The primary anesthetic was general anesthesia for 99% of the polio patients, with 1 patient undergoing monitored anesthesia care; while slightly more controls underwent a monitored anesthesia care (7%), and 1 patient had a neuraxial as their primary anesthetic, 93% of the controls had general anesthesia, which was not significantly different (P = 0.06). Duration of anesthesia was very similar (polio: mean 4.4 hours, SD = 2.0; controls: 4.5 hours, SD = 2.3). With regard to airway management, the 2 groups were again very similar with no significant differences noted. No difference was noted in difficulty of mask ventilation, type of laryngoscopy, airway device used, or difficulty of direct laryngoscopy (Table 2). Muscle relaxants were used in a similar proportion for each group (95% of polio patients and 91% of controls, P = 0.22), and the type of drugs used was very similar, with vecuronium the most common nondepolarizing muscle relaxant used (77% of polio patients and 75% of controls; Table 2). Among patients who received vecuronium as their only muscle relaxant, the doses used were similar between polio patients and controls (13.1 ± 5.7 vs 13.9 ± 6.5 for polio versus control; P = 0.387).
The postoperative course was very similar for both groups of patients. PACU admission, length of PACU stay, ICU admission, length of ICU stay, and initial extubation location were not significantly different between the 2 (Table 3). With regard to postoperative analgesia, slight differences were noted in modes of pain control. Control patients tended to be more likely to receive neuraxial anesthesia (14% compared with 8% of polio patients; P = 0.08), whereas peripheral nerve blockade was more common in polio patients (6% vs 0%; P = 0.001). Although not statistically significant, a lower percentage of polio patients compared with controls received opioids on POD1, and among those receiving opioids, the total dose received was significantly lower for polio patients versus controls (P = 0.025). On POD2, the percentage of patients receiving opioids was lower for polio versus control (P = 0.031), but the doses received were similar. Postoperative pain scores were very similar between the 2 groups. There was no significant difference in the maximum or average pain scores on POD1 and POD2 or in the number of patients who required pain service consultation (Table 3). There were no documented positioning injuries in either group of patients.
In looking at our primary outcome for any pulmonary complications, there was no significant difference between the 2 groups (17% vs 14% for polio versus control, respectively; conditional logistic regression odds ratio = 1.5; 95% confidence interval, 0.7–3.3; P = 0.33). Eleven percent of both groups required postoperative mechanical ventilation (P = 0.87), reintubation occurred in 4% of polio patients and 3% of controls (P = 0.66), pulmonary infections were noted in 7% of polio patients and 4% of controls (P = 0.26), and aspiration was documented in 2% of polio patients and 1% of controls (P = 0.49; Fig. 2). No difference was noted with those requiring a code or rapid response team intervention (4% vs 3% for polio versus control; P = 0.46). The 30-day mortality rate was also not significantly different, with 2% of polio patients dying, compared with 3% of controls (P = 0.79).
The analysis of the primary outcome was repeated for the subset of patients with a history of poliomyelitis who had persistent neurologic deficits preoperatively (n = 36) and their matched controls (n = 72). In this subset analysis, there were 4 (11%) polio patients and 8 (11%) control patients who experienced pulmonary complications (conditional logistic regression odds ratio = 1.00; 95% confidence interval, 0.27–3.72; P = 1.00). The percentage of patients experiencing specific pulmonary complications of interest was similar between groups (postoperative mechanical ventilation: 6% vs 8% for polio and control patients, respectively; prolonged mechanical ventilation: 0% vs 1%; reintubation: 8% vs 4%; pulmonary infection: 6% vs 6%; and aspiration: 0% vs 1%). The median pain scores on POD1 were also similar (2.2 ± 1.7 vs 2.2 ± 1.6 for polio and control patients, respectively), as was the percentage of patients receiving opioids on POD1 (69% vs 64%) and the median opioid dose in those receiving opioids (57.0 vs 58.5 mg).
The main finding of this study is that patients with a history of poliomyelitis do not seem to have an increased risk of pulmonary complications in the perioperative period. Although postoperative respiratory failure has been reported in a postpoliomyelitis patient,6 our study demonstrates that these patients do not have statistically significant rates of respiratory complications compared with matched controls. However, an odds ratio as great as 3.3-fold may be present. In addition, it shows that the immediate postoperative course of these patients is very similar to that of matched controls, with similar numbers of PACU admissions, PACU length of stay, and initial location of extubation. Although the overall percentage of polio patients admitted to an ICU postoperatively was higher, it was not significantly different and may represent heightened vigilance with these patients based on their history of poliomyelitis. This assertion is strengthened by the fact that the mean length of ICU stay was longer for the control population, and no other postoperative complication was found to be significantly higher in this group of polio patients. Furthermore, those requiring a code or rapid response team intervention postoperatively and the 30-day mortality rate were not significantly different.
Although chronic pain is commonly described in patients with a history of poliomyelitis, especially in patients with documented PPS,1,7,10 and preoperative opioid use was higher in the poliomyelitis group, our study did not find evidence of higher reported pain scores postoperatively or a need for increased amounts of opiates to control their pain. In fact, among those receiving opioids on POD1, the total opioid dose received was significantly lower for polio patients versus controls (P = 0.025). On POD2, the percentage of patients receiving opioids was lower for polio versus control (P = 0.031), but the doses received were similar. This study also shows that pain scores were similar for patients with and without a history of poliomyelitis undergoing similar operative procedures. No difference was found in the mean or maximum pain scores for POD1 and POD2. Although the use of nonsteroidal anti-inflammatory drug medications was significantly higher in the control group, it is unknown why this difference was present, and it does not appear to have influenced the amount of opiates used. If anything, it would indicate that the poliomyelitis group required fewer analgesic medications to achieve similar pain scores. The similarity in postoperative pain control is also evidenced by the lack of consults placed for our inpatient Pain Service in this study group.
In looking at the use of peripheral nerve blockade and neuraxial anesthesia, this study does shed some light on the use of these techniques in patients with a history of poliomyelitis. No evidence of sequelae from peripheral or neuraxial blockade was found in the polio patients in our study. Interestingly, 6 of our patients with a history of poliomyelitis received peripheral nerve blocks, whereas none of the controls did. This may represent a concerted effort by the anesthesiologist to avoid systemic opioids and decrease other anesthetics with concerns for postoperative sedation, or it may just represent a random sampling of patients that happened to capture no controls who received peripheral nerve blocks. In contrast, while it was not significantly different, there were many more control patients (14%) who received neuraxial anesthesia compared with the polio patients (8%; P = 0.08). This may represent a concern in performing neuraxial techniques in patients who have documented neurologic deficits or, again, it may just represent a random sampling of patients that happened to capture fewer polio patients who received neuraxial anesthesia for these procedures. As noted by Lambert et al.,7 the type of primary anesthetic used and the decision whether or not to use peripheral or neuraxial blockade must be made on an individual basis. The safety of peripheral nerve blockade and spinal anesthesia has been suggested in case reports,9,13 and a large case series showed no neurologic complications after neuraxial anesthesia in 79 patients with PPS.14
With regard to the use of nondepolarizing muscle relaxants, previous work by Gyermek8 analyzed the effects of d-tubocurarine, pancuronium, and gallamine in pediatric surgical patients with a previous history of poliomyelitis occurring 6 to 12 years before their surgical admission. He demonstrated that these pediatric patients with a history of poliomyelitis had significantly lower 50% effective dose (ED50) values for both d-tubocurarine and pancuronium compared with the controls, but recovery times were identical in the polio versus nonpolio groups. In our study, a number of different nondepolarizing muscle relaxants were used, but vecuronium was used most commonly (77% of polio patients and 75% of controls). Although we did not analyze specific recovery times, the vecuronium doses used were similar between polio patients and controls among patients who received vecuronium as their only muscle relaxant (13.1 ± 5.7 vs 13.9 ± 6.5 for polio versus control; P = 0.387). More studies are needed to specifically look at the response of poliomyelitis patients to modern nondepolarizing muscle relaxants, such as vecuronium and rocuronium, and in adult patient populations.
This study has several limitations, many of which are related to its design as a retrospective, matched cohort, single-center study. Although it is a valuable tool, passive medical record review for a diagnosis of polio has potential sources for error. When a history of polio is documented in a patient’s medical record, there is no control on the timing or accuracy of this diagnosis. This study relies on providers documenting this diagnosis accurately. While we were unable to assure the accuracy of this diagnosis, there was active review of each patient’s chart to ensure that this diagnosis had been established in the past and did not represent a false-positive identification. In addition, when using the Mayo Clinic Life Sciences System Data Discovery and Query Builder, we made sure to exclude reference to the polio vaccine to avoid identification of patients who had received the vaccine but did not actually have the disease. Another limitation of this study is the fact that some of the controls may have had polio in the past, without documentation in their medical record, or may have had subclinical infections that were never identified. While possible, each medical record of the controls was manually searched for a history of polio, and with the length of follow-up many of these patients have at our institution, missing this diagnosis in their record is unlikely.
Another potential weakness of our study is that the case population represented a somewhat milder burden of disease than expected. Few patients were severely affected by PPS. This may reflect a selection bias, wherein more severely affected patients may elect to avoid surgery.
When looking at postoperative respiratory complications as an outcome, our study does not control for every variable that could contribute to respiratory failure. With this in mind, we made every attempt to match our controls based on age, type of surgery, and type of primary anesthetic. As noted earlier, the comorbidities of these 2 populations correlated well and do not indicate any reason why one group or the other should be more prone to postoperative respiratory failure. This study is also limited by the demographics of the patient population, some of which are not documented (such as race). This group of patients may not be completely generalizable to the entire population, but it does represent a significant number of individuals diagnosed with polio and can be compared with many patient populations around the United States. With regard to the size and scope of our study, it is limited by the number of cases but, to our knowledge, this is the only matched cohort study looking at patients with a history of poliomyelitis. Nonetheless, given the limited number of patients with a history of poliomyelitis eligible for study, our study does not provide adequate statistical power to rule out potentially meaningful effects. Therefore, our study does not provide definitive evidence that patients with a history of poliomyelitis are not at increased risk for postoperative pulmonary complications.
This retrospective, matched cohort study suggests that patients with a history of poliomyelitis do not seem to have an increased risk of pulmonary complications in excess of those experienced by similar patients without a history of polio (i.e., upper limit of the odds ratio = 3.3).
Name: Luke W. Van Alstine, MD.
Contribution: This author helped conduct the study, analyze the data, and write the manuscript.
Attestation: Luke W. Van Alstine has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Paul W. Gunn, MD.
Contribution: This author helped design the study, conduct the study, and write the manuscript.
Attestation: Paul W. Gunn has seen the original study data and approved the final manuscript.
Name: Darrell R. Schroeder, MS.
Contribution: This author helped design the study, analyze the data, and write the manuscript.
Attestation: Darrell R. Schroeder has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Andrew C. Hanson, BS.
Contribution: This author helped analyze the data and write the manuscript.
Attestation: Andrew C. Hanson has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Eric J. Sorenson, MD.
Contribution: This author helped design the study and write the manuscript.
Attestation: Eric J. Sorenson approved the final manuscript.
Name: David P. Martin, MD, PhD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: David P. Martin has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.
This manuscript was handled by: Sorin J. Brull, MD, FCARCSI (Hon).
We thank and acknowledge Selma Harrison Calmes, MD (Chairman (retired), Department of Anesthesiology, Olive View-UCLA Medical Center, Sylmar, California and Clinical Professor of Anesthesiology (retired), Department of Anesthesiology, the David Geffen School of Medicine at UCLA, Los Angeles, California) for her support of our project.
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