Specific Aspects of Anesthesia Management in Patients With Obesity and Obstructive Sleep Apnea

The worldwide prevalence of obesity has been increasing. As a result, the number of patients with obesity encountered in the operating room is also rising.

Obesity is generally diagnosed based on the body mass index (BMI), calculated as weight (in kilograms) divided by height squared (in meters): weight (kg) / height² (m²). Overweight is defined as BMI ≥ 25, while obesity is established as BMI ≥ 30.

Obesity-Associated Physiological Changes

Body fat distribution is classified as peripheral adiposity or central adiposity. Patients with central (visceral) obesity face greater perioperative risks and are more likely to develop metabolic syndrome, which includes central obesity, hypertension, insulin resistance, and dyslipidemia. Note that central obesity is more common in men. A diagnostic criterion is waist circumference which should exceed 102 cm in men and 88 cm in women.

Respiratory Physiology Changes

Obesity increases the mechanical load on lung tissue and the thorax, and the metabolic demands of excess adipose tissue also rise. This leads to increased work of breathing, higher oxygen consumption, greater carbon dioxide production, and ventilation–perfusion mismatch. As a result, obesity implies reduced functional residual capacity (FRC), disruption of ventilation–perfusion ratios, and shunting in dependent lung regions.

These combined effects lead to:

• Shortened time to desaturation during periods of apnea;
• Increased O₂ requirements;
• Hypoventilation during spontaneous breathing in the supine position.

The supine position and obstructive sleep apnea (OSA) further exacerbate these effects.

Cardiovascular System Changes

Obesity contributes to elevated blood pressure and is associated with volume overload, which leads to adverse changes in left ventricular (LV) parameters, such as increased end-diastolic volume and elevated filling pressures. These alterations may result in left ventricular hypertrophy (LVH) and subsequently increase the risk of heart failure, ventricular arrhythmias, death from myocardial infarction, and sudden cardiac arrest.

Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a sleep‑related breathing disorder characterized by recurrent episodes of upper airway collapse, leading to reduced inspiratory airflow that may be complete (apnea) or partial (hypopnea).

Recurrent upper airway obstruction during sleep is associated with intermittent hypoxia and hypercapnia. Moderate and severe OSA pose significant risks for acute cardiovascular morbidity and mortality.

A diagnosis of OSA is associated with difficult airway management, postoperative desaturation and respiratory failure, opioid‑induced respiratory depression, and an increased incidence of postoperative cardiovascular complications.

Coagulation Status

Obesity is a prothrombotic condition associated with increased morbidity and mortality from thrombotic complications (myocardial infarction, stroke, venous thromboembolism).

The postoperative hypercoagulable state (thrombophilia) may persist for more than two weeks, necessitating postoperative thromboprophylaxis.

Insulin Resistance

This patient population requires careful monitoring of glycemic status, as poor glycemic control is associated with increased morbidity and mortality.

Dosing and Selection of Anesthetic Agents

Optimal methods for calculating anesthetic doses in patients with obesity remain limited. A gradual, titrated approach to dosing is recommended. In patients with severe obesity, the therapeutic dose range for many drugs may be very narrow, while the number of side effects may increase.

Drug dosing in patients with obesity is based on:

• Actual total body weight (TBW).
• Ideal body weight (IBW), a calculated value representing the weight associated with maximal life expectancy; this parameter is height- and sex-dependent. Common regional IBM formulas include:
  • Men: IBW (kg) = height (cm) – 100;
  • Women: IBW (kg) = height (cm) – 105.
• Adjusted body weight (AdjBW) accounts for increased lean mass in patients with obesity:
  • AdjBW = IBW + (0.4 × [TBW – IBW]).
• Lean body weight (LBW) refers to body weight excluding fat mass. There are other formulas that do not utilize TBW. LBW rarely exceeds 100 kg in men and 70 kg in women:
  • LBW (kg) = (9270 × TBW [kg]) / (8780 + (244 × BMI [kg/m²])).

Pharmacokinetic Considerations and Drug Use

Unlike hydrophilic drugs, lipophilic drugs have a larger volume of distribution. However, determining the volume of distribution in patients with obesity is challenging.

For most medications, dosing based on TBW is inappropriate due to the risk of overdose. To avoid overdosing as well as underdosing, AdjBW or LBW is generally preferred.

When using induction agents, TBW‑based dosing results in a longer duration of action than dosing based on LBW or AdjBW, but may cause significant hypotension.

Hydrophilic drugs such as neuromuscular blocking drugs (NMBDs) distribute primarily into central compartments. For example, a TBW‑based rocuronium dose does not significantly shorten onset time but markedly prolongs duration of action. Doses of neostigmine and sugammadex depend on the timing and total dose of neuromuscular blockers requiring reversal and may be titrated to effect.

Target‑controlled infusion (TCI) of propofol is unreliable in patients weighing more than 150 kg; commercially available pumps typically do not allow weight inputs above 150 kg or BMI > 35 kg/m².

The high prevalence of OSA among patients with obesity may be associated with increased sensitivity to anesthetic agents. It is recommended to minimize the use of respiratory depressants, prefer short‑acting agents, and employ multimodal analgesia with opioid‑sparing protocols to ensure rapid recovery of consciousness and protective reflexes.

Preoperative Preparation

According to the Society for Obesity and Bariatric Anaesthesia (SOBA), special attention should be given to screening patients with higher risk factors using the Obesity Surgery Mortality Risk Score (OS‑MRS) and the STOP‑Bang questionnaire for OSA risk.

Risk factors include:

• Metabolic syndrome;
• Low functional capacity;
• Abnormal ECG;
• Uncontrolled hypertension;
• Chronic heart failure (CHF) or ischemic heart disease (IHD);
• SpO₂ < 94 % on room air;
• Elevated bicarbonate level > 27 mmol/L (suggestive of hypoventilation);
• History of deep vein thrombosis or pulmonary embolism;
• STOP‑Bang score of 5;
• OS‑MRS score > 3.

If identified, risk factors may require preoperative arterial blood gas analysis, polysomnography or overnight oximetry, preoperative CPAP therapy in patients with OSA, referral to a cardiorespiratory expert, and more thorough postoperative monitoring.

Preoperative counseling should emphasize smoking cessation, preoperative diet, the need for thromboprophylaxis, and early mobilization.

Monitoring and Technical Considerations

Ultrasound may be required in patients with obesity to facilitate vascular access, neuraxial anesthesia, or nerve blocks. Operating table extenders or specialized bariatric tables may also be necessary.

In patients with obesity, blood pressure cuffs often need to be applied in a criss-crossed manner, which may reduce accuracy. Alternative cuff sites (e.g., forearm or calf) are frequently used to improve fit. Invasive blood pressure monitoring should be considered when the surgical procedure and/or the patient’s condition indicate a critical need for precise hemodynamic monitoring.

Airway and Intubation Risk Assessment

SOBA recommends that the prognosis of patients with an OS‑MRS score > 3 be discussed with a consultant, and that patients with a score of 4–5 receive anesthesia from an anesthesiologist experienced in managing this population. In approximately 30 % of cases, obesity is associated with a higher likelihood of difficult or failed intubation, complicated laryngoscopy, and bag‑mask ventilation. For elective surgery, shaving facial hair is recommended, as a beard may also interfere with effective ventilation. Patients whose sleep‑disordered breathing is adequately treated show lower perioperative risk.

Assessment of physical exercise tolerance helps identify patients at high risk for postoperative complications.

Fasting Recommendations

Patients with obesity should follow standard preoperative fasting ASA guidelines. For patients without additional aspiration risk factors (gastroesophageal reflux, intestinal obstruction), this includes: fasting from clear liquids for 2 hours, fasting from solid food for 6 hours, fasting from meals high in protein or fat for 8 hours.

Use of Specialized Medications

Glucagon‑like peptide‑1 (GLP‑1) receptor agonists (e.g., semaglutide), dual glucose‑dependent insulinotropic peptide receptor agonists, and sodium–glucose cotransporter‑2 inhibitors are more and more used for weight reduction and for treatment of other conditions (e.g., diabetes) in patients receiving perioperative care. These medications may be associated with a risk of perioperative pulmonary aspiration or euglycemic diabetic ketoacidosis.

According to the 2025 interdisciplinary consensus, patients receiving GLP‑1 receptor agonists and dual glucose‑dependent insulinotropic peptide receptor agonists should continue these medications throughout the perioperative period. However, sodium–glucose cotransporter‑2 inhibitors should be withheld the day before the procedure as well as on the day of the procedure; the regimen is then resumed 24–48 hours after surgery. Gastric ultrasound should be considered before induction of anesthesia. These patient population may also require rapid‑sequence induction and intubation (RSII).

Anesthesia Management

Whenever regional anesthesia is feasible, general anesthesia should be avoided, and sedation during regional anesthesia should be minimized.

Induction of Anesthesia

The preferred method of securing the airway is tracheal intubation with controlled ventilation.

During induction, the patient should be positioned in a ramped or head‑elevated position (the tragus aligned with the sternum, with the arms positioned away from the thorax). This improves lung mechanics and maximizes safe apnea time. Positive end‑expiratory pressure (PEEP) or high‑flow nasal oxygenation facilitates preoxygenation. To maximize safe apnea time, an end‑tidal O₂ concentration above 90 % should be targeted. Any difficulty with airway management should be addressed according to the Difficult Airway Society (DAS) recommendations.

Endotracheal tube size and tidal volume during controlled ventilation are determined based on a patient’s IBW. PEEP titration strategy and recruitment maneuvers reduce intra‑ and postoperative atelectasis.

Two peripheral intravenous lines are recommended; in cases of failed peripheral cannulation, central venous access should be considered.

Maintenance

Sources on inhalational versus intravenous anesthetics in patients with severe obesity contain conflicting data regarding the most preferable agent.

Perioperative strategy should include:

• Use of short‑acting medications;
• Use of depth‑of‑anesthesia monitoring and neuromuscular monitoring to reduce anesthetic burden;
• Maximal use of local anesthesia and multimodal techniques to achieve opioid‑sparing anesthesia;
• The head‑elevated position maintained throughout the procedure;
• Tidal volume set at 6–8 mL/kg of IBW;
• The fraction of inspired oxygen (FiO₂) limited to the level required to maintain peripheral oxygen saturation (SpO₂) > 92 %
  (ideally FiO₂ below 0.5–0.8) to prevent absorption atelectasis and oxygen toxicity;
• Cautious use of recruitment maneuvers (incremental increases/decreases in PEEP) and avoidance in hemodynamically unstable patients (PEEP of 15 cm H₂O improves oxygenation in patients with severe obesity during laparoscopy);
• For laparoscopic surgery, a slight sitting position increases diaphragmatic excursion and modestly reduces airway pressures.

Emergence From Anesthesia

Patients with obesity have a higher incidence of complications during extubation. To reduce the likelihood of such complications and assess readiness for extubation, quantitative neuromuscular monitoring is recommended. Neuromuscular blockade may be reversed with sugammadex or neostigmine (depending on the neuromuscular blocker used). Before tracheal extubation, patients must regain motor function, demonstrate recovery of airway reflexes, and have adequate tidal volumes. Extubation should be performed with the patient awake and in a sitting position. Premature extubation should be avoided in patients with obesity, as post‑procedural airway edema may further complicate an already difficult airway.

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Postoperative Care

Postoperative management for most patients with obesity should follow enhanced recovery strategies. Patients with comorbidities, high‑risk scores (OS‑MRS 4–5), untreated OSA, or a need for postoperative parenteral opioids require more careful monitoring, especially for hypercapnia in the postoperative period. In the postanesthesia care unit (PACU), patients should undergo continuous pulse oximetry until they demonstrate the ability to maintain adequate oxygenation at rest.

Patients with hypoxia unresponsive to standard oxygen therapy should receive noninvasive ventilation with continuous positive airway pressure (CPAP), bilevel positive airway pressure (BiPAP), or high‑flow nasal oxygen (HFNO) in the postoperative period.

Patients with OSA are advised to bring their personal CPAP devices in advance for use during recovery and afterward.

Given the risk of venous thromboembolism, adequate thromboprophylaxis is essential and should be continued after discharge. Below‑knee compression stockings should also be discussed with the patient beforehand.

Conclusion

Patients with obesity and OSA require a preplanned anesthetic strategy due to the combination of rapid loss of respiratory reserve, high risk of difficult airway management, and increased sensitivity to opioids. Key safety principles include optimized preoxygenation and positioning, a first‑attempt success strategy for intubation, lung‑protective ventilation with recruitment maneuvers as indicated, strict prevention of residual neuromuscular blockade at extubation, opioid‑sparing techniques throughout the perioperative period, and early mobilization, which helps reduce respiratory and thrombotic complications and accelerates recovery.