Acute hip fracture surgery anaesthetic technique and 30-day mortality in Sweden 2016 and 2017: A retrospective register study

Introduction

Hip fractures affect worldwide 1.6 million patients yearly and the incidence is rising, often elderly patients with comorbidities¹. There are annually approximately 17,500 patients with hip fracture in Sweden, the majority being females and elderly https://rikshoft.se/wp-content/uploads/2013/07/rikshoft_rapport2016.pdf. The search for safe and effective anaesthetic techniques for the management of the elderly patient with fracture is still on-going. There are several techniques possible, all with various benefits and potential negative effects. Neuraxial techniques (spinal and epidural) have the benefit of avoiding the need for airway management and only minor effects on cerebral function. However, blood pressure may drop, which is associated with spinal bupivacaine, and there are data showing a drop in blood pressure being a major risk factor². Neuraxial anaesthesia and oral anticoagulants is also a matter of discussion³. Delay surgery to await the anticoagulant elimination may not be optimal⁴. The most recent meta-analysis has not been able to show any clear benefit comparing neuraxial and general anaesthesia^5,6.

The aim of the present study was to assess the choice of main anaesthetic technique for acute hip fracture surgery in patients ≥50 years old and the impact of main anaesthetic technique on the 30-day mortality in Sweden. The primary outcome was the impact of anaesthetic technique, general vs. neuraxial, on 30-day mortality. Secondary outcomes were effects of age, sex, ASA class, fracture type and surgery within and after 24 hours on the 30-day mortality.

Methods

This was a retrospective register study. Ethical permission for the study was obtained from The Regional Ethical Review Board in Stockholm (Dnr: 2017/1915-31; approved 2017-11-08, Annika Sandström). Patient informed consent is not required for register studies in accordance with Swedish research regulations.

The Swedish Perioperative Register (SPOR) data for January 1^st 2016 and December 31^st 2017 was reviewed. A diagnosis of acute hip fracture (fracture on the femur as collum fracture (S72.0), pertrochanteric fracture (S72.10) and subtrochanteric fracture (S72.2)), age above 50 years, emergent surgery (within 14 days) and information about 30-day mortality was inclusion criteria for analysis.

The data-sheets retrieved from SPOR for the study analysis were based on the above inclusion criteria and SPOR had helped to categorise anaesthesia into three groups: neuraxial anaesthesia with and without sedation (NA); general anaesthesia (GA); and combined general and neuraxial anaesthesia (CA).

Results

A total of 13,649 patients were included in the analysis (Figure 1); 4,601 males and 9,048 females with a mean age of 82 ± 9.6 years. Patients’ demographics are presented in Table 1.

Figure 1. Study flow diagram displaying exclusions for the study cohort.

NA (spinal, epidural and combined spinal/epidural) was the most common anaesthetic technique used (82.5% of patients), GA was used in 16% and CA in 1.5% of patients. Mean age was similar between the anaesthetic techniques studied, the proportion of age class 75–84 years and >85 years was however higher among NA compared to GA (79 vs 75%; p<0.0001). Sex was evenly distributed: 64 and 67% of GA and NA were female patients, respectively. Collum type fracture was the dominating fracture 56 and 54% of GA and NA patients, respectively. ASA class 3 was the most common functional class with more than 50% of all patients. The proportion of ASA classes 3–5 was higher among GA compared to NA (73 vs 59%; p<0.001).

The 30-day mortality for the entire study cohort was 7.7%, with no significant difference between the three anaesthetic techniques studied (GA 7.8%, CA 7.4% and NA 7.7%; Table 1).

Most patients had surgery within 24 hours and there was no difference in delay to surgery between anaesthetic techniques (Table 2). Duration of anaesthesia, surgery or PACU stay was similar for GA and NA, but somewhat longer CA. There was no clear difference in registered blood loss except for the CA group of patients (Table 2).

The 30-day mortality was higher among males (10.6%) compared to females (6.2%) and increased for each age class; from 2% among 50–64 years old patients to 11.6% in patients above 85 years of age (see Table 3). There was also significant difference in 30-day mortality between fracture type and with increasing ASA class (Table 3). The odds ratio for mortality in relation to anaesthetic technique did not change when adjusted for age, sex, type of fracture and ASA class (Table 4). There was no difference in 30-day mortality between patients that had surgery within 24-hours or later; however the number of patients having surgery beyond 24-hours was small (Table 5). No differences were seen in duration of anaesthesia, surgery or PACU stay between patients that died compared to survived at day-30 (Table 5).

Discussion

We found NA being by far the most common anaesthetic technique used for acute hip surgery in patients above 50 years of age. However, anaesthetic technique did not impact the 30-day mortality in this retrospective register study in patients having surgery for acute hip fracture. The 30-day mortality increased with age and ASA class. The 30-day mortality was higher in males as compared to females and fracture type also impacted mortality (pertrochanteric fracture was associated to higher mortality).

Our results are in line with previous studies suggesting that anaesthetic technique per se does not have a major impact on mortality^2,3. Our overall mortality is also in line with the mortality described in a recent study from the US, including 107,317 hip fracture patients. That study found a 30-day mortality of 8.5%⁷. Our mortality rate is however somewhat higher than that described by Neuman et al. in study published in 2014 from New York⁸. This study was likewise unable to show any difference in 30-day mortality between general and regional anaesthesia. They did however find a 0.6 day shortened hospital stay in the spinal/epidural group of patients.

There are several limitations of this study. This is a retrospective register study, data derived from the relatively new Swedish perioperative register, SPOR-register⁹. Registers are dependent on input and data-management, and we are aware that a number of patients were excluded in the analysis of outcome due to missing information. It should also be acknowledged that there are numerous potential alternative anaesthetic techniques for hip fracture surgery. We merely sorted into three main techniques: neuraxial, general and combined anaesthesia. Peripheral blocks and light anaesthesia/sedation may indeed be an option^10,11. We have not considered this surgical technique in the present study.

The focus of our study was to assess the impact of anaesthetic technique on mortality among elderly, patient 50 years and older. Different age limits have been used. We limited our analysis to 50 years and older as pathophysiology reasonably is different; both fracture type/cause and patients’ general health/fragility. The groups were reasonably matched by means of age, fracture type and ASA score.There are without doubt also huge differences in the surgical trauma between merely a screw fixation and a joint prosthesis. We did not explicitly study the impact on anticoagulation, or patients having anticoagulation therapy. A recent paper from the US did not find major differences in complications or death when comparing cohorts of patient without and with anticoagulation therapy; patients having anticoagulation therapy more commonly received GA (84 vs 62%)¹². We did not sub-group the material further, e.g. cause of fracture and type of surgery. All patients with hip fractures having surgery regardless of cause was included. Combined technique was associated with longer perioperative times and more blood loss than GA and NA. This may be an effect due to combined spinal and epidural anaesthesia being chosen for more complex procedures; however, this is merely speculation. Tight haemodynamic control maintaining blood pressure and heart rate within minimal deviation from preoperative values have been suggested to have a major impact, and studies assessing its effect are being conducted¹³. Optimising haemodynamics by ultrasound monitoring may also facilitate the perioperative course¹⁴. Temperature control is also of importance¹⁵. We cannot comment on the anaesthetic protocol performed in the patients included in this study or be more explicit about what drugs were used, nor the handling of any deviation in vital signs. The available register-data does unfortunately not contain information on quality of postoperative care, the occurrence of delirium, postoperative pain and nausea in sufficient fashion for analysis. The postoperative course, mobilisation, ambulation, intake of food and drink and discharge from hospital should indeed be assessed in future studies. Active rehabilitation and physiotherapy is of huge importance¹⁶.

Age, comorbidities and increased ASA class are known risk factors for complications after hip fracture surgery^17,18. Nutritional status, malnourishment, as well as obesity, may also have an effect in increasing risk for complications¹⁹. We did not use the Nottingham score, and there is without doubt several patient factors that may have contributed to outcome. The International Fragility Fracture Network has recently provided extensive guidelines based on consensus²⁰. Still further studies are indeed warranted to improve the understanding on how to best care for elderly patients with acute hip fracture.

Conclusion

The study identifies that the majority of hip fracture surgery is performed under spinal anaesthesia in Sweden. Only around 16% of patients undergo general anaesthesia. This could introduce bias. However, the groups appear well matched and the sample size remains large enough for meaningful comparisons. Propensity matching would have increased the fidelity of comparisons but was not performed. The research adds to the current literature identifying that anaesthetic technique has minor impact on 30-day mortality.

Further studies are warranted determining the anaesthetic impact on morbidity, quality of recovery and mortality following high risk orthopaedic surgery.

Data availability

The data has been retrieved from the Swedish Perioperative Register (SPOR). This is a national database supported by The National Board of Health and Welfare, Swedish Society for Anaesthesia & Intensive Care and Swedish Association of Local Authorities and Regions and data is thus protected. The data can be retrieved by request from SPOR (http://www.spor.se/) following Ethical Review board approval via application (https://www.epn.se/en/start/).