Postoperative Pulmonary Complications: Understanding Patient Characteristics and Clinical Outcomes
Postoperative pulmonary complications (PPCs) are one of the most frequent and severe adverse events that occur in the hospital setting. The “Education Session II: Preventing Postoperative Pulmonary Complications: Are There Low-Hanging Fruits?” at the SOCCA 2021 Annual Meeting presented data from ongoing research to reveal factors leading to negative patient outcomes following hospitalizations. The findings have been published this past year with the hope that a better understanding of patient characteristics and clinical outcomes can provide a better approach to preventing PPCs in the future.
Shahzad Shaefi, MD, MPH, of Beth Israel Deaconess Medical Center, discussed hyperoxemia and its damaging effects during the perioperative phase. Oxygen is the most commonly administered drug used in hospital care, with 95% of patients receiving it in the ICU setting. In the last 5 years, many studies have been released indicating that its use is not as benign as once thought. Hyperoxemia can lead to mitochondrial damage, causing an inflammatory cascade, growth impairment and even cell death. Approximately 30% of patients with Acute Respiratory Distress Syndrome (ARDS) experienced episodes of hyperoxemia in the LUNG SAFE study. Unfortunately, despite multiple studies on the topic in past years, there’s no real consensus on definitions. A 2016 JAMA study of 400 ventilated ICU patients was ended early due to evidence pointing that increased oxygen use led to increased mortality. More recently, the ICU-ROX and HOT ICU trials showed no real difference between conservative- and liberal-use oxygen groups. The lack of good data and inadequate sample size of these studies make it hard to have a clear understanding of risk vs. benefit. Sicker patients may fare worse with higher oxygen supplementation. Based on analysis of recent data, it seems that a tighter control of oxygen therapy is good practice but more research is needed.
Karstan Bartels, MD, PhD, MBA, of the University of Nebraska, discussed research involving residual neuromuscular weakness following the administration of neuromuscular blockers. He stated that the evidence shows the use of blocking agents led to a qualitative decrease in grip strength postoperatively. This indicator can lead to a 10-fold increase in pharyngeal dysfunction and result in an aspiration pneumonia complication. The most common drug used as a neuromuscular blocking agent is Neostigmine, but the newer, more expensive agent sugammadex has fewer hypoxic effects and fewer PPCs. Since all neuromuscular blocking agents have adherent risks of PPCs, the recommendation is to use the least possible dosage. Additionally, there is the need for quantitative vs. qualitative testing to better understand the lasting effects of these medications.
Another presenter, Patrick Bender, MD, of the University of Vermont, discussed the effects of mechanical ventilation, positive end expiratory pressure (PEEP) and postoperative outcomes. He stressed that PEEP is not a “one size fits all.” Obesity and Trendelenburg position increase pleural pressure and increase the need for PEEP. The use of esophageal balloon manometer may help evaluate the PEEP requirements by measuring pleural pressure and allow for the personalization of mechanical ventilation, in return decreasing PPCs.
Lastly, Ashish Khanna, MD, FFCP, FCCM, from Wake Forest University School of Medicine, discussed the need for better monitoring and response during the postoperative recovery period. He stated that nearly half of all cardiopulmonary arrests and 85% of postoperative mortalities occur on the general care floors of the hospital. This is in part due to the lack of continuous monitoring used on these floors and the use of opioid pain management, leading to opioid-induced respiratory depression (OIRD). Comorbidities can also increase the risk of OIRD. Providing continuous monitoring is not the simple answer, since alarm fatigue and slow reaction times are also a factor. He discussed the 4 am phenomenon, which is the time of day when a code blue is most likely to happen. This correlates with the first episode of hypoxia occurring approximately 4 hours after leaving the PACU and the slow decline of the patient who is not on continuous monitoring through the night. He was optimistic that smart continuous monitoring may be coming and that the use of artificial intelligence could help.
There are many factors leading to PPCs in the hospital setting, and continued research is needed to get a better grasp on improved patient outcomes. Due to the overwhelming effects of the COVID-19 pandemic and the related hospitalizations over the past year, there will be more data coming in the near future to help us better understand the effects of mechanical ventilation, oxygenation and their relationship with PPCs.