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Titel på arbejdet The Perioperative Blood Loss and Complications in Lower Extremity Amputations. The results of four observational cohort studies.
Navn Christian Wied
Årstal 2017
Afdeling / Sted Ortopædkirurgisk afdeling, Hvidovre Hospital
Universitet København
  • Traumatology
Abstract / Summary

Background Many questions remain unanswered about the multifactorial complications that commonly lead to high morbidity and mortality among the lower extremity amputation (LEA) population. The morbidity and mortality warrants a continuous effort in perioperative optimisation and multidisciplinary regimes. Numerous factors influence the magnitude of the complications. An underestimation of the blood loss can influence negatively on outcome in these often frail patients, with very limited physiological reserves. The tourniquet is known to reduce the intraoperative blood loss. However, the scepticism towards the usage during amputation is attached to the potential damage to the vessels, which could lead to an increased risk of early failure. Silber et al. developed the concept of “Failure to Rescue” (FTR) which is a quality marker, attempting to measure a hospital’s ability to manage complications, while being less likely to confuse worse severity of illness with worse quality of care. It is becoming increasingly popular as an indicator showing how well hospitals perform once the complications occur. This seems reasonable since the mortality is related to the degree of illness and comorbidity of patients receiving treatment and not necessarily the expression of differences in the quality of care. The FTR rate is calculated as (patients with 30-days mortality/all patients with a severe postoperative complication). Since the mortality remains high, an easily applied risk stratification tool for individualising postoperative monitoring and care seems necessary. In 2007, Gawande et al. developed the Surgical Apgar Score (SAS) and the score has discriminatory power in vascular and general surgery. It remains unclear if the score has value in LEA surgery. To our knowledge, no recent scientific papers have aimed directly at describing the total blood loss (TBL), the FTR rate or the use of SAS in relation to LEA surgery. Purpose

As an overall aim of the thesis, we seek to provide new insights in the overall discussion of the perioperative blood loss and complications in patients with primary dysvascular LEA. We expect the thesis to generate hypotheses for new avenues of research.

Methods Study I assess the total blood loss in transfemoral amputations (TFA) and the possible triggers for an increased blood loss. The approach with Nadler’s calculation on the fourth postoperative day gives a rough estimate of the total blood loss from time of surgery until day four postoperatively. Study II on transtibial amputations (TTA) highlights the possible effect of tourniquet usage and aims to investigate if a possible increased total blood loss is present due to the risk of vessel damage when the tourniquet is inflated. Study III focuses on the perioperative mortality and the potential causes. The study includes an evaluation of the patient’s state prior to surgery and the calculation of the FTR rate. Study IV assess the discriminatory power of the SAS in lower extremity amputation surgery. All studies are retrospective cohort studies. Results In study I, the total blood loss was found to be roughly twice the intraoperative blood loss (OBL). Renal disease seemed to have a negative influence on the blood loss. The median TBL was 964ml (IQR: 407-1521) and the OBL was 400ml (IQR: 250-550). In study II, the patients operated using tourniquets received approximately three millilitres less transfusion blood per kilogramme of body weight than the patients operated on without using a tourniquet. The duration of surgery was shorter, and the OBL was less. The use of a tourniquet showed no statistically significant association with a 30day re-amputation at the femur level. Study III showed how 31 patients (16%) died in hospital, within a median of six (IQR: 4.5– 10) post-amputation days. Four (13%) deaths were classified as “definitely unavoidable”, four (13%) as “probably unavoidable”, and 23 (74%) as “Failure to Rescue”. Of the FTR deaths, 20 (87%) had active lifesaving care curtailed. The FTR rate was calculated to 30%. Patients who died were more frequently diagnosed with diabetes type II and either postoperative sepsis or pneumonia, compared with those who survived. With study IV, we found a significant linear association between a low SAS and postoperative complications. This effect was pronounced for transfemoral amputees where a significant increase was observed for the high-risk group compared to the low

risk group. This indicates moderate discriminatory power of the SAS in predicting postoperative complications among transfemoral amputated patients. Conclusion Based on the presented results of the thesis it seems reasonable to conclude the following: The TBL calculated on day four after TFA is roughly twice the amount reported just after the surgical procedure. Patients suffering from renal disease before amputation are more likely to have an increase in blood loss. The TBL did not significantly influence perioperative morbidity or mortality. Neither did a transfusions amount > 2 units between the preoperative haemoglobin and the haemoglobin on the fourth postoperative day. Therefore, a high anaemia vigilance seems recommendable when planning for TFA. Anaemic patients who receive a significant number of pre & post-operative blood transfusions, diabetic patients and patients with either postoperative sepsis or pneumonia seem to be subgroups with an apparent need of more perioperative-intensified care. From a haemodynamic viewpoint, it appears to be safe and advantageous to use a tourniquet during (ad modum Persson) TTA. The tourniquet reduces the duration of surgery, the blood transfusion rate and the OBL. The mortality of LEA patients is high and a large amount of patients is classified as FTR. Many of whom with active lifesaving care curtailed at some point prior to death. The SAS approach provides staff with information regarding the potential postoperative course after TFA surgery. This is pronounced when the patients are differentiated into a high- and low-risk group. The scoring system could prove useful in guiding preventive strategies, such as optimising intraoperative blood pressure or heart rate.

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