Nurses from across New Zealand are joining the throng of medicos volunteering to bolster frontline and support staff in hospital and GP services in the wake of Christchurch’s devastating earthquake.

As Australia begins sending rescue and medical experts, ranging from surgeons and anaesthetists to nurses, Canterbury District Health Board (CDHB) has called for more nursing staff to come forward and volunteer their services.

CDHB chief executive David Meates said already nurses and doctors across New Zealand were eager to help and he praised the entire health system for rising to "the challenges".

The Christchurch Hospital Emergency Department treated 220 trauma patients over Tuesday night and Mr Meates said the hospital is busy but is "coping well".

"The emergency department has been steady this morning and seeing fewer patients but with more serious injuries as people are freed from piles of rubble and buildings in the city," he said.

"They’ve seen many patients with lacerations, crush injuries, fractures, spinal injuries and serious wounds as a result of the quake. The cardiology and maternity units are also busy."

The New Zealand Nurses Organisation reported communications with members were still difficult but a spokesperson said the organisation had been able to ascertain that all its NZNO staff at Christchurch are safe.

All Canterbury DHB hospitals have sustained damage, leading to problems with sewerage and water supply, but all – including Burwood, Hillmorton and Princess Margaret hospitals - are operating, with bottled water and portaloos being brought in.

Around 150 beds in the Riverside Block at Christchurch Hospital were closed due to structural damage and water issues while four aged care facilities have been severely damaged, with plans being put in place to re-house residents.

Up to 40 stable patients have been transferred to other hospitals in the Christchurch region in a bid to free up the Christchurch Hospital for the more seriously ill.

Meanwhile, up to 45 home dialysis patients and their caregivers will be transferred to Auckland.

All elective surgery and outpatient appointments have been postponed for the next 48 hours with birthing units at Burwood and Lyndhurst momentarily closed. Birthing units at Rangiora, Lincoln and the Christchurch Women’s Hospital remain open.

CDHB has urged those wanting to volunteer to email their details to the National Health Coordination Centre at nhep@moh.govt.nz and put 'volunteer' in the subject line.