Routine postoperative blood tests in all patients undergoing Total Hip Arthroplasty as part of an enhanced recovery pathway: Are they necessary?

Abstract

Introduction

The increasing demand for Total Hip replacement (THR)/Total Hip Arthroplasty (THA) continues to place significant financial pressure on the National Health Service (NHS). Many institutions undertake post-operative blood tests routinely in this group of patients. The aim of this study was to identify if such routine blood tests (Full Blood Count (FBC) and Urea and Electrolytes(U&Es)) are required in all THR patients post-operatively.

Methods

Single institute, Multi-surgeon, retrospective observational study of consecutive patients who underwent primary elective THR done from Jan 2014 to Dec 2018.Post-operative blood tests and medical records were reviewed to identify derangement in haemoglobin (Hb) level and renal function requiring clinical intervention.

Results

Over the period of 4 years, 353 patients underwent elective THR with mean age of 70 years (range: 42–90). There were 203 Males and 150 Females. Mean pre-operative Hb was 134.7 g/l. Mean post-operative drop in Hb was 22.3 g/l. None of the patients in ASA grade 1 and 2 with age ≤70 years required blood transfusion post operatively.

6.4% of patients (n = 18/280) with an ASA of 1–2 had postoperative blood results requiring intervention of which only four (1.2%) were ≤70 years of age compared to 17.8% of patients (n = 14/73) with ASA 3–4.

Overall none of the patients in ASA grade 1 and 2 with age ≤70 years required blood transfusion post operatively nor had electrolyte disturbance. 1.2% had deranged renal function that needed minor clinical intervention.

Conclusion

Routine post-operative blood analyses may not required for all patients undergoing THA. Young and healthier patients seldom have significant abnormalities on routine post-operative blood analyses which requires clinical intervention.

Graphical abstract

1. Introduction

Total Hip Arthroplasty (THA) is a universally accepted, excellent intervention to improve function for degenerative hip disease. The demand for Total Hip Arthroplasty (THA) is expected to rise due to an increase in prevalence of osteoarthritis.1, 6 The post-operative recovery following a THA is reliable and predictable in most cases.² This has been further accelerated with advances in surgical and anesthetic techniques along with the introduction of multi-modal Enhanced Recovery After Surgery (ERAS) care pathways.^3,4 Traditionally, most institutions undertake routine post-operative blood tests, usually FBC and U&Es, in patients undergoing THA. The rationale for such investigations is to identify potential derangements in haemoglobin and renal function due to blood and fluid loss during the procedure and aids in further clinical management.(see Graph. 1 and Graph. 2)

Graph. 1.

Post-op Hb drop (g/l) vs patient’s ASA status.

Graph. 2.

Comparison of patients who had deranged U & E according to physical status ASA grade.

Current National Institute of Clinical Excellence (NICE) guidelines detail the pre-operative blood tests for elective surgical patients based on the nature of the procedure and patient’s physical status under the American Society of Anaesthesiologists (ASA).⁵ Despite this framework, no guidelines currently exist for routine post-operative blood investigation following elective arthroplasty procedures. It is the responsibility of the clinician to weigh the risks vs benefits of any invasive intervention to minimise potential harm to the patient and clinical personnel involved in their care. With increased financial constraints, we must also be able to justify the cost of any intervention.

We believe that, following an uneventful THA procedure in young and heathy patients routine post-operative blood tests are not required and that post-operative blood tests should be reserved for high-risk patients.

The aim of this study was to test this hypothesis and identify the prevalence of deranged haematological and renal function in patients following primary elective THA.

2. Methods

Single institute, multi-surgeon, retrospective observational study of consecutive patients who underwent primary elective THR over the period of four years. All patients who underwent elective primary unilateral THA procedures at our institution, between January 2014 to August 2018, were included. Data was obtained from theatre records and cross-referenced with National Joint Registry (NJR) records. Patients who underwent hip resurfacing, simultaneous bilateral THA procedures, and THA for intracapsular neck of femur were excluded.

Blood test results for all patients were obtained from our clinical portal system (Welsh Clinical Information Portal). The clinical records of those patients requiring either blood transfusion or electrolyte replacement were further analysed.

All patients underwent satisfactory pre-operative assessment and optimisation under supervision of a senior Consultant Anesthetist. A multi-modal perioperative care pathway was utilised for all patients. This included a standardised approach to blood preservation and hydration. Patients were admitted on the day of surgery and prescribed 150 mg of oral pregabalin 1 h prior to surgery, reduced to 75 mg for elderly patients (>70 years) or those with a low BMI (<25 kg/m2). All patients were allowed clear fluids up to Two hours prior to surgery. An opioid-free spinal anesthesia was preferred at the discretion of the anesthetist. Intravenous (IV) tranexamic acid (1 g) was given prior to skin incision, if not contra-indicated, followed by another dose of 1 g at the time of skin closure. Dexamethasone 8 mg, IV titrated 20 mmol magnesium sulphate infusion and 1 g of paracetamol (IV) were given intra-operatively.

All procedures were performed under direct supervision of a consultant arthroplasty surgeon. The surgeons used either posterior or direct anterior approach for THA according to their preference. Patients received either uncemented or hybrid (uncemented acetabular and cemented femoral components) components, again according to the surgeon’s preference. In order to facilitate early mobilization, peripheral nerve blocks were not routinely used. Peri-articular local anesthetic infiltration was used with a total volume of 150 ml consisting of a weight dependent dose of 0.25% bupivacaine with 1 ml of 1:200 000 adrenaline diluted in normal saline. Table 3

Table 3.

Demographics of patients who required blood transfusion. (HTN: Hypertension, Pulm: Pulmonary, CKD: Chronic Kidney Disease, HLD: Hypercholesteremia, DM: Diabetes Mellitus).

Age (years): Sex	ASA	Pre-op Hb (g/l)	Post-op Hb (g/l)	Hb drop (g/l)	Duration Of procedure (in Mins)	Co-Morbidities
83: Female	2	117	77	40	88	HTN, Pulm HTN
62: Female	3	128	70	58	126	CKD, HTN, Pulm HTN
81: Female	3	118	74	44	116	HLD, HTN, DM
87: Female	3	129	79	79	97	DM, HTN, MI

On return to the ward, all patients were encouraged to maintain adequate hydration by oral fluids in the post-operative period. Calf compression devices were used for mechanical thromboprophylaxis, if not contra-indicated, and all patients received LMWH (Enoxaparin) as chemical thromboprophylaxis, except in patients already on different anti-coagulant pre-operatively. Patients were encouraged for early mobilization as per ERAS protocol. All patients underwent post-operative blood analyses for FBC and U&Es as per department protocol on post-operative day 1. Blood analyses results from patients who required further intervention were recorded until they were discharged from the institution. Table 4.

Table 4.

The demographics of Patients in ASA 1 and 2 group with deranged U&E. (Cr: Creatinine, Ur: Urea, Na: Sodium, K: Potassium, IV: Intra-venous, MI: Myocardial Infarction, AF: Atrial Fibrillation, HTN: Hypertension, HLD: Hypercholesteremia, IHD: Ischaemic Heart Disease, DVT: Deep Vein Thrombosis, PE: Pulmonary Embolism, BCC: Basal cell carcinoma, TIA: Transient Ischemic attack, CA: Carcinoma, SJS: Steven Jhonson SyndromeDM: Diabetes Mellitus, CKD: Chronic Kidney Disease, PMR: Polymyalgia Rhuematica).

Age/sex	ASA	Derangements in Post op U&E’S	Intervention	Comorbidities
65/F	2	Cr: 135, Ur: 9.3	IV fluids	MI, AF
50/M	2	Cr: 117	IV fluids	HTN, HLD
66/F	2	Ur: 8.7	Oral/IV fluids	IHD
65/M	2	Cr: 129, Ur:8.8	Oral Fluids	DVT, PE, Gout
79/F	1	Ur: 9.1	IV fluids	Alzheimer’s Disease, BCC, HTN
77/F	2	Cr: 102	Oral Fluids	TIA, IHD
75/M	2	Cr: 114, Ur: 8.6	IV fluids	HTN, Alzheimer’s Disease, Cataract
59/F	2	Cr:112, Ur:9.2	IV fluids	Breast CA, HTN
71/F	2	K: 3.2	Oral K	HTN, Colon CA
71/M	2	K: 3.1	Oral K	IHD, Cataract
75/M	2	Na: 126	Fluid restriction	HTN, Colon CA
78/M	2	Cr: 122	IV fluids	SJS, Hypothyroidism
80/M	2	Cr: 111, Ur: 10.3	IV fluids	MI, HTN, Hypothyroidism
82/F	2	Na: 130	Fluid restriction	DM, HTN
84/F	2	Cr: 148, Ur:10.1, Na: 130	IV fluids	CKD, HTN, PMR
84/M	2	Cr: 142, Ur: 8.1	IV fluids	BCC, HTN, HLD
87/M	2	Cr: 141	Oral Fluids	AF, MI
90/M	2	Cr:119, Ur: 12.3	Oral Fluids	DVT, HTN

The absolute indication for post-operative blood transfusion was a haemoglobin (Hb) < 80 g/l. Transfusion in patients with ischaemic cardiac disease or subjective limitation of activity with physical therapy during post-operative rehabilitation was a multidisciplinary decision involving surgeons, nurses and physiotherapists.

The criteria of intervention following deranged U&E were, patients with altered post-operative urea and electrolyte value from baseline and clinically dehydrated and symptomatic leading to delay in rehabilitation and discharge.

Statistical analysis: Statistical analysis was performed with the software SPSS V 25. Frequencies or percentages were calculated for qualitative data and means ± standard deviations or medians (interquartile ranges) will be calculated for quantitative data. The Independent T-test and One-way ANOVA was used to examine differences between various parameter. Statistically significant differences are defined as those with a P value < 0.05.

3. Results

456 THA were performed between Jan 2014 to Aug 2018, out of which 353 patients met the inclusion criteria for this study. Mean age was 70 years (range: 42–90 years). There were 150 males and 203 females. Three hundred and one procedures were carried out via posterior approach and 52 were via direct anterior approach. The majority of patients underwent surgery for a primary diagnosis of osteoarthritis.

The majority of patients were ASA 1& 2 (n = 280/353, 79.3%). In this group, 42.7% (n = 150/280) patients were less than or equal to 70 years of age. The details of patients age and physical status according to ASA grade are demonstrated in Table 1.

Table 1.

Age and patient physical status according to ASA grade.

ASA Grade/Age	≤70 years	>70 years	Total
1	23	6	29
2	117	134	251
3	18	54	72
4	0	1	1
Total	158	195	353

Mean pre-operative and post-operative Hb were 134.8 g/l (range:168 g/l- 102 g/l) and 112 g/l (range:70 g/l- 156 g/l) respectively. Mean drop in Hb after the procedure was 22.3 g/l (range: 5 g/l - 58 g/l). There was no significant correlation found between Hb drop in relation to age, gender, approach and ASA status. Table 2 demonstrates correlation between various parameter and Hb drop in study population.

Table 2.

Hb drop correlation with Age, Approach, sex and ASA status.

	Mean Hb Drop g/l (Range)	P-value
Age		0.06 (Independent T-test)
=<70	23.46 (21.75–25.08)
>70	21.35 (20.06–22.62)
Sex		0.59 (Independent T-test)
Male	20.97 (19.40–22.69)
Female	22.27 (21.92–24.60)
Approach		0.39 (Independent T-test)
Anterior	21.60 (18.72–24.30)
Posterior	22.42 (21.27–23.64)
ASA Status		0.35 (One Way ANOVA)
1	22.38 (19.43–25.32)
2	22.60 (21.33–23.87)
3	21.26 (18.75–23.78)
4	17.00 (N = 1)

This study shows that routine post-operative blood tests are not required in patients under the age of 70 and who are ASA 1 or 2. No patients fulfilling these criteria required blood transfusion or had significant electrolyte abnormalities. Only 4 (1.2%) had mildly deranged renal function.

This is only the second study to date investigate the need for routine post-operative blood testing in THA patients undergoing surgery as part of an enhanced recovery pathway which includes blood preservation protocols. The strengths of this study are the fact full data sets were available for all eligible patients, all patients underwent surgery on the ERAS pathway and that our sample size is comparative to previous studies.

The rate of blood transfusion following THA has reduced significantly with the introduction of multi-modal blood preservation protocols. Such protocols typically start with the pre-operative identification and correction of anaemia. Peri-operatively pharmacological treatments with anti-thrombolytic agents (e.g. tranexamic acid), and non-pharmacological methods such as normovolemic haemodilution, hypotensive anesthesia, bipolar sealants, and cell salvage have all been employed. Postoperatively, the use of autologous transfusion and abstention from using surgical drains have also been shown to decrease the need for transfusion.⁹

Greco et al.⁹ retrospectively reviewed the need for routine post-operative blood results in 1023 patients undergoing total joint arthroplasty with a blood conservation protocol. In this study 401 patients underwent THA via either an anterior or direct lateral approach. They observed a transfusion rate of 2.5% in their THA group. They concluded “postoperative full blood counts and basic metabolic panels should not routinely be ordered in these patients unless their preoperative haemoglobin and potassium is below 130 g/dl or 4 mmol/l respectively, and they have medical comorbidities”.

Kildow et al.⁷ retrospectively reviewed 352 patients who underwent primary THA between Jan 2012 and Sep 2014. The incidence of transfusion was 15.3%(54/352) in patients not receiving TXA and 5.6%(17/352) in those given TXA. They concluded that routine post-operative full blood count was only required in those patients with pre-op anaemia or those not given TXA intraoperatively.

Halawi et al.¹⁰ investigated transfusion rates and AKI in 351 patients who underwent primary THA over a two-year period. The observed rates of AKI and blood transfusion were 2.0% and 2.3% respectively. Factors associated with blood transfusion were higher ASA class and intraoperative blood loss >250 mL combined with either preoperative anaemia or lack of tranexamic acid use. They concluded routine postoperative laboratory testing is not necessary in modern-day primary, unilateral THA, recommending instead that the decision to obtain laboratory tests should be driven by individual patients’ risk factors. Closer analysis of their data reveals that those patients requiring blood transfusion and those who developed post-operative AKI were all ASA class 3. This supports our own observations. Four patients in our cohort who were <70 years old had minor, transient electrolyte derangement which did not require any aggressive intervention and could have been treated with only encouraging oral fluids.

Our transfusion rate of 1.1% is like that observed by Greco et al., and Halawi et al. but lower that reported by Kildow et al. There results highlight the importance of the routine use of blood preservation protocols as part of an enhanced recovery pathway.

The risk factors for blood transfusion following THA have been well documented.^8,9 Increasing age, female sex, pre-operative anaemia, BMI, ASA grade >2, operative time and intra-operative blood loss have all been reported as independent risk factors. Whilst our results are consistent with the majority of these, we did not explore the relationships between intra-operative time and blood loss on transfusion.

The risk factors for post-operative electrolyte derangements like hypo or hyperkalaemia, hypo or hypernatremia are perhaps less clearly understood. Routine medications such as thiazides, angiotensin converting enzyme inhibitors, selective serotonin reuptake inhibitors, and conditions such as syndrome of inappropriate antidiuretic hormone secretion, Chronic kidney disease, Diabetes Mellitus etc. may all predispose patients to hyponatraemia and hypokalaemia. However, by reducing prolonged starvation and encouraging oral fluid intake peri-operatively, enhanced recovery pathways may help minimise electrolyte disturbances and the risk of AKI.⁹

Kidlow et al.⁸ investigated the role of Basal Metabolic Panel tests in patients undergoing primary TJA. They observed that in patients with normal preoperative values, without major medical comorbidities, these tests do not contribute actionable information. Using ASA as a surrogate marker of medical comorbidities we observed similar results but only in those patients under 70 years of age.

There are certain group of patients who may require a different approach. Patients with inflammatory arthritis or haemoglobinopathies, like sickle cell disease or thalassemia variants, will require close monitoring regardless of age and ASA status. These patients may have an altered physiological response to blood loss and surgical trauma and are often on complex medications like steroids and novel biologics which require careful monitoring. There were no patients in our cohort with haemoglobinopathies. None of the patients in our cohort with abnormal post-operative findings had inflammatory arthritis but we recommend extreme caution with these patients. The other subset is elderly patients with good general health i.e: >70 years of age with ASA 1or 2. We recommend strict post-operative monitoring based on results from our cohort.

The retrospective nature of our study is its main limitation; however, this is comparable to the other previously reported studies. Also, no detailed analysis of intraoperative blood loss, complications, duration of surgery and post-operative events was taken into consideration in those patients requiring post op intervention. Hence, the management of deranged/abnormal post-operative blood results in all patients with ASA 1 and 2¹³ is the product of a multidisciplinary discussion between the surgeon, general medical consultant, and physiotherapist. Similarly, in our institution decision of medical intervention is not based solely on an absolute haemoglobin level and blood results threshold but also incorporates factors from the medical history, specifically cardiac disease and chronic renal disease, as well as the patient’s postoperative activity level and ability to participate in physiotherapy. The other drawback is the lack of clearly defined transfusion protocols for those relative indication for transfusion, though this is fairly common in clinical practice. A multicentre pragmatic trial would be really helpful in looking into safety and cost effectiveness in post-operative blood analysis in low-risk patients undergoing elective THA with ERAS protocol.

The Department of Health for England statistics had shown that, over 230 million biochemistry and 47 million haematology investigations were requested in year 2014–15 at an estimated cost of over £415 m in secondary health care, with some estimates of up to £3bn for the National Health Service (NHS).¹² As the demand for primary arthroplasty continues to rise, the reduction in unnecessary blood tests post-operatively has the potential for significant cost savings for healthcare services. In our institution, FBC and Urea and Electrolyte blood test costs £20. In our cohort of 140 patients with age <70 years and ASA 1 and 2 status this would result in a potential cost saving of £2800 over the period of the study. In high volume centres this analysis might prove to be more cost effective in long run.

In conclusion, this study provides further evidence that with the introduction of ERAS protocol, routine post-operative blood tests can be avoided for many of the Elective patients undergoing THA and we propose the following Algorithm(see algorithm). Low risk patients (ASA 1 and 2) and age less than 70 have lower possibilities of finding significant derangements in post-operative bloods but intra-operative factors like blood loss, duration of surgery etc and post-operative course should be taken into consideration before deciding to perform post op blood analysis.

Declaration

• •This Audit is done as retrospective data analysis and departmental audit presentation; hence no approval is required from research and ethical committee. No funding is received from any source for conducting this audit.
• •All methods were carried out in accordance with relevant guidelines and regulations.
• •All experimental protocols of the study were approved by a named institutional and/or licensing committee.
• •Informed consent was waived by the IRB/ethics committee (Clinical audit and effectiveness department.

Funding

There is no funding source.

Ethical approval

This article was written with retrospective audit hence no ethical committee approval was required.

Declaration of competing interest

The authors declare that they have no conflict of interest.