'The most helpless I've ever felt': Sarah Michelle Gellar spends the night in ER with sick four-year-old son Rocky

Sarah Michelle Gellar admitted to feeling helpless after rushing her youngest son to hospital on Thursday night. 

The 39-year-old Buffy The Vampire Slayer star revealed on Friday that she spent the night at the ER, as she shared a picture of four-year-old Rocky James in the waiting room. 

The star - who shares Rocky with husband of 14 years Freddie Prinze Jnr - captioned that she had been worried about him after he struggled to breathe. 

She wrote: 'Well I made it 7 years before I had to take one of my children to the ER (I think that's a pretty good stretch). It was a long night and apparently a nasty virus, but thankfully Rocky was released. 

'I'm not going to lie, watching your child not be able to breathe, is the most helpless I have ever felt. Thank you to all the great doctors and nurses (and staff) who work tirelessly 24 hours a day to help. 

'And thank you to his big sister, Charlotte who would not leave his side. (The best moment was when I was filling out his paperwork, and I was asked if Rocky was single- laughter is definitely a great medicine).'

The I Know What You Did Last Summer stay kept her tot entertained with the help of an iPhone. 

She shared a picture of him tucked up in an hospital bed, captioned: 'Thank goodness for #iphones and #inspectorgadget when your little one is sick in the ER.'

Sarah and Freddie are also parents to 7-year-old Charlotte.

They met while they were filming the 1997 teen horror film I Know What You Did Last Summer, but did not begin dating until 2000.

They were engaged in April 2001 and married in Mexico on September 1, 2002. 

In 2007, in honor of their fifth year of marriage, Gellar legally changed her name to Sarah Michelle Prinze.