Blood contact and exposure in the operating room.

We prospectively studied 684 operations from all surgical specialties to describe the frequency and character of blood contact and exposure during the procedures. Blood contact was defined as percutaneous, mucous membrane, nonintact skin or intact skin contact of patient blood with any member of the operative team. Blood exposure was defined as contact in any of the preceding categories excluding intact skin. Over-all, 28 per cent of the patients had one or more blood contact events that involved 293 operating room personnel. Risk of blood contact was significantly greater for cardiothoracic (p less than 0.001), trauma (p less than 0.003) and obstetric cesarean section (p less than 0.021) procedures when compared with all other procedures. Three services (Ophthalmology, Transplant and Oral Surgery) had no contact events. The remaining nine had rates ranging from 17 to 33 per cent. Eight per cent of the procedures (n = 54) resulted in blood exposure to 63 individuals. Percutaneous exposure occurred in 3 per cent of all procedures. Blood contact events increased with increasing operative time. Blood contact most commonly occurred among circulating nurses (n = 79), anesthesia personnel (n = 65), surgeons (n = 59) and first assistants (n = 49). Despite increased concerns over the risk of occupationally acquired viral diseases, blood contact and exposure continue to be frequent events. Surgeons must assume that all patients are potentially infected and should adopt universally applied standards of behavior to minimize contact with blood.

Blood-borne factors regulating microvascular constriction in the rat hippocampal slice.

Previous work shows that blood serum contains a factor that elicits constriction of large cerebral arteries and may be responsible for cerebral vasospasm in subarachnoid hemorrhage patients. However, few studies have considered the action of potential spasmogens on intraparenchymal resistance vessels. We used a common preparation for neurophysiology, the rat hippocampal slice, to study penetrating arterioles and their response to a variety of potential vasoconstrictors. Dilute serum from clotted rat blood evoked profound microvascular constriction when applied to the slice, but plasma incubated with heparin to prevent coagulation was unable to do so. A variety of potential vasoconstrictor substances were tested to see if they could duplicate the effects of serum. Norepinephrine (10 microM), serotonin (one microM) and prostaglandin E2 (one nM) were ineffective in this regard. However, when a stable eicosanoid, thromboxane B2, was applied at a concentration achieved in the cerebrospinal fluid of subarachnoid hemorrhage patients, it duplicated a portion of the vasoconstriction produced by serum. It is concluded that thromboxane B2 may account for part of the spasmogenic property of serum and that unidentified molecules in the coagulation pathway may also play a role.

Vasoconstriction and neural excitation in response to transient hypoxia in the rat hippocampal slice.

The vascular and neural responses to transient hypoxia in the rat hippocampal slice were studied. Neural hyperexcitability produced by tissue hypoxia was associated with localized decreases in the diameter of precapillary arterioles. Vasoconstriction occurred periodically along the length of vessels observed. The mean percent decrease in vessel diameter in these narrowed regions was 10.25%. Population spikes recorded in the cell body layer of the dentate gyrus showed a mean increase in amplitude of 71.3%. The mean latency to peak response was similar for both the vessels and neurons. The results suggest mechanisms by which autoregulatory influences on microvessel caliber may be counteracted in conditions of hypoxia and hypotension in the whole animal.