Anaesthesiology Intensive Therapy, 2010,XLII,4; 197-200

Postoperative analgesia in a morbidly obese patient with chronic renal failure

*Andrzej Daszkiewicz1, Mariusz Wyleżoł1,2


1Hospital of Minimally-Invasive and Reconstructive Surgery in Bielsko-Biała


2Department of Surgery, Military Institute of Aviation Medicine in Warsaw

Background. The number of surgical interventions performed in obese patients has recently been increasing. Anaesthesia in a morbidly obese patient may be difficult, due to many pathophysiologic changes and co-morbidities, together with altered pharmacokinetics and pharmacodynamics of anaesthestic agents. We present a case of multimodal preventive analgesia in a bariatric patient with chronic renal failure.

Case report.
A 36-year-old, morbidly obese man (BMI 47.8 kg m-2) was scheduled for a laparoscopic adjustable gastric banding (LAGB). The anaesthetic risk was increased because of hypertension, chronic renal failure, steatohepatitis and obstructive sleep apnoea syndrome. 30 minutes before anaesthesia, the patient received 2 g iv paracetamol. After induction, he was given 8 mg dexamethasone and 100 mg tramadol. All port-sites were infiltrated with 0.5% bupivacaine and adrenaline, both before skin incision, and before wound closure. Since NSAIDs and opioids were contraindicated because of the patient’s co-morbidities, postoperative analgesia consisted of tramadol and paracetamol, given alternately, every 3 hours. The patient was discharged home 28 hours after surgery.

Discussion and conclusion. According to the Polish Postoperative Pain Management Recommendations 2008, the pain after LAGB is multifactorial and rated as category 2. The pre-emptive analgesia and postoperative regimen presented in this case can be recommended in similar cases.

The incidence of obesity has been increasing, so has the number of obese patients undergoing surgery. In many cases, anaesthetic management in morbidly obese patients (BMI >40 kg m-2) is difficult due to various obesity-related pathophysiological changes and co-morbidities. The risk of perioperative complications in such patients is high.

One of the relevant issues in this population of patients is the appropriate dosage of drugs, considering their pharmacokinetics and pharmacodynamics (which change in obesity cases). The recommended dosage provided in the informative drug leaflet refers to total body weight and is based on the assumption that pharmacokinetic processes are proportional to body weight. In many cases of obese patients too low doses are administered. Several methods of dosing regimen modifications have been suggested based on calculations on lean body mass, ideal body weight or corrected body mass. For the majority of agents used during anaesthesia, determinations of an initial (loading) and a maintaining dose are essential. The initial dose depends on the distribution volume whereas the maintaining dose on drug clearance. In obese patients, the distribution volume of a given drug is higher or unchanged and clearance – increased or unchanged. The factors affecting the drug concentration in blood are abundant and multi-directional in character; therefore, pharmacokinetic examinations are required to determine the optimal dosage of drugs in obese patients [1, 2].

The present report describes analgesic management after laparoscopic adjustable gastric banding in an obese patient with chronic renal failure. 

CASE REPORT

A 36-year-old morbidly obese patient (BMI 47.8 kg m-2, height 183 cm) was scheduled for laparoscopic adjustable gastric banding (LAGB). The co-morbidities significant for postoperative pain relief included: arterial hypertension, chronic renal failure, hepatic steatosis, and obstructive sleep apnoea syndrome.

The patient fulfilled the ASA III criteria. On the day preceding the surgery, in the afternoon, the patient received the hyperosmotic solution of phosphates to prepare the gastrointestinal tract. This caused exacerbation of chronic renal failure with increased concentration of creatinine and urea at normal serum levels of sodium, potassium and chlorine ions, unchanged values of haemotocrit and haemoglobin, and lack of clinical features of dehydration. The surgery was postponed. After nephrology consultation, pharmacotherapy was modified. However, the patient received the angiotensin-converting enzyme inhibitor, which might cause unfavourable interaction with analgesics.

The patient was operated on 3 months later at BMI 47.0 kg m-2. Before the procedure, he was administered sennosides with simultaneous intravenous infusion of crystalloids. Moreover, prophylactic antithrombotics and antibiotics were used. Thirty minutes before anaesthesia 2 g of iv paracetamol was administered.

After premedication with iv midazolam 2 mg and fentanyl 0.2 mg, the patient received propofol 200 mg and atracurium 50 mg. The endotracheal intubation was performed and artificial lung ventilation with the mixture of O2 and N2O (40:60) was started. The composition of respiratory gases and ventilation parameters were monitored. Intravenous dexamethasone 8 mg and tramadol 100 mg were administered. The anaesthesia was maintained with sevoflurane 1.2%-1.5% and supplementary doses of fentanyl and atracurium.

Before surgery, the skin and subcutaneous tissue at the incision site were infiltrated with 0.5% solution of bupivacaine with adrenaline 1:200 000. The pneumoperitoneum was created (CO2) with max pressure of 15 mm Hg (2 kPa). In the anti-Trendelenburg position, using laparoscopy, a subcardial retrogastric channel was formed and an adjustable band placed around the upper part of the stomach. The band was surrounded by the anterior gastric wall using four mattress sutures placed between, over and under the banded part of the stomach. The subcutaneous drain was brought out and connected with the port, which was placed suprafascially at the level of the lower part of the sternum. Before the placement of skin sutures port sites and trocar entry sites were re-infiltrated with 0.5% solution of bupivacaine with adrenaline 1:200.000. The procedure lasted 90 min.

About 10 min before the completion of anaesthesia, iv ondansetron 8 mg was administered. The residual neuromuscular blockage was reversed with neostigmine 1 mg. After extubation, the patient breathing efficiently was transferred to the recovery room.

The scheduled postoperative pain treatment in the surgical ward was based on iv paracetamol 1 mg every 6 h (since the administration of 2 g of the loading dose) and tramadol 100 mg every 6 h. Pain severity at rest and on coughing was assessed according to the numeric rating scale (NRS): on the day of surgery − every 4 h and on further days − every 6 h. When the analgesic effect was insufficient (NRS >3), iv ketamine 25 mg was considered.

In the evening after surgery, the patient was ambulated. He was discharged on the following day in the afternoon (28 h after surgery completion). During hospitalization, the severity of pain did not exceed NRS score 3; the patient did not require ketamine. The analgesic treatment prescribed on discharge included paracetamol syrup 1 g every 6 h and tramadol drops 25-50 mg orally every 6 h if need be.

DISCUSSION

Laparoscopic procedures are less invasive than laparotomies. Pain after laparoscopic procedures is less severe however, it may still be the major source of postoperative complaints.

Laparoscopic implantation of an adjustable gastric band is the procedure connected with slight tissue trauma (category II, NRS>4, pain up to 3 days) [3]. Postoperative pain is the sum of three various components: somatic, visceral and projected pain [4]. The somatic pain is conducted through by the spinal nerves and is mainly caused by skin and muscle incisions through which trocars are introduced and the area where the banding port has been suprafascially sewn up. The visceral pain in the gastric region is transmitted by visceral nerves leading sympathetic fibres to the spinal cord at the Th7-Th9 level and the vagus nerve leading the parasympathetic fibres. It may be induced by the discontinuance of tissues during the creation of retrogastric channel for banding and the band itself (mechanical irritation). This kind of pain may be accompanied by nausea. The projected pain has two sources. One of them, less common, is the pain in the back region at the level of lower scapula angles resulting from irritation o
f the gastric region earlier described. Another source of projected pain is the pain within the region of an arm or arms occurring after various laparoscopic procedures, which is induced by various irritating and injuring factors affecting the diaphragm during creation and maintenance of pneumoperitoneum. Stimuli from the diaphragm are conducted by diaphragmatic nerves from the cervical plexus (mainly C4 roots). This explains the presence of projected pain in arms [5, 6].

Effective analgesic management requires multimodal action – at various stages and on various mechanisms of nociception [7]. Modern pain management is not confined to postoperative pain relief but also prevents the development of hyperalgesia; due to hyperalgesia, postoperative pain is experienced long after the injured tissues have been healed and may lead to persistent postoperative pain. Hyperalgesia results from the development of peripheral and central sensitization. Sensitization may be inhibited or attenuated at various stages of nociception. The process of peripheral sensitization may be inhibited at the stage of transduction whereas central sensitization at conduction and modulation stages [8].

For adequate analgesic management, timing of drug administration is extremely important. Initially, high hopes were associated with the use of drugs before the surgical injury – pre-emptive analgesia. This method was to reduce central sensitization and prevent neuroplasticity phenomena; yet such effects were confirmed only in epidural continuous analgesia [9]. With time the method was modified and the drugs were used throughout the perioperative period – the supply started before surgical injury and continued through the intra- and postoperative period – preventive analgesia. The main objectives of this management were to alleviate pain after tissue injury, prevent central sensitization (at the spine level) and reduce the incidence of persistent postoperative pain [10]. In patients at a high risk of persistent postoperative pain, additional agents suppressing hyperalgesia should be considered – gabapentins, pregabalins or NMDA receptor antagonists – protective analgesia [11, 12].

In our case, preventive analgesia was used − paracetamol was administered before surgery. The use of a loading dose has been described in healthy individuals [13, 14] and recently also in obese patients [15].

When paracetamol is used in obese patients, high incidence of hepatic steatosis should be considered. The toxicity of paracetamol in therapeutic doses has not been demonstrated in patients with chronic liver diseases [16, 17].

The dosage of paracetamol in obese patients should be based on the ideal body weight [18]. The single dose for the patient described, depending on the method used to calculate the ideal body weight, ranged from 1.1 to 1.8 g. The minimum single toxic dose for paracetamol was defined as 7.5-10 g [19]. Paracetamol, in addition to relieving postoperative pain, inhibits central sensitization and reduces the development of hyperalgesia [20]. 

Another analgesic used in the postoperative period was tramadol. The first dose was administered after anaesthesia induction to use its intraoperative effects on the descending antinociceptive serotoninergic and noradrenergic system. The supply of tramadol in the initial period of anaesthesia reduces the risk of nausea and vomiting in the immediate postoperative period.

Dexamethasone used intravenously after induction of anaesthesia was applied mainly as an element of prevention of postoperative nausea and vomiting; in some studies, however, its beneficial analgesic effects were demonstrated [4]. In our case, due to chronic renal failure no non-steroidal anti-inflammatory drugs (NSAIDs) could have been used, more so that the patient received angiotensin-converting enzyme therapy. During surgery, the patient was placed in the anti-Trendelenburg position. Combined with elevated intra-abdominal pressure caused by pneumoperitoneum, this reduces the venous blood return and possibly the visceral flow (including the kidneys). Under such circumstances, the toxic effects of NSAIDs might increase.

Before the skin incision, local anaesthesia was used. This reduces peripheral sensitization, by inhibiting transduction and decreasing neurogenic inflammation at the injury site, and decreases central sensitization by inhibiting transmission of nociceptive stimuli to the spinal cord. Before the placement of sutures, the wound region was re-injected with a local anaesthetic to prolong its action over the early postoperative period.

During anaesthesia, fentanyl, N2O and sevoflurane were used. Fentanyl, binding the opioid receptors, inhibits the transduction of spinal and cerebral stimuli thus depressing the reflex reactions. Moreover, it may also activate pronociceptive systems and induce hyperalgesia, which is unfavourable.

Nitric oxide, the N-methyl-D-aspartate receptor antagonist, decreases central sensitization and hyperalgesia induced by fentanyl [21]. It was demonstrated that N2O might be used in bariatric surgery without the risk of worse operative conditions during laparoscopy [22].

In our patient, postoperative use of opioids was abandoned due to increased risk of respiratory depression (obesity and obstructive sleep apnoea syndrome); ketamine was planned as an additional analgesic [23]. However, its use was not required.

In morbidly obese patients with contraindications for non-steroidal anti-inflammatory drugs who underwent laparoscopic gastric banding, the use of infiltration anaesthesia of the wound and paracetamol as well as iv tramadol may be an effective method of postoperative pain management.

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address:

*Andrzej Daszkiewicz

Szpital Chirurgii Małoinwazyjnej i Rekonstrukcyjnej
w Bielsku-Białej
e-mail: andrzej.daszkiewicz@mp.pl

received: 05.03.2010
accepted: 03.05.2010