MMC Bariatrics Guidelines NEW
Richard Flowerdew, August 2009

Introduction Emergence / Post-Op Management
Pre-Op Evaluation Pain Management
Anesthetic Management  
   
Periop Lap Banding Pathway (pdf) Periop Gastric Bypass Pathway (pdf)

Introduction

Patients undergoing bariatric surgery present certain challenges, both  physiological and mechanical. Each of these challenges may require specific medical management protocols in addition to conventional anesthetic management to optimize the patient's surgical and medical outcome. 

These protocols are limited to the factors unique to this group of patients. It will not include factors common to all anesthesia care.


Obesity-Related Physiological Changes

Patients who present for bariatric surgery frequently have several obesity-related co-morbidities, including:

1. Diabetes
2. Sleep Apnea
3. Obesity Hypoventilation Syndrome
4. Hypertension
5. Congestive heart failure
6. Deep vein thrombosis
7. Pulmonary embolism

Mechanical Issues

The bariatric patient may also have several medical/management issues related to the mechanical effects of obesity including:

1. Transfer to and from the OR table
2. Securing the upper limbs
3. Airway management
4. Ventilation and airway pressures
5. Reverse Trendelberg position
   a. Securing the patient to the OR table
   b. Hypotension
6. Post operative comfort [large bed, lifting devices etc.]
7. OR table weight maximum limits


Pre-operative Evaluation

Bariatric patients are best served by being seen pre-operatively in the Pre-Anesthesia Evaluation Unit to evaluate the multiple medical and mechanical issues facing these patients. It is assumed that the appropriate surgical work-up, evaluation, preparation and counseling have already been performed.

Pre-operative anesthetic evaluation, in addition to the usual factors, 
should be focused on the presence of:
1. Obstructive Sleep apnea. [OSA]
   a. Presence
   b. Severity
   c. Support therapies
2. Hypertension
3. Diabetes
4. Airway evaluation
5. Current Medications
    Calcium channel blockers should be discontinued


Anesthetic Management

Pre-operative Medication (Sedation)
Benzodiazepines
   Pro: Anxiolytic; may expand window for airway management
   Con: Potentiate narcotics; prolong recovery of central nervous system
Narcotics [Low dose]
Propofol [Low dose]

Transport/Weight limits
Beds/Stretchers
   Standard hospital bed 500 lb maximum
   Bariatric beds [not regular OR stretchers] are required for patients over 500 lbs.
OR Tables
   OR Table configuration impacts weight bearing capacity (Normal vs Reverse orientation)
   Weights listed in appendix for different OR configurations
Transfer from bed to OR table [and post-operatively when the patient is less able to assist] 
   may benefit from the use of assist devices such as a lateral air transfer device or other lifting 
   devices to protect the patient and the healthcare providers from injury. 
   Please note weight limit on transfer device.

Monitoring
Conventional monitors:
   Non-invasive blood pressure will require large cuffs and/or placement on the forearm.

Central and radial lines:
   not specifically indicated for bariatric surgery unless other patient variables
   [e.g., difficult venous access, extreme obesity, significant cardiac and/or respiratory compromise] 
   indicate the need.

No esophageal or gastric monitor or tube to be placed except on the direction of the surgeon.

Temperature monitoring can be obtained with a naso-pharyngeal probe.

Positioning
   1. Adequate protection of extremities
   2. Protection from sliding down the OR table when in the reverse Trendelenburg [head up] position.
   3. Pillows, other supports or devices under the neck/shoulders may be required to 
       optimize airway management.

Anesthetic Induction
Patients have a higher likelihood for a difficult airway and, with reduced respiratory reserve, may more rapidly desaturate reducing the time for airway management.

A specifically designed foam "wedge" is available in the Anesthesia Workroom to optimize 
patient positioning for intubation


Actual intravenous induction agents and muscle relaxants [short acting/long acting] to facilitate intubation will be patient specific and rely on the medical judgment of the anesthesiologist.

The anesthesiologist must be familiar with the American Society of Anesthesiologists Difficult Airway Algorithm and Practice Parameter.

The availability of the Difficult Airway cart should be ascertained.

Intra-operative patient management
Anesthetic goals include:
  1. Rapidly excreted/metabolized anesthetic agents.
  2. Good operating conditions i.e. minimal muscular activity.
  3. Conducive to cardiovascular stability.
  4. Easily reversed at the end of the procedure with the rapid re-establishment of protective airway reflexes and respiration.
  5. Minimizing the potential adverse impact of OSA
  6. Therapies to minimize post-operative emesis.
  7. Therapies to decrease risk of venous thrombosis and embolism.
  8. Is cost effective.
The actual anesthetic management may be varied to best meet each individual patients medical needs.

Several anesthetic agents, intravenous and volatile, are available. 
  1. Intravenous agents:
    a. Remifentanyl
    b. Propofol
    c. Dexmedetomidine.
  2. Volatile agents:
    a. Desflurane [if no airway reactivity issues]
    b. Sevoflurane.
    c. Combination of agents 

The anesthetic technique should emphasize:
  1. Prevention of respiratory depression
  2. Minimizing the potentiating of obstructive sleep apnea.
  3. Rapidly re-established airway reflexes.

The following factors make bariatric patients at increased risk for post-operative respiratory depression:
  a. High incidence of Obstructive Sleep Apnea. [OSA}
  b. Large fat depots may absorb a greater quantity of anesthetic agent.
  c. Poor peripheral perfusion may both slow uptake and excretion of anesthetic agent from fat depots.
  d. Decreased respiratory function will increase wash-out times.
  e. Narcotics increase the severity of OSA.
  f. Drug doses calculations may be based on either total body weight [TBW] or ideal body weight [IBW] depending on the pharmokinetics and the distribution of the drug. For example, induction with propofol should be based on IBW but if used an infusion on TBW.

Intra-operative surgical testing

The surgeon may require the anesthesia care provider to assist in:
  a. Placing an esophageal bougie.
  b. Inserting an endoscope.
  c. Performing a "leak" test.
  d. Placing an nasogastric tube.

**These procedures are only to be performed on the orders of the surgeon.

Nasogastric tubes may be critical for the post-operative management of the bariatric patient
  a. The marker at the nose should be noted in the anesthesia record as well as in report to PACU.
  b. The tube must be well secured.
  c. Care on transfer from OR bed to stretcher to prevent accidental naso-gastric tube removal.


Emergence/Post Operative Management

The goals for emergence are:
  1. Well established respiratory pattern.
  2. Established protective reflexes.
  3. Minimal nausea and vomiting.
  4. Optimized respiratory patterns.
    a. Head of bed elevated.
    b. Adequate reversal.
  5. Oxygenation.
    a. Supplemental oxygen.
    b. Reduced narcotics and sedatives if possible.
    c. Encouraging deep breathing.
    d. CPAP may be contraindicated for certain procedures [Roux-en-Y]
  6. Monitoring.
    a. PACU times may be extended.
    b. Pulse oximetry may be continued on the floor.
    c. Capnography may be helpful.


Pain Management


Pain management can be complex as narcotics significantly increase the risk for respiratory depression.

Regional analgesia [i.e. epidural] is rarely required and placement can be difficult
  a. Laparoscopic techniques rarely require the level of analgesia produced by epidural analgesia.
  b. Obesity may make it very difficult to locate the epidural space.

Local infiltration of the portal sites by the surgeon is an important element in achieving early analgesia when the respiratory depressant effect of the residual anesthesia is at highest and may have a narcotic sparing effect. Higher concentrations of local anesthetic with epinephrine may extend the duration of analgesia. 

Patient controlled [narcotic] analgesia is an excellent option and well established practice. Continuous basal infusion rates of narcotics should be used with caution especially in patients with OSA. 

Other adjuvant analgesic agents such as tordal and tylenol may help produce analgesia with reduced respiratory depression.