Advisers and investors are still scrambling to deal with the impact of the bankruptcy of Lehman Brothers (NYSE: LEH - News) , particularly in the structured credit and loan markets.

"The scale of the problem is potentially massive," said David Littlewood of Cairn Capital, which is advising investors on the impact of the Lehman default.

"Lehman provides interest and currency hedges for hundreds of millions of dollars of asset-backed securities, and losing those hedging contracts could lead to downgrades and transactions being unwound, creating losses for investors."

"No one contemplated a bank bankruptcy when structuring these transactions, and assumed that they would be able to get replacement counterparties for hedges, but in these market conditions it is very difficult," he added.

Following the bankruptcy, Standard & Poor's downgraded 422 tranches in European securitisations in which Lehman provided some form of credit and/or liquidity support, or was otherwise involved in the transaction.

Analysts have flagged concerns about the potential unwinding of tens of billions of dollars of structured vehicles such as collateralised synthetic obligations - pools of repackaged credit derivatives - although they did not think this would not be enough to cause severe market dislocation.

Lehman's bankruptcy is a potential double hit for these vehicles - either because they may struggle to reset hedges that had been put in place by Lehman, or the vehicles themselves were directly exposed to Lehman's debt.

The volume of CSOs that may have to be unwound as a result of either of these scenarios could be in the region of $20bn-$40bn, according to the analysts, who declined to be named.

Another area where the Lehman bankruptcy has caused a lot of uncertainty is where the bank acted as a lender or facility agent - a bank lender that co-ordinates a company's group of creditors and, in particular, distributes interest payments from the borrower.

A recent example is when lenders to Firth Rixson, the Oak Hill Capital Partners buy-out, had to find a replacement for Lehman that was a facility agent for the syndicated loan ahead of an interest payment from the borrower. Lloyds TSB was approached to replace Lehman.

"Even normally mundane activities that Lehman would have fulfilled could have a big impact," said a debt banker.