CHICAGO (Reuters) - Shares of Intuitive Surgical Inc (ISRG.O: Quote, Profile, Research) tumbled nearly 16 percent on Friday on disappointing earnings, analysts said.

After the market closed on Thursday, the maker of robotic systems used in surgery said first-quarter profit jumped 88 percent, while revenue surged 65 percent to $188 million.

But analysts said the financial performance was not enough to support the stock -- which has tripled in value over the past 13 months -- at those lofty levels.

"Everything is relative, and relatively speaking, the first quarter was nowhere near enough to sustain Intuitive Surgical's valuation, we believe," Oppenheimer & Co analyst Amit Hazan wrote in a research report.

"Our main concern has been that upside would be limited in 2008, and it may have begun to play out as (Wall Street estimates of sales) were exceeded by the smallest margin in two years," he said.

Though the company raised its forecast for the year, Hazan remains cautious and predicted continued pressure on the stock this year.

Michael Matson, an analyst with Wachovia, noted that the credit crunch has begun to affect hospitals' capital expenditures, which could start to hurt Intuitive Surgical's sales.

"We still believe that while Intuitive Surgical's underlying demand as a trailblazer in robotic surgery remains strong, the risks surrounding the credit issues impacting hospital spending give us pause," Matson said in a research note. "Based on this, we remain on the sidelines until we can gain better visibility into the issues facing the capital equipment purchasing market.

Lazard analyst Sean Lavin, meanwhile, advised his clients to buy shares on weakness.