Patient-controlled analgesia for morbidly obese patients: an effective modality if used correctly

Clinical Update on Patient-Controlled Analgesia for Acute Postoperative Pain

Patient-controlled analgesia (PCA) is an effective method for controlling acute pain, including postoperative pain in adults and in children from five years of age, pain resulting from labor, trauma, or other medical situations, or chronic and malignant pain. The treatment consists of a mini-computer-controlled infusion pump permitting the administration of on-demand, continuous, or combined doses of analgesic (mainly opioid) variations in response to therapy, which allows pain to be significantly controlled. Intravenous (IV)-PCA minimizes individual pharmacodynamics and pharmacokinetic differences and is widely accepted as a reference method for mild or severe postoperative pain. IV-PCA is the most studied route of PCA; other delivery methods have been extensively reported in the literature. In addition, IV-PCA usually voids the gap between pain sensation and analgesic administration, permitting better recovery and fewer side effects. The most commonly observed complications are nausea and vomiting, pruritus, respiratory depression, sedation, confusion and urinary retention. However, human factors such as pharmacy preparation and device programming can also be involved in the occurrence of these complications, while device failure is much less of an issue.

Best anaesthetic drug strategy for morbidly obese patients

PURPOSE OF REVIEW

The purpose of this review is to describe an evidence-based drug strategy applicable to any obese patient, rather than to present one standard 'ideal' anaesthetic drug combination. The ultimate choice of specific drugs in any given situation will depend upon clinician experience, patient specifics, and drug availability. The fundamental principle in anaesthesia for the obese patient is to use the shortest acting, least fat soluble agents to ensure rapid recovery to safe levels of alertness and mobility.

RECENT FINDINGS

No new drugs have been introduced over the past few years, but we have seen an introduction of enhanced recovery after surgery-based protocols into bariatric surgery. Our understanding of how obesity affects pharmacokinetics/dynamics of our drugs is improving, with new and better use of established drugs. Allometric scaling is being tested in the different pharmacokinetic/dynamic models used in target controlled infusion devices, with improved performance as a result. Obstructive sleep apnoea has a significant impact upon outcome and utilization of clinical resources, including critical care beds. If an improved drug dosing strategy will reduce this impact, then this would be a step forward.

SUMMARY

This review introduces newer findings to help us use anaesthetic and analgesic drugs more safely in the morbidly obese. However, there remain many areas of uncertainty with a lack of consensus on many issues.

Anesthesia considerations in the obese gravida

Obesity is associated with serious morbidity during pregnancy, and obese women also are at a high risk of developing complications during labor, leading to an increased risk for instrumental and Cesarean deliveries. The engagement of the obstetrical anesthetist in the management of this group of high-risk patients should be performed antenatally so that an appropriate management strategy can be planned in advance to prevent an adverse outcome. Good communication between all care providers is essential. The obese patient in labor should be encouraged to have a functioning epidural catheter placed early in labor. Apart from providing analgesia and alleviating physiological derangements during labor, the presence of a functioning epidural catheter can also be used to induce anesthesia quickly in the event of an emergency cesarean section, thus avoiding a general anesthesia, which has exceedingly high risks in the obese parturient. Successful management of the obese patient necessitates a comprehensive strategy that encompasses a multidisciplinary and holistic approach from all care-providers.

Morbidly obese parturient: Challenges for the anaesthesiologist, including managing the difficult airway in obstetrics. What is new?

The purpose of this article is to review the fundamental aspects of obesity, pregnancy and a combination of both. The scientific aim is to understand the physiological changes, pathological clinical presentations and application of technical skills and pharmacological knowledge on this unique clinical condition. The goal of this presentation is to define the difficult airway, highlight the main reasons for difficult or failed intubation and propose a practical approach to management Throughout the review, an important component is the necessity for team work between the anaesthesiologist and the obstetrician. Certain protocols are recommended to meet the anaesthetic challenges and finally concluding with “what is new?” in obstetric anaesthesia.

Cesarean delivery in the obese parturient: anesthetic considerations

Obesity is a worldwide health problem and its prevalence is reaching epidemic proportions. As obesity does not spare women of childbearing age, obstetric anesthesiologists will increasingly be exposed to the challenges of anesthesia in this population. The purpose of this article is to give the reader a thorough understanding of the anesthetic implications of obesity relating to cesarean deliveries. Obesity is associated with hypertension, diabetes, obstructive sleep apnea and other comorbidities. It increases the risk of cesarean delivery, postpartum wound infections and deep venous thromboembolism. Obese parturients are prone to anesthetic complications such as aspiration of gastric contents, difficult monitoring, positioning, airway management and challenging neuraxial techniques. A thorough precesarean delivery preparation should include an evaluation by an anesthesiologist for women with a BMI over 40 kg/m² and institution of an antacid prophylaxis protocol, thromboprophylaxis and antibiotic prophylaxis. Regional anesthesia should ideally be used in all obese parturients unless contraindicated. The goals of postpartum care include efficacious analgesia, physiotherapy and early mobilization. Monitoring and vigilance in an intensive care unit or step-down units should be considered for morbidly obese women.

Obesity and obstetric anaesthesia

The prevalence of obesity continues to increase despite preventive strategies. Obese parturients are at increased risk of having either concurrent medical problems or superimposed antenatal diseases such as pre-eclampsia and gestational diabetes. Moreover, they have a tendency to labour abnormally contributing to increased instrumental delivery and Caesarean section. Obesity is a risk factor for anaesthesia related maternal mortality. Morbidly obese women must be considered as high-risk and deserve an anaesthetic consultation during their antenatal care. The significant difficulty in administering epidural analgesia should not preclude their use in labour. A more liberalised use of regional techniques may be a means to further reduce anaesthesia-related maternal mortality in the obese population. The mother's life should not be jeopardised to save a compromised fetus. Prophylactic placement of an epidural catheter when not contraindicated in labouring morbidly obese women would potentially decrease anaesthetic and perinatal complications associated with attempts at emergency provision of regional or general anaesthesia. Early mobilisation, aggressive chest physiotherapy and adequate pain control are essential components of effective postoperative care.

Anaesthetic management of patients with sleep apnoea syndrome

PURPOSE

Sleep apnoea syndrome (SAS) is a relatively common, potentially fatal, disorder. Patients with SAS exhibit repetitive, often prolonged episodes of apnoea during sleep, with serious nocturnal and diurnal physiologic derangements. Several anecdotal reports and clinical studies have documented anaesthetic-related occurrence of fatal and near-fatal respiratory complications in these patients. The purpose of this article is to outline the potential problems encountered in anaesthetic management of adult SAS patients, and to suggest a practical approach for anaesthesia both for incidental and specific procedures.

PRINCIPAL FINDINGS

SASs have many implications for the anaesthetist. First, SAS patients are exquisitely sensitive to all central depressant drugs, with upper airway obstruction or respiratory arrest occurring even with minimal doses. Thus sedative and opioid premedication should be omitted as should the intra and postoperative use of opioids be limited or avoided. All anaesthetic drugs should be administered by titration to desired effect, preferably using short-acting drugs. When feasible, continuous regional anaesthesia using a catheter is the technique of choice. Where possible nonopioid analgesics or local anaesthetics should be used for postoperative analgesia. Perioperative monitoring for apnoea, desaturation, and dysrhythmias is essential. Secondly, SAS patients have a potentially difficult airway. Awake intubation is the safest approach to airway control. Extubation should only be tried in the fully conscious patient with intact upper airway function and under controlled situations. Thirdly, the cardiorespiratory complication of SAS and the presence of associated diseases can adversely influence anaesthetic management.

CONCLUSION

Perioperative risks attending SAS patients emphasize the importance of their detection, perioperative evaluation and planning.