Periodic abnormal fluctuations of blood pressure, heart rate and skin blood flow appearing in a resuscitated comatose patient

Vasomotion - what is currently thought?

This minireview discusses vasomotion, which is the oscillation in tone of blood vessels leading to flowmotion. We will briefly discuss the prevalence of vasomotion and its potential physiological and pathophysiological relevance. We will also discuss the models that have been suggested to explain how a coordinated oscillatory activity of the smooth muscle tone can occur and emphasize the role of the endothelium, the handling of intracellular Ca(2+) and the role of smooth muscle cell ion conductances. It is concluded that vasomotion is likely to enhance tissue dialysis, although this concept still requires more experimental verification, and that an understanding at the molecular level for the pathways leading to vasomotion is beginning to emerge.

Dynamics of skin blood flow in human sepsis

OBJECTIVE

The study was undertaken to determine if sepsis alters the pattern of vasomotion and reactive hyperaemia in the skin.

DESIGN

This was a prospective, observational study.

SETTING

The study was performed in the medical and surgical intensive care units of a tertiary referral hospital.

PATIENTS AND PARTICIPANTS

11 patients with sepsis (using Bone's criteria [1]), were compared with 19 patients recovering from coronary artery bypass grafting who were used as non-septic controls. Nineteen normal volunteers were also studied.

MEASUREMENTS AND RESULTS

Skin blood flow was measured on the forearm using laser Doppler flowmetry at rest and after 2 min arterial occlusion with a tourniquet. The resting blood signal was analyzed by calculating the mean skin blood flow, the power of the skin blood flow signal (variance) and the power spectrum. The rate of recovery after arterial occlusion was determined by calculating the peak increase in skin blood flow and the time constant of the decay of skin hyperaemia back to baseline flow. Patients with sepsis had a mean skin blood flow of 6.24 (3.48) ml min-1 per 100 g tissue compared with 4.35 (1.41) ml min-1 per 100 g tissue for the patients after coronary artery bypass grafting (p < 0.05). The septic patients also showed a marked increase in the fraction of total power in the 0.1-0.15 Hz frequency band (0.19 (0.17) versus 0.068 (0.033), p < 0.05), a decreased peak hyperaemic response (40 (23)% increase in flow above baseline after cuff release versus 147 (19)%) and a prolonged time constant for recovery from hyperaemia (22.8 (12.7) versus 11.7 (8.5) seconds, p < 0.05). These results imply an increased local rather than central control of skin blood flow.

CONCLUSION

The laser Doppler flowmeter allows local rather than global haemodynamics to be studied. Abnormalities of skin blood flow control are found in sepsis, and this technique may prove useful to monitor the effects of treatment, especially if the use of laser Doppler flowmetry can be extended to other organs at risk of damage during sepsis such as gastro-intestinal mucosa.

Effects of neural blockade and general anesthesia on the laser-Doppler skin blood flow waves recorded from the finger or toe

Effects of neural blockade and general anesthesia on the basic wave (BW) and the reflex wave (RW) among the laser-Doppler (L-D) skin blood flow waves recorded on the finger or toe were studied in 2 volunteers and 42 patients. The BW was continuous, rhythmic and independent of respiratory movements. The RW, which was induced by a deep inspiration or a snapping sound, was a transient marked reduction in blood flow. The BW was almost flattened and the RW was no longer induced at the finger under complete wrist block (n = 2), or under cervical or upper thoracic epidural anesthesia extended caudally over T7 (n = 2). On the other hand, the BW was still detected with reducing frequency and the RW could be provoked with one exception at the finger on the side with a sympathetic ganglion block at the C6 vertebral level (n = 14). The BW and RW at the toe were retained under lumbar subdural anesthesia (n = 6) as well. However, under the combination of lumbar subdural anesthesia and lower thoracic epidural anesthesia extending rostrally over T4 (n = 6), both the BW and the RW disappeared at the toe. In the course of deepening nitrous oxide/enflurane anesthesia (n = 10), the BW gradually reduced in frequency until it was almost flattened, and it became difficult to provoke the RW. L-D flowmetry of the finger or toe could be a useful clinical measure for detecting the presence or absence of sympathetic function controlling cutaneous vasomotion.

Fundamental patterns and characteristics of the laser-Doppler skin blood flow waves recorded from the finger or toe

Three different components, Basic Wave (BW), Cardiac Wave (CW) and Reflex Wave (RW), among the laser-Doppler (L-D) skin blood flow waves on the finger- or toe-tip, were studied in 32 healthy volunteers. The cycle of the rhythmic BW was 8.1 +/- 1.7.min-1 and was independent of respiratory movements. The BW was synchronous with the baseline fluctuation in the digit-photoplethysmogram. Power spectral analysis of rhythmic fluctuations in the simultaneously recorded R-R interval on ECG, systolic blood pressure, and L-D skin blood flow disclosed that the BW was correspondent with the Mayer wave, i.e., low frequency component. The cycle of the CW was consistent with the heart rate and was superimposed on the BW. The RW was a transient marked reduction in blood flow, which was induced by a deep inspiration or various sensory stimuli. A sympathetic skin response on the palm and a venoconstrictive response on the occluded arm were observed concomitantly with the RW. Good synchronization was observed in each component of the L-D skin flow waves between the fingers and toes. These findings suggest that the BW and the RW on the finger- or toe-tip are predominantly driven by tonic and reflex phasic activities of descending sympathetic outflows via the supraspinal center, respectively.

A low frequency, high amplitude rhythmic fluctuation of laser-Doppler skin blood flow after subarachnoid phenol block

A 51-year-old male with a huge chondrosarcoma received subarachnoid dorsal root blocks with 10% phenol in glycerine to treat severe pain along the left leg. The dermatomes below the Th9 lost all somatic sensation on the left side after the nerve blocks, but the patient was not completely relieved from the pain. Laser-Doppler flowmetry on the toe of the left foot disclosed an increased blood flow and an abnormal fluctuation of the cutaneous capillary blood flow, i.e. a high amplitude rhythmic (HAR) wave with 2.5 to 3 cycles.min-1. The low frequency HAR wave persisted for the subsequent 3 months until a tingling sensation returned to the left leg. It would seem that some travelling roots of the sympathetic nerve were preserved from the chemical neurolysis and the remaining efferent and afferent nerve fibers were responsible for the persisting low frequency HAR wave and pain in the left leg.

Evaluation of the central nervous function in resuscitated comatose patients by multilevel evoked potentials

Multilevel evoked potentials were examined in 17 patients who became comatose after cardiac arrest and resuscitation. In 4 patients, the P1 through N3 components of the somatosensory evoked cerebral potential (SECP) were present altogether within 100 ms after the ischemic insults. They all subsequently regained consciousness, though three of them developed intelligence and motor disturbances to some extent. In 11 patients who regained consciousness, or remained in a vegetative state, the evoked potentials which reflect brainstem functions, such as the auditory evoked brainstem potential, the R1 wave of the orbicularis oculi reflex and the slow positive wave of the somatosensory evoked brainstem potential, were recognized. The somatosensory evoked spinal potential and spinal monosynaptic reflex showed normal appearances in the state of vegetation and even after the determination of brain death. The measures of SECP could be useful in predicting restoration of consciousness.