I have seen the topic of vitamin K (VitK) shot coming over and over in various discussion groups, with some parents weighing the need of the VitK in newborns. One of the main argument in favor for the injection of VitK in newborn is its ability to reduce the risk of cerebral bleeding (cerebral hemorrhage).
I thought a post on this topic would provide a great help in understanding the physiological role of VitK, the consequence of brain hemorrhage and conclude on the importance of the VitK shot.
1.What is the vitamin K?
Vitamin K is a fat-soluble vitamin that is mostly obtained by our gut microbiota and accessory from our food intake (in particular leafy greens and liver).
During gestation, the fetus obtains it from the mother, as such vitamin passes through the placenta barrier. Vitamin K plays an important role through its biochemical cycle called “the Vitamin K cycle”. Vitamin K can convert glutamyl residues present in proteins into gamma-carboxylglutamyl residues as depicted in the picture below:
Such modified glutamyl residues are present in particular set of proteins called “coagulation factors”. These coagulation factors are important pieces of what we refer as the “coagulation cascade”.
I know this graph is complicated but what we care here is the final part of the cascade. The presence of intrinsic damage or trauma, we have the activation of several coagulation factors. Amongst those that are VitK-dependent, we have factor VII (seven), IX (nine) and X (ten). Prothrombin, upon activation by factor X is converted into thrombin, which in turn cleaves the soluble fibrinogen into the insoluble fibrin. Fibrin acts as a mesh and forms a fibrin clot that will patch the bleeding area. This is an important physiological response when you rupture a blood vessel. The coagulation cascade will create a clot that will stop the bleeding process, saving you from a risk of loosing too much blood and entering an hypovolemic shock. One organ is particularly sensible to brain bleed, this organ is the brain.
2. Brain hemorrhage: small numbers, big damage
In this section, I will mostly discuss about brain bleeds in regards of hemorrhagic stroke but you can apply the same pathophysiology to brain bleeds induced by brain trauma. Brain bleeds are the second type of stroke. They account for about 15% of total stroke events, but account for 40% of stroke-related deaths.
We have different types of brain bleeds. In stroke, we usually have a type of brain bleed called “intracerebral hemorrhage” (ICH) that happens deep inside the brain. There are other types of hemorrhage called “sub-arachnoid hemorrhage”. In that case, the brain bleeds occurs in the sub-arachnoid space, a space between the brain and the skull. This type of bleed results into an ischemic stroke (due to a lack of blood perfusion in blood vessels beyond the bleed site) and a brain swelling (resulting in the crushing of the brain tissue due to increase intracranial pressure).
During the injury heme (from damaged astrocytes, neurons and red blood cells) is released in the extracellular space. Heme is a very strong pro-oxidant molecule resulting in the formation of radical oxygen species (ROS) such as anion superoxide (O2*-) and hydrogen peroxide (H2O2), which in turn further induce oxidative stress and cellular damage.
The major type of cells that suffers of such damage at the greatest extent are neurons. Neurons are highly sensible to such injury and unlike other cell types neurons do not divide anymore (post-mitotic cells). A dead neuron is a dead neuron. There are some studies suggesting a possible regeneration of neurons in certain brain regions in rodents (mice, rats), yet the presence of an evidence pointing out at similar mechanism in humans are yet to be demonstrated. Furthermore, there is still no evidence that stem cells (including cord blood stem cells from umbilical cord) can provide a repair of such brain region following injury.
As of today, a dead neuron is a dead neuron. The ability of a damaged brain region to recover is very limited.
3. Why Vitamin K shots?
As we just have explained here, we know that VitK is essential in coagulation and we also understood the impact of brain bleed on the brain. Thus, reducing such brain bleed can be done in the short-term by the induction of the coagulation cascade.
As we mentioned, babies get their VitK from the placenta, but by the time they are born, they are already coming with a low VitK. We also mentioned that the VitK is primarily produced by the gut microbiota. It will take weeks if not months for babies to get a gut microbiota that is functional enough to produce the VitK (I speculate that such microbiota is not present until the age of 12 months when baby eat a diet similar to adults). We can speculate that food (breast milk or baby formula) should provide a source of VitK but providing a steady and standardized intake from dietary is near impossible to achieve.
Furthermore, there is no lab tests or techniques that can predict the onset of a brain bleed. Furthermore, brain bleed has a very high mortality rate and very high morbidity rate including cerebral palsy and other brain damage.
Therefore, ensuring a source of VitK right at birth is the best approach to ensure the baby has enough VitK to have a functional coagulation cascade. In case of a brain bleed, we can expect to have a rapid response of the body to ensure a emergency clotting process ongoing until the doctors can intervene and stop such bleeding to happen and clean any possible brain bleed.
This is why it is important to opt-in for a VitK shot. Once a brain tissue is damaged, there is no evidence yet that there is regeneration of such area. Neurons do not divide anymore by birth and there is no evidence yet of stem cells (including stem cells from cord blood) able to repair such damage.