Arterial Line Placement in Patients Undergoing Primary Total Knee Arthroplasty
Lila R. Baaklini MD, Sarah M. Weinstein BA, Eva E. Mörwald MD, Crispiana Cozowicz MD, Lazaros Poultsides MD PhD, Jashvant Poeran MD PhD, Nigel Sharrock MD, Ellen Soffin MD PhD, Stavros G. Memtsoudis MD PhD FCCP
Arterial lines are frequently utilized during total knee arthroplasties (TKA) in patient populations who are deemed to require increased vigilance and to allow for continuous perioperative hemodynamic monitoring. However, it remains unclear if such interventions are associated with improved outcomes. In this retrospective study, we investigated the association between the anesthesiologist’s decision to place an arterial line catheter prior to surgery and common cardiac and pulmonary complications.
Materials and Methods
Approval for this retrospective study was obtained from the Hospital for Special Surgery (HSS) Institutional Review Board. Patients who underwent unilateral primary TKA at HSS from 2005-2014 were identified across anesthesia, surgical, billing, and demographics datasets. The statistical software R version 3.3.1 was then utilized to merge these datasets.
The resulting dataset consisted of 22,179 patients. Patients were excluded whose primary anesthetic type was missing (n=901) and whose anesthetic occurred after their admission date (n=73). For the remaining 21,205 patients, complications and comorbidities were identified using ICD-9 codes. The presence of an arterial line was identified using anesthesia billing CPT codes.
A multivariable logistic regression model was used to compute the odds for cardiac or pulmonary complications. The following covariates were included in the regression model: presence of an arterial line, age (years), gender (male or female), type of anesthesia (general, spinal, epidural, or combined spinal epidural-CSE), and Quan-Deyo comorbidity index.1
Of the 21,205 patients in this cohort, 16,832 (79.38%) had an arterial line placed intraoperatively. Of those who had an arterial line placed, 1,760 (10.46%) experienced a cardiac or pulmonary complication. This rate was higher than observed among patients who did not have an arterial line placed (188 of 4,373 patients, or 4.3%; p < 0.0001).
Patients who had an arterial line placed were, on average, older and had a higher Quan-Deyo comorbidity index, compared to those who did not. There was no significant difference in the proportion of males and females between the groups (Table 1).
Controlling for the covariates, arterial line placement was associated with higher odds of suffering a cardiac or pulmonary complication compared to no placement (OR 1.85; CI 1.57-2.17). In addition, the adjusted odds for cardiac or pulmonary complications increased with older age, male gender, general anesthesia (compared to neuraxial anesthesia), and higher comorbidity index (Table 2).
An AUC of 0.7026 suggests effectiveness of the regression model.
In this cohort of unilateral primary TKA patients, arterial line placement was associated with higher odds of cardiac or pulmonary complications. While causal relationships cannot be established, this finding likely suggests that the indication bias underlying the anesthesiologist’s decision to place an arterial line is selecting for patients at higher complication risk. Although adjusted for comorbidity burden, one cannot determine to what extent the placement of invasive monitoring modulates complications. Therefore, further research is needed to determine if the ability to monitor blood pressure real time via an arterial line prevents complications by allowing early detection of hemodynamic instability.