Morbidly obese patients and anesthesia are far from an ideal mix. These patients often suffer from sleep apnea and typically present with low lung and cardiac reserves. An obese patient's heart pumps at full throttle to barely maintain normalcy and lacks the power for increased output in times of stress ? it's analogous to using a compact car's engine to run a hulking SUV. Even small changes to the obese patient's vital system can cause serious problems, meaning the anesthesia provider must focus on maintaining vital physiological functions in the face of reduced lung capacity and cardiovascular reserve. Here's what you need to know about safe and effective anesthesia administration to your bariatric patients.

Predicting problems
A successful anesthesia provider strives to predict problems before the patient enters the OR. When prepping the bariatric patient, forecasting trouble is even more critical. Anesthesia providers should interview and examine the patient pre-operatively to review assessments by the surgeon, psychiatrist and primary care physician, the patient's lab work, and cardio and pulmonary reports. This physical exam and collection of clinical data are essential to formulating an effective anesthesia plan.

For instance, IVs are difficult to start in the thick arms of bariatric patients. I'll search for accessible veins during the pre-op assessment, create a mental picture of the target area and make a note for recall on the day of surgery. A thorough exam of the patient's airway also lets me plan ways to establish and maintain this critical conduit in the OR.

Obstructive sleep apnea is a common co-morbidity in obese patients and a major concern when evaluating the patient's airway. Fat deposits in the neck can constrict or collapse the airway. Increased abdominal bulk limits the lungs' reserves, emphasizing the need for a patent upper airway and effective ventilation. When compared to other patient populations, proper placement of the endotracheal tube in bariatric patients is essential to preventing hypoxia. The anesthesia provider needs to assess the degree and complications of sleep apnea before surgery, and must also remind apnea patients to bring their continuous positive airway pressure mask and machine on the day of surgery.

Sleep apnea patients are tested and prepared to their optimal levels of pulmonary function prior to surgery. Great care and effort is taken to prevent upper airway obstruction, which is the basis of sleep apnea. Propped up positioning, nasal trumpets, supplementary oxygen, humidifiers, nebulisers, careful reversal of muscle relaxants and CPAP machines are all part of sleep apnea management. Failure to take these measures results in hypoxia and hypercapnia.

Morbidly obese patients generally don't have healthy eating habits. This and metabolic abnormalities make diabetes another common co-morbidity. The patient's diabetes must be under control before surgery and insulin dosage and glucose levels should be monitored closely, as the uncontrolled diabetic state increases the risks of post-op complications, delayed wound healing and surgical infections. There is a growing belief that glucose levels for diabetic patients should be tightly controlled to normal levels during the perioperative period. There is no consensus for the acceptable level of blood glucose. We try to keep blood glucose at normal ranges while preventing hypoglycemia, which is just as damaging to the patient as hyperglycemia.

The patient's prescription medications and use of anti-inflammatory drugs and narcotic painkillers should also be noted. Patients on a regular narcotic regimen, as bariatric patients often are because of back and leg pain, can develop a high tolerance to these drugs and may require higher doses of post-op pain medication in the PACU.

Don't forget about the human side of this procedure. The pre-op meeting is an opportunity to explain possible complications and allay the patient's fears by answering questions about the entire surgical and anesthesia process. Making a human connection has a clinical benefit, after all: A patient's anxiety lowers when a familiar face administers anesthesia, decreasing the amount of pre-op sedation. This lowers the possibility of the patient having anxiety related cardiovascular stress, nausea, vomiting and aspirating during surgery. Understanding the patient's pain threshold can also help establish an effective regimen for controlling post-op discomfort.

Airway maintenance
The excess weight and thickness of the obese patient's neck makes it difficult to visualize the vocal cords and maintain the airway. Difficult airways cause challenging intubations, especially with the patient under general anesthesia. Anesthesia providers may have to intubate with the patient under light sedation. A local anesthetic numbs the airway, and a light sedative relaxes the patient, allowing for the insertion of a fiber optic intubation scope or laryngeal mask airway. Oxygen delivered through nasal cannulae can also aid in maintaining adequate oxygenation throughout this process.

Proper patient positioning can eliminate 90 percent of airway problems that arise during intubation and surgery. The supine position leads to physical discomfort for obese patients and clinical disadvantages to anesthesia providers. When lying flat, the obese patient's midsection presses on the diaphragm, limiting an already-small lung capacity. Gravity's pull on the increased neck mass also puts excess force on the upper airway. This causes the tongue to fall back on the throat and hampers maintenance of a patent airway or visualization of the vocal cords for endotracheal intubation.

Place obese patients on a gentle slope, with the chin higher than the chest. Plenty of commercial devices aid in elevating the patient's head, but consider using a series of folded bed sheets instead. The sheets can be arranged to meet any specification and customized to fit individual patients. I use about 10 to 15 sheets per case. Depending on your laundry fees, using linens may be as cost-effective as using a foam wedge or plastic prop.

While past protocol called for large amounts of a single anesthetic, a more balanced approach is now the standard of care. Small amounts of intravenous and inhalation drugs, muscle relaxants and narcotics control muscle relaxation, amnesia, sleep and pain relief. Cases begin with an IV induction agent plus a muscle relaxant, sleep is maintained using inhalation agents (such as desflurane and sevoflurane) and narcotic medications are administered through an IV during surgery. We generally use propofol and suxemethonium for induction and intubation, using milligrams per kilogram total body weight as a guiding dose. During surgery we continue with short acting inhalation agents such as sevoflurane. Non-depolarizing muscle relaxants, such as rocuronium, and narcotic analgesics are administered. Muscle relaxant and narcotic doses are generally calculated with milligrams per kilogram lean body weight, and titrated to effect.

Anesthesia providers must maintain homodynamic stability and keep the patient properly ventilated during surgery. Surgeons insufflate the abdomen with CO2, expanding its walls to separate the organs and allow for a clear view of them. But it also puts added pressure on the back; the patient's ventilation must be adjusted, filling the lungs with air to counteract the abdomen's push.

More invasive intraoperative monitoring is sometimes required for obese patients presenting with numerous and severe comorbidities. In addition to a peripheral line in the arm or hand, a CVP catheter inserted into the neck, chest or groin can be used to measure heart pressure. Additionally, an arterial line catheter inserted into the wrist measures blood pressure in real-time. While these monitoring techniques are available, you'll rarely need to use them. I've employed invasive monitoring twice in nearly 100 cases; and in those cases the invasive techniques were planned before surgery because the patients had severe co-morbidities and had undergone prior major abdominal procedures.

Less pain, more gain
The endotracheal tube is generally removed on the OR table after anesthetic agents have been stopped and the patient is fully awake. At this point the patient's muscle tone, level of consciousness, airway and pulmonary function are assessed and found to be acceptable for safe extubation and spontaneous ventilation. Patients who don't meet extubation criteria are reassessed in PACU before extubation is considered.

Efforts to control post-op pain actually begin during surgery with a slow IV narcotic titration. When compared to NSAIDs, narcotics are a preferred pain control medicine in bariatric patients. Fentanyl, morphine and hydromorphone are used. We generally avoid using common NSAIDs for fear they can cause internal bleeding at the suture sites, especially in severely obese individuals.

In PACU, titrate the narcotics as needed based on patients' response to pain. Patients should also receive a patient-controlled analgesia pump. Before leaving the PACU, the patients must maintain the airway without aid and should be observed with stable vital signs for at least 45 minutes.

Proper patient positioning in the OR again comes into play during recovery. Obese patients often present with lower back and leg pain. Placing folded sheets under the patient's knees takes pressure off the back during PACU stay and limits post-op discomfort. Patients who awake with more pain than they had before surgery are less willing to ambulate and are therefore at risk for developing post-op thrombophlebitis and pulmonary embolisms.

A complete plan
Anesthetically, obese patients pose many challenges unique to abdominal procedures, including weight-loss surgery. Before surgery, anesthesia providers must assess carefully the patient's medical history and co-morbidities. In the OR, proper patient positioning techniques are essential to establishing and maintaining the airway and in the critical post-op period, you must control pain to get patients comfortable and willing to ambulate.