Annals of the Royal College of Surgeons of England (1991) vol. 73, 283-284

Pulse oximetry in closed

limb

fractures

Huw G David

MB FRCS Orthopaedic Registrar

Department of Orthopaedic Surgery, Northwick Park Hospital, Harrow, Middlesex

Key words: Pulse oximetry; Limb fractures; Compartment syndromes

Recent sporadic reports have described the role pulse oximetry might play in monitoring trauma victims, and specifically in the assessment of patients with limb fractures where doubt exists concerning the adequacy of limb blood flow distal to the fracture after manipulation. The results of a prospective study to determine the changes in arterial oxygen saturation as shown by pulse oximetry before and after manipulation are presented. The results suggest that the pulse oximeter may be of use in confirming the presence or absence of adequate blood flow distal to a fracture, but that this information should be considered in the light of the clinical findings. The role of pulse oximetry in the early detection of a compartment syndrome complicating a closed limb fracture has yet to be determined.

Pulse oximetry, a popular addition to the armamentarium of anaesthetists in the monitoring of patients during operative procedures, has recently been recommended as an aid to the monitoring of trauma victims in general (1) and specifically in assessing limb perfusion after the manipulation of difficult closed limb fractures (2). In this latter article the authors report the case of a child with a supracondylar fracture of the humerus and clinical signs of impaired perfusion in whom the arterial oxygen saturation improved after manipulation as shown by a pulse oximeter, and advocate its use in such difficult cases. To date no study appears to have been performed to demonstrate what changes, if any, occur as shown by pulse oximetry in a series of closed limb fractures after manipulation. The results of such a prospective study are presented here.

Patients, method and results Patients with closed limb fractures requiring manipulation under general anaesthesia were entered into a Correspondence to: Huw G David FRCS, Department of Orthopaedics, Central Middlesex Hospital, Acton Lane, London NWIO 7NS

prospective study. The percentage arterial oxygen saturation as measured by a Critikon Oxyshuttle® pulse oximeter in the finger or toe of the injured limb distal to the fracture was measured immediately before and 3 minutes after the manipulation before plaster cast immobilisation. All manipulations were performed under inhalation anaesthesia within 6 h of injury. At the same time, control measurements were taken from the toe or finger of the uninjured contralateral limb in all patients. In each case the median percentage saturation figure over a 60 s period of assessment was recorded. A total of 40 patients with closed limb fractures requiring manipulation were entered into the study (23 males, 17 females; age range 6-88 years). The frequency of fractures sustained is shown in Table I. In addition there was one compound femoral shaft fracture (see below). In all but one patient with a closed limb fracture, the percentage arterial oxygen saturation as measured by the

Table I. Site and frequency of closed fractures Site

Number

Humerus

Midshaft Supracondylar Radius and ulna Proximal third Middle third Distal third Radius only Ulna only Femur Tibia ± Fibula Proximal third Middle third Distal third

* See text One compound fracture-see text

t

1 3* 2 4 14 2 2 ot

0 3 9

284

H G David

pulse oximeter distal to the fracture was in the range 92-100%, in both the uninjured and injured limb before and after manipulation. The percentage difference in oxygen saturation between the two limbs, before and after manipulation, was ± 3% or less. In one patient with a fracture of the midshaft of the humerus angulated through nearly 90°, the arterial oxygen saturation improved from 90% to 97% after manipulation, with a figure of 96% being recorded in the uninjured limb. A pulse distal to the fracture was undetectable in only two patients. In the first, an 8-year-old child with a supracondylar fracture of the humerus, the pulse oximetry value was identical to that obtained in the uninjured limb, with the return of a palpable pulse occurring within 48 h. In the second patient, with a compound fracture of the femur and entrapment of the superficial femoral artery, an oxygen saturation of zero and an undetectable pulse on initial assessment both returned to normal after resuscitation of the patient and freeing of the artery.

Discussion Pulse oximeters have become popular monitoring tools due to their ease of use, non-invasiveness, portability and applicability in cases where oxygen saturation may be threatened (3). Many units available provide a visual arterial waveform display in addition to a numerical reading of pulse rate and haemoglobin saturation. They are, however, only a measure of arterial oxygen saturation and not tissue oxygen saturation (4). They are dependent on the presence and subsequent detection of an arterial pulsation by the sensor, usually a lightemitting diode and photoelectric cell contained within a spring clip and applied to either a finger or toe. The role of the pulse oximeter in two cases where a pulse distal to a fracture could not be palpated have been described, and, while the pulse oximeter may be of use in such difficult cases, the information so provided should be interpreted in conjunction with, rather than at the expense of, the associated clinical findings. In the 39 patients in this study in whom a palpable pulse distal to the fracture was present both before and after manipulation, the arterial oxygen saturation was shown to be little altered by the presence of a closed limb

fracture when compared with the contralateral uninjured limb or after manipulation. As mentioned previously, the pulse oximeter is a measure of arterial and not tissue oxygen saturation. A moderate rise in tissue pressure, as may occur following a closed limb fracture, leads to a fall in the effective perfusion pressure (perfusion pressure minus tissue pressure) which in turn may lead to cessation of microcirculatory blood flow and acute tissue ischaemia (5). Although alteration in the arterial waveform with loss of the dicrotic notch, as shown by Doppler flow meter analysis, may occur, this is invariably a late feature, other abnormalities suggestive of increased tissue pressure and subsequent ischaemia such as subjective numbness, severe pain, hyperaesthesia and motor weakness becoming apparent at a much earlier stage (6). Indeed, the persistence of an arterial pulsation in the presence of a compartment syndrome is a frequent and clinically misleading sign as central arterial flow is rarely occluded (7). In conclusion, while the pulse oximeter may be of value in determining the presence or absence of a pulse distal to a fracture in doubtful cases, its role in the early non-invasive detection of a compartment syndrome complicating such an injury remains to be proved.

References I Silverston P. Pulse oximetry at the roadside: a study of pulse oximetry in immediate care. Br MedJ7 1989;298:711-13. 2 Best CJ, Woods KR. An aid to the treatment of supracondylar fracture of the humerus: brief report. 7 Bone 7oint Surg 1989;71B: 141. 3 Craft TM, Blogg CE. Letter, Br Med J 1989;298: 1096. 4 Moyle J. Letter, Br Med J 1989;298:1096. 5 Gardner AMN, Fox RH, Lawrence C, Bunker TD, Ling RSM, MacEachern AG. Reduction of post-traumatic swelling and compartment pressure by impulse compression of the foot. J Bone Joint Surg 1990;72B:810-15. 6 Matsen FA, Mayo KA, Krugmire RB, Sheridan GM, Kraft GH. A model compartment syndrome in man with particular reference to the quantification of nerve function. J Bone Joint Surg 1977;59A:648-53. 7 Mubarak SJ, Pedowitz RA, Hargens AR. Compartment syndromes. Current Orthopaedics. London: Churchill Livingstone, 1989:36-40.

Received 30 November 1990

Pulse oximetry in closed limb fractures.

Recent sporadic reports have described the role pulse oximetry might play in monitoring trauma victims, and specifically in the assessment of patients...
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