This chapter deals with the investigations and resuscitation of massive bleeding into the abdominal cavity.
There are really two main sources in the abdomen where one can bleed torrentially: a ruptured abdominal aneurysm or a retroperitoneal hematoma.
Ruptured abdominal aortic aneurysm
The AAA is most common in male smokers.
The question is, when will it rupture?
- Diameter is the best predictor of rupture
- Anything over 30mm in diameter is abnormal
- Anything over 50mm has a 1% annual risk of rupture
- Anything over 60mm has a 17% annual risk of rupture
In the presence of poorly controlled hypertension, these things tend to grow in diameter by about 3-5mm per year.
When it ruptures, one tends to have about 30% pre-hospital mortality, followed by a 40% perioperative mortality. And of course, it is almost uniformly fatal in patients who are not offered surgery. Which is a fair few - give the vascular disease profile which predisposes a person to AAA formation, one can expect that a fair few of these patients will have poor cardiorespiratory performance and poor quality of life.
But let us say you go ahead with the repair.
The key controversy is the target blood pressure. The patient is shocked and the lactate is rising; one may be tempted to react to this with fluids and vasopressors. However, this may not be the best strategy. After all, the aorta has a hole in it, and the systolic blood pressure is probably directly related to the rate of exsanguination though this defect. Authors have suggested a target systolic pressure of 70-80mmHg. It seems low, but it is a fair compromise - one simply has to accept that one's patient will progress equally in the direction of both bleeding to death and global hypoxic-ischaemic injury.
Concerns with anaesthesia
The key problem is induction of anaesthesia. The conscious ruptured AAA patient is in considerable pain, and their hemodynamic performance is largely reliant on their abdominal wall musculature contracting around their sore belly, tamponading the bleed. Consider now what might happen if you relax them with anaesthetic drugs and neuromuscular junction blockers. Now, nothing is putting pressure on the defect in the aorta. This is a recipe for a PEA arrest. The next phase of management should really be the cross-clamping of the aorta, which will result in a marked improvement of hemodynamic performance, but until the clamp is in place the anaesthetist is potentially stuck performing CPR on a bunch of empty ventricles.
The patient will ultimately return to ICU intubated.
Post-operative complications of emergency AAA repair
There are several issues one wought to look out for in the returning post-AAA repair patient:
- The abdominal viscera likely lost perfusion for some time; ischaemic phenomena should be expected, including
- Ischaemic renal failure (which is unlikely to recover)
- Ischaemic pancreatitis
- Ischaemic colitis
- Ischaemia-associated upper GI bleeding
- ischaemic paraplegia: spinal vessels may be compromised
- There may be a global ischaemic insult due to the shock state
- There may be lower limb ischaemia
- The patient will be hypothermic post-operatively
- Coagulopathy associated with massive transfusion seems almost mandatory
Key points for post-operative management of emergency AAA repair
- Extubate them early. There is usually no pulmonary insult, and their COPD does not fit well with prolonged intubation.
- A thoracic epidural will help
- Watch for lower limb infarction and multi-organ system failure, as these may be convenient signals to start palliative management.
Why would you bleed into the retroperitoneal potential space?
Well, you may have had some sort of procedure performed (eg. a renal biopsy). Or, trauma (eg. axe attack).
Alternatively, you might have bled spontaneously, and this may be completely attributable to your anticoagulation therapy.
Aetiology of retroperitoneal haemorrhage
- Procedural complication
- Antiplatelet therapy
- Malignancy of the kidney or adrenal gland
- Vascular disease of the kidney
- Spontaneous rupture of retroperitoneal veins
Apart from controlling the coagulopathy and replacing the lost blood, one has several treatment options.
This may play some role in uncontrolled retroperitoneal haemorrhage. Of course, this bleeding needs to be arterial, or you will get nowhere. And you do end up embolising various useful structures (eg. kidney). However, for the unstable patient, this is probably the treatment of choice.
These days, opening the abdomen and managing the retroperitoneal hematoma directly is a fairly uncommon practice, as most things can be done by the endovascular approach. However, in some situations angiography is helpless, and in these situations open hemostasis is preferred.