This publication reflects on the perioperative and anesthetic experience two years after starting a bariatric program. Retrospectively, the patient’s medical charts and anesthesia records were analyzed with emphasis on the bariatric surgery and any follow up procedures. All the essential process times and metrics were collected to create insight into the effects of implementing a surgical bariatric program from an anesthesia standpoint.
Our main finding was that the bariatric patient population presents with its unique challenges. When managed appropriately in an interdisciplinary fashion, anesthesia can be delivered safely to this patient population. The preoperative evaluation of these patients should be conducted based on an individual’s need rather than relying on standardized test batteries.
Anesthesia for morbidly obese patients is generally regarded as being associated with increased risks [8, 14]. Accordingly, there are various contributions on the anesthetic and perioperative management in this patient group [4–7, 15]. They include the preoperative assessment, especially with regards to the airway management and monitoring strategies, the intra-operative phase, the emergence from anesthesia and the postoperative phase. Since bariatric surgery is being used in a more widespread manner, caring for morbidly obese patients is becoming more common for many institutions [3]. The surgical procedures are well illustrated by Ogunnaike et al. [6], e.g.
General
When dealing with the anesthetic considerations for bariatric surgery, it quickly becomes clear that it takes more than good surgeons and anesthetists to have a successful program. The patients need involvement of additional specialists such as Internal Medicine, Psychiatry, Physical Therapy etc. [3]. In addition, emphasis has to be put on the follow up care since a significant proportion of the patients will require additional surgical interventions. This affected 10% of our patients after gastric bypass surgery. Not included in this number were cosmetic follow-up operations such as abdominoplasty after the weight loss. Possible complications such as anastomotic leakage or internal hernia that require urgent care have to be considered when setting up the infrastructure.
Preoperative evaluation
Ideally, the extent of the preoperative diagnostics are tailored for each patient [7, 10, 15–17]. Heinrich et al. [10] reported, that approximately 20% of their patients received preoperative pulmonary function tests, which in return showed pathological values in over 90% of the cases. Such a streamlined approach is not always feasible, resulting in more generous recommendations for preoperative testing [4, 6]. Overall, the reported incidences of comorbidities such as hypertension or diabetes mellitus are lower than maybe expected [9, 12]. Great emphasis is generally put on the preoperative detection of an obstructive sleep apnoea syndrome, which mainly results in consequences for the postoperative phase, but also can influence the course before the surgery [7]. There seems to be a general consensus on the evaluation of the intubation anatomy, but no uniform approach exists [7, 18].
In our cohort, the vast majority of patients presented with an ASA physical status of 2. Arterial hypertension, diabetes mellitus and other overweight associated comorbidities were relatively often encountered. At the same time they barely ever influenced the perioperative approach. In collaboration with the Cardiology department of our hospital we have defined a pathway for the subset of patients that need to be seen by a cardiologist preoperatively. As a result we had only 40% of the performed echocardiograms and 25% of the stress tests with pathological findings. These results were instrumental to evaluate the general risk, determine the need for intraoperative monitoring, and to clarify the necessity of postoperative observation in the intensive care unit. No preoperative test results were so severe or unexpected that the surgical procedure had to be cancelled. Preoperative examinations such as gastroscopy or abdominal ultrasonography were used to plan the surgical procedure and did not affect the anesthetic approach.
Anesthetic
A key factor for the perioperative course of those patients was the duration of anesthesia, which in return consists mostly of the duration of surgery and the expertise of the surgeon [19]. Various authors report very different times for gastric bypass surgery; a median of 241 min for Leykin [12], 160 min for Heinrich et al. [10], 120 min in a review by Shang and Beck [15], and a quick 40 min for Jacobsen et al., and Bergland et al. in a dedicated center in Oslo, Norway [9, 11]. The group around Jacobsen [11] additionally showed that the duration of the emergence from anesthesia could be substantially reduced as a result from standardization of the surgical procedure that also produced reliable waypoints for the anesthetist. In our cohort, we note a wide distribution of the times for anesthesia induction and emergence. This fact should be given additional consideration when coordinating the operating room resources.
The intraoperative monitoring of patients undergoing GBP is very heterogeneous. In many institutions the insertion of an arterial cannula for blood pressure measurement is standard [5] or at least generously applied [7, 10, 15]. A similar approach to the liberal usage of central venous access seems also typical [10]. At the same time there are also data from large bariatric centers in which invasive monitoring is largely avoided [9]. In our series, the non-invasive blood pressure measurement was clinically judged to be reliable in 80% of patients. Also, in 94% of the cases, 2 adequate peripheral venous catheters were successfully inserted.
During induction of anesthesia the main focus was on the airway management. The importance of proper patient positioning and pre-oxygenation is well described [7]. Depending on the training background, the fiber-optic intubation in the awake patient has a high significance [4, 12]. When patients are intubated with conventional, direct laryngoscopy, they are reported to either have roughly the same [9, 18, 20] or slightly more difficult intubation condition than comparable cohorts [5, 10]. In our institution, the details of the airway management were at the discretion of the attending anesthesiologist. In one of our reference hospitals (Kantonsspital St. Gallen, Switzerland, http://www.kssg.ch), the fiber-optic intubation in the awake patient is strongly propagated for patients with a BMI >35 kg/m2 which partially explains the rather large share of almost 20% of our patients being intubated in such fashion. The conventional laryngoscopies resulted in 80% in complete visibility of the glottis (Cormack-Lehane grade I). In one patient the conventional intubation failed, highlighting the need to define an appropriate contingency plan. In all cases with conventional laryngoscopy we performed mask ventilation after the induction of anesthesia. In our rapid sequence protocol we set the inspiratory pressure to a maximum of 15 cm H2O and ventilated the patient’s lungs about 4 times per minute.
In most publications the anesthesia maintenance is described as being accomplished with volatile anesthetics or balanced anesthesia [10, 11], but Propofol-based anesthesia regimes are also mentioned [7, 12]. In our patients we almost exclusively used Propofol, which provided adequate hemodynamic stability and a rapid and uncomplicated emergence. Regarding our emergence times, it should be noted that in our setting the extubation took place in a dedicated area in the OR for the majority of cases. The rate of intraoperative complications is described to be around 5%, of those roughly a fifth can be regarded as anesthesia-related [14]. During the procedure the adequate oxygenation of the patient is of main concern [7]. Recruitment maneuvers and increased PEEP levels were described as effective, but are not of great sustainability [21]. Accordingly, it was deemed necessary to increase the PEEP level above the default setting of 5 cm H2O in 40% of our patients.
No blood products had to be administered intraoperatively in any case. Due to the relative difficulty to access the patients during the procedure we performed a type and screen on all of them, so we would have blood products readily available should the need arise. Because of the long duration of the procedure we put a clear emphasis on the temperature management and consequently only had two of our patients (1.4%) that had to be extubated delayed due to hypothermia. The emergence from anesthesia was generally unproblematic, mostly due to the appropriate planning and consistent avoidance of residual paralysis.
Postoperative care
The rate of postoperative ventilation requirement and the surveillance in either a 24-hour post anesthesia care unit or an intensive care unit varies considerably. Nishiyama et al. [5] for example report over 25% patients requiring postoperative ventilation in their case series, Leykin [12] had a rate of about 4%. Heinrich et al. [10] monitored over 50% of their gastric bypass patients for more than 24 hours in a dedicated intermediate care unit and had over 10% of the patients intubated during that period. On the other hand, Jacobsen et al. [11] reported that only 3 out of 2,000 patients required surveillance in the intensive care unit over a period of 5 years, whereas most patients only spent 2–4 h in the post anesthesia care unit. In our setting, which is devoid of a step down unit, a patient with untreated sleep apnoea syndrome was considered to be an indication for postoperative admission to the ICU, in accordance to the ASA guidelines for postoperative monitoring in OSA patients. This explains half (10% of all patients) of the ICU admissions. However, no interventions regarding to the OSA were necessary. The other 10% of the patients had varying reasons for their stay in the ICU.
Pain management can be particularly challenging in bariatric surgery patients. In our retrospective analysis it was not possible to evaluate standardized data for mobilization of patients or pain assessments. However, it should be mentioned that in no patient an intervention of our peri-operative pain service (e.g. regional anesthesia or iv patient controlled analgesia) was necessary.
In general, the anesthetic literature on bariatric surgery appears to be very heterogeneous. This is reflected in the volume of reported operations performed in each center, the characteristic process times and also in the anesthetic management. However, some recommendations found in the literature seem rather laborious and intricate.
The mid-term goals for our perioperative approach are aiming towards a more formalized fast-track bariatric surgery regime. This should be facilitated by a reduction in the surgical times and enhanced interdisciplinary collaboration with focus on the essentials [9, 11]. Additionally, the risk stratification of airway difficulties should be more standardized and the extent of preoperative testing re-considered. Providing muscle relaxation with rocuronium together with its specific reversal with sugammadex certainly has a potential place in this context [22]. The outcomes of the proposed strategies with respect to prophylaxis of PONV and pain management have to be followed in more detail. Another interesting detail to be investigated in the future is the possible difference in perioperative risk in patients being “just obese” compared to those being diagnosed as having metabolic syndrome [23, 24].
