Anesthesia and other medicines administered during and after surgery can lead to medical complications. One notable complication is perioperative respiratory depression. Defined as a respiratory response to anesthetics, sedatives, and analgesics post-surgery, this condition is characterized by hypoventilation that leads to hypercapnia, hypoxemia, and, in extreme cases, mortality. Procedure-related factors, such as surgical site, difficulty/duration of the surgery, anesthetic technique, as well as patient characteristics can influence the risk of this complication. Given the complexity of causes, the chief approach to management is monitoring patients while correcting physiologic homeostasis (Aryad et al., 2019). However, there is significant variation in the identification and classification of respiratory complications. To combat this variation, ongoing developments are taking place in several management methods. These developments include predicting high risk for perioperative respiratory depression during the pre-operative stage, burgeoning novel algorithmic monitoring, and non-opioid treatment options.
There are several predictive risk scoring systems that aim to help clinicians anticipate and prepare for perioperative respiratory depression. One such system is the STOP-BANG questionnaire, which screens for the risk of obstructive sleep apnoea, which can impair respiratory management and lead to hypoxemia. Similarly, the Score for the Prediction of Postoperative Respiratory Complications (SPORC) system predicts the risk of reintubation, and the Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) considers age, preoperative oxygen saturation, respiratory infection, preoperative anemia, upper abdominal or intrathoracic surgical incision, duration of surgery, and emergency procedure to predict the risk of postoperative respiratory complications.
Given the multitude of potential causes, reliable predictions cannot be made regarding which postoperative patients will become hypoxemic, how severe the hypoxemia will be, or what pattern the oxygen desaturation will follow. For instance, a study utilizing the STOP-BANG score, which is a validated measure of obstructive sleep apnea risk (a leading indicator of respiratory challenges) found that the score was not associated with the degree of postoperative oxygen desaturation and was an insufficient measure of respiratory depression (Khanna et al., 2016). A similar study indicated the ARISCAT screening tool analyzed results of patients with existing risk, obscuring the impact of pre-existing risk factors on respiratory depression (Mazo et al., 2014). These studies suggest challenges in predicting the risk of perioperative respiratory depression.
Burgeoning research addresses these challenges. One developing treatment is continuous electronic cardiorespiratory monitoring, which improves early detection of respiratory compromise. Additionally, studies are assessing new monitoring systems that analyze a more comprehensive set of factors. For instance, the Integrated Pulmonary Index (IPI) algorithm considers oxygen saturation, pulmonary rehabilitation, and partial pressure end-tidal carbon dioxide levels to more accurately predict respiratory depression. Similarly, in a study validating the PRediction of Opioid-induced Respiratory Depression In Patients Monitored by capnoGraphY (PRODIGY) trial, researchers expanded parameters of vitals monitored (i.,e. HR, respiratory rate, ETCO2, and SpO2 via capnography and pulse oximetry), resulting in a promising assessment of respiratory depression risk (Khanna et al., 2016). Finally, there is an ongoing investigation of drugs that act through non-opioid receptor systems that can restore breathing and may also prevent opioid-induced respiratory depression without affecting analgesia. Drugs that act through non-opioid receptor systems (e.g., potassium channel blockers, ampakines, and 5-hydroxytryptamine [serotonin, 5HT] receptor agonists) have been shown to play a role in mitigating the risk of perioperative respiratory depression(Van der Schier et al., 2014).
Future research will continue to focus on the limitations of monitoring systems to bolster their efficacy, namely on expanding the respiratory depression risk factors measured. Additionally, clinicians hope to standardize the assessment of respiratory safety.
References
- Ayad, S., Khanna, A., Iqbal, S., Singla, N. Characterisation and monitoring of postoperative respiratory depression: current approaches and future considerations. Br J Anaesth. 2019 Sept. [QxMD MEDLINE Link].
- Khanna, AK, Sessler, D I, Sun, Z , Naylor, A J, You, J , Hesler, B D, Kurz, A, Devereaux, P J, Saager, L. Using the STOP-BANG questionnaire to predict hypoxaemia in patients recovering from noncardiac surgery: a prospective cohort analysis. Br J Anaesth. 2016 May. 116 (5):632-40. [QxMD MEDLINE Link].
- Mazo, V., Sabaté, S., Canet, J., Gallart, L., de Abreu, MG., Belda, J., et al. Prospective external validation of a predictive score for postoperative pulmonary complications. Anesthesiology. 2014 Aug. 121 (2):219-31. [QxMD MEDLINE Link].
- Van der Schier, R., Roozekrans, M., van Velzen, M., Dahan, A., & Niesters, M. (2014). Opioid-induced respiratory depression: reversal by non-opioid drugs. F1000prime reports 6, 79. [H1 Connect Link]