospective study.

Those involved with the planning and resourcing of health care should be aware of the huge variability in workload in this particular area of specialised surgery. One hernia cannot be assumed to be like any other and information collected from operation coding data may be highly misleading.