Volume‐targeted therapy of increased intracranial pressure: the Lund concept unifies surgical and non‐surgical treatments

Abstract

Opinions differ widely on the various treatment protocols for sustained increase in intracranial pressure (ICP). This review focuses on the physiological volume regulation of the intracranial compartments. Based on these mechanisms we describe a protocol called 'volume-targeted' ('Lund concept') for treatment of increased ICP. The driving force for transcapillary fluid exchange is determined by the balance between effective transcapillary hydrostatic and osmotic pressures. Fluid exchange across the intact blood-brain barrier (BBB) is counteracted by the low permeability to crystalloids (mainly Na+ and Cl-) combined with the high osmotic pressure (5500 mmHg) on both sides of the BBB. This contrasts to most other capillary regions where the osmotic pressure is mainly derived from the plasma proteins (approximately 25 mmHg). Accordingly, the level of the cerebral perfusion pressure (CPP) is of less importance under physiological conditions. In addition cerebral intracapillary hydrostatic pressure (and cerebral blood flow) is physiologically tightly autoregulated, and variations in systemic blood pressure are generally not transmitted to these capillaries. If the BBB is disrupted, transcapillary water transport will be determined by the differences in hydrostatic and colloid osmotic pressure between the intra- and extracapillary compartments. Under these pathological conditions, pressure autoregulation of cerebral blood flow is likely to be impaired and intracapillary hydrostatic pressure will depend on variations in systemic blood pressure. The volume-targeted 'Lund concept' can be summarized under four headings: (1) Reduction of stress response and cerebral energy metabolism; (2) reduction of capillary hydrostatic pressure; (3) maintenance of colloid osmotic pressure and control of fluid balance; and (4) reduction of cerebral blood volume. The efficacy of the protocol has been evaluated in experimental and clinical studies regarding the physiological and biochemical (utilizing intracerebral microdialysis) effects, and the clinical experiences have been favorable.

Severe traumatic brain injury in pediatric patients: treatment and outcome using an intracranial pressure targeted therapy—the Lund concept

“…ICP higher than 20 mmHg was the threshold for intervention and escalation of treatment. CPP of 40 mmHg was allowed [9].…”

“…The Lund concept is an intracranial pressure (ICP) targeted therapy based on physiological principles for volume regulation of the intracranial compartment [9].…”

The Lund concept: is this logical?

“…Dihydroergotamine (DHE) is known to primarily constrict venous capacitance vessels within the peripheral circulation and has also been shown to decrease ICP in patients with severe head injuries (9). This effect is obtained although CBF remains unaffected or increases (4,13).…”

“…Intracranial blood volume may be reduced both on the arterial side with thiopental (15) and on the venous side with DHE (4,9,13,14). DHE is only given when other treatments are insufficient and always at the lowest dose necessary to reduce intracranial pressure.…”

“…Some aspects may however be studied in a model system utilizing a denervated cat skeletal muscle enclosed in a plethysmograph (1,9). This model simulates the pathophysiological situation in a damaged brain since muscle capillaries are permeable for water and most solutes but much less permeable for proteins (σ ≈ 0.8-0.9).…”