Perioperative management of the obese patient.

Patients that are obese present a unique set of challenges and considerations in their peri-operative nursing management.
And it is more than just the nursing care around preventing pressure wounds and performing physical re-positioning that we must be aware of.

In the UK alone between 2002 & 2012 there was an eleven-fold increase in the number of patients admitted to hospital with a primary diagnosis of obesity.
An open access article published in the journal of Anaesthesia presents guidelines for the peri-operative management of obese patients and the associated problems in caring for them. It is worthwhile saving for future reference.

Here is a quick summary of some of the more salient nursing related points covered.

Weight formulas:

Total body weight TBW:  The actual weight of the patient

Ideal body weight IBW:  What the patient should weigh if they had normal ratio of lean to fat mass. Varies with age.

IBW = height (cm) – X (where X=105 in females and 100 in males)

Lean body weight LBW:  Patients weight excluding fat. Calculation is complicated but it rarely exceeds 100kg in males and 70kg in females.

Adjusted body weight ABW obese patients have increased lean body mass and increased volume of distribution for drugs Even more complicated

Fat distribution:

Patients with intra-abdominal fat deposits are at greater peri-operative risk than those with peripherally distributed fat.

This form of obesity is defined as a waist circumference greater than 88cm in females and 102cm in males ( or a waist-to-height ratio greater than 0.55).

These patients are more likely to experience metabolic syndrome (central obesity, hypertension, insulin resistance and hypercholesterolemia).

Obstructive Sleep Apnoea:

Obstructive sleep apnoea (OSA) occurs in 10–20% of obese patients.
OSA doubles the risk of postoperative desaturation, respiratory failure, cardiac events and ICU admissions. If OSA is identified pre-operatively and managed with continuous positive airway pressure (CPAP) therapy these complications are significantly reduced.

OSA may progress to obesity hypoventilation syndrome: obesity, OSA and daytime hypercapnia. This group of patients is particularly susceptible to the effects of anaesthetic agents and opioid analgesia. Watch them carefully for signs of hypoventilation and impending respiratory arrest in the early postoperative period.

Cardiovascular:

Obesity leads to increased blood pressure, cardiac output and cardiac workload. These patients are more likely to have cardiac arrhythmia’s such as atrial fibrillation. They are also at increased risk of sudden cardiac death.
Heart failure and ischaemic heart disease are increased risk factors in this population.

Obese patient are at an increased risk of prolonged QT intervals which can precipitate the life threatening arrhythmia Torsade de Pointes.
So care must be taken when giving drugs that also prolong QT such as ondansetron (more info on this here and here)

Thrombosis:

Obesity associated with increased risk of thrombotic disorders such as myocardial infarction, stroke and venous thromboembolism.

Strategies to reduce VTE include:

  • Early postoperative mobilisation
  • Mechanical compression devices
    thromboembolic (TED) stockings
    anticoagulant drugs
  • Currently limited evidence to support use of TED stockings in obese patients, but if used must be fitted correctly to avoid vascular occlusion.

ICU care:

All airway interventions carry increased risk of hypoxia and complications.
Tracheostomy may be performed if long term airway management is anticipated.
For calculating ventilator Tidal Volumes, ideal body weight should be used.

General nursing care:

Fat has a relatively low blood flow so calculating drug doses to total body weight risks overdose. It is preferable to base doses on lean body weight and titrate to effect.

Patient controlled analgesia (PCA’s) should be used with care due to the risk of respiratory depression in patients with sleep breathing disorders (which may be yet undiagnosed).

IMI drug administration should be avoided in obese patients due to unpredictable pharmacokinetics.

Oxygen therapy should be maintained postoperatively until baseline saturation are achieved & parenteral opioids no longer required.


Reference:

Peri-operative management of the obese surgical patient 2015 – – 2015 – Anaesthesia – Wiley Online Library. (n.d.).Available from http://onlinelibrary.wiley.com/enhanced/doi/10.1111/anae.13101/

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