Kanga cloths to smartphones: how should we measure blood loss in the operating room?
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Kanga cloths to smartphones: how should we measure blood loss in the operating room?
Ahmad Alli, MD • Gregory M. T. Hare, MD, PhD
Received: 30 September 2020 / Accepted: 18 October 2020 Ó Canadian Anesthesiologists’ Society 2020
Accurate assessment and treatment of acute surgical blood loss has been an important focus of anesthesiologists for many decades. As reviewed by Bonica and Lyter in 1951, ‘‘The amount of blood lost during surgical operations is usually more than that estimated by the surgical team. Unless an adequate amount is replaced, shock may ensue, and the postoperative morbidity is prolonged’’.1 In most adults, clinical signs of inadequate organ perfusion or shock present only when a significant amount of blood loss ([ 750 mL) has already occurred,2 and these signs can be masked in patients under anesthesia. Early detection of hemorrhage (occult or obvious), and the volume replacement for such hemorrhage, is considered one of the primary responsibilities of the anesthesiologist. Another important aspect to consider is that the numerical value of estimated blood loss (EBL) as charted on the anesthetic or surgical record is used widely for outcome prediction and research purposes. Nonstandardized or inaccurate measures of EBL therefore have the potential to cause bias in research and may in themselves result in adverse clinical outcomes due to unnecessary blood transfusion or lack thereof. Accurately quantifying blood loss in the operating room has been a problem from the very beginnings of modern anesthesia.1 As reviewed by Tran et al.,3 direct measurement, gravimetric assessment, and formula-based A. Alli, MD Department of Anesthesia, St. Michael’s Hospital, University of Toronto, Toronto, ON, Canada G. M. T. Hare, MD, PhD (&) Department of Anesthesia and Physiology, University of Toronto, St. Michael’s Hospital, 30 Bond Street, Toronto, ON M5B 1W8, Canada e-mail: [email protected]
assessments have been utilized. One of the earliest and easiest methods is visual estimation, by examining bloodsoaked sponges and suction canisters, which has been utilized to assess blood loss in obstetrics to minimize maternal morbidity and mortality.4 The main advantages of visual assessment are that it is readily accessible, rapid to perform, and cheap. This makes it particularly useful in resource-limited settings. In Tanzania, for example, Prata et al., reported the use of a locally made pre-cut piece of cloth, the kanga, to assess EBL after delivery in an obstetric out-of-hospital setting. Two blood-soaked kangas would prompt further management or referral.5 Similarly, in the operating room, soaked surgical sponges of certain sizes represent corresponding amounts of blood volume. Unfortunately, there is large heterogeneity in the methodology of studies analyzing this method, and this is reflected in the conflicting results of these studies. Visual assessment combined with direct measurement remains the recommendation of the American Society of Anesthesiologists.6 Empirically, the gravimetric a
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