Childhood obesity and anesthesia

Childhood obesity and anesthesia

Though adult obesity is a well identified and accepted health hazard there is too little information on childhood obesity. As anesthesiologists we are confronted with sever- al challenges while handling childhood obesity. It is observed that number of over- weight and obese children that are presenting for surgery and procedural sedation at healthcare facilities is ever increasing, mostly with no anticipation of the additional care that might be needed to manage them. Since children are continuously growing, even defining obesity in them is not straightforward. The challenges in anesthetising this group of children need to be explored.

The comorbidities are becoming increasingly common in obese children and they might be at greater risk of anesthesia and surgery related adverse events than their non obese counterparts. Several children present to healthcare facilities, often with no anticipation of the greater care that they might need or any additional preparation or challenge they might pose for the anesthesiologist.

Recent literature suggests that obese children are prone to suffer from hypertension,

type II diabetes, asthma, gastro-esophageal reflux, and obstructive sleep apnea just as their adult counterparts. They need to be screened proactively for the major comor- bidities prior to any surgery or procedural sedation. They are at an increased risk of problems occurring at any stage of the anesthetic process, some of which may even be potentially life threatening.

Anesthesiologists will need to have a clearer understanding of the definition of obesi- ty in children, and be able to identify the overweight or obese child and be able to op- timise their perioperative care.

Defining childhood obesity

Obesity in childhood might be far more complicated than can be put in words. Defin- ing obesity is difficult as the child is continuously growing. BMI is continuously changing with age, gender and stature and bears a curvilinear relationship. Hence obesity is not defined as per the adult norms. This is different from how we do things in adults where we look at ranges of BMI with set values. In children e.g. a BMI of 20 in a 3 year child (which is quite thin in an adult) is off the chart heavy. It’s com plex to allocate a normal BMI range for each age group hence by convention we refer to the normal ranges by the percentile on the nomogram graph. For defining obesity in children these charts have to be referred to.; overweight is 85-95 percentile and obese by pediatric BMI is considered over 95 percentile.and morbid obesity is more than the 99th percentile for that age and gender; Figure 1.

Dr aparna sinha
Figure1: Nomogram to assess childhood obesity

Preoperative assessment and Optimisation

Recent literature suggests that obese children suffer from comorbidities such as hy- pertension, type II diabetes, asthma, gastro-oesophageal reflux, and obstructive sleep apnea just as their adult counterparts. The major challenge for the anaesthesiologists here is to effectively screen children for these comorbidities prior to surgery or even procedural sedation

Routine assessment of children should include BMI in addition to vital parameters, BMI and ECG, blood glucose, and cholesterol measurement. Anesthesiologist should actively look for features of sleep disordered breathing. The presenting features of a sleep disordered breathing (SDB) might be vey different from that of adults. Children might be hyperkinetic and have behavioural problems such as, performing poorly in

school, having difficulty in paying attention, learning disabilities and poor weight gain. There may be one or more of the following signs and symptoms:

  • Noisy breathing / Snoring
  • Pauses/obstructed breathing
  • Restless/disturbed sleep
  • Snorting, coughing or choking
  • Mouth breathing
  • Bed wetting
  • Sleep terrors

Some may require overnight oximetry, formal sleep studies, and other respiratory function tests (in selected patients), including arterial blood gas analyses.

One needs to look out for gastro-oesophageal reflux and need for any preoperative medications.

These children are better cared for in facilities with the desired infra structure to sup-

port and perioperative period and this can go a long way in achieving a safe outcome .

Perioperative Management

When the child is an adolescent or a teenager, particular consideration should be giv- en to the seating, wheelchairs, bed width and weight bearing capacity of their beds and operation theater table. Imaging can also raise concerns owing to size and weight. Organising appropriate monitors and equipment, ensuring availability of non invasive ventilation (NIV) in perioperative period can be very vital towards patient safety.

Anesthetic technique

Induction of Anesthesia

For most obese children, intra venous induction is preferred to inhalational induction. Vascular access may pose challenge to the intra venous induction. Considering threat to airway and possibility of airway related adverse events at induction, it might be preferred to achieve vascular access while patient is awake. Ultrasound guidance and use of eutectic mixture of local anesthetic can make the experience safe and comfort- able.

Dexmedetomidine when used intra nasally in the dosa of 0.5 to 1.0 mcg/kg of ideal body weight is an effective and safe option as a sedative pre-medicant. Use of other sedatives prior to induction in the nervous obese child is better avoided due to in- creased risk of postoperative respiratory obstruction.

Airway management

Keeping on mind the challenges associated with the pediatric airway, it can be appreciated that these chal- lenges multiply manifolds in an obese child. While strategising the airway mangement, aim should be to build up the oxygen reserves prior to induction and preventing hypox- emia and airway related adverse events in this period. There is conflicting opinion on the choice of airway device. Some may consider a tracheal tube to be a safer option. However, the supra glottic devices (SGD) have their own set of advantages in partic- ular for minor surgeries. The size of the SGD needs to be carefully selected. Suitable airway adjuncts need to be readily available.

Poor compliance of lungs in the obese child may require optimum ventilatory strate- gy. The currently available anesthesia workstations have multiple options to choose from, to prevent volutrauma and barotrauma. Careful selection of pressures is advis- able to reduce the risk of barotrauma. In absence of these anesthesia-workstations however, attention should be paid to limit the tidal volume to 6ml/kg of IBW. Careful positioning of upper torso is vital for achieving SGD insertion, laryngoscopy and intubation. The child may need to be positioned on to a ramp using readily avail- able pillows and sheets to elevate upper torso. This would help to minimise di- aphragmatic splinting and optimise the FRC.

Application of PEEP and higher ventilatory pressures are beneficial to recruit more alveoli and prevent collapse of bases. Propensity towards peri-operative airway relat- ed adverse events and oxygen desaturation, than their non-obese counter-parts, makes them a high-risk group.

Monitoring

This is an additional challenge while caring for an obese child. Even basic standard monitoring ECG , SpO2 and blood pressure bring their own set of challenges. Non- availability of appropriate blood pressure measuring cuff may interfere with accurate measurement. Invasive arterial monitoring may be a indicated in such circumstances.

Pulse-oximetry can be accomplished with the use of an ear probe or with use of a wrap-around saturation probe.

BIS monitoring may be especially helpful as a guide to adequate depth of anaesthe-

sia. For maintenance sevoflurane or desflurane may be preferred to other inhalational agents because of their low solubility. Several practitioners prefer to use total intra- venous anesthesia using target controlled infusion pumps

Positioning

It is vital to prevent pressure necrosis during prolonged procedures. While simple padding of bony prominences may be all that is required in younger obese patients. The morbidly obese teenagers demand greater attention to detail. The healthcare providers need to be sensitised to these problems. Weight specific operating tables and seats, and careful attention to extremes opposition during surgery as pressure necrosis needs to be prevented.

Dosages of Anesthetics

The dosages of medications in pediatric patients is a complex affair. It can be even more daunting if it is an obese child. The calculations need not be based on the actu- al body weight, rather some anesthetics may need dosing on ideal body weight/lean body mass or even adjusted bodyweight. However, some drugs like, succinylcholine are dosed as per total body weight. Mostly, the other muscle relaxants are adminis- tered as per ideal body weight. Analgesics like paracetamol are dosed as per ideal body weight.

Pharmacokinetics is also significantly altered.In the very obese patients, even lean body mass may not be accurate requiring further dose adjustments; Figure 2.

Figure 2: Dosing scalars for commonly used anaesthetic drugs

   Lean body weight  Adjusted body weight
 PropofolPropofol (Infusion)
 ThiopentalAntibiotics
 FentanylLow molecular weight heparin
 RocuroniumAlfentanil
 AtracuriumNeostigmine (maximum 5 mg)
 VecuroniumSugammadexb
 Morphine 
 Paracetamol 
 Bupivacaine 
 Lidocaine 

Adjusted body weight (ABW)

Takes into account the fact that obese individuals have increased lean body mass and an increased volume of distribution for drugs. It is calculated by adding 40% of the excess weight to the IBW

ABW (kg) = IBW (kg) + 0.4 (TBW (kg) − IBW (kg))

Fluid management

The decision of administration of fluids based on actual body weight based or lean body mass is forever in dilemma. Some procedures, fluid administration may need to be guided by invasive monitoring using stroke volume variation or a haemoglobin and packed cell volume assessment assessment as a guide for blood and fluid re- placement. The latter is a part of goal directed therapy.

Another challenge

Bariatric surgery in adolescents

There have been increasing numbers of children presenting for bariatric surgery, even in India. While behavioral and lifestyle modifications may work most of the obese

children, there are some children, affected by severe obesity, that require more aggressive treatment such as bariatric surgery.

Bariatric surgery, is mostly performed on morbidly obese adults, and has shown to

produce sustained weight-loss and improvement in several obesity-related conditions such as type 2 diabetes, high blood pressure, sleep apnea, polycystic ovarian disease and more. The obese children who get posted for bariatric surgery bring along their own set of challenges. They are at extreme of suffering and may have BMI much greater than their adult counterparts. It is suggested that bariatric surgery should be offered to children in only exceptional circumstances. Some criteria have been laid down for selecting children for bariatric surgery.

  • Child should have nearly achieved physiological maturity
  • BMI of 40 kg /m2 or more, or > 35 – 40 kg/ m2 and other significant disease (e.g. type II diabetes, high arterial pressure, obstructive sleep apnea) that could be im- proved with weight loss
  • Failure of medical measures to maintain weight loss for 6 months
  • Under intensive specialist management
  • Acceptable for general anaesthesia and surgery
  • The family understands need for long-term follow-up.

Majority of the adolescents have significant psychological issues and slow self es- teem owing to their body morphology. The anaesthetic issues relating to them are similar to those of an obese child. Particular attention should be paid to positioning, pain management, thromboprophylaxis, and postoperative care.

Some surgeries may require extremes of positioning like Lloyd Davies position. Foot rests and appropriate restraints should be utilised to ensure that the patient doesn’t slip off. Silicon arm rests or cotton pads can be to prevent pressure areas are well padded to prevent pressure sores. Carboperitoneum and use of liver retractor may hamper lung compliance requiring ventilatory adjustments.

Postoperative pain management

Aim should be minimise the use of opioids or use opioid free techniques like multi- modal analgesia. Wound infiltration with local anaesthesia, appropriate usage of ultrasound guided abdominal field blocks, paracetamol and non-steroidal anti-inflam- matory drugs (if not contra-indicated) and weak opioids such as tramadol may be used. The use of patient-controlled analgesia (PCA) containing morphine or fentanyl may be considered with extreme caution after laparotomies. It is associated with s nausea, sedation, and airway related adverse events, may delay early mobilization and recovery.

Thromboprophylaxis

Obese children are less prone to venous thromboembolism (VTE); how ever due to poor mobility and pro-thrombotic state, post operative period carry risk of developing developing a VTE. Early ambulation and use of mechanical methods such as sequen- tial compression device during surgery with compression stockings applied through the perioperative period. The role of low-molecular-weight heparin is less clear in this age group.

Postoperative care of the obese child

Focus should be on continuous monitoring, oxygen availability, provision for a non invasive ventilation (NIV) device and monitoring in a in a high-dependency unit. Ad- equate numbers of the nursing team and support staff to assist in positioning (usually to be upright as much as possible). Needless to say they should be nursed on the appropriate bed with hydraulic or electrical controls to make positioning a safe and comfortable experience. The post anesthesia care unit should have provision for appropriate monitoring facilities for at least 24 h post-surgery. This will take care of any possible airway related adverse events.

Conclusion

Obese children are at an increased risk of adverse events at every step of the periop- erative process, which may be potentially life threatening. Awareness and prepared- ness on the part of anesthesiologists as a perioperative physicians is of paramount importance.

Suggested Reading

  1. El- Metainy S, Ghoneim T, Aridae E, Abdel Wahab M. Incidence of perioperative adverse events in obese children undergoing elective general surgery. Br J Anaesth 2011; 106: 359–63
  • Cole TJ, Bellizi M, Flegal KM, Dietz WH. Establishing a standard definition or child overweight and obesity worldwide: international survey. Br Med J 2000; 320: 1240–5
  • Tait AR, Voepel-Lewis T, Burke C, Kostrzewa A, Lewis I. Incidence and risk fac- tors for perioperative adverse respiratory events in children who are obese. Anes- thesiology 2008; 18: 375–80
  • Edgecombe H, Carter K, Yarrow S. Anaesthesia in the prone position. Br J Anaesth 2008; 100: 165–83
  • Baerdemaeker L, Mortier E, Strys M. Pharmacokinetics in obese patients. Contin Educ Anaesth Crit Care Pain 2004; 4: 152–5
  • Mortensen A, Lenz K, Abildstrom H, Loritsen T. Anaesthetising the obese child. Paediatr Anaesth 2011; 21: 623–9
  • Lemmens HJM, Brodsky JB. The dose of succinylcholine in morbid obesity. Anaesth Analg 2006; 120: 438–42
  • Smith HL, Meldrum DJ, Brennan LJ. Childhood obesity a challenge for the anaes- thetist. Paediatr Anaesth 2002; 12: 750–61

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