Due to the difficulty in enrolling a large number of super obese patients (body mass index, BMI > 50 kg m−2) the anaesthetic management of these patients is still inferred from evidence based on obese or morbidly obese patients . We report a case of a 35-year-old 220-kg male, ASA III, scheduled for laparotomy with Roux-en-Y gastric bypass. His height was 172 cm, BMI 74.7 kg m−2, with an ideal body weight of 74 kg. Thus his real body weight was 298% of his ideal weight with a weight excess of 147 kg. Anaesthesiology evaluation 12 days prior to surgery revealed: hypertension (160/90 mmHg), oesophagitis (primary grade, Savary classification), mild hyperuricaemia, hyperinsulinaemia and increased hepatic enzymes. Abdominal echography was normal as well as electrocardiogram and spirometery. Given the neck circumference of 52 cm and Mallampati class III airway, awake intubation was discussed and planned with the patient, who appeared motivated regardless of the possible discomfort of the procedure.
The day before surgery, omeprazole 20 mg was commenced twice a day orally and crystalloids 2000 mL overnight were administered. Omeprazole 40 mg was given intravenously (i.v.) 1 h prior to arrival in the operating room. Following standard monitoring, the left radial artery was cannulated. The patient tolerated well the awake autocalibration of neuromuscular function monitoring train-of-four (TOF-Watch). Midazolam 0.05 mg kg−1 (based on ideal body weight) was then administered. Following topical anaesthesia, awake fibreoptic endotracheal intubation was performed. The epiglottis appeared small and moderately hypertrophic. Immediately after placing the endotracheal tube, anaesthesia was induced with propofol 2.5 mg kg−1 and rocuronium 0.6 mg kg−1 based on ideal body weight. A remifentanil infusion was begun at 0.45 μg kg−1 min−1 again based on ideal body weight. Volume-controlled mechanical ventilation was set at a respiratory rate of 12 breaths min−1 and a tidal volume of 10 mL kg−1 ideal body weight, with FiO2 of 0.5 and PEEP of 5 cmH2O. It was modified thereafter to maintain an end-tidal CO2 of 35-40 mmHg. Anaesthesia was maintained with desflurane and remifentanil. Desflurane was titrated on bispectral index (BIS) values whereas the remifentanil infusion was titrated against haemodynamic monitoring.
Neuromuscular transmission was monitored by the response to single twitch stimuli at 0.1 Hz, using acceloromyography of the adductor pollicis muscle (TOF-Watch; Organon Tecknica, BV, NL). The onset time of 0.6 mg kg−1 of rocuronium was 88 s and duration of action (recovery to 25% of control) was 27 min. Recovery was monitored by TOF stimulation. Additional doses of rocuronium were administered as requested, based on neuromuscular monitoring. BIS was maintained between 40 and 60 (BIS monitor Model A 2000; Aspect Medical System Inc., Newton, MA, USA). End-tidal fraction of desflurane varied during maintenance of anaesthesia, between 4.0% and 5.7%.
Non-invasive haemodynamic monitoring was performed by the HemoSonic (HemoSonic™ 100; Arrow International, Everett, MA, USA) transesophageal echo-Doppler. Remifentanil infusion varied between 0.11 and 0.51 μg kg−1 min−1 with considerable intraoperative haemodynamic stability: mean arterial pressure (MAP) 69 ± 5 mmHg, heart rate (HR) 84 ± 12 min−1, aortic blood flow 9.0-11.5 L min−1, stroke volume 84-156 mL beat−1, acceleration 15.1-20.6 m s−1 and total systemic vascular resistance 793-1106 dyns cm−5.
Repeated arterial blood gas sampling was performed to confirm adequacy of ventilation during anaesthesia, prior to and after extubation, as well as in the recovery room. The surgical procedure lasted 6 h. Approximately 30 min before stopping the infusion of remifentanil, ketorolac, 30 mg, was administered i.v. Surgical wound infiltration with bupivacaine 0.25% (40 mL) was performed. Reversal of neuromuscular blockade by neostigmine 0.05 mg kg−1 and atropine 0.02 mg kg−1 both based on ideal body weight was undertaken 15 min before extubation, the TOF ratio being 0.55. Extubation was safely performed 7.5 min after interrupting desflurane administration. BIS values rose rapidly from 42 before interrupting desflurane administration to 64 after 4 min and to 88.3 min later. 30 s thereafter, the value was 94 and the patient was extubated. Extubation was performed under fibreoptic vision with a TOF ratio of 0.9. Meperidine 30 mg was administered 15 min after extubation. The patient was transferred under strict monitoring to the recovery room with an arterial pressure of 140/80 and a SPO2 of 100 with a FiO2 of 0.5.
Postoperative pain was managed by an i.v. infusion of tramadol, 200 mg, and ketorolac, 60 mg, over 24 h. Recovery was uneventful and pain, graded by visual analogic scale, ranged between 0 and 2. Face mask oxygen therapy was continued overnight. No desaturation episodes (SPO2 < 90) were recorded overnight and no further analgesia was required. When questioned on days 2 and 8, the patient did not remember the fibreoptic awake intubation but only topical anaesthesia of the pharynx. Amnesia included extubation since the first memories dated to the recovery room. No complications were observed and the patient was discharged on the 8th postoperative day.
In the present case, we coupled the use of short acting agents such as desflurane, remifentanil and rocuronium with continuous intraoperative monitoring of their effects. Desflurane was titrated on BIS values, rocuronium was administered on the basis of twitch response and remifentanil infusion was adjusted on haemodynamic monitoring documented by transesophageal echo-Doppler and blood pressure.
Morbid obesity is responsible for several pharmacological changes including alterations in the distribution, binding and elimination of many drugs. Hence, the resulting pharmacodynamic effect is often unpredictable and uncertain, making drug titration even more difficult . Desflurane, owing to its low solubility, is rapidly released from tissues and eliminated at the end of prolonged anaesthesia. Consequently, morbidly obese patients experience a significantly faster immediate recovery when receiving desflurane-remifentanil anaesthesia compared to sevoflurane-remifentanil . Remifentanil's ester structure accounts for its rapid metabolism by blood and tissue esterases to inactive products independent of renal and hepatic function. Moreover, remifentanil pharmacokinetics are not appreciably different in the obese and therefore remifentanil dosing regimens should be based on ideal body weight . Muscle relaxants with weak or moderate lipophilicity such as rocuronium are distributed mainly in lean tissue. Accordingly, the dosage of rocuronium in obese patients should be based on ideal rather than on real body weight .
Recently Gaszynski and colleagues  reported a case of intraoperative management of a super obese patient (219 kg, BMI 70.7). Induction with remifentanil, midazolam and propofol, was followed by midazolam and a mixture of 66% nitrous oxide in oxygen for maintenance of anaesthesia. Cisatracurium was used to facilitate oral endotracheal intubation. We preferred rocuronium because of its shorter onset and duration of action in morbidly obese, awake fibreoptic intubation and a low-solubility hypnotic volatile agent such as desflurane for maintenance of anaesthesia . For intraoperative analgesia we utilized remifentanil at an infusion rate between 0.11 and 0.51 μg kg−1 min−1 in contrast with the range of 0.5-0.75 μg kg−1 min−1 reported by Gaszynski and colleagues .
In conclusion, we report the use of short acting drugs coupled with intraoperative monitoring of the effects of each agent. Such strategy resulted in considerable intraoperative stability and prompt recovery of respiratory function allowing rapid extubation in the operating theatre and uneventful recovery.
Department of Anaesthesia and Intensive Care, Santa Maria degli Angeli Hospital, Pordenone, Italy
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